Mode Switching Research Articles

Disulfide-Driven Charge and Hydrophobicity Rearrangement of Remodeled Membrane Proteins toward Amyloid-Type Aggregation.

As a common pathological hallmark, protein aggregation into amyloids is a highly complicated phenomenon, attracting extensive research interest for elucidating its structural details and formation mechanisms. Membrane deposition and disulfide-driven protein misfolding play critical roles in amyloid-type aggregation, yet the underlying molecular process remains unclear. Here, we employed sum frequency generation (SFG) vibrational spectroscopy to comprehensively investigate the remodeling process of lysozyme, as the model protein, into amyloid-type aggregates at the cell membrane interface. It was discovered that disulfide reduction concurrently induced the transition of membrane-bound lysozyme from predominantly α-helical to antiparallel β-sheet structures, under a mode switch of membrane interaction from electrostatic to hydrophobic, and subsequent oligomeric aggregation. These findings shed light on the systematic understanding of dynamic molecular mechanisms underlying membrane-interactive amyloid oligomer formation.

Grid-Forming Control for Solar Generation System with Battery Energy Storage

Solar generation systems with battery energy storage have become a research hotspot in recent years. This paper proposes a grid-forming control for such a system. The inverter control consists of the inner dq-axis current control, the dq-axis voltage control, the phase-locked loop (PLL) based frequency control, and the DC voltage control. The proposed control embeds the PLL into the grid-forming inverter control, offering the advantages of better synchronization and fault current-limiting capability. With the proposed control, the battery energy storage is able to provide inertial and primary frequency support during the grid frequency disturbance. Simulation models are established in PSCAD/EMTDC, and the results during the active power variation and AC voltage variation, the grid frequency disturbance, grid fault, and mode switch validate the effectiveness of the proposed control.

Dynamic analysis of cracked pipe elbows: Numerical and experimental studies

This study aims to investigate the dynamic behaviors of fluid-delivering cracked pipe elbows (FDCPEs), thereby providing theoretical and methodological guidance for vibration-based crack detection in pipe elbows. Specifically, an efficient spectral element-finite element (SE-FE) based modeling method for the FDCPEs is proposed firstly, which considers fluid-structure coupling and breathing effect. For the SE-FE method, the spectral element (SE) and finite element (FE) are constructed to simulate the healthy straight segments and cracked elbows of the pipe, respectively, and a penalty function method is adopted to simulate interface coupling and breathing effects. Furthermore, the computational accuracy and efficiency of the SE-FE method are verified through numerical and experimental studies. Finally, the effects of the elbow and crack parameters on the dynamic behaviors of FDCPE are analyzed. The results indicate that changes in the bending radius and angle may trigger frequency veering behaviors, leading to in-plane and out-plane vibration mode switching. Moreover, the even-mode harmonics of the stress responses can effectively detect cracks in the elbow. Most importantly, the strength of nonlinearity at different measuring locations can be used to predict the crack location and size.

Fault Handling and Localization Strategy Based on Waveform Characteristics Recognition with Coordination of Peterson Coil and Resistance Grounding Method

To address challenges in locating high-impedance grounding faults (HIGFs) and isolating fault areas in resonant grounding systems, this paper proposes a novel fault identification method based on coordinating a Peterson coil and a resistance grounding system. This method ensures power supply reliability by extinguishing the fault arc during transient faults with the Peterson coil. When a fault is determined to be permanent, the neutral point switches to a resistance grounding mode, ensuring regular distribution of zero-sequence currents in the network, thereby addressing the challenges of HIGF localization and fault area isolation. Fault calibration and nature determination rely on recognizing neutral point displacement voltage waveforms and dynamic characteristics, eliminating interference from asymmetric phase voltage variations. Fault area identification involves assessing the polarity of zero-sequence current waveforms attenuation during grounding mode switching, preventing misjudgments in grounding protection due to random initial fault angles and Peterson coil compensation states. Field experiments validate the feasibility of this fault location method and its control strategy.

STAR-RIS-assisted key generation method in quasi-static environment

In this paper, we introduce a new method to solve the low-entropy problem in a quasi-static environment. We utilize a simultaneous transmission and reflection reconfigurable intelligent surface (STAR-RIS) that transmits and reflects incoming signals to users located on different sides of the surface. Specifically, we design the flow of multi-user channel probing when STAR-RIS is assisted, analyze and derive the analytical expression of the secret key capacity (SKC) of STAR-RIS-assisted system from the perspective of information theory, and finally analyze how to maximize the SKC and sum of all users under three different working protocols of STAR-RIS. The simulation results show that: (1) STAR-RIS can achieve better SKC performance than the conventional reflection/transmission RIS; and (2) the SKC is determined by the number of STAR-RIS elements, correlation coefficient, pilot length and RIS-reflected channel quality, and the time switching protocol can obtain higher SKC than the energy splitting protocol and mode switching protocol.

A CC/VC‐based power tracking method for photovoltaic inverter operated in voltage control mode

AbstractThe active power control of photovoltaic (PV) inverters without energy storage can flatten the fluctuating power and support the voltage amplitude and frequency of the grid. When operated in grid‐forming voltage‐control mode, because the PV power can change rapidly and widely, the PV inverter needs to track the power commands quickly and precisely. Traditionally, this goal is achieved with the estimation of PV power curve or PI‐based multiple‐loop feedback control, where flexibility, availability and accuracy are not satisfactory. Therefore, a CC/VC‐based power tracking (CVPT) method is proposed, which only uses single‐loop in control. The proposed method does not need to tune multiple loops and can respond faster, which is important for grid‐forming voltage control. Furthermore, the different operating modes due to the limitation of PV maximum power are analysed, and a mode switch method is proposed. Simulation and experimental results demonstrate that the PV inverter can cope with power disturbances from both the power and grid sides and maintain the quality of grid voltage.

Control strategies for mode switching of a large marine two-stroke engine equipped with exhaust gas recirculation and turbocharger cut-off systems

To meet the stringent nitrogen oxides emissions regulations, the recent marine two-stroke engines are equipped with exhaust gas recirculation (EGR) systems. Crossing the boundaries of exhaust control areas requires switching between the engine operating modes associated with the activation or deactivation the EGR system, which imposes challenges to the engine operation. This study aims to develop and numerically test effective control strategies for improving the mode switching of marine two-stroke engines with EGR systems. The investigated engine dynamic model is developed by integrating a zero-dimensional thermodynamic model developed in GT-POWER and the control model developed in MATLAB/Simulink. This model is first validated against the experimentally measured engine performance parameters, and subsequently employed to simulate the engine dynamic operation with mode switching. The simulation results are assessed to quantify the impact of several control strategies on the engine performance. The derived perrformannce parameters time variations demonstrate that the deactivation of the EGR branch and the small engine–turbocharger result in exceeding the manufacturer limits at high loads and increasing the fuel consumption. The proposed load-based control strategies, which employ load thresholds and time delays for the control of the EGR and turbocharging systems activation/deactivation, are proved effective, as the engine performance parameters are retained within their limits and fuel consumption penalties are minimised. This study provides insights for developing the control of the marine engines after-treatment systems, hence contributing towards enhancing shipping sustainability.

Multimode Design and Analysis of an Integrated Leg-Arm Quadruped Robot with Deployable Characteristics

To improve locomotion and operation integration, this paper presents an integrated leg-arm quadruped robot (ILQR) that has a reconfigurable joint. First, the reconfigurable joint is designed and assembled at the end of the leg-arm chain. When the robot performs a task, reconfigurable configuration and mode switching can be achieved using this joint. In contrast from traditional quadruped robots, this robot can stack in a designated area to optimize the occupied volume in a nonworking state. Kinematics modeling and dynamics modeling are established to evaluate the mechanical properties for multiple modes. All working modes of the robot are classified, which can be defined as deployable mode, locomotion mode and operation mode. Based on the stability margin and mechanical modeling, switching analysis and evaluation between each mode is carried out. Finally, the prototype experimental results verify the function realization and switching stability of multimode and provide a design method to integrate and perform multimode for quadruped robots with deployable characteristics.

Short-term Load Forecasting and Regime Switching Detection Based on Normalized Causal Entropy Boosting

Abstract This paper introduces a method based on normalized causal entropy boosting (NCEBoosting) to identify regime switches in load patterns and improve the adaptability of prediction models. Load time-series exhibit multidimensional, nonlinear changes influenced by factors such as human behavior and meteorological environments. To detect regime switches, we calculate the sparsified causal entropy matrix using a small batch of load flow data, which corrects the original prediction model. Subsequently, the corrected model is employed to predict the load requirements after the switch. By comparing the causal entropy across different time periods, we effectively detect conceptual drift, phase changes, and unexpected events in the data, enabling the determination of load mode switches. Given that load timing data is typically generated in batches, calculating the causal entropy of successive data batches provides a robust metric. In this paper, we determine the load mode change by calculating the integrated causal entropy of the batch data streams and calibrating the prediction model accordingly. Extensive computational experiments on real building load datasets are conducted to validate the proposed method. The results demonstrate that the normalized causal entropy boosting effectively detects load mode switches compared to traditional approaches. Furthermore, the method demonstrates efficient adaptive learning based on online data streams, resulting in improved adaptability and prediction accuracy.

Energy management strategy for electro-hydraulic hybrid electric vehicles considering optimal mode switching: A soft actor-critic approach trained on a multi-modal driving cycle

Hybrid electric vehicles (HEVs) feature multiple working modes. Thoughtful selection of these modes can optimally balance driving performance, power demands, and energy consumption, thereby enhancing the overall efficiency of the vehicle. This paper presents a soft actor-critic (SAC) approach trained on a multi-modal driving cycle (MDC) for selecting operational modes of electro-hydraulic hybrid electric vehicle (EHHEV). Firstly, characteristic parameters are extracted and clustered for five typical driving cycles through principal component analysis and K-means clustering, creating a multi-modal driving cycle. Secondly, based on the operational characteristics of EHHEV, state variables, action variables, reward functions, learning rates, and other parameters are set for the SAC algorithm, and the EMS framework is built based on the electro-hydraulic hybrid electric power system. Subsequently, the SAC algorithm is trained using the MDC to construct the SAC-MDC EMS. Results demonstrate that compared to EV, RB EMS, and SAC EMS, IREC achieves maximum improvements of 22.38 %, 5.55 % and 0.80 %, respectively. The dynamic performance and the motor load optimization capability are also enhanced. To further validate the practicality and reliability of the SAC-MDC EMS, this paper validates it using actual driving data, revealing that it still exhibits outstanding performance.

Transient characterization of the mode switching process in the reversible solid oxide cell stack

Reversible solid oxide cells (RSOCs) is a promising energy storage and conversion technology requiring frequent switching between fuel cell mode and electrolysis mode in practice. Unfortunately, it may cause a large current density undershoot that has irreversible damage to the RSOC. Therefore, understanding the transient behaviors of the RSOC is critical for its efficient and durable operation. A three-dimensional transient model of a 30-cell SOC stack with an external manifold is established. From SOFC to SOEC, the mass transfer lag and slow heat transfer cause the current density of the stack requiring 2500 s to reach a steady state. And the bottom inlet way and the external manifold structure cause differences in the current density, molar fraction and temperature variation with time between different cells. The upper cells show a slower mass transfer rate and undergo greater temperature changes. The inconsistent temperature change gradients and temperature change rates among different cells will inevitably produce changing thermal stresses and bring irreversible mechanical losses to the stack. Similar transient characteristics are observed when switching from SOEC to SOFC. However, it takes longer time (3200 s) to achieve the final steady state.

Protocol-based SMC for singularly perturbed systems with switching parameters and deception attacks

This research paper investigates a protocol-based sliding mode control (SMC) approach for singularly perturbed systems with switching parameters and random occurring deception attacks. The mode switching behavior of the original system is regulated using a semi-Markov process, and a novel and more efficient mode monitoring method is proposed, distinct from the conventional hidden Markov model. Furthermore, to reduce the triggering rate while maintaining control performance, a probability-based event triggering protocol is introduced. By employing the proposed scheme along with Lyapunov theory, sufficient criteria for parameter correlation are established to ensure asymptotic stability. The designed sliding mode control incorporates a convergence factor to enhance the control performance. Finally, the feasibility and practicality of the proposed control strategy are verified through simulations using two practical models.

A complete dynamic modeling of two-by-one gas-steam combined cycle unit for coordinated control design

The high penetration of renewable energy can potentially change the role of combined cycle gas turbines (CCGT) from load suppliers to flexible suppliers. However, the slow process in the dynamic modeling of the CCGT complete system restricts the design of its best flexible operation strategy. Therefore, this paper adopts the composite modeling method to establish a complete nonlinear dynamic model of a 2 × 1 CCGT including two gas turbines, two three-pressure heat recovery steam generators (HRSG), one steam turbine, and one heat exchanger. This model can reflect the dynamic characteristics of pressure and flow in the bottom cycle due to the changes in operating mode, which can guide the design of the flexible operation control strategy of the 2 × 1 CCGT. To verify the model’s accuracy, the simulated data were compared with the field data from a 900 MW cycle with the same configuration. The results show that the established model can accurately reflect the changing trend of variables during mode switching. The range errors of essential variables such as gas turbine (GT) power is 3.8 %, GT outlet temperature is 1.4 %, high-pressure drum pressure is 4.5 %, and the range errors of other variables are below 5 %, proving the fidelity of the established control model. The dynamic model established in this paper will be the basis for model-based controller design which can handle multi-objective optimization and constraints in flexible operations. Moreover, this model will be used to guide the design of multi-mode control and energy management strategies.

Temporal mode switching during polariton condensation

Multimode behavior plays a key role in a wide range of nonlinear optical phenomena. Multiple exciton-polariton modes can attain macroscopic population as observed in time-integrated measurements. Recent theory work has shown that, rather than being simultaneously in many modes, the population may temporally switch between the modes. However, the origin and the dynamics of multimode condensation has not been experimentally addressed. Here, we study the dynamics of exciton-polariton condensation into multiple modes of Gaussian defect microcavities filled with ladder type polymer gain material methyl-substituted ladder-type poly(p-phenylene) MeLPPP. We deploy a second-order cumulant model to simulate the dynamics of the system and find picosecond-timescale switching between condensate modes. By interferometric measurements we reveal the experimental signatures of such mode competition behaviour.

A Coordinated Mode Switch Control Strategy for a Two-Gear Power-Split Hybrid System

A Coordinated Mode Switch Control Strategy for a Two-Gear Power-Split Hybrid System

Topological unwinding in an exciton-polariton condensate array

The phase distribution in a Bose-Einstein condensate can realize various topological states classified by distinct winding numbers. While states with different winding numbers are topologically protected in the linear Schrödinger equation, when nonlinearities are introduced, violations of the topological protection can occur, leading to unwinding. Exciton-polariton condensates constitute a nonlinear open-dissipative system that is well suited to studying such physics. Here we show that a one-dimensional array of exciton-polariton condensates displays a spontaneous phase unwinding from a π- to zero-state. We clarify that this collective mode transition is caused by the combined effect of nonlinearity and topological defects in the condensates. While the mode-switching phenomenon observed in our previous experiment was interpreted as the single-particle mode competition, we offer an alternative explanation in terms the collective phase unwinding and find its evidence by reanalyzing the experimental data. Our results open a route towards active control of the mode switching by manipulating the topological defects in prospective quantum polaritonic devices.

Optical integrated reconfigurable mode generator-multiplexer for radio-frequency orbital angular momentum.

Radio-frequency orbital angular momentum (RF-OAM) mode multiplexing has received increasing attention in next-generation (6G) wireless communication as a new spatial multiplexing dimension to further extend data capacity. In particular, the circular antenna array (CAA) based RF-OAM generation using photonic methods is a promising approach due to its flexible reconfigurability, low propagation loss, high operating bandwidth, and high pattern quality. However, most current reports focus either on the bulk optics-based implementations or on band-limited delay line-based approaches. In this paper, we present a novel phased array-based integrated photonic RF-OAM generator-multiplexer for a four-antenna CAA system supporting three RF-OAM modes at 16 GHz for both fast mode switching and mode multiplexing. It consists of a specially designed interleaved optical filter and a four-element phased array based on cascaded phase shifters. By changing the pair of wavelengths used, the output RF-OAM modes can be quickly switched between fundamental mode and ±1 modes. A bandwidth of 1 GHz was experimentally demonstrated. Mode multiplexing can be achieved when all three wavelength pairs are loaded.

Robust generalised predictive position control for chain‐type rotary shell magazine with disturbance observer

AbstractThe realisation of fast position tracking control and strong robust control of the chain‐type rotary shell magazine in the complex systems such as the large calibre howitzer has been the focus and challenge of research. The predictive control strategies can achieve a fast dynamic response, but it relies on the system model. By integrating the generalised predictive control method with sliding mode theory, a novel robust generalised predictive position control method is proposed. Firstly, a non‐cascade position tracking controller is designed based on the continuous‐time model of the systems; then, a sliding mode compensation structure is introduced to address the degradation of control performance due to load variations and external disturbances. The scheme utilises the sliding mode switching term to overcome the effects caused by the disturbances while preserving the fast dynamic response characteristics of the original predictive control. Moreover, the disturbance observer is designed to further enhance the robustness by producing corresponding compensation according to the perturbation quantity. The proposed controller has been validated in a shell magazine test bench, indicating its superior position control performance of the shell magazine under different load conditions.

Statistical analysis of bistable feature in a 1.55-[formula omitted] vertical cavity emitting laser

Optical bistability in telecom-band lasers has attracted significant attention because of its immense potential for applications in the fields of optical communications and optical computing. In this paper, we report on an experimental investigation of the statistical properties of a 1.55-μm bistable VCSEL. The VCSEL exhibits mode switching at a current of 5.41 mA and 4.15 mA when the pump continuously increases and decreases, respectively. Both of these switching exhibit a bistable region, indicating a polarization bistability induced by the gain saturation. By calculation of second-order autocorrelation functions with injection current, we identify different regions associated with the dynamics of different dominant modes. In particular, the statistical analysis reveals more properties of the bistable laser, such as the intensity fluctuations induced by different kinds of noise.

Electromechanically Reconfigurable Terahertz Stereo Metasurfaces.

Dynamic terahertz devices are vital for the next generation of wireless communication, sensing, and non-destructive imaging technologies. Metasurfaces have emerged as a paradigm-shifting platform, offering varied functionalities, miniaturization, and simplified fabrication compared to their 3D counterparts. However, the presence of in-plane mirror symmetry and reduced degree of freedom impose fundamental limitations on achieving advanced chiral response, beamforming, and reconfiguration capabilities. In this work, a platform composed of electrically actuated resonators that can be colossally reconfigured between planar and 3D geometries is demonstrated. To illustrate the platform, metadevices with 3D Split Ring Resonators are fabricated, wherein two counteracting driving forces are combined: i) folding induced by stress mismatch, which enables non-volatile state design and ii) unfolding triggered by the strain associated with insulator-to-metal transition in VO2, which facilitates volatile structural reconfiguration. This large structural reconfiguration space allows for resonance mode switching, widely tunable magnetic and electric polarizabilities, and increased frequency agility. Moreover, the unique properties of VO2, such as the hysteretic nature of its phase transition is harnessed to demonstrate a multi-state memory. Therefore, these VO2 integrated metadevices are highly attractive for the realization of 6G communication devices such as reconfigurable intelligent surfaces, holographic beam formers, and spatial light modulators.