جستجوی مقالات مرتبط با کلیدواژه « sensitivity » در نشریات گروه « فنی و مهندسی »

Accurate solving of complex systems such as space systems and specifically space propulsion system is very costly and time consuming. By developing and building a surrogate model, the solution time and the cost can be reduced. The closer the surrogate model is to the actual model, the more accurate the solution and the lower the error rate. High-precision successor models are called metamodels. The basis of producing a high-precision meta-model is to perform high-precision sensitivity analysis with a suitable method. Sensitivity analysis can show the effect of input variables on output variables and produce a surrogate model by eliminating ineffective input variables. Therefore, sensitivity analysis is of great value in solving complex systems. The purpose of this paper is to analyze the sensitivity of the multidisciplinary design of a monopropellant liquid propulsion system by the Latin Hypercube Sampling method. In this article, the topics related to the liquid monopropellant propulsion system are divided into six parts: High pressure gas tank, liquid fuel tank, injector, decomposition chamber, catalytic bed and nozzle. By determining the input and output variables of each subject, the results of sensitivity analysis are displayed in two ways: the sensitivity of the input variables to the output and the two-by-two correlation of the parameters with each other. In the results, as can be seen, the specific impulse input variable, in the high-pressure gas tank and the liquid fuel tank, has no effect on the output variables. In the injector, the number of grooves, groove angles and fuel tank pressure do not have a significant effect on the output variables. In the decomposition chamber sensitivity analysis diagram, the radius of the granule and for the catalyst bed, in addition to the radius of the granule, the percentage of ammonia decomposition are also ineffective. Finally, the sensitivity analysis for the nozzle shows that the ratio of specific heat has no effect on the output variables.

Estuaries and bays are areas with a wide range of hydrodynamic and morphological phenomena. The existence of this diversity in environmental processes will lead to complex and sometimes unknown interactions in their structure. Understanding the behavior and environmental conditions of these beaches will improve the attitude of coastal users for better management of these areas. Many classifications have been made by researchers to understand the behavior of this coastal environment. The dimensionless VU parameter is a numerical parameter to facilitate speed, accuracy as well as cost reduction in the classification of this coastal environment. This parameter classifies the estuaries into three categories: tidal domination, wave domination, and mixed energy, based on the relative strength of the tides and the river flow relative to the wave infiltration. Each of these classes has its own behavioral characteristics. The purpose of this study is to identify the type of performance of the North Persian Gulf estuaries and sensitivity measurement The dimensionless VU parameter in the classification of morphodynamic class of Persian Gulf estuaries. Morphological classification was used as the basic criterion for validation and Hayes hydrodynamic classification was used as a comparison tool. For this purpose, data from observing the trend of changes from satellite images, wave data and tides and meteorology have been used. To classify the dimensionless parameters of the estuaries, the tidal amplitude, the area of the estuaries and the tidal prism in the estuaries have been calculated. The results of morphological classification indicate that the study area is dominated by tides and the results of Hayes hydrodynamic classification with 96% accuracy have presented similar results to morphological classification. In contrast, the dimensionless parameter VU with poor accuracy of 53% presented poor results in classification. By examining the calculation results, the error rate of the dimensionless parameter VU in small estuaries and tidal domains has been determined. By defining the ratio of wave height to tidal amplitude (H / TR), regression lines of difference intervals, the dimensionless parameter VU with morphological classification is determined. It was also found that in a constant ratio of wave height to tidal amplitude, with increasing wave height, the percentage of classification the dimensionless parameter VU error increases. And also at a constant wave height, with decreasing tidal amplitude, the percentage of the dimensionless parameter VU increases.

In this paper, capacitive tilt micro sensors based on the MEMS technology are designed, analyzed and simulated. These micro sensors are cylindrical and interdigital capacitors (IDC) of the structure from copper, are located on one of their bases. Electrodes of the IDCs are located on the same plate and connected to the ground or terminal voltage. Half of the cylinder is filled with the silicone oil while there is air in the other half. By rotating the cylinder around the x-axis, as the oil level inside the cylinder remains horizontal due to the gravity, position of the electrode’s surfaces which are located inside the oil changes, so tilt around this axis is measured. Two structures are proposed to measure tilt around the x-axis. In this paper, using detailed analysis, the effect of the angular changes on the structural capacitors and outputs is investigated. Moreover, the proposed structures have been simulated by COMSOL Multiphysics software. The results of simulation and analysis are in good agreement. The measuring range of these structures is -90 ° to 90 ° or 0 ° to 180 °  with the sensitivity of 44 fF/deg and 88 fF/deg for one and two-capacitor structure, respectively.

In this study, a plasmonic infrared refractive index sensor (RI) based on the Metal-Insulator-Metal (MIM) structure by two gold nanorods in the top layer to measure the analytic refractive index has been proposed. Sensor characteristics such as Sensitivity (S), Full Width at Half Maximum (FWHM) and Figure of Merit (FOM) were calcuted 736.842 nm / RIU, 40 nm and 18.421, respectively.Since the two-dimensional nature of collective provocations in graphene makes plasmon imprisonment in graphen is more powerful than metals and in addition, the  metals does not ideally absorb biological molecules, A graphene layer has been added to increase the sensitivity of the sensor. Finally, the gold nanorod sensor using graphene layer between the nanorods and dielectric was investigated and the characteristics of the sensor with thickness of graphene layer, 2 nm and chemical potential of 0.7 eV have obtained as S = 778.571 nm / RIU, FWHM = 46 and FOM = 16.045.

Diaphragm pressure sensors are used in various industries. Much research has been done to optimize and improve the quality of these sensors. This paper investigates "sensitivity" as a critical variable in diaphragm pressure sensors based on MEMS technology. Aperture geometry is one of the most influential variables in the sensitivity of a diaphragm sphygmomanometer, which in addition to sensitivity, can affect other variables such as operating range, sensor accuracy, dimensions, and even price. To increase the performance and sensitivity of pressure sensors, the sensor aperture was simulated in AbaqusFEA software, and while validating the computational solver, different geometries were evaluated. The results showed that the circular diaphragm has the best performance. Then the effect of corrugations on the surface of the diaphragm was investigated, and different forms of waves were simulated. The results showed that creating a circular wave with a radius of 15 μm at the end of the diaphragm surface increases the sensor's sensitivity by 18%.

The aerodynamic coefficients of any flying object can be estimated with high accuracy, by aero-ballistic tests, monitored in aerodynamic laboratories. For test-running management, it is necessary to determine the number and type of estimated variables and the station placement of each test. For this purpose, the sensitivity of variables under measurement, in relation to the associated aerodynamic coefficients must be calculated and surveyed. As the trajectory path is a nonlinear equation with six degrees of freedom, in this article we estimate the aerodynamic coefficients and sensitivity of each output to the changes of aerodynamic coefficients using the least square method and fisher data matrix. In other word, if the test data such as the speed and pitch angle are to be measured in an aero-ballistic test, the results of this research can specify their accuracy and sensitivity to each aerodynamic coefficient and the relevant coefficient errors.

Auxetic structures (negative Poisson’s ratio) are a group of materials that expand (contract) under tensile (compression) longitudinal loading. In this work, the effect of re-entrant auxetic structure geometry on Poisson’s ratio was investigated under large tensile loading experimentally and numerically and showed that the location and stiffness of rotation joints are two new important parameters affecting the value of Poisson’s ratio. Poisson's ratio increases as the rotation joints tighten and move away from the center of the structure. Therefore, by changing the location and stiffness of the rotation joints, it will be easy to obtain re-entrant auxetic structures with different Poisson's ratios, which makes it possible to build piezoresistant auxetic sensors with different sensitivities. A highly sensitive, stretchable piezoresistant auxetic sensor made of silicon rubber and chopped carbon fibers is proposed for low strain values. The main feature of this sensor is its high sensitivity for strains less than 6%, which previous works have been unable to detect this range of strains. Shifting strain is the value of strain in which the Poisson's ratio of the structure changes from negative to positive. The provided auxetic sensor performs exceptionally well until the shifting strain and then performs as conventional sensors. This improvement in sensing performance is about 150% (in terms of gauge factor).