Tsai_2007_APSR
Defect Inspection in Low-Contrast LCD Images
136IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, VOL. 7, NO. 1, FEBRUARY 2011Defect Inspection in Low-Contrast LCD Images Using Hough Transform-Based Nonstationary Line DetectionWei-Chen Li and Du-Ming Tsai, Member, IEEEAbstract—In this paper, we propose a Hough transform-based method to identify low-contrast defects in unevenly illuminated images, and especially focus on the inspection of mura defects in liquid crystal display (LCD) panels. The proposed method works on 1-D gray-level profiles in the horizontal and vertical directions of the surface image. A point distinctly deviated from the ideal line of a profile can be identified as a defect one. A 1-D gray-level profile in the unevenly illuminated image results in a nonstationary line signal. The most commonly used technique for straight line detection in a noisy image is Hough transform (HT). The standard HT requires a sufficient number of points lie exactly on the same straight line at a given parameter resolution so that the accumulator will show a distinct peak in the parameter space. It fails to detect a line in a nonstationary signal. In the proposed HT scheme, the points that contribute to the vote do not have to lie on a line. Instead, a distance tolerance to the line sought is first given. Any point with the distance to the line falls within the tolerance will be accumulated by taking the distance as the voting weight. A fast search procedure to tighten the possible ranges of line parameters is also proposed for mura detection in LCD images. Experimental results have shown that the proposed method can effectively detect various mura defects including spot-, line-, and region-mura. It performs well for the test images containing nontextured and structurally textured patterns in the unevenly illuminated surfaces. Index Terms—Defect detection, Hough transform (HT), liquid crystal display, mura, surface inspection.Fig. 1. Low-contrast surface images in macroview and microview of LCD panels: (a1), (a2) faultless LCD surface images under macroview (lower resolution) and microview (higher-resolution), respectively; (b1), (b2) respective enhanced images of (a1), (a2); (a3), (a4) defective LCD surface images under macro and microview, respectively; (b3), (b4) respective enhanced images of (a3), (a4).I. INTRODUCTIONIN AUTOMATED surface inspection, defects in uniform or nontextured surfaces can be easily identified if the local anomalies have distinct contrasts from their regular surrounding neighborhood. However, a defect in the low-contrast image is extremely difficult to detect when the defect shows no clear edges from its surroundings and the background presents uneven illumination. In this paper, we consider the task of automated visual inspection of low-contrast defects and, especially, aim at the mura defects in liquid crystal display (LCD) panels, where the material surfaces require uneven lighting to intensify the hardly visible defects.“Mura” is one large category of defects found in LCD manufacturing. It is derived from the Japanese word for blemish. Mura is a local brightness nonuniformity that causes an unpleasant sensation to human vision [1]. According to the size and shape, the types of mura can be roughly classified as line-mura, spot-mura, and region-mura. A line-mura is a narrow straight of brightness different from its surrounding neighborhood. A spot-mura is a small circular-shaped area defect. Region-mura is one of the most difficult defects to detect in terms of the automated surface inspection algorithms since the region-mura possesses a large area of a LCD image and shows smooth changes of brightness from its uneven-lighting, low-contrast neighborhood. Fig. 1(a1) and (a2) demonstrate two surface images of a defect-free LCD panel, in which Fig. 1(a1) and (a2) are, respectively, the macroview (lower image resolution) and microview (higher image resolution) of the panel. Fig. 1(b1) and (b2) illustrate the respective enhanced images of Fig. 1(a1) and (a2) by linearly stretching the original gray levels between 0 and 255 for 8-bit displays. The enhancement equation is given byManuscript received March 21, 2009; revised August 18, 2009; accepted October 12, 2009. First published November 24, 2009; current version published February 04, 2011. Paper no. TII-09-03-0041. The authors are with the Department of Industrial Engineering and Management, Yuan-Ze University, Chung-Li 32003, Taiwan, China (e-mail: s958909@.tw; iedmtsai@.tw). Color versions of one or more of the figures in this paper are available online at . Digital Object Identifier 10.1109/TII.2009.2034844where is the gray level at image coordinates and and are respectively the minimum and maximum gray levels in the image. It can be seen from Fig. 1(a2) that the microview of LCD panel presents a textured background. It comprises horizontal gate lines and vertical data lines in the1551-3203/$26.00 © 2010 IEEELI AND TSAI: DEFECT INSPECTION IN LOW-CONTRAST LCD IMAGES USING HT-BASED NONSTATIONARY LINE DETECTION137surface, and makes the sensed image a class of structural texture. Fig. 1(a3) and (a4) present two defective LCD images that contain, respectively, a line-mura and a spot-mura on the surfaces. Fig. 1(b3) and (b4) are the corresponding enhanced defect images of Fig. 1(a3) and (a4). The enhanced images of both defect-free and defective surfaces show that the surface images are unevenly illuminated and the defects present only smooth edge transition and low intensity contrast from the surrounding background. All these surface properties in images make the automated defect inspection task extremely difficult. This section first reviews the previous work on surface defect detection. It then describes the properties of the low-contrast mura in LCD images and the core of the proposed method to tackle the defect detection problem. A. Review of Related Work The requirement of defect detection in uniform surfaces has arisen in glass plates [2], [3], sheet steel [4], aluminum strips [5], and web materials [6]. Defects in these uniform images can be effectively identified with simple statistical measures such as the mean and variance of gray levels. They can also be easily detected using simple thresholding or edge-detection techniques. The main target surfaces in the present paper involves low-contrast anomalies in an uneven lighting background, which invalidates the use of first-order statistics and thresholding and gradient methods to segment the defects. The currently available surface inspection techniques for defect detection in low-contrast images are either only applicable for specific types of small mura defects such as line-mura and spot-mura, or very computationally intensive for large regionmura. Saitoh [7] presented a machine vision scheme for the inspection of brightness unevenness in LCD panel surfaces. An edge detection algorithm was used to identify discontinuous points first. Then, a genetic algorithm was applied to extract the boundary of anomalous brightness region. Kim et al. [8] studied the detection of spot-type defects in LCD panel surfaces. An adaptive multiple-level thresholding method based on the statistical characteristics of the local block is applied to segment the macroview defect from the background surface. Oh et al. [9] studied the detection of line-type defects in TFT-LCD panels. In a low-resolution image, a directional filter bank (DFB) that finds directional information is used to identify horizontal or vertical line-shaped abnormal regions. In a high resolution image, an adaptive multilevel thresholding technique is employed to detect abnormal line defects that are brighter or darker than the surrounding pixels. Zhang and Zhang [10] presented a fuzzy expert system to detect point defects, line defects and region defects in TFT-LCD panels. The defects are measured by the features of intensity contrast, area, location, direction and shape. The choice of proper defect features and design of fuzzy rules are time consuming, and highly rely on the types and characteristics of defects in question. Lee and Yoo [11] proposed a surface fitting approach to identify low-contrast region-mura in LCD panels. For each data pixel, they first used the modified regression diagnostics to roughly estimate the background region. The background region was further approximated by a low-order polynomial to generate a background surface. The estimated background surface was then subtracted from the original image to remove the influence of nonuniform backgroundand transform the segmentation problem into a simple thresholding one. This approach showed good detection results in the experiment. However, it is rather computationally intensive for background surface estimation. By observing the horizontal or vertical scan lines of an unevenly illuminated LCD image, the gray-level profile of a scan line shows the trend of a straight line. Due to the effect of uneven illumination in the surface image, the profile will not present a well-structured line. Rather, the gray-level profile can be considered as a nonstationary signal that shows an upward, downward or flat variation in direction. In this paper, we propose a Hough transform (HT)-based one-dimensional surface inspection scheme that can detect both small- and large-sized mura defects of varying shapes in LCD panel surfaces. Finding a line segment in a noisy nonstationary signal is a nontrivial problem. The most commonly used technique for straight line detection in a noisy image is the HT [12]. The HT for line detection in an image is based on a voting procedure which accumulates the number of points that lie on the same line of specific parameter values. For straight-line detection, the best straight line is estimated by the maximum counts of accumulator which corresponds to a pair of specific line parameters. The merit of HT that converts the difficult shape detection in the Cartesian space into simple peak detection in the parameter space will not be beneficial for nonstationary signals. The points deviated from a specific line, even with a minor distance to the line, will not be accumulated and the resulting peak is low and scattering. In this study, the standard HT is not suitable to detect the linear trend of nonstationary gray-level profiles in low-contrast images. The standard HT has been popularly applied to straight line detection since Duda and Hart [13] proposed the parameterspace transform method. It converts the Cartesian coordinate to parameter space for a line equation system with in the range of and . The transform creates the corresponding line equations, which intersect in . The accumulators count the number the parameter space of intersection points and find a peak to decide a pair of specific parameter with respect to the line equation. The HT is a very costly algorithm in terms of computation time. The space complexity of the standard algorithm is determined by the number of accumulators in the parameter space, and the time complexity is determined by the total number of increments of parameter values. A number of speed-up algorithms for straight-line detection were developed to overcome the high computation load of the standard HT. Bergen and Shvaytser [14] described an efficient probabilistic algorithm with Monte Carlo approximation to the HT. The complexity of the proposed algorithm is independent of the input size. The proposed probabilistic steps involve randomly choosing small subsets of points, and have shown that the complexity can be further reduced by sampling small subsets of points that jointly vote for likely patterns. Rau and Chen [15] used the principal axis analysis method to accelerate the extraction of straight lines and increase the accuracy of the detected lines. Duquenoy and TalebAhmed [16] proposed two HT acceleration techniques, spatial under-sampling and anticipated maxima detection. The undersampling technique was presented to find the best criterion derived from the observed stability of the peak position in the138IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, VOL. 7, NO. 1, FEBRUARY 2011parameter space to stop the transform calculation. The anticipated maxima detection adaptively detects the maximum peak of accumulation in the parameter space to improve the estimated accuracy of peak detection. Furthermore, many a modified HT methods were also proposed to improve the accuracy of line parameter estimation based on the coarse-to-fine technique [17]–[20]. Niblack and Petkovic [21] alternatively used filtering techniques in the Hough space to improve the estimation accuracy of line parameter values. Costa and Sandler [22] presented a normalized parameter space to reduce the effect of noise points so that the accuracy of peak detection can be improved. B. Surface Properties of LCD Images and Overview of the Method In physics, the energy from a light source that reaches a given part of a surface falls off as the inverse square of the distance that the light travels from the source to the surface [23]. Given the distance from the light source to one end of the image plane and the adding distance to the opposite end of the image plane. Generally, the light source distance is significantly larger than ). If the the width of the sensed surface (roughly equal to can be distance is normalized as one unit, then if the term is approximately given by close to zero. Therefore, the intensity is linearly decreased from one end to the opposite end in the image plane if the light source distance is distinctly larger than the sensed surface width. By scanning the sensed 2-D surface image horizontally or vertically, the 1-D gray-level profiles crossing over faultless and defective surface regions will all have a global representation of straight line. Given a nonstationary gray-level profile with the trend of a straight line, the defect points on the gray-level profile can be detected by calculating the distance of each point to the best fitting line of the profile. If the distance of a point on the profile is distinctly far away from the fitting line, the point can then be declared as a defect one. The currently available HT methods focused on either improving accuracy of parameter values or accelerating computation time. The standard HT may perform poorly for nonstationary gray-level profiles in a low-contrast, unevenly illuminated image. Fig. 2(a) demonstrates a textured LCD image, in which the dark mura defect is in the central bottom area. Fig. 2(b) shows the gray-level profiles of two horizontal scan lines across defect-free (scan line 1) and mura (scan line 2) regions. Fig. 2(c) shows the detection results of the standard HT for the defective gray-level profile (scan line 2), in which the detected straight-line with the largest accumulation peak is depicted in the figure. Fig. 2(d) presents an ideal straight line which makes the mura defect segment far away from the fitting line. The demonstration sample reveals that the standard voting procedure of the HT is invalidated to find the line segment in a nonstationary gray-level profile. In this study, a revised version of the HT is proposed for line detection in nonstationary gray-level profiles. The standard HT requires a sufficient number of points lie exactly on the same straight line at a given parameter resolution so that the accumulator will show a distinct peak in the parameter space to indicate the presence of a straight line. It fails to detect a line that has numerous points distributed around the vicinity of the lineFig. 2. Two-dimensional and one-dimensional LCD images: (a) original LCD image containing a mura defect in the central bottom area; (b) gray-level profiles crossing over defect-free and mura regions; (c) straight line detected by the HT for the scan line 2 in (b); and (d) expected straight line for the scan line 2 in (b).in a nonstationary signal. In the proposed HT-based scheme, the distance tolerance of a point to the line sought is first given. Any point with the distance to the line falls within the tolerance will be accumulated as a function of the distance to the line sought. This approach allows the nonstationary points contribute to the accumulator in the voting processing. The proposed HT with adaptive voting weight under a given distance tolerance can well detect the most possible line equation in a nonstationary gray-level profile. Any points on the gray-level profile that are distinctly far away from the fitting line can then be identified as defective ones. A fast search procedure that can tighten the possible ranges of the line parameters is also proposed by finding the global dominant line segment of all gray-level profiles in each scan direction. By recursively applying the proposed HT method to all individual row and column gray-level profiles, the actual region of a mura defect can be presented in the 2-D inspection image. II. NONSTATIONARY LINE SEARCH This section presents the proposed HT scheme for line detection in nonstationary gray-level profiles. The standard HT is first introduced in Section II-A. The proposed HT-based scheme is then described in Sections II-B and II-C. A. Overview of Hough Transform (HT) In the standard HT algorithm for straight-line detection, the equation used to describe a line in two-dimensional (2-D) space is given by the parameters and in the normal form (1) where is the perpendicular distance of the line to the origin, and is the angle between the normal to the line and the posi-LI AND TSAI: DEFECT INSPECTION IN LOW-CONTRAST LCD IMAGES USING HT-BASED NONSTATIONARY LINE DETECTION139tive axis. To apply the HT with this form, each point is parameter mapped to all possible parameter values in the despace. A two-dimensional (2-D) voting accumulator notes the number of points falling on the line with parameter values and . The largest peak of the accumulator determines and , i.e., the specific pair ofwhere and denote the most possible parameter values of the straight line sought in the Cartesian space. The standard HT algorithm can well detect a strict line segment in a complicated, noisy image. For a given parameter values and , it basically accumulates for only those points line with a given parameter that lie exactly on the resolution. The points in a nonstationary profile will be treated as the noisy ones, even they are in a distant neighborhood of line. The detection of local peaks in the vicinity the of maximum accumulator value, or an iterative coarse-to-fine search [17]–[20], cannot take into account those points. Therefore, the standard HT may perform poorly for a nonstationary gray-level profile, where only a small segment shows the trend of a straight line. B. Proposed HT Scheme In the proposed HT scheme, the points that contribute to the vote do not have to lie exactly on a line. Instead, the distance tolerance of a point to the line sought is first given. Any point with the distance to the line falls within the tolerance will be accumulated as a function of the distance. Conversely, any point with the distance beyond the tolerance is discarded in the voting process. Highly nonstationary gray-level profiles require a larger distance tolerance , while more stable gray-level profiles use a smaller distance tolerance for detecting the line equation. be of size . For Let the inspection image , the a given horizontal scan line Y, , row gray-level profile is denoted by . The coordinates of a point on the gray-level is then given by , for profile Y of length . To simplify the notation, the gray-level is represented by , i.e., the point on a gray-level profile is denoted by . To calculate the distance between a point and a straight line, we can rewrite (1) from the normal . That is form to the slop-intercept form (2) is the slop , and where . Therefore, the distance from a point profile to the line with parameter values is the intercept in the gray-level is calculated by (3) The distance of a point is used to derive the voting weight in the accumulator, which is given by (4)where is the exponent and is used to adjust the significance of a small change in distance . It is set at 3 in this study. Note is in the range between 0 and 1. A that the weight line has a maximum weight of point lying exactly on the 1, whereas the weight is dramatically reduced to 0 as the point is far away from the line. In order to accommodate the nonstationary nature of the graywith distance less level profile, a point than a predetermined distance tolerance is considered as a point on the line with the voting weight defined in (4). HenceThe accumulator then adds the voting weight as (5) At the end of the voting process, the final line equation of the gray-level profile is, therefore, given by the maximum value of , i.e.,To demonstrate the effectiveness of the proposed HT and the effect of changes in tolerance , four synthetic 1-D linear signals , , 2, 3, 4, with varying degrees of random noise are are given by created to verify the performance. The signals the following linear equation, which arewhere is a Gaussian noise with zero mean and standard , , , and . is a straight deviation to are the same straight lines line containing no noise, and and direction with added Gaussian noise. The distance of the ideal straight line are . Fig. 3(a)–(d) show the results of line detection for signals , , and from the proposed method. The distance tolerance is given by 2, 5, and 10 to test the fitting results. Table I lists all the estimated and values with varying values. It can be observed that the proposed method can well detect nonfor line stationary lines even under the severe noise signal . The detected parameter values are very close to the true parameter values (159, 84). The peaks of the accumulator are directly proportional to the value of and the detection results are not sensitive to the changes in value. A synthetic gray-level profile is also generated to demonstrate the effectiveness of the proposed HT that uses the distance as the adaptive weight to find a straight line within a given distance tolerance. Fig. 4(a) shows the line detection result from the standard HT for the synthetic nonstationary profile. The result indicates the linear trend of the profile cannot be precisely detected. In contrast, Fig. 4(b) shows the line detection result from the proposed method. It well performs the detection of linear trend, regardless of the variation along the line. In defect detection, the proposed HT scheme is used to identify best fitting lines of the oscillated, nonstationary gray-level profiles in a low-contrast image. During the scanning procedure140IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, VOL. 7, NO. 1, FEBRUARY 2011Fig. 3. Four nonstationary line signals and their detected lines from the proposed method: (a) a synthetic line signal L without noise; (b)–(d) three synthetic line signals L L with different Gaussian noises of , , respectively. (a) L ; (b) L and ; (c) L ; and . (d) L ( = 10)=6=8= 10( = 0)( = 6)( = 8)TABLE I FITTING RESULTS OF THE PROPOSED METHOD FOR THE LINE SIGNALS IN Fig. 3The expected distance and direction of the line signal: = 159, = 84.Fig. 4. (a) Detected straight line from the standard HT for a nonstationary profile. (b) Detected straight line from the proposed HT method. (a) ; ; . ; . (b) ; (68 83)() = (63 88)()=of an inspection image, each column (vertical) and row (horizontal) gray-level profiles are individually evaluated. Any point deviated distinctly from the fitting line is marked as a defect one. , we have to estimate gray-level For an image of size profiles of horizontal rows and gray-level profiles of vertical columns in the image. The voting procedure of the proposed HT scheme for the points on the gray-level profile is based on thedistance tolerance , i.e., the points need not lie exactly on the line sought. The standard HT needs only to evaluate all possible values of in a small finite range, and then can be calculated by using (1). For the proposed HT method, the line (1) cannot be and used to calculate the value for given coordinates values. Therefore, the proposed HT method must evaluate all possible combinations of both and . This should result in a huge computational burden if all possible combinations of must be evaluated for every point on the gray-level profile. In order to make the proposed HT applicable to defect detection in a manufacturing process, we present a fast selection process that finds the most possible ranges of and in the line equation. For a given inspection image, all row gray-level profiles in the image should have the similar trend of a straight-line shape with or without defects on the surface. It is also true for all column gray-level profiles in the image. The core idea for the constraints of and values is to evaluate the ranges from a profile map. The profile map is constructed by overlapping all row gray-level plane (or the profiles (or column profiles) in the plane). The most possible ranges of and will be extracted from this profile map. The detailed process for searching the ranges of line parameters and in the profile map is discussed in the following section. C. Constraints on the Line Parameters andThe gray-level profiles of the same scan direction in a lowcontrast image have approximately the same trend of a line slop. We can therefore plot all gray-level profiles of the same scan direction on a map which has the gray-level (from 0 to 255 forLI AND TSAI: DEFECT INSPECTION IN LOW-CONTRAST LCD IMAGES USING HT-BASED NONSTATIONARY LINE DETECTION141Fig. 5. Construction procedure for the row and column profile maps. Fig. 6. High-pass Haar wavelet decomposition: (a) horizontal profile map ^ (x) of (a); and (c) wavelet detail signal R(x; f (x)); (b) upper contour R ^ (x) of (b). The dash-line in (c) represents the control limit 2 d .an 8-bit display) in the vertical axis and the profile point number in the row and in the column) in ( the horizontal axis. Each row (or column) scan image will be (or ) plane to form a profile map. overlapped in the Fig. 5 illustrates an image of size . It therefore involves row profiles and column profiles. The row profile plane is given by map in theLikewise, the column profile map in the structed asplane is recon-row gray profiles has similar trend of a line slop, the upper contour and lower contour in the filtered profile map are basically identical in shape. In a given inspection image, the defect-free region is generally distinctly larger than the defective region. Therefore, the defect-free line segwill be longer than any of the ment in the upper contour defective segments. We need only to identify the defect-free line and the possible range can be easily desegment from termined from such a segment. In this study, we use the fast Haar wavelet decomposition to of detect the longest line segment in the upper contour the filtered profile map. The range search procedure is proin the filtered proceeded as follows. The upper contour file map is given byRange of : In the profile map, a point of gray-level profiles is marked by 0 (black intensity), and the remaining empty space is marked by 1 (white intensity). Once the maps of row and column gray-level profiles are separately constructed, we can easily find the ranges of and from the maps. The transform representation in the map shows a principal direction of the gray-level profiles. Thus, we can easily restrict the search range of within a once the principal direction in the profile map small interval is determined. In the proposed search scheme of parameter ranges, the ranges of will be separately estimated from the row and , column profile maps. For the row profile map the morphological closing operation is first implemented to eliminate the noisy points first, i.e.,The upper contour is then decomposed into its detailed part using the Haar wavelet frame. Thuswhere and denote, respectively, the dilation and erosion 3 structuring element. The binary operation, and B is a 3 closing operation smoothes the contour and removes isolated (extreme) points in the profile map. Since the majority of thewhere are the high-pass coefficients of the Haar basis [24], and are given by and . is the decomposed detail version of , which entails only the fine detail of the upper contour. Note that has the because same full length of the original upper contour the filtered 1-D signal is not subsampled. Fig. 6(a) illustrates the filtered horizontal profile map of an image, and Fig. 6(b) presents its upper contour. Fig. 6(c) shows the detailed version in the wavelet decomposition. In order to extract the of dominant line segment that shows significantly linear trend in , a simple statistical process control limit is used to set up the threshold. This threshold can effectively detect the transition。
AnaChip AP2007 数据手册
AP2007Synchronous PWM ControllerFeatures- Single 4.5V to 20V Supply Application - 0.8V + 2.0% Voltage Reference - Virtual Frequency Control TM - Fast Transient Response- Synchronous Operation for High Efficiency (93%) - Short Circuit Protect- Small Size with Minimum External Components - Soft Start and Enable Functions - Under Voltage Lockout Function - SOP-8L Pb-Free PackageApplications- Microprocessor Core Supply- Low Cost Synchronous Applications - Voltage Regulator Modules (VRM) - Networking Power Supplies - Sequenced Power Supplies- Telecommunication Power Supplies.General DescriptionThe AP2007 is a low-cost, full featured, synchronous voltage-mode controller designed for use in single ended power supply applications where efficiency is of primary concern. Synchronous operation allows for the elimination of heat sinks in many applications. The AP2007 is ideal for implementing DC/DC converters needed to power advanced microprocessors in low cost systems or in distributed power applications where efficiency is important. High-side drive circuitry, and preset shoot-thru control, allows the use of inexpensive 1P+1N-channel power switches.AP2007’s features include temperature compensated voltage reference, Virtual Frequency Control TM method to reduce external component count, an internal 200KHz virtual frequency oscillator, under-voltage lockout protection, soft-start, shutdown function and current sense comparator circuitry.Virtual Frequency Control is a trademark of PWRTEK, LLC.Pin AssignmentsSOP-8L1(Top View)VCC V REFPHASE DRVP DRVNFBGND AP20072345678SS/SHDNOrdering InformationAP2007 X X Package Packing S: SOP-8LBlank : Tube A : TapingPin DescriptionsNameDescriptionVCC Chip supply voltage V REF Reference voltagePHASEInput from the phase node betweenthe MOSFET sDRVP High side driver output (P MOSFET)GND Ground DRVN Low side driver output (N MOSFET) FB Feedback inputSS/SHDN Soft start, a capacitor to ground setsthe slow start time / Shutdownfunction查询AP2007供应商Synchronous PWM ControllerBlock DiagramCROSS CURRENT CONTROL DRVNVIRTUAL FREQ OSCILLATORDRVPR Q SQSQB R+-+-+-+-VOLTAGE REFERENCE +-VCC0.8VUNDER VOLTAGEERROR COMPVCC 12ua2ua0.2V0.9VSS/SHDNFBGNDOCSETPHASEVCCDRVPDRVNAP2007 FUNCTIONAL BLOCK DIAGRAMVirtual Frequency Control - PatentNumber 6,456,050.V REF-+0.4V -+0.4VAbsolute Maximum RatingsSymbol ParameterRange. Unit V IN VCC to GND -1 to 22 V V PHASE PHASE to GND -1 to 22 V V DRVP DRVP to GND -1 to 22 V V DRVN DRVN to GND-1 to 22 V θJC Thermal Resistance Junction to Case 90 oC/W θJA Thermal Resistance Junction to Ambient 250 oC/W T OP Operating Temperature Range -40 to +85 o C T ST Storage Temperature Range-65 to +150o C T LEADLead Temperature (Soldering) 10 Sec.300o CSynchronous PWM ControllerElectrical CharacteristicsUnless specified: V CC =12V; GND = 0V;V O = 5V; T J = 25oCSymbol Parameter Conditions Min. Typ. Max. Unit Power SupplyV CC Supply Voltage(Recommended)4.5 - 20 VI CC Supply Current DRVP & DRVN are floating - 9.5 - mA ∆V LINE Line Regulation V O = 2.5V - 0.5 % Error Comparator A OL Gain (A OL ) - 70 - dB I B Input Bias - 0.2 1 uA Oscillator F OSC Oscillator Frequency - 200 - KHz DC MAX Oscillator Max Duty Cycle 80 85 - % Mofset DriversI DRVP DRVP Source/Sink V CC – V DRVP =3VV DRVP – V GND = 2V 0.5 1 - AI DRVN DRVN Source/Sink V CC – V DRVN = 3VV DRVL – V GND = 2V0.5 1 - AV DRVL DRVP/N Low Level Voltage - - 1.2 V V DRVH DRVP/N High Level Voltage V CC -1.2- - V ProtectionT DEAD Dead Time DRVP & DRVN are floating - 150 - nS Vocset Over Current Setting Voltage 0.4 VV DRVP/N DRVP/DRVN System ErrorVoltage (Note3) V SS =Low, V CC <3.8, over current happenV CC -1.2- - VReferenceReference Voltage 0.7840.8 0.816V V REF Accuracy 0o C to 70oC-2 - + 2 %Soft StartI SSC Charge Current V SS = 1.5V 8.0 10 12 uA I SSD Discharge Current V SS = 1.5V 1.3 2 2.7 uA Under voltage lockout (UVLO)V UT Upper Threshold Voltage (V CC )- 4.0 - V V LWT Lower Threshold Voltage (V CC )- 3.8 - V V HT Hysteresis (V CC ) - 200 - mVNote 1. Specification refers to Typical Application Circuit.Note 2. This device is ESD sensitive. Use of standard ESD handling precautions is required. Note 3. Abnormal condition; Ex: over-current, under-voltage lockout, soft-start disappear.Synchronous PWM ControllerTypical Application Circuit87651234D1Option VCC SS/SHDN FB DRVP GNDPHASE DRVN Q1Q2L110uHC8470u/16V C9Vout=3.2V*+-+-C1R21KR33K ** Vout = 0.8 x (1+R3/R2)AP2007C4330nC3330nR112ΩV REF 10n470u/16V470u/16VAF9435C5AF9410C20.1uC647n C70.1u 1ΩOption 1ΩOptionR2 1K ~ 10K≅(4835)(4412)Virtual Frequency ControlVirtual Frequency Control combines the advantages of constant frequency and constant off-time control in a single mode of operation. This allows fix frequency, precision switching voltage regulator control with fast transient response and the smallest solution size. Switch duty cycle can be adjusted from 0% to 100% on a pulse by pulse basis when responding to transient conditions. Both 0% and 100% duty cycle operation can be maintained for extended periods of time in response to load or line transients. Figure 1 depicts a simplified operation of the Virtual Frequency Controltechnique: The VFC oscillator generates a pulse of a known duration (VFC_Pulse). The regulator loop responds by returning a complementary feedback pulse (FB_Pulse). The FB_Pulse duration is a result of external conditions such as inductor size, the voltage across the inductor and the duration of the VFC_Pulse. A VFC control loop is then formed whereby the duration of the VFC_Pulse is modified as a result of the FB_Pulse duration. The VFC loop arrives at a state of equilibrium, where the operating frequency remains inherently constant.GATE CONTROL LOGICVIRTUAL FREQ OSCILLATOR+-FB PulseVFC PulseVrefERROR COMPV INLout CoutVout Rfb1Rfb2Figure 1: Virtual Frequency Control Loop- Synchronous single supply application.Synchronous PWM with VFC Controller (Preliminary) Virtual Frequency Control (Continued)Virtual frequency control is a technique that provides stable, constant frequency of operation for pulse controlled architectures such as constant off-time/on-time. This is all done internal to the IC with minimal number of components and without the need for connections to external terminals such as input and/or output. No external compensation is required, thus providing a low cost, high performance fix frequency solution for switching voltage regulators.Virtual Frequency Control is a trademark of PWRTEK, LLC.Function DescriptionSynchronous Buck ConverterPrimary V CORE power is provided by a synchronous, voltage-mode pulse width modulated (PWM) controller. This section has all the features required to build a high efficiency synchronous buck converter, including soft-start, shutdown, and cycle-by-cycle current limit.Referring to the functional block diagram FIG 1, the output voltage of the synchronous converter is set and controlled by the output of the error comparator. The external resistive divider reference voltage, is derived from an internal trimmed-bandgap voltage reference. The inverting input of the error comparator receives its voltage from the FB pin.The internal oscillator uses an on-chip capacitor and trimmed precision current sources to set the virtual oscillation frequency to 200KHz. The virtual frequency oscillator sets the PWM latch. This pulls DRVN low, turning off the low-side N_MOSFET and DRVP is pulled low, turning on the high-side P-MOSFET (once the cross-current control allows it). The triangular voltage ramp at the FB pin is then compared against the reference voltage at the inverting input of the error comparator. When the FB voltage increases above the reference voltage, the comparator output goes high. This pulls DRVP high, turning off the high-side P-MOSFET, and DRVN is pulled high, turning on the low-side N-MOSFET (once the cross-current control allows it). The Virtual Frequency Oscillator then generates a programmed off time to allow the FB voltage to return to the valley voltage of the triangular ramp. At the end of the off time the PWM latch is set and the cycle repeats again.Under Voltage LockoutThe under voltage lockout circuit of the AP2007 assures that the high-side P-MOSFET driver outputs remain in the off state whenever the supply voltage drops below set parameters. Lockout occurs if V CC falls below 3.8V. Normal operation resumes once V CC rises above 4.0V. R DS(ON) Current LimitingThe current limit threshold (0.4V) is set by connecting an internal resistor from the V CC supply to OCSET. Vocset is compared to the voltage at the PHASE node. This comparison is made only when the high-side drive is high to avoid false current limit triggering due to uncontributing measurements from the MOSFET s off-voltage. When the voltage at PHASE is less than the voltage at OCSET, an over-current condition occurs and the soft start cycle is initiated. The synchronous switchturns on and SS/SHDN starts to sink 2uA. When SS/ SHDN reaches 0.2V, it then starts to source 10uA and a new cycle begins. When the soft start voltage is below 0.9V the cycle is controlled with pulse by pulse current limiting.Soft StartInitially, SS/SHDN pin sources 10uA of current to charge an external capacitor. The inverting input of the error comparator is clamped to a voltage proportional to the voltage on SS/SHDN. This limits the on-time of the high-side P-MOSFET, thus leading to a controlled ramp-up of the output voltages.Synchronous PWM with VFC Controller (Preliminary)Function Description (Continued)Hiccup ModeDuring power up, the SS/SHDN pin is internally pulled low until V CC reaches the under-voltage lockout level of 4V. Once V CC has reached 4V, the SS/SHDN pin is released and begins to source 10uA of current to the external soft-start capacitor. As the soft-start voltage rises, the inverting input of the error comparator is clamped to this voltage. When the error signal reaches the level of the internal 0.8V reference, the output voltage is to have reached its programmed voltage. If an over-current condition has not occurred the soft-start voltage will continue to rise and level off at about 2.5V.An over-current condition occurs when the high-side drive is turned on, but the PHASE node does not reach the voltage level set at the OCSET pin. Once an over-current occurs, the high-side drive is turned off and the low-side drive turns on and the SS/SHDN pin begins to sink 2uA. The soft-start voltage will begin to decrease as the 2uA of current discharge the external capacitor. When the soft-start voltage reaches 0.2V, the SS/SHDN pin will begin to source 10uA and begin to charge the external capacitor causing the soft-start voltage to rise again. If the over-current condition is no longer present, normal operation will continue. If the over-current condition is still present, the SS/SHDN pin will again begin to sink 2uA. This cycle will continue indefinitely until the over-current condition is removed.In order to prevent substrate glitching, a small-signal diode should be placed in close proximity to the chip with cathode connected to PHASE and anode connected to GND.Marking Information(Top View)SOP-8L184AP2007YY WW XLogo"02" =2002~5Synchronous PWM ControllerPackage InformationPackage Type: SOP-8LVIEW "A"LHECVIEW "A"AA 2A 1B e D7(4X)0.015x457(4X)yDimensions In Millimeters Dimensions In Inches SymbolMin. Nom. Max. Min. Nom. Max.A 1.40 1.60 1.75 0.055 0.063 0.069 A1 0.10 - 0.25 0.040 - 0.100 A2 1.30 1.45 1.50 0.051 0.057 0.059B 0.33 0.41 0.51 0.013 0.016 0.020C 0.19 0.20 0.25 0.0075 0.008 0.010D 4.80 5.05 5.30 0.189 0.199 0.209E 3.70 3.90 4.10 0.146 0.154 0.161 e - 1.27 - - 0.050 - H 5.79 5.99 6.20 0.228 0.236 0.244 L 0.38 0.71 1.27 0.015 0.028 0.050 y - - 0.10 - - 0.004θ0O - 8O 0O- 8O。
Large area single-mode parity–time-symmetric
OPTICS LETTERS / Vol. 37, No. 5 / March 1, 2012
Large area single-mode parity–time-symmetric laser amplifiers
Mohammad-Ali Miri,* Patrik LiKamWa, and Demetrios N. Christodoulides
CREOL, College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816–2700, USA *Corresponding author: miri@ Received October 26, 2011; revised January 9, 2012; accepted January 15, 2012; posted January 17, 2012 (Doc. ID 157003); published February 17, 2012
By exploiting recent developments associated with parity–time (PT) symmetry in optics, we here propose a new avenue in realizing single-mode large area laser amplifiers. This can be accomplisБайду номын сангаасed by utilizing the abrupt symmetry breaking transition that allows the fundamental mode to experience gain while keeping all the higher order modes neutral. Such PT-symmetric structures can be realized by judiciously coupling two multimode waveguides, one exhibiting gain while the other exhibits an equal amount of loss. Pertinent examples are provided for both semiconductor and fiber laser amplifiers. © 2012 Optical Society of America OCIS codes: 140.3570, 140.4480, 130.2790.
image alignment and stitching a tutorial
Richard Szeliski Last updated, December 10, 2006 Technical Report MSR-TR-2004-92
This tutorial reviews image alignment and image stitching algorithms. Image alignment algorithms can discover the correspondence relationships among images with varying degrees of overlap. They are ideally suited for applications such as video stabilization, summarization, and the creation of panoramic mosaics. Image stitching algorithms take the alignment estimates produced by such registration algorithms and blend the images in a seamless manner, taking care to deal with potential problems such as blurring or ghosting caused by parallax and scene movement as well as varying image exposures. This tutorial reviews the basic motion models underlying alignment and stitching algorithms, describes effective direct (pixel-based) and feature-based alignment algorithms, and describes blending algorithms used to produce seamless mosaics. It closes with a discussion of open research problems in the area.
Chan and Reich 2007 IT Alignment - What we have learned
State of the ArtIT alignment:what have we learned? Yolande E Chan1,Blaize Horner Reich21The Monieson Centre,Queen’s School of Business,Queen’s University,Kingston,Canada2Segal Graduate School of Business,Faculty of Business Administration,Simon Fraser University,Vancouver,CanadaCorrespondence:YE Chan,Queen’s School of Business,Queen’s University,Kingston,ON,Canada K7L3N6.Tel:þ16135332364;Fax:þ16135332321;E-mail:ychan@business.queensu.caAbstractWe provide a review of the alignment literature in IT,addressing questions such as:Whathave we learned?What is disputed?Who are contributors to the debate?The article isintended to be useful to faculty and graduate students considering conducting researchon alignment,instructors preparing lectures,and practitioners seeking to assess the‘state-of-play’.It is both informational and provocative.Challenges to the value ofalignment research,divergent views,and new perspectives on alignment are presented.Itis hoped that the article will spark helpful conversation on the merits of continued investigation of IT alignment.Journal of Information Technology(2007)22,297–315.doi:10.1057/palgrave.jit.2000109Published online18September2007Keywords:alignment;linkage;fit;models;measures;antecedents;outcomes;strategy;structure;culture;knowledge;social dimensionsIntroductionF or two decades,IT alignment has consistently appearedas a top concern for IT practitioners and company executives(Luftman et al.,2005).Hundreds of commentaries and cases have been published in trade publications.Many scholarly journal articles have been published.So what have we learned?In this article,we focus on the alignment literature within the MIS research discipline,reviewing past articles–primarily of a scholarly nature–and proposing integrating views.Researchers,teachers,and practitioners alike should find this integration of the literature beneficial. For research,we suggest where future contributions might be made.For lecturers,we present alignment models that can be used in IT strategy classes to explain key concepts.In addition,we present the‘state-of-play’in alignment practice for lecturers and practitioners.For the latter,we also suggest ways to interpret the literature and implement research recommendations.We have tried to be both informational and provocative.Challenges to the value of alignment research,divergent views and new perspectives on alignment are presented.Our goal is to be as inclusive of major alignment perspectives as possible.1We invite scholars and practitioners to contact the authors to provide additional information,similar and contrary views,and case studies.Via the Journal of Information Technology and AISWorld(http://www.isworld. org),we will summarize the feedback and stories we receive.Welcome to a conversation on IT alignment.Structure of ArticleIn the article,we first discuss the motivation for alignment research.Next,we move on to define alignment and to present key dimensions and levels of the alignment construct.Our goal is to be inclusive of many different perspectives.We then present a review of various factor models of alignment and discuss antecedents and out-comes.We address the questions:What creates alignment? What benefits can reasonably be expected?Next,we present a process perspective on alignment and comment on different process models that have been researched.In closing,we provide reflections on the IT alignment research stream to date and highlight key implications for research and practice.Motivation and need for alignment researchFor many years,researchers have drawn attention to the importance of alignment between business and IT2(e.g., McLean and Soden,1977;Henderson and Sifonis,1988).In early studies,this often meant linking the business plan and the IT plan.Another perspective involved ensuring congruence between the business strategy and the IT strategy.Still another has required examining the fit between business needs and information system priorities. These conceptualizations have been enlarged over time and now research recognizes many points of alignment between business andIT.Journal of Information Technology(2007)22,297–315&2007JIT Palgrave Macmillan Ltd.All rights reserved0268-3962/07$30.00 /jitEarly motivation for alignment emerged from a focus on strategic business planning and long-range IT planning in the early1980s(e.g.,IBM,1981).From a business perspective,planning was characterized as a top-down and a bottom-up process,and departmental(e.g.,IT)plans were created in support of corporate strategies.From an IT perspective,decisions on hardware and software had such long-term implications that tying them to current and future plans of the organizational unit was a practical necessity.The business and IT performance implications of alignment have been demonstrated empirically and through case studies during the last decade(e.g.Chan et al.,1997;de Leede et al.,2002;Irani,2002;Kearns and Lederer,2003). Simply put,the findings support the hypothesis that those organizations that successfully align their business strategy with their IT strategy will outperform those that do not.Alignment leads to more focused and strategic use of IT which,in turn,leads to increased performance(Chan et al.,2006).For all these reasons,academics have been motivated to study IT alignment.However,the motivation for and methods of alignment research have also been challenged.A counter-argumentMany scholars argue that the alignment literature fails to capture important phenomena and that in fact,alignment is not always desirable.The arguments have several themes, including(1)alignment research is mechanistic and fails to capturereal life,(2)alignment is not possible if the business strategy isunknown or in process,(3)alignment is not desirable as an end in itself since thebusiness must always change,and(4)IT should often challenge the business,not follow it. These arguments that challenge the need for further alignment research are described more fully below. Ciborra(1997)3suggests that the alignment literature is too theoretical;that it is generated by the scientific method applied to the design of human affairs and computer systems.He recommends a Mintzberg-like approach,where researchers go to the field for insights(Mintzberg,1973). Critics of IT alignment research argue that in the world of work,alignment does not succeed because strategy is not a clear concept due to various turbulent,unpredictable circumstances that leave managers muddling through, betting,and tinkering with their corporate strategies(Vitale et al.,1986).Tightly coupled arrangements can have negative outcomes especially in turbulent times.That is,if the business environment suddenly changes and alignment is too tight,businesses may have difficulty adjusting to their new environments.Furthermore,the use of technology itself is characterized by improvisations of various sorts(Ciborra,1996; Orlikowski,1996)and by unexpected outcomes.Working toward pre-specified or fixed outcomes may be unrealistic. In the worst case,this is an argument for the demise of alignment research.At best,this calls for an enlarged notion of alignment within a hybrid network of semiauto-nomous(vs harmonized and synchronized)actions (Ciborra,1997).Depending on the model of alignment,one can argue that it is necessary for IT to challenge the business,not simply implement its vision(Chan and Huff,1993).Disagreement, friction,and conflict can be more desirable than reactive, smooth IT operations in order to achieve high business performance.This view suggests that researchers who believe that IT should simply support what the business is doing may be wasting their and others’time.However, Kearns and Lederer(2000)point out that while effective alignment of the IT plan with the business plan can provide competitive advantage,the opposite–aligning the business plan with the IT strategy–can result in potential losses.For this reason,researchers and practitioners must be cautious about putting IT in the lead.Levy(2000),using a resource-based perspective,cautions that IT–even aligned IT–in and of itself is not strategic.In order for IT to be strategic,it must be valuable,unique,and difficult for competitors to imitate.Sauer and Burn(1997)warn that alignment can give rise to pathologies that require careful management if undesired business and IT costs are to be avoided.Three types of pathological outcomes from strategic alignment are identi-fied:misalignment,which occurs when a company tries to align IT with business strategies that are not internally consistent;IT stagnation,which occurs as part of a common,almost natural,cycle of innovation;and IT and globalization,which presents special scale and cultural difficulties for alignment.If IT researchers produce manu-scripts that call for high alignment in these potentially difficult and pathological situations,they are doing a disservice to practitioners.So should we abandon the study of alignment?The authors think not but welcome reader input.Although there are theoretical and empirically based arguments suggesting that alignment may not always be a suitable goal,the practitioner community consistently ranks it as a top priority.The Society for Information Management conducts surveys to gauge the importance of various IT issues.In2005,the number one management concern of all groups of respondents was alignment(Luftman et al.,2005).Alignment was also ranked as the top management concern in2004and2003,whereas it was ranked9th in1994,7th in1990,5th in1986,and7th in 1983.It is clear that the issue of IT alignment has remained important over the past two decades.From the authors’perspective,the issues noted above are challenges to the attainment of alignment,rather than reasons alignment should not be pursued or studied.In this article,we take as given the view that alignment is inherently of value and contributes to organizational success.What we do not take for granted is that alignment is a static,single-dimensional factor or process,or that it is easy to attain.Our goal is to explore the many perspectives taken on alignment and to suggest ways in which academics and practitioners can integrate,build on and apply what has been learned.Challenges in attaining alignmentBefore outlining the approaches and benefits of alignment, we summarize alignment challenges from apractitioner’sperspective.These challenges relate to knowledge,locus of control,and organizational change.Alignment challenges related to knowledgeChallenges related to knowledge refer to the central problem that IT executives are not always privy to corporate strategy, and that organizational leaders are not always knowledgeable about IT.Also,managers are not always knowledgeable about key business and industry drivers.Corporate strategy is unknown:A recurring issue seen in previous alignment research is that often corporate strategy is unknown(Reich and Benbasat,2000)or,if known,is unclear and/or difficult to adapt(Baets,1992). This poses a significant challenge because most models of alignment presuppose an existing business strategy to which an IT organization can align itself.Formal business strategies are often too ambiguous for business managers to understand(Campbell,2005).Man-agers face ambiguity surrounding the differences between espoused strategies,strategies in use,and managerial actions,many of which may be in conflict with one another.This issue of comprehension can be both internal and external to the IT organization.Internal comprehen-sion is affected by mental models and world views, relationships,shared domains of knowledge,and shared systems of meaning.External comprehension is influenced by education and training,the organizational structure and visibility of the IT staff in the structure,and the IT environment.Failures or weaknesses in any of these areas may result in poor alignment.Lack of awareness or belief in the importance of alignment:Although there is empirical support for the notion that alignment provides organizational value, many business managers are unaware of the importance of IT alignment and/or have little belief that IT can solve important business problems(Baets,1996).For instance,in Baets’study of European banks,it was found that the influence of mindsets on IT alignment awareness was significant.Although there was a trend in the use of IT from a support function to a competitive capability, and IT issues were perceived to have a great influence on the banking industry,there was no strong and clear belief that IT could solve specific banking problems. Those managers who could see specific ways to solve banking problems via IT had more positive attitudes towards IT strategy and planning.Similarly,a study by Vitale and colleagues revealed a strong relationship between IT-knowledgeable management and system identi-fication processes that were viewed as satisfactory(Vitale et al.,1986).Henderson and Venkatraman(1993)found that man-agers were more comfortable with their ability to compre-hend business positioning choices(i.e.,where products are sold)rather than IT positioning choices(i.e.,critical technology to support business strategies).This was attributed to the fact that strategy has typically been viewed as something applied to the output market,and that IT has typically been viewed as an internal response(or an input)to business strategy as opposed to something that leverages business strategy.Lack of industry and business knowledge:Baets(1996) found IT alignment was hindered by a lack of knowledge about the banking industry(not just skills and knowledge about IT)among banking managers.In particular,it was found that IT alignment was negatively influenced by the following industry factors:(i)when awareness of the banking industry issues was low and(ii)when the interaction of different aspects within the corporate strategy was not well known to managers.Therefore, before managers could use IT solutions to help solve their banking problems,a deeper knowledge of the banking industry itself was required.In a multiple case study of insurance business units, Reich and Benbasat(2000)showed that shared domain knowledge between business and IT executives was the strongest predictor of the social dimension of alignment. When shared domain knowledge was high,communication between the two groups was strategic and frequent,and the result was a high level of alignment.Alignment challenges related to locus of control and the status of ITCampbell et al.(2005)suggest that when managers are confronted with a business challenge,they make decisions based on their locus of comprehension(understanding) and their locus of control(authority to make decisions). These constraints impact alignment.From this perspective, strategic alignment can be seen as an array of bounded choices made in order to resolve strategic ambiguity (Campbell,2005).Another contributing factor in the attainment of align-ment is the status of IT within the business unit or organization.In a study of cultural assumptions about IT, Kaarst-Brown and Robey(1999)found five separate archetypes.In several of these archetypes,notably the ‘fearful’and the‘controlled’,managers felt that IT was not a benign force within the organization.Therefore,although managers cognitively knew what was needed to achieve IT alignment,practically it was not feasible.Alignment challenges related to organizational change The business environment is constantly changing,and thus there may be no such thing as a‘state’of alignment. Strategic choices made by one organization frequently result in imitation by other organizations.Thus,strategic alignment is a process of change over time and continuous adaptation(Henderson and Venkatraman,1993).Van Der Zee and De Jong(1999)cite a main problem with alignment as the time lag between business and IT planning processes. That is,given that the business environment and technol-ogy change so quickly,once an IT plan is enacted,there is a high probability that the plan and the technology are already obsolete.Having presented challenges to alignment research and practice in organizations,we now turn our attention to defining alignment and presenting variance and process models.These definitions and models create a foundation for future alignmentresearch.What is alignment?Alignment definitionsAlignment has been conceptualized in the academic literature in various ways.Sauer and Yetton(1997)argue that its basic principle is that IT should be managed in a way that mirrors management of the business.4Reich and Benbasat(1996)define alignment as the degree to which the mission,objectives,and plans contained in the business strategy are shared and supported by the IT strategy. Henderson and Venkatraman(1993)state that alignment is the degree of fit and integration among business strategy,IT strategy,business infrastructure,and IT infra-structure.McKeen and Smith(2003)argue that strategic alignment of IT exists when an organization’s goals and activities and the information systems that support them remain in harmony.Good alignment means that the organization is applying appropriate IT in given situations in a timely way,and that these actions stay congruent with the business strategy,goals,and needs(Luftman and Brier,1999).When asking focus group participants to define align-ment,Campbell(2005)was given the following answer:‘Alignment is the business and IT working together to reach a common goal.’Similarly,Abraham(2006) described alignment using a rowing analogy;‘Strategic alignment,is then,everyone rowing in the same direction.’These perspectives do not refer to visions, strategies,plans,structures,etc.that are mentioned in many academic definitions of alignment but their meaning is very clear.However,because of their lack of precision,they are less helpful in articulating what exactly constitutes good alignment and how it might be measured.Equivalent termsIn the literature,alignment has also been called fit (Chan,1992;Henderson and Venkatraman,1993), linkage(Reich,1993),and integration(Henderson and Venkatraman,1993).Chan(1992)defined fit as the degree of coherence between realized business strategy and realized IT strategy.Henderson and Venkatraman(1993) defined fit in terms of the relationship between external business strategy and internal infrastructure and processes. They defined functional integration in terms of the business–IT relationship.Reich and Benbasat(1996,p.56)defined linkage as‘the relationship between the business domain and the IT domain’.These terms and others(e.g.,bridge(Ciborra,1997),harmony(Luftman et al.,1999),and fusion(Smaczny,2001))are sometimes used interchangeably with alignment although subtle differences exist.The term‘fit’has an extensive research stream in the mathematical and strategic management literatures (e.g.,see Edwards,1992).In the MIS literature,it has often,but not exclusively,been used to refer specifically to the measurement of alignment(e.g.,Bergeron et al., 2001).Although it may be argued that‘alignment’is now the dominant term in the MIS literature,this cannot be said for the strategy literature where we also find extensive use of terms such as fit,congruence,and covariation.Alignment dimensionsIn the MIS literature,several dimensions of alignment are clearly apparent:strategic/intellectual,structural,social, and cultural.Although significantly more attention is given to strategic IT alignment,both strategic alignment and structural alignment influence performance.In addition, alignment is contingent on many of the social and cultural aspects of an organization(Reich and Benbasat,1996; Chan,2001).Strategic and intellectual dimensionsStrategic alignment refers to the degree to which the business strategy and plans,and the IT strategy and plans, complement each other.Reich and Benbasat(2000)define intellectual alignment in terms of‘the state in which a high-quality set of inter-related IT and business plans exist.’With this perspective,it is difficult for alignment to occur if the business lacks a formal,documented plan(Vitale et al., 1986;Lederer and Mendelow,1989;Wang and Tai,2003). Kearns and Lederer(2000)argue for a distinction between the information systems plan(ISP)–business plan (BP)and BP–ISP model of alignment.The ISP’s alignment with the BP,or the ISP–BP model,signifies IS manage-ment’s understanding of business strategy(Reich and Benbasat,1996).The BP–ISP alignment model,on the other hand,ensures that the business plan reflects the experience and knowledge of the organization utilizing IT-based resources,and signifies better top management understanding and commitment(Bensaou and Earl,1998).Structural dimensionsStructural alignment refers to the degree of structural fit between IT and the business.Structural alignment is influenced by the location of IT decision-making rights, reporting relationships,(de)centralization of IT,and the deployment of IT personnel(Chan,2002).Pyburn(1983) found that IT is much more likely to be perceived as supporting the critical needs of the business when there are few levels between senior management and IT management. Earl(1989)outlined five ideal IT arrangements:centra-lized,business unit,business venture,decentralized,and federal.In this model,‘arrangement’connotes the struc-tures,processes,and accommodations that evolve when organizing IT.These arrangements need to be aligned with factors such as the host organization characteristics, technology assimilation,the strategic impact of IT,and the IT heritage.Brown and Magill(1994)suggested a simpler structural typology involving IT structures that are centralized, decentralized,or hybrid.They provided evidence that each structure can be effective,given the right circumstances.In their study,the choice of a decentralized IT structure was influenced by a corporate strategy of unrelated diversifica-tion,a decentralized overall firm structure,a culture of strong autonomy without the desire for a CIO,satisfaction with the management and use of technology,and total business unit control over system approvals.The choice of a centralized IT structure resulted from a corporate strategy of related diversification,an overall firm structure of hybrid strategic business units,a culture of central direction,a CIO who was part of the top management team,satisfactionwiththe management and use of technology,and some business unit control of systems approvals.Empirically,Tavakolian(1989)found that IT structure is strongly related to competitive strategy.That is,firms that have a conservative strategy tend to have a centralized IT structure.Those firms that are more entrepreneurial and risk-taking tend to have a decentralized IT structure. Bergeron et al.(2001)found that increasing structural complexity alone has no impact on performance.That is, more complex IT structures are not necessarily superior. However,increasing structural complexity in conjunction with a stronger IT management can increase competitive positions in terms of growth and profitability.The informal structureAlthough the formal structure is most often researched, Chan(2001)found the informal structure to be of great importance in improving IT alignment and performance. The informal structure was defined as‘relationship-based structures that transcend the formal division of labor and coordination of tasks’.Chan’s study suggested that scarce management time and resources are better spent on improving the informal organization than on aligning formal structures.Although less visible than the formal structure,it can be more malleable and paradoxically more enduring.Social dimensionReich and Benbasat(2000)define the social dimension of strategic alignment in terms of‘the state in which business and IT executives within an organizational unit understand and are committed to the business and IT mission, objectives,and plans.’They argue that researchers should study the social and intellectual dimensions of alignment together.This will reveal the complexity and challenges of IT alignment.There are many barriers to achieving both intellectual and social dimensions of alignment and the prerequisite strong CEO–CIO relationship(Feeny et al.,1992).IT personnel and business staff must collaborate together at all levels of an organization.This is a prerequisite for high alignment.Yet this may be hindered by many issues such as the invisibility of the IT staff,communication barriers, history of IT/business relationships,attitudes of organiza-tion members to IT,shared domain of knowledge,and leadership(Earl,1989;Campbell,2005).Cultural dimensionPyburn(1983),in an early study on strategic IT issues, points out the importance of cultural fit between business and IT as a precondition for successful IS planning.He argues that IS planning can validly adopt a personal-informal or a written-formal approach,but that it needs to be aligned with cultural elements such as the business planning style and the top management communication style to be effective.In essence then,alignment needs to be culturally supported; otherwise,it is a never-ending quest.Chan(2002)suggests that a strong company culture is a precondition to the type of informal structure that fosters alignment.Tallon(2003) emphasizes the need for a mind-set that encourages shared networks and common IT procurement policies,and an across-the-board willingness to give up incompatible best-of-breed systems.He states that the‘alignment paradox’cannot be avoided just by picking certain technologies and avoiding others.Flexibility takes vigilance and smart management approaches.Alignment is then fundamentally about cultural change and behavior change(CIO Insight Staff,2004).There has to be commitment from top management for alignment to work.People are not going to listen to what the CIO says as much as they are going to watch what the CIO does,and what the CIO’s business partners do.IT personnel need to be skilled in the softer side of business,which often does not go hand-in-hand with the engineering focus of IT professionals.Top management buy-in,proactive CIOs, and socially adept IT professionals are vital for making alignment a cultural phenomenon.Van Der Zee and de Jong(1999)and CIO Insight Staff (2004)raise the issue of the lack of a common‘language’between business and IT executives.They cite the need to build bridges so that both IT and business personnel are using the same terms,talking about the same topic,which in turn assists with alignment in thought and action.Hunt (1993)states that in well-aligned firms,top management welcomes what can be done through IT,using their understanding of the particular business issues in their company and their imagination when conceiving IT-enabled business strategies.Burn(1993)advocates a cultural audit to examine the relationships between organizational and IT strategy formulation processes.Burn suggests two independent audit checks:one to review the alignment of organizational strategy and structure,and the other to review the alignment of IT strategy and structure.The two audit checks,when applied together,are referred to as the organizational‘cultural’audit framework.Levels of alignmentIdeally,alignment should be present at all levels of the organization,including the organizational level,system level(Floyd and Woolridge,1990;Campbell,2005),project level(Jenkin and Chan,2006),and the individual/cognitive level(Tan and Gallupe,2006).According to Floyd and Woolridge(1990),misalign-ment can often explain system implementation difficulties. Formal strategies are often only implemented at the upper levels of the organizations,yet strategy is carried out on the front line.The focus of alignment at the lower levels of an organization involves translating business unit goals into personal goals(Campbell,2005).Recognizing this problem,Bleistein et al.(2006) attempt to use requirements engineering to link higher-level strategic goals to lower level,explicit organizational processes.Their model provides a mechanism for verifying alignment as requirements are explicitly verified with super-ordinate goals and subordinate goals.Jenkin and Chan(2006)examine alignment at the project level.They define IT project alignment as the degree to which an IT project’s deliverables are congruent with the organization’s IT strategy and the project’s objectives. Critical to project alignment is the project’s responseto。
基于Tsai法的摄像机标定反推修正模型
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Motorola 无线手机产品说明书
MAINTENANCE MANUAL GPS TIMING MODULE ROA 117 2260/1, 2ericssonzSPECIFICATIONSInput V oltage +5 Vdc 10%Current Drain 67 Milliamps (Typical)Operating Temperature -30ºC to +60ºCDimensions 8.0 inches long x 4.0 inches wideConnector P1+5 Vdc A30, A31, B30, B31GroundA1, B1, C1, C12, A32, B32, C32Ericsson Inc.Private Radio Systems Mountain View RoadLynchburg, Virginia 24502AE/LZB 119 1875 R1A1-800-528-7711 (Outside USA, 804-528-7711)Printed in U.S.A.DESCRIPTIONG lobal P ositioning S atellite (GPS) Timing Module ROA 117 2260 is used in the GPS Simulcast Synch Shelf. There are multiple Synch Shelves in the GPS Simulcast System, one at the Control Point and one at each Transmit Site. Each Synch Shelf has two GPS Timing modules, A and B. Each of these are fully redundant.The Timing Module plugs into slots 9 & 10 of the Synch Shelf located at both the Control Point and the Transmit Site.At the Control Point, the Timing Module is an ROA 117 2260/1 and the module at the Transmit Site is an ROA 117 2260/2. One difference is that there is a different PROM in socket XU1 with different programming used between the two locations. Also, front panel LED’s and labels differ: CPTM for C ontrol P oint T iming M odule (Figure 1) and TXTM for T ransmit(X)T iming M odule (Figure 2).The Timing Module has three functions. Each function, though related, is performed differently at each location, control point or transmit site. At the Control Point, these functions:•Generate 300 Hz FSL (Frame Sync Line)•Generate Composite References•Select 9600 Hz ClocksAt the Transmit site, these functions:•Select 9600 Hz clocks•Recover references from composites•Control T1 delayRefer to Figures 1 and 2. The following is a description of the LED indicators found on the front panel of the modules.•PWR - Green LED indicates when power is applied to the module.•ACTV - Green LED indicates when this is the active module.•MAJ - Red LED indicates when a major alarm condition exists.•MIN - Yellow LED indicates when a minor alarm condition exist.•GPS - Yellow LED indicates that there is no signal coming from the GPS receivers. This is at the Con-trol Point.•LL - Yellow LED, at the transmit site, indicates that there is no signal coming from the GPS receivers andthe Land Line signals are being used.•FSL - Yellow LED indicates there is a loss of the Frame Synch Line at the Control Point.•REF 2 - Yellow LED indicates when there is a loss of composite reference 2 at the Transmit Site.•PROG- Switch resets PROM U1 and the Xilinx (FPGA) module U4 to the initial state.•TEST - Connector is an RJ12, 8-Pin connector used for test purposes (Refer to TEST AND TROU-BLESHOOTING). Connector P1 DefinitionCopyright © September 1996, Ericsson Inc.NOTERepairs to this equipment should be made only by an authorized service technician or facility designated the supplier. Any repairs,alterations or substitution of recommended parts made by the user to this equipment not approved by the manufacturer could voidthe user’s authority to operate the equipment in addition to the manufacturer’s warranty.This manual is published by Ericsson Inc., without any warranty. Improvements and changes to this manual necessitated by typographical errors, inaccuraciesof current information, or improvements to programs and/or equipment, may be made by Ericsson Inc., at any time and without notice. Such changes will be in-corporated into new editions of this manual. No part of this manual may be reproduced or transmitted in any form or by any means, electronic or mechanical, in-cluding photocopying and recording, for any purpose, without the express written permission of Ericsson Inc.AE/LZB 117 1875 R1A1Figure 1 - Control Point Timing Module Front PanelFigure 2 - Transmit Site Timing ModuleAE/LZB 117 1875 R1A 2CIRCUIT ANALYSISFunctional circuitry is primarily contained in a Xilinx 3190A FPGA(F ield P rogrammable G ate A rray) integrated circuit (U4). This circuitry is programmed differently for con-trol and transmit applications.The GPS Timing module has hot standby capability. Cir-cuitry outside the FPGA provides this capability as well as I/O interfaces and a P hase-L ock-L oop (PLL). The PLL is used at the transmit site.Xilinx 3190A FPGA U4 is wired in master serial mode, which determines how programming is accomplished (Figures 4 & 5). These figures are included for those familiar with Xilinx technology and are not described within this document.At power up, following the release of the Reset/reprogram push-button switch S1, or following automatic detection of a Xilinx fault, data PROM U1 is read serially into U4. A watchdog function is performed by 555 timer, U5 in the Activity Detector circuit. This timer causes a reprogramming if the 9600 Hz selected clock is not provided by U4 (automatic Xilinx fault detection).Crystal B1 provides a 4.9152 MHz clock used internally by the Xilinx logic.This board operates from a single +5 volt supply. An on-board thermister fuse (F1) prevents module failure from causing this shelf supply to collapse.Input signals arrive as RS-422 levels and are converted to TTL logic levels by RS-485 receivers U9, U11, and U14. Input fault lines connect directly to U4, as they arrive at TTL logic levels. The outputs driving the GPS ReSync modules (located in the same shelf) are buffered with tri-state line drivers U7, U13 and U15. The RS-422 level outputs are generated using RS-485 drivers U16-U20. The tri-state controls on all these drivers are used by the hot standby circuitry to turn the output to high impedance when the module is in hot standby. The circuitry attached to RC_IN and RC_OUT provides operational/hot-standby selection; these leads tie through the backplane to the companion module.PLL U3 provides a de-jitter filter with zero phase shift on the recovered landline 9600 clock. This PLL is used only at the transmit site.CONTROL POINTThe major functions performed at the Control Point areshown in Figure 3. The GPS signal selection block selects a9600 clock and 1 pps signal from either of the redundant GPSlocked clock sources. The Clock Generator block generates a19200 Hz clock for use by the other blocks. The 300 HzGenerator generates the 300 Hz required by the ReSync bydividing the selected 9600 Hz by 32. It also ensures that thephase of this 300 Hz is proper relative to the F rame S ync L ine(FSL) input. The Composite Reference Generator takes theselected 9600 Hz clock and inserts tags at the proper times tocreate reference signals that contain:•Composite Reference 1 contains 9600 Hz clock plustags for 300 Hz and pseudo FSL.•Composite Reference 2 contains 9600 Hz clock plustags for 1 pps.These Composite References are extracted at the transmit site.The 300 Hz generator and the Composite Reference Generatorare implemented as state machines.TRANSMIT SITEThe major functions performed at the transmit site are shownin Figure 4. There are similarities to the Control Point. The clockgenerator generates a 19,200 Hz clock for internal use; the GPSsignal selection block selects the 1 pps and 9600 Hz clock fromthe two redundant GPS locked clock sources. In addition it alsoprovides for selection of the landline 9600 Hz in the unlikelyevent that both GPS sources are failed. The Signal Recoveryblock is the corresponding function of the Composite ReferenceGenerator at the Control Point. It extracts the 9600, 300 1 ppsand pseudo FSL from the reference signals. The 9600 Hzlandline is routed off the Xilinx IC (U4) to be filtered by thePLL and returned for use by the T1 delay module. The T1 delaymodule examines the selected GPS signals (1 pps and 9600) andcompares their phase to the corresponding landline signals. Ifcertain “hysterisis hurdles” are exceeded the number of T1cycles of delay desired are serially sent to the Intraplex MUXwhere the actual delay is accomplished. This Delay Controlblock and Signal Recovery block are implemented with statemachines.SELECTORC L O C KTO CPTC(RS-422)9.6 DATA ANDCLOCK TO MUX(RS-422)TO MUX(RS-422)(RS-422)GPS BGPS A9.6Figure 3 - Functions at the Control Point (CPTM)AE/LZB 117 1875 R1A3GPS AGPS BTO RESYNC MODULESTO MUX F R O M G P SA L A R M Figure 4 - Functions at the Transmit Site (TXTM)1U U 00 H zS L *d r i v eS L *t e s to m p R e f 1o m p R e f 2Figure 5 - Xilinx 3190A FPGA at the Control PointAE/LZB 117 1875 R1A4TEST AND TROUBLESHOOTINGThe GPS Timing operates in two functionally different applications. Some of the functionally is the same for both applications and some is complementary to the other applica-tion. The module contains a PROM which holds the configu-ration information for the application.The functions to be tested are described previously for the control point and transmit site application.Signal on test connector P2:Control PointPin 1 - Composite Ref. 1Pin 2 - 1pps GPS Pin 3 - nc Pin 4 - FSL*Pin 5 - Selected 9600 (ReSync)Pin 6 - 300 outPin 7 - Composite Ref. 2Pin 8 - nc Transmit SitePin 1 - T1 Delay Data Pin 2 - 1pps GPS Pin 3 - 1pps landline Pin 4 - FSL*Pin 5 - Selected 9600 (ReSync)Pin 6 - 300 out Pin 7 - ncPin 8 - 9600 PLL * Pseudo FSL.To test as a Control Point module:The module must be powered up and supplied with GPS signals (9600 Hz, 1pps and an FSL). The presence of the “selected” signals at all the proper outputs and of the gener-ated signals (300, Comp Ref. 1 and Comp Ref. 2) must be verified. This is done for GPS “A” and “B”. The generated Comp Ref. 1 and Comp Ref. 2 need to be checked to verify the “tag” is placed consistently following the corresponding event.With no signals present, the MINOR alarm goes active;the green activity (ACTV ) LED goes out and the red MAJOR alarm LED comes on.To test the Transmit Site:It is desirable to have an operational module in the Control Point mode to provide the Comp Ref. 1 and Comp Ref. 2signals. Signal selection is checked similar to that done at the Control Point with the additional fault mode of reverting to landline 9600 if neither GPS source is present. A second GPS source allows a precise time difference between the landline 1pps and the “direct” 1pps to test the T1 delay portion of the module. A known time difference is programmed onto the local GPS and the T1 delay output is examined to verify that a new delay value is sent. As there is no MUX (& T1 delay module) the correction will successively add to itself.U TS 2S 01p p s L LS E L 300T 1_C L O C A S M _C L C O M P _R E F 1Figure 6 - Xilinx 3190A FPGA at the Transmit SiteAE/LZB 117 1875 R1A5*COMPONENTS ADDED, DELETED OR CHANGED BY PRODUCTION CHANGESDATACLKRESET/OE(OE/RESET)CE G N DC E OVppVccU1PROMRON 107 786 CPTM (XC1765D)RON 107 787 TXTM(XC1765D)U2DUAL D FLIP/FLOPRYT 306 2003/C (74HC74)á = Transition from low to high levelQ0 = The level of Q after the previous clock pulse* = Nonstable, don’t preset when PR and CLR are set highX = Any input, including transition18916U3PHASE-LOCK-LOOPRYT 306 6075/C (74HCT4046)CONNECTIONS PARTS LIST IC DATAAE/LZB 117 1875 R1A 6Positive Logic: Y=A • BPositive Logic: Y=A+B26U4XILINXRYT 139 003/5C(3190A)V DSCHTHRESCONTGNDTRIG OUTU5555 TIMER RYT 108 6003/CG N DVcc 4B 4A 4Y 3B 3A 3Y2Y 2B2A 1Y1B1A U6QUAD NAND GATERYT 306 2001/C (74HC00)G NDVcc C4A4Y4C3A3Y3Y2A2C2Y1A1C1U7, U13, U15TRI-STATE BUFFER RYT 3066029/C (74HC125)Vcc 4Y 4B 4A 3Y 3B 3AG N D 2B2A 2Y 1B 1A 1Y U8QUAD NORGATERYT 306 2006/C (74HC020)IC DATAAE/LZB 117 1875 R1A7VccB4A4R 04E N 34R 03A3B3G N D B2A2R 02E N 12R 01A1B1U9, U11, U14RS-485 QUAD RECEIVER RYT 109 6079/2C (LTC489)Vcc DI 4DOA 4D O B 4E\DOB 3DOA 3DI 3G N DDI 2DOA 2DOB 2E DOB 1DOA 1DI 1U16 - U20RS-485 QUAD DRIVERRYT 109 6078/1C (LTC486)E EDOA1DOB1DOA2DOB2DOA3DOB3DOA4DOB4CONNECTIONSH: High Level L: Low Level X: Irrelevant Z:HighImpedance (Off)FUNCTION TABLEIC DATAAE/LZB 117 1875 R1A8OUTLINE DIAGRAM AE/LZB 117 1875 R1AOUTLINE DIAGRAM(1078 ROA 117 2260, Rev. B)9AE/LZB 117 1875 R1ASCHEMATIC DIAGRAMSCHEMATIC DIAGRAM(1911 ROA 117 2260, Sh. 1, Rev. B)SCHEMATIC DIAGRAM AE/LZB 117 1875 R1ASCHEMATIC DIAGRAM(1911 ROA 117 2260, Sh. 2, Rev. B)AE/LZB 117 1875 R1ASCHEMATIC DIAGRAMSCHEMATIC DIAGRAM(1911 ROA 117 2260, Sh. 3, Rev. B)AE/LZB 117 1875 R1A This page left blank intentionally。
Collaborative networks and product innovation performance--Toward a contingency perspective
Research Policy 38(2009)765–778Contents lists available at ScienceDirectResearchPolicyj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /r e s p olCollaborative networks and product innovation performance:Toward a contingency perspectiveKuen-Hung Tsai ∗Department of Business Administration,National Taipei University,151University Rd.,San Shia,Taipei 237,Taiwana r t i c l e i n f o Article history:Received 3October 2007Received in revised form 11September 2008Accepted 26December 2008Available online 29January 2009Keywords:Collaborative networkProduct innovation performance Absorptive capacitya b s t r a c tAn increasing number of studies have examined the impact of collaborative networks on product innova-tion performance,but have produced inconsistent results.This research contributes to existing literature by examining how absorptive capacity affects the relationships between different types of partners and product innovation performance.The sample used in this research is drawn from the Taiwanese Tech-nological Innovation Survey (TTIS)database.A moderated hierarchical regression approach is used to analyze the models,which are further explored by firm size and industry type.Some interesting findings appear.First,absorptive capacity positively moderates the impact of vertical collaboration on the per-formance of technologically new or improved products.Second,the effect of absorptive capacity on the relationship between supplier collaboration and the performance of new products with marginal changes varies based on firm size and industry type.Third,absorptive capacity negatively affects the relationship between customer collaboration and the performance of marginally changed products.Fourth,absorptive capacity positively affects the relationship between competitor collaboration and the performance of new products with marginal changes for large firms.Fifth,absorptive capacity negatively affects the relation-ship between collaboration with research organizations and the performance of technologically new or improved products.On the contrary,absorptive capacity positively affects the impact of collaboration with research organizations on the performance of marginally changed products.These results enrich current understanding of the relationships between collaborative networks and product innovation performance.©2009Elsevier B.V.All rights reserved.1.IntroductionGiven the intense competition in most markets today,compa-nies are increasingly recognizing the necessity and advantages of regularly developing new products.Firms that introduce higher-quality products faster than their competitors usually earn higher economic returns (Datar et al.,1997).However,rapid changes in technology often force such firms to depend on external technological knowledge and skills in addition to internal techno-logical resources.Many firms today are relying more extensively on external linkages to acquire new technological knowledge using strategies such as technology licensing and collaborative agreements.Inter-firm collaboration is an important vehicle for the creation of technological competencies (Schoenmakers and Duysters,2006),and is a viable solution to the problem of resources and capabilities not always being available within a firm and diffi-cult to obtain efficiently in the market (Das and Teng,2000).While most research on this topic focuses on the motives behind R&D collaboration (e.g.,Fritsch and Lukas,2001;Tether,2002;∗Tel.:+886286746568;fax:+886286715912.E-mail address:atmas@.tw .Miotti and Sachwald,2003;Belderbos et al.,2004b ),a number of authors have evaluated the impact of different types of collaborative networks on product innovation performance (Lööf and Heshmati,2002;Criscuolo and Haskel,2003;Miotti and Sachwald,2003;Belderbos et al.,2004a;Faems et al.,2005;Nieto and Santamaría,2007).However,these studies present inconsistent results:some show that these relationships are negative or insignificant,while others find they are positive.This ambiguity implies that other factors may moderate the relationship between collaborative net-works and product innovation performance.Given that inter-firm collaboration is an effective vehicle for organizational learning,prior research argues that a sufficient degree of absorptive capac-ity is required for effective learning in a collaborative agreement between firms (Mowery et al.,1996;Lane et al.,2001).Despite a growing interest in the link between organizational learning and product innovation (e.g.,Adams et al.,1998;Erwin,2002),rela-tively little research examines how absorptive capacity moderates the relationship between external linkages and product innova-tion.The lack of research on this issue is surprising,especially since some important works (e.g.,Cohen and Levinthal,1990;Kim,1997,2001;Teece,2000)emphasize that a firm’s absorptive capacity determines the extent to which it is able to utilize external knowl-edge.0048-7333/$–see front matter ©2009Elsevier B.V.All rights reserved.doi:10.1016/j.respol.2008.12.012766K.-H.Tsai/Research Policy38(2009)765–778The present study therefore addresses the question:Dofirms with a high level of absorptive capacity realize higher product innovation from close collaboration thanfirms with a low level of absorptive capacity?Answering this question can make a signif-icant contribution to the literature on this topic.While previous studies focus on the effects of collaborative networks on prod-uct innovation performance,this paper proposes a contingency framework to address the value of absorptive capacity in explain-ing the relationship between collaborative networks and product innovation performance.Additionally,this study advances research on absorptive capacity by empirically examining its effect on the use of external knowledge for product innovation.Answers to the question of absorptive capacity are also important because they are relevant tofirms that depend to a large extent on technol-ogy acquired from collaborating with different partners.In their efforts to reduce the costs and risk of technology development and to introduce higher-quality products faster than competitors,firms may count heavily on the effectiveness with which they can gain access to external sources of technological knowledge and skills. While some previous studies suggest that collaborating with dif-ferent partners is an effective way to improve product innovation (e.g.,Belderbos et al.,2004a;Nieto and Santamaría,2007),this research sheds light on the importance of absorptive capability in the effectiveness of collaborative networks.The remainder of this paper is organized as follows.Follow-ing this introduction,Section2reviews the literature and provides theoretical expectations.Section3introduces the research meth-ods,including the model,variable definitions and measurements, and the data source utilized in this study.Section4presents the results and discussions.Section5summarizes the results,discusses their implications for theory and managerial practice,and suggests possible directions for future research.2.Literature review and research hypotheses2.1.The impact of different types of partnersPrior research suggests that afirm can advance its product innovation by interacting with different collaborators,primarily including suppliers,customers,competitors,and research orga-nizations.Suppliers usually have greater expertise and more comprehensive knowledge regarding the parts and components which may be critical to afirm’s new product development.Thus, supplier collaboration can allowfirms to incorporate the exper-tise and different perspective of a supplier to improve its solutions or create new methods for product development(Bonaccorsi and Lipparine,1994;Eisenhardt and Tabrizi,1995).Supplier involve-ment also helpsfirms identify potential technical problems,thereby speeding up new product development and responses to market demands(Kessler and Chakrabatri,1996).Miotti and Sachwald (2003)used the French CIS-2survey to reveal the positive effect of collaboration with suppliers on the share of innovative prod-uct turnover.Faems et al.(2005)analyzed Belgian manufacturing firms and found a positive association between suppliers and the proportion of turnover attributed to improved products.In a sur-vey of Spanish manufacturingfirms,Nieto and Santamaría(2007) regressed product innovation on collaborative networks and found a positive link between collaboration with suppliers and the degree of product innovativeness.However,Sánchez and Pérez(2003) analyzed Spanish manufacturingfirms and concluded that collabo-rating with suppliers does not improve new product performance. Freel(2003)analyzed UK small and medium-sized manufacturing firms and found that supplier collaboration does not have a signif-icant impact on new product performance.Ledwith and Coughlan (2005)used a sample of electronicsfirms in Ireland and the UK and found an insignificant correlation between collaboration with sup-pliers and product innovation performance.In addition,Belderbos et al.(2004a)studied Dutch manufacturingfirms and found a negative but insignificant relationship between collaboration with suppliers and product innovation performance.Collaborating with customers is another important way for a firm to improve its product innovation performance(Gupta et al.,2000;Fritsch and Lukas,2001;Brockhoff,2003).Working with customers not only provides benefits in identifying market opportunities for technology development,but also reduces the likelihood of poor design in the early stages of development.In addition,understanding the needs of influential customers may helpfirms gain new ideas about solutions(von Hippel et al.,1999) and identify market trends early on,thereby increasing the chances of new product development and success.Thus,customer involve-ment may lead to product innovation advantages(Souder et al., 1997;Li and Calantone,1998).Miotti and Sachwald(2003),Freel (2003),and Faems et al.(2005)all found that collaboration with customers has a positive impact on product innovation perfor-mance.In contrast,Lööf and Heshmati(2002)analyzed Swedish manufacturingfirms and found a negative relationship between customer collaboration and product innovation performance.Nieto and Santamaría(2007)found that customer collaboration has a positive impact on product innovation with marginal changes,but does not affect significant innovation with new functions.In addi-tion,Belderbos et al.(2004a)revealed an insignificant association between collaboration with customers and changes in new product sales.Monjon and Waelbroeck(2003)analyzed French manufactur-ingfirms and found that customer collaboration has an insignificant impact on product innovation.The least frequent type of collaborative network thatfirms adopt to achieve product innovation seems to be collaboration with com-petitors(Bayona et al.,2001;Nieto and Santamaría,2007),but this type of collaboration still provides some advantages.Firms involved in a cooperative agreement may share technological knowledge and skills with each other,producing a synergistic effect on solv-ing common problems outside the competitor’s area of influence (Tether,2002).The case study of Inkpen and Pien(2006)suggests thatfirms collaborating with competitors may perform better in innovation than they would otherwise.At the same time,firms can accelerate their capability development by R&D cooperation,which allows them to reduce the time and risk involved in technologi-cal innovation(Belderbos et al.,2004a).Furthermore,collaborating with competitors enablesfirms to ascertain their competitors’tech-nological level;firms that are more knowledgeable about their competitors’technology strategies are better able to differenti-ate themselves(Linn,1994).Lööf and Heshmati(2002)found that collaborating with competitors is positively related to new prod-uct sales.However,Monjon and Waelbroeck(2003),Miotti and Sachwald(2003),and Belderbos et al.(2004a)found that com-petitor collaboration has a negative but insignificant impact on product innovation performance.Nieto and Santamaría(2007)also found that collaboration with competitors does not impact prod-uct innovation with marginal modifications,but it negatively affects product innovations with new functions.Due to governments’encouragement,more and morefirms are pursuing product innovations by collaborating with universities and research institutions.Universities and research institutes are important centers for the creation and dissemination of scientific knowledge(Hemmert,2004).Firms can interact formally and informally with universities and research institutes to acquire new scientific knowledge to benefit their product or process innovations(Caloghirou et al.,2004).In contrast,afirm choosing not to acquire technological knowledge from universities and research institutions may fall behind,reducing the likelihood that it will make a technological breakthrough leading to a commercial product(Spencer,2003).Several studies suggest that technologicalK.-H.Tsai/Research Policy38(2009)765–778767innovation relies heavily on knowledge from universities and research institutions(Bozeman,2000;McMillan et al.,2000;Vuola and Hameri,2006).Belderbos et al.(2004a),Faems et al.(2005), and Nieto and Santamaría(2007)found that collaboration with research institutes and universities positively affects product inno-vation performance.However,Monjon and Waelbroeck(2003), Caloghirou et al.(2004),and Ledwith and Coughlan(2005)found that collaboration with universities and research institutes has a negative effect on product innovation performance.Furthermore, Lööf and Heshmati(2002)revealed an insignificant relationship between collaboration with research organizations and product innovation performance.In summary,the empirical studies reviewed above show that while there is some support for collaborating with different part-ners in product innovations,there is an absence of consensus on the benefits of this type of networking.Surprisingly,though most of the studies mention the importance of absorptive capacity,they do not investigate its moderating role.Therefore,the way in which absorptive capacity affects the relationship between collaboration and product innovation performance is worthy of further study.2.2.The role of absorptive capacityAbsorptive capacity refers to afirm’s ability to use its own prior related knowledge to recognize,assimilate,and use exter-nal knowledge for its own commercial ends(Cohen and Levinthal, 1990).Zahra and George(2002)and Todorova and Durisin(2007) further characterized absorptive capacity as a bundle offive capa-bilities:recognition,acquisition,assimilation,transformation,and exploitation.Obviously,afirm with a high level of absorptive capac-ity is better able to create and exploit linkages with otherfirms (Caloghirou et al.,2004).The absorptive capacity of afirm is greatly dependent on its current level of technological knowledge(Cohen and Levinthal,1990;Kim,1997,2001),which in turn is derived from previous and current efforts in internal R&D(e.g.,Veugelers,1997; Stock et al.,2001;Schoenmakers and Duysters,2006).Numerous studies argue that a certain degree of absorptive capacity is required for effective learning in inter-organizational collaborations(e.g., Mowery et al.,1996;Kim,1998;Lane and Lubatkin,1998;Lane et al.,2001).Organizations with a greater absorptive capacity usually have a sufficiently developed technology base that enables them to have rich and detailed communications with their suppliers dur-ing the knowledge-sharing process.This communication process, in turn,may generate new ideas or solutions for product designs. Further,suchfirms are more likely to recognize the value of new ideas and effectively integrate them into their product develop-ment efforts.As certain ideas are completely de novo,it is necessary to develop new parts and components to produce significant inno-vations.Unrealistic designs or incompatible parts and components may seriously delay the development cycle(Culley et al.,1999). Thus,close collaboration with suppliers is important during the engineering process to shorten the development time and ensure the quality of new products.In contrast,an organization with a lower absorptive capacity mayfind it difficult to recognize the value of new ideas which emerge from interactions with their suppliers.Afirm may also lack sufficient ability to integrate ideas into new products.In this case, close collaboration with suppliers may waste time and money and, as a result,inhibit new product performance.Based on these argu-ments,this study expects that the greater the absorptive capacity, the stronger the relationship between collaboration with suppliers and product innovation performance.Absorptive capacity can also enhance the use of knowledge from customer collaboration in product innovation.In working closely with customers,and particularly with influential customers,afirm may uncover latent customer needs(Atuahene-Gima et al.,2005). These unarticulated needs alert thefirm to new market opportu-nities,technology developments,and ideas that challenge existing cause-effect relationships,thereby resulting in new products with significant benefianizations with a greater absorptive capac-ity are more likely to identify,convert,and exploit these needs using new technological knowledge.Absorptive capacity,then,improves afirm’s chances of capturing new market opportunities by mak-ing innovative products.Hence,afirm’s performance in product innovation may be improved by close customer collaboration.Con-versely,an organization lacking sufficient absorptive capacity will be unable to integrate the latent customer needs into new product developments.Thus,even if afirm collaborates closely with cus-tomers,these activities may not increase thefirm’s performance in product innovation,and may even be detrimental to such per-formance.Based on the arguments above,this study proposes that the greater the absorptive capacity,the stronger the relation-ship between collaboration with customers and product innovation performance.The impact of any external knowledge absorbed from com-petitor collaboration on product innovation may also depend on absorptive capacity.By establishing collaborative arrangements, afirm can access the specialized knowledge of its competitors, which is usually tacit and cannot be easily copied by simple obser-vation.Inkpen and Pien’s(2006)case study suggests thatfirms with a sufficiently developed technology base are able to iden-tify and understand the knowledge that underpins similarities and differences in their collaborators’skills.As a result,they may be more likely to incorporate competitor knowledge and expertise in their own technological innovations.Further,the research of Kim and Song(2007)suggests that absorptive capacity may facilitate the creation of new technology through collaboration with other companies.Afirm with a greater absorptive capacity has a better technology base that enables it to understand and exploit competi-tors’skills and knowledge(Cohen and Levinthal,1990),thereby resulting in significantly innovative products.For example,given that Hewlett–Packard(HP)had developed its own laser printing capabilities,it chose to work with canon to develop the desk-top laser printer and achievefirst-mover advantages in personal laser printers(Helleloid and Simonin,1994).Therefore,this study hypothesizes that the greater the absorptive capacity,the stronger the impact of collaboration with competitors on product innovation performance.Research organizations are an important source of new scien-tific knowledge.Collaborating with research organizations enables afirm to access scientific knowledge previously unexplored.This knowledge may provide thefirm with different modes of reason-ing,problem formulation,and solutions(Amabile,1988).Exposure to these different approaches adds to the repertoire that afirm can bring to bear on new product development problems.The process of combining new technological knowledge into existing knowl-edge can foster insights that can then lead to additional insights and profundity,thereby offering significantly higher potential for breakthrough innovations(Ahuja and Lampert,2001).However, case studies and empirical evidence show that absorptive capacity is important for afirm,especially for SMEs,to achieve success-ful collaboration with research institutions(Koschatzky,2002; Hadjimanolis,2006).While collaborating with research organiza-tions,firms with a high level of absorptive capacity are better able to learn new perspectives that may provide better,more effective solutions in new product development.In contrast,an organization that lacks sufficient absorptive capacity may be unable to digest advanced technologies when closely collaborating with research organizations.Thus,this study hypothesizes that the greater the absorptive capacity,the stronger the impact of collaboration with research organizations on product innovation performance.768K.-H.Tsai /Research Policy 38(2009)765–778In summary,with an adequate degree of absorptive capacity,firms will be better at internalizing their partners’knowledge,and thereby improve their chances for product innovations.Whether or not the benefits of collaborating with different types of partners can be realized may be affected by the parent organization’s absorptive capacity as derived from its existing technological knowledge.Con-versely,an inability to identify and understand the technological knowledge that underpins partners’competencies limits a firms’collaborative learning potential.3.Research method 3.1.Conceptual frameworkFig.1shows the conceptual framework investigated in this study.This framework indicates that the product innovation performance of a firm is affected by its collaborative networks in terms of differ-ent types of partners.It further proposes that these relationships are influenced by the absorptive capacity of a firm.In addition,sev-eral important controls are included in the model to eliminate or reduce the bias arising from the confounding effects.This frame-work guides the definitions and measures of the major variables used in this study.3.2.Variable definitions3.2.1.Dependent and independent variablesThe dependent variable in this study is product innovation per-formance,which is measured by innovative sales productivity.This study operationalizes this measure as the sales generated by new products per employee (i.e.,the ratio of sales attributed to new products divided by the total number of employees).These sales include (1)technologically new or technologically improved prod-ucts introduced to the market within the past 3years,and (2)marginally changed products within the same time period.Note that this study does not measure product innovation performance by the volume of new product sales because this measure signif-icantly correlates with firm size.A technologically new product is a product whose technological characteristics or intended uses differ significantly from those of existing products (OECD,1997).A technologically improved product refers to an existing product whose performance has been significantly improved or upgraded (OECD,1997).A marginally changed product is an innovative prod-uct that cannot be categorized into either of the first two groups.The independent variables in this study are the four types of col-laboration with different partners,including suppliers,customers,Fig.1.Conceptual framework.competitors,or research institutes and universities.These variables measure the level of collaboration with different types of partners.This study constructs each of these variables by the product of two variables in the TTIS database.One is a dummy variable which takes the value of 1if the firm is engaged in collaboration with a specific type of partner,else 0;the other is the relative importance (high,medium,and low)of collaboration with this partner,indicating how close the collaboration is.3.2.2.Moderator and controlsThe moderating variable in this research is absorptive capacity.The absorptive capacity of a firm depends greatly on its existing technological knowledge base (Cohen and Levinthal,1990;Kim,1997,2001).If a firm lacks a sufficiently developed technologi-cal knowledge base,it may have difficult absorbing any externally acquired technological knowledge (Schoenmakers and Duysters,2006).Firms can only be expected to learn from their collaboration partners if they have some level of prior technological knowledge which they can us to incorporate their partners’knowledge and use it for their own purposes.Prior research views in-house R&D invest-ment as the key determinant of a firm’s absorptive capacity (e.g.,Cohen and Levinthal,1990;Mowery et al.,1996;Stock et al.,2001;Carayannis and Alexander,2002;Todorova and Durisin,2007).The absorptive capacity variable is measured by dividing the firm’s total expenditures on in-house R&D activities and training programs for technological activities in the past 3years by its total number of employees in a current year.Note that the numerator of the vari-able is a stock measure,as in previous studies (e.g.,Helfat,1997;Ahuja and Katila,2001),usually used as a proxy for the firm’s tech-nology base acquired from previous and current R&D or training activities.However,this study does not use in-house R&D or train-ing stock to measure a firm’s internal efforts in innovation activities because this measure is always highly correlated with firm size.This type of measure represents a firm’s absorptive capacity more accurately than the R&D intensity measure (R&D expenditure/sales)widely used in prior research (e.g.,Jones et al.,2001;Belderbos et al.,2004a;Faems et al.,2005;Schoenmakers and Duysters,2006;Nieto and Santamaría,2007).More importantly,this measure reflects existing knowledge accumulated from past learning and intensity of effort,which are both important elements of absorptive capacity (Cohen and Levinthal,1990;Kim,1997,2001).The research model in this study also contains several impor-tant controls.The first control is the use of industry dummies for fixed industry effects.As stressed in prior research,these dummies capture various environmental dimensions such as tech-nological opportunity and competition intensity (e.g.,Veugelers,1997;McGahan and Porter,1997).This analysis uses seven indus-try dummies representing eight traditional manufacturing sectors.The second control is the size of the firm as measured by its total number of employees,which is a proxy for size in previous studies related to innovation performance (e.g.,Caloghirou et al.,2004;Schoenmakers and Duysters,2006).Next,the average ratio of employees with a university degree or higher by total number of employees serves as a proxy for the quality of the firm’s human resources,which is an important determinant of innovation output in the literature (e.g.,Rothwell and Dodgson,1991;Jones,2001).In addition,this study controls for the effects of inward technology licensing since previous studies emphasize the role of this control on innovation (e.g.,Zahra et al.,2005;Tsai and Wang,2007).Inward technology licensing in this study comprises the firm’s expendi-tures on external technology acquisition through inward licensing.The last control is a dichotomous variable that takes the value of 1if the firm is mostly foreign owned;else zero.Previous studies suggest that the subsidiary of a foreign parent company may per-form better in bringing new product products to the market than a host company (e.g.,Deeds and Hill,1996;Belderbos et al.,2004a ).K.-H.Tsai/Research Policy38(2009)765–778769Table1Means,standard deviations,and correlations(N=753).Variable PIP CL S CL C CL P CL R ACAP FS HQ ITL SBPIP 1.000CL S0.084b 1.000CL C0.116a0.435a 1.000CL P−0.0030.219a0.237a 1.000CL R0.0500.116a0.062c0.083b 1.000ACAP0.361a0.074b0.129a−0.003−0.001 1.000FS0.159a0.153a0.180a0.0030.270a0.058 1.000LQ0.123a0.094a0.0340.011−0.086b0.080b−0.039 1.000ITL0.131a0.081b0.142a0.0510.103a0.210a0.309a0.050 1.000SB0.044−0.070c−0.026−0.058−0.0110.0120.060c−0.0430.021 1.000Mean50.60.2590.4290.0900.2370.253444.410.226 5.8010.072 S.D.75.60.739 1.0020.4310.6090.6181215.000.22633.870.258Notes:(1)PIP:product innovation performance;CL S:collaboration with suppliers;CL C:collaboration with customer;CL P:collaboration with competitors;CL R:collaboration with research organizations;ACAP:absorptive capacity;FS:firm size;LQ:labor quality;ITL:inward technology licensing;SB:subsidiary.(2)Unit of analysis for PIP is thousand NT dollars;and ITL is million NT dollars;FS,person.a p<0.01.b p<0.05.c p<0.10.Therefore,this study uses this variable to control for the effects of thefirm’s managerial style on innovation output.3.3.The dataThis study analyzes data at thefirm level.Both the sample and the variables used in this analysis come from the Taiwanese Techno-logical Innovation Survey(TTIS),jointly conducted by the National Science Council and the Ministry of Economic Affairs in2002.The sample is representative of the population of traditional Taiwanese manufacturingfirms because the sampling frame was generated by a stratified random sampling process based onfirm size and industry.The database consists of1346firms in various manufac-turing industries.Among this total,firms indicating that they had not engaged in technological innovation activities during the pre-vious3years were excluded from this study since their profiles do not contain any data for external technology sourcing variables. The sample includes a total of753firms for the preliminary anal-ysis and the model estimation.Thesefirms are categorized into eight sectors:food,beverages&tobacco(40firms,5.31%);textile, wearing apparel&leather(56firms,7.44%);paper&printing(29firms,3.85%);chemical,rubber&plastic(130firms,17.26%);non-metallic mineral(28firms,3.72%);basic metal(22firms,2.92%); fabricated metal(108firms,14.34%);and machinery,electronics &transportation equipments(340firms,45.15%).Within the sam-ple,the percentage of reported collaboration with suppliers,clients, competitors,and research organizations is about20%,18%,8%,and 23%,respectively.Thesefigures reveal that competitor collaboration does not seem to be the best way to improve innovation.This may be caused by problems of technological knowledge leakage and the increased risk of hold up in competitor collaboration(Bayona et al., 2001).Thisfinding is consistent with that of Nieto and Santamaría (2007).Moreover,collaboration with research organizations seems to be the most frequent type of partnership.This phenomenon is unlike that of a large number of European countries documented in Drejer and Jørgensen(2005)and Nieto and Santamaría(2007), where collaboration with suppliers was the most important.Table1 reports the basic statistics for the variables(except for the industry dummies)used in the analysis.Table1shows some interestingfindings.First,all of the correlation coefficients for the collaboration variables(except collaboration with research organizations)achieve a statistical sig-nificance at the5%significance level.This indicates that a certain proportion of thefirms within the sample collaborate with more than one type of partner for technological innovations.In particu-lar,firms collaborating with suppliers tend to also collaborate with their customers(r=0.44,p<0.01).Second,competitor collabora-tion has the lowest value in its mean and standard deviations among the collaboration variables.This result shows that collaboration with competitors is the least common type of partnership for prod-uct innovation within the sample.Third,a significant correlation exists betweenfirm size(FS)and product innovation performance (PIP).This preliminary analysis suggests that largefirms have an innovation advantage over smallerfirms in terms of output,sup-porting the Schumpeterian hypothesis.4.Analyses4.1.ResultsThe models in this study are estimated by OLS-based hier-archical regression.Model1contains several control variables, including industry dummies(IND1–IND7),firm size(FS),labor quality(LQ),inward technology licensing(ITL),and subsidiary (multi-nationality)dummy(SB).Then,absorptive capacity(ACAP) and the collaboration variables(CL S,CL C,CL P,and CL R)are entered in Model2.The terms of the interaction between the collabora-tion variables and the ACAP variable are added in Model3.Because the interaction terms are usually highly correlated with ACAP or the collaboration variables,this study follows the procedure sug-gested by Friedrich(1982)to reduce or eliminate any bias resulting from multi-collinearity.This approachfirst standardizes the vari-ables except for the dummies and then forms the cross-product terms.Table2presents the moderated regression analysis results for the models.Table2indicates that adding the collaboration and ACAP vari-ables(Model2)to the model with only controls(Model1)increases the R2by about38.2%.The F-value(106.48)for the incremental R2 values achieves a statistical significance at the1%level.An inspec-tion of the coefficient estimates of the collaboration variables shows that these variables do not explain the change in product inno-vation performance.This result implies that collaboration with different types of partners does not increase product innovation performance when the analyses does not account for the effect of absorptive capacity.1Adding the interaction terms(Model3)to Model2further increases the R2by about1.7%.The F-value(4.63) 1This result confirms to that documented in Brouwer and Kleinknecht(1996), Love and Rpoer(2001),and Freel(2003).。
基于边缘提取的图像压缩编码
基于边缘提取的图像压缩编码
许海霞
【期刊名称】《山东纺织经济》
【年(卷),期】2007(000)001
【摘要】本文提出了基于边缘提取的图像压缩编码算法.该算法针对具体情况,对仅需要知道图像边缘信息的图像首先采用canny算子进行边缘提取,然后对边缘提取后的图像再进行一维游程编码.实验结果表明,此算法具有更高的压缩率.
【总页数】2页(P87-88)
【作者】许海霞
【作者单位】潍坊学院信息与控制工程学院,山东潍坊,261061
【正文语种】中文
【中图分类】TN919.81
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2.基于小波与分形相结合的图像压缩编码 [J], 张晶晶;张爱华;纪海峰
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ISA 75.08.03-2001(R2007)
Draft Standard ISA-75.08.03-2001 (R2007)Face-to-Face Dimensions for Socket Weld-End and Screwed-End Globe-Style Control Valves (Classes 150, 300, 600, 900, 1500, and 2500)Approved DateISA-75.08.03-2001 (R2007)Face-to-Face Dimensions for Socket Weld-End and Screwed-End Globe-Style Control Valves (Classes 150, 300, 600, 900, 1500, and 2500)ISBN:Copyright © 2007 by ISA. All rights reserved. Not for resale. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic mechanical, photocopying, recording, or otherwise), without the prior written permission of the Publisher.ISA67 Alexander DriveP.O. Box 12277Research Triangle Park, North Carolina 27709- 3 - ISA-75.08.03-2001 (R2007)PrefaceThis preface, as well as all footnotes and annexes, is included for information purposes and is not part of ISA-75.08.03-2001 (R2007).This document has been prepared as part of the service of ISA towards a goal of uniformity in the field of instrumentation. To be of real value, this document should not be static but should be subject to periodic review. Toward this end, the Society welcomes all comments and criticisms and asks that they be addressed to the Secretary, Standards and Practices Board; ISA; 67 Alexander Drive; P. O. Box 12277; Research Triangle Park, NC 27709; Telephone (919) 549-8411; Fax (919) 549-8288; E-mail:standards@.The ISA Standards and Practices Department is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrumentation standards. The Department is further aware of the benefits to USA users of ISA standards of incorporating suitable references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavor to introduce SI-acceptable metric units in all new and revised standards, recommended practices, and technical reports to the greatest extent possible. Standard for Use of the International System of Units (SI): The Modern Metric System, published by the American Society for Testing & Materials as IEEE/ASTM SI 10-97, and future revisions, will be the reference guide for definitions, symbols, abbreviations, and conversion factors.It is the policy of ISA to encourage and welcome the participation of all concerned individuals and interests in the development of ISA standards, recommended practices, and technical reports. Participation in the ISA standards-making process by an individual in no way constitutes endorsement by the employer of that individual, of ISA, or of any of the standards, recommended practices, and technical reports that ISA develops.CAUTION — ISA ADHERES TO THE POLICY OF THE AMERICAN NATIONAL STANDARDS INSTITUTE WITH REGARD TO PATENTS. IF ISA IS INFORMED OF AN EXISTING PATENT THAT IS REQUIRED FOR USE OF THE DOCUMENT, IT WILL REQUIRE THE OWNER OF THE PATENT TO EITHER GRANT A ROYALTY-FREE LICENSE FOR USE OF THE PATENT BY USERS COMPLYING WITH THE DOCUMENT OR A LICENSE ON REASONABLE TERMS AND CONDITIONS THAT ARE FREE FROM UNFAIR DISCRIMINATION.EVEN IF ISA IS UNAWARE OF ANY PATENT COVERING THIS DOCUMENT, THE USER IS CAUTIONED THAT IMPLEMENTATION OF THE DOCUMENT MAY REQUIRE USE OF TECHNIQUES, PROCESSES, OR MATERIALS COVERED BY PATENT RIGHTS. ISA TAKES NO POSITION ON THE EXISTENCE OR VALIDITY OF ANY PATENT RIGHTS THAT MAY BE INVOLVED IN IMPLEMENTING THE DOCUMENT. ISA IS NOT RESPONSIBLE FOR IDENTIFYING ALL PATENTS THAT MAY REQUIRE A LICENSE BEFORE IMPLEMENTATION OF THE DOCUMENT OR FOR INVESTIGATING THE VALIDITY OR SCOPE OF ANY PATENTS BROUGHT TO ITS ATTENTION. THE USER SHOULD CAREFULLY INVESTIGATE RELEVANT PATENTS BEFORE USING THE DOCUMENT FOR THE USER’S INTENDED APPLICATION.HOWEVER, ISA ASKS THAT ANYONE REVIEWING THIS DOCUMENT WHO IS AWARE OF ANY PATENTS THAT MAY IMPACT IMPLEMENTATION OF THE DOCUMENT NOTIFY THE ISA STANDARDS AND PRACTICES DEPARTMENT OF THE PATENT AND ITS OWNER. ADDITIONALLY, THE USE OF THIS DOCUMENT MAY INVOLVE HAZARDOUS MATERIALS, OPERATIONS OR EQUIPMENT. THE DOCUMENT CANNOT ANTICIPATE ALL POSSIBLE APPLICATIONS OR ADDRESS ALL POSSIBLE SAFETY ISSUES ASSOCIATED WITH USE IN HAZARDOUS CONDITIONS. THE USER OF THIS DOCUMENT MUST EXERCISE SOUNDISA-75.08.03-2001 (R2007) - 4 -PROFESSIONAL JUDGMENT CONCERNING ITS USE AND APPLICABILITY UNDER THE USER’S PARTICULAR CIRCUMSTANCES. THE USER MUST ALSO CONSIDER THE APPLICABILITY OF ANY GOVERNMENTAL REGULATORY LIMITATIONS AND ESTABLISHED SAFETY AND HEALTH PRACTICES BEFORE IMPLEMENTING THIS DOCUMENT.THE USER OF THIS DOCUMENT SHOULD BE AWARE THAT THIS DOCUMENT MAY BE IMPACTED BY ELECTRONIC SECURITY ISSUES. THE COMMITTEE HAS NOT YET ADDRESSED THE POTENTIAL ISSUES IN THIS VERSION.The following people served as members of ISA Subcommittee SP75.08 and approvedANSI/ISA-75.08.03-2001:NAME COMPANY W. Weidman, Managing Director Parsons Energy & Chemicals GroupH. Baumann H B Services Partners LLCG. Borden ConsultantR. Brodin Fisher Controls International, Inc.F. Cain Flowserve Corp.R. Chown Otec Process Systems, Inc.B. Hatton DeZurik Division UnitJ. Reed NorrisealH. Sonderegger Anvil International, Inc.The following people served as members of ISA Committee SP75 and approvedANSI/ISA-75.08.03-2001:NAME COMPANY W. Weidman, Managing Director Parsons Energy & Chemicals GroupD. Buchanan, Chairman Union Carbide Corp.A. Abromaitis Red Valve Co., Inc.H. Backinger ConsultantG. Barb ConsultantH. Baumann H B Services Partners LLCJ. Beall Eastman Chemical Co.W. Black Cashco, Inc.W. Blackwell Industrial ValveH. Boger Masoneilan DresserG. Borden ConsultantS. Boyle Metso Automation USA, Inc.R. Brodin Fisher Controls International, Inc.F. Cain Flowserve Corp.A. Engels Praxair, Inc.H. Fuller Valvcon Corp.J. George Richards IndustriesL. Griffith ConsultantD. Grunenberg Richards IndustriesJ. Jamison Bantrel, Inc.R. Jeanes TXU ElectricJ. Kersh M W Kellogg Co.C. Langford Cullen G. Langford, Inc.W. Lestan Dresser Valve DivisionA. Libke DeZurik Valve Co.R. Louviere Services Unlimited- 5 - ISA-75.08.03-2001 (R2007) J. McCaskill Power ChokesA. McCauley Chagrin Valley Controls, Inc.R. McEver Emerson Valve AutomationH. Miller Control Components, Inc.T. Molloy CMES, Inc.L. Ormanoski Frick Co.J. Ozol Northern States PowerW. Rahmeyer Utah State UniversityJ. Reed NorrisealK. Schoonover Con-Tek Valves, Inc.A. Shea DeZurik/Copes-VulcanE. Skovgaard Leslie Controls, Inc.H. Sonderegger Anvil International, Inc.ANSI/ISA-75.08.03-2001 was approved for publication by the ISA Standards and Practices Board on 04 April 2001.NAME COMPANY M. Zielinski Fisher-Rosemount Systems, Inc.D. Bishop ConsultantM. Cohen ConsultantM. Coppler Ametek, Inc.B. Dumortier Schneider ElectricW. Holland Southern CompanyE. Icayan Advanced Control & Engineering SolutionsA. Iverson Ivy OptiksR. Jones Dow Chemical Co.V. Maggioli Feltronics Corp.T. McAvinew Merrick & Co.A. McCauley, Jr. Chagrin Valley Controls, Inc.G. McFarland Westinghouse Process Control Inc.D. Rapley Rapley Consulting Inc.R. Reimer Rockwell AutomationJ. Rennie Factory Mutual Research Corp.H. Sasajima Yamatake Corp.I. Verhappen Syncrude Canada Ltd.R. Webb Power EngineersW. Weidman Parsons Energy & Chemicals GroupJ. Weiss EPRIM. Widmeyer EG&G Defense MaterialsR. Wiegle CANUS Corp.C. Williams Eastman Kodak Co.G. Wood Graeme Wood ConsultingThe following people served as members of ISA Subcommittee SP75.08 and reaffirmedISA-75.08.03-2001 (R2007):NAME COMPANY W. Weidman, Chair Worley ParsonsH. Baumann ConsultantG. Borden ConsultantF. Cain Flowserve CorporationR. Chown Otec Process Systems Inc.R. Duimstra Fisher Controls International Inc.ISA-75.08.03-2001 (R2007) - 6 -V. Mezzano Fluor CorporationJ. Reed ConsultantJ. Young Dow Chemical CompanyThe following people served as members of ISA Committee SP75 and reaffirmedISA-75.08.03-2001 (R2007):NAME COMPANY J. Young, Chair Dow Chemical CompanyW. Weidman, Managing Director Worley ParsonsH. Backinger ConsultantH. Baumann ConsultantJ. Beall Emerson Process ManagementW. Black Curtiss-Wright Flow Control CorporationH. Boger Masoneilan DresserG. Borden ConsultantS. Boyle Metso Automation USA Inc.J. Broyles Enbridge Pipelines Inc.F. Cain Flowserve CorporationW. Cohen KBRR. Duimstra Fisher Controls International Inc.J. Faramarzi Control Components Inc.J. George Richards IndustriesH. Hoffmann Samson AGJ. Jamison OPTI Canada Inc.R. Jeanes TXU ElectricC. Langford Cullen G Langford Inc.G. Liu Syncrude Canada Ltd.J. McCaskill Power ChokesA. McCauley Chagrin Valley Controls Inc.R. McEver ConsultantV. Mezzano Fluor CorporationT. Molloy CMES Inc.L. Ormanoski York Process SystemsJ. Ozol NMC Prairie Island Nuclear PlantW. Rahmeyer Utah State UniversityJ. Reed ConsultantE. Skovgaard Control Valve SolutionsThis standard was approved for reaffirmation by the ISA Standards and Practices Board on__________ 2007:NAME COMPANY T. McAvinew, Vice President Jacobs Engineering GroupM. Coppler Ametek Inc.B. Dumortier Schneider ElectricD. Dunn Aramco Services CompanyW. Holland ConsultantE. Icayan ACES Inc.J. Jamison Husky Energy Inc.K. Lindner Endress+Hauser Process Solutions AGV. Maggioli Feltronics CorporationA. McCauley Chagrin Valley Controls Inc.G. McFarland Emerson Process Mgmt Power & Water Solutions- 7 - ISA-75.08.03-2001 (R2007) R. Reimer Rockwell AutomationN. Sands E I du PontH. Sasajima Yamatake CorporationT. Schnaare Rosemount Inc.J. Tatera Tatera & Associates Inc.I. Verhappen MTL Instrument GroupR. Webb Robert C Webb PEW. Weidman Worley ParsonsJ. Weiss Applied Control Solutions LLCM. Widmeyer ConsultantM. Zielinski Emerson Process ManagementThis page intentionally left blank.- 9 - ISA-75.08.03-2001 (R2007)CONTENTS1 Scope (11)2 Purpose (11)3 Definitions (11)4 Dimensional data (11)5 References (12)Annex A (informative) — Dimensions for metrically sized valves (15)This page intentionally left blank.- 11 - ISA-75.08.03-2001 (R2007) 1 ScopeThis standard applies to socket weld-end globe-style control valves, sizes 1/2 inch (15 mm) through4 inches (100 mm), and screwed-end globe-style control valves, sizes 1/2 inch (15 mm) through2 1/2 inches (65 mm), having top, top and bottom, port, or cage guiding.2 Purpose2.1 The purpose of this standard is to aid users in their piping designs by providing Classes 150 through 2500 socket weld-end control valve dimensions and Classes 150 through 600 screwed-end control dimensions without giving special consideration to the equipment manufacturer to be used.2.2 The short-long dimensions provided in Tables 1 and 2 clarify 2.1 by consolidating the diversity of existing manufacturers' lengths into two sets of dimensions for each size valve. Before using either the short or long dimensions, the piping designer should confirm with the selected valve manufacturer which dimension is correct for the valve(s) being supplied.3 DefinitionsFor definitions of terms used in this standard, see ANSI/ISA-75.05.01-2000 (R2005), Control Valve Terminology.4 Dimensional data4.1 Face-to-face dimensions for socket weld-end globe-style control valves are listed in Table 1.Table 1 — Face-to-face dimensions for socket weld-endglobe-style control valvesPN 20, 50, & 100 (Classes 150, 300, & 600)PN 150 & 250(Classes 900 & 1500)PN 420(Class 2500)Nominal Valve Dimension “A” Dimension “A” Dimension “A”Size mm inches mm inches mm inchesTolerance mm inches Short Long Short Long Short Long Short Long Short Long Short Long mm inches15 1/2 170 206 6.69 8.12 178 279 7.00 11.00 216 318 8.50 12.50 ±6.4 ±0.2520 3/4 170 210 6.69 8.25 178 279 7.00 11.00 216 318 8.50 12.50 ±6.4 ±0.2525 1 197 210 7.75 8.25 178 279 7.00 11.00 216 318 8.50 12.50 ±6.4 ±0.2540 1-1/2 235 251 9.25 9.88 235 330 9.25 13.00 260 381 10.25 15.00 ±6.4 ±0.2550 2 267 286 10.50 11.25 292 375 11.50 14.75 324 400 12.75 15.75 ±6.4 ±0.2565 2-1/2 292 311 11.5012.25 292 11.50 324 12.75 ±6.4 ±0.2580 3 318 337 12.50 13.25 318 533 12.50 21.00 381 660 15.00 26.00 ±6.4 ±0.25100 4 368 394 14.50 15.50 368 530 14.50 20.88 406 737 16.00 29.00 ±6.4 ±0.25ISA-75.08.03-2001 (R2007) - 12 -4.2 Face-to-face dimensions for screwed-end globe-style control valves are listed in Table 2.Table 2 — Face-to-face dimensions for screwed-end globe-style control valvesNominal Valve Size PN 20, 50, & 100(Classes 150, 300, & 600)“A”DimensionToleranceinchesmmmm inches Short Long Short Long mm inches±0.06215 1/2 165 206 6.50 8.12 ±1.6±0.06220 3/4 165 210 6.50 8.25 ±1.6±0.062±1.68.2525 1 197 210 7.7540 1-1/2 235 251 9.25 9.88 ±1.6 ±0.06250 2 267 286±1.6±0.06210.5011.2565 2-1/2 292 311 11.50 12.25 ±1.6 ±0.0625 ReferencesAmerican Society of Mechanical Engineers (ASME)ASME B16.11-2005 Forged Fittings, Socket-Welding and ThreadedASMEfrom:AvailableAvenueParkThreeNew York, NY 10016-5990800-843-2763Tel:- 13 - ISA-75.08.03-2001 (R2007) ISAANSI/ISA-75.05.01-2000 Control Valve Terminology(R2005)ISAfrom:AvailableDrive67Alexander12277BoxPOResearch Triangle Park, NC 27709919-549-8411Tel:Manufacturers Standardization Society of the Valve & Fittings Industry (MSS)SP-84-1990 Valves - Socket Welding and Threaded EndsMSSfrom:Available127 Park Street, NEVienna,22180-4602VA703-281-6613Tel:This page intentionally left blank.- 15 - ISA-75.08.03-2001 (R2007) Annex A (informative) — Dimensions for metrically sized valvesThis annex is not part of ISA-75.08.03-2001 (R2007), but is included to facilitate its use.Dimensions for metrically sized valves are nominal conversions that are conventionally used in the Manufacturers Standardization Society (MSS) of the Valve and Fitting Industry's PublicationMSS-SP86-2002, and in International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) documents.This page intentionally left blank.Developing and promulgating sound consensus standards, recommended practices, and technical reports is one of ISA’s primary goals. To achieve this goal the Standards and Practices Department relies on the technical expertise and efforts of volunteer committee members, chairmen and reviewers. ISA is an American National Standards Institute (ANSI) accredited organization. ISA administers United States Technical Advisory Groups (USTAGs) and provides secretariat support for International Electrotechnical Commission (IEC) and International Organization for Standardization (ISO) committees that develop process measurement and control standards. To obtain additional information on the Society’s standards program, please write:ISADepartmentAttn:StandardsDriveAlexander6712277P.O.BoxResearch Triangle Park, NC 27709ISBN:。
基于Tsai算法的光电系统畸变图像的标定和校正
基于Tsai算法的光电系统畸变图像的标定和校正聂亮;李育蒙【期刊名称】《价值工程》【年(卷),期】2016(035)007【摘要】畸变普遍存在于光电系统中,影响光电系统的成像。
为了解决这个问题,研究Tsai模型,实现Tsai算法的标定,并利用线性变换方法或者透视变换矩阵求解摄像机参数,再用之前得到的结果带入非线性方程,解得一个估计值,然后用估计值作为初始值,根据特定的算法来迭代,直达满足条件为止,求解其他参数。
并评估算法的精度。
%Distortion widely exists in optical system, it affects optical system imaging. In order to solve this problem, TASI model are studied to achieve calibration of Tsai algorithm, and the method of linear transformation or perspective transformation matrix is used to solve the camera intrinsic parameters. And then, the results obtained before are subsitituted into non linear equation to get an estimate value and take the estimate value as initial value to carry out the iteration by the specific algorithm until meet the conditions and then solve other parameters and evaluate the algorithm's accuracy.【总页数】2页(P180-181)【作者】聂亮;李育蒙【作者单位】西安工业大学光电工程学院,西安710021;西安工业大学光电工程学院,西安710021【正文语种】中文【中图分类】TP301.6【相关文献】1.基于tsai方法的多项畸变模型单目摄像机标定 [J], 牛苗苗;孙灿;熊海涵2.基于CORDIC算法的全景图像畸变场校正算法 [J], 张辉;李科杰;张振海3.基于标定的CCD图像畸变校正方法研究 [J], 徐芳;刘晶红;王宣4.一种基于拼接算法的鱼眼图像畸变校正方法 [J], 何志东; 张建伟; 梁斌斌5.基于映射适应性卷积和等距投影的鱼眼图像畸变校正算法 [J], 马辉;朱琳;曾静因版权原因,仅展示原文概要,查看原文内容请购买。
基于小波变换的亚像素计算机视觉检测算法
基于小波变换的亚像素计算机视觉检测算法申宗林;李智成;李彩红;梁皓嶙;李锋【摘要】计算机视觉检测作为一种非接触检测手段在工业制造中逐步兴起,传统像素级精度己经不能满足实际检测需求.提出利用小波变换函数改进最小二乘回归直线拟合法方法,先根据一次、二次微分找出其突变点,一次微分的极大值点对应二次微分的零交叉点和平滑后信号的拐点,再结合小波变换模型通过减小尺度的方式精确定位成像边缘,以达到亚像素精度需求.并基于C++编写尺寸检测系统,可以检测大小、完整性等,并找出缺陷产品,联动控制报警机制,从而降低人工视觉检测的复杂度.仿真实验证明,新算法精度可以达到亚像素级别,测试结果稳定,误差很小,具有良好的通用性.%Computer vision detection, as a kind of non-contact detection methods,is gradually rising in the industrial manufacture. Traditional pixel level accuracy has been unable to meet the needs of the actual detection. This paper puts forward a improved least squares regression linear fitting model, using wavelet transform function, according to the first order and second order differential, finding the mutation point,the maximum point of the first order differential and corresponding to the zero crossing point of the second differential and inflection point of the signal after smoothing,and combining with wavelet transform model,by the way of reducing scale,to precisely locate the edge of imaging in order to achieve sub-pixel accuracy requirements. And on the basis of C++, size detection system is programmed, which can be used to detect the size and integrity, so as to detect defective product, and coordinately control the alarming mechanism to reduce the complexity of artificial vision detection. Thesimulation results show that the ac-curacy of the new algorithm can reach sub-pixel level with stable measure result,less error,and well versa-tility.【期刊名称】《微处理机》【年(卷),期】2017(038)004【总页数】4页(P64-66,86)【关键词】计算机视觉;亚像素;小波变换;检测系统;最小二乘法;拟合算法【作者】申宗林;李智成;李彩红;梁皓嶙;李锋【作者单位】广东交通职业技术学院,广州510650;广东交通职业技术学院,广州510650;广东交通职业技术学院,广州510650;广东交通职业技术学院,广州510650;广东交通职业技术学院,广州510650【正文语种】中文【中图分类】TP393计算机视觉检测作为一种非接触检测手段在智能制造中逐步兴起。
2007测量技术与智能仪器国际会议(ISMTII2007)
2007测量技术与智能仪器国际会议(ISMTII2007)
佚名
【期刊名称】《纳米技术与精密工程》
【年(卷),期】2006(4)4
【总页数】1页(P274-274)
【关键词】智能仪器;智能化仪器;ISMTII2007;会议;测量技术;测定技术
【正文语种】中文
【中图分类】TB
【相关文献】
1.维纳与智能测量的新进展--第七届国际测量技术与智能仪器研讨会侧记 [J], 张国雄
2.IEEE仪器与测量技术国际会议简报 [J],
3.《国外电子测量技术》2008电子测量仪器用户应用情况调查暨2007年度特殊贡献产品评选活动成功落下帷幕 [J],
4.2007测量技术与智能仪器国际会议(ISMTII 2007) [J],
5.智能传感器技术与虚拟仪器技术在测量仪器中的完美结合 [J], 王艳萍;马冲因版权原因,仅展示原文概要,查看原文内容请购买。
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DOI:10.1017.S0003055407070153 Solidary Groups,Informal Accountability,and Local Public Goods Provision in Rural ChinaLIL Y L.TSAI Massachusetts Institute of TechnologyW hy would government officials in authoritarian and transitional systems where formal demo-cratic and bureaucratic institutions of accountability are often weak ever provide more thanthe minimum level of public goods needed to maintain social stability?Findings from a unique combination of in-depth case study research and an original survey of316villages in rural China indicate that even when formal accountability is weak,local officials can be subject to unofficial rules and norms that establish and enforce their public obligations.These informal institutions of accountability can be provided by encompassing and embedding solidary groups.Villages where these types of groups exist are more likely to have better local governmental public goods provision than villages without these solidary groups,all other things being equal.F ormal institutions of accountability are oftenweak in developing countries(Bardhan2002).States in these countries often lack strong bu-reaucratic institutions for controlling corruption and making sure that lower level officials are doing their jobs.Democratic institutions such as elections that al-low citizens to hold local officials accountable may be weak and unreliable or even nonexistent.Yet in these countries some local officials still perform bet-ter than others.Under these conditions,how do cit-izens make government officials organize and fund the public goods and services that they want and need?This question is important for practical,political,and theoretical reasons.Practically speaking,people every-where need their governments to provide roads,educa-tion,clean water,and other public goods and services that they have trouble producing on their own.The provision of these basic public goods and services mat-ters deeply for the quality of people’s lives everywhere. Politically,how effectively governments provide these goods and services has an enormous impact on their legitimacy.Many of the developing countries in Asia, Africa,and Latin America that struggle the most to provide basic public goods are also the countries strug-gling the most to build effective states and maintain regime stability.This question is also important from a theoreti-cal perspective.Existing explanations of governmen-Lily L.Tsai is Assistant Professor,Department of Political Science, Massachusetts Institute of Technology,77Massachusetts Avenue, E53-425,Cambridge,MA02139(l tsai@).I am indebted to Elizabeth Perry,Grzegorz Ekiert,Robert Putnam,and Theda Skocpol for their invaluable advice and sup-port at various stages of the project.Earlier versions of this paper benefited greatly from comments provided by Edward Young,Adam Berinsky,Melani Cammett,Andrea Campbell,Mary Gallagher,John Gerring,Frances Hagopian,David Laitin,Chappell Lawson,De-vra Moehler,Daniel Posner,Susan Rose-Ackerman,James Scott, Tianjian Shi,participants of the World Bank Seminar Series on the Political Economy of Governance Reform,the China Research Sem-inar at Oxford University,the Democracy,Governance,and Identity Workshop at the University of Michigan,and six anonymous review-ers.Nathan Cisneros and William Tilden provided valuable editorial assistance.tal performance and variation in governmental public goods provision have focused primarily on the role of strong democratic and bureaucratic institutions.The-ories of institutional design argue that the key to good government is providing formal democratic in-stitutions and devolving power to local levels so that citizens can monitor and sanction officials effectively (e.g.,Dahl1971;O’Donnell1996;Rose-Ackerman 2005;Seabright1996).Theories of civil society and social capital argue that voluntary associations,interest groups,and associational activity can improve govern-mental performance in democratic systems(Boix and Posner1998;Edwards and Foley1998;Ehrenberg1999; Putnam1993).In consolidated democracies where for-mal institutions ensure the incorporation of citizen demands into the policymaking process,autonomous associations and interest groups can help citizens voice their demands more effectively.Other studies suggest that democratic institutions may not be necessary for good governmental public goods provision,but these arguments still rely on the existence of effective and coherent formal state institutions.Peter Evans(1995), for example,argues that developmental states differ from predatory states in two ways.First,developmen-tal states generate bureaucracies with corporate coher-ence and strong bureaucratic institutions of internal accountability.Second,developmental states are“em-bedded”in the sense that the state forges informal connections with powerful business interests.Corpo-rate solidarity enables the state to resist sliding into patron–client relationships with societal interests.Wai Fung Lam(1997)finds that irrigation governance in Taiwan is effective because strong community norms work in tandem with formal bureaucratic admini-stration.But what about governmental public goods pro-vision in countries which lack strong democratic and bureaucratic institutions of accountability?Pub-lic goods provision is often much more of a prob-lem,both practically and politically,in developing countries with nondemocratic or transitional systems. How do we account for variation in local governmen-tal performance and public goods provision in these systems?355A MODEL OF INFORMAL GOVERNMENTAL ACCOUNTABILITYPublic goods provision is always associated with a col-lective action problem.Everyone has an incentive to free ride on the efforts of everyone else.Most mod-els of public goods provision focus on the collective action problem.Alesina,Baqir,and Easterly(1999) argue that public goods provision is poorer in ethni-cally diverse areas because different ethnic groups have different preferences or tastes for particular public services,thus making any collective decision difficult. Elinor Ostrom(1990)finds that well-designed commu-nity social institutions can help overcome obstacles to collective action.Robert Putnam(1993,2000)argues that dense social networks and norms of trust can make people more likely to cooperate with each other.But these models do not explicitly address the ad-ditional problem associated with governmental public goods provision—–the provision of public goods and ser-vices by the government—–in systems with weak formal democratic and bureaucratic institutions:the problem of accountability.In these systems overcoming the col-lective action problem among citizens is not sufficient to guarantee that the government will provide public goods responsibly.Once public funds are in the hands of government officials,how can citizens make sure that officials use these funds to pave roads,build schools, and invest in local public projects?How can citizens have leverage over government officials in the absence of strong formal institutions?I propose a model of informal governmental ac-countability.Even when formal governmental account-ability is weak,local officials may still have a strong incentive to provide public goods when citizens award them moral standing for doing so.Like other types of prestige,moral standing is“the esteem,respect,or ap-proval that is granted by an individual or a collectivity for performances or qualities they consider above the average”(Goode1979,7).In the case of moral stand-ing,esteem or respect is granted for above-average per-formance of actions considered morally good.Those specific standards and actions vary.Moral standing can be a powerful incentive.It not only makes people feel good about themselves,but also it can translate into economic and social advancement.Local officials with higher moral standing may alsofind it easier to elicit citizen compliance with state policies.Moral standing can be an invaluable resource for accomplishing a va-riety of political,social,and economic objectives. When are people more likely to reward officials with moral standing for providing public goods and ser-vices?First,citizens and officials must share a set of criteria for moral behavior.At minimum,these crite-ria include the principle that contributing to the good of the group deserves moral approval.Without this criterion,the group would not last very long.Second, opportunities must exist for publicizing behavior that meets these shared standards.The more citizens be-lieve that officials really do share the group’s obliga-tions and standards and the more citizens know about whether officials actually behave according to these standards,the more likely they are to award officials moral standing.Like all forms of prestige,moral stand-ing is dependent on the“verbal information dissemi-nated in the community relating news and approval of an individual’s activities”(Riches1984,235).I argue that people are more likely to use moral standing to reward local officials for good public goods provision when there are local solidary groups—–groups based on shared moral obligations as well as shared interests.To provide informal institutions that enable citizens to hold local officials accountable for public goods provision,solidary groups must have two par-ticular structural characteristics.First,they must be encompassing,or open to everyone under the local gov-ernment’s jurisdiction.In localities with encompassing solidary groups,social boundaries overlap with polit-ical boundaries.Examples of encompassing solidary groups might include citizens’groups that monitor town planning decisions in the United States,parish churches in nineteenth-century England(Morris2001), and village harambees or self-help organizations in Kenya(Miguel1999).Second,solidary groups must be embedding in that they incorporate local officials into the group as members.Not all encompassing sol-idary groups are embedding.English parish churches are often embedding because local officials are likely to attend church services and identify as members of the congregation.In contrast citizen watchdog orga-nizations in the United States,which are designed to monitor and challenge government,may encompass a particular town or municipality but are unlikely to embed officials into the group as members.In localities with encompassing and embedding sol-idary groups,citizens and officials are more likely to share a common set of ethical standards and moral obligations.Members of clans,churches,fraternal orga-nizations,and other solidary groups have strong obliga-tions to the collective.In solidary groups members are judged according to the group’s standards of what con-stitutes a good person and a good member.Members of church congregations thus feel compelled to contribute something when the donation basket is passed around. Members of clans are expected to and commended for siding with fellow members in disputes with out-siders.Group activities and dense social networks also provide ample opportunities for individual members to publicize their exemplary behavior.For moral standing to be conferred on an individual,both the individual’s actions and acceptance of shared standards have to be “common knowledge”(Chwe2003).Churches ask for volunteers to help with church activities immediately after services when the congregation is still assembled. In rural China lineage members are expected to attend group rituals of respect for shared ancestors.These collective gatherings help publicize who is deserving of moral standing in the community.When the boundaries of a solidary group overlap with the administrative boundaries of the local gov-ernment,embedded officials have a strong social obli-gation to contribute to the good of the group.Because in this case the group and the public are the same, officials in localities with encompassing and embedding356solidary groups can earn moral standing for providing public goods(and suffer severe social sanctions for not doing so).Officials in localities with encompassing and embedding solidary groups thus have an extra incen-tive to provide public goods and services to their juris-diction.RESEARCH DESIGNContemporary rural China provides an ideal setting to examine the factors that affect the quality of lo-cal governance because of the tremendous variation in the performance of village governments.1As in many countries,the Chinese state has decentralized primary responsibility for the provision of basic public goods and services to local governments.During the period of this study(1999–2002),village government officials in China were expected to fund and organize the construction of all roads,drainage systems,irri-gation works,primary school facilities,and sanitation and trash disposal within the village primarily through resources available within the village(see Wong1997), although this may change with recent rural tax reforms andfiscal recentralization.Some village governments provide their citizens with outstanding public goods and services;other village governments provide noth-ing at all.Examining variation in governmental provi-sion of public goods within the same country also allows us to hold constant macro-conditions such as political ideology,national policy,and regime type while partic-ular factors that existing theories suggest as important for governance and public goods provision are allowed to vary.To study this problem,in2001,I surveyed316villages and carried out a set of detailed case studies in rural China.After two months of preliminary research in seven different provinces across the country and eight months of in-depthfieldwork in one set of villages in the southern province of Fujian,I designed a survey to ex-amine the impact of formal and informal institutions on village governmental public goods provision.The four provinces for the survey—–Shanxi,Hebei,Jiangxi,and Fujian—–were chosen to reflect differences in levels of economic development as well as regional differences between north and south China in terrain,institutional history,and social organization.Shanxi and Hebei are neighboring provinces in the north,but Shanxi is in the interior and less developed.Jiangxi and Fujian are neighboring provinces in the south,but Jiangxi is in the interior and less developed.Within each province,two counties were selected to vary in model county status for village democratic reforms(model counties employ more administrative resources and pressure to imple-ment village democratic reforms)but to have similar economic and geographic characteristics.The original 1Although the central government officially refers to village gov-ernments as“self-governing organizations,”village governments are widely considered part of the state apparatus by higher level officials, village officials,and citizens themselves.Village governments collect state taxes,enforce state directives such as the birth control policy, and provide village public goods and services.rationale for this selection strategy was to be able to use model county status as an instrument for identi-fying the impact of village democratic reforms which may be endogenous to the model,but in this paper, the implementation of village democratic reforms is included as a control rather than studied as the main variable of interest.To conduct this survey,I visited each of the eight counties and presented references from Chinese aca-demics and researchers to the county government.Af-ter obtaining permission to carry out research in the county,I selected eight townships through a random stratified sampling procedure(with stratification by of-ficial income per capita).A county official then accom-panied me and my research team of Chinese university student enumerators to each of the townships where I then selectedfive villages in each township through a similar procedure(again with stratification by official income per capita).In townships with fewer thanfive villages,all the villages were surveyed.Townships with less thanfive villages account for the sample of316 villages(as opposed to320villages).Each township government then contacted the village governments in their jurisdiction to notify them that a couple of stu-dents would be visiting them to do academic research. The combination of official approval from the local government and our obvious status as students helped secure the willing cooperation of our respondents.In each of the sampled villages,enumerators interviewed one or,in most cases,more than one village official in order tofill out village-level survey questionnaires about village conditions.In all cases,enumerators also used village documents to corroborate interviewee re-sponses.Survey respondents showed a high level of frankness about even potentially sensitive topics such as economic indicators and the implementation of vil-lage democratic reforms.This level of comfort can be largely credited to the highly skilled administration of the survey by the student enumerators,most of whom had grown up in villages themselves and were pursuing degrees in agricultural economics,rural sociology,and related disciplines.2THE IMPORTANCE OF SOLIDARY GROUPS Before we go on to thefindings from analysis of the quantitative data,this section draws on data from in-depth case studies to illustrate how encompassing and embedding solidary groups,such as village temples and village-wide lineages,can provide incentives for local officials to provide public goods and services.When solidary groups are both encompassing and embed-ding,officials who provide public services to the local administrative unit(such as a ward,a town,or a village) 2When asked,for example,for the village’s“official”income per capita and“real”income per capita,only14%,in fact,reported the samefigures.Village officials were also comfortable report-ing interference—–even by themselves personally—–in the preelection process,even though such interference goes against official state regulations,as well as failure on their part to implement officially required procedures for voting and the operation of villagers’repre-sentative assemblies.357are also fulfilling collective obligations to the solidary plying with group norms of collective re-sponsibility enables them to acquire moral standing among all their constituents since,in this case,local administrative boundaries coincide with social bound-aries.Imagine the mayor of a small town in the United States with only one church.Church suppers and pic-nics are a major part of the town’s social life,and the church hall might in fact be the only place that people can rent for social gatherings.Even if not everyone goes to church regularly,everyone sees the church as representative of the town community.In this kind of small town,if the mayor does something exemplary like bringing down the crime rate by strengthening the police force,the minister might very well mention his good work in front of the congregation during his Sunday sermon.Getting commended by the minister during services can give the mayor a measure of moral and social standing in addition to whatever he might already possess as a public official or social elite.The mayor benefits personally from this increased stand-ing.People stop him on the street to praise his work, storekeepers treat him with more deference,the bank is willing to give him a bigger mortgage,and his chil-dren receive more attention at school.Increased moral standing may also make his mayoral tasks easier to carry out.When he tries to implement a difficult state policy—–a new requirement,for example,that students of a different ethnic group be bused into the town school—–additional standing can help him elicit compli-ance from his constituents.Moral standing can make citizens more likely to trust that the mayor is right and defer to his judgment on whether the policy should be implemented.A local official with sufficient moral standing may also be more able to persuade leaders of the community solidary group to use their own moral authority to win over particularly stubborn opponents of the policy.Solidary Groups in Rural ChinaVillage Temples.In the Chinese context,an analo-gous example would be the case of West Gate,a vil-lage of about3900people in the coastal province of Fujian.Overfive months in2000and2001,I visited West Gate weekly to talk with villagers and observe village politics.West Gate’s equivalent of our hypo-thetical town church is the village temple community council.The temple council organizes a multitude of religious and community activities for the village.As with temple groups in many other villages,West Gate’s temple council evolved out of an informal group of villagers who decided,after the start of liberalization in the late1970s,to try to rebuild village temples de-stroyed during the Cultural Revolution.Unlike larger, official Buddhist temples,these small village temples are a part of Chinese folk religion and house deities that people consider the guardians of their specific vil-lage.During festival holidays,village temples organize parades,opera performances,and other ritual festiv-ities.Villagers have clear obligations to contribute to and participate in these activities because these col-lective activities represent group tributes to the vil-lage’s guardian deities.Village residents are expected to make donations to help fund these activities.The names of donors and the amount they donated are posted publicly on the temple wall.Village temples are an important symbol of the village community.They provide strong institutions enforcing each member’s responsibility to contribute to the collective good and numerous opportunities for publicizing whether mem-bers have fulfilled their responsibilities.West Gate’s12village officials—–who,as with most village officials in China,come from within the village—–try hard to be upstanding members of the village temple group.Party secretary Sun was one of the two top donors to a recent temple reconstruction project,having donated2,000yuan or about the same as the national annual per capita rural income.In1996 when the district government directed all its villages to set up senior citizens’associations,West Gate’s officials agreed to call the temple community council(which had been operating since the1980s)the village senior citizens’association,thereby giving it an extra layer of legitimacy.Because the Communist Party discourages “superstitious”activities,village officials refrain from taking leadership positions in the temple,but as or-dinary members of the temple group,they diligently fulfill their obligations to contribute to the good of the group.These obligations make West Gate’s officials very responsive to citizen demands for public goods and ser-vices.In exchange,the temple gives the village officials a good name or,as the temple council head notes,“half of the spotlight.”Council members also help officials mobilize villagers to attend meetings convened by the village government,convince villagers to give rights-of-way for the construction of a public drainage channel, and monitor the state ban onfirecrackers during festi-vals.The temple community council in West Gate has a positive effect on local governmental public goods pro-vision because it is both encompassing and embedding. If it were not encompassing,officials would only be able to gain moral standing among some of the villagers.If it were not embedding,officials would not be able to gain any moral standing at all.The moral standing conferred by the temple community council gives an incentive for officials to provide public services,which formal state institutions do not provide.The importance of having both structural character-istics becomes even clearer when we compare village temples to the other types of solidary groups most com-mon in rural China—–village churches and lineages. Village Churches.The necessity of embedding local officials is clear if we compare temple groups like the one in West Gate to village churches.Extensive case study and interview data indicated that village temple groups typically embed village officials in their activ-ities,but village churches do not.The state permits Catholic and Protestant churches,but in contrast to its358tolerance of village folk temples,it considers churches to have high subversive potential and regulates them closely.Party members are thus prohibited from partic-ipating in church activities.Unlike village temples that developed indigenously,are inherently limited to the immediate locality overseen by the village guardian deity,and have a history of reinforcing the authority of the state,3Christian churches were started in the nineteenth century by missionaries aligned closely with foreign governments seeking to open China to trade by setting up areas of extraterritoriality and weaken-ing the state(Esherick1987;Latourette1929;Madsen 1998).The state thus not only associates Christianity with threats to its sovereignty but with events like the Taiping Rebellion in which Christianity provided the basis for mobilizing vast numbers of people across localities against the state(Spence1996).The state therefore requires all churches to be registered with the state Religious Affairs Bureau and tries hard to limit the scope of a church to the local community. The example of South Bend,a village located in the northern province of Hebei,illustrates how village churches fail to have the same positive impact on vil-lage governmental public goods provision that village temples do.South Bend’s church is easily the grandest building for miles.Mass is held daily when the state-authorized priest is in town and weekly when he is traveling around the county serving the eight other state-registered congregations.Just about everyone in the village identifies himself or herself as Christian, and at any given service about one-third of the village is in attendance.A church management committee of four male villagers appointed by the priest oversees the maintenance of the church building,materials for church activities and services,and donations from the congregation,which total about three thousand yuan per year(about$375,U.S.),an amount that exceeds the tax revenue the village government is able to extract. The Party secretary of South Bend says that he be-lieves in God but calls himself a bad disciple because he is a Party member and Party members are not allowed to believe in religion.He complains bitterly about his lack of authority among villagers whom he says do not trust him because he never goes to church.Instead, he says,the church management committee makes all the important decisions in the village.South Bend’s village Party secretary is unable to benefit from the moral standing that the church can confer because the state does not allow him to participate as a member. Relative to the village officials in West Gate,South Bend’s Party secretary has far less incentive to organize public projects.Village government funds are spent instead on the wages of village officials,and the village government does not fund or organize public services. Villagers do not listen to the village Party secretary, and there is a high level of tax evasion.3Local guardian deities are seen as officials in a celestial bureau-cracy that mirrored the earthly imperial bureaucracy.Just as earthly government officials are assigned responsibility for a particular dis-trict or jurisdiction,officials in the celestial bureaucracy also take responsibility for a particular district or jurisdiction(Wolf1974).As we can see,South Bend’s church does not have a positive impact on village governmental performance. It sets clear standards for exemplary behavior and the conferral of moral standing and offers opportunities for members to show that they follow these standards, but village officials cannot take advantage of these op-portunities or participate in these institutions. Although the church does not improve public goods provision by the village government,it does,however, itself provide some public goods for the village.In1997 the church obtained a grant from the state Religious Affairs Bureau to replace the church’s roof.This grant bypassed the village government and went directly to the church.The church diverted20,000yuan from this grant to buy concrete and organized villagers to vol-unteer their labor so the village’s main road could be paved.Encompassing solidary groups which are not em-bedding,like South Bend’s village church,may be able to enforce norms of collective obligation among their members but cannot extend these norms to local offi-cials.They may be able to organize collective projects themselves but are far less able to hold government officials responsible for organizing these projects.All other things being equal,the hypothetical small-town mayor who does not belong to the town church is un-likely to be commended by the pastor during services and thus has less of an incentive to provide public ser-vices than the small-town mayor who does belong to the town church.In fact,as we see in South Bend, members of encompassing solidary groups may actu-ally hold officials in low regard precisely because they are not embedded in the group.One could argue that in democratic systems low regard for government of-ficials can be healthy and motivate citizens to monitor officials more closely.In these systems closer monitor-ing can improve governmental performance because democratic institutions such as elections enable them to sanction officials who perform poorly.Thus encom-passing groups that are not embedding may have a positive impact on local governance in democratic sys-tems.But in places which lack democratic institutions, autonomous civil society groups or solidary groups that are not embedding have much less direct impact on governmental performance.Low regard of govern-ment officials may increase their monitoring,but with-out well-implemented elections or legal guarantees, citizens may not be able to remove or punish officials if they detect misconduct.These groups thus cannot provide informal institutions to hold officials account-able for providing public services—–although they may be able to provide public services instead of the local government.Lineage Groups.The third type of solidary group commonly found in rural China is based on lineage soli-darity.Like village temple groups and village churches, lineage groups inculcate a sense of obligation to the group,but in this case obligation is based on concepts of family and shared patrilineal descent rather than on religious beliefs.Interviews with villagers and officials in all four provinces of the study indicated that like359。