Theoretical Sensitivity Analysis Research Articles

高灵敏度FBG水听器

A fiber Bragg grating (FBG) hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressure sensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young's modulus of the diaphragm is higher, a flatter frequency response will be obtained.

Research of a novel fiber Bragg grating underwater acoustic sensor

A new type of optical fiber underwater acoustic sensor (hydrophone) constructed with two fiber Bragg gratings (FBG) and a self-demodulation method is presented in this paper. Unlike other FBG sensors which have separate sensing and demodulating elements, this FBG hydrophone has only a single structure for both sensing and demodulating using a pair of matched FBGs. The cylindrical structure of the hydrophone solves the problems of low sensitivity and cross-sensitivity of the bare fiber Bragg grating acoustic sensors. Theoretical analysis of measurement sensitivity is described. Simulation and preliminary experimental results indicate that the measurement sensitivity can reach 0.78 nm/MPa for underwater acoustic pressure in range of 100–200 dB re 1 μPa.

Sensitivity Analyses and Validation of Continuous Roll Prediction Model for Front Drive Mowers

This study relates to a continuous roll prediction model for front-mounted mowers; this software is used for analysis of roll behavior of front-mounted mowers. Sensitivity analysis of this model evaluated deck width, Roll Over Protective Structure (ROPS) position, deformation of ROPS and soil, and operator mass. Field tests were conducted to evaluate the accuracy of the theoretical sensitivity analysis. The objectives were to study how these parameters affect the roll behavior and the influence degree (Change of Critical ROPS Height (CRH) divided by original CRH). The model showed strong sensitivity to the deck height (D3), the horizontal distance (L3) between deck/slope contact point and the center of gravity, the horizontal distance (L6) between center of gravity (CG) and the ROPS impact point, therefore, the slight changes in these parameters caused a greater change in the roll behavior. The model was relatively insensitive to the extension width of the mower deck measured from the center of the front tire (Bm), the deformation (T) of ROPS and soil, and the operator mass (m1 ). From the sensitivity analysis, there is greater tendency for the mower to continuously roll with lower deck position than higher deck position and regular ROPS position; therefore, these factors should be used in the mower design. The information gained from this sensitivity analysis can be useful for ROPS and mower design to meet the continuous roll requirement of ASAE S547.

An EOQ model for deteriorating items with price dependent demand and permissible delay in payments under inflation

An inventory model in which the supplier provides the purchaser a permissible delay of payments is developed when units in inventory are subject to constant rate of deterioration and demand is selling price dependent. Shortages are not allowed and effect of the inflation rate is considered. The optimal solution is characterized to optimize the net profit. An easy-to-use algorithm is given to find the optimal selling price, the optimal order quantity and replenishment cycle time to maximize the net profit. At the end, a numerical example is given to illustrate the theoretical results and sensitivity analysis of parameters on the optimal solutions is carried out.

Modular metabolic control analysis of large responses

Deciphering the laws that govern metabolic responses of complex systems is essential to understand physiological functioning, pathological conditions and the outcome of experimental manipulations of intact cells. To this aim, a theoretical and experimental sensitivity analysis, called modular metabolic control analysis (MMCA), was proposed. This field was previously developed under the assumptions of infinitesimal changes and/or proportionality between parameters and rates, which are usually not fulfilled in vivo. Here we develop a general MMCA for two modules, not relying on those assumptions. Control coefficients and elasticity coefficients for large changes are defined. These are subject to constraints: summation and response theorems, and relationships that allow calculating control from elasticity coefficients. We show how to determine the coefficients from top-down experiments, measuring the rates of the isolated modules as a function of the linking intermediate (there is no need to change parameters inside the modules). The novel formalism is applied to data of two experimental studies from the literature. In one of these, 40% increase in the activity of the supply module results in less than 4% increase in flux, while infinitesimal MMCA predicts more than 30% increase in flux. In addition, it is not possible to increase the flux by manipulating the activity of demand. The impossibility of increasing the flux by changing the activity of a single module is due to an abrupt decrease of the control of the modules when their corresponding activities are increased. In these cases, the infinitesimal approach can give highly erroneous predictions.

Gas-phase photoacoustic sensor at 8.41 μm using quartz tuning forks and amplitude-modulated quantum cascade lasers

We demonstrate the performance of a novel infrared photoacoustic laser absorbance sensor for gas-phase species using an amplitude-modulated quantum cascade (QC) laser and a quartz tuning fork microphone. The photoacoustic signal was generated by focusing 5.3 mW of a Fabry–Perot QC laser operating at 8.41 μm between the tines of a quartz tuning fork which served as a transducer for the transient acoustic pressure wave. The sensitivity of this sensor was calibrated using the infrared absorber Freon 134a by performing a simultaneous absorption measurement using a 31-cm absorption cell. The power and bandwidth normalized noise equivalent absorption sensitivity (NEAS) of this sensor was determined to be D=2.0×10-8 W cm-1/Hz1/2. A corresponding theoretical analysis of the instrument sensitivity is presented and is capable of quantitatively reproducing the experimental NEAS, indicating that the fundamental sensitivity of this technique is limited by the noise floor of the tuning fork itself.

Optical sizing of aggregated combustion particles: computational development of a two-angle laser scattering technique

To simplify the experimental efforts involved in the nonintrusive optical characterization of typical combustion-generated particulates, an inverse analysis of scattering measurements at only two angles is developed and evaluated based on the exact scattering computations on simulated fractallike aggregates. Two optimum angles are suggested by combination of theoretical (sensitivity analysis) and practical (spatial resolution) considerations that have led to the interpretation of spherule diameter from the ratio of large-angle scattering and absorption coefficients and the aggregate gyration radius from the ratio of scattering dissymmetry. The inferred spherule and aggregate sizes are found to be generally in good agreement with the initially prescribed values for the range of physical and optical particulate properties considered here. These computational results under precise simulation conditions demonstrate the accuracy of the proposed particulate-sizing technique by avoiding the common experimental uncertainties that prevent a definitive performance assessment of any experimental method.

Reply to the comment on "Uncertainties in the temperature dependence of the line-coupling parameters of the microwave oxygen band: impact study"

For original paper see Boukabara et al., ibid., vol. 43, no.5, p.1109 (2005) and for comment see Rosenkranz., p.2160 (2005).The impact study described by Boukabar is, in essence, a theoretical sensitivity analysis of the temperature dependence of the line coupling coefficients in the microwave oxygen absorption band as accounted for in the millimeter-wave propagation model (MPM). The study was driven by emerging highly demanding requirements in terms of accuracy of the brightness temperatures measurements and therefore equally demanding requirements for models that simulate them. The main conclusions of the study are twofold: 1) the need to extend experimental measurements to the lower range of the atmospheric temperatures and 2) that errors due to uncertainties in the temperature dependence, are not necessarily entirely removable by a bias correction. The spectral region, where most of the impact was found, is located at the edge of the absorption band, especially in dry conditions. Rosenkranz commented on the work by Boukabara et al. and they now reply to these comments.

Theoretical and experimental studies of the spatial sensitivity of an electrostatic pulverised fuel meter

In coal-fired power plants, the coal is pulverised and pneumatically conveyed to the burners. It is essential to measure and control pulverised fuel (PF) to improve combustion efficiency, reduce pollution and lower operating costs. Unlike single-phase flow, where flow density is generally considered to be uniform, air–solids two-phase flow in pneumatic conveying systems can undergo inhomogeneous concentration distributions across a given pipe cross-sectional area, especially around bends and bifurcators or trifurcators. The “roping” flow regime is an extreme example of inhomogeneous solids distribution, where highly concentrated solids form a column-like (rope-like) flow. For such complex flow regimes, solids concentration or solids mass flow meters will give different outputs when inhomogeneous flow occurs at locations where these meters are installed if they are sensitive to the flow patterns. This problem can be solved in two ways. The first and simplest approach is to restrict the meter's installation to locations where solids are relatively uniformly distributed over the cross-sectional area of the pipe. Alternatively, it can be solved by using a meter having uniform spatial sensitivity, so that the measurement would not be affected by the flow regimes. Because the installation locations of PF meters must suit other requirements, such as accessibility for the convenience of maintenance, it is ideal if the meters have uniform spatial sensitivities. Electrostatic mass-flow meters are typically used to give a measure of the fuel mass flow rate. One design employs ring-shaped electrodes which have non-uniform sensitivity, resulting in variations in meter output for the same flow stream passing through the sensing volume at the different radii relative to the meter's central line. This paper presents a theoretical analysis of the spatial sensitivity of the electrostatic meter with ring-shaped electrodes in the time and frequency domains. One goal of the study is to improve its performance and to achieve uniform sensitivity. The experimental data presented in this paper support the overall mathematic modeling, based on electrostatic field theory, using the finite-element method (FEM). Although the FEM analysis provides useful results, a more rigorous investigation is recommended for future work.

Absorbing Aerosol Index: Sensitivity analysis, application to GOME and comparison with TOMS

The Absorbing Aerosol Index (AAI) was investigated and used to analyze GOME data and compare it to TOMS data. The physical interpretation of the AAI was studied with an extensive theoretical sensitivity analysis. The dependence of the method on a number of atmospheric, surface, and aerosol properties was studied using a numerical radiative transfer model. It was found to be sensitive to absorbing aerosols with wavelength‐dependent refractive indices and to elevated absorbing aerosols, both with wavelength‐dependent and wavelength‐independent (gray) refractive indices. It was found to be insensitive to clouds, while small size scattering aerosols yield negative values. AAIs were calculated from GOME data for the period July 1995 to December 2000 and compared to TOMS AAI data. In a part of this period, July 1995 to October 1996, no TOMS observations were available, and the GOME data can be used to supplement the TOMS data set. The GOME AAI corresponds very well with known absorbing aerosol events. It suffers from lower spatial resolution and less frequent temporal coverage as compared to TOMS, but is useful as an independent data source of global aerosol measurements.

A theoretical analysis of sensitivity in semiconductor measurement by microwave photoconductance decay

The aim of this work is to determine the sensitivity in the semiconductor measurement by microwave photoconductance decay. The reflection coefficient and the sensitivity were determined by solving the Maxwell equations and the method of a transfer matrix, then the dependence of sensitivity on the dark conductivity of sample, the distance between sample and metal reflector, and the thickness of sample for the general and two special measurement configurations were discussed. It is found that for all conductivity samples, the case of putting a metal reflector behind the detected sample with an optimal distance helps the sensitivity higher.

On the sensitivity and signal to noise ratio of a step-index fiber optic surface plasmon resonance sensor with bimetallic layers

In this paper, a theoretical analysis of sensitivity and signal-to-noise ratio (SNR) of a step-index fiber optic surface plasmon resonance sensor with bimetallic layers (silver and gold) has been carried out. The numerical treatment is based on Kretschmann’s SPR theory and Drude model of metals. The light source considered is a p-polarized one. The potential of different bimetallic ratios (gold as outer one) for the sensing purposes has been analyzed. The effect of different design parameters related to optical fiber as well as sensing layer on sensitivity and signal-to-noise ratio of the sensor has been studied. A comparison between selected ray launching and all guided rays launching in terms of sensitivity and SNR has been performed for different bimetallic ratios. The effect of fiber length and FWHM of a Gaussian input on the sensor’s performance has also been studied. All these studies, leads to a significant analysis to achieve the best possible design of a fiber optic SPR sensor with maximum sensitivity and SNR simultaneously for both laboratory and remote sensing applications.

Sensitivity of the FAA Integrated Noise Model to input parameters

The standard method for computing noise contours around civil airports is SAE-AIR-1845 (FAA Integrated Noise Model, European ECAC-CEAC Doc. 29). It is subject to the inaccuracies implicit in the model as well as those caused by erroneous or imprecise input data. Regarding the latter, the existing errors and/or uncertainties, may be amplified in the output results, to a greater or lower extent, in some cases offering unreliable predictions. In order to study this phenomenon, the Institute of Sound and Vibration Research (ISVR – Southampton) carried out a theoretical sensitivity analysis based on the segmentation technique, regarding the input parameters of the SAE-AIR-1845, and obtaining the input variables of the model, the variation of which implied greater changes in the output variables. The results were validated by using the FAA Integrated Noise Model Version 6.0 software, based on the aforementioned document. It has been revealed that the model has a greater sensitivity to factors that modify the flight path, and a lower sensitivity to the other parameters. Thus, an error greater than 10% in the variable “gross weight” offers an additional error of between 3 and 7 dB. However, parameters such as the ID of the flaps hardly modify the results obtained for the least favourable case by 1 dB. As a result of this research, the sensitivity of the model was quantified for each of the input parameters (taken alone and also in interaction with other parameters), and criteria for the minimisation of global error, resulting from uncertainties in the input parameters, were stated.

Study of a simple transient non-intrusive sensor for internal temperature estimation during food product freezing

It is first recalled that the temperature profile in a freezing product is almost linear. To estimate the freezing level of a food product, a non-intrusive sensor is proposed which may estimate the surface temperature and the slope of the internal temperature profile. It consists in analysing transient response when the sensor is set in contact with the product to characterise. The sensor is made of a thermopile (Peltier element) fixed on an isothermal medium made of a high effusivity material (copper). A modelling of the transient response of the sensor using the quadrupoles method is presented. Then, the results of the characterisation of the sensor by experimental determination of the transfer functions between fluxes and temperatures are given. A theoretical sensitivity analysis enables to study of the potential limits of this sensor. Finally, the influence of internal temperature profile slope on the sensor response is evidenced by the results of an experimental study. The main interests of this sensor are its simplicity and low cost and a flux measurement independent of thermal contact resistance to estimate a temperature.

Vibration measurements using continuous scanning laser Doppler vibrometry:theoretical velocity sensitivity analysis with applications

It is readily accepted that a laser vibrometer measures target velocity in thedirection of the incident laser beam, but this measured velocity must beconsidered in terms of the various components of the target velocity. This paperbegins with a review of the theoretical description of the velocity sensed by asingle laser beam incident in an arbitrary direction on a rotating targetundergoing arbitrary vibration. The measured velocity is presented as the sum ofsix terms, each the product of a combination of geometric parameters, relating tothe laser beam orientation, and a combination of motion parameters—the‘vibration sets’. This totally general velocity sensitivity model can beapplied to any measurement configuration on any target. The model is alsosufficiently versatile to incorporate time-dependent beam orientation and thisis described in this paper, with reference to continuous scanning laserDoppler vibrometry. For continuous scanning applications, the velocitysensitivity model is shown formulated in two useful ways. The first is in termsof the laser beam orientation angles, developing the original model toinclude time dependency in the angles, whilst the second is an entirely newdevelopment in which the model is written in terms of the mirror scan angles,since it is these which the operator would seek to control in practice.In the original derivation, the illuminated section of the rotating targetwas assumed to be of rigid cross section but, since continuous scanningmeasurements are employed on targets with flexible cross sections, suchas beams, panels and thin or bladed discs, the theory is developed inthis paper for the first time to include provision for such flexibility.

117 理論感度解析を用いた超音速フラッタ限界動圧向上のための平板翼の構造最適化

This paper investigates the structural optimization of plate wing for supersonic flutter. The analytical sensitivity of the critical dynamic pressure on supersonic flutter is formulated by the theoretical sensitivity analysis. The sensitivity is implemented in the steepest descent method to investigated the performance of the optimization. A delta wing model is considered for a numerical example. The numerical results indicate that the computational cost is reduced and the critical dynamic pressure is improved with respect to the results with the evolutionary structural optimization.

Fuzzy Logic Based Gains Determination of Induction Motor Flux Observers

It is proposed in this paper a method to compute gains of induction motor flux observers, based on fuzzy logic associated to a theoretical sensitivity analysis. The theoretical analysis, taking the magnetic saturation into account, allows to study the observer sensitivity to all parameter uncertainties. The fuzzy logic associated to the theoretical analysis allows to determine observer gains which optimize together dynamics and sensitivity criteria. Although the theoretical sensitivity analysis may be developed for observers in any reference frame, the proposed method is applied in this paper respectively to a reduced and a full order flux observers based on the Park model in the stator reference frame only. The proposed method is validated by experiments on a 750W induction motor.

Is the effect of wine on health confounded by diet?

To the Editor: A light to moderate intake of wine may have both cardioprotective and cancer inhibitory effects. 1 We have found that those who had a daily intake of 3–5 glasses of wine had a 50% lower risk of dying from all causes compared to non-drinkers of wine, while beer, and spirits drinking had a much smaller beneficial effect, if any. 1 However, diet may confound the relation. A high intake of fruit, vegetables, and fish and a low intake of saturated fat may reduce the risk of coronary heart disease morbidity and mortality. 2 There may also be protective effects of fruit and vegetables intake on risk of cancer. 3 Preference of wine compared to preference of beer or spirits may be associated with a more frequent intake of fruit, fish, vegetables, salads and olive oil. 4 Others have suggested that wine is associated with a presumably healthy diet, but none have taken dietary factors sufficiently into account in prospective studies of the health effects of wine. We have quantitatively assessed in a theoretical sensitivity analysis 5 whether diet is a plausible confounder of the relation between wine intake and mortality by applying the method to previously reported data from the Copenhagen City Heart Study. 1 In the present analysis, the unadjusted odds ratio for the 50 deaths among the 257 exposed (ie, those who had a daily intake of wine) and the 780 deaths among the 2,553 unexposed (non-wine drinkers) was estimated as 0.6. 1 The odds ratios for the relation between wine intake and mortality, adjusted for a hypothetical confounder, have been calculated for various scenarios (Table). It appears that even a very strong confounder (odds ratio = 0.3 or 0.1) would have to exhibit a very uneven distribution among wine drinkers and non-wine drinkers to fully explain the findings noted above. Table 1: Odds Ratios for Death among Wine Drinkers (1–5 Glasses of Wine per Day) Compared with Non-Wine Drinkers, Adjusted for Different Distributions of Confounding Factors of Three Different Strengths, Copenhagen City Heart StudyAlthough both errors in dietary assessment and intraindividual variability of the diet can lead to underestimation of dietary differences and effects, it seems very unlikely that the previously reported lower mortality among wine drinkers compared to non-wine drinkers can be explained fully by dietary factors. The finding that wine drinkers more frequently than beer and spirits drinkers may have a “healthier” diet 4 should, however, be taken into account in interpretations of the prospective studies of effects of both type of alcohol and diet. Until now, there is no clear evidence that there is a large protective effect of the healthy diet on morbidity or mortality. Further, the studies suggesting any such effect have not controlled their results for intake of alcohol or type of alcohol. The simple analysis presented here only takes a single confounder into account. It is evident that a conglomerate of several confounders, as well as possible effect modifiers (such as several dietary factors combined with, for example, a high level of physical activity), may play a role. Morten Grønbæk Thorkild I.A. Sørensen

Computational Sensitivity Analysis for State Constrained Optimal Control Problems

A theoretical sensitivity analysis for parametric optimal control problems subject to pure state constraints has recently been elaborated in [7,8]. The articles consider both first and higher order state constraints and develop conditions for solution differentiability of optimal solutions with respect to parameters. In this paper, we treat the numerical aspects of computing sensitivity differentials via appropriate boundary value problems. In particular, numerical methods are proposed that allow to verify all assumptions underlying solution differentiability. Three numerical examples with state constraints of order one, two and four are discussed in detail.

A methodology to determine gains of induction motor flux observers based on a theoretical parameter sensitivity analysis

A method to compute gains of induction machine flux observers, based on a theoretical sensitivity analysis taking the magnetic saturation into account, with the aim to minimize the observer sensitivity to electrical parameter uncertainties is proposed in this paper. It is shown for a reduced order observer, that the sensitivity to parameter uncertainties may be independent of the reference frame, when a modification is introduced in the classical determination of the slip frequency. It is also shown how to extend the proposed method to a full order observer. The theoretical study is completed by experiments on a 750 W induction machine (using DSP TMS320C31) which confirms the theoretical results.