Search Results (626)

Modern deep neural network (DNN) accelerators must sustain high throughput while avoiding performance degradation from supply voltage (VDD) droop, which occurs when large arrays of multiply–accumulate (MAC) units switch concurrently and induce high peak current ($IC{C}_{max}$) transients on the power delivery network (PDN). In this work, we focus on ASIC-class DNN accelerators with tightly synchronized MAC arrays rather than FPGA-based implementations, where such cycle-aligned switching is most pronounced. Conventional guardbanding and reactive countermeasures (e.g., throttling, clock stretching, or emergency DVFS) either waste energy or incur non-trivial throughput penalties. We propose SparseDroop, a unified hardware-conscious framework that proactively shapes instantaneous current demand to mitigate droop without reducing sustained computing rate. SparseDroop comprises two complementary techniques. (1) SparseStagger, a lightweight hardware-friendly droop scheduler that exploits the inherent unstructured sparsity already present in the weights and activations—it does not introduce any additional sparsification. SparseStagger dynamically inspects the zero patterns mapped to each processing element (PE) column and staggers MAC start times within a column so that high-activity bursts are temporally interleaved. This fine-grain reordering smooths $ICC$ trajectories, lowers the probability and depth of transient VDD dips, and preserves cycle-level alignment at tile/row boundaries—thereby maintaining no throughput loss and negligible control overhead. (2) SparseBlock, an architecture-aware, block-wise-structured sparsity induction method that intentionally introduces additional sparsity aligned with the accelerator’s dataflow. By co-designing block layout with the dataflow, SparseBlock reduces the likelihood that all PEs in a column become simultaneously active, directly constraining $IC{C}_{max}$ and peak dynamic power on the PDN. Together, SparseStagger’s opportunistic staggering (from existing unstructured weight zeros) and SparseBlock’s structured, layout-aware sparsity induction (added to prevent peak-power excursions) deliver a scalable, low-overhead solution that improves voltage stability, energy efficiency, and robustness, integrates cleanly with the accelerator dataflow, and preserves model accuracy with modest retraining or fine-tuning. Full article

Power semiconductor devices are fundamental components in modern electronic power conversion. In applications demanding high power density and efficiency, the choice between silicon (Si) IGBTs and Silicon Carbide (SiC) MOSFETs is critical. SiC MOSFETs, owing to their high critical electric field, superior thermal conductivity, wide band gap, and low power loss, realize significant performance improvements and compact design. This work presents a comprehensive, simulation-driven comparative investigation under identical setups, evaluating both technologies across various parameters. The effects of temperature variations on gate-source threshold voltage drift, current slew rate, device stress, and energy dissipation during switching transitions are evaluated. Furthermore, the characteristic switching behavior when the DC-bus voltage, gate resistance, and load current are varied is investigated. This study addresses a current scarcity of systematic investigation by presenting a comprehensive comparative evaluation of switching losses and efficiency across varied operating conditions, providing validated conclusions for the design of advanced WBG converters. The results demonstrate that SiC exhibits lower losses and faster switching speeds than Si IGBTs, with minimal temperature-dependent loss variations, unlike Si devices, whose losses rise significantly with temperature. Si shows distinct tail currents during turn-off, absent in SiC devices. A conclusive comparative evaluation of switching energy losses under varied operating conditions demonstrates that SiC devices can effectively retrofit Si counterparts for fast, low-loss, high-efficiency applications. Full article

Two types of devices capable of switchable infrared spectral control are demonstrated by utilizing the phase-change characteristics of In₃SbTe₂ (Indium–Antimony–Tellurium, IST), which transitions from a low-loss dielectric amorphous phase to a high-loss metallic crystalline state. Through comprehensive structural design, theoretical calculation, simulation analysis, experimental measurement, and application demonstration, we realize distinct switching effects and functions of these two devices. In the first design, IST mono-layer thin films integrated with infrared-transparent substrates (KBr and ZnSe) enable switching between amorphous high transmittance and crystalline high reflectance states over the 2.5–15 μm range, suitable for infrared optical switches and stealth applications. In the second design, introducing a Si metasurface disk array atop the IST mono-layer thin film enables switching between broadband infrared transparency and narrowband high emissivity. This configuration allows independent spectral control of the infrared spectra within the non-atmospheric (5–8 μm) and atmospheric (8–14 μm) windows, providing a versatile platform for tunable thermal radiation management and adaptive infrared camouflage. Full article

As a multi-switching power electronic circuit with complex variable topology, the three-level active neutral point clamped (ANPC) converter is a complex system with strong coupling and low linearity. It has numerous high-speed switching devices, a large number of switch states, and a high matrix dimension. Modeling each switch will undoubtedly further increase the circuit size. While in real-time simulation, updating all states of the model to produce outputs within a single time step results in a significant computational load, causing an increasing consumption of FPGA hardware resources as the number of switches and circuit size grow. In order to solve this problem, the current common practice is to decompose the entire complex power electronic system into smaller serial subsystems for modeling. The overall modeling approach for small circuits can be achieved, but when the size of the circuit increases, the overall modeling complexity and difficulty are increased or even impossible to achieve. Decoupling power electronic circuits with this decomposition into subsystem modeling not only reduces the matrix dimension and simplifies the modeling process, but also improves the computational efficiency of the real-time simulator. However, this inevitably generates simulation delays between different subsystems, leading to numerical oscillations. In an effort to overcome this challenge, this paper adopts the method of parallel computation after subsystem partitioning. There is no one-beat delay between different subsystems, and there is no loss of accuracy, which can improve the numerical stability of the modeling and can effectively reduce the step length of real-time simulation and alleviate the problem of real-time simulation resource consumption. In addition, to address the problems of low accuracy due to the traditional forward Euler method as a solver and the possibility of significant errors at some moments, this paper uses a modified prediction correction method to solve the discrete mathematical model, which provides higher accuracy as well as higher stability. And, different from the traditional control method, this paper uses an improved FCS-MPC strategy to control the switching transients of the ANPC model, which achieves a very good control effect. Finally, a simulation step size of less than 60 ns is successfully realized by empirical demonstration on the Speedgoat test platform. Meanwhile, the accuracy of our model can be objectively evaluated by comparing it with the simulation results of the Matlab Simpower system. Full article

Aging plays a major role in the development of numerous chronic diseases, one of which is a marked decline in skeletal health. Beyond diminishing bone mass and strength, mammals of advanced age experience a decline in skeletal mechanotransduction—that is, the ability of the skeleton to respond adaptively to mechanical perturbation. One possibility for the loss of mechanotransduction in bone with aging is an age-associated increase in the population density of senescent cells—those cells that have undergone irreversible cell cycle arrest, resistance to apoptosis, and production of a modified secretome (the SASP) that has damaging effects to nearby healthy (non-senescent) cells. We investigated whether the presence of senescent cells might drive some of the diminished mechanical response observed in aged bone, by testing the hypothesis that the clearance of senescent cells via intermittent senolytic treatment promotes mechanical responsiveness in an aged skeleton. C57BL/6 mice aged 6 months and 22 months were treated weekly with the senolytic cocktail Dasatinib and Quercetin (D + Q) for 1 month, then subjected to low level in vivo mechanical loading of the ulna for 1 week. The 6-month-old mice exhibited a doubling of load-induced ulnar periosteal bone formation when treated with D + Q, compared to vehicle-treated mice, but the periosteal response to loading was not significantly altered by D + Q in the aged (22-month) mice. We further probed the efficacy of D + Q in mechanotransduction by switching to an endocortical model—the axial tibia loading system. Here, the 22-month-old mice had nearly double the load-induced endocortical bone formation compared to vehicle-treated mice. We further assayed the cortical bone gene expression profile in loaded and control tibias from treatment-naïve 6-month and 22-month mice, to determine whether there is significant overlap between mechanically induced signaling genes and SASP genes. We found significant load-induced changes among several SASP genes, suggesting that inhibition of the SASP (i.e., senomorphics) might interfere with mechanical signaling from otherwise healthy cells. In summary, clearance of senescent cells via intermittent D + Q treatment is effective at improving endocortical mechanical responsiveness in the aged skeleton, which is commonly diminished throughout the course of aging. Full article

The rapid growth of Internet of Things (IoT) deployments has created an urgent need for energy-efficient communication strategies that can adapt to dynamic operational conditions. This study presents a novel adaptive protocol selection framework that dynamically optimizes IoT communication energy consumption through context-aware decision making, achieving up to 34% energy reduction compared to static protocol selection. The framework is grounded in a comprehensive empirical evaluation of three widely used IoT communication protocols—MQTT, CoAP, and HTTP—using Intel’s Running Average Power Limit (RAPL) for precise energy measurement across varied network conditions including packet loss (0–20%) and latency variations (1–200 ms). Our key contribution is the design and validation of an adaptive selection mechanism that employs multi-criteria decision making with hysteresis control to prevent oscillation, dynamically switching between protocols based on six runtime metrics: message frequency, payload size, network conditions, packet loss rate, available energy budget, and QoS requirements. Results show MQTT consumes only 40% of HTTP’s energy per byte at high volumes (>10,000 messages), while HTTP remains practical for low-volume traffic (<10 msg/min). A novel finding reveals receiver nodes consistently consume 15–20% more energy than senders, requiring new design considerations for IoT gateways. The framework demonstrates robust performance across simulated real-world conditions, maintaining 92% of optimal performance while requiring 85% less computation than machine learning approaches. These findings offer actionable guidance for IoT architects and developers, positioning this work as a practical solution for energy-aware IoT communication in production environments. Full article

A novel reduced-component multilevel inverter (MLI) topology is presented to overcome the limitations of conventional multilevel inverters, such as high switching losses, complex modulation, and excessive semiconductor usage. The proposed triple-source cross-connected configuration minimizes conduction paths and reduces voltage stress across switching devices to approximately 45% of the total DC-link voltage. A hybrid carrier-less pulse-width modulation (PWM) strategy, derived from the equal-area criterion, was developed to generate switching pulses without the need for carriers or reference signals. Analytical and experimental analyses demonstrated a significant improvement in power quality, achieving a total harmonic distortion (THD) of 4.3%, compared with 8.2% in conventional PWM schemes, while enhancing the conversion efficiency from 91.5% to 95.2%. Simulation and hardware validation in a nine-level prototype confirmed the superior efficiency, low harmonic distortion, and compactness of the proposed inverter, making it well-suited for renewable energy integration, electric vehicles, and medium-power industrial systems. Full article

This paper presents a reconfigurable switching circuit and control methodology for mitigating power losses in photovoltaic (PV) systems under partial shading. The proposed hardware uses a simplified network of power MOSFETs and diodes to enable dynamic reconfiguration between series and parallel connections, improving energy yield with minimal conduction losses. Unlike conventional approaches that require irradiance measurements or extensive sensing, the control algorithm uses only per-module voltage and a single-current measurement to detect shading events in real time. A novel switching strategy reduces the number of actively controlled transistors, simplifying the control circuitry and reducing power dissipation. Both simulation and experimental results validate the method. Simulations of a 4-module PV system showed maximum power point (MPP) increases from 900 W to over 1100 W and from 460 W to 900 W, with full recovery to 1500 W after shading removal. Experimental verification on a 3-module setup under controlled shading yielded similar improvements: MPP increased from 38.4 W to 45.6 W and from 38.4 W to 45.8 W. These results demonstrate rapid adaptability, effective mismatch loss reduction, and maximisation of available power, making the proposed design a practical and low-overhead solution for commercial PV systems with non-uniform irradiance. Full article

This paper presents a novel hybrid modulation technique for Asymmetrical Cascaded H-Bridge Multilevel Inverters (ACHBMLIs), specifically designed to enhance both efficiency and harmonic performance. Unlike conventional strategies, the proposed method optimizes the switching scheme by operating the high-voltage H-Bridge at the fundamental frequency, thereby significantly reducing switching losses while maintaining low harmonic distortion levels comparable to traditional Pulse Width Modulation (PWM). To assess the effectiveness of the approach, a comprehensive comparison was conducted against two widely adopted modulation techniques for ACHBMLIs: Multicarrier Pulse Width Modulation (MPWM) and the Staircase Modulation Strategy (SMS). The evaluation involved both simulation and real-time Hardware-in-the-Loop (HIL) testing of a 7-level three-phase ACHBMLI, with a focus on key performance indicators such as voltage and current harmonic distortion, as well as converter efficiency. The results demonstrate that the proposed hybrid modulation achieves higher efficiency than PWM and lower current Total Harmonic Distortion (THD) than SMS. These findings highlight the potential of the hybrid strategy as a compelling solution for applications that demand an optimal balance between energy efficiency and waveform quality. Full article

This paper provides a comprehensive review of recent advancements in radio-frequency (RF) multifunctional components with integrated filtering characteristics, including tunable filtering attenuators, filtering power dividers, filtering couplers, and filtering Butler matrices, all of which play critical roles in wireless communication systems. With the increasing demand for miniaturization, integration, and low-loss performance in RF front-ends, multifunctional components with filtering characteristics have become essential. This review first introduces tunable attenuators and filtering attenuators based on various technologies such as PIN diodes, graphene-based structures, and RF-MEMS switches, and also analyzes their advantages, limitations, and performance. Then, we discuss filtering power dividers developed from Wilkinson structures, three-line coupled structures, resonator-based coupling matrix methods, and SSPP-waveguide hybrids. Furthermore, filtering couplers and filtering Butler matrices are reviewed, highlighting their capability to simultaneously achieve amplitude and phase control, making them suitable for multi-beam antenna feeding networks. Finally, a brief conclusion is summarized. Future research directions, such as hybrid technologies, novel materials, broadband and multi-band designs, and antenna-matrix co-design, are suggested to further enhance the performance and practicality of multifunctional RF components for next-generation wireless communication systems. Full article

Temperature excursions during refrigerated transport strongly affect the quality and shelf life of perishable food, yet reproducing realistic, time-varying cold-chain temperature histories in the laboratory remains challenging. In this study, we present a compact, portable climate chamber driven by Peltier modules and an identification-guided control architecture designed to reproduce real refrigerated-truck temperature histories with high fidelity. Control is implemented as a cascaded regulator: an outer two-degree-of-freedom PID for air-temperature tracking and faster inner PID loops for module-face regulation, enhanced with derivative filtering, anti-windup back-calculation, a Smith predictor, and hysteresis-based bumpless switching to manage dead time and polarity reversals. The system integrates distributed temperature and humidity sensors to provide real-time feedback for precise thermal control, enabling accurate reproduction of cold-chain conditions. Validation comprised two independent 36-day reproductions of field traces and a focused 24-h comparison against traditional control baselines. Over the long trials, the chamber achieved very low long-run errors ($\mathrm{MAE}\cong 0.19 °\mathrm{C}$, $\mathrm{MedAE}\cong 0.10 °\mathrm{C}$, $\mathrm{RMSE}\cong 0.33 °\mathrm{C}$, $R^2=0.9985$). The 24-h test demonstrated that our optimized controller tracked the reference, improving both transient and steady-state behaviour. The system tolerated realistic humidity transients without loss of closed-loop performance. This portable platform functions as a reproducible physical twin for cold-chain experiments and a reliable data source for training predictive shelf-life and digital-twin models to reduce food waste. Full article

Power electronics is an important feature of the new power system. The high-speed development of the new power system has gradually increased the requirements for high-efficiency and high-reliability high-voltage transmission and substation equipment. Silicon carbide (SiC) devices, which have the advantages of fast switching speed, low power loss, and high-temperature resistance, are the key core technology for the upgrading of high-voltage transmission and substation equipment. The paper begins by examining the evolution of the demand for high efficiency, compact and reliable power electronic devices for high-voltage transmission and substation systems at different stages of energy development. SiC has emerged as a key technological path to break through the physical limits of silicon-based devices, due to its outstanding material properties. Silicon-based devices encounter significant bottlenecks in high-voltage and high-frequency applications, with high switching losses and a junction temperature tolerance that is typically limited to 150 °C. In contrast, SiC devices can reduce switching losses by 60–80% and operate stably at temperatures up to 200 °C or even higher, thereby significantly enhancing system efficiency and power density. Finally, the paper provides a systematic analysis of the application of SiC devices in high-voltage transmission and substation equipment, exploring and identifying the technical bottlenecks and future research directions for SiC-based high-voltage transmission equipment. Full article

Atherosclerotic cardiovascular disease treatment is being reevaluated, since a residual cardiovascular risk (RCR) persists even in patients who achieve optimal LDL-C values. Underlying causes are metabolic dysfunction, lipoprotein(a), inflammation, and triglyceride-rich lipoproteins and their remnants. Dietary treatment options like time-restricted eating (TRE) are becoming more widely acknowledged for their potential advantages in metabolic health and weight control, as a treatment of atherosclerosis expanding beyond LDL-C medication. Beyond weight loss, TRE (which restricts meals to a window of 6 to 8 h) appears as the most accessible treatment, and has been shown to improve blood pressure, lipid profiles, and glucose regulation through mechanisms like metabolic switching and circadian synchronization. We hypothesize, and will present our arguments, that a key mechanism underlying the cardiovascular and weight-related benefits of TRE is its impact on the circadian regulation of angiopoietin-like protein 4 (ANGPTL4) activity within adipose tissue. Additionally, lipolysis is accelerated by ANGPTL4 activation. TRE, via its actions on ANGPTL4, therefore not only inhibits adipose fatty acid uptake but stimulates their release as well. Additionally, TRE may increase intravascular very low-density lipoprotein (VLDL) catabolism by muscle due to the reduced exposure of lipoprotein lipase (LPL) to competing chylomicrons, known to slow the rate of VLDL catabolism. During the prolonged fasting, VLDL residence time is thus shortened, limiting the exposure to endothelium and hepatic lipases and thus reducing the amount of atherogenic remnant particles. Larger, longer-term randomized controlled studies in a variety of groups are required to further clarify TRE’s function in RCR prevention and therapy. As knowledge of triglyceride lipoprotein (TRL) metabolism expands, a comprehensive strategy for the management of RCR emerges, and a broader spectrum of LPL regulator-based therapeutics is created. Consequently, it is advisable to prioritize further research into the influence of TRE on LPL modulation via ANGPTL4 and ANGPTL8, which provides a natural, accessible, and low-cost alternative. Full article

Wavefront aberrations caused by thermal flows or arising from the quality of optical components can significantly impair wireless communication links. Such aberrations may result in an increased error rate in the received signal, leading to data loss in laser communication applications. In this study, we explored a newly developed combined stochastic gradient descent optimization algorithm aimed at compensating for optical distortions. The algorithm we developed exhibits linear time and space complexity and demonstrates low sensitivity to variations in input parameters. Furthermore, its implementation is relatively straightforward and does not necessitate an in-depth understanding of the underlying system, in contrast to the Stochastic Parallel Gradient Descent (SPGD) method. In addition, a developed switch-mode approach allows us to use a stochastic component of the algorithm as a rapid, rough-tuning mechanism, while the gradient descent component is used as a slower, more precise fine-tuning method. This dual-mode operation proves particularly advantageous in scenarios where there are no rapid dynamic wavefront distortions. The results demonstrated that the proposed algorithm significantly enhanced the total collected power of the beam passing through the 10 μm diaphragm that simulated a 10 μm fiber core, increasing it from 0.33 mW to 2.3 mW. Furthermore, the residual root mean square (RMS) aberration was reduced from 0.63 μm to 0.12 μm, which suggests a potential improvement in coupling efficiency from 0.1 to 0.6. Full article

As a core functional device in microwave systems, attenuators play a crucial role in key aspects such as signal power regulation, amplitude attenuation, and impedance matching. Addressing the pressing technical issues currently exposed by attenuators in practical applications, such as excessive insertion loss, low attenuation accuracy, large physical dimensions, and insufficient process reliability, this paper proposes a design scheme for an RF three-bit reconfigurable stepped attenuator based on radio frequency micro-electromechanical systems (RF MEMS) switches. The attenuator employs planar integration of the T-type attenuation network, Coplanar Waveguide (CPW), Y-shaped power divider, and RF MEMS switches. While ensuring rational power distribution and stable attenuation performance over the full bandwidth, it reduces the number of switches to suppress parasitic parameters, thereby enhancing process feasibility. Test results confirm that this device demonstrates significant advancements in attenuation accuracy, achieving a precision of 1.18 dB across the 0–25 dB operational range from DC to 20 GHz, with insertion loss kept below 1.65 dB and return loss exceeding 12.15 dB. Additionally, the device boasts a compact size of merely 0.66 mm × 1.38 mm × 0.32 mm, significantly smaller than analogous products documented in existing literature. Meanwhile, its service life approaches 5 × 10⁷ cycles. Together, these two attributes validate the device’s performance reliability and miniaturization advantages. Full article