Simulation Of Transient Response Research Articles

Numerical Simulation of Transient Response of Inlet Relative Humidity for High Temperature PEM Fuel Cells with Material Properties

High temperature proton exchange membrane fuel cells (HT-PEMFCs) have been drawing much attention due to their easy water management and other advantages. A three-dimensional non-isothermal transient model of HT-PEMFCs with phosphoric acid doped polybenzimidazole (PBI) membrane is developed in this study. The inlet relative humidity (RH) is considered for the membrane conductivity in the model. The effect of inlet RH on the transient response of the cell is discussed and the results show that the increase of inlet RH had positive effect on cell performance but negative effect on transient response.

Validation of the heat and mass transfer models within a pressurized water reactor containment using the International Standard Problem No. 47 data

Abstract A lumped parameter type code, called HEPCAL, has been worked out in the Institute of Thermal Technology of the Silesian University of Technology for simulations of a pressurized water reactor containment transient response to a loss-of-coolant accident. The HEPCAL code has been already verified and validated against available experimental data, which in fact have been taken from separate effect tests mainly. This work is devoted to validation of the latest version of the HEPCAL code against experimental data from more complex tests. These experiments have been performed on three different test rigs (called TOSQAN,MISTRA and ThAI) and a part of them became the basis of the International Standard Problem No. 47 (ISP-47) dedicated to containment thermal-hydraulics. Selected experiments realized within the framework of the ISP-47 project have been simulated using the HEPCAL-AD code. The obtained results allowed for drawing of some important conclusions concerning heat and mass transfer models (especially steam condensation), two-phase flow model and buoyancy effects.

Simulation of Lamb wave reflections at plate edges using the semi-analytical finite element method

In typical Lamb wave simulation practices, effects of plate edge reflections are often not considered in order to simplify the wave signal interpretations. Methods that are based on infinite plates such as the semi-analytical finite element method is effective in simulating Lamb waves as it excludes the effect of plate edges. However, the inclusion of plate edges in a finite plate could render this method inapplicable, especially for transient response simulations. Here, by applying the ratio of Lamb mode reflections at plate edges, and representing the reflection at plate edges using infinite plate solutions, the semi-analytical finite element method can be applied for transient response simulation, even when the plate is no longer infinite.

Comparison of simulations to experiment for a detailed analysis of space-charge-limited transient current measurements in organic semiconductors

Space-charge-limited current transients (also referred as time resolved dark injection) is an attractive technique for mobility measurements in low mobility materials, particularly the organic semiconductors. Transients are generally analyzed in terms of the Many-Rakavy theory, which is an approximate analytical solution of the time-dependent drift-diffusion problem after application of a voltage step. In this contribution, we perform full time-dependent drift-diffusion simulation and compare simulated and experimental transients measured on a sample of triaryl-amine based electroactive dendrimer (experimental conditions: $\ensuremath{\mu}\ensuremath{\approx}{10}^{\ensuremath{-}5}$ cm${}^{2}/\text{(Vs)}$, $L=300$ nm, $E<{10}^{5}$ V/cm). We have found that the Many-Rakavy theory is indeed valid for estimating the mobility value, but it fails to predict quantitatively the time-dependent current response. In order to obtain a good agreement in between simulation and experiment, trapping and quasi-ohmic contact models were needed to be taken into account. In the case of the studied electroactive dendrimer, the experimental results were apparently consistent with the constant mobility Many-Rakavy theory, but with this model, a large uncertainty of $20%$ was found for the mobility value. We show that this uncertainty can be significantly reduced to $10%$ if a field-dependent mobility is taken into account in the framework of the extended Gaussian disorder model. Finally, we demonstrate that this fitting procedure between simulated and experimental transient responses also permits to unambiguously provide the values of the contact barrier, the trap concentration, the trap depth in addition to that of the mobility of carriers.

On the stochastic simulation of hydroelectric turbine blades transient response

This paper describes a methodology for the extrapolation of a single measured non-stationary time series to an expected long-term service history. Within the context of limited data availability, stochastic simulation is used to generate an ensemble of surrogate realizations from which expected long-term service histories can be derived. Two non-stationary stochastic simulation algorithms are implemented. Both simulation algorithms are compared using the transient response measured on hydroelectric turbine blades during startup. In both algorithms, an independent random phase shift is introduced in the analytic signal given by the Hilbert transform of each time series subcomponent. The subcomponents are obtained either by Empirical Mode Decomposition (EMD) or by Stationary Wavelet Decomposition (SWD). The simulated realizations will invariably include some inherent variations arising from the process itself, combined with epistemic uncertainty due to the assumptions made during modeling. To ensure the quality of the simulated realizations, the following quantitative criteria are used to compare the simulated ensemble to the reference data: cumulative energy, extreme value distribution and rainflow amplitude spectra.

A Precision and High-Speed Behavioral Simulation Method for Transient Response and Frequency Characteristics of Switching Converters

We propose a fast and precise transient response and frequency characteristics simulation method for switching converters. This method uses a behavioral simulation tool without using a SPICE-like analog simulator. The nonlinear operation of the circuit is considered, and the nonlinear function is realized by defining the nonlinear formula based on the circuit operation and by applying feedback. To assess the accuracy and simulation time of the proposed simulation method, we designed current-mode buck and boost converters and fabricated them using a 0.18-µm high-voltage CMOS process. The comparison in the transient response and frequency characteristics among SPICE, the proposed program on a behavioral simulation tool which we named NSTVR (New Simulation Tool for Voltage Regulators) and experiments of fabricated IC chips showed good agreement, while NSTVR was more than 22 times faster in transient response and 85 times faster in frequency characteristics than SPICE in CPU time in a boost converter simulation.

Voltammetric Behavior of Gold Nanotrench Electrodes

We report the fabrication and electrochemical response of a gold nanoband electrode located at the bottom of a glass/epoxy nanotrench, hereafter referred to as a gold nanotrench electrode. Gold nanotrench electrodes of 12.5 and 40 nm in width with various depths from a few tens of nanometers to approximately 4 μm are fabricated and further characterized by cyclic voltammetry. The fabrication of a Au nanotrench electrode follows a simple electrochemical etching process in which a small AC signal is applied to an inlaid Au nanoband electrode submersed in a NaCl solution. The voltammetric behavior of a Au nanotrench electrode is characterized by a quasi-steady-state response at lower scan rates (e.g., <1 V/s for a 12.5-nm-wide electrode). We present an analytical expression for the quasi-steady-state diffusion-limited current of the nanotrench electrode based upon the analysis of the mass-transport resistance. Finite-element simulation of steady-state and transient voltammetric responses of the nanotrench electrodes provides additional insights for the analytical model. Peak-shaped transient voltammetric responses were observed at scan rates as low as 5 V/s for both inlaid and nanotrench electrodes. This result may suggest that the exposed area of the nanoband electrode is much greater than that expected from the fabrication of the inlaid bands. However, the extent to which this is seen is greatly decreased in the nanotrench electrode by a smoothing effect during etching. Our results confirm previous reports of excess overhanging metal and delamination crack contributing significantly to the shape and magnitude of the voltammetric response.

9F-05 蝸牛内基底板の過渡応答シミュレーション(OS-8 福祉・リハビリテーション工学(3))

9F-05 蝸牛内基底板の過渡応答シミュレーション(OS-8 福祉・リハビリテーション工学(3))

The magnetic relaxation effect on TEM responses of a two-layer earth

We have simulated ungrounded horizontal loop transient responses of a two-layer earth consisting of a magnetically viscous layer above (model 1) or below (model 2) a nonmagnetic layer. The transient responses of a two-layer magnetically viscous earth can be computed using the superposition principle because magnetic relaxation and eddy current responses are independent at electrical conductivities typical of the real subsurface. The transients are presented and analyzed in the form of Y = f( h1) functions, where h1 is the upper layer thickness and Y is the response (at some fixed time) of a two-layer ground normalized to that of a uniform ground with its magnetic viscosity as in the upper (model 1) or lower (model 2) layer. In model 1, the Y function increases as magnetic viscosity grows in the upper layer while the latter is thinner than the loop size, but the magnetic relaxation responses of a thicker upper layer are almost identical to that of a uniform magnetically viscous ground. In model 2, the Y responses are likewise almost identical to that of a uniform magnetically viscous ground ( h1 = 0) as far as the thickness of the upper layer remains small, but they decrease, first slowly and then ever more rapidly, after the layer becomes 15–20% thicker than the transmitter size. The effective sounditng depth in a magnetically viscous ground being controlled by the size of the transmitter, it is reasonable to use geometrical sounding to resolve the vertical distribution of magnetic viscosity.

Verification of Thermal System Performance for Control Applications Using TMG Finite Element Simulation and MATLAB

Many real world engineering systems are sensitive to temperature, and temperature control is vital to the success and operation of a broad spectrum of engineering applications. This paper investigates the use of numerically generated frequency response data to simulate the control system behavior of a simple but realistic finite element based nonlinear thermal model. Using an IDEAS TMG finite element model, a thermal control system Bode plot was computed. The Bode plot was then used to determine the transfer function of the thermal system and design an appropriate control compensator to implement thermal control. The performance of the compensated thermal system was then predicted first by MATLAB, and second by TMG. The response predicted by MATLAB using transfer functions was corroborated by its close agreement with a TMG finite element transient response simulation.

A 'concatenation' study of wave energy transport among three coupled plates

We address the problem of constructing predictions for the diffuse transport and distribution of mean spectral acoustic energy density in an undamped complex linear structure, without appeal to SEA and by taking information gleaned from short time cost‐effective, direct numerical simulations (DNS). A numerical model is constructed consisting of three finite plates coupled by sets of springs. Coupling is chosen to be sufficiently strong to avoid localization and sufficiently weak that the notion of substructures remains valid. Numerical simulations of transient responses to each of several sources are carried out; responses are recorded at each of several receivers. The resulting time‐domain diffuse waveforms are analyzed for the work done at each source, and the transient spectral energy density at each receiver at times shortly after the action of the sources. This information is used in a 'concatenation' ansatz to predict the evolution and distribution of spectral energy density at these receivers at later times. The resulting prediction is compared favorably with the actual energy densities observed in the DNS at late times. It is described how the results also apply directly to the more conventional but closely related problem of damped systems and/or steady state input. Work supported by NSF CMS‐0528096.

Modeling and simulation of transient responses of a flexible beam floating in finite depth water under moving loads

The dynamic response of a free–free flexible beam floating in an unbounded water domain under the effect of moving loads is numerically analyzed. The water is assumed compressible and inviscid. The surface disturbance satisfies a linear free surface wave condition and an undisturbed condition at infinity. In the present work, a finite element procedure was developed directly in time domain and implemented to solve the two-dimensional problem of the transient behavior of an elastic beam floating on the surface of finite deep water under the passage of a moving force with uniform speed. The presented data demonstrates the applicability of the proposed mathematical model and numerical approach. The influences on the dynamic responses of floating beam of some factors were studied.

Accurate numerical models for simulation of radiation events in nano-scale semiconductor devices

Space and ground-level electronic equipment with devices of nanometer scale and extremely high densities may be strongly affected by ionizing radiation. Accurate numerical models are necessary for better analysis of radiation effects and design of radiation tolerant devices. Numerical models and adaptive dynamic 3D mesh generation presented in this paper enable efficient simulations of transient semiconductor device response to realistic multi-branched track, produced by ionizing particle and nuclear reactions. A description of the numerical models, adaptive 3D meshing approach, and efficient solution method for large 3D problems using unstructured meshes is provided. The developed approach efficiently uses computer resources, which makes possible solution of transient 3D multi-branched ion strike problems with 100,000 mesh nodes within 512MB computer memory.

Magnetohydrodynamic simulations of transient transpolar potential responses to solar wind density changes

Magnetohydrodynamic (MHD) simulations are used to examine the response of the transpolar potential (ΦTP) to changes in the solar wind density during periods of constant solar wind electric field. For increases (decreases) in the solar wind density ΦTP responds immediately by increasing (decreasing) from the steady state values. In both cases the response of ΦTP is transient, decaying to near initial steady state values even when the density change persists. The magnitude of the ΦTP response is proportional to both the rate of erosion of the dayside magnetopause and the ionospheric Pedersen conductance. In our MHD simulations ΦTP is driven entirely by the dayside merging rate and is insensitive to changes in the nightside reconnection rate. The observed relationship between the modeled dayside merging rate and ΦTP is well characterized by an L‐R circuit equation derived from integrating Faraday's Law around the Region 1 current loop. The inductive time constant for variations in the transpolar potential was found to be 6.5 (13) minutes for simulations using ionospheric Pedersen conductances of 6 (12) mhos. This corresponds in both cases to a magnetosphere‐ionosphere inductance of 65 Henries. Observations of the transpolar potential derived using the assimilative mapping of ionospheric electrodynamics (AMIE) model are presented and shown to be consistent with the simulation results.

Numerical simulation of transient hydroelastic response of a floating beam induced by landing loads

The dynamic response of a floating platform under the effects of impulsive and moving loads is of concern in various areas of engineering technology, such as floating airports, floating bridges and buoyant tunnels, among others. In the present work, the floating platform is simplified as a flexible beam floating in an infinite water domain. The water is assumed to be compressible and inviscid, whose governing equation is formulated in terms of the hydrodynamic pressure variable. The surface disturbance satisfies a linear free-surface wave condition and a radiation wave condition at an artificially truncated boundary. A time-domain finite element model is developed to analyze this fluid–structure interactive dynamical system, which exhibits strong coupling between the system’s components. The numerical results are compared with the experimental and numerical ones. The results of comparison confirmed the validity of the proposed approach. The influences on the dynamic responses of floating beam of some factors were studied.

Transient Response Simulation of an Off-Road Motorcycle with Conventional and Multicell Tire Inflation Mechanisms

Abstract Resistance to complete loss of inflation pressure due to puncture is the primary purpose for using nonconventional multicell tire inflation mechanisms. However, recent subjective testing of one particular multicell mechanism also reveals beneficial ride performance characteristics. To gain scientific understanding of this additional benefit, an off-road motorcycle model is developed. Pneumatic stiffness behavior of a conventional inner-tube and the multicell inflation mechanism is described by a simplified tire model which has been shown to accurately predict experimentally measured static stiffness data. Numerically simulated transient response data from the vehicle model is used to evaluate ride performance characteristics when the two mechanisms are used for tire inflation. Data analysis is also performed to reveal why performance improves when the multicell mechanism is utilized. The procedure is validated using experimental data collected on a real vehicle under conditions similar to the numerical simulation.

Simulating Nuclear Events in a TCAD Model of a High-Density SEU Hardened SRAM Technology

The interaction between a heavy ion and the overlayer materials in an integrated circuit may result in a nuclear reaction. This reaction leads to a charge generation profile that is substantially altered from the profile generated during a direct ionization event. In this work, nuclear reactions are integrated into the modeling of the SEU response of an SRAM cell using GEANT4-based simulations. The simulated transient response is compared to the response obtained using a typical heavy ion model that includes only direct ionization

An improved mixed numerical-experimental method for stress field calculation

In this work a numerical-experimental method is used to study the dynamic behavior of an aluminum plate subjected to a small mass impact. The out-of-plane displacements, due to transient bending wave propagation, were assessed for successive time instants, using double pulse TV-holography, also known as pulsed ESPI. The experimental setup and the image processing methods were improved to allow the calculation of the plate transient stress field. Integral transforms are used to obtain the strain fields from spatial derivatives of displacements noisy data. A numerical simulation of the plate transient response was carried out with FEM Ansys ®. For this purpose a PZT transducer was used to record the impact force history, which was inputted in the numerical model. Finally, the comparisons between numerical and experimental results are presented in order to validate the present methodology.

Simulation of the temperature transient response of the bimetallic thermometer

The temperature of the oil in automobile oil pan is often measured by a bimetallic thermometer. The bimetallic thermometer was selected as a prime case of a thermometer that is affected by the thermal energy. It serves as a pilot example for the larger project focused on the study of thermal load of thermometers. The paper deals with the mathematical simulation of temperature fields in the bimetallic thermometer. The temperature field is generated by the influence of the ambient temperature and the influence of concrete oil. ANSYS environment is used for the modelling of this physical problem.

The vibratory characteristics of obturators with different bulb height and form designs

The aim of the present study was to investigate whether the vibratory characteristics of obturator prostheses are affected by bulb design, i.e.: the hollow or buccal flange type, and different lateral and medial bulb heights. Buccal flange and hollow bulb obturator prostheses were fabricated with two different lateral bulb wall heights and two different medial bulb wall heights. Ultimately, eight obturator prostheses were prepared for evaluation of their vibratory characteristics. The frequency-response functions were recorded on an FFT analyzer to identify their vibratory characteristics. A transient response simulation was carried out in which an impact was applied to the non-defect side. The decay rate, damping time and maximum amplitude of the retainers were statistically analysed by anova with Scheffé's test (P < 0.05). The decay rate of every buccal flange type was higher and damping time was shorter than those of every hollow type, except between a pair with low lateral and low medial bulb walls. The maximum amplitude values of four obturators with low medial bulb walls were significantly lower than those of four obturators with high medial walls. The buccal flange obturator prosthesis with high lateral and low medial walls showed the maximum decay rate and the minimum amplitude of the retainers on molars. Vibration analysis suggests that a buccal flange obturator prosthesis with high lateral and low medial walls is preferable.