Switching Time Research Articles

Event-triggered resilient control of nonlinear multi-agent systems with disturbances under DoS attacks and directed switching topologies

This paper addresses the issue of resilient event-triggered consensus control for nonlinear multi-agent systems (MASs) operating in non-ideal communication networks. Specifically, it focuses on the challenges posed by directed switching topologies, disturbances and denial-of-service (DoS) attacks. A new approach is introduced to study the consensus tracking problem with a dynamic leader. The proposed strategy utilises a resilient event-triggered consensus tracking control framework, which comprises an event-triggered controller (ETC) and an event-triggering mechanism (ETM). By establishing matrix inequalities and considering parameters associated with DoS attacks and average dwell time, sufficient conditions for solving H ∞ consensus tracking problem are derived. One characteristic of the designed ETM is that events only occur at the triggering or switching time, preventing Zeno behaviour. Furthermore, a resilient event-triggered control strategy is suggested to tackle the containment problem with multiple dynamic leaders. Finally, the effectiveness of the designed control strategies is demonstrated through numerical simulations.

Intermittent Optimization of Shale Gas Wells Based on Reservoir–Wellbore Coupling

Shale gas, as an important component of unconventional energy, holds enormous potential value in the energy sector. However, due to the complex geological characteristics and fluid flow mechanisms of shale gas reservoirs, its exploitation faces numerous challenges. This study focuses on the optimization of intermittent production methods for shale gas wells in the Changning block. In this study, a dynamic coordination model of formation recharge and wellhead output was established using real-time pressure monitoring and historical production records as key inputs. Based on this, the dimensionless production efficiency index was optimized by finely regulating the switching timing of the wellhead, thus significantly enhancing the cumulative oil production of the well. The conclusions indicate that the optimization methods proposed in this study can effectively guide the production operations of shale gas wells in the Changning block, thereby enhancing production yield and stability. This research contributes practical value to the field by offering theoretical support and practical guidance for shale gas exploitation, addressing technical challenges in the process.

Switching Time Optimization for Binary Quantum Optimal Control

Quantum optimal control is a technique for controlling the evolution of a quantum system and has been applied to a wide range of problems in quantum physics. We study a binary quantum control optimization problem, where control decisions are binary-valued and the problem is solved in diverse quantum algorithms. In this paper, we utilize classical optimization and computing techniques to develop an algorithmic framework that sequentially optimizes the number of control switches and the duration of each control interval on a continuous time horizon. Specifically, we first solve the continuous relaxation of the binary control problem based on time discretization and then use a heuristic to obtain a controller sequence with a penalty on the number of switches. Then, we formulate a switching time optimization model and apply sequential least-squares programming with accelerated time-evolution simulation to solve the model. We demonstrate that our computational framework can obtain binary controls with high-quality performance and also reduce computational time via solving a family of quantum control instances in various quantum physics applications.

Material selection and performance analysis of RF-MEMS switch for MM-WAVE applications

This paper presents the design, simulation, and investigation of a fundamental structure for capacitive MEMS switches in a shunt configuration. The main objective is to select materials that achieve low actuation voltage while maintaining RF and dynamic performance, especially for mm-wave applications. The proposed design consists of a Fixed-Fixed flexure beam with dimensions of 260 μm in length, 100 μm in width, and 0.5 μm in thickness. Considering the impact of squeeze film, 60 holes are integrated into the beam membrane, each measuring 64 μm² (8µm x 8µm), and a final gap of 1.9 μm is implemented. The suitability of materials for the beam membrane and dielectric layer in capacitive MEMS switches has been thoroughly examined through a combination of theoretical analysis and software simulations. Aluminum (Al) has emerged as the ideal choice for the beam membrane in mm-wave applications. This preference is defensible by its simulated results to offer a low pull-in voltage of 4V, a quality factor of 1.18, and a switching time of 67 microseconds. Similarly, Si3N4 has been identified as appropriate material, offering a upstate capacitance of 91fF and a downstate capacitance of 7.1pF.

Wave transformation in transmission lines with rapid connection and disconnection of reactive elements

Rapid switching of transmission line parameters has emerged as a way to manipulate signals and as a testbed for various electromagnetic processes in time-varying media, including metamaterials. In general, the switching results in wave reflection and transmission similar to that for a spatial interface but at new frequencies. Here, various realizations of parameter switching are studied: connection and disconnection of reactive elements (capacitors and inductors) in series and in parallel. The temporal boundary conditions for the current and voltage distributions are derived rigorously based on the telegrapher’s equations that explicitly model additional elements, instead of taking the equivalent values. It is shown that the temporal boundary conditions depend not only on the parameter values before and after switching but on its specific realization. Connecting or disconnecting reactive elements always involves energy losses. When new elements are added, two types of losses are identified. The first type is related to the creation of static magnetic and electric fields in the elements after switching. The second type is related to a very rapid energy dissipation during switching even for a vanishingly small resistivity in the line. When elements are removed, their energy is also removed from the waves. The effects of finite switching times are discussed. This study defines some serious constraints in using switchable transmission lines for the realization of photonic time crystals and efficient wave manipulation without externally added energy. The results are also applicable to wave propagation phenomena in other media with time-varying parameters.

Rendezvous analysis and control design for multiple mobile agents with preserved network connectivity on hyperboloid

This paper studies the rendezvous problem for a second-order multi-agent system on the hyperboloid under a proximity-based communication topology. Using the Riemannian geometrical structure on the hyperboloid, we design a nonlinear feedback control law in which each agent has a limited sensing range. By analyzing the switching behavior of the communication topology, we show that the switching time of the resulting closed-loop system is finite, and the connectivity of the communication topology is preserved if the initial network is connected. In addition, we also provide an analysis of the asymptotic behavior of the second-order closed-loop system on the hyperboloid and prove that the proposed feedback control law enables all agents to converge to the same position.

Weight change with antiretroviral switch from integrase inhibitor or tenofovir alafenamide-based to Doravirine-Based regimens in people with HIV

Background Weight gain has been well-described with integrase strand transfer inhibitors (INSTIs) and tenofovir alafenamide (TAF). Doravirine (DOR) has been identified as a relatively “weight-neutral” drug; however, there is little data describing its effect on weight change in routine clinical practice. Methods We conducted a retrospective chart review of weight change among people with HIV changing from an INSTI- to a non-INSTI regimen with DOR. Results At the time of ART switch, among 49 people with HIV, the mean age was 47 years, 24% were female, and 75% had HIV-1 viral load <200 copies/mL. Most (55%) people with HIV were taking bictegravir/TAF/emtricitabine prior to the switch. Although 84% switched due to concerns about weight gain, only 16% had a weight gain of ≥10% in the year preceding, and 49% had no substantial change in weight. 86% switched to DOR/lamivudine/tenofovir disoproxil fumarate. A weight decrease (−2.6% [95% CI: −5.1, −0.1%, p = .041] was seen over the year following the ART switch. Weight change prior to switch was greatest in the year 2021 compared to 2019, 2020, and 2022. Conclusions Overall, modest changes in weight were seen following ART switch from INSTI-based regimen to a DOR-based, non-INSTI regimen. Further investigations with larger people with HIV cohorts will be helpful to guide clinical practice, while the impact of the COVID-19 pandemic on weight change should also be considered.

Hierarchical Sliding Mode Control Design for Stabilization of Underactuated Wheeled Acrobot System

This paper presents the hierarchical sliding mode control (HSMC)--based stabilization problem of the wheeled Acrobot (WAcrobot) system, which combines an actuated wheel that rolls in the horizontal plane with an Acrobot consisting of two inverted pendulum links. These links are driven by an actuator at the second joint and freely rotate in a vertical plane. The stabilization problem of the WAcrobot, previously addressed using switch-based controllers in many studies, is solved in this work by designing a single-stage controller without requiring switching steps or time. The design approach comprises two parts. First, the system is reduced to a cascaded nonlinear model in finite time using the inherent dynamic coupling relationship. Second, a two-loop control scheme is employed: the outer loop ensures that the actuated state variables track the desired response, while the inner loop forces them to exhibit an asymptotically stable nature. After the desired design of both loops, the asymptotic stability of the overall dynamics is achieved. Finally, the theoretical analysis is validated using MATLAB. Simulation results demonstrate that the proposed controller effectively stabilizes the WAcrobot system at the equilibrium points.

PROPERTIES OF SOLUTIONS IN THE DUBINS CAR CONTROL PROBLEM

TThis paper addresses the time-optimal control problem of the Dubins car, which is closely related to the problem of constructing the shortest curve with bounded curvature between two points in a plane. This connection allows researchers to apply both geometric methods and control theory techniques during their investigations. It is established that the time-optimal control for the Dubins car is a piecewise constant function with no more than two switchings. This characteristic enables the categorization of all such controls into several types, facilitating the examination of the solutions to the control problem for each type individually. The paper derives explicit formulas for determining the switching times of the control signal. In each case, necessary and sufficient conditions for the existence of solutions are obtained. For certain control types, the uniqueness of optimal solutions is established. Additionally, the dependence of the movement time on the initial and terminal conditions is studied.

A Novel Approach Using LuxSit-i Enhanced Toehold Switches for the Rapid Detection of Vibrio parahaemolyticus.

Vibrio parahaemolyticus (V. parahaemolyticus) is a significant concern, as it can cause severe infections and hemolytic trauma. Given its prevalence in seawater and coastal seafood, it poses a substantial risk as a foodborne pathogen. Biosensor-based detection technology has been continuously evolving, and toehold switches have emerged as a promising area within it, especially in the detection of RNA viruses. Here, we have developed a cell-free toehold switch sensor for V. parahaemolyticus detection. Traditional toehold switch detection methods usually use green fluorescent protein (GFP) or enzyme LacZ as the output signal, with an incubation time as long as 2 h, and are also mainly applied to the detection of RNA viruses. In this study, we introduced a novel, artificially designed luciferase (LuxSit-i) as an output signal and constructed toehold switches with two different output signals (sfGFP, LuxSit-i), aimed at reducing the incubation time of toehold switches. Moreover, to further improve the detection process, we separately utilize recombinase polymerase amplification (RPA) and nucleic acid sequence-based amplification (NASBA) to amplify dead and live bacterial suspensions for detection and attempt to distinguish between dead and live bacteria. This study provided a convenient, rapid, and accurate method for the on-site detection of V. parahaemolyticus, especially beneficial for resource-limited settings. By eliminating the requirement for specialized facilities and personnel, this system has the potential to be a valuable tool in improving public health responses, especially in developing regions.

CA1 ensembles expressing immediate-early genes are driven by context switch, shrink with sustained presence, and show no effect of change of task demands.

The hippocampus (HPC) is essential for navigation and memory, tracking environmental continuity and change, including navigation relative to moving targets. CA1 ensembles expressing immediate-early gene (IEG) Arc and Homer1a RNA are contextually specific. While IEG expression correlates with HPC-dependent task demands, the effects of behavioral demands on IEG-expressing ensembles remain unclear. In three experiments, we investigated the effects of context switch, sustained presence, and task demands on dorso-proximal CA1 IEG+ ensembles in rats. Experiment 1 showed that the size of IEG+ (Arc, Homer1a RNA) ensembles dropped to baseline during uninterrupted 30-minute exploration, reflecting familiarization, unless a context switch was present. Context-specificity of the ensembles depended on both environment identity and timing of the context switch. Experiment 2 found no effect of HPC-dependent mobile robot avoidance or HPC-independent avoidance of a stationary robot on IEG+ ensembles beyond mere exploration. Experiment 3 replicated these findings for c-Fos protein. The data suggest that IEG+ ensembles are driven by a context switch and shrink over time during sustained presence in the same environment. We found no evidence of task demands or their change affecting the size, stability over time, or task-specificity of IEG+ ensembles. These results shed light on the temporal dynamics of CA1 IEG+ ensembles, and their control by contextual and behavioral factors.

Effects of Phenoxazine Chromophore on Optical, Electrochemical and Electrochromic Behaviors of Carbazole-Thiophene Derivatives.

Phenoxazine, as an organic-small-molecule chromophore, has attracted much attention for its potential electrochromic applications recently. To develop appealing materials, phenoxazine chromophores were introduced at the N-position of carbazole-thiophene pigment, yielding two novel monomers (DTCP and DDCP), whose chemical structures were characterized by NMR, HRMS and FTIR. The results of the optical property study indicate that little influence could be observed in the presence of the phenoxazine chromophore. Corresponding polymer films on the surface of an ITO/glass electrode were obtained through electropolymerization. The electrochemical features displayed were various due to the introduction of the phenoxazine group. The spectroelectrochemical results demonstrate that the color of the polymer films could be changed. Compared with the PDDC films, the PDDCP films exhibited three different colors (tangerine, green and purple colors) in different redox states, which could be attributed to the synergistic effect between the carbazole-thiophene conjugate chain and the phenoxazine group. Moreover, fast switching time could be seen due to the presence of the phenoxazine chromophore. This study could provide a reference for obtaining high-performance electrochromic materials.

Pulse splitting technique for low sidelobe time-modulated antenna array synthesis with harmonic suppression

Abstract In this paper, pulse splitting approach is proposed to simultaneously reduce the sidelobe level (SLL) of fundamental signal and maximum sideband levels (SBLs) of harmonic signals for time-modulated linear array (TMLA). This is achieved by controlling only the periodic switching time sequence of each element of the TMLA. In pulse splitting, the on–off switching sequence of each radiating element is characterized by multiple rectangular sub-pulses within the modulation period which increase the degrees of freedom in order to better synthesize the desired fundamental pattern with simultaneous suppression of harmonic or sideband radiation. A genetic algorithm is employed to optimize the switch-on and switch-off instants of each sub-pulse for each element for 16-element uniform amplitude, phase, and space linear antenna array. The simulation results reveal that the proposed method can achieve the desired patterns with very low SLL and SBLs compared with previous published results.

Optimal Control of a Harmonic Oscillator with Parametric Excitation

This paper addresses the time-optimal control problem for a harmonic oscillator characterized by a time-dependent frequency. The primary objective is to determine the minimal time required to transition the system from an initial state, defined by a given position and velocity, to a specified final state, while ensuring that the frequency remains within prescribed bounds. The key challenge lies in identifying the optimal switching times between two available frequencies to meet all boundary conditions efficiently. By examining various boundary scenarios, constructing the reachable set of all admissible trajectories, and employing both analytical techniques and control theory, we develop a robust solution strategy. This work holds particular relevance for practical applications demanding rapid state transitions, such as mechanical vibration control and signal processing, where achieving time-optimal performance is critical. Furthermore, the methods presented are adaptable to a wide range of systems facing similar constraints, providing a versatile and effective framework for time-optimal control.

Transient Current Responses of Organic Electrochemical Transistors: Evaluating Ion Diffusion, Chemical Capacitance, and Series Elements

AbstractFor the successful implementation of organic electrochemical transistors in neuromorphic computing, bioelectronics, and real‐time sensing applications it is essential to understand the factors that influence device switching times. This work describes a physical‐electrochemical model of the transient response to a step of the gate voltage. The model incorporates 1) ion diffusion inside the channel that governs the electronic conductivity, 2) horizontal electron transport, and 3) the external elements (capacitance, ionic resistance) of the ion dynamics in the electrolyte. This work finds a general expression of two different time constants that determine the vertical insertion process in terms of the transport/polarization parameters, in addition to the electronic transit time. The work highlights the central role of the chemical capacitance in determining the modulation of the lateral conductivity. The different types of response of the drain current are classified, and the significance for synaptic operation in neuromorphic circuits is discussed. The model is confirmed by detailed simulations that enable to visualize the different ions distributions and dynamics.

Stimuli‐Responsive Smart Glass with Switchable Unidirectional Light Source for Enhanced Privacy/Indoor Illumination

AbstractLight manipulation is in high demand in science and industry. Smart glasses enable dynamic light control for indoor illumination, privacy protection, automobiles, and displays. However, existing technologies often limit single‐functionality (simultaneous bidirectional transparency or opacity) and strongly inherent user preferences. Here, a novel class of stimuli‐responsive smart glass featuring a switchable unidirectional light source using 2,2‐dimethoxy‐2‐phenylacetophenone (DMPAP)‐doped twisted hybrid polymer network liquid crystals (TH‐PNLCs) with a linear polarizer is developed. These DMPAP‐doped TH‐PNLCs exhibit a blue‐shift in spectra under cross‐polarizer, enhanced twist angle, and increased light amplitude compared with undoped devices. When subjected to external electric stimuli and edge light, the device emits light bi‐directionally with different polarizations. As a proof of concept, placing a transmissive polarizer in front of the homogeneous alignment layer (Surface A) enables light absorption and scattering toward vertical alignment (Surface B), ensuring privacy by blocking visibility from Surface A while keeping Surface B visible. Replacing the transmissive linear polarizer with a reflective one enhances light scattering, boosting intensity from Surface B, making the device ideal for energy‐efficient indoor lighting. Featuring fast switching times and robust endurance, this stimuli‐responsive smart glass offers a pioneering solution for green buildings and automobiles with enhanced privacy and indoor illumination.

Experimental Study on the Output Characteristics of a Novel Intensifier Controlled by an Electromagnetic Valve

The application of ultra-high-pressure (UHP) water jets for rock slotting in the bottom hole has been recognized as a highly effective approach to enhance rock-breaking efficiency. However, the current downhole intensifiers are confronted with various limitations, including the short duration of UHP pulse water jet output and challenges in attaining both controllable and adjustable output frequencies, consequently leading to compromised slotting efficiency. In this study, a novel intensifier controlled by an electromagnetic valve was designed, and a visual test platform was constructed to investigate the output pressure characteristics and their influencing factors. The output characteristics of the intensifier consist of a mixed pulse jet composed of high-pressure and low-pressure jets, resulting in a square wave-like output waveform with an adjustable frequency. The output pressure characteristics of the intensifier are primarily influenced by the input pressure and the switching time of the electromagnetic valve, assuming that the structural parameters are constant. Increasing the input pressure raises the peak pressure, thereby enhancing the slotting capability of the jet stream. Aligning the switching time of the electromagnetic valve with the rotation period of the drill bit improves the slotting efficiency. In the lab tests, the output pressure of the intensifier was successfully increased to 118.2 MPa, with a sustained duration of a high-pressure jet segment for 2.1 s. These research findings offer a new method for enhancing drilling efficiency in deep hard rock formations.

Power and sample size calculation for non-inferiority trials with treatment switching in intention-to-treat analysis comparing RMSTs.

Background: Difference in Restricted Mean Survival Time (DRMST) has attracted attention and is increasingly used in non-inferiority (NI) trials because of its superior power in detecting treatment effects compared to hazard ratio. However, when treatment switching (also known as crossover) occurs, the widely used intention-to-treat (ITT) analysis can underpower or overpower NI trials. Methods: We propose a simulation-based approach, named nifts, to calculate powers and determine the necessary sample size to achieve a desired power for non-inferiority trials that allow treatment switching, in ITT analysis using DRMST. Results: Real-world and simulated examples are used to illustrate the proposed method and examine how switching probability, switching time, the relative effectiveness of treatments, allocation ratio, and even time distribution influence powers and sample sizes. Our simulation study shows that switching time and switching probability decrease or increase powers and sample sizes compared to those in the scenarios without treatment switching. A shorter switching time and a higher switching probability amplify the magnitude of these changes. The direction of the change in powers and sample sizes depends on the relative effectiveness of the treatments. When m2/m1>1, power decreases and sample size increases, while m_2/m_1<1 leads to the opposite effect, where m1 and m2 are the median survivals in the control and experimental groups, respectively. Conclusions: This simulation-based approach offers a preview of how treatment switching can influence powers and sample sizes in NI trials, providing investigators with useful information before conducting the trials. nifts is freely available at https://github.com/cyhsuTN/nifts.

Enhanced performance of self-selective RRAM devices in V/TaOx/Pt structure

Abstract The performance of resistive random-access memory devices with vanadium as the top electrode and different TaOx insulating layer is investigated in this paper. The results indicate that the VO2 oxide layer generated by the oxidation of the vanadium electrode can serve as inherent selector, without the need for additional series selectors required in conventional methods. A large amount of oxygen vacancy migration was limited in the double insulating layers, enabling the device to achieve stable Self-Selective resistive random-access memory performance. This indicated that the advantage of the double insulation layers lay in manipulating the migration of oxygenions and vacancies. Endurance tests showed no degradation over 103 cycles, and the device maintained stability after 20,000 pulse applications. The subthreshold swing of the selector was less than 42 mV/dec, and the switching time was less than 2 μs. This research presents a promising advancement in resistive random-access memory technology with potential for high-density memory integration and reliable performance.&amp;#xD;

Fast and large refractive index switching of optically isotropic liquid crystal films

ABSTRACT Polymer Dispersed Liquid Crystals (PDLCs) consist of low molecular weight liquid crystal (LC) droplets embedded in a polymer matrix. Nano-PDLCs are a special type of PDLCs where the LC droplet sizes are in the nanometre range. For normal incidence of light, the nano-PDLC has a voltage dependent, isotropic refractive index that could be used to make polarisation independent tunable lenses. Here, we report the effect of chiral dopant on haze, switching time and field-induced variation of the refractive index δn E of PDLC materials having a high birefringence ( Δn = 0.38 at 550 nm ) nematic liquid crystal dispersed in a polymer matrix. As an effect of the chiral dopant, δn decreases slightly from 0.05 to 0.037 at E = 10 V / μm , however the relaxation time and the haze decrease to a much larger extent from 2.5 ms to 0.3 m s, and from 50% to less than 10% at 550 nm, respectively. These improvements are due to the sub-micrometer helical pitch in the LC droplets that reduces the size of the LC droplets well below 1 µm, leading to nano-PDLC with sub-millisecond switching time and low haze.