Transient Response Research Articles

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.

Viscoelastic Rheological Modelling of the Lateral Dynamic Response of Ballasted Railway Tracks

This article presents a novel methodology for evaluating the response of ballasted railway tracks under train-induced loading along lateral directions. The main focus of this study is the development of a computational technique that can capture the lateral response of ballasted railway tracks, which has been ignored in past studies. The proposed approach employs a viscoelastic rheological track model in which three substructure layers are simulated using discrete masses, Hooke’s (springs) and Newtonian elements (dampers). The methodology is successfully validated against the data from experimental and analytical investigations published in the literature. Subsequently, parametric investigations are conducted to study the influence of axle load, train speed, and granular layer thickness on the track response. The results indicate that as the axle load (20 to 40 t) and train speed (70 to 200 km/h) are increased, there is a corresponding increase in track displacements (both lateral and vertical) by 100% and 26.2%, respectively. However, an increase in the granular layer thickness (0.1 to 0.75 m) reduces ballast top displacement (lateral and vertical) by 20–30%. The results demonstrate the capability of the proposed computational approach to capture the transient response of railway tracks and the influence of neighbouring layer properties on the track response. The proposed methodology can be helpful to practising railway engineers for assessing the performance of ballasted railway tracks along lateral directions.

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.

Microsatellite Yaw-axis Attitude Control System Using Model Reference Adaptive Control Based PID Controller

This paper presents a Model Reference Adaptive Control (MRAC) based Proportional Integral and Derivative (PID) controller for microsatellite yaw-axis Attitude Control System (ACS). The objective is to combine the algorithm of MRAC with PID to improve the performance of a microsatellite system especially settling time. MRAC based PID controller for yaw-axis ACS was modelled and simulated in MATLAB/Simulink to meet transient response characteristics specifications. The performance of the system was evaluated in terms of rise time, settling time, maximum overshoot, and steady-state error including energy consumption measured based on armature voltage of the direct current motor. The simulation results revealed that the proposed system meets all the performance specifications and outperformed classical PID controller for adaption gain of 0.2 to 20. When compared with PID and Proportional Derivative (PD) based Controllers in previous study for adaption gain of 10, 15, and 20, the proposed system proved to be superior. Generally, the choice of the MRAC based PID controller considering the range of adaption gain (γ = 0.1 to 20) should be based on either transient response advantage or energy consumption or even both over PID controller. The significance of this study is that an MRAC based PID controller that offered wide range of adaption capability for microsatellite ACS has been proposed.

Dimension reduction approach for understanding resource-flow resilience to climate change

Networked dynamics are essential for assessing the resilience of lifeline infrastructures. The dimension-reduction approach was designed as an efficient way to map the high-dimensional dynamics to a low-dimensional representation capturing system-level behavior while taking into consideration network structure. However, its application to socio-technical systems has not been considered yet. Here, we extend the dimension-reduction approach to resource-flow dynamics in multiplex networks. We apply it to the San Francisco fuel transportation network, considering the flow between refineries, terminals and gas stations. We capture the aggregated dynamics between the facilities of each type and identify macroscopic conditions for the system to supply a given demand of fuel. By considering multiple sea level rise scenarios between 2020 and 2100, we address the impact of coastal flooding due to climate change on the maximum suppliable demand. Finally, we analyze the system’s transient response to production failures, investigating the temporary interruption in production and the duration it takes for complete demand satisfaction to become unachievable after the interruption.

A universal pre-charging method for enhancing transient speed in Organic Electrochemical Transistors

Organic electrochemical transistors (OECT) have shown great potential in diverse applications; however, in many OECTs, their slow transient response has thus far limited their practical use. One reason for the slow response is the complex interplay between lateral and vertical ion transport that has so far been poorly understood. In this work, we study the impact of lateral ion transport on OECT transient response, introduce a robust pre-charging method to manipulate the slow lateral ion transport. This approach leads to quicker ion redistribution and improved switching speeds. We show the general utility of pre-charging method in enhancing the switching speeds across various material systems, characterized by both low and high ion mobilities, and across different device architectures, achieving nearly symmetric speeds for both on-switching and off-switching. Moreover, we showcase the efficacy of the pre-charging method in enabling slow OECTs to capture rapid signals in real-world applications. Our findings present a groundbreaking strategy for enhancing the response times of OECT devices and deepening our understanding of the transient mechanisms in OECT device.

Adaptive fuzzy integrated LMS based control strategy for voltage power quality enhancement

In this paper, an adaptive Takagi Sugeno (TS) Fuzzy integrated Mixed Order Normalized Least Mean Square/Fourth Algorithm (MONLMS/F) is proposed for the unresolved voltage power quality issues in distribution system. The proposed control utilizes the cost function of mixed order of errors, which are based on second and fourth order and the feature of cost function overcomes the demerit of traditional basic least mean square method, which is based on second-order error. The implemented control technique has two main objectives. Firstly, the fundamental estimation of correct active and reactive signals from polluted grid voltage for computing the reference load voltages and second is the DC link voltage regulation. A correct weight estimation is achieved by Mixed Order Normalized Least Mean Square/Fourth Algorithm (MONLMS/F) and voltage regulation is performed by Takagi Sugeno Fuzzy (TSF) approach. The proposed integrated control enhances the capability of system against voltage deviation from the reference voltage and successfully eliminates the harmonics from polluted grid voltages. A bio-inspired optimizer like Spotted Hyena (SH) is integrated with TSF for self-tuning of the membership functions (MFs) and fuzzy rule to adapt the system variations and regulate fluctuations in the DC link for dynamic conditions. However, auto-tunned TS-Fuzzy have a fast transient response of DC and AC link voltage based on dynamic indicators like settling time (ts=0.12 s), undershoot (Us=3.4 %) and peak overshoot (Mp=5.6 %) are compared to classical PI controller. Nonetheless, the proposed TS-MONLMS/F control strategy outperforms the other classical control with low oscillations at any power quality scenario with improved dynamic response. The significant MATLAB simulation and experimental results are evaluated, and its performance is demonstrated with the dSPACE (DS1202) processor for experimental realization.