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sec与csc

sec与csc

三角函数中sec csc 的意思以及有关的应用读音csc (扣赛肯体kou sai ken ti)cs cθsinθ=1sec(赛肯体 sai ken tiSEC正割sec在三角函数中表示正割直角三角形斜边与某个锐角的邻边的比,叫做该锐角的正割,用sec(角)表示。

正割与余弦互为倒数,余割与正弦互为倒数。

即:secθ=1/cosθ在y=secθ中,以x的任一使secθ有意义的值与它对应的y值作为(x,y).在直角坐标系中作出的图形叫正割函数的图像,也叫正割曲线.y=secθ的性质:(1)定义域,θ不能取90度,270度,-90度,-270度等值; 即θ≠kπ+π/2 或θ≠kπ-π/2 (k∈Z,且k=0)(2)值域,|secθ|≥1.即secθ≥1或secθ≤-1;(3)y=secθ是偶函数,即sec(-θ)=secθ.图像对称于y轴;(4)y=secθ是周期函数.周期为2kπ(k∈Z,且k≠0),最小正周期T=2π.CSC又叫余割函数:即在直角三角形中斜边比角的对边a 0` 30` 45` 60` 90`cosa 1 √3/2 √2/2 1/2 0 baobao1975 2009-07-15 14:06:30 正割-sec直角三角形斜边与某个锐角的邻边的比,叫做该锐角的正割,用sec(角)表示。

(sec的完整形式为secant)在y=secx中,以x的任一使secx有意义的值与它对应的y值作为(x,y).在直角坐标系中作出的图形叫正割函数的图像,也叫正割曲线.y=secx的性质:(1)定义域,{x|x≠kπ+π/2,k∈Z}(2)值域,|secx|≥1.即secx≥1或secx≤-1;(3)y=secx是偶函数,即sec(-x)=secx.图像对称于y轴;(4)y=secx是周期函数.周期为2kπ(k∈Z,且k≠0),最小正周期T=2π.正割与余弦互为倒数,余割与正弦互为倒数。

(5)secθ=1/cosθ余割-csc直角三角形斜边与某个锐角的对边的比,叫做该锐角的余割,用csc(角)表示。

tan z,cot z,sec z,csc z幂级数展开式的几种简明求法

tan z,cot z,sec z,csc z幂级数展开式的几种简明求法
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sec cot csc 读法

sec cot csc 读法

sec cot csc 读法### sec、cot、csc的读法在数学中,我们经常会遇到各种各样的三角函数,包括常见的正弦、余弦、正切等。

而在这些函数中,还有三个比较特殊的三角函数,它们分别是sec、cot以及csc。

本文将会介绍这三个函数的读法。

- sec的读法如下:sec [sek]sec函数是正切函数(tan)的倒数,即sec x = 1 / cos x。

它表示一个角的余割(cosecant)值的倒数。

- cot的读法如下:cot [kɒt]cot函数是正切函数(tan)的倒数,即cot x = 1 / tan x。

它表示一个角的余切(cotangent)值的倒数。

- csc的读法如下:csc [sɛk]csc函数是正弦函数(sin)的倒数,即csc x = 1 / sin x。

它表示一个角的余割(cosecant)值的倒数。

这三个函数在数学和物理学中都有广泛的应用。

它们可以用于求解三角方程、解析几何、计算力学问题等等。

因此,了解它们的读法和含义对于学习和应用三角函数是非常重要的。

需要注意的是,这些三角函数的值是由特定的角度决定的,而角度的单位可以是弧度(radian)或者度数(degree)。

在实际应用中,我们常常使用度数来度量角度。

在计算三角函数的时候,可以通过相关的公式将角度转换为弧度,再进行计算。

总结起来,我们可以通过使用这些特殊的三角函数(sec、cot、csc)来解决各种数学和物理问题。

通过掌握它们的读法和含义,我们可以更好地理解和运用三角函数的概念,提高数学和物理学习的效果。

从生命科学领域解读《Science》2009年度十大突破

从生命科学领域解读《Science》2009年度十大突破
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sec分离寡核苷酸孔径选择

sec分离寡核苷酸孔径选择

sec分离寡核苷酸孔径选择摘要:1.SEC 分离寡核苷酸的概述2.寡核苷酸孔径选择的重要性3.SEC 分离寡核苷酸的原理4.SEC 分离寡核苷酸的操作步骤5.SEC 分离寡核苷酸的应用案例6.SEC 分离寡核苷酸的发展前景正文:一、SEC 分离寡核苷酸的概述SEC(Size Exclusion Chromatography,尺寸排除色谱法)是一种根据样品分子大小进行分离的液相色谱技术。

在生物领域,SEC 常被用于分离寡核苷酸(oligonucleotides),寡核苷酸是具有生物学活性的核酸片段,广泛应用于基因工程、药物研发等领域。

二、寡核苷酸孔径选择的重要性寡核苷酸的孔径选择对其在生物体内的活性和功能至关重要。

合适的孔径有利于寡核苷酸的稳定性和生物活性,而不合适的孔径可能导致寡核苷酸结构不稳定,进而影响其功能。

因此,在SEC 分离过程中,选择合适的孔径对寡核苷酸的分离和纯化至关重要。

三、SEC 分离寡核苷酸的原理SEC 分离寡核苷酸的原理是根据样品中分子的大小和形状,在流动相和固定相之间产生不同的分配系数,从而实现样品的分离。

在SEC 过程中,寡核苷酸通过多孔凝胶颗粒的孔道,这些孔道具有一定的孔径。

根据寡核苷酸的大小,它们在孔道中的运动速率不同,从而达到分离的目的。

四、SEC 分离寡核苷酸的操作步骤1.样品准备:将寡核苷酸样品溶解在适当的缓冲液中,并进行过滤以去除杂质。

2.色谱柱安装:将多孔凝胶颗粒装填到色谱柱中,用缓冲液洗涤色谱柱以去除颗粒间的空气。

3.样品注入:将样品溶液注入色谱柱中,开始分离过程。

4.检测:采用紫外检测器或荧光检测器检测分离过程中的寡核苷酸。

5.数据处理:收集色谱图,根据峰面积和保留时间进行样品分析。

五、SEC 分离寡核苷酸的应用案例1.寡核苷酸库的筛选:通过SEC 技术筛选具有特定序列和功能的寡核苷酸。

2.寡核苷酸药物的研究:利用SEC 技术研究寡核苷酸药物的结构和稳定性。

8 网神SecSSLVPN 3600安全接入 全线产品白皮书-09V1.1

8 网神SecSSLVPN 3600安全接入 全线产品白皮书-09V1.1

网神SecSSL 3600安全接入网关系统产品白皮书网御神州科技(北京)有限公司目录1 产品概述 (3)2 产品特点 (3)3 产品功能 (7)4 产品型号及指标 (11)4.1 SSL VPN主机系统介绍 (11)4.2 SSL VPN辅件介绍 (18)5 产品资质与荣誉 (18)1 产品概述网神SecSSL 3600系列安全接入网关系统是网御神州推出的基于SSL协议标准全新架构的SSL VPN产品,是为企/事业单位提供安全、方便及高效的远程及内网安全接入方案。

通过对接入受控网络的主机进行全面的安全状态检查和修复,再加上细粒度的动态授权机制,SecSSL 3600确保接入用户的主机环境符合企业的安全策略要求。

系统也能够在用户访问结束后,根据安全策略的设置清除遗留在远程主机本地的数据,真正做到了“零”痕迹。

利用创新的智能终端识别和链路质量侦测技术,SecSSL 3600允许用户利用各种不同的移动计算终端快速地接入受控网络。

SecSSL 3600确保用户可以利用任意平台,随时随地安全及快速的访问内部资源,是目前企/事业单位远程及内网安全网络接入的最佳选择。

网神SecSSL 3600系列安全接入网关系统针对的应用环境包括(但不局限于)下列描述:●电子商务交易平台●电子政务应用系统●ERP、CRM、SCM、OA、财务、人力资源、物流管理等应用系统●MySQL、SQL Server、Oracle等各种数据库系统●网上银行●网络图书馆的远程安全接入和访问●电子邮件系统●协同设计系统●关键内部业务应用系统等2 产品特点●无客户端软件采用无客户端软件的解决方案,用户只需通过浏览器即可实现远程访问服务。

由于SSL VPN 使用了已嵌入于一般浏览器中的SSL协议,从而使管理员无需为终端用户提供软件安装、维护及策略定制的服务,仅需在VPN网关上设置用户访问权限即可。

●不改变用户使用习惯每个企业都根据自身的实际需要定制开发了一些应用系统,或者部署了一些服务来满足自己的需要,例如,使用Outlook的日历安排功能安排会议,为不同分支机构的IC设计工程师部署集中的Terminal Server以共享设计仿真资源等。

永大变频器使用说明书

永大变频器使用说明书

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sec色谱和正点离子

sec色谱和正点离子

sec色谱和正点离子
SEC色谱是一种分离和分析生物分子(通常是蛋白质或多肽)的方法,也被称为凝胶层析色谱。

它基于分子的大小和形状来分离样品中的不同分子,利用聚合物凝胶作为固相材料。

SEC色谱的基本原理是根据分子在凝胶网络孔隙中扩散速率
的差异来实现分离。

较大的分子由于其体积较大,在凝胶中扩散速率较慢,因此在色谱柱中流动速度较快,较小的分子则较快地穿过凝胶矩阵,流动速度较慢。

这样就可以将样品中的分子按照大小分离。

正点离子(或称阳离子)是指带有正电荷的离子。

在化学和生物化学中,正点离子可与带有负电荷的分子(如DNA、RNA)或基团(如羧酸基团)相互作用。

这种相互作用通常是通过静电相互吸引而发生的。

在某些分析方法中,正点离子也可以被用作色谱材料。

正点离子交换色谱基于正点离子与带有负电荷的分子之间的相互作用,通过改变溶液pH或添加盐来控制其吸附和解吸。

这样就可以
实现对样品中带有负电荷的分子的分离和富集。

网神SecSIS360安全隔离与信息交换系统(网闸)产品介绍09V1.0

网神SecSIS360安全隔离与信息交换系统(网闸)产品介绍09V1.0

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会话终结
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三个目的端。 • 实现传输后删除或者不删除。 • 实现文件增量传输,不变化不传输,只传输变化的文件。 • 适合于:用户有自己的文件服务器、具有较高的安全性要求的
3. 网神网闸产品功能介绍- FTP访问

09反函数与复合函数的导数,隐函数的导数

09反函数与复合函数的导数,隐函数的导数

y arcsin x 1 ,
cos y
注意到在区间
Iy


2
, 2

内,cos
y

1 x2 , 从而有
arcsin x 1 .
1 x2
5
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例2 求反正切函数 y arctan x的导数.
解 函数 y arctan x x 是 x tan y在
v(
x)
u(x) u(x)

.
该方法称为对数求导法.
28
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例12 求函数 y ln x x 的导数.
解 两边取对数后得
求导后有
ln y x lnln x,
1 y 1 lnln x x 1 1
y 2x
ln x x

2
1
x

ln
ln
x

dx du dx u
15
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例5 求函数 y arcsin x2 1的导数.
解 因 y arcsin x2 1 可视为
y arcsin u,u v,v x2 1
复合而成, 由复合函数求导公式(2.6)得:
dy dy du dv 1 1 2x dx du dv dx 1 u2 2 v
-4 -2 o 2 4 x -2 -4
25
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例10 求由方程 sin x y y2 cos x 确定的曲线在

sec分子量痕量线解读

sec分子量痕量线解读

sec分子量痕量线解读
SEC(Size Exclusion Chromatography,尺寸排阻色谱)是一种用于分析样品中分子大小和分子量的分离技术。

在SEC分析中,样品通过一根装有分离介质(如聚合物颗粒)的色谱柱,分子在色谱柱中根据其大小和形状被分离成不同的峰。

分子量痕量线是指在SEC色谱图中,分子量较大的组分形成的峰。

解读SEC分子量痕量线时,需要注意以下几点:
1. 峰形状:分子量痕量线的峰形状可以反映样品中分子量的分布。

通常,单峰表示分子量的分布较为集中,而多峰则表示存在多个分子量区域。

2. 峰位置:分子量痕量线的峰位置对应着样品中较大分子的分子量。

通过比较不同样品峰位置的变化,可以推断分子量的变化。

3. 峰高度:分子量痕量线的峰高度与样品中较大分子的含量有关。

峰高度越高,表示样品中较大分子的含量越多。

4. 分离程度:分子量痕量线的分离程度可以反映样品中分子量的分布范围。

分离程度越大,表示分子量的分布范围越宽。

5. 基线噪音:在解读分子量痕量线时,需要关注基线噪音。

基线噪音较小时,表示实验条件的稳定性和仪器灵敏度高。

6. 重复性:进行多次实验,观察分子量痕量线的重复性。

重复性好表示实验方法和条件的可靠性。

总之,通过解读SEC分子量痕量线,可以了解样品中分子量的分布特征,为药物研发、生物大分子分析等领域提供重要信息。

在实际应用中,还需要结合其他分析方法(如多角度光散射MALS、动态光散射DLS等)和专业知识,对分子量痕量线进行综合分析。

SEC Millenium Hydrocarbon Gas Detector 操作手册说明书

SEC Millenium Hydrocarbon Gas Detector 操作手册说明书

SEC Millenium HydrocarbonGas DetectorInstruction and Operation ManualSensor Electronics Corporation12730 Creek View AvenueSavage, Minnesota 55378 USA(952) 938-9486 Fax (952) 938-9617Email:************************************Document Number 1460002, Revision CSensor Electronics CorporationSensor Electronics Corporation (SEC) designs and manufactures innovative fixed system gas detection equipment, for combustible gases, oxygen, carbon dioxide and toxic gases.CommitmentOur quality and service are uncompromising. We back each of our products with a two-year warranty on all materials and workmanship. We offer technical support, user training and on-site service and maintenance of equipment to meet the needs of our customers.Gas Detection ServiceIndividually designed maintenance packages are available for specific customer needs. Service begins with verification of the system installation that includes an initial system check and calibration. We then offer customer training programs (on-site and at factory) to insure that technical personnel fully understand operation and maintenance procedures. When on-the-spot assistance is required, service representatives are available to handle any questions or problems immediately.WARRANTYSENSOR ELECTRONICS CORPORATION (SEC) WARRANTS PRODUCTS MANUFACTURED BY SEC TO BE FREE FROM DEFECTS IN WORKMANSHIP AND MATERIALS FOR A PERIOD OF TWO (2) YEARS FROM DATE OF SHIPMENT FROM THE FACTORY. ANY PARTS RETURNED FREIGHT PRE-PAID TO THE FACTORY AND FOUND DEFECTIVE WITHIN THE WARRANTY WOULD BE REPAIRED OR REPLACED, AT SEC'S OPTION. SEC WILL RETURN REPAIRED OR REPLACED EQUIPMENT PRE-PAID LOWEST COST FREIGHT. THIS WARRANTY DOES NOT APPLY TO ITEMS, WHICH BY THEIR NATURE ARE SUBJECT TO DETERIORATION OR CONSUMPTION IN NORMAL SERVICE. SUCH ITEMS MAY INCLUDE:CHEMICAL SENSOR ELEMENTSFUSES AND BATTERIES.WARRANTY IS VOIDED BY ABUSE INCLUDING ROUGH HANDLING, MECHANICAL DAMAGE, ALTERATION OR REPAIR. THIS WARRANTY COVERS THE FULL EXTENT OF SEC LIABILITY AND SEC IS NOT RESPONSIBLE FOR REMOVAL, REPLACEMENT COSTS, LOCAL REPAIR COSTS, TRANSPORTATION COSTS OR CONTINGENT EXPENSES INCURRED WITHOUT PRIOR WRITTEN APPROVAL. SENSOR ELECTRONICS CORPORATION'S OBLIGATION UNDER THIS WARRANTY SHALL BE LIMITED TO REPAIR OR REPLACEMENT OF ANY PRODUCT THAT HAS BEEN RETURNED TO SENSOR ELECTRONICS CORPORATION FOR WARRANTY CONSIDERATION. THIS WARRANTY IS EXPRESSLY IN LIEU OF ANY AND ALL OTHER WARRANTIES EXPRESSED OR IMPLIED, AND ALL OTHER OBLIGATIONS OR LIABILITIES ON THE PART OF SENSOR ELECTRONICS CORPORATION INCLUDING BUT NOT LIMITED TO, THE FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SENSOR ELECTRONICS CORPORATION BE LIABLE FOR DIRECT, INCIDENTAL, OR CONSEQUENTIAL LOSS OR DAMAGE OF ANY KIND CONNECTED WITH THE USE OF IT'S PRODUCTS OR FAILURE TO FUNCTION OR OPERATE PROPERLY.WARNING: READ AND UNDERSTAND THE USER’S MANUAL BEFORE OPERATING OR SERVICINGWARNING: KEEP COVER TIGHT WHILE CIRCUITS ARE LIVECAUTION: FOR SAFETY REASONS THIS EQUIPMENT MUST BE OPERATED ANDSERVICED BY QUALIFIED PERSONEL ONLYRevision HistoryTable of ContentsRevision History (3)Table of Contents (4)I. SPECIFICATIONS (5)II GENERAL DESCRIPTION (6)III. OPERATION (8)IV. CALIBRATION (10)V. MAINTENANCE (10)VI. Parts List (11)VII. Drawing Section (12)I. SPECIFICATIONSModel:Sensor Electronics Corporation SEC MILLENIUM Infrared Hydrocarbon Gas DetectorAvailable gases:Methane Hexane Jet A TolueneEthane Diesel Ethanol P-XyleneEthylene Gasoline Methanol Tert-Butyl AcetateEthylene Oxide Green Earth Butane MEKPropane DF 2000 HexanePlease note that this list is not all-inclusive. The SEC MILLENIUM can be calibrated for most hydrocarbons, provided a calibration gas is available. For more please contact Sensor Electronics Corporation.Part Number: 1420280Detection Method:DiffusionOptional sample draw (requires a minimum of 1 liter per minute flow rate)Output (analog):4-20 mA (Source type), max. 1000 Ohm load at 24 VDC supply voltageResponse Time:T50 < 5 secondsT90 < 10 secondsConstruction:316 stainless steel.Accuracy:+/- 3% LFL, 0 to 50% LFL (Lower Flammable Limit)+/- 5% LFL, 51 to 100% LFLOperating Temperature Rating:-40︒ to +70︒C at 0 to 99% RH (non-condensing)Operating Voltage:24 VDC Operating range: 18 to 32 VDC measured at the detector headPower Consumption: 5 Watts Max.Max. Current Draw: (at 24 VDC)Average: 210 mAPeak: 400 mAApprovals:Explosion Proofness: Class I, Division 1, Groups B,C and D, Temp T5; (CSA for -40C to +50C) Combustible Gas Performance: C22.2 No 152, ANSI/ISA 12.13.01 – 2000; (CSA)UL 2075, Methane 0-100%LEL Only; (Conforms to UL2075, Intertek Listed)(UL2075 Listing requires the use of the SEC3120 Transmitter.) Installation Category: Cat. I, Pollution Degree 2II GENERAL DESCRIPTIONCONVENTIONSThe following conventions are used in this manual.!Warning or Caution StatementVDC (DC Voltage)SEC MILLENIUMThe SEC MILLENIUM Infrared gas detector is a microprocessor based intelligent gas detector that continuously monitors combustible hydrocarbon gases and vapors within the Lower Flammable Limit (LFL).The SEC MILLENIUM is ideally suited for use in harsh environments and where the cost of required maintenance for conventional catalytic detectors is prohibitive. The SEC MILLENIUM Infrared gas detector will perform reliably in the presence of silicone and other catalytic poisoning agents and can also operate in oxygen free environments or where high background gas levels are present. There are no known poisons that affect this technology.The SEC MILLENIUM is a stand-alone device providing a continuous 4 to 20 mA output.Features∙Requires no routine calibration to ensure proper operation.∙ Continuous self-test automatically indicates a fault, with fail to safe operation.∙ A multi-layered filtering system protects optics from dirt and water ingress.∙Straight optical path eliminates the need for mirrors or reflective surfaces, such as mirrors or beam splitters.∙Performs well in the presence of high concentrations or constant background levels of hydrocarbons and in oxygen depleted atmospheres.∙Highly resistant to poisoning and etching.∙Standard 4 to 20 mA output (current source)∙Explosion proof housing designed for harsh environments.∙Smart Calibration AutoAC™ circuit.Infrared Detection TechnologyThe SEC MILLENIUM Infrared gas detector uses infrared absorption technology for detecting combustible hydrocarbon gases. Gases absorb infrared light only at certain wavelengths. The concentration of a gas can be measured by the difference of two channels (wavelengths), a reference and a measurement channel. The SEC MILLENIUM uses a collimated infrared light source that passes through a waveguide, at the end of the waveguide is a dual channel receiver. The dual channel receiver measures the intensity of two specific wavelengths, one at an absorption wavelength and another outside of the absorption wavelength. The gas concentration is determined by a comparison of these two values.Infrared Absorption Spectrum for MethaneThe dual channel receiver is a single wafer, double filtered, dual receiver with an internal optical barrier. The elements are perfectly matched resulting in overall stability and superior performance throughout the entire temperature range.Using a dual channel receiver there is no need to use any special lenses or beam splitters to achieve the different measurement bands.The SEC MILLENIUM utilizes a unique, patented feature; the AutoAC ™ circuit. The AutoAC ™ circuit is an automatic analog control circuit, which allows the SEC MILLENIUM to be calibrated for any combustible hydrocarbon, provided that a calibration quality level of the gas is available. This eliminates setting dipswitches or changing out sensors for different types of hydrocarbons, simply calibrate the unit with a calibration gas of the specific gas to be detected.The optics can be easily disassembled for cleaning. This does not require powering the unit down and does not compromise the units’ explosion proof rating. The device will self-compensate for dirty optics until a point in which the optical surfaces are completely obscured.There are no consumable components contained in this product.Wavelength100%Dual Channel Infrared LightIII. OPERATIONInstallation and StartupWarning: If the equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment may be impaired.The first step in the installation process is to establish a mounting location for the SEC MILLENIUM. Select a location that is typical of the atmosphere to be monitored or close to the anticipated source of a dangerous gas.It is very important that the SEC MILLENIUM be properly located to enable it to provide maximum protection. The most effective number and placement of sensors vary depending on the conditions of the application. When determining where to locate sensors the following factors should be considered.∙What are the characteristics of the gas that is to be detected? Is it lighter or heavier than air? If it is lighter than air the sensor should be placed above the potential gas leak. Place the sensor close to the floor for gases that are heavier than air or for vapors resulting from flammable liquid spills. Note that air currents can cause a gas that is heavier than air to rise. In addition, if the temperature of the gas is hotter than ambient air or mixed with gases that are lighter than air, it could also rise.∙How rapidly will the gas diffuse into the ambient air? Select a location for the sensor that is close to the anticipated source of a gas leak.∙Wind or ventilation characteristics of the immediate area must also be considered. Movement of air may cause gas to accumulate more heavily in one area than in another. The detector should be placed in the areas where the most concentrated accumulation of gas is anticipated. For outdoor applications with strong wind conditions, it may require the sensors to be mounted closer together and on the downwind side, to the anticipated area of a gas leak. Also take into consideration for indoor applications, the fact that many ventilation systems do not operate continuously.∙The sensor should be accessible for maintenance.∙Excessive heat or vibration can cause premature failure of any electronic device and should be avoided if possible.∙Follow all national and local installation codes and practices.The SEC MILLENIUM has a ¾” NPT threaded connector for mounting the detector to a junction box. SEC can provide a junction box with terminals for this purpose.A user-supplied junction box can be used providing it has the appropriate sized NPT conduit entries. The junction box must be suitable for use in the application and location in which it is being installed.After the device has been installed, a calibration is required. Refer to the Calibration section of this manual. Wiring connectionsRed wire: 18 to 32 VDCBlack wire: DC CommonBlue wire: 4 to 20 mA outputWhite wire: Smart Calibration Wire (data wire)Earth Ground: Male 10-32 Stud on SEC Millenium cap, see figure 1.Wire sizing:0 to 500 feet, recommended wire gauge size 16 AWG501 to 1000 feet, recommended wire gauge size 14 AWGShielded cable is recommended. Wiring should be installed in metal conduit with no other cabling in the same conduit.Warm-upWhen power is applied to the detector, it enters a one (1) minute warm-up mode. The output current will be 4.0 mA during the warm up time period. At the end of the warm-up period with no faults present, the detector automatically enters the normal operating mode and continues to show 4 mA. If a fault is present after warm-up, the detector current output will indicate a fault. See the following chart for fault code status.NormalIn the normal operating mode, the 4-to-20 mA signal levels correspond to the detected gas concentration. The detector continuously checks for system faults or initiation of calibration and automatically changes to the appropriate mode.The 4 to 20 mA output of the SEC MILLENIUM is a non-isolated current source.Current Output and Corresponding StatusOnce the fault is cleared the SEC MILLENIUM will atomatically resume normal operation.IV. CALIBRATIONSEC MILLENIUMThe SEC MILLENIUM is factory calibrated; zeroed and spanned. Unlike catalytic sensors it does not require routine span gas calibration to ensure proper operation.The SEC MILLENIUM can be calibrated for almost any hydrocarbon using a calibration gas of the hydrocarbon that is to be detected (target gas). The SEC MILLENIUM is required to be spanned with gas only one time with the target gas. Typically this is done at the factory, but it is possible to field span the device by connecting the SEC MILLENIUM to a computer and using a software package provided by SEC. Please contact the factory for further details.A typical field calibration only requires the use of zero air (or 99.99% nitrogen). If the sensor is located in an area that is known to be free of the hydrocarbon gases then ambient air can be used as a zero reference.If zero air is used for the calibration, there is a fitting on the bottom of the sensor for a 1/8” ID tubing connection.Before beginning calibration use the SEC MILLENIUM Insulation Tube to cover outer cylinder holes and connect a clean air source to the sensor’s calibration port for a minimum of 3 minutes. To enter into the calibration mode the calibration wire must be connected to negative (common of the power supply) for ten (10) seconds, upon release the sensor will automatically enter the zero calibration routine. The electronics will automatically adjust the sensor’s signal to the new zero reference level. (Applying span gas is not necessary because of the SEC MILLENIUM’s unique software algorithms). During the zero calibration routine, the current output of the SEC MILLENIUM will go to 2.2 mA. Although this can be accomplished manually, installation of a switch (contact closure) can accomplish the zeroing procedure. It is recommended that this switch be a momentary type switch to prevent it from inadvertently being left in the calibrate position. If after 20 seconds the calibration lead has not been removed from common, the SEC MILLENIUM will ignore the signal and continue operation as normal.The SEC MILLENIUM can be spanned in the field if the customer wishes to change the target hydrocarbon gas. Please contact factory for additional equipment information and pricing for SEC PC IR Link Package) V. MAINTENANCEThe SEC MILLENIUM does not normally require cleaning of the optics. However if the unit is operating in a very dirty or dusty environment the optical path might become obscured. If the obscuration is severe enough to affect the unit’s accuracy, the unit will activate an “Optics Fault”. To clear an Optics Fault, first try a calibration. If the calibration does not correct the fault condition, try to clean the optics. The outer barrel (tube with two sets of holes) can be removed (unscrewed) to inspect the cleanliness of the hydrophobic filter. The hydrophobic filter is a Teflon coated stainless steel mesh that keeps moisture and particulates out of the optical path. A setscrew holds the fil ter to the MILLENIUM’s housing. Once the hydrophobic filter is removed, the internal waveguide tube should be inspected for cleanliness. The waveguide and waveguide collar can be removed by inserting rigid instruments such as Allen wrenches into one hole of the waveguide and one hole of the collar. Turning the two instruments in opposite directions will loosen the waveguide allowing the collar to be screwed down on to the waveguide until it can be removed from the SEC MILLENIUM housing. This will allow the windows of the SEC MILLENIUM to be cleaned. Dust can be removed using compressed air. Hard or oily deposits can be removed using Isopropyl alcohol and cotton tipped swabs. Wipe any film or residue or film left by the alcohol on the windows with a clean dry cotton swab. The internal surface of the electro-polished wave-guide tube can be cleaned the same way. Be careful not to leave any particles of the cleaning swab in the waveguide. The waveguide holes can collect pieces of the cleaning swab. After reassembling the unit (the waveguide and collar should be very tight to both ends of the SEC MILLLENIUM housing after installation. Once the unit is completely reassembled and power is reapplied, the SEC MILLENIUM must be calibrated. Refer to the calibration section of this manual.VI. Parts ListPart Number Description142-0280 Replacement Sensor SEC MILLENIUM190-1001 SEC 2001 Sensor Separation Kit142-0877 SEC Insulation Tube142-0497 SEC MILLENIUM Replacement Hydrophobic Filter 142-0297 SEC MILLENIUM Wave Guide Tube142-0570 SEC MILLENIUM Wave Guide Tube Collar142-0636 SEC PC IR Link KitVII. Drawing SectionFigure # TitleFigure 1 Wiring Diagram, SEC MILLENIUM Figure 2 SEC Sensor Separation Kit。

SEC2000微机励磁调节装置说明书_09版_

SEC2000微机励磁调节装置说明书_09版_

概述SEC2000微机励磁调节器装置以经典和现代控制理论与微机控制技术相结合的新型励磁调节器。

它不但具有常规调节器的全部调节控制功能。

并具有常规调节器所不具备的许多控制、限制、保护和容错等功能。

它是现代同步发电机组较为理想的励磁调节装置。

它适用于各种方式的可控硅励磁,是一种通用性极强的励磁调节装置。

微机励磁调节器以其优良的控制调节规律、完备的限制及保护手段、通用和灵活的系统功能、简单的操作和维护、智能化的试验开发以及高的可靠性为主要特征。

本说明书将从SEC2000微机励磁调节装置的基本原理,安装操作,投运维护几个方面做一介绍。

产品在使用安装前清务必详细阅读本说明书以及有关技术资料,以便对SEC2000微机型励磁调节装置有一较全面的了解,避免不必要的人为使用错误。

与本手册有关的技术文件:1. 《SEC2000微机励磁调节装置电路原理图》2. 《SEC2000微机励磁调节装置接线图》3. 《EU30/ EU32 控制器操作说明书》微机励磁调节装置一般与功率整流装置、灭磁过电压保护装置等组成成套励磁控制装置,并在本公司统一设计、生产和供货,有关功率整流装置和灭磁过电压保护装置参见本公司随行的装置说明书和成套图纸资料。

目录1 装置的特点及适用范围 (2)1.1 主要特点 (2)1.2 装置的适用范围使用环境 (2)2 主要功能及技术参数 (5)2.1 装置的主要功能 (5)2.2 主要技术参数 (5)3 系统配置 (6)3.1 电气配置 (6)3.2 结构配置 (7)4 设备的安装与操作说明 (12)4.1 设备的安装 (12)4.2 操作说明 (13)5 设备的投运与维护 (19)5.1 设备的投运试验 (15)5.2 设备的维护 (18)6 装置的基本工作原理 (19)6.1 操作原理及I/O口配置(参见接线图) (19)6.2 硬件工作原理 (20)6.3 软件介绍 (21)7 产品的成套性与订货 (28)7.1 产品的成套性 (27)7.2 备品备件 (28)7.3 设备随行资料 (28)7.4 订货须知 (28)8 设备的质量承诺与售后服务 (28)8.1 技术支持 (28)8.2 质量承诺 (29)1 装置的特点及适用范围1.1 主要特点SEC2000励磁调节装置是针对同步发电机可控硅励磁系统设计的新一代全数字式微机励磁调节装置,它的主要特点有:1. 较强的通用性和灵活性。

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IX. The Wigner-Eckart theoremWe will now touch on a result that relates very deeply to the rotational symmetry of space. However, its practical consequences are somewhat limited, and so we will only go over it in faint detail. The basic thing that we observe is that simply looking at how quantum states behave under rotation gave us a terrific amount of insight into the quantum theory of angular momentum. One can ask the corresponding question about operators: how do quantum operators behave when we rotate the system and what do we learn about operators in general (and most importantly, their matrix representations!) by studying their rotational character? We will find many connections to our results for the addition of angular momenta.a. Spherical TensorsKey to the statement of the Wigner-Eckart theorem is the definition of spherical tensor operators. This is rendered quite difficult by the fact that most chemists and physicists do not know what a spherical tensor is (never mind the operator part). This is just a geometrical concept, and once again we will find that the transition to quantum mechanics is trivial; all the “weirdness” is classical.Under rotation, a classical observable T changes asRr (θ)⋅ p ),,T ( p r ) ⎯⎯→ T( R(θ)⋅ Rn nRwhere “ ⎯ ⎯→ ” indicates the act of rotation and R (θ) is a matrixnrotates vectors by an angle θ about a unit vector n, as in the section on angular momentum. Now, the interesting fact is that there are certain groups of observables that are related to one another by rotation. Further, one finds that these groups always have an odd number of members! Any such group of observables with 2k + 1 elements is said to compose a spherical tensor of rank k (also called irreducible tensors). By convention, these operators are indexed with the 2k + 1numbers q =− k,− k+ 1,...k − 1,k . Mathematically, we require that any rotated element of the tensor be expressible as a linear combination of the un-rotated elements:kq Rq ' q T k ⎯⎯→ ƒT D k q ' q′ − = k q where the coefficients D q ' will depend on the axis and angle of rotation. A few examples are helpful:1) Rank 0: These are typically called scalars. Examplesinclude all pure numbers and the dot product of any twovectors, for example:T R T r ⋅ r ⎯⎯→ r = r ⋅ r 2) Rank 1: These are typically called vectors. Examplesinclude angular momentum ( L ) as well as r and p :3Rr i ⎯⎯→( R (θ)⋅ r )= ƒ( R (θ)) ij r j n i n j = 1 r If we want to associate the components of the vector withthe q =−1,0,1ordering, it is convenient to define + 1 = x + i y r 0 = z r − 1 = x − iy . Note the similarity with angular momentum and theJ ˆ + , J ˆ, J ˆ − operators.z 3) Rank 2: No special name here, but one can typicallyextract a spherical tensor of rank 2 from a matrixM = u ⊗ v (where u and v are vectors) by subtracting itstrace (a scalar) and a term that looks like the crossproduct of u and v (a vector). To be precise:T ~ u ⋅ i j −M ij = M ij − 3 v δ ij v u j − v u i 2The original matrix had 3x3=9 components so removing 1with the scalar and 3 with the vector leaves 9-1-3=5 left­over components that conveniently make up a second ~ rank tensor M .Overall, we stress the resemblance of a spherical tensor of rank k to a system with k units of angular momentum.b. Spherical tensor operatorsTo put it succinctly, a spherical tensor operator in quantummechanics is simply an operator that behaves like a spherical tensor under rotations. Thus, for a tensor operator of rank k :kqq ' q T ˆ k ΩƒT ˆ D k q ' q′− = k The quantum definition is more general than the classical one, in that it encompasses (in principle) a greater variety of possible rotations, including ones in “spin” space. However, in practice we will be most interested in physical rotations.c. The Wigner –Eckart TheoremThe Wigner-Eckart theorem tells us what information we can discernabout the matrix elements of a spherical tensor operator Tˆ between k angular momentum eigenstates. The reason we are interested in this is that we know that tensor operators have a special relationship to rotations, and these rotations are generated by angular momentum. Note that this is only interesting if the eigenstates and the tensor are defined with respect to the same type of rotation. For example, if the operators form a spherical tensor with respect to spin rotations, there need be no special relationship of these operators between orbital angular momentum eigenstates.We thus wish to compute a matrix element like: q α, ' j , ' m ' T α, j, m k where α and α' symbolize the values of all other quantum numbers in the system (e.g. principal quantum number, spins, vibrational quantum numbers, etc.). The Wigner-Eckart theorem tells usq α, ' j , ' m ' T α, j, m = j , q k m ;, j , ' m ; ' j , k α, ' j ' T k α, j k the first term is just the CG coefficient for two angular momenta (of magnitudes j and k ) coupling together to make a total angularmomentum of magnitude j' . The second term is called the reduced matrix element. The theorem does not give us any way to constructthis, but the important point is it depends only on α, j', j and k . Wewill not prove this result, but a proof can be found in several different text books (e.g. Sakurai p.239 and Merzbacher, p. 396, but not CTDL).What insight does this give us? Well, first it is important to note thatthis result jives with our observation that Tˆ behave as if they had k angular momentum of magnitude k -the CG coefficients involve coupling j units of angular momentum (from the ket) with kadditional units to make a total angular momentum j' (in the bra). Where else could the angular momentum be coming from, if not T ˆ ?kSecond, this allows us to apply our selection rules for the CG coefficients to drastically reduce the number of coefficients we calculate. Specifically, the matrix element is zero unless:q = m ′− m and j − j ' ≤ k ≤ j + j ′ .The first relation is just conservation of total m applied to the CG coefficient and the second is the triangle rule at work. Finally, it is important to note that the reduced matrix element does not dependon which element of Tˆ k we choose (i.e. does not depend on q ) and it does not depend on m or m' . This drastically reduces the work we have to do in practice. For example, if we want to compute the matrix elements of z between the Hydrogenic eigenfunctions, we note that z is a component of the rank 1 tensor r and so:, ' ' ,, ,l n , ' m l n z m = ml 0,1; l , ' m ; ' l 1, l n z l n , ' ' , which implies that this matrix element is zero unlessm ′− m = 0 and j − j ' ≤ k ≤ j + j′ which is more familiar asΔ m = 0 and Δ j = ,0 ± 1with j = j' = 0 excluded. This is an example of a selection rule . You will see a great many more relations like this next semester.。

Sec09_瞬态响应

Sec09_瞬态响应

少(30*40)*5 = 6000 时间步将被需要。
NAS122, Section 9, March 2011 Copyright 2011 MSC.Software Corporation S9-10
案例分析:直接瞬态响应分析
NAS122, Section 9, March 2011 Copyright 2011 MSC.Software Corporation
NAS122, Section 9, March 2011 Copyright 2011 MSC.Software Corporation
S9-8
直接瞬态响应分析(续)
● 在时间分析中的几点建议:
● 总体上 ● 经常在milliseconds (ms)层次考虑问题; 0.001sec = 1ms.
a. b. c. d. e. f.
a
e h f
b
c
d i
NAS122, Section 9, March 2011 Copyright 2011 MSC.Software Corporation
g
S9-15
案例分析:直接瞬态响应分析(续)
为力载荷创建一个非空间场函数. a
Properties: Create / NonSpatial/ Tabular Input 输入 force 为场函数名称. 选择 Time (t) 作为独立变量. 点击 Input Data. 点击 Map Function to Table. 输入 –sind(250*360*’t) 和作用载荷起始时间、 终止时间、步数等参数 g. 点击 Apply. h. 点击 OK . i. 点击 Apply.
● 需要检查结构的最低振动频率,保证结构衰减需要的最少时间。假定,在上面的

伊拉克项目评价SEC

伊拉克项目评价SEC

伊拉克SEC项目分析及评价一、项目背景1、基本信息建设地点:位于伊拉克首都巴格达以南120公里的瓦西特省境内,底格里斯河西岸。

项目名称:伊拉克EPC项目工程规模:新建4×330MW燃油电站,电厂区域面积大约120公顷;锅炉以燃烧重油或原油为主,同时也可以燃烧天然气,点火油为轻柴油;没有输煤、除灰、除尘、除渣系统;机力通风冷却塔。

业主:伊拉克电力部工期: 34+6+5+5 个月;SEC预计09年初收到预付款,09年7-8月进驻。

2、项目组成EPC方:上海电气公司设计方:山东电力设计院设备方:三大设备均为上海电气供货施工方:当地分包商3、服务范围:1)负责EPC总合同范围内土建、安装、单机调试的技术指导及监督工作。

2)负责汽轮发电机组本体安装工作(包括润滑油、密封油系统),工作范围及接口参照《电力工程建设预算定额》。

3)负责DN80以下(含DN80)小管及支吊架的现场布置设计,绘制相关的布置图及安装技术指导,并提供有关详细资料供设计院出竣工图纸。

4、EPC价格:约10亿美元5、伊拉克项目简要信息伊拉克全称伊拉克共和国,位于亚洲西南部,阿拉伯半岛东北部,面积4.4万平方公里。

北接土耳其,东邻伊朗,西毗叙利亚、约旦,南连沙特阿拉伯、科威特,东南濒波斯湾。

截止2007年底,伊拉克全国人口为3050万,伊拉克是一个多民族的国家,其中阿拉伯人占73.5%,库尔德人占21.6%,其余为土耳其人,亚美尼亚人,亚述人,犹太人和伊朗人。

居民中95%信奉伊斯兰教(什叶派约占54.5%,逊尼派占40.5%),北部的库尔德人也信仰伊斯兰教,他们多属逊尼派,只有少数人信奉基督教或犹太教。

官方语言为阿拉伯语。

现场的最高气温46.7℃,最低气温1.8℃,平均气温22.1℃;平均年降雨量124mm;平均风速4.1m/s;基本风压0.8KN/m2。

电厂区域的地质状况良好,不存在地质缺陷;整个厂区的标高在22.90m—23.90m之间;土壤构造是为15米厚的沾土层及下面的沙层;地下水位为1.4—4米,其中含有硫酸盐及氯化物。

sec凝胶法

sec凝胶法

sec凝胶法SEC凝胶法(SDS-PAGE)是一种常用的蛋白质分离和分析方法。

它是以电泳为基础的技术,通过将蛋白质样品加入凝胶中,利用电场的作用使蛋白质在凝胶中进行电泳迁移,根据蛋白质的分子量大小进行分离。

SEC凝胶法的原理是利用聚丙烯酰胺凝胶(Polyacrylamide Gel)作为分离介质,将蛋白质样品加入凝胶孔道中。

聚丙烯酰胺凝胶是一种有机高分子化合物,它能够形成一种网状结构,具有一定的孔隙度。

当电场施加在凝胶上时,蛋白质会受到电场的作用而向电极方向移动。

由于聚丙烯酰胺凝胶的孔隙度不同,不同大小的蛋白质分子在凝胶中的迁移速率也不同,从而实现了蛋白质的分离。

SEC凝胶法的步骤如下:1. 制备凝胶:将聚丙烯酰胺溶液中加入过硫酸铵和N,N,N',N'-四甲基乙二胺,搅拌均匀后倒入凝胶板中。

加入甲醇上层,形成平整的凝胶表面,并在表面覆盖一层甲醇。

2. 将样品与SDS缓冲液混合:将待测蛋白质样品与SDS缓冲液混合,并在100℃下加热,使蛋白质变性。

3. 加载样品:将变性后的蛋白质样品通过微量注射器或微量移液器加入凝胶孔道中。

4. 加电泳:将凝胶板放入电泳槽中,加入电泳缓冲液,然后施加电场,使蛋白质样品开始迁移。

5. 显色和成像:经过一段时间的电泳迁移后,关闭电场,取出凝胶板。

可以使用染色剂(如Coomassie Blue染色剂)对蛋白质进行染色,然后观察凝胶板上的蛋白质条带,或者使用成像仪对凝胶板进行成像。

SEC凝胶法的优点在于分离效果好,能够分离出不同分子量的蛋白质,从而对蛋白质进行定性和定量分析。

同时,SEC凝胶法具有操作简单、结果可靠、重复性好等特点,广泛应用于生物化学、分子生物学等领域。

SEC凝胶法有一些注意事项需要注意。

首先,凝胶的制备过程需要注意操作技巧,以免产生气泡或凝胶不均匀。

其次,加载样品时要避免过多或过少的样品加入,以免影响分离效果。

此外,电泳条件的选择也会影响分离结果,需要根据实验需要进行优化。

常见单位转换

常见单位转换

常见单位转换分类:工业知识2021-04-22 09:2439人阅读评论(0)收藏举报Unit names Alternate names /spellingsAbbreviation Enumeration CodeConversion Rate (relativeto first unit)DistanceMeter metre m unit_m 1 Feet Foot ft unit_ft 3.280839895 Furlongs Furlong fur unit_fur 0.00497097 Inches Inch in unit_in 39.37007874 Light years Lightyears ly unit_ly 1.06E-16 Miles Miles mile unit_mile 0.000621371 Nautical Miles Nautical Mile nmile unit_nmile 0.000539957 Parsecs Parsec psc unit_psc 3.24E-17 Yards Yard yd unit_yd 1.093613298FlowLitres/second Liters/second l/s unit_l_s 1 Feet3/hour Foot3/hour cu ft/hr unit_ft3_hr 127.1328002 Feet3/minute Foot3/minute cu ft/min unit_ft3_min 2.118880003 Feet3/second Foot3/second Cu ft/sec unit_ft3_sec 0.035314667 Gallons (UK)/day Gallon (UK)/day gal/da (UK) unit_gal_da_uk 19005.33469 Gallons (UK)/hour Gallon (UK)/hour gal/hr (UK) unit_gal_hr_uk 791.8889455 Gallons (UK)/minute Gallon (UK)/minute gal/min (UK) unit_gal_min_uk 13.19814909 Gallons (UK)/second Gallon (UK)/second gal/sec (UK) unit_gal_sec_uk 0.219969152 Gallons/day Gallon/day gal/da unit_gal_da 22824.46532 Gallons/hour Gallon/hour gal/hr unit_gal_hr 951.0193885 Gallons/minute Gallon/minute gal/min unit_gal_min 15.85032314 Gallons/second Gallon/second gal/sec unit_gal_sec 0.264172052 Litres/day Liters/day l/da unit_l_da 86400 Litres/hour Liters/hour l/hr unit_l_hr 3600 Litres/minute Liters/minute l/min unit_l_min 60 Meters3/day Metres3/day cu m/da unit_m3_da 86.4 Meters3/hour Metres3/hour cu m/hr unit_m3_hr 3.6Meters3/minute Metres3/minute cu m/min unit_m3_min 0.06 Meters3/second Metres3/second cu m/sec unit_m3_sec 0.001 Ounces (UK)/hour Ounce (UK)/hour oz/hr (UK) unit_oz_hr_uk 126702.2313 Ounces (UK)/minute Ounce (UK)/minute oz/hr (UK) unit_oz_min_uk 2111.703855 Ounces (UK)/second Ounce (UK)/second oz/hr (UK) unit_oz-hr_uk 35.19506424 Ounces/hour Ounce/hour oz/hr unit_oz_hr 121730.4817 Ounces/minute Ounce/minute oz/min unit_oz_min 2028.841362 Ounces/second Ounce/second oz/sec unit_oz_sec 33.8140227 Yards3/hour Yard3/hour cu yd/hr unit_yd3_hr 4.70862223 Yards3/minute Yard3/minute cu yd/min unit_yd3_min 0.078477037 Yards3/second Yard3/second cu yd/sec unit_yd3_sec 0.001307951DensityGrams/Meter3 Grams/Metre3 g/cu m unit_g_m3 1 Ounces/Gallon Ounce/Gallon Oz/gal unit_Oz_gal 0.000133526 Pounds/Foot3 Pounds/Feet3 lb/cu ft unit_lb_ft3 6.24E-05 Pounds/Inch3 Pound/Inch3 lb/cu in unit_lb_in3 3.61E-08 Tons/Yard3 Tonne/Yard3 T/cu yd unit_T_yd3 1.44E-06AreaMeters2 Metres2 sq m unit_m2 1 Acres acre a unit_a 0.000247104 Feet2 foot2 sq ft unit_ft2 10.76391042 Hectares Hectare ha unit_ha 0.0001 Inches2 Inch2 sq in unit_in2 1550.0031 Miles2 Mile2 sq mi unit_mi2 3.86E-07 Yards2 Yard2 sq yd unit_yd2 1.195990046AngleRadians Radian rad unit_rad 1 Circles Circle cir unit_cir 0.159154943Degrees Degree deg unit_deg 57.29577951 Grades Grade grd unit_grd 63.66197724 Minutes Minute min (angle) unit_min_angle 3437.746771 Octants Octant octant unit_octant 1.273239545 Revolutions Revolution rev unit_rev 0.159154943 Seconds Second sec unit_sec_angle 206264.8062 Turns Turn trn unit_trn 0.159154943 Quadrants Quadrant quad unit_quad 0.636619772AccelerationMeters/sec2 Metres/sec2 m/sq sec unit_m_sec2 1 Feet/sec2 foot/sec2 ft/sq sec unit_ft_sec2 3.280839895 Free fall (g) gravity g (grav) unit_grav 0.101971621 Inches/sec2 Inch/sec2 in/sq sec unit_in_sec2 39.37007874SpeedMeters/second Metres/second m/sec unit_m_sec 1 Meters/minute Metres/minute m/min unit_m_min 60 Meters/hour Metres/hour m/hr unit_m_hr 3600 Feet/second foot/second ft/sec unit_ft_sec 3.280839895 Feet/minute foot/minute ft/min unit_ft_min 196.8503937 Feet/hour foot/hour ft/hr unit_ft_hr 11811.02362 Knots Knot kt unit_kt 1.943844492 Mach Machs Ma unit_Ma 0.003016955 Miles/second Mile/second mi/sec unit_mi_sec 0.000621371 Miles/minute Mile/minute mi/min unit_mi_min 0.037282272 Miles/hour Mile/hour mph unit_mph 2.236936292PressurePascals Pascal Pa unit_Pa 1 Atmospheres Atmosphere atm unit_atm 9.87E-06Bars Bar bar unit_bar 1.00E-05 Cm of Mercury Cm Mercury cmHg unit_cmHg 0.000750062 Dynes/Centimeter2 Dynes/Centimetre2 dyn/sq cm unit_dyn_cm2 10 Inches of Mercury Inch of Mercury in Hg unit_inHg 0.0002953 Pounds/Foot2 Pounds/Feet2 lb/sq ft unit_lb_ft2 0.020885434 Pounds/Inch2 Pound/Inches2 PSI unit_PSI 0.000145038 Tons/Foot2 Tonnes/Feet2 T/sq ft unit_T_ft2 1.04E-05 Tons/Inch2 Tonnes/Inch2 T/sq in unit_T_in2 7.25E-08 Torrs Torr unit_Torr 0.007500617 Kilograms/Meter2 Kilograms/Metre2 kg/sq m unit_kg_m2 0.101971621PowerWatts Watts W unit_W 1 British Thermal Unit/hour BTU/hour BTU/hr unit_BTU_hr 3.415179027 British ThermalBTU/minute BTU/min unit_BTU_min 0.05691965 Unit/minuteBritish ThermalBTU/second BTU/sec unit_BTU_sec 0.000948661 Unit/secondCalories/second Calorie/second cal/sec unit_cal_sec 0.239058511 Horsepower Horse power hp unit_hp 0.001341022 Pound-feet/minute Pound-foot/minute lb.ft/min unit_lb_ft_min 44.25372896 Pound-feet/second Pound-foot/second lb ft/sec unit_lb_ft_sec 0.737562149MassGrams Gram g unit_g 1 Carats Carat ct unit_ct 5 Grains Grain gr unit_gr 15.43235835 Ounces Ounce oz unit_oz 0.035273962 Ounces (Troy) Troy Ounce oz t unit_oz_t 0.032150748 Pennyweights Pennyweight dwt unit_dwt 0.643014931 Pounds Pound lb unit_lb 0.002204623 Pounds (Troy) Troy Pound lb t unit_lb_t 0.002679229 Stones Stone St unit_St 0.000157473Tons (metric) metric Tonne T (metric) unit_T_met 1.00E-06 Tons (imperial) english Tonnes T (imperial) unit_T_imp 1.10E-06LightLux Lux lx unit_lx 1 Flames Flame fl unit_fl 0.02322576 Footcandles Feetcandles fc unit_fc 0.09290304 Meter-candles Metre-candles mc unit_mc 1ForceNewtons Newton N unit_N 1 Gram Force Grams Force gf unit_gf 101.9716213 Joules/Centimeter Joules/Centimetre J/cm unit_J_cm 100 Joules/Meter Joules/Metre J/m unit_J_m 1 Ounce Force Ounces Force ozf unit_ozf 3.59694309 Pound Force Pounds Force lbf unit_lbf 0.224808943TemperatureCelsius deg C C unit_C 1 Fahrenheit deg F F unit_F 1.8 Kelvin deg K K unit_K 1TimeSeconds Second sec unit_sec 1 Centuries Century century unit_century 3.17E-10 Days Day da unit_da 1.16E-05 Decades Decade decade unit_decade 3.17E-09 Fortnights Fortnight fortnight unit_fortnight 8.27E-07 Hours Hour hr unit_hr 0.000277778 Leap-years Leap-year leap yr unit_leap_yr 3.16E-08Millenniums Millennium millennium unit_millennium 3.17E-11 Minutes Minute min unit_min 0.016666667 Months (30 days) Month (30 days) mon unit_mon 3.86E-07 Weeks Week wk unit_wk 1.65E-06 Years Year yr unit_yr 3.17E-08VolumeLitres Liters l unit_l 1 Inches3 Inch3 cu in unit_in3 61.02374409 Feet3 foot3 cu ft unit_ft3 0.035314667 Yards3 Yard3 cu yd unit_yd3 0.001307951 Cups Cup c unit_c 4.226752838 Gallons (US) Gallon (US) gal (US) unit_gal_us 0.264172052 Gallons (UK) Gallon (UK) gal (UK) unit_gal_uk 0.219969152 Meters3 Metre3 cu m unit_m3 0.001 Ounces (US) Ounce (US) fl oz (US) unit_fl_oz_us 33.8140227 Ounces (UK) Ounce (UK) fl oz (UK) unit_fl_oz_uk 35.19506424 Pints Pint pt unit_pt 2.113376419 Quarts Quart qt unit_qt 1.056688209 Tablespoons Tablespoon tbsp unit_tbsp 67.6280454 Teaspoons Teaspoon tsp unit_tsp 202.8841362Volume - DryLitres (Dry) Liters l (Dry) unit_l_dry 1 Barrels Barrel bbl unit_bbl 0.008648489 Bushels (Dry) Bushel (Dry) bu unit_bu 0.028377592 Pecks Peck pk unit_pk 0.113510368 Pints (Dry) Pint (Dry) pt (Dry) unit_pt_dry 1.81616588 Quarts (Dry) Quart (Dry) qt (Dry) unit_qt_dry 0.90808294分享到:•上一篇:杂七杂八•下一篇:可变参数。

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2 ˆh Kh n dh
h1 K h

A
25 10.107.0.68/~jgche/ 倒格子和第一Brillouin区 注意,面间距是与晶面指数而不是密勒指数相关
倒格子与Bravais格子的几何关系
• 由倒格矢与晶面面间距的关系 • 自原点O引晶面族法线N,截取P使 OP 2 / d
• 作变量替换,r’=r+Rl,就有
FK h 1 i ( K h r ' K h R l ) F (r ' )e dr ' V iK h R l F e iK h R l 1 iK h r ' dr ' e F (r ' )e Kh V
1
10.107.0.68/~jgche/
特别强调:晶面指的是格点所在平面
• 右图是金 刚石的原 子排列结 构:即图 中的球是 原子,而 不是格点 • 问:(001) 晶面族最 靠近原点 的是哪个 晶面?
10.107.0.68/~jgche/ 倒格子和第一Brillouin区

2
本讲目的:引入倒空间的有关概念
Rl Rl
l
• 格点满足平移周期性,则有Kh满足
K h R l 2m
• 那么乘上不变因子
10.107.0.68/~jgche/
k e
Hale Waihona Puke Rl i k K h R l
倒格子和第一Brillouin区
12
• 利用Poisson求和公式,即可得 k e i k K R k K h
b2 b3 a1 2 b1 (b 2 b 3 ) b 3 b1 a 2 2 b1 (b 2 b 3 )
a 3 a1 b 2 2 a1 (a 2 a 3 )
b1 b 2 a1 a 2 a 3 2 b 3 2 b1 (b 2 b 3 ) a1 (a 2 a 3 ) • 有些教科书也将这个关系作为倒格子基矢定 义,即由这三个矢量可以定义倒格矢,倒格矢 给出的端点集合构成倒格子 • 互为倒正,即正格子也可看作倒格子的倒格子
10.107.0.68/~jgche/ 倒格子和第一Brillouin区
15
倒格子基矢?
• • • •
R l l1a1 l2a 2 l3a 3 对正格子 代入 K h R l l1K h a1 l2 K h a 2 l3K h a 3 2m 如果选择一组b,使 b i a j 2 ij 那么矢量K就可由b组成 K h h1b1 h2b 2 h3b 3
10.107.0.68/~jgche/ 倒格子和第一Brillouin区
13
在正空间,格矢Rl端点(格点)的集合就 是格子;那么,矢量Kh端点的集合 呢?
10.107.0.68/~jgche/
倒格子和第一Brillouin区
14
2、倒格子(reciprocal lattice)
• 定义:对Bravais格子中所有的格矢Rl,有一系 列动量空间矢量Kh ,满足 iK h R l
倒格子和第一Brillouin区
8
V (r ) Vatom r R l
只是一个数学变换
l
(r ) atom r R l
l
• 势能、电荷密度等满足迭加原理的物理量 F (r ) f r R l
l
• 如果晶体具有平移周期性 R l R m R n
• 即
FK (1 e
h
iK h R l
)0
K h R l 2m, m整数
FK h 0
e
iK h R l
1
• 即如有平移周期性,那么一定在Fourier空间存在 Kh矢量满足这个关系
10.107.0.68/~jgche/ 倒格子和第一Brillouin区
10
问题是:这个Kh矢量有什么意义?
24
倒格子和第一Brillouin区
倒格矢的长度与面间距
• 设晶面(h1h2h3)的面间距为d • 则最靠近原点的晶面到原点的距离即OA在面 方向上的投影 a1 K h
d
C B O
Kh
a1 h1b1 h2b 2 h3b 3 h1 h1b1 h2b 2 h3b 3 2 2 Kh Kh dh
10.107.0.68/~jgche/ 倒格子和第一Brillouin区
18
Kh端点的集合构成倒空间中的Bravais格子
• 倒格矢
K h h1b1 h2b 2 h3b 3
• 满足平移对称
K h K h ' K h"
• 倒格子原胞体积,是正格子原胞体积的倒数, 可得
(2 ) b1 (b 2 b 3 )
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倒格子和第一Brillouin区
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Kh=h1b1+h2b2+h3b3与晶面(h1h2h3)正交
• 注意不是密勒指数(hkl),晶面指数(h1h2h3)。即 该晶面族最靠近原点晶面的截距分别为a1/h1, a2/h2, a3/h3 • 证明:
C B O
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正(坐标)空间
• 数学:(正)格子 • 观察:显微镜?
周期性
倒(动量)空间
• 观察: X射线衍射 • 数学:倒格子
r r r r r r r
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数学变换
倒格子和第一Brillouin区
k?
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坐标空间中用格矢(Rl)描写晶体平移周 期性;那么,在动量空间呢?
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• b i a j 2 ij 表示什么? • 是正交关系!即b1与a2和a3正交! • 看a2和a3确定的平面,即a2×a3 矢量垂直于该平面
* b1与a2和a3分别正交!
a 2 a3
a3
a2
• 即矢量b1与矢量a2×a3平行!因此,可设 b1 a 2 a 3 • 确定η可利用正交关系,就有 a1 b1 a1 a 2 a 3 2
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倒格子和第一Brillouin区
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为什么要倒(k)空间?
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1、晶格的Fourier变换
• 一个物理问题,既可以在正(坐标)空间描写, 也可以在倒(动量)空间描写
* 坐标表象r,动量表象k
• 为什么选择不同的表象?为什么动量空间?
e
1
K h R l 2m,
m为整数
的全部端点Kh的集合,构成该Bravais格子的 倒格子,这些点称为倒格点, Kh称为倒格矢 • 因此,Bravais格子也称为正格子(direct lattice) • 等价关系:知道Kh,就知道Rl;反过来也一样 • 它们满足Fourier变换关系,因此,倒空间也称 Fourier空间
h l
Rl
Kh
• 即当矢量Kh与Rl乘积是2π的整数倍时,在坐 标空间Rl处的δ函数的Fourier变换为在动量空 间以Kh为中心的δ函数! • 这告诉了我们什么信息,Kh对应什么?
* 坐标空间里,δ(r-Rl)函数表示在Rl的格点,当满足 上述条件时,其Fourier变换也是δ(k-Kh)函数,表 示坐标空间几何点的Fourier变换也是几何点! * 或者说前面Kh与Rl的关系定义了倒空间矢量,Kh的 量纲为Rl的倒数
* 则是Rl的周期函数 F (r R l ) F (r )
h
• 可对其作Fourier展开 • FKh称为Fourier系数
F (r ) FK h eiK h r
* 两边乘共轭因子 e iK h r 后积分可得这个系数
1 1 i K h ' K h r iK h r F (r )e dr FK h ' e dr V V h'
1. 为什么要倒(动量)空间? 2. 晶格的平移周期性,在动量空间如何描写?
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倒格子和第一Brillouin区
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第9讲、倒格子和第一Brillouin区
1. 晶格的Fourier变换 2. 3. 4. 5. 倒格子 正、倒格子对应的几何关系 重要的例子 第一Brillouin区
a
2b 2a
2 ˆ b1 i a 2 ˆ b2 j b
视野拓展 正格子和倒格子之间的关系
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3、正、倒格子对应的几何关系
• 不同空间描写晶体的对称性
r空间 Bravais格子 W-S原胞
k空间 倒格子 第一Brillouin区
* 适当地选取一个表象,可使问题简化、容易处理 如电子在均匀空间(特例=自由电子)运动,虽然 坐标一直变化,但k守衡,这时在坐标表象当然 不如在动量表象简单 * 衍射实验的理论基础 在量纲上,坐标空间和动量空间互为倒数,因此 也把坐标和动量空间分别称为正、倒空间;其他 也沿用这种称谓
10.107.0.68/~jgche/ 倒格子和第一Brillouin区
1 iK h r F ( r ) e dr FK h V
倒格子和第一Brillouin区
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仅当Kh’=Kh时,这个 9 积分不为零,且等于 V
• 因为F(r)= F(r+Rl),就有
FK h
1 1 iK h r iK h r F ( r R ) e dr F ( r ) e d r l V V
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