Search Results (423)

Polyurea elastomers are widely used in industry thanks to their exceptional mechanical properties. However, cold-pour systems typically require extended ambient curing times to achieve optimal performance. This study investigates whether accelerated thermal curing can replicate or exceed the mechanical properties obtained through the standard ambient cure protocol. Specimens were prepared by hand-mixing and then cured at temperatures of 50 $°\mathrm{C}$ and 70 $°\mathrm{C}$ for 1 h, 3 h and 6 $\mathrm{h}$. Selected specimens were then aged at room temperature for up to 7 d. Uniaxial tensile tests were conducted, with strain measured via a video-tracking technique. Porosity analysis was performed using cross-section micrographs. The results show that a 6 $\mathrm{h}$ cure at 50 $°\mathrm{C}$ yields mechanical properties comparable to those obtained through the standard ambient cure, while a 6 $\mathrm{h}$ cure at 70 $°\mathrm{C}$ significantly surpasses them. Post-cure aging was found to be particularly effective for specimens with a thickness of 1.5 $\mathrm{m}$$\mathrm{m}$, achieving a tensile strength of 4.7 $\mathrm{M}$$\mathrm{Pa}$ after 7 d, exceeding that declared by the manufacturer. Full article

Non-insulated heat exchangers in gas-to-gas service lose substantial energy to the surroundings. This study evaluates Al₂O₃ and ZnO ceramic coatings (200 $\mathsf{\mu }$m) as passive thermal retention layers on the inner surface of the outer tube in a copper double-pipe heat exchanger, using 3D CFD simulations verified for internal consistency against Log Mean Heat Transfer Rate analytical solutions. Six cases were modelled: three coating conditions across parallel-flow and counter-flow configurations under laminar conditions ($R{e}_i\approx 525$, $R{e}_o\approx 192$) with air as the working fluid. The coating elevates the outer tube inner wall temperature $T_3$, increasing the convective driving force to the cold fluid while suppressing ambient dissipation. In parallel flow, Al₂O₃ increases the net inter-fluid heat transfer rate by 35.7% and reduces ambient losses by 81.4%; ZnO achieves 30.9% and 70.4%, respectively. In counter-flow, Al₂O₃ yields a 26.6% enhancement and 73.2% loss reduction. The coated parallel-flow configuration outperforms the uncoated counter-flow baseline. Thermal circuit analysis shows that Al₂O₃ superiority arises from its higher conductivity (40 vs. 19 W m⁻¹ K⁻¹), which sustains a higher equilibrium $T_3$ and a heat partition ratio of 11.84 versus 7.17 for ZnO. These results show that a single ceramic coating layer can recover a large fraction of the thermal energy lost through non-insulated walls, offering a low-cost, retrofit-compatible pathway to improve the energy efficiency of gas-to-gas heat exchangers in HVAC, building energy recovery, and industrial process heat applications. Full article

Ambient temperature is a continuous environmental input that affects energy homeostasis through integrated physiological programs. In mammals, thermal cues detected by cutaneous and visceral sensors are conveyed through spinal, vagal, and sympathetic pathways. They are complemented by circulating mediators from the gut, liver, and adipose tissue. These signals converge on brainstem–hypothalamic networks, including the preoptic area and arcuate nucleus, to coordinate feeding behavior, thermogenesis, vasomotor tone, and endocrine outputs. Recent circuit-mapping and single-cell approaches have refined the cellular logic governing the distinct architectures of cold- and heat-defense programs. This review synthesizes these advances to illustrate how a plastic effector network maintains systemic energy homeostasis. Finally, we highlight the translational implications of these thermosensory mechanisms for treating obesity and type 2 diabetes. Full article

To investigate the influence of external ambient temperature on the transmission characteristics of laser propagation in an internal channel, a simulation model of laser transmission within a closed channel is established in this study. The model comprehensively considers factors including gas density, refractive index distribution, and thermal deformation of optical components. Based on optical transmission theory, the model is used to calculate the beam drift characteristics and the variation in the Strehl ratio at different temperatures. The results indicate that ambient temperature has a significant impact on beam stability and quality. At low temperature (−30 °C), speckle structures appear in the laser spot, with minor drift along the X direction but obvious negative drift along the Y direction, mainly caused by the sinking of cold air driven by gravity and the refractive index gradient. The beam drift decreases initially with increasing temperature, reaches its minimum at around 10 °C, and then increases gradually as the temperature continues to rise. The Strehl ratio initially increases during the early stage of temperature rise, but diminishes in the high-temperature range due to intensified gas disturbances, enhanced thermal lensing effects, and aggravated mirror surface deformation. Full article

To address the critical challenges of lithology acquisition and low blasting refinement under extreme low temperatures and varying thermal conditions in high-altitude environments, this study develops a real-time dynamic identification method for rock-like interfaces using Measurement While Drilling (MWD) technology. The scope of this research involves the use of a self-developed indoor digital drilling experimental platform to simulate both ambient and freezing (−20 °C) conditions. Procedures included conducting comprehensive comparative drilling experiments on various rock-like materials with distinct strength levels to evaluate their mechanical responses during penetration. The major findings reveal a significant influence of low-temperature hardening effects on MWD parameters; specifically, the frozen state notably increases drilling torque and feed pressure while simultaneously decreasing the stable rotational speed of the drill bit. To resolve the feature parameter drift induced by temperature variations, a novel interface recognition algorithm is proposed that integrates Z-score normalization, change-point detection, and multi-dimensional spatial clustering. Through a dual-detection mechanism involving both single-point and cumulative features, the algorithm effectively captures precise mutation information during rock layer transitions. It further incorporates multi-dimensional indicators, such as consistency, change intensity, and point density, to perform comprehensive weighted scoring. Experimental results demonstrate that the proposed algorithm effectively eliminates the systematic offset of parameters caused by temperature fluctuations. The prediction error at both “strong-weak” and “weak-strong” transition interfaces is maintained within 1.5 mm, which significantly improves the accuracy and robustness of interface recognition under complex and varying working conditions. These key conclusions provide essential technical support for the implementation of differentiated charging and green refined mining operations, ensuring greater energy efficiency and environmental protection in cold-region engineering. Full article

Skeletal muscle development and physiological homeostasis are profoundly influenced by environmental cues. Among these factors, ambient temperature represents a critical determinant of growth performance and metabolic adaptation in mammals. However, the effects of different ambient temperature ranges on skeletal muscle characteristics and on responses across multiple visceral tissues remain poorly understood. In this study, five ambient temperature conditions (16 °C, 20 °C, 24 °C, 28 °C, and 32 °C) were established to investigate their physiological impacts in a mouse model. Our results demonstrate that ambient temperature markedly influences growth performance and skeletal muscle phenotype. Notably, mice housed at 20 °C showed relatively preserved grip strength and a shift in myofiber cross-sectional area distribution, although these findings did not consistently indicate superior skeletal muscle development across all indices. Further analysis revealed that ambient temperature significantly modulated the expression profiles of myosin heavy chain (MyHC) isoforms in skeletal muscle. Specifically, cold exposure was associated with an upregulation of the slow-twitch-related MyHC I, whereas heat stress correlated with an elevation of the fast-twitch-related MyHC IIb. Functional assessments indicated that exposure to colder or hotter conditions was associated with impaired muscle performance, as reflected by reduced grip strength at 16 °C, 28 °C, and 32 °C, and decreased endurance capacity at 28 °C and 32 °C. Histological analyses of major visceral organs revealed no obvious structural alterations in the heart, liver, spleen, lung, or kidney across temperature conditions. However, exposure to thermal extremes (16 °C and 32 °C) significantly reduced intestinal villus height, suggesting compromised intestinal integrity under temperature stress. Collectively, these findings indicate that ambient temperature is associated with multi-tissue changes in skeletal muscle characteristics, functional performance, and intestinal morphology. This study provides new insights into how environmental temperature modulates tissue adaptation and physiological homeostasis in mammals. Full article

The thermal safety and longevity of lithium-ion batteries are critically constrained by excessive temperature rise and spatial thermal non-uniformity, particularly during high-rate discharges. Most existing numerical investigations rely on simplified heat generation models that fail to capture the spatiotemporal heterogeneity of electrochemical heat sources, leading to compromised predictive accuracy. To address this deficiency, this study develops a comprehensive three-dimensional electrochemical–thermal coupled framework, integrating the Newman pseudo-two-dimensional (P2D) electrochemical model with conjugate heat transfer and laminar flow dynamics. The predictive robustness of this framework is rigorously validated against experimental data across multiple discharge rates (3 C and 5 C). The validated model is then deployed to evaluate a water-cooled microchannel cold plate designed for prismatic $\mathrm{L}\mathrm{i}\mathrm{M}{\mathrm{n}}_2{\mathrm{O}}_4$/graphite cells under a demanding 5 C discharge. A systematic parametric investigation is conducted to quantify the effects of ambient temperature (293–343 K), microchannel number (2–6), and coolant inlet velocity (0.1–0.6 m/s) on the maximum battery temperature (${\mathrm{T}}_{\mathrm{m}\mathrm{a}\mathrm{x}}$) and temperature difference ($\mathsf{\Delta }\mathrm{T}$). Results demonstrate that the proposed system exhibits exceptional environmental robustness: over a 50 K ambient temperature span, ${\mathrm{T}}_{\mathrm{m}\mathrm{a}\mathrm{x}}$ increases by merely 2.0 K, remaining safely below the 323 K industry limit. Densifying the channel count from 2 to 6 further reduces ${\mathrm{T}}_{\mathrm{m}\mathrm{a}\mathrm{x}}$ by 1.55 K and narrows $\mathsf{\Delta }\mathrm{T}$ to 4.25 K, successfully satisfying the strict 5 K temperature uniformity standard. Furthermore, the thermal benefit of elevating inlet velocity exhibits a pronounced diminishing-return trend governed by the asymptotic reduction in bulk coolant temperature rise, dictating a critical trade-off against the quadratically escalating pumping power. Ultimately, these findings provide robust theoretical guidelines for the rational design of safe and energy-efficient battery thermal management systems. Full article

In the postharvest supply chain, directly moving Korla fragrant pears from ice temperature storage to ambient display readily induces quality deterioration, shortens shelf life, and causes substantial economic losses. Using Korla fragrant pears as the study system, we propose a gradual rewarming protocol. We optimised temperature and time parameters with response surface methodology and validated the protocol by comparing changes in shelf-life quality and microstructure under gradual versus direct rewarming. Results indicate that rewarming at 6 °C for 12 h is the optimal condition for maintaining overall postharvest quality. Under these conditions, gradient rewarming significantly improved physical and chemical quality. Compared with direct rewarming, weight loss decreased by 2.6 percent, firmness increased to 4.23 kg/cm², the peak soluble solids content reached 12.5%, the respiratory peak was delayed and the rate slowed, and shelf life was extended by about 80%. Microstructural verification showed a more compact cellular arrangement, reduced intercellular spaces, and the mildest degree of cell collapse in pears subjected to gradient rewarming. The proposed gradient rewarming protocol provides theoretical and practical guidance for optimising temperature control strategies across the postharvest cold chain and retail stages for Korla fragrant pears. Full article

This paper presents the results from in-lab chassis dynamometer testing of two battery electric vehicles of the same make and model: a 2022 model year vehicle with a heat pump and a 2020 model year vehicle with a resistive positive temperature coefficient (PTC)-type heater. The vehicles were tested over a series of standard drive cycles at −10 °C, −7 °C, 0 °C, and 25 °C to determine the impacts of the different heating systems on vehicle energy consumption and driving range in cold temperatures. The results indicate that in most (but not all) heating situations the heat pump heated its vehicle’s cabin more efficiently than the PTC heater did, especially at 0 °C. At the lowest temperature, −10 °C, the heat pump used more energy than the PTC heater on cold-start but was more efficient than the PTC heater once the cabin was warmed up. Over standard drive cycles and using SAE J1634 calculation methods to obtain a single range value for each cycle type, the improvement in the percentage of driving range retained by the heat pump-equipped vehicle over the PTC heater-equipped vehicle varied between 1% and 15% depending on ambient conditions and drive cycle, with the average advantage in percentage range retained being 7% over the UDDS cycle, 7% over the HWFET cycle, and 4% over the US06 cycle for all cold temperatures combined. Full article

This study presents a numerical investigation of the effects of atmospheric icing on the aerodynamic performance and power output of the NREL 5 MW reference wind turbine. In cold climate regions, ice accretion on wind turbine blades significantly alters the airfoil geometry, leading to aerodynamic degradation characterized by increased drag, reduced lift, and substantial power losses. Understanding these effects is therefore essential for reliable performance prediction and efficient turbine operation under icing conditions. To address this problem, numerical simulations were conducted on six representative blade sections using the FENSAP-ICE framework, which integrates flow field calculations, droplet transport, and ice accretion modeling within a unified computational environment. The analyses were performed under different atmospheric icing conditions, considering liquid water content values of 0.22 g/m³ and 0.50 g/m³ and ambient temperatures of −2.5 °C and −10 °C. The median volumetric diameter was fixed at 20 µm, and the icing duration was set to one hour for all cases, allowing for both glaze and rime ice formations to be systematically examined. The results reveal that ice accretion becomes increasingly pronounced toward the blade tip, mainly due to higher relative velocities and increased collection efficiency in the outer sections. Glaze icing conditions produce irregular horn-shaped ice formations and lead to severe aerodynamic degradation, whereas rime ice forms more compact structures near the leading edge and results in comparatively lower performance losses. The degraded aerodynamic coefficients obtained from the iced airfoils were subsequently incorporated into BEM-based power calculations, indicating that total power losses can reach up to 40% under severe icing conditions, with the outer blade sections contributing most significantly to this reduction. Furthermore, an economic assessment based on annual energy losses highlights the substantial impact of atmospheric icing on wind turbine performance and operational costs. Full article

This study evaluates the feasibility of using two affordable thermal cameras (UNI-T UTi260M and UTi260T), which are not designed as automotive sensors, for observing pedestrians and warm objects during night-time driving under low-illumination conditions. The experimental setup includes mounting the camera on the vehicle body (e.g., side mirror area/roof), recording road scenes in urban and rural environments, and selecting representative frames for qualitative and quantitative analysis. The study assesses: (i) observable pedestrian detectability in unlit road sections and under oncoming headlight glare, where visible cameras often lose contrast; (ii) the influence of low ambient temperature and strong cold wind on image appearance (including “whitening”/contrast shifts); and (iii) workflow differences, where UTi260M relies on a smartphone application for streaming/recording, while UTi260T supports PC-based image analysis and temperature-profile visualization. In addition, a calibration-based geometric method is proposed for approximate pedestrian distance estimation from single frames using silhouette pixel height and a regression model based on 1$/h_{px}$, valid for a specific mounting configuration and a known subject height. Results indicate that both cameras can highlight warm objects relative to the background and support visual pedestrian identification at low illumination, including in the presence of oncoming headlights, with UTi260M showing more stable behavior in parts of the tests. This work is a feasibility study and does not claim Advanced Driver Assist Systems (ADAS) functionality; it outlines limitations, repeatability considerations, and a minimal set of metrics and procedures for future extension. All quantitative indicators derived from exported frames are explicitly treated as image-level proxy metrics, not as physical sensor characteristics. Full article

At temperatures higher than 5 °C in the cooling chambers of refrigeration systems, bacteria multiply rapidly on fresh fishes, thereby leading to an increased risk of foodborne diseases. Maintaining the storage temperature within the recommended bounds of 0 °C and 5 °C is needed to maintain food safety and quality. This study presents model predictive control of a data-driven medium-temperature cold storage system using subspace system identification techniques. The identified linear model presents a holistic view of the whole system, with each subsystem cohesively linked together. The data-driven model was developed from synthetic data derived from a high-fidelity simulation benchmark model of a supermarket refrigeration system from Aalborg University, Denmark. The benchmark model consists of a medium-temperature closed display case, the suction manifold, and the compressor rack. The data of the expansion valve, suction pressure, compressor capacity, heat transfer rate, and ambient temperature were taken as inputs, while the data of the air and goods temperatures were taken as outputs based on expert knowledge. A linear model predictive controller was designed to control the temperature outputs of the identified linear model, and the outputs were compared with the proportional–integral dead band control used in the benchmark. Simulation results for 24 h showed that the model predictive controller was able to achieve an air temperature and a goods temperature within the recommended temperature range of 0 °C and 5 °C that guarantees safe storage of fresh fishes. These results imply that a reduced-order model of a commercial refrigeration system that is robust, reliable, and stable can be developed and controlled to achieve the goal of food safety, thereby guaranteeing food security and reducing costs. Full article

Background: Thermostability remains a key bottleneck for equitable access to mRNA-LNPs vaccines, mainly due to cold-chain requirements. Objectives and methods: Here, we optimized freeze-drying formulations by screening excipients (sugars, sugar alcohols, and proteins) and buffers to preserve mRNA-LNPs as solid formulations under ambient and refrigerated conditions. Physicochemical properties (size, polydispersity index [PDI], and encapsulation efficiency [EE]) and functional integrity, assessed by fluorescence-based in vitro transfection assays, were evaluated during long-term storage of up to six months. Results: Preliminary screening identified 20% sucrose and trehalose with Tris or histidine buffers as optimal for preserving physicochemical properties during freeze-drying, including high encapsulation efficiency (>90%), particle size (~200 nm), and low polydispersity (PDI < 0.2). Mannitol, gelatin, and PBS-based buffers showed adverse effects. At 4 °C, formulations F1–F3 maintained physicochemical stability and functional transfection activity for up to four months. In contrast, 20 °C storage caused progressive destabilization, with increased size, PDI, and encapsulation loss (>60% by six months). Among all formulations, 20% sucrose with 5 mM Tris (F1) showed the most robust preservation of physicochemical integrity and in vitro transfection efficiency under refrigerated and ambient conditions. Conclusions: Sugars outperformed sugar alcohols and gelatin as cryoprotectants. All formulations were stable, including functionally active at 4 °C for up to four months, while a sucrose/Tris formulation retained acceptable stability at 20 °C. Overall, the results demonstrate the feasibility of storing mRNA drug products as solid formulations at non-freezing temperatures. Full article

Heat creep is a critical failure mechanism in fused filament fabrication (FFF) extrusion systems, arising from insufficient thermal isolation between the hot end and cold end. It causes premature polymer softening, extrusion instability, and nozzle clogging, especially when active cooling is reduced or lost. This study experimentally evaluates passive cooling strategies for mitigating heat creep in consumer-class printers by exploiting ambient thermal stratification within the build volume. Vertical air-temperature gradients above heated build plates were measured for enclosed, semi-enclosed, and open-frame architectures, revealing pronounced stratification. Cold-end temperatures were then quantified for a stock extruder under forced and natural convection while printing polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS). Finally, a modified cold-end using a heat pipe to relocate heat rejection to an elevated heat sink was tested under identical conditions, assuming fan failure. Elevated heat-rejection locations experienced lower ambient temperatures and improved natural-convection heat transfer. Relative to the stock configuration, the augmented design reduced cold-end temperatures and improved thermal stability during representative printing cycles without continuous active cooling—the improvement percent is ~8%. The results demonstrate that coupling heat-pipe conduction with environmental thermal gradients can mitigate heat creep and improve extruder reliability with lower energy demand. Full article

With rising customer demands for the timeliness and quality of refrigerated goods, the efficiency and fluidity of cold chain logistics remain inadequate, resulting in a notable imbalance between supply and demand in the cold chain market. To reduce the damage of fresh produce and lower logistics costs, this paper introduces multimodal transportation into the cold chain market and performs an analysis of optimizing multimodal transportation routes for refrigerated goods. This study constructs a mixed-integer programming model for cold chain multimodal transportation, aiming to minimize total costs while considering carbon emissions and uncertain demand. An improved adaptive large neighborhood search (ALNS) algorithm is developed to solve the mathematical model, featuring improved adaptive scoring and operator selection mechanisms. The algorithm’s performance is validated through a real-world multimodal transportation network in China. Furthermore, a sensitivity analysis is performed on rail freight rates, confidence levels, and ambient temperature, from which we derive managerial insights with practical significance. Full article