Search Results (1,175)

The nucleic acid amplification reaction has extremely high requirements for the precision of temperature control. The conventional PID control algorithms exhibit limitations in nonlinear and time-varying PCR temperature control systems, including poor adaptive parameter adjustment, excessive overshoot, and insufficient steady-state precision, which directly restricts the efficiency and specificity of nucleic acid amplification. This paper focuses on the design and optimization of the fuzzy PID temperature control algorithm. By combining the nonlinear adaptive advantages of fuzzy control and the steady-state precision of PID control, a temperature control algorithm model suitable for the thermal convection nucleic acid amplification instrument was constructed. This device can adapt to the thermal convection temperature control mode, providing a stable reaction platform for the subsequent algorithm performance testing and nucleic acid amplification experiments. For this fuzzy PID temperature control algorithm, this study established a simulation model using MATLAB/Simulink R2020a by defining the fuzzy input and output variables and designing the membership functions and fuzzy rule base. A performance comparison of temperature control was then conducted between this algorithm and the conventional PID algorithm. The nucleic acid amplification experiment verified the effectiveness of this algorithm in practical applications. The simulation results demonstrate that the fuzzy PID algorithm significantly suppresses the system overshoot, effectively shortens the adjustment time, and achieves a steady-state control precision of ±0.05 °C. The temperature control system equipped with this algorithm achieves a heating rate of 7.5 ± 0.1 °C/s, a cooling rate of 13.5 ± 0.1 °C/s, a steady-state temperature deviation of only ±0.1 °C, and an amplification efficiency of 98.7%. All performance indicators are superior to those of the conventional PID temperature control system and existing commercial instruments. This fuzzy PID temperature control algorithm provides crucial technical support for enhancing the efficiency, specificity, and repeatability of nucleic acid amplification, and holds broad application value in the biotechnology field with high requirement on precision temperature control. Full article

p-GaN gate enhancement-mode GaN High Electron Mobility Transistors (HEMTs) are promising normally off power devices, but their high-temperature reliability is strongly affected by the gate-contact scheme. This study compares Pd ohmic and Ni Schottky p-GaN gate HEMTs fabricated on the same GaN-on-Si epitaxial platform by combining temperature-dependent electrical characterization, post-temperature-dependent-test (TDT) room-temperature recovery analysis, and thermoreflectance thermal mapping. Electrical measurements were performed in a temperature range from room temperature to 500 °C using gate leakage, transfer, and output characteristics, while thermal maps were obtained before and after the TDT under identical bias conditions. The Pd ohmic devices exhibited a higher initial current drive but a larger operating gate-current penalty and greater degradation of normalized on-state characteristics at elevated temperature. After the TDT, reduced transconductance and maximum drain current were accompanied by weaker active-channel heating, indicating degradation-type cooling associated with reduced gate–channel modulation efficiency. In contrast, the Ni Schottky devices showed a lower gate-current penalty and better normalized output retention up to approximately 300 °C; however, post-TDT increases in transconductance and drain current occurred together with degraded subthreshold swing and persistent localized heating, indicating apparent on-state activation with weakened gate/depletion control. These results show that p-GaN gate reliability should be assessed through coupled electrical and thermal signatures rather than single electrical or thermal metrics. Full article

Monopolar radiofrequency (MRF) is a well-established modality for non-invasive facial rejuvenation; however, its clinical utility is frequently constrained by patient discomfort and inconsistent thermal delivery. This study evaluated the efficacy, safety, and mechanistic profile of a novel MRF system incorporating continuous water cooling (RF-CWC) designed to optimize thermal distribution and enhance patient tolerance. In a prospective, single-arm clinical trial involving 22 female participants, a single RF-CWC treatment utilizing region-specific static and sliding delivery modes yielded statistically significant improvements in jawline lifting, alongside a volumetric increase in the midface and a concomitant volumetric reduction in the lower face (p < 0.001) over an 8-week follow-up period, with no adverse events reported. To elucidate the underlying cellular mechanisms, the system was further evaluated using an ultraviolet B (UVB)-induced ex vivo human skin model and an in vivo porcine model. Histological, immunohistochemical, and ELISA analyses revealed that RF-CWC effectively mitigated UVB-induced dermal degradation ex vivo by significantly up-regulating elastin, insulin-like growth factor, and hyaluronic acid, while down-regulating matrix metalloproteinase-1, interleukin-1α, and heat shock protein 72 (p < 0.05). Furthermore, the in vivo model demonstrated time-dependent increases in collagen types I and III and elastin without thermal tissue damage, with the sliding mode and higher shot counts correlating with enhanced extracellular matrix (ECM) remodeling. Comparative analyses demonstrated that RF-CWC achieved superior ECM restoration and reduced inflammatory cell infiltration relative to traditional cryogen spray-cooled RF systems. Taken together, these findings suggest that the RF-CWC system may promote robust ECM remodeling and significant facial neocollagenesis while minimizing inflammatory responses, potentially presenting an optimized, highly effective, and patient-friendly advancement in MRF technology. Full article

The sol–gel coprecipitation method is highly efficient for synthesising a wide range of binary perovskite solid solutions (SSs), which have been under exhaustive study due to their semiconductor and catalytic properties. Therefore, we conducted a systematic study to extend the chemical stability of the cubic structure in Zr⁴⁺-rich SS in the system SrTiO₃–SrZrO₃. The proposed new approach involves in situ gel coprecipitation and simultaneous hydrothermal processing, which was conducted at standard conditions (200 °C for 6 h) in a KOH (5 M) solution under stirring at 130 rpm. The formation of the cubic perovskite-structured SS occurred in the compositional range from 10.0 to 100.0 mol% Ti⁴⁺. The particle crystallisation was achieved via the dissolution-crystallisation mechanism, which proceeded rapidly, aided by preliminary gel dehydration and vigorous stirring. The prepared particles, either orthorhombic or cubic, have a unique morphology, resembling a pseudocuboidal shape with rounded edges. The particle size decreases as the Ti⁴⁺ content in the SSs increases, due to improved gel solubility. The band gap of the cubic intermediate SSs is sharp, ranging from 3.12 to 3.57 eV; thus, these perovskites can be applied in the development of semiconductor devices and in catalysis. These powders can also be employed as cool pigments due to their high NIR solar irradiance of 80.22%. Full article

Earth–Air Heat Exchangers (EAHEs) are passive systems that use the thermal interaction between air and soil along buried ducts to moderate supply air temperature, thereby lowering building energy consumption and improving indoor comfort conditions. This device has been employed in several countries and under diverse climatic characteristics. The integration of EAHE systems with bioclimatic design strategies contributes to improved building energy performance and more efficient use of thermal resources. This study aims to computationally investigate the thermoenergetic performance of EAHE system, for both cooling and heating purposes, installed in Social Housing (SH) across different Brazilian bioclimatic zones, and to propose strategies that improve the energy efficiency of these built environments. The study involves the validation and verification of a computational model and the thermoenergetic assessments of an SH unit, investigating different solar orientations and the installation of EAHE. These evaluations are performed via dynamic simulations conducted with the EnergyPlus software. The results show that the installation of the EAHE system coupled to the SH improves the thermoenergetic performance of the indoor environment, mainly by enhancing thermal comfort across different Brazilian bioclimatic zones (BZ). In BZ2R, the EAHE increased the annual PHFT by 4.5%, corresponding to seventeen additional days per year within the acceptable operative temperature range. The highest monthly improvement was observed in BZ1M, where the PHFT increased by 14.3% in January, equivalent to more than four additional days of thermal comfort in that month. The system proved to be more effective in zones 1M, 2R, 3B, and 4B, particularly in climates with lower annual average dry-bulb temperatures. Regarding energy performance, the EAHE showed benefits in specific months and conditions, indicating that its feasibility should be assessed through monthly thermoenergetic analyses rather than only annual indicators. This work provides validated and verified references and parameters for future projects and contributes to the state of the art in this field, as there are still few studies evaluating EAHE systems integrated into buildings using this software, despite its widespread use in building performance analysis. Full article

Thermal tactile perception plays a crucial role in enhancing realism and immersion in human–machine interaction, virtual/augmented reality, and wearable systems. By exploiting the thermoelectric effect to achieve precisely controllable heating and cooling, wearable thermoelectric devices (WTEDs) offer an effective approach for generating localized and programmable thermal sensations, which calls for a clear understanding of skin temperature regulation mechanisms. In this work, a dynamic thermal conduction model is developed for a skin–WTED integrated system incorporating a nickel foam-reinforced hydrogel heat sink, based on the dual-phase lag (DPL) bioheat conduction theory. The model accounts for blood perfusion and metabolic heat generation in skin tissue, as well as the Thomson effect within the thermoelectric legs and convective heat losses from their side surfaces. The theoretical predictions are validated through human skin temperature regulation experiments using a fabricated WTED, showing close agreement between experiments and simulations and confirming the model’s accuracy and reliability. Based on the validated model, the cooling current, filling factor, and thermoelectric leg height are optimized by minimizing the skin surface temperature. Furthermore, the model is applied to thermal tactile feedback studies, enabling the controlled reproduction of skin thermal sensations associated with common objects, including an iron block, a PMMA plate, and carbonated beverages packaged in aluminum cans and plastic bottles. Overall, this study provides a practical and predictive framework for understanding, optimizing, and applying WTEDs in thermal tactile feedback. Full article

Liquid crystal physical gels (LCPGs) combine the anisotropic properties of liquid crystals with the structural stability of soft solids. In this work, MBBA-based LCPGs were prepared using chiral oxalamide gelators 1,6-bis((O-leucylmethanol)-N-yloxalamido)hexane (6-O-Me) and 1,9-bis((O-leucylmethanol)-N-yloxalamido)nonane (9-O-Me) and thoroughly characterized for their thermal, rheological, and electrorheological behaviours. Techniques included differential scanning calorimetry, oscillatory rheology, electrorheological testing, and advanced microscopy analysis. A custom microfluidic device was developed for in situ application of an electric field and optical assessment of its influence on microstructure formation. Both gels exhibited distinct gel-like behavior, with storage moduli consistently exceeding loss moduli and sustained network stability under both short- and long-term deformations. The gelators had minimal effect on the isotropic–nematic transition of MBBA but efficiently delayed crystallization, extending the stability window by −8 °C for 9-O-Me and −14 °C for 6-O-Me. When subjected to electric fields, the gel network weakened in the nematic phase, and the fiber assembly during cooling was altered, resulting in the formation of thicker, anisotropic fibers, consistent with microscopic observations. These results illustrate how the properties of LCPGs can be tuned through molecular design and external stimuli, expanding their potential for stimuli-responsive soft matter applications. Full article

The rapid growth of electromobility and the increasing deployment of EV chargers emphasize the importance of pulse rectifiers with built-in power factor correction (PFC) filters. The new switching power devices offer higher converter switching frequencies, which enable a decrease in nominal values of passive components, such as inductors and capacitors, and their physical dimensions. Devices like CoolMOS and GaN enable operation with low switching power, but are usually constructed for lower drain-source voltage. From this point of view, the Vienna Rectifier is a prospective type of pulse rectifier with built-in PFC because of its reduced blocking-voltage requirements for the power transistors. Nevertheless, faster switching semiconductor devices with lower switching gate charge require more precise driving circuit tuning and setup. There are many scientific papers focused on the driving setup and techniques of the power transistors applied in H-bridge topologies. The purpose of this paper is to investigate the commutation loop and the related switching phenomena of the Vienna Rectifier topology. This paper evaluates the driver setup for a CoolMOS-based Vienna Rectifier with anti-serial connection of transistors forming a bidirectional switch. The switching transients are analyzed and simulated. Subsequently, the real driver settings are evaluated on the real prototype. Full article

Marine invertebrates exhibit diverse thermoregulatory capabilities enabled by hierarchical architectures, porous skeletal frameworks, and adaptive interfaces. These biological features provide engineering cues for controlling heat conduction, convection, and radiation, particularly when lightweight and multifunctional thermal designs are required. This review surveys marine-invertebrate-inspired thermal management from an engineering perspective and synthesizes biological structure–function relationships into transferable design concepts. Literature was collected from Scopus, Web of Science, and Google Scholar. Studies were included if they (i) explicitly referenced marine invertebrate morphology, structural organization, interfacial behavior, or adaptive mechanisms and (ii) quantitatively reported thermal metrics such as thermal conductivity, heat capacity/latent heat, heat dissipation performance, or temperature modulation. To maintain biological scope while enabling cross-comparison, the review is organized across major marine invertebrate phyla frequently used in bioinspired engineering—Mollusca, Porifera, Cnidaria, Echinodermata, and Arthropoda—and the engineering literature is classified into three categories: (A) bio-inspired functional materials for thermal transport or optical–thermal control; (B) bio-inspired structural architectures that guide heat flow via hierarchical or porous geometries; and (C) integrated thermal management systems that couple multiple mechanisms at the device or system scale. Across these categories, the reviewed studies demonstrate promising routes toward electronics cooling and aerospace thermal protection. Remaining challenges include scalable fabrication over large areas, flow uniformity in microchannel-based platforms, and long-term reliability under combined pressure, salinity, and thermal cycling. Full article

This study presents a low-cost, practical approach for determining the average trip current level from a statistically significant sample of polymer positive temperature coefficient (PPTC) fuses. The experimental method uses a controlled constant-current source (CCS) to test PPTC fuses over a range of standard room temperatures without an expensive temperature chamber. This novel approach enables designs to practically investigate the reliability of trip current levels for equivalent specified PPTC fuses from different manufacturers. The experimental setup uses a calibrated CCS circuit to incrementally increase current through a PPTC fuse by 0.01 A. The current flow duration for each applied CCS setting was set to the specified time-to-trip value before device trip determination. The trip condition is identified when the sensed PPTC current drops to 50% of the specified fault trip current. To prevent thermal runaway, an empirically determined zero-current cool-down period separates each current increment. Testing revealed differences in the average trip currents of PPTC fuse samples from different manufacturers: 1.26 A, 1.10 A, and 1.06 A, respectively. The determined 95% confidence interval trip-current ranges also revealed a significant difference between PPTC manufacturer populations. The findings reveal that PPTC determined average trip current within the standard room-temperature range can serve as an effective comparison metric between manufacturers with equivalent device specifications. Full article

This study investigates the effects of flow distributor placement and loosener configuration on particle-flow behavior in a hydrogen-based direct reduction shaft furnace using the discrete element method (DEM). A three-dimensional industrial-scale furnace model based on a MIDREX-type geometry was established, and four representative structural configurations were examined by varying the flow distributor position and loosener setting. The results show that flow distributor placement is the dominant factor controlling particle descending behavior and particle-flow uniformity. When the flow distributor was located in the cooling zone, the flow uniformity index reached 0.875, which was 40.9% and 20.9% higher than those for the transition–cooling interface and transition-zone configurations, respectively. Particle trajectory analysis indicates that the effect of flow distributor position is mainly confined to the region above the device, with limited influence on the lower burden trajectory. Although the loosener has little effect on particle-flow uniformity, it significantly suppresses particle degradation. Under the transition-zone flow distributor configuration, the predicted powder formation ratio decreased from 3.89% to 2.97% after introducing the loosener, corresponding to a relative reduction of 23.7%. Overall, among the four representative configurations investigated in this study, positioning the flow distributor in the transition zone while retaining the loosener provides a more balanced compromise between burden-flow regulation and powder suppression for shaft furnace design and industrial operation. Full article

Miniature vapor compression refrigeration systems are gaining increasing relevance in cutting-edge applications such as drone docking station cooling, electric vehicle battery thermal management, portable medical and diagnostic devices, compact beverage dispensers, field-mounted telecom cabinet cooling, as well as the already established fields of electronics and personal cooling. These systems offer a promising pathway to localized and mobile cooling solutions. When coupled with the implementation of alternative low-GWP refrigerants that match or even enhance system performance, the result is a more efficient, environmentally responsible, and potentially sustainable refrigeration technology. Therefore, this study experimentally evaluates the performance of R515B as a low-GWP drop-in replacement for R134a in a miniature vapor compression refrigeration system. Key parameters were analyzed to determine the most suitable operating conditions, resulting in a capillary length of 1.25 m, refrigerant charge of 110 g, compressor speed of 4500 rpm, and high condenser fan speed, under which R515B achieved a COP of 5.16 and a cooling capacity of 252.20 W, representing improvements of 38% and 6.5%, respectively, compared to R134a. These results confirm the viability of R515B as an efficient, environmentally friendly alternative for miniature small-scale vapor compression systems. Full article

Rapid growth in fossil-fuel consumption has amplified the severity of global climate issues, making the deployment of renewable energy solutions increasingly imperative. Among candidate approaches, adsorption-based technologies are attractive; however, the limited adsorption capacity and kinetic performance of traditional adsorbents constrain composite-cycle efficiency and hinder large-scale implementation. In this work, we develop and evaluate a new class of composite adsorbents prepared by impregnating metal–organic frameworks (MOFs) with hygroscopic chloride salt solutions (LiCl, CaCl₂, and MgCl₂). Owing to their enhanced sorption characteristics, the resulting materials support an integrated adsorption cycle in which one device can simultaneously realize refrigeration, space heating, seawater desalination, and power generation. Under standard operating conditions, experiments demonstrate that MOF–vermiculite composites deliver a cooling coefficient of performance (COP) of 0.71, a heating COP (COP_h) of 1.30, a specific power-generation output of 27.2 kJ/kg, and a desalination yield of 0.71 g/g. Collectively, these metrics outperform the majority of previously published results, indicating that composite adsorbents can substantially improve the efficiency and practicality of renewable energy conversion systems. Full article

Population growth, industrialization and climate change have placed increasing stress on natural freshwater reserves, making conventional water sources inadequate. Coupled with rising energy constraints and environmental concerns, interest in desalination technologies that can operate more sustainably and efficiently has intensified. Among the available approaches, membrane desalination has gained particular importance because of its modularity, relatively low energy demand, and compatibility with decentralized water treatment. In parallel, thermoelectric devices have emerged as promising components for hybrid desalination systems due to their ability to convert temperature gradients into electricity or provide localized heating and cooling for process enhancement. This article presents a narrative review of thermoelectric integration in desalination systems, with particular emphasis on membrane desalination and membrane-hybrid water treatment configurations powered by renewable-energy or low-grade heat sources. The review examines the role of thermoelectric devices in relation to key membrane-based and hybrid desalination processes, including reverse osmosis, membrane distillation, electrodialysis, nanofiltration, forward osmosis, and selected hybrid systems. Particular attention is given to system configurations, renewable energy coupling pathways, functional roles of thermoelectric devices, water productivity, module output, desalination efficiency, water quality, and economic performance. The reviewed literature indicates that thermoelectric integration can provide meaningful benefits in hybrid desalination, particularly through improved thermal management, enhanced utilization of low-grade heat, and supplementary energy recovery. These opportunities appear especially relevant for thermally driven membrane systems such as membrane distillation and for membrane-hybrid configurations intended for decentralized or renewable-powered applications. However, the available evidence remains highly heterogeneous, with substantial variation in system scale, operating conditions, reporting metrics, and cost assumptions, which limits direct cross-study comparison and broad generalization of performance claims. This review highlights the technical challenges, reporting inconsistencies, and research gaps that currently constrain the practical development of thermoelectric-assisted membrane desalination and outlines future directions for membrane-aligned hybrid desalination research. Full article

As the heat flux of electronic devices continues to increase, conventional air cooling and single-phase liquid cooling technologies are increasingly constrained by heat transfer limits and pumping power consumption. However, systematic investigations on the coupling between microchannel evaporators and the overall dynamic response of MPTL systems remain limited. To address this issue, a visualization experimental platform for the microchannel MPTL was developed, and flow boiling experiments were conducted under varying heat fluxes and circulating flow rates. Key parameters including wall temperature, fluid temperature, pressure drop, and flow patterns were measured to characterize the thermal–hydraulic behavior of the system. The results show that the wall temperature increases stepwise with increasing heat flux, reaching a critical heat flux of 814.2 W/cm² at a mass flux of 105.6 kg/(m²·s), where heat transfer deterioration occurs. During this transition, inlet temperature oscillations with an average amplitude of 8 °C were observed due to vapor backflow. With decreasing circulating flow rate, the flow pattern evolved sequentially from single-phase flow to bubbly, slug, churn, annular, and reverse annular flow, accompanied by a shift in the dominant heat transfer mechanism from forced convection to nucleate boiling and convective evaporation. The best heat transfer performance occurred under annular flow conditions at an outlet vapor quality of 0.4–0.5. These findings provide useful guidance for the design and operation optimization of microchannel MPTL systems in high-heat-flux electronic cooling applications. Full article