Search Results (770)

Photovoltaic/Thermal (PV/T) technology efficiently harnesses solar energy by co-generating electricity and hot water. Unlike conventional PV systems, PV/T systems improve thermal utilization, cool PV modules, and prevent performance degradation caused by high temperatures. Among the various PV/T configurations, micro-channel heat pipe (MCHP) systems are prominent due to their ability to enhance heat transfer through the use of vacuum-filled, refrigerant-sealed MCHPs. This study explores how factors such as working fluid type, evaporation section heat flux, fill ratio, and condensation section length impact system performance. A 3D steady-state CFD model simulating phase-change heat transfer was developed to analyze thermal and electrical efficiencies. The results reveal that R134a outperforms acetone in heat transfer, with thermal resistance showing a significant decrease (from 0.5 °C·W⁻¹ at a 30% fill rate to 0.3 °C·W⁻¹ at a 70% fill rate) under varying heat source powers. The optimal fill ratio depends on the heat flux; for powers up to 70 W, the fill ratio ranges from 30% to 50%, while above 70 W, it shifts to 60–80%. Additionally, a longer condensation section reduces thermal resistance by up to 30% and enhances heat transfer efficiency, improving the overall system performance by 10%. These findings offer valuable insights into optimizing MCHP PV/T systems for increased efficiency. Full article

Post-traumatic stress disorder (PTSD) is frequently comorbid with persistent depressive disorder (dysthymia), indicating shared neurobiological pathways that influence stress modulation, emotional regulation, and neurohormonal adaptation. This study examines the roles of serum biomarkers—small ubiquitin-like modifier 1 (SUMO1), malondialdehyde (MDA), fractalkine (CX3CL1), and ubiquitin C-terminal hydrolase L1 (UCHL1)—involved in oxidative stress management, neuroimmune regulation, and neuronal proteostasis. In this cross-sectional analysis, biomarker expression was assessed in 92 male trauma-exposed participants aged 19–50 years, divided into three groups: PTSD duration ≤ 5 years (n = 33, median age 34.0 years [IQR 31.0–41.0]), PTSD duration > 5 years (n = 31, median age 36.0 years [IQR 29.5–41.0]), and controls without current or past PTSD (n = 28, median age 33.5 years [IQR 24.3–41.5]). Participants were stratified into younger (19–34 years) and older (35–50 years) cohorts to account for age-related neurobiological variability. Dysthymic symptomatology was evaluated using the Cornell Dysthymia Rating Scale (CDRS), focusing on chronic subthreshold depressive features. Results indicated a significant association between PTSD and elevated dysthymic symptom burden (p < 0.001), with both PTSD subgroups demonstrating mild to moderate CDRS severity compared to euthymic controls. Biomarker analysis revealed phase-dependent alterations: SUMO1 levels were significantly elevated in the ≤5 years PTSD group compared to controls (p = 0.002), suggesting early compensatory neuroprotection, whereas UCHL1 was markedly increased in the >5 years PTSD group (p = 0.015), which is indicative of chronic neuronal damage and proteostatic disruption. No significant differences were observed in MDA or CX3CL1 across groups (p > 0.05). These findings highlight PTSD’s contribution to sustained affective dysregulation, potentially mediated by temporal shifts in oxidative stress and protein homeostasis markers. Clinically, this supports the utility of biomarker profiling for risk stratification, early intervention, and personalized therapeutic strategies, such as targeted modulation of SUMOylation or UCHL1 activity, to enhance neuroresilience and mitigate progression to severe mood disorders. Full article

Membrane distillation crystallization (MDCr) is an approach for treating hypersaline wastewaters and enabling zero-liquid-discharge (ZLD) systems. However, its performance is often inhibited by concentration polarization, scaling, and membrane wetting. Heterogeneous seeding has been proposed to shift crystallization into the bulk phase, yet its quantitative influence on flux stability, wetting resistance, and crystal growth remains poorly understood. This study investigates air-gap MDCr (AGMDCr) of 300 g L⁻¹ NaCl using polypropylene (PP) and polytetrafluoroethylene (PTFE) membranes under seeded and unseeded conditions. Introducing 0.1 g L⁻¹ SiO₂ seeds (30–60 µm) enhanced steady-state permeate flux by 41% and maintained salt rejection ≥ 99.99%, indicating effective suppression of wetting. Seeding shifted the crystal size distribution from fine (mean 50.6 µm, unseeded) to coarse (230–340 µm), consistent with reduced primary nucleation and preferential growth on seed surfaces. At 0.6 g L⁻¹, the flux decreased relative to 0.1–0.3 g L⁻¹, consistent with near-wall solids holdup and hindered transport at high seeding concentration. The PTFE membrane exhibited a 47% higher flux than PP, primarily due to its reduced thermal resistance and optimized module geometry at the same flow rate. These results demonstrate that appropriately sized and dosed SiO₂ seeding effectively stabilizes flux and suppresses wetting in MDCr. Full article

We present a novel formulation of the Rayleigh–Plesset equation to describe stable gas bubble dynamics in viscoelastic media, using bubble volume variation, rather than radius, as the primary variable of the resulting nonlinear ordinary differential equation. This formulation incorporates the linear Kelvin–Voigt model as the constitutive relation for the surrounding fluid, capturing both viscous and elastic contributions, to track the oscillations of a gas bubble subjected to an ultrasonic field over time. The proposed model is solved numerically, subjected to a convergence analysis, and validated by comparisons with theoretical and experimental results from the literature. We systematically investigate the nonlinear oscillations of a single spherical gas bubble in various viscoelastic environments, each modeled with varying levels of rheological complexity. The influence of medium properties, specifically shear elasticity and viscosity, is examined in detail across both linear and nonlinear regimes. This work improves our understanding of stable cavitation dynamics by emphasizing key differences from Newtonian fluid behavior, resonance frequency, phase shifts, and oscillation damping. Elasticity has a pronounced effect in low-viscosity media, whereas viscosity emerges as the dominant factor modulating the amplitude of oscillations in both the linear and nonlinear regimes. The model equation developed here provides a robust tool for analyzing how viscoelastic properties affect bubble dynamics, contributing to improved the prediction and control of stable cavitation phenomena in complex media. Full article

Against the backdrop of global climate change intensifying seasonal freeze–thaw cycles, deteriorating soil conditions in farmland within seasonal frost zones constrain agricultural sustainability. This study employed an in situ field experiment during seasonal freeze–thaw periods in the black soil zone of Northeast China to investigate the joint regulatory effects of seasonal freeze–thaw processes and tillage practices on multidimensional features of soil bacterial communities. Key results demonstrate that soil bacterial communities possess self-reorganization capacity. α-diversity exhibited cyclical fluctuations: an initial decline followed by a rebound, ultimately approaching pre-freeze–thaw levels. Significant compositional shifts occurred throughout this process, with the frozen period (FP) representing the phase of maximal differentiation. Actinomycetota and Acidobacteriota consistently dominated as the predominant phyla, collectively accounting for 33.4–49% of relative abundance. Bacterial co-occurrence networks underwent dynamic topological restructuring in response to freeze–thaw stress. Period-specific response patterns supported sustained soil ecological functionality. Furthermore, NCM and NST analyses revealed that stochastic processes dominated community assembly during freeze–thaw (NCM R² > 0.75). Tillage practices modulated this stochastic–deterministic balance: no-tillage with straw mulching (NTS) shifted toward determinism (NST = 0.608 ± 0.224) during the thawed period (TP). Across the seasonal freeze–thaw process, soil temperature emerged as the primary driver of temporal community variations, while soil water content governed treatment-specific differences. This work provides a theoretical framework for exploring agricultural soil ecological evolution in seasonal frost zones. Full article

Capacitor voltage imbalance among submodules in energy storage modular multilevel converters (MMCs) can lead to current distortion, power oscillations, and even system instability. Traditional voltage control strategies, inherited from non-storage MMCs, offer limited regulation capabilities and are insufficient to address the complex balancing requirements across phases, arms, and submodules in distributed Energy-Storage MMCs (ES-MMC). This paper proposes a self-synchronized common-mode current strategy to achieve capacitor voltage rebalancing in Carrier Phase-Shifted PWM (CPS-PWM) modulated ES-MMCs. The proposed method establishes both phase-level and arm-level power rebalancing pathways by utilizing the common-mode current in the upper and lower arms. Specifically, the DC component of the common-mode current is employed to regulate common-mode power between the arms, while the fundamental-frequency component, through its interaction with the fundamental modulation voltage, is used to adjust differential-mode power. By coordinating these two power components within each phase, the method enables effective capacitor voltage rebalancing among submodules in the presence of power imbalance caused by a nonuniform distributed energy storage converter. A comprehensive analysis of differential- and common-mode voltage regulation under CPS-PWM is presented. The corresponding control algorithm is developed to inject adaptive common-mode voltage based on capacitor voltage deviations, thereby inducing self-synchronized balancing currents. Simulation and experimental results verify that the proposed strategy significantly improves power distribution uniformity and reduces capacitor voltage deviations under various load and disturbance conditions. Full article

Background/Objectives: This study investigated how phase-specific dietary strategies and weight regulation influence gut microbiota composition and diversity in competitive weightlifters. Particular emphasis was placed on integrating energy intake, macronutrient clustering, and weight fluctuations across distinct training phases. Methods: Thirteen competitive weightlifters were recruited, with 10–12 contributing complete data per phase. Fecal and dietary samples were collected during the preparation, competition, and transition phases. Gut microbiota was profiled via 16S rRNA gene sequencing, and alpha/beta diversity was analyzed using QIIME2. K-means clustering based on caloric/macronutrient intake identified dietary patterns. Taxonomic differences were assessed using DESeq2, and microbial structures were compared across training phases, weight classes, and weight-change categories. Results: Overall phylum- and genus-level profiles and diversity indices remained stable across training phases, indicating community-level resilience. However, specific genera varied with dietary and physiological factors. Enterococcus was higher during the preparation phase, whereas Lactobacillus was enriched during the competition and transition phases as well as in the high-calorie cluster. Lightweight and heavyweight athletes also showed distinct microbial structures, and pre- and post-competition weight changes were associated with shifts in selected taxa. Notably, the low-calorie group exhibited higher Shannon diversity than the high-calorie group (p = 0.0058), with Lactobacillus dominance contributing to reduced evenness in high-energy diets. Conclusions: Despite overall microbial stability, dietary energy availability and body-weight regulation modulated specific taxa relevant to performance and recovery. By integrating dietary clustering, weight-class comparison, and pre- and post-competition weight changes, this study provides novel insight into the microbiota of resistance-trained athletes, a population underrepresented in previous research. Despite the modest sample size and single-season scope, this study offers new evidence linking dietary strategies, weight regulation, and gut microbiota in weightlifters, and highlights the need for validation in broader cohorts. Full article

This paper presents a modified Orthogonal Frequency Division Multiplexing (OFDM) system that combines Discrete Wavelet Transform (DWT) with Discrete Sine Transform (DST) to enhance data rate capacity over traditional Discrete Fourier Transform (DFT)-based OFDM systems. By applying Inverse Discrete Wavelet Transform (IDWT) to the modulated Binary Phase Shift Keying (BPSK) bits, the constellation diagram reveals that half of the time-domain samples after single-level Haar IDWT are zeros, while the other half are real. The proposed system utilizes these $0.5N$ zero values, modulating them with the DST (IDST) and assigning them as the imaginary part of the signal. Performance comparisons demonstrate that the Bit-Error-Rate (BER) of this hybrid DWT-DST configuration lies between that of BPSK and Quadrature Phase Shift Keying (QPSK) in a DWT-based system, while also achieving data rate improvement of $0.5N$. Additionally, simulation results indicate that the proposed approach demonstrates stable performance even in the presence of estimation errors, with less than 3.4% BER degradation for moderate errors, and consistently better robustness than QPSK-based systems while offering improved data rate efficiency over BPSK. This novel configuration highlights the potential for more efficient and reliable data transmission in OFDM systems, making it a promising alternative to conventional DWT or DFT-based methods. Full article

The dead-time effect seriously affects the soft-switching performance and operating efficiency of the dual-active-bridge converter, and also causes problems such as reduced duty cycle, distortion of voltage and current waveforms, and narrowed transmission power range. The proposal of the five-degree-of-freedom modulation strategy transforms the working voltage waveforms of the primary and secondary sides as well as the inductor current waveform of the DAB converter from symmetric to asymmetric, while the dead-time issue still persists. Based on the five-degree-of-freedom modulation strategy, this paper analyzes the electrical characteristics of the converter before and after the introduction of dead time, designs switch drive pulses to avoid the dead time, and proposes a dead-time compensation modulation strategy based on five-degree-of-freedom phase shift. The results show that the proposed dead-time compensation control strategy can avoid problems such as voltage and current waveform distortion and reduction in the soft-switching power range caused by dead time, realizing dead-time compensation in the full power range. Experimental measurements show that, for different voltage transmission ratios, the maximum efficiency improvement is approximately 3.8–4% and the current stress is reduced by 2.11% to 3.13% under low-power operating conditions. The maximum efficiency improvement is approximately about 1.4–2.8% and the current stress is reduced by 1.84% to 2.53% under high-power operating conditions. Full article

The integration of a pixelated Fabry–Pérot filter array onto the image sensor enables on-chip snapshot multispectral imaging, significantly reducing the size and weight of conventional spectral imaging equipment. However, a traditional Fabry–Pérot cavity, based on metallic or dielectric layers, exhibits a narrow bandwidth, which restricts their utility in broader applications. In this work, we propose novel Fabry–Pérot filter structures that employ dielectric thin films for phase modulation, enabling single-peak filtering across a broad operational wavelength range from 400 nm to 1100 nm. The proposed structures are easy to fabricate and compatible with complementary metal-oxide-semiconductor (CMOS) image sensors. Moreover, the structures show low sensitivity to oblique incident angles of up to 30° with minimal wavelength shifts. This advanced Fabry–Pérot filter design provides a promising pathway for expanding the operational wavelength of snapshot spectral imaging systems, thereby potentially extending their application across numerous related fields. Full article

To address the issue of insufficient contrast in conventional X-ray absorption imaging for biological soft tissues and weakly absorbing materials, this paper proposes a beam tracking X-ray phase-contrast imaging system using a conventional X-ray source. A periodic pinhole array mask is placed between the X-ray source and the sample to spatially modulate the X-ray beam, dividing it into multiple independent sub-beams. Each sub-beam is deflected due to the modulation effect of the sample, resulting in slight positional shifts in the intensity patterns formed on the detector. The experiments employ an X-ray source with a 400 μm focal spot and use a two-dimensional step-scanning approach to acquire image sequences of various samples. The experimental results show that this method can extract the edge profile and structural changes in the samples to some extent, and it demonstrates good contrast and detail recovery under weak absorption conditions. These results suggest that this method has certain application potential in material inspection, non-destructive testing, and related fields. Full article

Background/Objectives: Decision-making under socially evaluative stress engages a dynamic interplay between cognitive control, emotional appraisal, and motivational systems. Contemporary models of multi-level co-regulation posit that these systems operate in reciprocal modulation, redistributing processing resources to prioritise either rapid socio-emotional alignment or deliberate evaluation depending on situational demands. Methods: Adopting a neurofunctional approach, a novel dual-task protocol combining the MetaCognition–Stress Convergence Paradigm (MSCP) and the Social Stress Test Neuro-Evaluation (SST-NeuroEval), a simulated social–evaluative speech task calibrated across progressive emotional intensities, was implemented. Twenty professionals from an HR consultancy firm participated in the study, with concurrent recording of frontal-temporoparietal electroencephalography (EEG) and bespoke psychometric indices: the MetaStress-Insight Index and the TimeSense Scale. Results: Findings revealed that decision contexts with higher socio-emotional salience elicited faster, emotionally guided choices (mean RT difference emotional vs. cognitive: −220 ms, p = 0.026), accompanied by oscillatory signatures (frontal delta: F(1,19) = 13.30, p = 0.002; gamma: F(3,57) = 14.93, p ≤ 0.001) consistent with intensified socio-emotional integration and contextual reconstruction. Under evaluative stress, oscillatory activity shifted across phases, reflecting the transition from anticipatory regulation to reactive engagement, in line with models of phase-dependent stress adaptation. Across paradigms, convergences emerged between decision orientation, subjective stress, and oscillatory patterns, supporting the view that cognitive–emotional regulation operates as a coordinated, multi-level system. Conclusions: These results underscore the importance of integrating behavioural, experiential, and neural indices to characterise how individuals adaptively regulate decision-making under socially evaluative stress and highlight the potential of dual-paradigm designs for advancing theory and application in cognitive–affective neuroscience. Full article

This study presents a comparative analysis of efficiency and harmonic generation in Triple Active Bridge (TAB) converters under two operating configurations: Case I, with one input source and two loads, and Case II, with two input sources and one load. Two modulation strategies, Single-Phase Shift (SPS) and Dual-Phase Shift (DPS), are evaluated through frequency-domain modeling and simulations performed in MATLAB/Simulink. The analysis is complemented by experimental validation on a laboratory prototype. The results show that DPS reduces harmonic amplitudes, decreases conduction losses, and improves output waveform quality, leading to higher efficiency compared to SPS. Harmonic current spectra and total harmonic distortion (THD) are analyzed to quantify the impact of each modulation method. The findings highlight that DPS is more suitable for applications requiring stable power transfer and improved efficiency, such as renewable energy systems, electric vehicles, and multi-source DC microgrids. Full article

This research explores a phase-shift-based discontinuous PWM method used for 24 V battery-powered onboard micro inverters, which are critical for thermally limited applications like micromachines, where efficient heat dissipation and compact size are paramount. Discontinuous pulse width modulation (DPWM) reduces switching losses by clamping the phase voltage to the DC bus in order to improve inverter efficiency. Due to the change in power factor at different operating points from motors or the inductor load, the use of only one DPWM method cannot achieve the optimal efficiency of a three-phase voltage source inverter (3ph-VSI). This paper proposes a generalized DPWM method with a continuously adjustable phase shift angle, which extends the six traditional DPWM methods to any type. According to different power factors, the proposed DPWM method is divided into five power factor angle intervals, namely [−90°, −60°], [−60°, −30°], [−30°, 30°], [30°, 60°], and [60°, 90°], and automatically adjusts the phase shift angle to the optimal-efficiency DPWM mode. The power factor is calculated by means of the Synchronous Reference Frame Phase-Locked Loop (SRF-PLL) method. The switching losses and harmonic characteristics of the proposed DPWM are analyzed, and finally, a 24 V onboard 3ph-VSI experimental platform is built. The experimental results show that the efficiency of DPWM methods can be improved by 3–6% and the switching loss can be reduced by 40–50% under different power factors. At the same time, the dynamic performance of the proposed algorithm with a transition state is verified. This method is particularly suitable for miniaturized inverters where efficiency and thermal management are critical. Full article

For power electronic transformer (PET) based Modular Multilevel DC-Link Based T-type Converters (MMDTC) with Double Active Bridges (DABs) (namely DABs-based MMDTC-PET), the sub-module capacitor voltages exhibit relatively large ripples. To reduce the voltage ripple of sub-module capacitors, this paper proposes a novel MMDTC-PET structure that utilizes the Three-Port Active Bridges (TABs) to replace the DABs as the isolation stage (TABs-based MMDTC-PET). When the two full bridges of the TAB on the primary side adopt identical phase-shift modulation, the two sub-module capacitors within the upper and lower arms form a parallel connection. This configuration endows the sub-module capacitors with switched-capacitor characteristics, suppressing voltage ripple in the sub-module capacitors and enabling power ripple flow to the secondary side. Meanwhile, by leveraging the characteristic that the AC power components of the upper and lower arm sub-modules have equal amplitudes but opposite phases, these AC power components are mutually canceled on the secondary side of the TAB. Simulation and experimental results verify the effectiveness of the proposed scheme. Full article