Transient Response Research Articles

Fast forward modeling of grounded electrical-source transient electromagnetic based on inverse Laplace transform adaptive hybrid algorithm

Frequency–time conversion is a crucial step in grounded electrical-source transient electromagnetic response calculation, and the performance of the algorithm is directly related to the overall accuracy and speed of forward modeling. In mainstream algorithms, algorithms with high accuracy often have slow computation speed while algorithms with high efficiency have unsatisfactory accuracy, especially when facing inversion problems that are difficult to meet requirements. This paper introduces three inverse Laplace transform algorithms for this problem: the Gaver–Stehfest algorithm, the Euler algorithm, and the Talbot algorithm. The performance of each algorithm in forward modeling was analyzed using half-space and layered models, and the optimal selection schemes for algorithm weight coefficients were provided. The numerical calculation results show that the Gaver–Stehfest algorithm has a unique advantage in computational efficiency, while the Talbot algorithm and Euler algorithm meet the accuracy requirements. After considering both accuracy and efficiency, the Talbot algorithm is selected to replace conventional algorithms for calculation of grounded electrical-source transient electromagnetic forward modeling. In addition, this paper combines the characteristics of the Gaver–Stehfest algorithm and the Talbot algorithm to implement an adaptive hybrid algorithm. This algorithm uses the Gaver–Stehfest algorithm for forward modeling in the early times and the Talbot algorithm to compensate for the decrease in accuracy in the later times. Through the comparison of forward modeling calculations, it can be seen that the hybrid algorithm proposed in this paper fully utilizes the advantages of both algorithms. The hybrid algorithm greatly improves computational speed while meeting accuracy requirements, and has significant advantages over conventional algorithms.

Non‐Contact Transfer Printing Enabled by an Ultrasonic Droplet Stamp

AbstractTransfer printing is an important material heterogeneous technique with unique capability for developing existing and envisioned electronic or optoelectronic systems. Here, a simple design of ultrasonic droplet stamp is reported featuring a water droplet on an acoustic resonator attached to a glass sheet, for developing an efficient non‐contact transfer printing. The water droplet offers the benefits of a gentle and conformal contact, yielding an enough adhesion for a reliable pickup in the absence of ultrasound, and ejects a sub‐droplet rapidly due to the Raleigh instability with the ultrasound for an easy non‐contact printing. Experimental studies are carried out to investigate the transient response of ultrasonic droplet stamp under the action of ultrasound and showed that the proposed stamp exhibited extraordinary capabilities of damage‐free pickup and receiver‐independent printing. Demonstrations of the ultrasonic droplet stamp in transfer printing of thin inks with different materials and shapes onto various flat, curved and rough surfaces illustrate its great potential for heterogeneous integration and deterministic assembly.

Design of 300nA quiescent current and 300mA load capacity LDO with fast transient response

Design of 300nA quiescent current and 300mA load capacity LDO with fast transient response

Analysis of Transient Instability on a 132KV Transmission grid Power System Using 4th Order Runge kutta Technique

This study examines the transient response of synchronous machines in a 132kV transmission grid power system utilizing 4th order Runge Kutta algorithms. In order to determine the critical clearance angle (CCA) and critical clearing time (CCT) of the transmission grid, a three-phase fault was intentionally introduced. Data were gathered from the Transmission Company Nigeria (TCN) for the specific purpose of analysis and simulation. The Electrical Transient and Analysis Program (ETAP 19.1) is utilized with circuit breaker and relay time settings of (0.00, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.2) to examine the differential variations in generator rotor angles, alterations in generator bus voltage, and changes in system frequency. The obtained results demonstrate that the 4th order Runge Kutta numerical technique is stable and accurate. It exhibits a fast response critical clearing time (CCT) of 0.02s and a critical clearing angle of 76.9 degrees, which is very close to the expected value of 81.5 degrees. The average critical angle was determined from the simulated results. Additionally, a lower percentage error of -51% was observed at the moment of disturbance. The 4th order Runge-Kutta numerical technique is superior due to its sustainability, faster computation, and stability in the presence of transient disturbances, as demonstrated in the study case. It is crucial to promptly and accurately coordinate the circuit breakers and protection relays in order to rapidly clear a symmetrical 3 phase fault at any bus. This will improve the stability margin of the network.

Upgrading the dynamic mathematical model of temperature sensors in gaseous media for low Biot number (Bi < 0.1)

A mathematical model incorporating the transient response of NTC thermistors is presented. The internal thermal conduction resistance of the sensor relative to the thermal convection resistance of the medium results in a low Biot number Bi<0.1, yielding a fast dynamic response in gaseous media. This is advantageous in applications requiring minimal fluid interaction. However, negligible energy exchanges occur, introducing measurement uncertainty and ignoring the behavior of the measuring instrument. Therefore, this work proposes an improvement strategy for the mathematical model of these sensors, complementing the conventional model based on the concept of time constant. The strategy considers the heat flow through the thermistor wires in the energy balance, assuming they are semi-infinite solids and applying an approximation to the heat flow formula. Satisfactory improvement results were obtained compared to the conventional model, based on controlled laboratory tests with various gases.

Investigation of containment spraying characteristics based on the correction of droplet evaporation shielding effects

Historically, the spray models in the accident analysis program are mostly based on the isolated droplet and ignore the shielding effects among droplets, which theoretically introduces some errors. This paper investigates the effect of multi-droplet shielding on spray evaporation by taking the containment spray systems as the research object. By discussing the correction factors, the law of droplet group shielding effects can be studied, and then the correction of the spray package can be realized by the self-programming. After that, the transient response characteristics of temperature and pressure in the containment before and after the model correction are studied by modeling the loss of coolant accident and main steam line break accident, respectively. And, this research tries to analyze the influence of the cell normalization model as well as spray parameters on the calculation results. The results reveal that the program can achieve more accurate prediction after being modified by the shielding effects, and the multi-cell model can capture the temperature stratification effects more accurately under accident conditions. Additionally, the spray temperature and spray sizes have an insignificant effect on the in-shell thermal hydraulics response characteristics, but the increase of the spray flow rate has a better effect on the mitigation of the temperature stratification effects and the suppression of the in-shell pressure. The research in this paper can provide some reference or research ideas for accurate modeling and safety analysis of accidents.

Analysis and design of high‐frequency multiple‐output wireless power transfer system with load‐independent class‐E/F inverter

AbstractThis paper proposes a high‐frequency multiple‐receiver wireless power transfer (WPT) system with a load‐independent class‐E/F inverter. Each receiver has a post‐regulator, which changes the equivalent resistance seen from the inverter to obtain the necessary power for output voltage regulation. Because the load‐independent class‐E/F inverter generates constant AC current ( ), the transmitter supplies the minimum required power to the receivers by the change of the equivalent resistances. Besides, the load‐independent inverter consistently achieves zero‐voltage switching (ZVS) without any control. As a result, no information feedback by wireless communication is necessary for output regulation and ZVS achievement, simplifying the system configuration and improving the transient response of the control. This paper presents analytical expressions of the proposed system. Besides, the experiment was carried out with a two‐receiver WPT system. The implemented system worked well by individual and independent output regulation of the post regulator at each receiver. The implemented WPT system achieved the power‐delivery efficiency of 83.4% at the 6.78 MHz transmission frequency and the total output power of 40 W.

Analysis of the dynamic response for Kirchhoff plates by the element-free Galerkin method

Dynamic response analysis involves examining structural behavior under dynamic loading conditions. Transient dynamic analysis emerges as a method employed to assess the responses of deformable bodies. Due to the depth analysis of transient responses for thin plates, the associated error analysis work becomes particularly important. In this work, we conduct stability and convergence analysis of the element-free Galerkin (EFG) method for the dynamic response of Kirchhoff plate model. We start by discretizing the thin plate dynamics using the EFG method for the spatial domain and the central difference scheme for the temporal domain. Stability and convergence analysis for transient responses, including deflection and moment responses, are derived similarly to those in two-dimensional transient structural dynamic analysis. The key to the analysis is transforming the governing equations and clamped boundary conditions into a weak formulation with penalty terms using the penalty method. The main results demonstrate a significant correlation between the error estimate and both nodal spacing and time step size. Additionally, the continuity of the approximation functions and the selection of penalty factors significantly affect numerical accuracy. To validate the theoretical results, we conduct numerical experiments involving clamped square and L-shaped plates with uniform and nonuniform node distributions, as well as a perforated plate model. Furthermore, we investigate the impact of node influence domains and penalty factors on numerical accuracy, facilitating parameter selection for practical engineering applications.

Frequency-adaptive odd-harmonic repetitive control scheme for three-phase shunt active power filters

Repetitive control (RC), which can track the periodic input or suppress the periodic disturbance with a zero steady-state error, is a promising control strategy for shunt active power filters (SAPF). However, the conventional RC (CRC) scheme will suffer a severe performance degradation caused by the grid frequency variations. In this article, a frequency-adaptive odd-harmonic repetitive control scheme with a single and fixed sampling rate is proposed for SAPF to deal with grid frequency variations and provide fast transient response for RC system. The frequency-adaptability of proposed repetitive control scheme can be implemented by updating the coefficients of the approximate expression for the delay unit in repetitive controller. The FIR filter based on Lagrange linear interpolation is used to transform the multirate repetitive control system into single-rate repetitive control system to address the problems caused by the multirate repetitive control system. Moreover, a fractional-order linear compensator with a simple structure is designed to compensate the magnitude and phase of the system accurately. Compared with other classical repetitive control strategies, the proposed repetitive control scheme can provide a better adaptation to the steady-state deviation and dynamic variation of grid frequency and ensure the control performance of SAPF system. Simulation and experimental results verify the effectiveness of the proposed control scheme.

Size-dependent transient response of sandwich microbeam with three-phase bidirectional FGM face layers under a moving mass

Size-dependent transient response of sandwich microbeam with three-phase bidirectional FGM face layers under a moving mass

Ultrafast Coherent Exciton Couplings and Many-Body Interactions in Monolayer WS2.

Transition metal dichalcogenides (TMDs) are quantum confined systems with interesting optoelectronic properties, governed by Coulomb interactions in the monolayer (1L) limit, where strongly bound excitons provide a sensitive probe for many-body interactions. Here, we use two-dimensional electronic spectroscopy (2DES) to investigate many-body interactions and their dynamics in 1L-WS2 at room temperature and with sub-10 fs time resolution. Our data reveal coherent interactions between the strongly detuned A and B exciton states in 1L-WS2. Pronounced ultrafast oscillations of the transient optical response of the B exciton are the signature of a coherent 50 meV coupling and coherent population oscillations between the two exciton states. Supported by microscopic semiconductor Bloch equation simulations, these coherent dynamics are rationalized in terms of Dexter-like interactions. Our work sheds light on the role of coherent exciton couplings and many-body interactions in the ultrafast temporal evolution of spin and valley states in TMDs.

Path integration solutions for stochastic systems with Markovian jumps

A path integration method for solving Markovian jump stochastic dynamical systems is presented. The Markovian jump process and the state vector of the system are combined into a new augmented state vector. The randomness of the Markovian jump is modeled by a stochastic process, which is merged with the stochastic perturbations to form the stochastic source affecting the evolution of the augmented system. Then a probability mapping is constructed, mapping the probability space of the stochastic source to the short-time transition probability density function of the augmented system. By solving this probability mapping, the short-time transition probability density function of the path integration method is obtained, thus a path integration method is customized for Markovian jump stochastic systems. Finally, a hydraulic relief valve system is used as an application example to demonstrate the availability of the path integration algorithm. The results suggest that the pre-compression parameters and coefficient of restitution of the plug can induce stochastic P-bifurcation phenomena. When the above two parameters are small, the system becomes unstable with the parameters taken in this example. Monte Carlo simulations prove that the proposed method effectively captures the transient and stationary responses of Markovian jump systems.

Design and characterization of a pyroshock reduction structure based on local resonance mechanisms

In the spacecraft Pyrotechnic shock process, the explosion generated by the strong shock wave and preload force release of the vehicle structure produces a transient, high-frequency, and high-amplitude shock response, resulting in a harsh shock environment prone to failure or damage to many precision equipment or components on the spacecraft, a fatal impact on the launch mission. This paper designed a local resonance shock mitigation structure based on local resonance theory for the Pyrotechnic shock environment and optimized the parameters of the structure by the genetic algorithm. A Pyrotechnic shock simulation experimental device was built to verify the impact reduction effect of the designed shock reduction structure. This experimental device can well restore the pyrotechnic shock environment. In addition, a finite element simulation model was established, and the impact reduction effect of the protective structure was verified both numerically and experimentally. The experimental and numerical analysis results show that the impact response decays significantly in the structural band gap range with the same transfer path, and the shock response spectrum amplitude decreases 9.8 dB in the 100–10,000 Hz frequency band.

A new adaptive droop control strategy for improved power sharing accuracy and voltage restoration in a DC microgrid

In a DC Microgrid, accurate power sharing and voltage restoration are two primary control goals to guarantee power quality and reliable operation. Inaccurate power sharing is a significant concern due to discrepancies in feeder line resistance, faulty equipment, lack of monitoring and control, and nonlinear load. Moreover, inaccurate power sharing may lead to overloading of converters and cause a cascade of failures throughout the entire system. This study proposes a new adaptive droop control strategy to address these challenges. To enhance accurate power sharing, error current sharing is formulated by considering bus current and total rated current. This is regulated by the adaptive controller to adjust droop resistance. Additionally, the impact of droop voltage because of feeder line resistance is considered in the proposed strategy. The primary control loop regulates the output voltage of converter utilizing the proposed observer-based optimum sliding mode control (OOSMC). The controller gain of the OOSMC is optimized using a gradient-based method to enhance transient and steady state response of the converter output. In the secondary loop, the twin-delayed deep deterministic policy gradient (TD3) for voltage restoration is employed with a new reward function to optimally tune the proportional-integral (PI) controller. Finally, the superiority of the proposed strategy is evaluated through rigorous testing scenarios, including the use of constant power load (CPL) and sudden failure in the converters. Moreover, the proposed strategy is validated by simulations and laboratory-based experiments. The results show that the OOSMC outperforms GA and PSO while the TD3 has better performance than traditional PI. Furthermore, when the equivalent power-rated converters are implemented in the system, the proposed strategy can transfer identical power sharing of 4 W to the load and provide accurate current sharing of 0.167 A compared to conventional droop control while the DC bus voltage is maintained at the 24 V reference value. In the case of different power-rated converters, the proposed strategy can achieve power sharing accuracy. The first, second and third converters supply 2 W, 4 W, and 6 W, respectively, to the load and provide accurate current sharing. Meanwhile the DC bus voltage can be kept at the reference voltage of 24 V. In the scenario of various kinds of disturbances, the proposed strategy can achieve accurate power and current sharing when the system is tested under load and input voltage variations. Meanwhile the DC bus voltage always returns to the voltage reference. Moreover, the proposed strategy can share power and current accurately when the converter occurs a sudden failure.

HGG-41. COMBINATORIAL BH3-MIMETIC STRATEGY FOR OVERCOMING RADIORESISTANCE IN PEDIATRIC HIGH-GRADE GLIOMA

Abstract BACKGROUND High-grade gliomas (HGGs) are a leading cause of cancer-associated death in children. Radiation therapy (RT) continues to be the only standard-of-care treatment across HGG subtypes, but disease frequently recurs following only a transient response. We have recently identified that HGGs utilize the pro-survival BCL-2 family of proteins to evade cell death after radiation, and we demonstrated that effective inhibition of BCL-2 with the CNS-penetrant drug venetoclax could be utilized to disrupt this resistance and augment radiation-induced cell killing. While this treatment significantly prolonged survival in orthotopic mouse models of pediatric HGG, tumors invariably developed resistance to single-agent venetoclax and recurred. METHODS We profiled tumors from venetoclax-resistant animals for alternate BCL-2 family binding. We then assessed susceptibility to MCL1 inhibition in venetoclax-treated or treatment naïve culture models. Synergy was tested in vitro, and mitochondrial ROS production and induction of apoptosis was assessed using the MCL1-specific agent S63845. Finally, venetoclax and S63845 were tested in combination following fractionated radiotherapy in orthotopic models of DIPG. RESULTS MCL1 is an acquired dependency following treatment with RT + venetoclax. S63845 synergizes with venetoclax following RT to drive mitochondrial ROS production and apoptosis. The combination of venetoclax and S63845 significantly prolongs survival in xenograft models of DIPG. CONCLUSIONS Combinatorial targeting with BH3 mimetics augments radiation-induced cell killing and may open new therapeutic avenues for pediatric HGG.

An intelligent aortic valve model for complete cardiac cycle.

The aortic valve (AV) is crucial for cardiovascular (CV) hemodynamic, impacting cardiac output (CO) and left ventricular volumetric flow rate (LVQ). Its nonlinear behavior challenges standard LVQ prediction methods as well as CO one. This study presents a novel approach for modeling the AV in the CV system, offering an improved method for estimating crucial parameters like LVQ across various AV conditions, including aortic stenosis (AS). The model, based on AV channel length during the entire cardiac phase, introduces a time-varying AV resistance (TV-AVR) parameterized by the pressure ratio across the AV and LVQ, enabling the simulation of both healthy and AS-related conditions. To validate this model, in vitro measurements are compared using a hybrid mock circulatory loop device. An unconventional use of a convolutional neural network (CNN) corrects the model's estimates, eliminating the need for labeled datasets. This approach, incorporating real-time learning and transforming 1-D CV signals into 2-D tensors, significantly improves the accuracy of LVQ measurements, achieving an error rate of less than 3.41 ± 4.84% for CO in healthy conditions and 2.83 ± 1.35% in AS cases-a 33.13% enhancement over linear diode models. These results underscore the potential of this approach for enhancing the diagnosis, prediction, and treatment of AV diseases. The key contributions of the proposed method encompass nonlinear TV-AVR estimation, investigation of transient CV responses, prediction of instantaneous CO, development of a flexible framework for noninvasive measurements integration, and the introduction of an adjustable resistance model using an extended Kalman filter (EKF) and CNN combination, all without requiring labeled data.

Dynamic modeling and identification of a reluctance synchronous machine parameters

This article discusses an identification and modeling approach of a reluctance synchronous motor (RSM) based on the running rotor technique. The applied flux linkage approximation functions reflect the self-saturation and cross-saturation effects, and the applied mathematical model is continuous and differentiable. The proper design of the experiment is discussed, and relevant recommendations are made to ensure the mitigation of procedural mistakes in the experiments. A detailed analysis of the impact of configuration faults on the obtained experimental data is provided, considering distortions in the obtained flux linkage and inductance surfaces. Considering the achieved model accuracy, a novel model evaluation considering the achieved model accuracy technique based on transient current response is proposed.

Ultrafast Opto-Electronic and Thermal Tuning of Third-Harmonic Generation in a Graphene Field Effect Transistor.

Graphene is a unique platform for tunable opto-electronic applications thanks to its linear band dispersion, which allows electrical control of resonant light-matter interactions. Tuning the nonlinear optical response of graphene is possible both electrically and in an all-optical fashion, but each approach involves a trade-off between speed and modulation depth. Here, lattice temperature, electron doping, and all-optical tuning of third-harmonic generation are combined in a hexagonal boron nitride-encapsulated graphene opto-electronic device and demonstrate up to 85% modulation depth along with gate-tunable ultrafast dynamics. These results arise from the dynamic changes in the transient electronic temperature combined with Pauli blocking induced by the out-of-equilibrium chemical potential. The work provides a detailed description of the transient nonlinear optical and electronic response of graphene, which is crucial for the design of nanoscale and ultrafast optical modulators, detectors, and frequency converters.

Transient behavior of a plate partially immersed in the fluid subjected to impact loadings: Theoretical analysis and experimental measurements

This study aimed to investigate the transient behavior of a rectangular plate partially in contact with fluid subjected to a dynamic external force. To this purpose, a theoretical model was developed to analyze vibration characteristics and transient wave propagation. Based on superposition method, the dry mode shapes and natural frequencies of the plate under vacuum could be obtained. The dry mode shapes were treated as the fundamental function to construct the wet mode that describes the vibration behavior of the fluid-plate coupled system. The velocity potential and fluid pressure within a finite tank due to the plate deflection were derived using an equation governing the incompressible fluid. Based on the relationship between dry mode shape and wet mode shape, the fluid-plate coupled system's wet mode shape and resonant frequency could be determined from the frequency response function. Applying the normal mode method, the transient displacement of plate and fluid pressure can be obtained by solving a system of non-homogeneous differential equations. The theoretical predictions were verified by finite element method (FEM) and experimental measurements. Experiments were conducted using piezoelectric film sensors (polyvinylidene fluoride, PVDF) to measure the force history induced by a steel ball impact to quantitatively analyze the transient response. The comparison results proved that the theoretical predictions and experiments were in good agreement, including the transient responses of the displacement and in-plane strain of a plate partially submerged in the fluid. The results indicate that changes in water depth can induce resonance frequency shifts and wet mode shape distortions, which also illustrate that the vibrational properties of wet modes affect transient behavior. The proposed transient solution demonstrates an analytical approach that connects the physical significance of the dynamic behavior of the fluid-plate coupled system in time and frequency domains; it provides a connection between the transient behaviors and vibration characteristics.

Paired metabolomics and volatilomics provides insight into transient high light stress response mechanisms of the coral Montipora mollis

The coral holobiont is underpinned by complex metabolic exchanges between different symbiotic partners, which are impacted by environmental stressors. The chemical diversity of the compounds produced by the holobiont is high and includes primary and secondary metabolites, as well as volatiles. However, metabolites and volatiles have only been characterised in isolation so far. Here, we applied a paired metabolomic-volatilomic approach to characterise holistically the chemical response of the holobiont under stress. Montipora mollis fragments were subjected to high-light stress (8-fold higher than the controls) for 30 min. Photosystem II (PSII) photochemical efficiency values were 7-fold higher in control versus treatment corals immediately following high-light exposure, but returned to pre-stress levels after 30 min of recovery. Under high-light stress, we identified an increase in carbohydrates (> 5-fold increase in arabinose and fructose) and saturated fatty acids (7-fold increase in myristic and oleic acid), together with a decrease in fatty acid derivatives in both metabolites and volatiles (e.g., 80% decrease in oleamide and nonanal), and other antioxidants (~ 85% decrease in sorbitol and galactitol). These changes suggest short-term light stress induces oxidative stress. Correlation analysis between volatiles and metabolites identified positive links between sorbitol, galactitol, six other metabolites and 11 volatiles, with four of these compounds previously identified as antioxidants. This suggests that these 19 compounds may be related and share similar functions. Taken together, our findings demonstrate how paired metabolomics-volatilomics may illuminate broader metabolic shifts occurring under stress and identify linkages between uncharacterised compounds to putatively determine their functions.