Marked signal improvement by stochastic resonance for aperiodic signals in the double-well
嗅质的嗅觉与味觉区别
Behavioral/Systems/CognitiveProcessing of Odor Mixtures in the Zebrafish Olfactory Bulb Rico Tabor,Emre Yaksi,Jan-Marek Weislogel,and Rainer W.FriedrichDepartment of Biomedical Optics,Max Planck Institute for Medical Research,D-69120Heidelberg,GermanyComponents of odor mixtures often are not perceived individually,suggesting that neural representations of mixtures are not simple combinations of the representations of the components.We studied odor responses to binary mixtures of amino acids and food extracts at different processing stages in the olfactory bulb(OB)of zebrafish.Odor-evoked input to the OB was measured by imaging Ca2ϩsignals in afferents to olfactory glomeruli.Activity patterns evoked by mixtures were predictable within narrow limits from the component patterns,indicating that mixture interactions in the peripheral olfactory system are weak.OB output neurons,the mitral cells(MCs),were recorded extra-and intracellularly and responded to odors with stimulus-dependent temporal firing rate modulations.Responses to mixtures of amino acids often were dominated by one of the component responses.Responses to mixtures of food extracts,in contrast, were more distinct from both component responses.These results show that mixture interactions can result from processing in the OB. Moreover,our data indicate that mixture interactions in the OB become more pronounced with increasing overlap of input activity patterns evoked by the components.Emerging from these results are rules of mixture interactions that may explain behavioral data and provide a basis for understanding the processing of natural odor stimuli in the OB.Key words:olfaction;odor mixture;information processing;olfactory glomerulus;mitral cell;neural circuitIntroductionOlfaction is considered a“synthetic”sense because the ability to segment the perception of odor mixtures into distinct compo-nents is limited(Laing and Francis,1989;Livermore and Laing, 1996).The perception of an odor mixture either is dominated by an intense component or acquires a new quality(Moskowitz and Barbe,1977;Laing and Willcox,1983;Laing et al.,1984,1989; Bell et al.,1987;Staubli et al.,1987;Derby et al.,1996;Valentincic et al.,2000;Wiltrout et al.,2003).Thus,responses to odorants are assumed to“interact”in the response to a mixture,giving rise to a neural representation that discards information about individ-ual components but acquires mixture-specific properties.Such mixture interactions may be important for the processing of nat-ural odor stimuli.Chemicals are detected by olfactory sensory neurons(OSNs), each of which expresses one ofϾ1000odorant receptors(ORs)in rodents(Malnic et al.,1999;Mombaerts,1999;Zhang and Firest-ein,2002).OSNs expressing the same odorant receptor converge onto distinct olfactory glomeruli(Ressler et al.,1994;Vassar et al., 1994;Mombaerts,1999).Odor quality initially is represented in the olfactory bulb(OB)by a combinatorial activity pattern across glomeruli,each of which responds to multiple odors(Stewart et al.,1979;Lancet et al.,1982;Friedrich and Korsching,1997; Rubin and Katz,1999;Fuss and Korsching,2001;Wachowiak and Cohen,2001).The principal neurons of the OB,the mitral cells(MCs),receive input from OSNs and interact via local inter-neurons.Synaptic connections within the OB shape the tuning profiles of MCs and temporally pattern their responses.Interactions between components in a mixture may occur at different stages of odor processing.In OSNs,mixture interac-tions have been observed in vertebrates and invertebrates and may be mediated by competitive inhibition or synergistic activa-tion of odorant receptors or by cross-talking signal transduction pathways(Ache et al.,1988;Laing et al.,1989;Ache and Zhain-azarov,1995;Kang and Caprio,1997;Cromarty and Derby,1998; Spehr et al.,2002).Mixture interactions also have been observed in the OB(Kang and Caprio,1995;Giraudet et al.,2002;Wilson, 2003);however,the origin of the interactions has remained un-known.A2-deoxyglucose study suggested that mixture interac-tions occur primarily in the periphery(Bell et al.,1987),although evidence exists for central mixture interactions in the spiny lob-ster(Derby et al.,1985).It is therefore unclear how neural circuits in the brain contribute to the processing of odor mixtures.More-over,understanding the processing of natural odor stimuli would be facilitated by a set of rules describing the effect of mixture interactions on odor-evoked activity patterns.We examined binary mixture interactions in the OB of adult zebrafish,which is similar to that of other vertebrates but con-tains relatively few glomeruli and MCs(Baier and Korsching, 1994;Byrd and Brunjes,1995;Edwards and Michel,2002).Bi-nary mixture interactions were studied in patterns of afferent glomerular activity and in MC odor responses,representing OB input and output activity,respectively.Significant interactions were observed in MC responses,but not their input activity pat-terns,indicating that the OB contributes to the processing ofReceived May12,2004;revised June9,2004;accepted June10,2004.This work was supported by the Max Planck Society,the Deutsche Forschungsgemeinschaft,and a fellowshipfrom the Boehringer Ingelheim Fonds to E.Y.We thank Gilles Laurent for generous support and Hartwig Spors forcomments on this manuscript.Correspondence should be addressed to Dr.Rainer Friedrich,Max Planck Institute for Medical Research,Depart-ment of Biomedical Optics,Jahnstrasse29,D-69120Heidelberg,Germany.E-mail:Rainer.Friedrich@mpimf-heidelberg.mpg.de.J.-M.Weislogel’s present address:Interdisciplinary Center for Neurosciences,University of Heidelberg,D-69120Heidelberg,Germany.DOI:10.1523/JNEUROSCI.1834-04.2004Copyright©2004Society for Neuroscience0270-6474/04/246611-10$15.00/0The Journal of Neuroscience,July21,2004•24(29):6611–6620•6611odor mixtures.Tentative rules for mixture interactions in the OB were derived and provide a basis for understanding the effect of mixture interactions on odor representations by multiple neurons.Materials and MethodsAnimals and loading of OSNs with a Ca2ϩindicator.Adult zebrafish (Danio rerio)were obtained from a local supplier or from a laboratory colony and kept at22–26°C.Loading of OSNs with calcium green-1 dextran(10kDa;Molecular Probes,Eugene,OR)was performed as de-scribed(Friedrich and Korsching,1997).Briefly,ϳ1l of6–8%calcium green-1dextran in3m M NaCl and0.1%Triton X-100was applied into each naris under anesthesia with0.01%MS-222.After5min the dye solution was washed away,and the fish were allowed to recover.Triton X-100transiently permeabilized olfactory cilia,allowing uptake of the dye.Cilia regenerated during the next48hr(Friedrich and Korsching, 1997).Fish were used for imaging experiments3–6d after dye loading. Surgery and odor stimulation.An explant of the intact zebrafish brain and nose was used in all experiments and prepared as described (Friedrich and Laurent,2001,2004).Briefly,fish were cooled to4°C and decapitated in teleost artificial CSF(ACSF)(Mathieson and Maler, 1988).The eyes,jaws,and bones over the ventral forebrain were removed to expose the ventral OBs.The preparation was placed ventral-side up into a custom-made flow chamber,continuously superfused with ACSF, and allowed to warm up to room temperature(ϳ22°C).In some imaging experiments that used an inverted microscope,brain structures caudal to the optic chiasm were removed,and the preparation was placed ventral-side down in a chamber with a coverslipped window in the floor as described(Friedrich and Korsching,1997).All animal procedures were performed in accordance with the animal care guidelines issued by the Federal Republic of Germany.Odors were delivered through a constant carrier stream directed at the ipsilateral inflow naris by a computer-controlled,pneumatically actuated HPLC injection valve(Valco,Houston,TX,or Rheodyne,Rohnert Park, CA).The time course of the odor stimulus was measured by imaging the efflux of a fluorescein solution from the delivery tube.The stimulus rose to maximum concentration withinϳ600msec and persisted forϳ2.4 sec.The stimulus time course was highly reproducible.Amino acids (Sigma,St.Louis,MO,or Fluka,Neu-Ulm,Germany)were of the highest purity available.Fresh stock solutions(1or10m M)were prepared at least every10d,refrigerated,and diluted to final concentrations of10–40M immediately before the experiment.Food extracts were prepared from commercially available flake food or from commercially available dried tubifex,daphnia,or blood worms.Stock solutions were made at least every14d by incubating200mg of fish food in50ml of ACSF for1hr and filtering through filter paper.Stock solutions were kept refrigerated and diluted1:10to1:100immediately before the experiment.The dilution factor was chosen so that the peak Ca2ϩsignals evoked by food extracts and amino acid stimuli were similar.Seven different foods were used.In all experiments the concentration of each component was the same when applied alone or in the mixture.Odor applications were separated by at least105sec to exclude sensory adaptation.Stimuli did not saturate glomerular responses because higher concentrations evoked larger Ca2ϩsignals in most glomeruli(Friedrich and Korsching,1997).Ca2ϩimaging.Specimens were viewed either with an inverted micro-scope(Zeiss Axiovert100,Oberkochen,Germany)equipped with a10ϫair objective[numerical aperture(NA)0.5;Zeiss]or with a custom-made upright epifluorescence microscope that used a BX-RFA epifluorescence condenser(Olympus,Tokyo,Japan)and a20ϫobjective(NA0.95; Olympus).Fluorescence was excited with a150W xenon arc lamp equipped with a stabilized power supply(Opti Quip,Highland Mills, NY)through an excitation filter(495/30HQ).Light was attenuated to 1.5%of the full intensity by neutral density filters to minimize photo-bleaching.Emitted light was projected through a dichroic mirror (Q520LP)and emission filter(HQ545/50)onto the chip of a CCD cam-era(CoolSnapHQ,Photometrics,Tucson,AZ).Images were binned to a final resolution of130ϫ174pixels and digitized at12bits and2–16Hz. Each pixel value in an image series was converted to a value representing the relative change in fluorescence(⌬F/F)after stimulus application.The baseline fluorescence(F)was calculated by averaging over the frames before stimulus onset.No bleach correction was performed,because bleaching was minimal and a correction would introduce additional noise.Response maps were obtained by averaging⌬F/F frames over2–4 sec after response onset and mild spatial filtering(Gaussian filter ofϭ1.2pixels;width,5pixels).The signal-to-noise ratio was substantially higher in experiments performed with the upright microscope and the 20ϫ,NA0.95objective.Quantitative analysis therefore was restricted to these experiments(nϭ35).However,results obtained with the inverted microscope(nϭ22experiments)were qualitatively indistinguishable. Electrophysiology.Axoclamp2B amplifiers(Axon Instruments,Foster City,CA)in bridge mode were used for all recordings.Intracellular whole-cell patch-clamp recordings(nϭ13cells)were performed with borosilicate pipettes(12–18M⍀).The pipette solution contained(in m M)130K-gluconate,10Na-gluconate,10Na-phosphocreatine,4NaCl, 4Mg-ATP,0.3Na-GTP,10HEPES,pH7.25.Mitral cells in the superfi-cial layers were approached under visual control by using differential interference contrast(DIC)optics and contrast-enhanced video display.Ex-tracellular recordings were performed in the loose-patch or cell-attached configuration.In cell-attached recordings(nϭ7)the pipettes(12–18M⍀) were filled with intracellular solution,and MCs were approached under visual control.Loose-patch recordings(nϭ32)were done as described (Friedrich and Laurent,2001,2004)by using pipettes filled with ACSF(9–12 M⍀).Results obtained with the three different recording methods were indistinguishable.In total,responses to57stimulus sets(components and mixture)were recorded from52MCs.The maximum number of stimulus sets tested on a single MC was three.Each odor stimulus was repeated,on average,6Ϯ3times.Responses of the same neuron to the same stimulus were averaged in peristimulus time histograms(PSTHs)with100msec bin width.A stimulus presented early during the experiment usually was re-peated at a later time to ensure the stability of responses(Friedrich and Laurent,2004),or stimuli were interleaved.Prediction of the mixture response from Ca2ϩimaging data.Presynaptic glomerular Ca2ϩsignals were,with very few exceptions,positive-going and increased monotonically with stimulus concentration until satura-tion(Friedrich and Korsching,1997).Because of these properties,the algorithm explained in Figure1was used to predict mixture responses from the component responses.Often,relatively large regions in the activity map showed no detectable odor response.To minimize the in-fluence of the noise in these regions on the quantitative analysis,pixel values of⌬F/FϽ0.4%were set to zero and excluded from quantitative analysis.This threshold corresponds toϳ2SDs of the average pixel noise (0.21Ϯ0.07%⌬F/F;nϭ35experiments).The average pixel noise was determined in subtractions of two response maps measured in the ab-sence of odor stimulation.When the response to one component is below response threshold or saturating,the mixture response would be expected to be equal to the response to the more potent component alone;i.e.,the superposition term(see Fig.1)should be zero.This is achieved by using the geometric mean in the calculation of the superposition term.The disadvantage is, however,that the geometric mean can rectify noise;when no real re-sponse increase occurs in a pixel between1and2ϫconcentration(be-cause the stimulus is below threshold or saturating),noise can lead to small negative difference values in the terms⌬2ϫ–1ϫResp OdorX(see Fig.1).The multiplication then yields a positive value,thereby biasing the prediction to more positive values.This effect is relatively small and occurs primarily in nonresponsive regions.Nevertheless,to avoid this, negative difference values in⌬2ϫ–1ϫResp OdorX(see Fig.1)were set to zero.Statistical comparisons.All statistical comparisons were performed by using a nonparametric Wilcoxon rank sum test.All given error values are SDs.ResultsMeasurement of odor responses in sensory afferents tothe OBOdor-evoked activity in sensory afferents to glomeruli was mea-sured by Ca2ϩimaging after OSNs were loaded with calcium6612•J.Neurosci.,July21,2004•24(29):6611–6620Tabor et al.•Odor Mixture Processinggreen-1dextran(Friedrich and Korsching,1997).Experiments were performed in a ventrolateral region of the OB that contains small,densely packed glomerular structures responding prefer-entially to amino acids and nucleotides(Friedrich and Korsching, 1997,1998).Odor application to the nose evokes distinct patterns of fluorescence signals in the OB,reflecting changes in Ca2ϩconcentration in OSN axonal terminals(Friedrich and Korsch-ing,1997;Fuss and Korsching,2001;Wachowiak and Cohen, 2001;Wachowiak et al.,2004)(see Fig.2A1–A4).Application of the carrier solution alone did not evoke detectable signals(data not shown).As shown previously(Friedrich and Korsching, 1997),the time courses of odor-evoked Ca2ϩsignals were similar and stereotyped throughout the observed region.This is consis-tent with odor responses of single zebrafish OSNs recorded elec-trophysiologically:OSN responses follow a stereotyped phasic–tonic time course,and the pattern of activity across multiple OSNs does not change much during odor stimulation(Friedrich and Laurent,2001,2004).Maps of Ca2ϩsignals,therefore,were time averaged.Negative-going responses were very rare,consis-tent with the low abundance of inhibitory electrical responses in zebrafish OSNs(Friedrich and Laurent,2004).Responses of glo-merular units have odor-and glomerulus-specific thresholds and increase monotonically with concentration over several log units until saturation(Friedrich and Korsching,1997).Analysis of mixture interactions in sensory afferents tothe OBThe monotonicity of concentration–response functions and the very rare occurrence of negative-going responses are reminiscent of concentration–response curves describing ligand–receptor in-teractions.We therefore used a simple algorithm based on mod-els of ligand–receptor activation to predict afferent patterns of Ca2ϩsignals evoked by binary odor mixtures from the patterns evoked by their components(Fig.1).This algorithm assumes that components(ligands)do not interact and activate a common effector(receptor)associated with each glomerulus.The strength of activation of a given glomerulus by a given ligand is described by the corresponding concentration–response function.Local information about concentration–response functions was ob-tained by measuring responses to components at the concentra-tion used in the mixture(1ϫ)and at twice that concentration (2ϫ).The minimum signal expected in response to the mixture isthe signal elicited by the more potent component at the1ϫcon-centration(Max1ϫ;Fig.1).Added to this signal is the signal in-crement expected from the second component(Superposition term;Fig.1).This is approximated as the geometric mean of the signal increase between1ϫand2ϫconcentrations for each com-ponent.The geometric mean was used because it yields correct values when the concentration of one component is below re-sponse threshold or saturating(i.e.,when the concentration–re-sponse function has a slope near zero;see Fig.1and Materials and Methods).The calculation yields three values:a conservative lower bound(Max1ϫ),a conservative upper bound(Max2ϫ;the signal elicited by the more potent component at2ϫconcentra-tion in each pixel),and the prediction(Fig.1).The difference between lower and upper bounds is usually small relative to the absolute response magnitude,because a twofold concentration change is small relative to the dynamic range and affects activity patterns only slightly(see below).The prediction error arising from uncertainties in the concentration–response function therefore is also small.Nevertheless,the prediction by the geo-metric mean is an approximation;precise knowledge of the con-centration–response function would be required to construct an exact algorithm.Moreover,the calculation of the prediction ac-cumulates noise in the data,arising,for example,from shot noise and the low amount of bleaching.To minimize these effects,we included only those pixels in which the response(⌬F/F)was Ͼ0.4%in the analysis.We first examined glomerular Ca2ϩsignals in response to single amino acids,which are natural odors for fish and other aquatic animals.Concentrations used were10–40M,which are intermediate in the behaviorally relevant range(Carr,1988).Fig-ure2A1–A4shows Ca2ϩsignal maps evoked by two amino acid components at1and2ϫconcentrations in the ventrolateral OB, thresholded at⌬F/Fϭ0.4%.From these responses the bounds and the prediction were calculated pixel-wise and compared with the actual mixture response.The lower and upper bounds(Fig.2A5,A6)were only slightly different from each other.The prediction(Fig.2A7)was very similar to the measured mixture response(Fig.2A8).Responsive regions in the pattern evoked by the mixture corresponded to those in the prediction,and similar distributions of response magnitude were observed in the two maps.The sum of the com-ponent patterns(Fig.2A9)did not predict response patternsas Figure1.Schematic illustration of the algorithm for prediction of afferent activity patterns evoked by a binary odor mixture.The algorithm assumes that both components stimulate the same effector site with different potency and potentially also with different concentration–response functions.The algorithm requires that negative responses do not occur and that con-centration–response functions are rmation about the full concentration–re-sponse functions is not required,but information about the local slope of the functions is sufficient.Thisinformationwasobtainedbyapplyingeachcomponentofabinarymixturealone at the concentration used in the mixture(1ϫ)and at twice that concentration(2ϫ).In each pixel a lower bound for the expected response to the mixture is given by the larger of the⌬F/F values evoked by the two components at1ϫconcentration,Max1ϫ(Odor1,Odor2),whereas an upper bound is given by the larger of the⌬F/F values evoked by the two components at2ϫconcentration,Max2ϫ(Odor1,Odor2).The prediction is calculated by adding a“superposition term”to the lower bound.The superposition term represents the expected signal increase over thelowerboundbecauseofthesecondcomponent.Itiscalculatedasthegeometricmeanofthe increase in Ca2ϩsignal between1ϫand2ϫconcentration for each odor(⌬2ϫ–1ϫResp Odor1 and⌬2ϫ–1ϫResp Odor2).Using the geometric mean ensures that the algorithm performs cor-rectlywhentheslopeoftheconcentration–responsefunctionforoneorbothodorsisnearzero. Nevertheless,thecalculatedpredictionisanapproximation,ratherthanaprecisecalculation,of the expected signal in response to the mixture.Tabor et al.•Odor Mixture Processing J.Neurosci.,July21,2004•24(29):6611–6620•6613well.This was expected,because it did not take into account the nonlinearity of con-centration –response functions.Figure 2A10depicts the difference be-tween the mixture response and the pre-diction.Negative and positive deviations from zero were encoded by opposite col-ors.Deviations were small relative to the overall response magnitude (note differ-ent calibration of color scales)and ap-peared to be only slightly greater than de-viations between maps evoked by repeated applications of the mixture (Fig.2A11).Similar results were obtained in n ϭ33experiments.The deviation between the mixture re-sponse and the prediction was quantified in 18experiments performed under con-ditions of low photon noise (see Materials and Methods).The differences in pixel val-ues between the prediction and the actual mixture response are shown as histograms in Figure 2C .Similar distributions were measured in two consecutive series of ap-plications (Fig.2C ,blue and cyan,respec-tively),indicating that responses were sta-ble.The widths of these distributions,quantified by the SD of a Gaussian fit to the histogram,were not significantly dif-ferent from each other (p Ͼ0.65;Fig.2D ).These distributions were slightly but sig-nificantly broader than the distribution of difference values for repeated mixture re-sponses (Fig.2C ,red,D ).Activity maps evoked by repeated responses to the mix-ture were therefore more similar to each other than to the prediction.These results were confirmed by using the correlation coefficient as a measure of similarity.Themean correlation between the prediction and the mixture response was 0.89Ϯ0.06for the first series of stimuli and 0.88Ϯ0.09for the second set of stimuli (not sig-nificantly different;p Ͼ0.8),whereas the mean correlation between maps evoked by repeated mixture applications was slightly but significantly higher (0.93Ϯ0.06;p Ͻ0.05).The slightly higher similarity between repeated mixture responses could indicate a significant deviation of the prediction from the mixture response.However,it is likely that this deviation is at least partially a consequence of the calculation of theprediction,because the prediction is not exact and because theprocedure accumulates noise.Moreover,the correlation betweenmixture responses and prediction was high,and the average dif-ference between the SDs of the Gaussian fits was 0.05Ϯ0.03%⌬F /F .This value is very small compared with the ⌬F /F values inthe response maps.We therefore conclude that afferent glomer-ular responses to binary mixtures of amino acids are predictablewithin narrow limits by a model assuming no interactions be-tween components.We next measured afferent glomerular activity in response to different food extracts,each containing many different com-pounds.These complex stimuli evoked widespread glomerular activity.As a consequence,patterns of Ca 2ϩsignals evoked by different food odor stimuli overlapped greatly (Fig.2D1–D4).Nevertheless,responses to binary mixtures of food extracts were in large part predictable from the component responses by the algorithm that was used.As for amino acids,lower and upper bounds were similar to each other and to the prediction(Fig.Figure 2.Patterns ofafferent glomerular activity evoked by binary odor mixtures and their components.A1–A4,Maps ofafferent glomerular Ca 2ϩsignals in the ventrolateral OB,evoked by two amino acid components at 1ϫand 2ϫconcentration.Lateral is to the bottom;anterior is to the right.A5–A7,Lower bound,upper bound,and prediction (see Fig.1)as calculated from A1–A4.A8,Measured response to the mixture.A9,Sum of component activity patterns at 1ϫconcentration (A1ϩA3).A10,Difference between mixture response and prediction (A8–A7).A11,Difference between response maps evoked by two repeated applicationsofthemixture.Theleftcolorscaleappliestodifferenceimages(A10,A11)andtherightcolorscaletoallotherimages.B ,Distribution of pixel values in difference images,averaged over n ϭ18experiments with binary amino acid mixtures in which the full set of stimuli was applied twice.Blue,Difference between response map evoked by the mixture and the prediction;cyan,same for a second set of applications;red,difference between response maps evoked by the mixture in repeated applications.C ,Quantification of the width of distributions of pixel values in difference images.In each of n ϭ18experiments the width of the distribution of pixel values in difference images was measured as the SD of a Gaussian fit.Error bars show the average SD for each typeofdifferencemap.ThesignificanceofdifferencesinmeanSDisshownbysymbolsineachbar.*p Ͻ0.05;**p Ͻ0.01;ns,notsignificant.The top row of significance symbols is for comparison between each of the bars to the first (left)bar and the bottomrow for comparisons to the second bar.D ,Same display as in A for a binary mixture of food extracts.E ,F ,Same plots as in B ,C for binary mixtures of food extracts (n ϭ17).Scale bars,100m.6614•J.Neurosci.,July 21,2004•24(29):6611–6620Tabor et al.•Odor Mixture Processing2D5–D7).The prediction,but not the sum of the activity maps of the component,was a close approximation of the true response to a binary mixture of food extracts(Fig.2D7–D11).Similar results with mixtures of food extracts were obtained in nϭ24 experiments.Quantitative analysis of the deviation of the prediction from the mixture response,as described above,was performed for17 experiments performed under low-noise conditions(see Materi-als and Methods).The pixel value differences between prediction and mixture response were not significantly different for re-peated series of stimuli(pϾ0.8;Fig.2E,blue and cyan,F).As for amino acids,these distributions were slightly but significantly broader than the distributions of differences between repeated mixture responses(Fig.2E,red,F).The average correlation be-tween the prediction and the mixture response was0.92Ϯ0.06 for the first series of stimuli and0.91Ϯ0.07for the second set of stimuli(pϾ0.8).These values were not significantly different from the mean correlation of responses to repeated mixture ap-plications(0.95Ϯ0.03;pϾ0.06).Hence,as with amino acid stimuli,the correlation between mixture response and prediction was high,and the average difference between the SDs of Gaussian fits was very small(0.02Ϯ0.05%⌬F/F).Thus,responses to binary mixtures of complex food odor stimuli are also predictable within narrow limits by a model assuming no interactions.Finally,we tested whether the small deviation between the pre-diction and the response to the mixture depended on the overlap between the component activity patterns.However,the deviation of the mixture from the prediction,quantified by the difference in the width of difference distributions,was not correlated with the corre-lation between the component activity patterns(amino acids,rϭ–0.17;pϾ0.5;food extracts,rϭ–0.19;pϾ0.45).Together,these results indicate that mixture interactions between the tested simple and complex stimuli in the peripheral olfactory system of zebrafish are,at most,weak.Mitral cell odor responsesWe next examined odor responses of the output neurons of the OB,the MCs.MCs were recorded extracellularly in the loose-patch or cell-attached configuration or were recorded intracellu-larly by the whole-cell patch-clamp technique.Unlike OSNs, MCs frequently respond to odors with inhibition.Moreover,MC firing rates often are modulated over tens or hundreds of milli-seconds and can comprise successive excitatory and inhibitory epochs.In addition,a subset of mitral cell responses showed sub-threshold membrane potential oscillations of20–30Hz(Fig.3) (Friedrich and Laurent,2001,2004).Mitral cell response patterns to the same odor do not change abruptly as a function of concen-tration and are usually similar over concentration ranges of more than one log unit(R.W.Friedrich,unpublished observations).The complex response properties arise from synaptic interac-tions in the OB,indicating that MC responses do not simply relay their glomerular input but also reflect dynamic processing by neural circuits in the OB.The temporal patterning and the occur-rence of inhibitory responses preclude the prediction of mixture responses by simple models of receptor–ligand interactions.We therefore compared MC odor responses by using methods that take into account their temporal response patterns.Mixture interactions in mitral cell responses:simple odors We first examined responses to amino acids and their binary mixtures.Figure4A shows responses of one MC,recorded extra-cellularly.In this example the response to component1was clearly excitatory,whereas the response to component2was in-hibitory.The response to the mixture was excitatory,with a mag-nitude and time course almost identical to the response to com-ponent1.Hence,the response to the mixture was dominated by the response to the excitatory component.Figure4B shows data from another MC that also responded with clear-cut excitation to one and with clear-cut inhibition to another component.In this case the response to the mixture was dominated by the inhibitory component.In each of18experiments testing mixtures of one clearly excitatory and one clearly inhibitory component,one component dominated over the other in the response to the mix-ture.In83%of the cases(15of18)the dominant component was the excitatory one,whereas in the remaining17%of the cases(3 of18)the inhibitory component dominated.In another18experiments that used amino acid stimuli, components evoked more complex responses that often dif-fered mainly in their temporal patterns.In the example shown in Figure4C,the responses to both components were excita-tory but had different,odor-specific time courses.The re-sponse to the mixture was dominated by one of the compo-nent responses and was clearly distinct from the response to the other component.A dominance of one componentalso Figure3.Examplesofmitralcellodorresponsestoaminoacidsandfoodextracts.Shownare whole-cell recordings of mitral cell responses to different amino acids(left column)and food extracts(right column).Each response is from a different mitral cell.Both types of stimuli can evoke simple(phasic–tonic;top)and more complex(multi-phasic)response time courses.Fast subthreshold membrane potential oscillations are seen in a subset of odor responses.Odor stimulus is indicated by the horizontal bar.Vertical bars,20mV.Tabor et al.•Odor Mixture Processing J.Neurosci.,July21,2004•24(29):6611–6620•6615。
利用迈克耳逊干涉仪测气体折射率实验报告
利用迈克耳逊干涉仪测气体折射率实验报告英文回答：Introduction。
The Michelson interferometer is a device that can be used to measure the refractive index of a gas. It consists of two arms of equal length, each of which is terminated by a mirror. A beam of light is split into two beams, and each beam is sent down one of the arms. The beams are then reflected back by the mirrors and recombined. If the refractive index of the gas in one of the arms is different from the refractive index of the gas in the other arm, the beams will be out of phase when they are recombined, and this will produce an interference pattern.Procedure。
I set up the Michelson interferometer and aligned themirrors so that the beams were recombining in the center of the screen. I then introduced a sample of gas into one of the arms and observed the interference pattern. I measured the distance between the bright bands and used this to calculate the refractive index of the gas.Results。
利用迈克耳逊干涉仪测气体折射率实验报告
利用迈克耳逊干涉仪测气体折射率实验报告英文回答：Determination of Refractive Index of Gas Using Michelson Interferometer。
The Michelson interferometer is a versatile tool that can be used to measure various optical properties of materials, including the refractive index of gases. In this experiment, we employed the Michelson interferometer to determine the refractive index of an unknown gas sample.The Michelson interferometer consists of two mirrors, M1 and M2, mounted on a rigid frame in a configuration known as the "common path interferometer." A beam of light from a coherent source is split into two beams using asemi-transparent mirror, M3. One beam travels to mirror M1, while the other travels to mirror M2. The beams are then reflected back to the semi-transparent mirror, where theyrecombine to produce an interference pattern.The interference pattern is typically observed as a series of bright and dark fringes. The position of these fringes depends on the optical path length difference between the two interfering beams. By introducing a cell containing the gas sample into one of the arms of the interferometer, the optical path length is changed, resulting in a shift in the fringe pattern.The change in the fringe pattern can be used to determine the refractive index of the gas sample. The refractive index is a dimensionless quantity that describes the speed of light in a medium relative to its speed in vacuum. A higher refractive index indicates that the light travels slower in the medium.The refractive index of the gas sample can be calculated using the following formula:```。
合成生物学_山东大学中国大学mooc课后章节答案期末考试题库2023年
合成生物学_山东大学中国大学mooc课后章节答案期末考试题库2023年1.标准化是所有工程学科的关键部分。
答案:正确2.生物安全包括哪些方面？答案:合成生物的泄露对研究人员造成的伤害_合成生物的泄露对公共环境造成的伤害_用合成生物技术发动生化战争3.单输入和多输入都是串联结构。
答案:正确4.关于核糖体结合位点的叙述，错误的是：答案:核糖体结合位点可以启动基因的转录。
5.现代生命科学的发展历史上，所经历的3次革命是：答案:合成生物学革命_基因组学革命_分子生物学革命6.单输入SIM的特点是，子模块表达的顺序与其功能相吻合。
答案:正确7.能与阻遏蛋白相结合的调控序列，叫做答案:operator8.分解代谢的中间产物，经常对代谢途径具有正反馈作用。
答案:正确9.当细胞对某种物质的需求量较高时，通常采用前馈的调节方式。
答案:错误10.“或”门逻辑的一致性前馈C1-FF结构，对于上升刺激的影响具有延迟效应，但对下降刺激的影响，则没有延迟效应。
答案:错误11.关于生物模块（biological module）叙述错误的是：答案:生物模块在细胞内，是与Part、Device和System并列的一个层次结构。
12.合成生物学是汇聚研究范式的典型。
答案:正确13.合成生物学工程化的研究策略中涉及的概念有：答案:抽提_解耦_标准化14.相比于基因工程，合成生物学又拓展出的一些工具包括：答案:抽提_标准化_DNA的从头合成15.合成生物学在生物医药领域里的应用体现在哪些方面：答案:个体化医疗_免疫细胞设计_开发天然药物_开发生产疫苗16.常见的装置的种类有：答案:基因开关_逻辑门_接收器_蛋白质生成装置17.下列哪些是组合型Part (composite part) ?答案:蛋白质生成装置_转换器18.与基因工程相比较，合成生物学的特点包括：答案:学科交叉的特点_网络分析是其核心内容之一_广泛使用数学模拟工具_标准化零件的特点19.一个标准的生物砖（BioBrick），其前后缀之间不能含有EcoRI酶切位点。
激发光强度 英文
激发光强度英文The excitation of light intensity can be achieved through various methods, such as using a high-powered laser or a strong light source. This can cause the atoms of a material to become excited and emit light at a higher intensity. Another way to increase light intensity is by using optical amplifiers, which can boost the strength of the light signal.In addition, the use of reflective materials or surfaces can help to enhance the intensity of light by reflecting and concentrating the light in a specific direction. This can be particularly useful in applications where a high level of light intensity is required, such as in scientific research or industrial processes.Furthermore, the design of optical systems can also play a crucial role in maximizing light intensity. By carefully engineering the components of an optical system, such as lenses, mirrors, and filters, it is possible to optimize the transmission and concentration of light, leading to a higher intensity of light output.Moreover, advancements in technology have led to the development of specialized light sources, such as LEDs and lasers, which are capable of emitting light at extremely high intensities. These light sources can be used in a wide range of applications, including medical imaging, telecommunications, and industrial manufacturing.In conclusion, there are various methods andtechnologies available to increase the intensity of light. By utilizing high-powered light sources, optical amplifiers, reflective materials, and advanced optical system designs,it is possible to achieve a higher level of light intensity for a wide range of applications.激发光强度可以通过多种方法实现，例如使用高功率激光或强光源。
拉雷尔电子有限公司产品说明书
LAUREL ELECTRONICS, INC.4-20 mA & Serial Output Transmitter for Resistance Input in OhmsFeatures•4-20 mA, 0-20 mA, 0-10V or -10V to +10V transmitter output, 16 bits, isolated•RS232 or RS485 serial data output, Modbus or Laurel ASCII protocol, isolated•Dual 120 mA solid state relays for alarm or control, isolated•Five precalibrated resistance input ranges from 20.000 Ω to 200.00 kΩ•Fixed 2.0000 ohm, 2.0000 MΩ and 20.000 MΩ range available as a factory specia• 1 mΩ resolution on 20 Ω scale•Custom curve linearization for changing resistance transducers•2, 3 or 4-wire connection with lead resistance compensation•Analog output resolution 0.0015% of span (16 bits), accuracy ±0.02% of span•DIN rail mount housing only 22.5 mm wide, detachable screw-clamp connectors•Universal 85-264 Vac / 90-300 Vdc or 10-48 Vdc / 12-32 Vac powerDescriptionThe Laureate Resistance Transmitter is factory calibrated forfive jumper selectable resistance ranges from 20 Ω to 200 kΩ.Fixed factory-special ranges of 2.000 Ω, 2.0000 MΩ and 20.000MΩ are also available. Accuracy is an exceptional 0.01% of fullscale ± 2 counts. Resolution is one part in 20,000. In the 20 Ωrange, resolution is 1 mΩ, making the transmitter suitable forcontact resistance and conductance measurements.Transmitter connections can be via 2, 3 or 4 wires. With 4-wirehookup, 2 wires are used for excitation and two separate wiresare used to sense the voltage across the resistance to bemeasured, thereby eliminating any lead resistance effects. With3-wire hookup, the transmitter senses the combined voltage dropacross the RTD plus two excitation leads. It also senses thevoltage drop across one excitation lead, and then subtracts twicethis voltage from the combined total. This technique effectivelysubtracts the lead resistance if the excitation leads are the same.All resistance ranges are digitally calibrated at the factory, withcalibration factors stored in EEPROM on the signal conditionerboard. This allows ranges and signal conditioner boards to bechanged in the field without recalibrating the transmitter. Ifdesired, the transmitter can easily be calibrated using externalstandards plus scale and offset in software.Fast read rate at up to 50 or 60 conversions per second whileintegrating the signal over a full power line cycle is provided byConcurrent Slope (Pat 5,262,780) analog-to-digital conversion.High read rate is ideal for peak or valley capture and for real-timecomputer interface and control.Open sensor indication is standard and may be set up to indi-cate either upscale or downscale. Excitation is provided by thetransmitter.Custom curve linearization, available with the Extendedversion, makes this transmitter ideal for use with transducerswhose output is a changing resistance.Standard features of Laureate transmitters include:•4-20 mA, 0-10V or -10V to +10V analog transmitter output,isolated, jumper-selectable and user scalable. All selectionsprovide 16-bit (0.0015%) resolution of output span and 0.02%output accuracy of a reading from -99,999 to +99,999 countsthat is also transmitted digitally. Output isolation from signaland power grounds eliminates potential ground loop problems.•Serial communications output, isolated. User selectableRS232 or RS485, half or full duplex. Three protocols are userselectable: Modbus RTU, Modbus ASCII, or Laurel ASCII.Modbus operation is fully compliant with Modbus Over SerialLine Specification V1.0 (2002). The Laurel ASCII protocolallows up to 31 Laureate devices to be addressed on thesame RS485 data line. It is simpler than the Modbus protocoland is recommended when all devices are Laureates.•Dual solid state relays, isolated. Available for local alarm orcontrol. Rated 120 mA at 130 Vac or 170 Vdc.•Universal 85-264 Vac power. Low-voltage 10-48 Vdc or 12-32 Vac power is optional.Easy Transmitter programming is via Laurel's InstrumentSetup Software, which runs on a PC under MS Windows. Thissoftware can be downloaded from this website at no charge. Therequired transmitter-to-PC interface cable is available from Laurel(P/N CBL04).SpecificationsRange Resolution Accuracy Excitation Current0-2.0000 Ω 0-20.000 Ω 0-200.00 Ω 0-2000.0 Ω 0-20000 Ω 0-200.00 kΩ 0-2.0000 MΩ 0-20.000 MΩ 0.1 mΩ1 mΩ10 mΩ100 mΩ1 Ω10 Ω100 Ω1 kΩ±0.01% of range± 2 counts5 mA5 mA500 µA50 µA5 µA500 nA500 nA75 nASignal InputInput Resolution Input Accuracy Update Rate, Max 16 bits (65,536 steps)±0.01% of full scale ± 2 counts 50/sec at 50 Hz, 60/sec at 60 HzAnalog Output (standard)Output Levels Compliance at 20 mA Compliance at 10V Output Resolution Output Accuracy Output Isolation 4-20 mA, 0-20 mA, 0-10 Vdc, -10 to +10Vdc (user selectable) 10V (0-500Ω load)2 mA (5 kΩ load or higher)16 bits (65,536 steps)0.02% of output span plus conversion accuracy250V rms working, 2.3 kV rms per 1 minute testSerial Communications (standard)Signal TypesData RatesOutput Isolation Serial Protocols Modbus Modes Modbus Compliance Digital Addressing RS232 or RS485 (half or full duplex)300, 600, 1200, 2400, 4800, 9600, 19200 baud250V rms working, 2.3 kV rms per 1 min testModbus RTU, Modbus ASCII, Laurel ASCIIRTU or ASCIIModbus over Serial Line Specification V1.0 (2002)247 Modbus addresses. Up to 32 devices on an RS485 line w/o a repeater.Dual Relay Output (standard)Relay Type Load Rating Two solid state relays, SPST, normally open, Form A 120 mA at 140 Vac or 180 VdcPower InputStandard Power Low Power Option Power Frequency Power Isolation Power Consumption 85-264 Vac or 90-300 Vdc10-48 Vdc or 12-32 VacDC or 47-63 Hz250V rms working, 2.3 kV rms per 1 min test 2W typical, 3W with max excitation outputMechanicalDimensions MountingElectrical Connections 129 x 104 x 22.5 mm case35 mm rail per DIN EN 50022 Plug-in screw-clamp connectorsEnvironmentalOperating Temperature Storage Temperature Relative Humidity Cooling Required 0°C to 55°C-40°C to 85°C95% at 40°C, non-condensingMount transmitters with ventilation holes at top and bottom. Leave 6 mm (1/4") between transmitters, or force air with a fan.PinoutMechanicalQA Application with Relays in Passband ModeA deviation limit (50 mΩ in this example) is set uparound both sides of a setpoint. The relay closes (oropens) when the reading falls within the deviationband, and opens (or closes) when the reading fallsoutside of this band. This mode sets up a passbandaround the setpoint and can be used for contactresistance testing in a production environment.RTD HookupIn 4-wire hookup, different pairs of leads are used to apply the excitation current and sense the voltage drop across the unknown resistance, so that the IR drop across the excitation leads is not a factor.In 3-wire hookup, the transmitter senses the combined voltage drop across the unknown resistance plus two excitation leads. It also senses the voltage drop across one excitation lead, and then subtracts twice this voltage from the combined total. This technique effectively subtracts all lead resistance and compen-sates for ambient temperature changes if the two excitation leads are identical.In 2-wire hookup, the transmitter senses the combined voltage drop across the unknown resistance and both lead wires. The voltage drop across the lead wires can be measured by shorting out the resistance during transmitter setup, and this voltage is then automatically subtracted from the combined total. However, changing resistance of the lead wires due to ambient tempera-ture changes will not be compensated.Ordering GuideCreate a model a model number in this format: LT20R1Transmitter Type LT Laureate 4-20 mA & RS232/RS485 output transmitter Main Board 2 Standard Main BoardPower0 Isolated 85-264 Vac or 90-300 Vdc 1 Isolated 10-48 Vdc or 12-32 VacResistance RangeR0 0-20 ohms (factory special fixed range) R1 0-20 ohms R2 0-200 ohms R3 0-2 kohms R4 0-20 kohms R5 0-200 kohmsR6 0-2 Mohms (factory special fixed range) R7 0-20 Mohms (factory special fixed range)Note: The same signal conditioner board can be used for resistance and RTD temperature measurement.AccessoriesCBL04 RS232 cable, 7ft. Connects RS232 screw terminals of LT transmitter to DB9port of PC.CBL02 USB to RS232 adapter cable. Combination of CBL02 and CBL04 connectstransmitter RS232 terminals to PC USB port.。
开启片剂完整性的窗户(中英文对照)
开启片剂完整性的窗户日本东芝公司，剑桥大学摘要：由日本东芝公司和剑桥大学合作成立的公司向《医药技术》解释了FDA支持的技术如何在不损坏片剂的情况下测定其完整性。
太赫脉冲成像的一个应用是检查肠溶制剂的完整性，以确保它们在到达肠溶之前不会溶解。
关键词：片剂完整性，太赫脉冲成像。
能够检测片剂的结构完整性和化学成分而无需将它们打碎的一种技术，已经通过了概念验证阶段，正在进行法规申请。
由英国私募Teraview公司研发并且以太赫光（介于无线电波和光波之间）为基础。
该成像技术为配方研发和质量控制中的湿溶出试验提供了一个更好的选择。
该技术还可以缩短新产品的研发时间，并且根据厂商的情况，随时间推移甚至可能发展成为一个用于制药生产线的实时片剂检测系统。
TPI技术通过发射太赫射线绘制出片剂和涂层厚度的三维差异图谱，在有结构或化学变化时太赫射线被反射回。
反射脉冲的时间延迟累加成该片剂的三维图像。
该系统使用太赫发射极，采用一个机器臂捡起片剂并且使其通过太赫光束，用一个扫描仪收集反射光并且建成三维图像(见图)。
技术研发太赫技术发源于二十世纪九十年代中期13本东芝公司位于英国的东芝欧洲研究中心，该中心与剑桥大学的物理学系有着密切的联系。
日本东芝公司当时正在研究新一代的半导体，研究的副产品是发现了这些半导体实际上是太赫光非常好的发射源和检测器。
二十世纪九十年代后期，日本东芝公司授权研究小组寻求该技术可能的应用，包括成像和化学传感光谱学，并与葛兰素史克和辉瑞以及其它公司建立了关系，以探讨其在制药业的应用。
虽然早期的结果表明该技术有前景，但日本东芝公司却不愿深入研究下去，原因是此应用与日本东芝公司在消费电子行业的任何业务兴趣都没有交叉。
这一决定的结果是研究中心的首席执行官DonArnone和剑桥桥大学物理学系的教授Michael Pepper先生于2001年成立了Teraview公司一作为研究中心的子公司。
TPI imaga 2000是第一个商品化太赫成像系统，该系统经优化用于成品片剂及其核心完整性和性能的无破坏检测。
补偿光纤Michelson弱磁传感器相位漂移的新方法
补偿光纤Michelson弱磁传感器相位漂移的新方法33倪明环33,周晓军,于彦明(电子科技大学光电信息学院,四川成都610054)摘要:提出了基于谐波分析的相位补偿法,用以解决光纤Michelson弱磁传感器中由于环境因素如温度变化等引起相位漂移带来的输出信号衰落问题。
该方法对正交工作点附近相位变化非常敏感,利用干涉仪参考臂压电陶瓷(PZT)的反馈电压可有效地控制相位漂移。
实验表明:干涉仪相位变化小于1°;将高频调制磁场H m cosωm t加于干涉仪信号臂换能器上探测直流弱磁信号,传感器输出信号稳定性好,线性度优于1%,灵敏度达3.5×10-6rad/n T(H m=4000n T)。
关键词:光纤传感器;干涉仪;谐波分析中图分类号:TN253 文献标识码:A 文章编号:100520086(2006)0120058204N e w Method to Compensate the Phase Shift of Fiber Optic Michelson Interfero2 metric Weak Magnetic SensorN I Ming2huan33,ZHOU Xiao2jun,YU Yan2ming(College of Photo2electric Information,University of Electronic Science and Technology of China,Cheng2 du610054,China)Abstract:A new method to compensate the pha se shift in fiber optic Michelson interfero2 metric weak magnetic sensor based on harmonic analysis is propo sed to solve the signal fading problem of the sensor that arise s from environmental effects such as ambient tem2 perature fluctuations.The method is sensitive to the phase variation around the quadrature, and it can effectively control the phase shift by using a correction signal to piezoelectric ceramic in reference arm of the interferometer.Exp erimental re sults show that the pha se variation of the interferometer is le ss than1°.Applying a magnetic dither H m co sωm t to the magnet transducer in signal arm of the interferometer for detecting direct2current weak magnetic signals,the stable magnet field sensing signals are obtained,the magnetic sensi2 bility of the sensor is3.5×10-6rad/nT(H m=4000nT)and the linearity is better than 1%.K ey w ords:optical fiber sensor;interferometer;harmonic analysis1 引 言 干涉型光纤传感器具有灵敏度高、体积小和抗电磁干扰等特点[1],但它易受环境影响发生随机相位漂移,导致信号衰落及探测灵敏度降低[2],因此必须解决相位漂移问题。
Gas Clip Technologies 单气体胶带和SGC Plus 毒气探测器用户指南说明书
Single Gas Clip and SGC Plus User’s Manual Rev 2.06READ BEFORE OPERATION Gas Clip Technologies (GCT) Single Gas Clip and SGC Plus detectors are personal safety devices designed to detect the presence of specific toxic gases (Carbon Monoxide (CO) or Hydrogen Sulfide (H2S)) or Oxygen (O2) deficiency. Accordingly please ensure you have been properly trained on the use of the equipment and appropriate actions in the event of an alarm condition.WARNINGI f the detector is past the “Activate BeforeDate” on the package, please do not activate.D o not attempt part replacement orsubstitution as this could impair the intrinsicsafety rating and will void the warranty of theproduct.B efore daily use check the following:-Sensor and Audio ports are clear of anyobstructions i.e. debris or blockage-Perform the “Self-test” to ensure properoperation of visual, audible, and vibratingalarms-Confirm receipt of a check mark in theupper left hand corner signaling a successful“Self-test”C alibrate the O2 detector at least every 30days. Make sure to calibrate in a clean airenvironment. See O2 detector section forinstructions on calibration.B oth the CO and H2S versions of the SingleGas Clip and SGC Plus do not requirecalibration for the life of the product, howeverwe do recommend bump tests please seeour bump test recommendations below:B ump Test the detector periodically bychallenging the sensor with a knownconcentration of the target gas to bedetected. Recommended target gasconcentrations (H2S: 25 ppm, CO: 200ppm, O2: 18%). Bump Test can beperformed either manually or through theSGC Dock. If a manual test is to beperformed make sure to test in a clean airenvironment.I f a detector fails the Self-test or Bump Testplease discontinue use.T he detector contains a lithium battery thatmust be disposed of by a qualified recycler.D o not substitute internal components as thismay interfere with the intrinsic safety of thedevice.D o not attempt to replace the battery orsensor, this product is designed to bedisposable. Changing these components willvoid the warranty.I f you suspect any malfunction or have anytechnical problems please contact GCT at877-525-0808Activating the D etectorTo activate the d etector, press and hold down button forapproximately 5 seconds. Upon activation, the detector willvibrate, flash, and sound the audible alarm. A successfulactivation will display the life remaining in months on thedetector as 24 months.Display DetailsThe detector utilizes a special high viewing angle LCD that isdesigned to enhance the screen visibility. In the absence ofgas, it displays life remaining. In those cases where gas ispresent, the display will automatically shift to a display thatshows gas concentration and a battery icon.*Note the display mode can be changed in the IR Linksoftware with the "Sensor Reading" and "Life Remaining"user options.Warning: Users must familiarize themselves withthe icons in both non-alarm and alarm statesWarning: If the display is missing icons or cannotbe clearly read, please contact GCT immediatelyDay to Day UsagePrior to daily use, the detector will prompt the user to perform a self-test . T his process is a simple and effective way to ensure safe operation of the detector. During the self-test the audio, visual, and vibrating alarms are activated and the sensor is tested. Below is a step by step process for performing the test:Screen 1:When the “Test” Icon appears in the upper left hand corner, a self-test is required. Press the button on the front of the detector to perform the test. Screen 2:After pressing the button the following screen will appear. During the self-test ensure that the following occur: (1) t he detector emits one audible beep and vibrates , (2) all LED’s light up (3) a ll LCD display elements appear. Screen 3:After the full element LCD screen, thelow alarm and high alarm set points willbe displayed. Note these alarm setpoints can be adjusted using the IR LinkorSGCDock configuration options. Factory Standard Alarm Set Points: H2S: Low 10 ppm / High 15 ppm CO: Low 35 ppm / High 200 ppm O2: Min 19.5% / Max 23.5%Screen 7: (see A dditional Steps section for screen 4-6 displays)When a self-test is successful thedetector will turn to the original screen and display a check mark in place of where the test icon was previously displayed and one short audible beep will sound. The detector will by default prompt another “Self-test” in 20 hours from when the button was pressed. Note this value can be changed via the IR Link software anywhere from 8 to 20 hours. See the IR Link QuickReference Guide for further detail.Additional Steps:Above we outlined the most common screen configurationsh owever if the detector has been programmed via the IR Link , or has been exposed to gas , additional screens may appear Screen 4 (If applicable): If programmed with a “User ID”, after the alarm set points are displayed, a combination of numbers and or letters will scroll across the screen. This will be a max of 2 screens with a maximum character limit on the “User ID” of 6 characters. The “User ID” can be changed/modified via the IR Link software .Screen 5 (if applicable): If the detector has been exposed to gas exceeding the low alarm set point a value will appear with “max” next to it. This represents the peak value (highest) that the detector has seen. After this screen , there will be another screen displaying a value with hours, days, or months . T his represents the amount of time that has pas sed since the peak reading.Screen 6 (if applicable): After the peak reading and time passed since screens, a screen will appear with CLP. If the user presses the button down while this is displayed, the peak value on the detector will be reset. Note : while the value will be cleared on the display , the value will be held in the detector’s log. See the event log section for further details. This value can be cleared on the next screen.Failures/FAQ’sIf the self-test fails, the detector emits five shortbeeps and flashes before displaying “Test”. Repeat the self-test.If the self-test fails three (3) consecutive times the detector will enter a Fail Safe mode. Please contact GCT for a replacement detector. During normal operation, the battery iscontinuously monitored. If the battery is low for more than (3) hours the detector enters Fail Safe mode.If the battery self-test fails (5) consecutive times the LCD will display “EO5”. In case of an EO5 screen discontinue use and contact GCT for a replacement detector.A long with the battery, the sensor is continuouslymonitored during normal operation. If a problem with the sensor is detected, the screen will display “EO6”. In case of an EO6 screen, please discontinue use and contact GCT for a replacement detector.I f the detector is displaying “bUP”, the detector is either due for a bump test because of a scheduled test or has failed a bump test. Please refer to “Bump Test Interval” for more detail.I f the detector is displaying “EOL” i t has reached the end of its operating life. Please discontinue use.AlarmsAlarm Types:Screen DisplayDetailLOW ALARMAudible Alarm: One (1) slow beep every secondVisual Alarm: One (1) slow flash every secondVibrating Alarm: One (1) slow vibration every second HIGH ALARM and OVER LIMIT (OL) ALARMAudible Alarm: Two (2) fast beeps every secondVisual Alarm: Two (2) fast flashes every secondVibrating Alarm: Two (2) fast vibrations every second DETECTOR LIFECOUNTDOWN ALARM “EOL” Once the detector has less than One (1) month of liferemaining, the unit will switch to days remaining, when it is less than One (1) day remaining it will switch to hours remaining. Once the detector has Eight (8) hours remaining, it will begin to beep, flash, and vibrate intermittently. To end thealarms press the button down. Once the detector has reached the end of its operating life the display will show “EOL” (End Of Life).Alarm Set Points:Default factory set points:H2S: Low Alarm 10 ppm/High Alarm 15 ppm CO: Low Alarm 35 ppm/High Alarm 200 ppm O2: Low Alarm 19.5%/High Alarm 23.5%*Note these set points can be changed using the GCT IR Link. Please refer to the SGC IR Link documentation forfurther details. To display the detector alarm set points press the button on the front of the detector.U se caution when changing alarm set points. Confirm these levels with your company safety officer.D O NOT use IR communications when anexplosive atmosphere may be present.Event LogBy default the detector stores the last twenty five (25) alarm events. The system stores events by first in first out, i.e. the 26th event will replace the first event and so on. Thisinformation can be downloaded using the GCT IR Link. For each alarm event the detector records the following:•The detector serial number •Bump Test (Yes or No)•Life remaining on the detector •Number of self-tests performed •Number of events•Alarm Condition (Low, High, or OL)•Specific event date and time•Peak gas concentration in ppm or %.Bump Test Interval (bUP)Using the IR Link or GCT Manager, units can beprogrammed to alert the user if a bump test is due. This interval can be set anywhere from 1 to 365 days. *Note the unit default is to have no bump interval programmed. If a detector is due for a bump test, the unit display will alternate between the months remaining and “bUP”. In addition the unit will emit alternating flashes (left and right) every 5 seconds. And the “test” icon will remain even after a button push.This alert can be cleared by either placing the unit in a Clip Dock or, if the bump interval is set, by manually applying gas to the unit. To manually clear the alert, press the button down once and wait for the "GAS" to show on the display while the TEST icon flashes. The detector will wait for 45 seconds for the target gas to be applied, or a button press to skip the bump test. If the SGC is bumped while showing "GAS", then it will record as a bump test in the event log instead of as an exposure. If no gas is applied, it will return to the normal screen and will not record anything in the event log.2.06O2 Detector-Calibration G CT recommends users of the O2 Single Gas Clipto bump test the detector before using each day.Single Gas Clip Oxygen (O2) detector factory default willprompt the user to calibrate the detector every 30 days. The user will be prompted by the screen flashing CAL, please see calibration instruction below:Calibration InstructionsO nly perform O2calibration in normal air (20.9% Oxygen) that is free of hazardous gases.1.Press and hold down theyellow button for four (4)seconds2.The screen will display CAL and the O2 icon will flash in the lower left hand side3.After a successfulcalibration, the detector will emit one (1) beep, vibration and LED flash4.After an unsuccessful calibration, the detector will beep, flash, and continue to display calibration. If after a few failed calibration please contact GCT customer support at 877-525-0808CleaningThe detector can be cleaned with a soft damp cloth. Do not use solvents, soaps or polishes. A neutral cleaner, like Mat & Table Top Cleaner (by ACL Staticide ) may also be used. The sensor screen may be cleaned with a soft brush under clean, warm water. Return the filter to the detector once it has fully dried.Hibernation (SGC+ Only)When the SGC Plus is not used for extended period of time it can be turned off (Hibernated) to suspend the 24 month operation life countdown.SGC Plus Hibernation with the IR Link1.Check that you have installed the IR Link Software and the IR Link USB connections are plugged in2.Click Read Device on the IR Link Software3.Note when the monitor is hibernated the event log will be cleared. It is highly recommended to save the event log by pressing the save event log before hibernating.4.Click on the Hibernate Button, acknowledge the event log message5.Keep in front of the IR Link until the "Hibernate OK" message is displayed at the bottom of the IR Link Software6.Confirm the monitor screen is blank7.If you encounter any problems please contact GCT customer support at 877-525-0808SGC Plus Hibernation with the Clip Dock1.Check that the Clip Dock is turned on and USB memory is inserted 2.The Clip Dock is capable of hibernating 4 units at one time, place the desired amount of monitors in the docking station3.Press and hold the bump test and calibration buttons down simultaneously for approximately 2 seconds4.A successful hibernation will result in a GREEN light on for the corresponding unit number5.Note the event log will be automatically stored on the Clip Dock USB memory6.Confirm the monitor screen is blank7.If you encounter any problems please contact GCT customer support at 877-525-0808Instrument SpecificationsSize: 3.3 x 2.0 x 1.1 in. (85 x 50 x 28 mm.)Weight: 2.7 oz. (76 g)Temperature: -40 to 122°F (-40 to +50°C) for CO and H 2S, -31 to +122°F (-35 to +50°C) for O 2Humidity: 5% to 95% non-condensing relative humidityIngress Protection: IP 67Alarms: Visual, vibrating, audible (minimum 95dB) LEDs: 4 red alarm bar LEDsDisplay: Liquid Crystal Display (LCD)Battery Life: 24 months of operation/ 2 minutes of alarm per day.Event Log Storage: Last 25 events. Newer events replace older events.Warranty: Full 2 years (SGC) or 3 years (SGC+) Sensor Type: Single plug-in electrochemical cell User Options: User ID, Low Alarm, High Alarm,Calibration Interval, Bump Interval, Self-Test Interval, Calibration Gas, Display sensor/life remaining, Bump Due LEDApprovals: INMETRO : IEx 15.0058 Ex ia IIC T4 Ga (-40°C (H2S,CO) / -35°C (O2) ≤ Ta ≤ +50°C)Instructions S pecific toH azardous A rea I nstallations(in accordance with IEC 60079-0:2011 clause 30)The following instructions relevant to safe use in a hazardous area apply to equipment covered by certi cate numbers IECEx CSA 16.0020X and Sira 16ATEX2087X. 1. The certi cation marking is as follows:Ex ia IIC T4 Ga0518 II 1G2. The equipment may be used in zones 0, 1 & 2 with ammable gases and vapours with apparatus groups IIC and with temperature classes T1, T2, T3, T43. The equipment is only certi ed for use in ambienttemperatures in the range -40°C(H2S)/-40°C(CO)/-35°C(O2) ≤ Ta ≤ +50°C and should not be used outside this range 4. Installation shall be carried out in accordance with the applicable code of practice by suitably-trained personnel 5. There are no special checking or maintenance conditions other than a periodic check.6. With regard to explosion safety, it is not necessary to check for correct operation.7. The equipment contains no user-replaceable parts and is not intended to be repaired by the user. Repair of the equipment is to be carried out by the manufacturer, or their approved agents, in accordance with the applicable code of practice.8. Repair of this equipment shall be carried out in accordance with the applicable code of practice9. If the equipment is likely to come into contact with aggressive substances, e.g. acidic liquids or gases that may attack metals or solvents that may a ect polymeric materials, then it is the responsibility of the user to take suitable precautions that prevent it from being adversely a ected thus ensuring that the type of protection is not compromised.10. The certi cate number has an ‘X’ su x which indicates that special conditions of installation and use apply. Thoseinstalling or inspecting this equipment must have access to the contents of the certi cate or these instructions. The conditions listed in the certi cate are reproduced below:No precautions against electrostatic discharge arenecessary for portable equipment that has an enclosure made of plastic, metal or a combination of the two, except where a signi cant static-generating mechanism has been identi ed. Activities such as placing the item in a pocket or on a belt, operating a keypad or cleaning with a damp cloth, do not present a signi cant electrostatic risk. However, where a static-generating mechanism is identi ed, such as repeated brushing against clothing, then suitable precautions shall be taken, e.g. the use of anti-static footwear.Contact InformationGas Clip Technologies, Inc. 610 Uptown Blvd, Suite 4100 Cedar Hill, TX 75104Toll Free: +1 (877) 525-0808 Phone: +1 (972) 775-7577 Fax: +1 (972) 775-2483E-mail:********************Website: Limited WarrantyGas Clip Technologies (“GCT”) warrants this product to be free from defects in material and workmanship under normal use and service for a period of two years beginning upon the date of activation for all Single Gas Clip products and the SGC Plus monitor for 3 years from date of activation or 24 months of operational life, whichever occurs first. This warranty is valid only if the detector is activated by the date on package. This warranty extends only to the sale of new and unused products to the original buyer. GCT’s warranty obligation is limited, at GCT’s option, to refund of the purchase price, repair, or replacement of a defective product that is returned to a GCT authorized service center within the warranty period. In no event shall GCT’s liability hereunder exceed the purchase price actually paid by the buyer for the product. This Warranty does not include: (1) Fuses, disposable batteries, or routine replacement of parts due to the normal wear and tear of the product arising from use. (2) Any product which in GCT’s opinion, has been misused, altered, neglected or damaged by accident or abnormal conditions of operation, handling, or use. (3) Any damage or defects attributable to repair of the product by any person other than the authorized dealer, or installation of unapproved parts on the product. The obligations set forth in this warranty are conditional on: (1) Proper storage, installation, calibration, use, maintenance, and compliance with the user’s manual instructions and any other applicable recommendations of GCT. (2) The buyer promptly notifying GCT of any defect and, if required, promptly making the product available for correction. No goods shall be returned to GCT until receipt by the buyer of instructions from GCT. (3)The right of GCT to require that the buyer provide proof sale or packing slip to establish that the product is within the warranty period. The buyer agrees that this warranty is the buyer’s sole and exclusive remedy and is in lieu of all other warranties, express or implied, including but not limited to any implied warranty or merchantability or fitness for a particular purpose. GCT shall not be liable for any special,indirect, incidental, or consequential damages or losses,including loss of data, whether arising from breach of warranty or based on contract, tort, or reliance on any other theory. Some countries or states do not allow limitation of the term of an applied warranty, or exclusion or limitation of incidental or consequential damages, the limitations and exclusions of this warranty may not apply to every buyer. If any provision of this warranty is held invalid or unenforceable by a court of competent jurisdiction, such holding will not affect the validity or enforceability of any other provision.。
modis辐射定标参数
MODIS辐射定标参数主要包括增益(Gain)、偏置(Bias)和规模因子(Scale Factor)。
增益(Gain)：是指传感器输出信号与输入信号之间的比例关系。
增益参数用于调整传感器的灵敏度，以确保在不同的光照条件下，传感器能够输出适当的信号。
偏置(Bias)：是指传感器输出信号与输入信号之间的偏差。
偏置参数用于消除传感器的非线性输出，确保传感器输出的信号与实际输入信号之间的误差在最小范围内。
规模因子(Scale Factor)：是指传感器输出信号的缩放比例。
规模因子参数用于调整传感器输出信号的范围，以确保在不同的测量范围内，传感器能够输出适当的信号。
以上信息仅供参考，如有需要，建议您咨询专业人士。
signaling criteria use criteria
signaling criteria use criteria什么是信号标准和使用标准。
文章将介绍信号标准和使用标准的概念，解释它们的重要性，并提供详细的步骤来定义和应用这些标准。
第一部分：引言信号标准和使用标准在各个行业中都扮演着重要的角色。
它们有助于确保信号传输的一致性和可靠性，并提供一套规范来指导各种应用场景中的信号交互。
本文将深入探讨信号标准和使用标准的定义、重要性以及如何定义和应用这些标准的步骤。
第二部分：信号标准的定义和重要性信号标准是对信号传输中各个方面的规范化要求的描述。
这些标准通常包含一系列技术规范、协议和接口要求，以确保信号能够正确传递和解读。
信号标准的制定对于确保设备和系统之间的兼容性和互操作性至关重要。
信号标准的使用具有以下重要性：1. 可靠性：信号标准可以确保信号在传输过程中不受干扰或失真。
这些标准定义了适当的信号传输介质、传输速率、协议和错误纠正机制，以确保信号的准确传输和解析。
2. 一致性：信号标准提供了一套共同的规范，使各方能够使用相同的参数和接口进行信号交互。
这样可以确保不同设备和系统之间的信号传输方式一致，降低了协作和集成的成本和风险。
3. 互操作性：信号标准促进了设备和系统之间的互操作性。
使用相同的信号标准，不同的设备和系统可以相互通信和交换数据，从而促进信息的共享和集成。
第三部分：使用标准的定义和重要性使用标准是基于信号标准制定的一套规则和指南，用于在特定的应用场景中定义和应用信号标准。
使用标准的目的是确保信号在特定场景中的正确使用和解释。
使用标准的重要性如下：1. 规范化：使用标准提供了一套规范化的方法和步骤，用于定义和应用信号标准。
这些标准化的方法可以确保信号的一致性和可重复性。
2. 指导：使用标准为信号的定义和应用提供了明确的指导。
这些指导的步骤可以帮助用户遵循适当的流程和方法来使用信号标准。
3. 效率：使用标准可以提高工作效率。
由于使用标准减少了对个人经验和判断的依赖，因此可以更快地进行信号的定义和应用，并避免因个人差异引起的错误。
调节信英语作文模板
调节信英语作文模板Adjustment of the SignalSignal adjustment is a crucial process in ensuring smooth communication and efficient transmission of information. There are various factors that can affect signal quality, such as noise, interference, and distance. Therefore, it is important to properly adjust the signal to optimize its performance.One of the key ways to adjust a signal is by using amplifiers. Amplifiers are devices that increase the strength of a signal, making it easier to transmit over long distances or through obstacles. By adjusting the gain of the amplifier, the signal can be boosted to the desired level for clear and reliable communication.Another important aspect of signal adjustment is filtering. Filters are used to remove unwanted noise and interference from the signal, ensuring that only the desired information is transmitted. By adjusting the filter settings, the signal can be cleaned up and improved for better quality communication.In addition to amplifiers and filters, signal adjustment can also involve adjusting the modulation scheme. Modulation is the process of encoding information onto a carrier signal for transmission. By adjusting the modulation parameters, such as frequency, phase, and amplitude, the signal can be optimized for efficient transmission and reception.Overall, signal adjustment is a critical step in ensuring effective communication. By using amplifiers, filters, and modulation techniques, the signal can be adjusted to achieve the desired quality and reliability. It is important to carefully adjust the signal to overcome any obstacles and ensure smooth transmission of information.信号调节是确保顺畅沟通和高效信息传输的关键过程。
精神分裂症40 Hz听觉稳态反应缺陷研究进展
•综述•精神分裂症40 Hz听觉稳态反应缺陷研究进展王丽娜贾立娜潘伟刚马辛首都医科大学附属北京安定医院精神疾病诊断与治疗北京市重点实验室100088通信作者：马辛，Email:maxinanding@【摘要】目前已有大量证据支持7振荡活动在精神分裂症异常皮质环路中起着重要作用，并可能作为一个潜在的研究靶点。
近年来，听觉稳态反应作为研究精神分裂症异常振荡的电生理指标受到了广泛关注，有研究显示40 Hz听觉稳态反应缺陷与精神分裂症密切相关，故本文中对40 Hz听觉稳态反应与精神分裂症的相关研究做一综述。
【关键词】精神分裂症；诱发电位，听觉；7振荡基金项目：北京市科学委员会重大专项(D171100007017001〉Research progress of 40 Hz auditory steady-state response defect in schizophreniaW a n g L i n a,J i a L in a, P a n W e ig a n g, M a X inB e i j i n g K e y L a b o r a t o r y o f M e n t a l D i s o r d e r s, B e i jin g A n d i n g H o s p i t a l,C a p i t a l M e d i c a l U n i v e r s i t y, B e i j i n g100088,C h in aC o r r e s p o n d i n g a u t h o r:M a X in, E m a il:m a x i n a n d i n g@v i p.163.c o m【Abstract 】There is sound evidence to support the important role of gamma oscillatoryactivity in abnormal cortical circuits in patients with schizophrenia and it may be used as a potentialresearch target. In recent years, auditory steady-state response has received extensive attention asan electrophysiological indicator for the study of abnormal gamma oscillations in schizophrenia.Studies have shown that the 40 Hz auditory steady-state response defect is closely related toschizophrenia. Therefore, this article reviews the related studies on 40 Hz auditory steady-stateresponse and schizophrenia.【K eyw ords】Schizophrenia; Evoked potentials, auditory; Gamma oscillationFund program: Major Project of Beijing Municipal Science Commission (D171100007017001)精神分裂症是一种重性精神疾病，在我国的终生患病 率为0.6%m，临床表现主要为阳性症状、阴性症状以及认知 功能障碍等u]，因其高复发率、高致残率及高疾病负担的特 征，给患者的生活质量及社会稳定均带来不同程度的负面 影响。
电子美国电动机测试仪与分析仪 iTIG II 说明书
THE EASIEST TO USE TESTERS ON THE MARKETDELIVERING A COMPREHENSIVE TEST SETTHA T FINDS MORE FAUL TSiTIG IIThe iTIG II motor tester and winding analyzer combines multiple testing technologies from micro-ohm resistance to high frequency surge tests and partial discharge measurements into a single light weight portable instrument. From low voltage to high voltage, 20 different tests are available.Why Consider an Electrom Motor Tester?•Find more faults with state of the art high frequency surge test technology.-Customers find faults they do not find with other lower-frequency surge testers. •Get early warnings of insulation deterioration with Partial Discharge tests.-Fast, cost effective and no accessories needed.•The easiest tester to use according to our customers, manual to fully automatic models.•Powerful time saving trend analysis, reporting tools and data transfer options.•Modular construction, designed to be upgraded to higher level models withoutpurchasing a new tester.WHO USES ELECTROM MOTOR ANAL YZERS?The Electrom Instruments motor testers and winding analyzers are used worldwide throughout industries that use, service, repair, rewind and manufacture electrical rotating machinery, coils, transformers and sensors.Some Advantages for Industrial Users and Motor Repair CompaniesEasy to Use: According to our customers the iTIG II is the easiest tester to use. With automated models, each test can be done the same way every time regardless of operator. Preset test parameters and templates are available, and assembled motors can be surge tested without turning the rotor.Portable, Rugged & Light Weight: The iTIG II is the lightest fully automatic, 12kV and 15kV tester available. For even more portability see the iTIG II MINI with up to 6kV surge/hipot output.The PP-II is the only truly portable 45J 30kV POWER PACK at less than 50 lbs/23kg. It can be used with multiple iTIG II’s.Reports: Complete reports are automatically generated, named and stored by the tester with a click on the print button. They can also be generated on a rmation: Information is only entered once, and is organized well to meet both motor shop and industrial user needs.Motor Shops: Reports can be transferred to job number folders in Motor Shop Software directly from the tester via WiFi, VPN, or Ethernet.Reliability and Maintenance Programs: In addition to reports with multi-test graphs and tables, test results can be stored automatically in summary files that open in Excel or database software as a spreadsheet on a PC. Each row is a test set making trend analysis easy.VFD Issues: Diagnosis of operating problems in systems that use VFD power is greatly enhanced with offline Partial Discharge measurements done during a surge test.Training: DON’T USE THE TESTER OFTEN? Our training program will surprise you!Motor Manufactures and OEMsElectrom Instruments’ Production Line Test Automation Systems (PLTA) are based on advanced iTIG II technology. Test systems can include bar code scanning, external controls, automatic upload of test results to a server and more.Whether you manufacture motors, generators, alternators, reactors, various types of transformers, solenoids or anytype of coil, large or small, we may have a solution for your winding tests.iTIG II MINI & iTIG IIiTIG II & Power Pack IIiTIG IIiTIG II & Power Pack IIOUTPUTSThe iTIG II series of coil and motor testers come with max output voltages of 4kV, 6kV, 12kV, 12kV-H and 15kV-H. The H model has higher discharge capacitance, and can generate a higher voltage than the 12kV model when the 12kV is maxed out.Power Packs with maximum output voltages from 18kV to 30kV for testing large higher voltage motors and generators can be added at any time. Our Power Packs are the smallest most portable high voltage test sets available on the market. See Power Pack brochure.PORTABLE, MODULAR, BASIC TO AUTOMA TICThe iTIG II winding and motor analyzer is portable, light weight and rugged, designed for shop and field testing. It comes in basic to fully automatic versions.Not only high voltage tests can be part of an automated test sequence, but also high accuracy low voltage measurements such as:•µΩ resistance •Capacitance •Inductance •ImpedanceAll tests and measurements can be done through the high voltage lead set with the model D.All models can be upgraded to higher level models later, with more automation, more features and higher outputs. They can include production line automation software.REAL EASE OF USEApplication of advanced user interface design techniques and software algorithms creates an intuitive and easy to use Windows™ based tester - even with complex testing requirements. According to our customers it is the easiest to use tester they have seen.The many time saving features include:•Surge wave voltage range and sweep are automatically set, no need to hold buttons during any tests.•Time saving report generation done by the tester.•Automatically track test results over time for reliability and maintenance programs.•Assembled motor surge test without the need to turn the rotor.•Preset test templates with all test parameters and limits.•Single button multi-coil test capability and master coil comparisons.•Automated analysis features such as armature shorting bar pattern detection.•Push one button to have a series of tests done automatically, the same way every time.30kV Power Pack IISURGE AND HIPOT TESTSWith the iTIG II no manual lead switching is required. Once the operating voltage of the motor is entered, the high frequency surge tests, with IGBT generated fast rising pulses per IEEE 522, can be done automatically. There is no need to further adjust voltage range and sweep (or time base), it is all done by the tester.•Superior High Frequency Surge PulsesThe iTIG II is the only surge tester capable of generating fully automatic software-controlled surge voltage pulses at high pulse rates up to 50 Hz. This eliminates ionization dissipation present in low frequency surge testers such as those pulsing at 5Hz and lower. As a result, the iTIG II finds more cases of weak insulation and faults, and at lower voltages than low frequency testers.•Automatic Quick Surge™ and Surge Guard™Enables the user to push a button and let the iTIG II run the test with a controlled and limited number of pulses. Quick Surge™ and Surge Guard™ technology make the tests faster, and ensures the right number of surge pulses are applied for optimal performance.•Pulse to Pulse Surge TestThe PtoP surge test automatically raises the surge voltage in small steps at a pulse rate of about 20Hz. The voltage is raised to the design test voltage, and the % wave difference between steps is calculated at each step. The final L-L difference is also displayed. The picture has a graph of the results, one bar per voltage step. The tall bar shows a failure at about 1850V in phase 2.The test eliminates the need to turn rotors in assembled motors with rotor influence. It is also used in applications with normal differences in the phase-to-phase surge waves, such as with many concentric wound stators, and in applications where there are no other coils/phases to compare to.•Master Coil and Multi-Coil TestsThese modes make it easy to surge test a large number of any type of coil, DC armature or stator. Results can be displayed in multiple ways for easy analysis. The iTIG II D can be set up specifically as a single coil tester by the user, and can automatically surge test a single coil in both directions.•Manual or Automated IR, PI and DC Hipot TestsResults can be temperature corrected. Multi-point test graphs for PI, hipot step voltage and ramp tests, and comparisons to previous tests for trend analysis or pre/post repair results are available. An AC Hipot option up to 5kV is available with a separate unit that is controlled by the iTIG II. It uses the iTIG II output test leads. This integration allows AC Hipot to be included in automated test sequences.L-L Surge test failurePtoP surge test, tall bar = phase 2 failure3 Hipot step tests, breakdown in 3rd testDC Hipot test screenPARTIAL DISCHARGE CAPABILITYOffline PD measurements provide an early warning of insulation breakdown before a surge test, hipot test or online monitoring indicate an insulation breakdown or failure. It is a great tool to track the condition of equipment over time and can provide an opportunity to lengthen the life of a motor.In a motor shop or in the field, PD can be a tiebreaker in the determination of pass/fail, and can determine whether to schedule reconditioning /replacement or not.Partial Discharge tests can also be used to find problems in systems powered by inverter drives (VFD). In coil and rotating equipment manufacturing, partial discharge measurements are used for quality control to confirm that there is no PD or that the PD is below a certain level.HOW THE iTIG IIDOES PD MEASUREMENTSThe iTIG II does the partial discharge measurement during a surge test using capacitive coupling technology and advanced software algorithms. Repetitive PD Inception Voltage (RPDIV) and Extinction Voltage (RPDEV), and maximum Partial Discharge levels in mV are displayed and automatically stored.All the PD measurements can be part of a fully automatic sequence of tests that starts with winding resistance and impedance measurements, moves through IR and Hipot tests, and finishes with surge tests and PD measurements. The results can be compared to earlier results for trending or pre/post repair comparisons.Evaluation of PD results should take into account results from other tests. One can choose which PD measurements to include:Combining the surge test with a partial discharge measurement is a fast and cost-effective way to get PD measurements. No accessories, couplers or other gadgets are needed. All the required pieces are included inside the iTIG II motor tester.Only max PD is measured to quickly check if there is PD or not. In low voltage motors there should be no PD at normal surge test voltages.RPDIV, RPDEV and Max PD are included. A significant reduc-tion in the inception voltage (RPDIV) over time can indicate breakdown of the insulation before other signs of breakdown are detected.Learn more about PDWINDING RESIST ANCEWinding resistance is an important measurement because other testsand measurements will not find some of the problems a resistancemeasurement will. The measurement is used to find open windings,shorts to ground, wrong turn count, wrong wire gauge, resistiveconnections, round wire(s) in hand that are not connected in a coil,connection mistakes, resistance imbalance between phases, and insome cases shorted turns.4-wire measurementsAll iTIG II winding resistance measurements are done with a highlyaccurate 4-wire system using Kelvin clamp leads. The measurementscan be in milli-Ohms or micro-Ohms depending on the model.Temperature corrected resistance from a few μΩ to 2kΩ is available.DC Armature Equalization DetectionFor bar to bar resistance measurements on DC armatures, the iTIG IID will detect what percent equalization the armature has. If there aretwo levels of resistance it calculates an average for each level and themax delta between the high and low measurements for each level. Abar graph is created for the measurements, the averages are drawnand the faulty bars that exceed failure limits are colored differentlythan the rest of the bars. The ARP-02 4-wire resistance probes andμΩ measurement are required.IMPEDANCE MEASUREMENTS & ROTOR TESTSWhere more analysis is needed, for example for predictive maintenance, Electrom offers the CLZ option. It includes measurements of inductance, impedance and phase angle for windings and coils, and capacitance measured from the winding to ground. It also calculates Dissipation factor (D), also called Tan Delta, and Quality factor (Q).Rotors in assembled motors can be tested with the CLZ option using the “rotor influence check” or RIC test. This method checks squirrel cage rotors for broken rotor bars.2 resistance levels; out of spec results are redCheck for broken rotor barsµΩ measurement of 3-phase motorCapacitance, inductance & impedance resultsLearn moreWHA T TYPES OF TEST CAN BE DONEAND WHA T WEAKNESSES/FAILURES ARE FOUNDThe table shows some of the tests that can be done with the iTIG II winding analyzer. For some, test profiles can beprogrammed along with default settings and default test voltage formulas.Test Tips Surge:The only test that finds turn to turn faults that occur at high voltages, provides early warning if the fault is above peak operating voltage.PD: Partial Discharge test finds insulation weaknesses earlier than any other test, enables reconditioning before a failure occurs that requires rewinding.DC Hipot:Can find phase to phase weaknesses when the phases are disconnected.Step Voltage: Finds at what voltage the ground insulation starts to break down.IR (megohm): Mainly a contamination test; can include DAR and/or PI; PASS/FAIL informs whether ornot to perform high voltage tests.Low Resistance: The only test that will find resistive connections, round wire(s) in hand that are not connected in a coil, partial blowout of some coils, and more.RIC test: Inductance measurement can be used for rotor influence checks on assembled induction motors.•••••••DC MOTOR TEST ACCESSORIESATF-11: ARMATURE TEST FIXTUREThe ATF-11 is used to do SpanSurge Tests of DC motor armatures.A span test is done across multiplebars on the commutator. Requiresan FS-12 Foot Switch for easyoperation. Also very useful formulti-coil tests.ABT, ARMATURE BAR-TO-BAR SURGE TEST ACCESSORYUsed with the iTIG II B, C & D for:•Surge comparison tests bar-to-bar on armatures.Surge tests of single coils with very low inductancewhen the desired surge test voltage is below 1400V.•It is typically used with 12kV and 15kV iTIG II models.Max ABT Output: 1400VComes with the BBP bar to bar probe in the pictureand the FS-12 foot switch.FS-12: FOOT SWITCHFor starting tests and allowing hands off operation of theiTIG II surge tester. Works with all models.ASP SURGE PROBE-SETThe ASP is an optional and alter-native probe-set for the ABT. Itcan be used for bar to bar testsand span tests. The voltage me-asured is load dependent whenthe ASP is used. For accurate me-asurements of the test voltage inthe load itself, the BBP probe isused.This probe set also comes in a version that connects di-rectly to the iTIG II high voltage leads (ASP-22). This is analternative to the AFT-11 above.ARP: ARMATURE RESISTANCE PROBESThe ARP, 4-wire ResistanceProbes, are mainly used tomeasure the resistance bar-to-bar on armatures. Theycan also be used to measureresistance of other thingssuch as equalizers.The ARP is used with the C and D model iTIG II. MicroOhm (μΩ) measurements are required in most casessince bar-to-bar and equalizer measurements typicallyare below 1mΩ.The models come with the following resistancemeasurements:Model B: mΩ || C: mΩ, µΩ optional || D: µΩThe Model D has report software that automaticallygenerates reports with Pass/Fail results for each bar-to-bar measurement in a test-set. The results are presentedin a bar graph.If the armature equalization is uneven (for example33% or 66% equalized), the armature tester detects thepattern, adjusts accordingly, and calculates Pass/Failresults based on two resistance levels.•••DC MOTOR TESTINGDC motors are tested with the same instrument used for AC motor tests. The tests used are the same, but the test procedures are different. To make the tests easier, the iTIG II has dedicated user interface screens for DC motor tests. Multi-coil tests are available. Options for presentation of winding resistance and surge test data include bar graphs.TEST REPORTSReports can be generated automatically on the iTIG II with a click of the print button, stored, and be transferred to a PC/server at any time later.Reports can also be generated on a PC using the TRPro report software.Reports are easily customized to include a cover page, your logo and other info, both tabular and graphical views of all the different types of test data, for example:Pre and Post repair data can be included in one report.Pulse-to-Pulse surge data can include both bar charts and nested wave graphs (see picture below).Multi coil surge data can be presented in a summary bar chart and/or with detailed surge waveform graphs that can include other test results next to each surge graph.Hipot step test and PI graphs can include multiple tests to show trends and pre/post repair results.A rmature resistance values displayed in bar charts show data grouped by shorting-bar pattern.Your company logo is easily added to all report pages.Output formats include: printers, PDF, HTML and Microsoft Word TM format.Reports and screens on the testers are available in multiple languages.•••------••Failed L-L and PtoP surge test, one of multiple report pagesTREND ANAL YSIS CAPABILITIES• A full set of built in trend data tables and multi-test graphs for Megohm, PI and Hipot/Step Voltage tests is available.Results for each test set can be automatically stored in a line item test summary file. They can be transferred to aserver with one click of a button or automatically with the Export software.Transferred test summary files (test results over time) can be viewed in Excel or in a database program in a spreadsheet format. This makes trend analysis easy.DA TA TRANSFERMotor data, test data and complete reports can be exported from the iTIG II with one click transfers using flashdrives, Ethernet, Wi-Fi or VPN.•Transfers to a PC or server can be accessed by multiple people.Reports can go directly to job number folders in systems like MotorBase® and ACS.CUSTOMER OR MOTOR DA TABASE IMPORTWhen purchasing an ITIG II for the first time or for a new location, existing customer or plant data, motor or model data can be imported from databases or spreadsheets. This saves the operator time and eliminates entry mistakes and duplications.••••Some columns from the test summary CSV file. The file includes a total of 40 columns of data.Overview screen of test results, always available. Click tabs at the bottom to display results for each test. Repeat any individual testbefore the test set is closed.Customer and motor list screen, TRPro report program for PCs. Easily search for key data and sort the table by column heading, similar to the motor list screen in the iTIG II C & D.SPECIFICA TIONSHighest standards of instrumentation design.Providing superior measurement accuracy in all phases of testing.•High precision 4-wire μΩ winding resistance measurements through high voltage leads available.•High precision leakage current measurement.•Stable high precision high voltage generation.GET IN TOUCHIf you have any questions about our products or services, please do not hesitate to reach out to us or one of our trusted distributors around the world.For information on other Electrom products please visit our website. Or use the following links to find more information on the higher voltage Power Packs , and the even lighter and more portable iTIG II MINI .Toll free: 800.833.1881 (US, Canada, Caribbean)Tel: +1 720.491.3580Fax: +1 720.491.3533Email: *********************Address:1821 Lefthand Cir. Unit A Longmont, CO 80501USAAre you looking for a solution or are you interested in receiving more information? Click the button below and let us know.Contact usQuotes and informationiTIG II & 30kV Power Pack II iTIG II MINIGet info or a quote。
375 TRI-WING 螺丝刀用户手册说明书
EAN:4013288037046Size:178x33x33 mmPart number:Weight:56 gArticle number:375 TRI-WING®Country of origin:CZ82054000Customs tariffnumber:Screwdriver for TRI-WING® screwsMulti-component Kraftform handle for fast and ergonomic screwdrivingHandle markings simplify finding and sorting of toolsHexagonal anti-roll feature against rolling awayThe Wera Black Point tip offers an exact fit and optimum corrosion protectionHigh quality Kraftform Plus screwdriver. Multi-component Kraftform handle for fast and low-fatigue working. Kraftform Plus: hard gripping zones for high working speeds whereas soft zones ensure high torque transfer. The Wera Black Point tip offers optimised corrosion protection and an exact fit. The hexagonal anti-roll feature prevents any bothersome rolling away at the workplace. Handle markings for simplified finding and sorting of the tool.Web linkhttp://products.wera.de/en/tools_for_the_aerospace_segment_screwdrivers_screwdrivers_kraftform_plus__series_300_375_tri-wing.htmlThe TRI-WING® screwdriving systemKraftformRapid hand repositioningKraftform Plus screwdrivers –ergonomics you can grasp.They relieve the entire hand-arm system even when used intensively.Along with other technical and product advantages such as the Lasertip for a secure fit in the screw head,Kraftform screwdrivers are the ideal choice whenever manual screwdriving jobs are concerned.The TRI-WING®screwdriving system is mainly found in aviation and household technology (here e.g.on live components).The asymmetric arrangement of the three profile flanks prevents the use of anything other than the original tools.The high-precision Wera profile design ensures a secure fit of the tool in the head of the screw.The blades are manufactured out of bit material.The Wera know-how with regard to the hardening technology ensures a long service life of the tool.The basic idea for the prototype of the Kraftform handle –that the hand should dictate the design –has,right through to today,proved to be correct.In cooperation with the internationally recognised Fraunhofer IAO Institute,Wera developed a screwdriver handle designed to match the shape of the human hand as long ago as the 1960s.After a long development phase,the Wera Kraftform handle was launched to the market in 1968.It has been optimised through the years with new technologies,but has kept its proven shape.After all,the human hand has not changed either.The hard materials used for the handle ensure rapid hand repositioning without any danger of the skin “sticking"to the handle.The surrounding hard zones with large diameters glide like wheels across the hand.Large contact area Identification marking Non-roll featureWera Black Point tipThe large contact area –with particularly high friction to the soft zones –results in high torque transfer without any bruising from the edges.The screw symbol and tip size identification markings on the handle make it easier to find the right screwdriver in the tool case or at the workplace.The hexagonal non-roll feature prevents any rolling away at the workplace.The Wera Black Point tip and a refined hardening process ensure long service life of the tip,improved corrosion protection and an exact fit.Web linkhttp://products.wera.de/en/tools_for_the_aerospace_segment_screwdrivers_screwdrivers_kraftform_plus__series_300_375_tri-wing.htmlFurther versions in this product family:mm mm mm inch08081 3.5 3 1/818081 3.5 3 1/828098 4.5 3 1/838098 4.5 3 1/8410098 6.04510098 6.04Web linkhttp://products.wera.de/en/tools_for_the_aerospace_segment_screwdrivers_screwdrivers_kraftform_plus__series_300_375_tri-wing.html。
如何在Digi手机路由器上实现最大信号强度说明书
How to Achieve Maximum Signal Strengthwith Digi Cellular RoutersWhat tools do I have for determining signal strength?The best throughput comes from placing the device in an area with the greatest Received Signal Strength Indicator (RSSI). RSSI is a measurement of the Radio Frequency (RF) signal strength between the base station and the mobile device, expressed in dBm. The better the signal strength, the less data retransmission and, therefore, better throughput.•How do I read RSSI on the Digi cellular router?RSSI information is available from several sources:1. The LEDs on the device give a general indication (1-4 “bars”).2. Via the Digi device’s local user interface:http (Digi web interface > Information > System Info > Mobile)CLI command “display mobile” via telnet, SSH or local serial port connection (via HyperTerminal, TeraTerm or other emulation package) to the Digicellular router.3. Digi Connectware® Manager (Server Platform) can also display the value in dBmvia System Information screen.•What do the numbers mean?-101 dbm or less (0-1 LED) -> Unacceptable coverage-100 dbm to –91 dbm (1-2 LEDs) -> Weak Coverage-90 dbm to –81 dbm (2-3 LEDs) -> Moderate coverage-80 dbm or greater (4 LEDs) -> Good CoveragePre-install surveys can also be done using a data device such as Blackberry, Treo andeven cell phone. Check out this guide from WPS Antennas on how to use a cell phone fora basic site survey: /pdf/testmode/FieldTestModes.pdf.These data devices cannot provide a 100% reliable comparison to how a Digi cellularrouter will behave due to antenna differences, etc. Generally, if the other device worksokay, the Digi device should as well. As noted below, special antennas can usually helpin areas with marginal signal.What about placement?Placement can drastically increase the signal strength of a cellular connection. Often times, just moving the router closer to an exterior window or to another location within the facility can result in optimum reception.•Another way of increasing throughput is by physically placing the device on the roof of the building (in an environmentally safe enclosure with proper moisture and lightningprotection).o Simply install the device outside the building and run an RJ-45 Ethernetcable to your switch located in the building.o Keep antenna cable away from interferers (AC wiring).Antenna OptionsOnce optimum placement is achieved, if signal strength is still not desirable, you can experiment with different antenna options. Assuming you have tried a standard antenna, next consider: •Check your antenna connection to ensure it is properly attached. If you have the ConnectPort™ WAN VPN product, ensure the internal antenna connectors are alsoproperly connected.•Cabled antenna (Digi part # - DC-ANT-DBDT) has no dBm gain, but has 8-foot cable and magnetic base for attachment to metal ground plane.•High gain antenna (Digi part # - DC-ANT-DBHG), which has higher dBm gain and longer antenna.•Antenna boosters and directional antennas:o Companies such as sell signal enhancingtechnologies ranging from $100-$1000.Directional antennas are larger and take some time to set up but aretypically in the $150 price range. Also verify if the antenna is single- ordual-band. Single-band antennas require matching the signal from thecarrier. If you aren’t sure which frequency you carrier is using in aparticular location, you may contact WPS Antennas for assistance.Powered antenna boosters can be much more expensive, but are ofteneasier to set up.o Many cabled antennas require a metal ground plane for maximumperformance. The ground plane typically should have a diameter roughlytwice the length of the antenna.Does it help overall throughput to stack the devices at one location?No, do not stack multiple routers per location. Adding additional routers at the remote location will not increase throughput because the bottleneck becomes the limited EGPRS capable data timeslots allocated at the cell site. All data customers share the same timeslots. If you stack routers, you will simply be competing with yourself for data channels.NOTE:Another way of optimizing throughput is by sending non-encrypted data through the device. Application layer encryption or VPN put a heavy toll on bandwidth utilization. For example, IPsec ESP headers and trailers can add 20-30% or more overhead.Digi International ▪ 11001 Bren Road East ▪ Minnetonka, MN 55343 ▪ 952-912-3444 ▪*************©2006 Digi International Inc.。
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a r X i v :p h y s i c s /0511016v 1 [p h y s i c s .d a t a -a n ] 2 N o v 2005Marked signal improvement by stochastic resonance for aperiodicsignals in the double-well systemR´o bert Mingesz,Zolt´a n Gingl,and P´e ter MakraDepartment of Experimental Physics,University of Szeged,D´o m t´e r 9,Szeged,H-6720,HungaryAbstract On the basis of our mixed-signal simulations we report significant stochastic resonance induced input-output signal improvement in the double-well system for aperiodic input types.We used a pulse train with randomised pulse locations and a band-limited noise with low cut-offfrequency as input signals,and applied a cross-spectral measure to quantify their noise content.We also supplemented our examinations with simulations in the Schmitt trigger to show that the signal improvement we obtained is not a result of a potential filtering effect due to the limited response time of the double-well dynamics.1I.INTRODUCTIONHaving originated in the context of ice ages[1],stochastic resonance(SR)is nowadays often given a signal processing interpretation:noise aids a weak signal to surpass some kind of barrier in a system,which is then reflected in the noise content of the output of the system.As the most widely used measure of this noise content is the signal-to-noise ratio (SNR),one quantitative definition of SR may be a noise-induced optimisation of the output SNR.Stochastic resonance in itself means using noise to make the output less noisy than it would be without noise,yet the signal processing approach just mentioned impels one to to raise the question whether,in the framework of SR,noise can also make the output less noisy as compared to the input,similarly to the wayfilters do.This question has long intrigued researchers working in thefield of SR,and after a few unsuccessful attempts at the beginning,SR-induced input-output improvement has been demonstrated in a wide range of systems from a simple level crossing detector[2,3]and other static non-linearities[4] to the Schmitt trigger[5]and even dynamical systems such as neuronal models[6]or the archetypal double-well potential[7].To our present knowledge it seems unlikely that stochastic resonance will ever rivalfilters in technical applications designed to improve signal quality.Yet there may exist processes, like neural signal transfer,where SR represents the only viable method of amplifying sub-threshold stimuli,and a number offindings do point in this direction[8,9].As aperiodic signals are native in this class of processes,studying their role in SR-induced signal improve-ment is not at all without relevance.Quantifying the noise content of aperiodic signals poses a special problem,as the most widely used definition of the signal-to-noise ratio is valid in the strict sense only for harmonic signals,and even its wide-band extension depends on the condition of periodicity in the input signal.Several cross-correlational and cross-spectral measures have been in use in thefield of aperiodic SR to circumvent this problem;here we adopt the cross-spectral treatment used by L B Kish[2].In our present study,we apply a mixed-signal simulation environment to examine whether aperiodic signals—a randomised pulse train and a band-limited noise as signal—can also be improved by SR occurring in the archetypal double-well system.2II.MODELLING AND METHODSA.Measures of noise contentThefirst to introduce the technical notion of signal-to-noise ratio into SR research were Fauve and Heslot when reporting stochastic resonance in a real-world electronic device,the Schmitt trigger[10].SNR then became widely adopted as the quantifier of SR,most often taken in the following form to facilitate analytical treatment[11]:lim∆f→0 f0+∆f f0−∆f S(f)d fR:=∞0S N(f)d f.(2) This definition(to which,contrasting it to the narrow-band scope of the definition in Eq1, we refer as the wide-band SNR)is valid for non-sinusoidal periodic signals as well,and,as we have demonstrated in[7],it provides a much more realistic account of signal improvement even in the case of a sine input.For all measures of noise content,the chief difficulty lies in separating signal from noise. Sometimes,especially in the case of the narrow-band definition in Eq(1),this was carried out by recording the PSD of the output when noise was fed into the input without any signal. This method doubled the simulation workload,as each simulation step was to be repeated without input signal,while its validity was also questionable from a theoretical point of view,since it failed to take into account the cross-modulation between signal and noise which occurs due to the non-linearity inherent in systems showing SR.In most cases,when the background noise PSD is smooth,signal-noise separation may be simplified by taking the noisy spectra as a whole and calculating the PSD of the noise at the signal frequency (or the integer multiples of the signal frequency in the case of the wide-band definition)as3the average of PSD values in the neighbourhood of the spectral peak(excluding the peak itself,of course);the signal PSD is then the PSD at the spectral peak minus this averaged noise background.When the input signal is aperiodic,neither of the above-mentioned methods works,be-cause signal power is not concentrated at particular frequencies.This case calls for a more elaborate technique of signal-noise separation,which is usually based on either the cross-correlation(as,for example,in[12])or the cross-spectrum between the noiseless input and the noisy signal.Here we reach back to the treatment used in[2],and take the signal PSD at the output as the part of the total PSD which shows correlation with the noiseless input, reflected in their cross-spectrum:|S in,out(f)|2S sig out(f)=∞0S noi out(f)d f.(5) As we are interested in input-output signal improvement,we also need a cross-spectral SNR at the input:R cs,in:= ∞0S sig in(f)d f,(8)R w,in4andR cs,outG cs:==x(t)−x3(t)+p(t)+w(t),(10)dtwherein p(t)denotes the input signal and w(t)stands for the noise(a physical white noise—that is,having a limited bandwidth—in our case).Comparing the noise content of the input and output signals,we looked for a signal improvement induced by stochastic resonance.We applied a mixed-signal(ie,having both digital and analogue components)simulation system to realise the double-well potential and solve Eq(10).To obtain the solution of the latter,wefirst transformed it into an integral form:x(t)= t0 x(τ)−x3(τ)+p(τ)+w(τ) dτ.(11) We generated the input signal and the noise digitally,then converted them into analogue signals.All mathematical operations in Eq(11),such as addition,multiplication and inte-gration,were performed by analogue devices.The output of our analogue circuitry was the solution of Eq(11),which we then transmitted through an anti-aliasingfilter and converted back to the digital domain using high-resolution A/D converters.In order to avoid artefacts that might stem from different treatment,we used the very samefiltering and sampling unit to digitise both the input and the output.The simulation system was driven by a high-performance digital signal processor(DSP),under the control of a computer running LabVIEW,which also performed all evaluation tasks.Our mixed-signal simulation system is summed up in Fig1.It is worth noting that the analogue integrator introduces a1/(RC)factor into Eq(11), wherein R and C are the resistance and the capacitance in the integrator circuit.The output of the integrator is therefore not exactly the solution x(t)but1y(t)=Figure1:Our mixed-signal system realising the double-well modelwherein b:=RC/(1s).Substituting s:=τ·1/b,we see that the integrator transforms the time scale by a b factor:y(t)= t/b0 y(bs)−y3(bs)+p(bs)+w(bs) ds.(13) This means that the actual frequency scale in the analogue circuitry is1/b times the theo-retical frequency scale corresponding to Eqs(10)and(11).In our simulations,the value of b was1.2·10−4.We used three types of input signals in our simulations:the periodic pulse train for which we have already obtained high SNR gains in the double-well system[7],included here for the purposes of comparison between the wide-band and the cross-spectral gain,and two aperiodic signals,a pulse train with randomised pulse locations and a band-limited noise whose upper cut-offfrequency is much smaller than the bandwidth of the noise as stochastic excitation(see Fig2).In the case of pulse trains,we defined the duty cycle of the signal as 2τ/T,whereτis the pulse width and T is the period of the periodic pulse train.The parameters of our mixed-signal simulations are summarised in Table I.In the case of the randomised pulse train,we determined the peak locations randomly before starting the simulations and then used exactly the same waveform in each realisation during averaging, while the band-limited noise as signal was generated anew in each averaging step.We also determined the threshold amplitude A T experimentally as the minimum signal amplitude at which switching between wells can occur without noise,and expressed the signal amplitude6Figure2:The input signals we used:periodic pulse train,aperiodic pulse train and a band-limited noiseParameter Aperiodic pulses0.9A TPulse width N/A10%Standard deviation0.31A T39Hz/4.68·10−3HzBandwidth*39Hz/4.68·10−3Hz5kHz/0.6HzSampling frequencyLength of samplesCycles per sample N/Abetween10and50Table I:The parameters of the simulations.The frequency values marked with*are measurable on two different frequency scale(as discussed above):thefirst value is the analogue frequency and the second is the corresponding theoretical value.A T denotes the threshold amplitudeand the standard deviation of the noise as normalised by this threshold.III.RESULTSFirst,for the purposes of validation we compared the two kinds of gains(G w and G cs)for a periodic pulse train,in which case both are valid measures and they should theoretically yield the same results.Indeed,Fig3shows that the difference between them is negligible.7Figure3:The wide-band gain G w and the cross-spectral gain G cs compared in the double-well system for a periodic pulse train as input.The standard deviation of the additive input noise is denoted byσThe results for the aperiodic signals we were mainly interested in are depicted in Fig 4.In the left panel,we can see that a pulse train made aperiodic by having its peaks at randomised locations can be improved by stochastic resonance almost to the same extent as its periodic counterpart.Encouraged by thisfinding,we went even further an applied a band-limited noise with low cut-offfrequency as input signal(to avoid confusion,we use the terms noise as signal and additive noise to differentiate between the random process acting as input signal and the one acting as the stochastic excitation which defines stochastic resonance).From the right panel of Fig4,we can deduce that input-output improvement is possible even for completely random input signals.One may argue that the input-output improvement of a noise acting as input signal stems simply from afiltering effect caused by the fact that the response time of the double well is limited,preventing high-frequency oscillations from appearing at the output.If this is the case,the major part of the additive noise getsfiltered out while the noise as signal, having a much lower cut-offfrequency,remains largely intact,which then leads to an input-output gain.We followed two different paths to examine this possibility:first,we compared the results obtained in the double well to those obtained in a non-dynamical stochastic resonator,the Schmitt trigger,wherein no suchfiltering can take place;second,we reduced the bandwidth of the additive noise to get it closer to the bandwidth of the noise as signal. The data pertaining to the Schmitt trigger come from numerical simulations carried out with the same parameters as the mixed-signal measurements.802468100.00.10.20.30.40.50.60.7G c s σ/A T 0.00.51.01.52.02.50.00.20.40.60.8 1.0 1.2G c sσ/A TFigure 4:The cross-spectral gain G cs in the double-well system for an aperiodic pulse train (left panel)and a band-limited noise (right panel)as input signal.The three curves on the right panel correspond to three different bandwidths of the additive noise.The standard deviation σof the additive input noise is normalised by the value of the threshold amplitude A T246810120.00.10.20.30.40.50.60.70.8G c sσ/A T Double well Schmitt trigger 0.00.51.01.52.02.50.00.20.40.60.8 1.0 1.2 1.4G c sσ/A T Figure 5:The cross-spectral gain G cs in the double-well system and in the Schmitt trigger compared for an aperiodic pulse train (left panel)and a band-limited noise (right panel)as input signal.The standard deviation σof the additive input noise is normalised by the value of the threshold amplitude A TIn Fig 5we can observe the similarity between the results in the double well and those in the Schmitt trigger,which suggests that the limited response time due to the dynamics of the double-well system may not play a significant role in producing an input-output gain.Indeed,at low frequencies such as those we have chosen the output of the double well is very similar to that of the Schmitt trigger.90.00.51.01.52.00.00.5 1.0 1.5 2.0G c s σ/A T5 kHz 1.25 kHz 312 Hz 156 Hz 0.81.01.21.41.61.82.02.22.40.01000.02000.03000.04000.05000.0G c s , m a x Noise bandwidth [Hz]Figure 6:The dependence of the cross-spectral gain G cs obtainable in the Schmitt trigger for a band-limited noise acting as input signal on the bandwidth of the additive noise .The right panel depicts the maximum of the gain curves as a function of the bandwidth of the additive noiseFrom the right panel of Fig 4we can infer that reducing the bandwidth of the additive noise,while degrading the value of the gain,does not prevent input-output amplification paring the right panel of Fig 4with the left panel of Fig 6,we may also see that the reduction in the bandwith of the additive noise affects the two systems,the dynamical and the non-dynamical,in a very similar way,showing that the decrease in the value of the gain is not a result of a filtering effect.We also examined how the maximum of the gain depends on the bandwidth of the additive noise:the right panel of Fig 6shows that input-output improvement occurs in a very wide additive noise bandwidth range and the value of a gain only sinks below one for bandwidths that are less than ten times the signal bandwidth (it is important to note here that a noise bandwidth much greater than the frequency of the signal is a requirement for stochastic resonance itself to take place).IV.CONCLUSIONSUtilising a mixed-signal simulation system,we have demonstrated that the stochastic resonance occurring in the archetypal double-well model can lead to a significant input-output improvement even for aperiodic signals.We applied two kinds of aperiodic signals,a randomised pulse train and a band-limited noise as input signal,and using a cross-spectral measure to reflect their noise content both at the input and at the output,we have found input-output gains well above unity for both types of signals.10From a comparison between the dynamical double-well and the non-dynamical Schmitt trigger,and from studying the dependence of the gain on the bandwidth of the additive noise,we can conclude that the significant signal improvement we have found is not a result of afiltering effect due to the limited response time inherent in the dynamics of the double well.Our results bring about a significant extension of the range of signal types which can be improved by stochastic resonance.Now it is clear that—although the value of the gain may depend on the type of the input signal—there are no strict requirements for the input signal to be amplified by SR:it need not be pulse-like or periodic at all;in fact,even completely random signals may be improved.AcknowledgementsOur research has been funded by OTKA(Hungary),under grant T037664.Z Gingl acknowledges support from the Bolyai Fellowship of the Hungarian Academy of Sciences.[1]R.Benzi,A.Sutera,and A.Vulpiani,Journal of Physics A14,L453(1981).[2]L.B.Kiss,in Chaotic,Fractal and Nonlinear Signal Processing,edited by R.Katz(1996),vol.375,pp.382–396.[3]K.Loerincz,Z.Gingl,and L.B.Kiss,Physics Letters A224,63(1996).[4] F.Chapeau-Blondeau,Physics Letters A232,41(1997).[5]Z.Gingl,R.Vajtai,and L.B.Kiss,Chaos,Solitons and Fractals11,1929(2000).[6] F.Liu,Y.Yu,and W.Wang,Physical Review E63,051912(2001).[7]Z.Gingl,P.Makra,and R.Vajtai,Fluctuation and Noise Letters1,L181(2001).[8] D.F.Russell,L.A.Wilkens,and F.Moss,Nature402,291(1999).[9]I.Hidaka,D.Nozaki,and Y.Yamamoto,Physical Review Letters85,3740(2000).[10]S.Fauve and F.Heslot,Physics Letters A97,5(1983).[11] 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