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A curved heat transfer surface is proposed to improve the condensation process. The flow performance and condensation law in the cosine-shaped flow channel, a special curved surface, are numerically and theoretically studied. A theoretical model of surface filmwise condensation on a curved flow channel is established and the mathematical model is validated. The liquid film thickness equation in different zones of the curved surface is deduced and calculated. The results show that the main condensation heat transfer zone is in the middle zone (25 mm < s < 45 mm) and the wave crest zone (0 mm ≤ s ≤ 25 mm), the temperature gradient of the liquid film surface decreases along the liquid flow direction, and the liquid film thickness becomes thinner with the increase of steam velocity. [ABSTRACT FROM AUTHOR]

The localised heat addition and rapid temperature fluctuations during welding induces significant levels of residual stresses in thick-walled pipe welds. Residual stress so induced by welding, need to be stress relieved; in these thick walled pipes that are extensively used in power plant applications. While thermal stress relieving (SR) serves as a pivotal intervention, field-welded components and sizable weldments, exceeding furnace capacities, necessitate resistance-based, local post weld heat treatment (PWHT). Nevertheless, the local heating of pipes always results in a finite Through-Thickness Temperature Gradient (TTG). Though, heat treatment parameters are governed by standards, to limit TTG for effective SR; observations indicate limitations of these parameters in achieving desired TTG for specific pipe dimensions. Prior studies specify two alternatives viz. widening the heated band and reducing the heating rate to achieve the desired TTG. However, the preferred approach of widening the heat band for larger pipes; necessitate exorbitantly large capacity power sources and expose a wider zone of weldment to critical transformation temperatures which pose practical limitations and attract industrial apprehensions. Thus, to take informed decisions, the relative efficacies of alternatives over the standard governed approach in terms of relief and redistribution of residual stress, capacity of power source required and energy consumed are evaluated through Finite Element (FE) simulation. Valuable insights from FE results, considering the merits, demerits, logical advantages and financial implications facilitating selection of appropriate SR strategy in industrial applications for successfully relieving stress in difficult to SR pipes (thick-walled, SA335P91) are determined and discussed in detail. [ABSTRACT FROM AUTHOR]

The nonlinear free vibrations of elastically supported fiber-reinforced polymer cylindrical shells (FRPCSs) under temperature gradient conditions are investigated using both theoretical and tested techniques. A dynamic model of the FRPCSs with consideration of such complex thermal conditions is firstly established based on the first-order shear deformation theory in conjunction with Hamilton's principle, the Galerkin method, the artificial spring technique, etc. Numerical results at room temperature and in a uniform thermal environment with classical or arbitrary boundary conditions are utilized to give a rough validation of this model. Subsequently, a thermal-vibration system is set up to measure the nonlinear natural frequencies of two FRPCS specimens subjected to four different temperature gradient conditions in free-free boundary constraints, and iterative calculations are performed to identify the temperature-dependent material properties. Finally, the detailed comparisons of calculated and experimental results provide a solid validation of the proposed model. This study offers a practical model tool to forecast the nonlinear free vibrations of the FRPCSs in a complex thermal environment, which can be readily adjusted and extended to other forms of composite shells. Also, the predicted and measured results can help assess the structural thermal-vibration behaviors when the temperature gradient effect needs to be considered. Communicated by Makoto Ohsaki. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of utilizing the finite element method (FEM)-based conductive heat transfer (CHT) analysis simulation to determine temperature gradients and solidification rates at the solid–liquid interface during laser beam oscillation welding. By comparing experimental observations with FEM-based CHT analysis, the underlying microstructural evolution and grain formation during welding were examined. FEM-based CHT enables the calculation of temperature gradients (G) and solidification rates (R), offering insights into the formation of equiaxed structures, which are crucial for suppressing hot cracking. Columnar-to-equiaxed structure transition thresholds, such as G/R and G3/R, accurately predict the emergence of fully equiaxed grain structures, validated by electron backscatter diffraction. This research provides valuable insights into temperature gradients and solidification rates in oscillation welding, guiding process design for achieving refined equiaxed structures and minimizing hot cracks. [ABSTRACT FROM AUTHOR]

This research paper focused on investigating the influence of various factors on steady Couette flow beneath a permeable bed. Factors studied included aligned magnetic field, thermal radiation, temperature gradient heat source, viscous dissipation, and Joules dissipation. The momentum and energy equations governing flow and heat transmission were analytically solved to predict the generation of entropy. The findings were visually presented through graphical representations, which effectively demonstrated the effect of these factors on the fluid's velocity, temperature, entropy production, and Bejan number. In addition, the shear stress and rate of heat transfer coefficient at the channel walls were computed and their behavior was documented in tables to provide further insights. [ABSTRACT FROM AUTHOR]

In the process of preparing polycrystalline silicon using Al-Si alloy purification, the enrichment of primary silicon can effectively reduce the consumption of aluminum and acid in the subsequent pickling process, thereby lowering the separation cost of high-purity primary silicon. Electromagnetic directional solidification is one of the best methods for preparing polycrystalline silicon currently due to its advantages such as simple process and strong controllability. However, there is a lack of systematic research on how various process parameters affect the enrichment of primary silicon. Therefore, this study investigates the effects of initial solidification temperature, crucible initial position, and descent rate on the behavior of primary silicon enrichment during the solidification process of Al-50% Si (mass fraction) alloy, and characterizes the morphology of primary silicon grains within the enrichment zone. The results show that when the initial solidification temperature is 950 ℃, the initial crucible position is -5 mm, and the crucible descent rate is 2 mm/h, primary silicon is mainly concentrated in the lower part of the ingot with a maximum enrichment rate of 79. 1%, which is the optimal combination of processes. At the same time, as the degree of primary silicon enrichment increases, the primary silicon grains change from "disk-like" to coarse "spherical", which helps reduce the inclusion of primary silicon and improve its purity. [ABSTRACT FROM AUTHOR]

This work conducted an exploring study to minimize porosity cavities in a 300 mm × 2000 mm slab by mechanical heavy reduction when it has solidified. Real density measurements of slab samples indicated that, with a heavy reduction of 20 mm to slab after behind its solidification end, slab center was much denser and much more consistent. Porosity volumes at 1/4 and 1/2 width regions of slab were minimized from 5.19 × 10−4 cm3/g to 1.29 × 10−4 cm3/g and from 2.27 × 10−4 cm3/g to 1.05 × 10−4 cm3/g, respectively. Original Position Statistical-Distribution Analysis (OPA) of larger sampled slabs indicated that the heavy reduction was efficiently penetrated from slab surface into center to heal porosity cavities. Obtained results indicated positive influences of heavy reduction in healing porosity holes in slab even after solidification, when the temperature gradient of slab surface and center was about 280 °C. [ABSTRACT FROM AUTHOR]

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Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the unstable vibration of generator unit in nuclear power plant, a rotor dynamics analysis model was established, in which the thermal effect induced by oil shear flow in bearing was considered. One-dimensional energy balance equation was used to solve the journal temperature difference caused by the flow of lubricating oil in the bearing small gap. The average journal temperature difference and its angle during a whirling cycle were obtained. The effect of cross-sectional temperature gradient on shaft bending deformation was calculated, and the equivalent bending moment was obtained. The equivalent bending moment was input to the shaft in finite element model, and the bending deformation of the generator shaft was calculated. The results show that the temperature difference of the journal is induced by the shear flow of lubricating oil in the bearing clearance. The temperature difference of the journal increases with the increase of journal eccentricity and bearing clearance. After the eccentricity of the journal increases to a certain extent and the bearing clearance decreases to a certain extent, the temperature difference of the journal section increases rapidly, exhibiting typical nonlinear characteristics. If the amplitude of synchronous whirling orbit increases, the dynamic eccentricity increases and the cross-sectional temperature difference increases. Journal temperature difference of a certain nuclear power generation unit was calculated using the model. Within a reasonable range of bearing parameters in nuclear power units, the temperature difference can reach 10 ℃. Its impact on vibration is equivalent to the impact of G2.5 level imbalance force on the generator. The periodic vibration fluctuation phenomenon that occurred on a certain type of nuclear power unit was introduced. Test shows that the fluctuation amplitude is related to the lubricating oil temperature. It is pointed that the journal temperature difference produces rotational unbalance, resulting in vibration fluctuation. Unstable vibration is related to lubricating oil viscosity, bearing clearance, eccentricity ratio and unbalanced force. The unstable vibration can be reduced by reducing the viscosity of lubricating oil, increasing the bearing clearance, reducing the eccentricity and unbalance. The engineering verification test of adjusting lubricating oil temperature was carried out. The test results show that increasing the temperature of lubricating oil to reduce the temperature viscosity of lubricating oil is helpful to reduce the unstable vibration. The analysis results by calculation are consistent with the engineering practice. The model established in this study can be used for the analysis of unstable vibration of nuclear power generator units.

Sn–Ag solders are widely used for advanced electronic packaging. The combined effect of Ag element and temperature gradient (TG) on the formation of Sn grains in Cu/Sn-xAg/Cu micro solder joints was elucidated systematically. Numerous small-sized β-Sn grains were formed in both Cu/Sn/Cu and Cu/Sn-0.5Ag/Cu micro solder joints after reflow with or without TG. The Cu/Sn-0.5Ag/Cu joint was found to have more twinning β-Sn structures. The formation of the multiple β-Sn grains in these two joints was attributed to the presence of multiple tetrahedral metastable short-range order (SRO) structures which acted as nuclei for the nucleation and growth of β-Sn. The existence of TG slightly enhanced the preferred orientation characteristics of Sn grains. For the joints with Ag content was or higher than 2 wt%, several Sn grains were formed without TG, while a single or highly oriented Sn grains were observed with TG. The number and orientation of Sn grains were affected by the combined effect of Ag element and TG significantly. The β-Sn grains formed without TG were based on the {101} type cyclic twinning configuration clusters that stabilized by Ag atoms and acted as nuclei. The formation of a single or highly preferred β-Sn grains was benefit from the combined effect of Ag element and TG. The results provide theoretical guidance for optimizing the composition of Sn–Ag solders and controlling the microstructure of the joints, thereby contributing to the advancement of electronic packaging technologies.

A two-step joining approach was proposed to minimize or eliminate decomposition bubbles in laser joining metal to polymer. Finite element simulation was utilized to analyze the temperature distribution and incorporated the bubble shrinkage mechanism and thermal capillary effect, providing the theoretical basis for explaining the reduction in bubbles and their movement. Two experimental setups were employed: with and without laser beam offset. In experiments without offset, the bubbles after the second joining process underwent significant shrinkage, resulting in a notable reduction in volume. In offset experiments, the bubbles not only reduced in size but also exhibited movement and elimination. This was induced by the laser beam offset, which created a temperature gradient perpendicular to the joining direction, triggering thermal capillary effects that caused the bubbles to migrate towards the hotter side and eventually escape from the joint edges. Consequently, the joints obtained through double welding exhibited higher fracture stress as compared to those obtained through single welding. The theoretical analysis of the bubble reduction mechanism aligned with experimental observations, further validated by camera images.

The oxidation resistance of yttria‐stabilized zirconia (YSZ) thermal barrier coatings and conductivity of YSZ solid oxide fuel cells are closely related to the diffusion of oxygen ions (O2−$\text{O}^{2-}$) in YSZ, but the O2−$\text{O}^{2-}$ diffusion behavior in small‐sized YSZ samples under non‐isothermal condition where the temperature gradient (∇T$\nabla T$) could be significant remaining elusive. Herein, we disclose the previously unrevealed effect of extreme ∇T$\nabla T$ on the self‐diffusion behavior of O2−$\text{O}^{2-}$ in both pristine and strained YSZ. It is found that the O2−$\text{O}^{2-}$ self‐diffusion coefficient (D$D$) experiences a nearly one‐fold increase under an extreme ∇T$\nabla T$ around 60 K/Å. The diffusion direction tends to be toward regions of high temperature. Uniaxial stress is revealed to reduce D$D$ due to the increased activation energy of ions, whereas ∇T$\nabla T$ promotes the O2−${\text{O}}^{2-}$ self‐diffusion in the stressed system. These results underscore the role of ∇T$\nabla T$ in influencing the self‐diffusion behavior of YSZ, providing a theoretical guideline for examining ceramics serving in extreme environments. [ABSTRACT FROM AUTHOR]

This study aimed to elucidate the influence of various culture medium components, including carbon sources, nitrogen sources, inorganic salts, suspension agents, and temperature, on the mycelial growth characteristics of Phallus dongsun. Employing single-factor experiments and response surface methodology within glass Petri dishes, the research identified that carrot powder, soybean powder, and ZnSO4 notably enhanced the proliferation of aerial mycelium, significantly augmenting the growth rate of P. dongsun mycelium. The resultant mycelium was observed to be dense, robust, and fluffy in texture. In particular, ZnSO4 markedly accelerated the mycelium growth rate. Furthermore, xanthan gum was found to effectively modulate the medium’s viscosity, ensuring a stable suspension and facilitating nutrient equilibrium. The optimal cultivation temperature was determined to be 25°C, with mycelial growth ceasing below 5°C and mycelium perishing at temperatures exceeding 35°C. The optimal medium composition was established as follows: wheat starch 5 g/l, carrot powder 5 g/l, soybean powder 7.50 g/l, glucose 10 g/l, ZnSO4 0.71 g/l, NH4Cl 0.68 g/l, xanthan gum 0.5 g/l, and agar 20 g/l. Under these optimized conditions, the mycelium of P. dongsun exhibited a rapid growth rate (1.04 ± 0.14 mm/day), characterized by a thick, dense, and well-developed structure. This investigation provides a theoretical foundation for the conservation, strain selection, and breeding of P. dongsun.

The temperature dependences of the thermoelectromotive force of chromium mono and disilicides in the temperature range 200℃÷+600℃ have been studied. For chromium disilicide, the dependence of the thermopower coefficient (α) on temperature (T) has three sections. Chromium monosilicide is characterized by a smooth increase in thermopower with increasing temperatures up to 200℃, and then its constancy. It was revealed that silicides rich in chromium atoms have lower thermopower values than silicides rich in silicon. The maximum thermo-EMF values of 110 μV/K and 190 μV/K were observed for chromium mono- and disilicides, respectively. It was revealed that for chromium silicides the dependence of the dimensionless parameter Q = Z∙T on temperature is linear. The possibility of predicting the technology of synthesis of semiconductor material with optimal thermoelectric properties using the dependence of thermopower on conductivity and the parameter Q on temperature is shown.

Aiming at the problem of moist and thermal coupling effect of winter aqueduct, the finite element model of temperature field, humidity field and humid heat coupling field of concrete box aqueduct with different environmental parameters was established by using Fluent finite element software. Taking an aqueduct in Northwest China as an example, the ambient temperature, ambient humidity and wind speed from January 5 to January 20, 2023 were measured, and the influence of different working conditions on the temperature effects of the aqueduct in the uncoupled and fully coupled state in winter was analyzed. The analysis results show that the most unfavorable temperature difference in winter when the aqueduct is open to water is - 14. 7 ℃ and - 6. 3 ℃ when it is not water. The most unfavorable transverse temperature difference in winter when the aqueduct is open to water is - 10. 2 ℃ and - 6. 2 ℃ when no water is not connected. In the process of humidity diffusion, the humidity in the direction of plate thickness gradually decreases from inside to outside, and the water absorption rate decreases with the increase of time. In the process of moist and thermal coupling, the temperature value of the fully coupled field is less than the temperature value of the non-coupling field, the deflection change value of the fully coupling action of humidity and heat is less than the deflection change value under the non-coupling of humidity and heat, and the tensile stress of the moist and thermal coupling action is less than the tensile stress value under the non-coupling of moist heat, therefore, the full coupling of humidity and heat is beneficial to the deformation of the aqueduct structure. [ABSTRACT FROM AUTHOR]

As the water pipe cooling system is widely applied to controlling temperature in mass concrete structures, the precise simulation of the temperature field in mass concrete with cooling pipes embedded is meaningful. This paper presents an isogeometric analysis (IGA) with NURBS for heat transfer in mass concrete with consideration of the cooling pipe. The proposed method not only achieves the same level of accuracy with fewer nodes but also eliminates the time-consuming process of mesh in the traditional FEM. The coarsest parameter space which depicts small pipe and large concrete precisely is constructed to create an efficient model for numerical computation. In addition, the unique k-refinement in IGA is supposed to be the most appropriate encryption mechanism, and the knot insertion vector for effective refinement is calculated by considering the characteristics of temperature gradient distribution around the cooling pipes. In addition, a different calculation parameter has been discussed to show the stability and flexibility of the IGA. The obtained numerical results demonstrate the accuracy and efficiency of the proposed scheme in the simulation of transient temperature fields in concrete structures with cooling systems. [ABSTRACT FROM AUTHOR]

Direct-current gas-insulated switchgear (DC GIS) is an important device for promoting the lightweight and compact design of offshore wind power platforms. Gas pressure and temperature gradients are crucial factors that must be considered during the design process of the DC GIS. In this study, the multi-physics coupling model of basin insulators considering surface charge accumulation was established, and the corresponding real-sized insulator surface charge measurement platform was constructed. The effects of gas pressure and temperature gradient on the surface charge accumulation characteristics were investigated, respectively. The results show that the effect of gas pressure on the surface charge distribution characteristics depends on the dominant mode of surface charge. When volume conduction is dominant, the effect of gas pressure on the surface charge is negligible. However, when gas conduction is dominant, the accumulation of a uniform charge pattern on the insulator surface increases with the rise in gas pressure. Furthermore, due to gas convection, the temperature of the upper part of the DC GIS is significantly higher than that of the lower part, which leads to a temperature difference between the upper and lower surfaces of the insulator. The charge density on the insulator upper surface near the central conductor rises with the increase in load current. [ABSTRACT FROM AUTHOR]

Bridge early warning based on structural health monitoring (SHM) system is of significant importance for ensuring bridge safe operation. The temperature-induced deflection (TID) is a sensitive indicator for performance degradation of continuous rigid frame bridges, but the time-lag effect makes it challenging to predict the TID accurately. A bridge early warning method based on nonlinear modeling for the TID is proposed in this article. Firstly, the SHM data of temperature and deflection of a continuous rigid frame bridge are analyzed to examine the temperature gradient variation patterns. Kernel principal component analysis (KPCA) is used to extract principal temperature components. Then, the TID is extracted through wavelet transform, and a nonlinear modeling method for the TID considering the temperature gradient is proposed using the support vector machine (SVM). Finally, the prediction errors of the KPCA-SVM algorithm are analyzed, and the early warning thresholds are determined based on the statistical patterns of the errors. The results show that the KPCA-SVM algorithm achieves high-precision nonlinear modeling for the TID while significantly reducing the computational load. The prediction results have coefficients of determination above 0.98 and fluctuate within a small range with clear statistical patterns. Setting the early warning thresholds based on the statistical patterns of errors enables dynamic and multi-level warnings for bridge structures. [ABSTRACT FROM AUTHOR]

Diurnal and seasonal temperature variations cause uniform temperature changes, vertical temperature gradients, and horizontal temperature gradients. Vertical temperature gradients occur when the bridge deck absorbs heat due to solar radiation more than the bottom parts of bridge girders. Consequently, the vertical temperature gradient causes redistribution of bearing reactions, and induces additional flexural stresses in continuous spans. Estimating the vertical temperature gradient effect on continuous concrete bridges requires knowledge of thermal analysis of statically indeterminate structures or advanced three-dimensional (3 D) finite element (FE) analysis. Therefore, this article focuses on developing a simplified analysis method for estimating vertical temperature variations effects on continuous prestressed concrete bridge girders, which is required for bridge design. Restraint moments induced by vertical temperature gradients are investigated using 3 D FE analysis. A total of 115 bridges with different configurations (number of spans, girder spacing, and girder type) were analyzed to estimate the positive thermal moments at support locations. Results from these analyses were then used to develop simplified equations for estimating the positive restraint moments due to vertical temperature gradients from AASHTO LRFD Bridge Design Specifications (BDS). The developed equations are validated using John James Audubon Bridge #2 field data, and for other AASHTO LRFD temperature zones. [ABSTRACT FROM AUTHOR]

Desiccation tolerance of pathogenic bacteria is one strategy for survival in harsh environments, which has been studied extensively. However, the subsequent survival behavior of desiccation-stressed bacterial pathogens has not been clarified in detail. Herein, we demonstrated that the effect of desiccation stress on the thermotolerance of Escherichia coli O157:H7 in ground beef was limited, and its thermotolerance did not increase. E. coli O157:H7 was inoculated into a ground beef hamburger after exposure to desiccation stress. We combined a bacterial inactivation model with a heat transfer model to predict the survival kinetics of desiccation-stressed E. coli O157:H7 in a hamburger. The survival models were developed using the Weibull model for twodimensional pouched thin beef patties (ca. 1 mm), ignoring the temperature gradient in the sample, and a three-dimensional thick beef patty (ca. 10 mm), considering the temperature gradient in the sample. The two-dimensional (2-D) and three-dimensional (3-D) models were subjected to stochastic variations of the estimated Weibull parameters obtained from 1,000 replicated bootstrapping based on isothermal experimental observations as uncertainties. Furthermore, the 3-D model incorporated temperature gradients in the sample calculated using the finite element method. The accuracies of both models were validated via experimental observations under non-isothermal conditions using 100 predictive simulations. The root mean squared errors in the log survival ratio of the 2-D and 3-D models for 100 simulations were 0.25-0.53 and 0.32-2.08, respectively, regardless of the desiccation stress duration (24 or 72 h). The developed approach will be useful for setting appropriate process control measures and quantitatively assessing food safety levels. [ABSTRACT FROM AUTHOR]

High-quality, large-size CaF2 crystals are urgently needed for advanced applications such as deep ultraviolet lithography and aerospace cameras. However, growing such crystals is a challenging task in the field of crystal growth. Heat transfer, flow, and phase change processes of 3, 7, and 20 inch (1 inch =2. 54 cm) CaF2 crystals at different growth stages on the vertical Bridgman growth were conducted by numerical simulation. The results show that as the crystal size increases, the melt flow strength and the area of heat dissipation on the crucible wall increase, resulting in problems such as local depression of the melt-crystal interface, increase in the radial temperature difference, reversal of the temperature difference between the crystal edge and center, and decrease in the axial temperature gradient near the melt-crystal interface. Furthermore, this article discusses optimization strategies for growth rate and power of heater in the growth of large-size CaF2 crystals. [ABSTRACT FROM AUTHOR]

The priming effects (PEs) of soil organic carbon (SOC) decomposition is a crucial process affecting the C balance of terrestrial ecosystems. However, there is uncertainty about how PEs will respond to climate warming. In this study, we sampled soils along a subtropical elevation gradient in China and conducted a 126‐day lab‐incubation experiment with and without the addition of 13C‐labeled high‐bioavailability glucose or low‐bioavailability lignin. Based on the mean annual temperature (MAT) of each elevation (9.3–16.4°C), a temperature increase of 4°C was used to explore how PEs mediate the decomposition of SOC in response to warming. Our results showed that the magnitude of glucose‐induced PEs (PEglucose) was higher than lignin‐induced PEs (PElignin), with both PEs linearly increasing with MAT. Across the MAT (i.e., elevation) gradient, short‐term warming had a constant magnitude of negative effects on PEglucose, whereas rising MAT exacerbated the negative effects of short‐term warming on PElignin. Moreover, the temperature sensitivity of SOC decomposition decreased after adding glucose and lignin across the MAT gradient, suggesting that fresh C inputs may prime the microbial breakdown of labile SOC under warming. Taken together, warming alleviated SOC loss due to PEs through varying mechanisms depending on substrate bioavailability. Warming mediated the PEglucose by increasing available nitrogen and weakening microbial nitrogen‐mining but inhibited the PElignin by shifting from microbial nitrogen‐mining to microbial co‐metabolization. Our findings highlight the role of warming in regulating the PEs and suggest that incorporating the suppression effect of warming on PEs can contribute to the accurate prediction of soil C dynamics in a warming world. Plain Language Summary: Tropical and subtropical ecosystems have the highest vegetation productivity and diversity on earth and play a crucial role in regulating climate change. However, it is unclear how diverse plant‐derived components stimulate microbial decomposition of soil organic carbon (SOC) via a phenomenon called priming effects (PEs) under climate warming. Here, we added two 13C‐labeled substitutions of plant components (e.g., glucose and lignin) to soils collected from a subtropical elevation gradient and carried out a 126‐day lab‐incubation experiment. Warming consistently harmed glucose‐induced PEs (PEglucose), while amplified the negative effect on lignin‐induced PEs (PElignin) across the elevation gradient, suggesting that warming has stronger negative effects on PElignin at warmer sites. Warming mediates the PEglucose by weakening microbial N‐mining but strengthening microbial preferential substrate utilization. This is achieved by reducing substrate‐built microbial biomass and making more substrate for respiration compared to unwarmed soil. In contrast, warming inhibits lignin‐induced PEs by shifting from microbial N‐mining to microbial co‐metabolization. This shift is supported by the positive association between lignin‐induced PEs and lignin‐derived microbial biomass and available nitrogen. Our measurement suggests that warming decreased the intensity of SOC decomposition by downregulating the primed SOC loss with fresh substrate inputs through varying mechanisms depending on substrate bioavailability. Key Points: Soil C priming effect linearly decreases with elevation in subtropicsHigh‐ and low‐quality substrates play opposite but complementary roles in soil C feedback to climate warmingThe suppression effect of warming on priming can contribute to the accurate prediction of soil C dynamics in a warmer world [ABSTRACT FROM AUTHOR]

The repair of magnesium alloy castings is of great importance in terms of engineering and economic benefits. This study employs the cold welding technique to repair the ZM5 alloy, and the effects of current and preheating treatment on the microstructure and mechanical properties were investigated. The increase in current exacerbates the cracks, while the preheating treatment can effectively control them. However, the liquefaction cracks occur near the heat-affected zone after preheating at 300 °C. The microstructure of the repaired zone shows finer dendritic structure consisting of α-Mg and β-Mg17Al12 phases. After preheating treatment, the repaired zone shows the microhardness of 72 HV0.1, higher than the non-preheating samples (65 HV0.1), and the substrate (63 HV0.1). The average tensile strength of the preheated samples is 110 MPa higher than the non-preheating samples, and reaching 88.7% of the substrate. The fracture mechanism for both the substrate and repaired samples was brittle failure. [ABSTRACT FROM AUTHOR]

New types of instabilities associated with crystal anisotropy during thermomigration of rectilinear and curvilinear (annular) zones under the action of a temperature gradient in the silicon-aluminium system are experimentally revealed. A force model of thermomigration is improved, which takes into account vectors of resistance forces to atomic-kinetic processes at the dissolution front. This model explains the observed features of the stable and unstable motion of the linear zones. Reasons and a mechanism of thickenings and kinks of the ends of rectilinear zones, their fragmentation and decay, as well as transformation of annular linear zones into triangular and square zones during thermomigration in the < 111 > and < 100 > directions, respectively, were also explained. [ABSTRACT FROM AUTHOR]

The presence of a temperature gradient (if any) within the ceramic sample is casually ignored during the sintering of ceramic shapes. The present work exposes some serious repercussions of such a thought process and provides simple solutions to mitigate the same; 3 mol.% yttria‐doped zirconia ceramic was used for this study. With the help of the combinatorial finite element analysis (FEA) model and real‐life experiments, our work illustrates the complex interplay of heat transfer mechanisms and reveals the dynamic nature of temperature distribution during the heating and cooling cycles of ceramics. Although the rate of heating is usually assigned as the most important factor during sintering, the present study shows that variations in heat transfer mechanism and sample geometry contribute very strongly to overall temperature distribution during the heating, holding, and cooling cycles. Along with of vertical positioning of the samples (inside the furnace), a bottom supporting ceramic plate with a high thermal conductivity can also help in reducing the temperature gradient between the top and bottom of the ceramic samples. Overall, exposing the sample most for the radiative heat transfer holds the key to successful sintering in order to avoid any phase, compositional, or microstructural heterogeneity across the thickness of the specimen. [ABSTRACT FROM AUTHOR]

Much recent scientific focus has been on the impact of climate change on human and natural environments. However, a particular research gap that we address is evaluating the effect of global warming on land surface temperatures across different spatial contexts, such as elevation, in mountain regions. Our aim is to establish the effect of global warming on daytime land surface temperatures at various elevations and slope aspects of the central Alborz Mountains in northern Iran. The land surface temperature (LST) component is extracted from MODIS Terra sensor satellite images for the period 2001–2021 on a monthly basis (240 images were used). Results indicated that increasing surface temperature trends are more pronounced than decreasing trends. Significant increasing surface temperature trends are observed for the months of January through December and June through July. In contrast, October records significant decreasing trends across all study areas and geographic domains. Rates of surface temperature increases are lower in the northern zones compared to the southern zones of the Central Alborz, for elevations ranging from 1500 to 4000 m above sea level. A key finding is that global warming has increased surface temperatures on both the northern and southern aspects of the western and mid regions of the Central Alborz Mountains, while no changes are noted for the eastern region. [ABSTRACT FROM AUTHOR]

With the use of the asymptotic method, it is shown that the three-layer problem on the conjugate heat exchange in an anisotropic medium with counterflows of liquid, formulated in the zero approximation, is equivalent to the analogous problem formulated using the Newton law. It was established that in the case where the counterflows of liquid in such a medium have equal strengths, the summary convective heat transfer in the medium is suppressed, and the medium takes new properties consisting in the appearance of heat flow mixed in nature, whose value is determined by the relation similar to the Fourier heat conduction law. By this meant that in the case where a temperature gradient is superimposed on a three-layer system of equivalent counterflows of liquid, in it there arises a heat flow having a value proportional to the temperature gradient in the medium and propagating in the direction opposite to the direction of this gradient. The effective coefficient of heat conductivity of medium, generated in it by the counterflows of liquid, separated by an immovable layer, is proportional to the square of the velocity of these flows. An immovable layer in a medium, separating the counterflows of liquid, increases the generation of heat in the medium, and the heat flow generated exceeds substantially the molecular one even in the case where it has a low velocity. Such processes provide the mass exchange in living organisms and their heat exchange with the environment. [ABSTRACT FROM AUTHOR]

The multiphase fluid flow and heat transfer behavior in the steelmaking converter are essential for efficient and stable smelting. Herein, a mathematical model of heat transfer for the hot spot zone of the converter is established. The temperature distribution of the molten bath is clarified, and the effects of operating parameters and the exothermic rate of hot spot zone on the heat transfer behavior of the molten bath are investigated. The results show that the temperature gradient between the hot spot zone and the liquid steel as well as the circulation of liquid steel will lead to the nonuniform distribution of temperature. Both the direction of flow field and the mixing characteristics of molten bath influence the heating rate of molten bath, whereas the direction of the flow field plays a dominant role. In addition, the oxygen lance height has a significant influence on the heat transfer behavior; as the lance height increases from 1.35 to 1.65 m, the heating rate increases by 68.32%. The increase of exothermic rate will remarkably increase the temperature gradient and the heating rate increases by 65.84% and 114.28% when the exothermic rate increases by 1.5 and 2 times, respectively. [ABSTRACT FROM AUTHOR]

Based on High Magnetic field Helicon eXperiment, considering the parabolic distribution and Gaussian distribution of radial plasma density, HELIC code was used to study the influence of temperature and pressure gradient on power deposition, electric field, and current density of Helicon Wave Plasma. Three different gradients (positive, negative, and zero gradient) were selected. The results show that positive temperature gradient is beneficial to increase the relative absorption power at the center of plasma. Compared with negative and zero pressure gradients, positive pressure gradient increases the relative absorption power and weakens the current density at the center of plasma, and increases the electric field intensity at the edge of plasma. Larger edge heating will cause the relative absorption power at edge to rise rapidly, which is not conducive to the coupling at the center of plasma. In practical experiments, it is particularly important to reduce the heating effect at edge by cooling the antenna itself. Three different gradients of temperature and pressure have little effect on electric field intensity and current density in plasma, and the variation trend is basically similar, which proves the stability of the antenna mode: m = 1. [ABSTRACT FROM AUTHOR]

The fully nonlinear equations of gas dynamics are solved in the framework of a numerical approach in order to study the stability of the steady mode of Rayleigh-Bénard convection in compressible, viscous and heat-conducting gases encapsulated in containers with no-slip boundaries and isothermal top and bottom walls. An initial linear temperature profile is assumed. A map of the possible convective modes is presented assuming the height of the region and the value of the temperature gradient as influential parameters. For a relatively small height, isobaric convection is found to take place, which is taken over by an adiabatic mode when the height exceeds the critical value, or by a super-adiabatic mode in case of a relatively high temperature gradient. In the adiabatic mode, convective flow develops due to adiabatic processes given a stable initial stratification. An analytic formula for the critical height of the region is derived taking into account and neglecting the dependence of the gas viscosity on the temperature. Moreover, an analytic formula is obtained for the upper boundary of the region of applicability of the Boussinesq approximation for incompressible gases. These models for compressible gases are relevant to practical situations such as the study of convective flows in spatially extended gas mixtures when dealing with safety issues related to hydrocarbons stored in gas stations. A dangerous situation arises when the tank is almost empty but some hydrocarbon is left at the bottom of the tank. In the presence of convective flows, the vaporized fuel is mixed with the oxidizer (air) forming a gas-vapor medium. However, if the volumetric concentration of fuel vapor (hydrocarbon) is in the interval between the lower and upper concentration limits of ignition, then the gas-vapor mixture becomes explosive and any accidental spark is sufficient to cause an emergency. [ABSTRACT FROM AUTHOR]

The unique structural design of an arch ring featuring varying inclination angles for individual segments causes variations in the longitudinal distribution of the temperature field d along the arch axis. This study aims to enhance the understanding of temperature fields in reinforced concrete (RC) arch bridges with diverse arch ring structural configurations during their construction phases. A comprehensive investigation into the three-dimensional distribution pattern of solar-induced temperature fields within arch ribs during the construction of RC ribbed arch bridges was conducted. A field test specifically measuring the temperature distribution across arch rib cross-sections was conducted on-site, involving an RC arch bridge constructed using the cable-stayed cantilever cast in situ method. Analyzing the monitored on-site temperature data revealed the distribution characteristics of temperature fields at the arch foot cross-section under solar radiation. By comparing these findings with international standards, a vertical temperature gradient fitting model for arch rib cross-sections under solar radiation was formulated. Drawing upon meteorological records and solar radiation principles, an adaptive numerical simulation finite element model was developed to depict the temperature field within an arch rib section. This model was rigorously verified. Subsequently, a comprehensive analysis of the three-dimensional temperature field of the arch rib under solar radiation was performed. Additionally, a three-dimensional temperature gradient fitting model was proposed, accounting for the longitudinal inclination of the bridge. [ABSTRACT FROM AUTHOR]

A temperature gradient was induced in 316 stable austenitic stainless‐steel tension specimens, and the strain and temperature evolution during tensile deformation was monitored using optical and infrared cameras. The combination of global load with full‐field strain and temperature provided local information on the thermomechanical state of the investigated material. The deformation did not fully concentrate on the hotter portion of the specimen, but instead, the hottest portion strain hardened enough so that the colder portions of the specimen also experienced plastic deformation. Evidently, heat release occurred with plastic deformation and altered the initial temperature gradient as deformation progressed. The Taylor–Quinney coefficient was computed in integral and differential forms, and both are presented as a function of temperature and strain. The Johnson–Cook plasticity model was calibrated through an inverse method procedure in which only five tests were used, and the obtained temperature and strain rate dependencies of the model were comparable to those found in the literature for the same material. A local analysis was done to quantify the impact of adiabatic heating on the mechanical behaviour of the material. [ABSTRACT FROM AUTHOR]

The temperature dependences of the thermoelectromotive force of chromium mono and disilicides in the temperature range 200℃÷+600℃ have been studied. For chromium disilicide, the dependence of the thermopower coefficient (α) on temperature (T) has three sections. Chromium monosilicide is characterized by a smooth increase in thermopower with increasing temperatures up to 200℃, and then its constancy. It was revealed that silicides rich in chromium atoms have lower thermopower values than silicides rich in silicon. The maximum thermo-EMF values of 110 μV/K and 190 μV/K were observed for chromium mono- and disilicides, respectively. It was revealed that for chromium silicides the dependence of the dimensionless parameter Q = Z∙T on temperature is linear. The possibility of predicting the technology of synthesis of semiconductor material with optimal thermoelectric properties using the dependence of thermopower on conductivity and the parameter Q on temperature is shown. [ABSTRACT FROM AUTHOR]

This study sought to investigate the invasive mechanism of Myriophyllum aquaticum by subjecting it to simulation experiments in varying water temperatures ranging from 0 °C to 30 °C. The results showed that water temperature considerably affected both the growth and reproduction of M. aquaticum. The optimal temperature range for the growth of M. aquaticum was 25‒30 °C. Although the growth of M. aquaticum was inhibited at temperatures between 0‒5 °C, this did not result in mortality. The stem nodes, branches, and diameter reached maximum values over a temperature range of 20‒25 °C. High-temperature stress at 30 °C led to a gradual decrease or disappearance of branches. Compared to the 0 °C, 5 °C, and 30 °C treatment groups, a temperature of 20 °C led to biomass accumulation and significantly higher values. M. aquaticum’s physiological activities were affected by temperature. Except for 10 °C and 15 °C, the catalase activity varied among different water temperatures. M. aquaticum catalase activity was maximal at 5 °C and minimal at 25 °C. Conversely, the synthesis of photosynthetic pigments was highest at 10 °C and 15 °C. The plant’s optimal temperature for growth was between 20 °C and 25 °C. When the temperature was <10 °C, M. aquaticum adapted to the water temperature’s potential damage. This plant has a notable ability to tolerate various temperatures. [ABSTRACT FROM AUTHOR]

Water vapor adsorption on soil, a crucial non-rainfall water resource in arid regions, warrants further experimental investigation, particularly on two typical land surfaces: bare soil and gravel. This study examined the formation characteristics and influencing factors of vapor adsorption in an arid region of Northwestern China. Observations and analyses were conducted on adsorption and evaporation measurements taken by two small weighing lysimeters (SLSs); soil temperature at a depth of 5 cm; surface temperature; relative humidity; and air temperature at a height of 30 cm above the ground from 2019 to 2020. The adsorbed water in this area was more abundant at night and less abundant during the day, with a stable nightly adsorption rate of 0.013 mm/h. Adsorption was more frequent in spring and winter (from January to June and November to December), accounting for about 90% of the total annual adsorption. In 2019 and 2020, the ratio values of adsorption to evaporation were 0.16 and 0.10 for bare soil, and 0.10 and 0.12 for gravel, respectively. Adsorption was more likely to occur when the soil moisture content was less than 13%; the highest adsorption frequency was close to 20% when the RH was between 75 and 95%; low soil temperatures were more conducive to the occurrence of adsorption. The effect of temperature differences (Ta−Ts) on adsorption was stronger than that of relative humidity. The adsorption frequency generally showed a bimodal change with increasing temperature difference, but the effect of temperature differences was less effective for gravel than bare soil. When the relative humidity was high and the temperature difference was weakly positive, the maximum adsorption intensity could reach 0.18 mm/h. [ABSTRACT FROM AUTHOR]

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The use of polymers for water storage or distribution is closely monitored, especially with regard to the possible contamination with substances coming from the material's surfaces. Different standards are practiced across countries according to type of applied materials and such test methods are prevalently based on constant temperature conditions. However, these polymers systems could be located in diverse environment which does not necessarily provide constant conditions. Experimental findings show that exposure of liquid inside polymeric materials to specific temperature gradients, and consequently to emerging organized flows, can result in an accelerated leaching of undesirable substances from the solid surface. In presented work model steady-state and organized flow conditions are used to compare release of contaminates from polyethylene by measuring of surface tension, UV–Vis spectroscopy, FTIR, scanning electron microscopy and elemental analysis of polymer surfaces and water leachates. The pilot study shows that convective flow generated via temperature gradient significantly affects contaminant release in comparison to a steady state and mixing flow conditions.

To further study adiabatic parameters distortion, the adiabatic decomposition of 2,4-DNT, 20%DTBP, and 45%Glucose was systematically analyzed using thermal analysis calorimetry and numerical simulation methods. The study revealed the variation laws and influence mechanisms of the temperature gradient effects and thermal inertia in adiabatic systems. A numerical model for decomposition in a closed adiabatic system was developed by integrating the apparent kinetics into the CFD code. The results show that the temperature gradient effects during adiabatic decomposition initially increase and then decrease until reaching zero. The temperature gradient effects become more pronounced as the exothermic characteristics of substances increase. They are the most significant at the peak self-heating rate, with gradients of 182.4 °C·cm−1, 21.6 °C·cm−1, and 0.78 °C·cm−1, respectively. Specific data segments for adiabatic analysis should maintain α values below 0.138 for 2,4-DNT, 0.484 for 20%DTBP, and should utilize complete 100 % adiabatic data for 45%Glucose, aiming to mitigate potential distortion in adiabatic parameters. Furthermore, Фeff varies with the reaction, initially increasing and then decreasing in deviation from the theoretical value, with peak deviations of 60 %, 20 %, and 0.3 % for three substances, respectively. These findings lay the foundation for further optimizing the temperature gradient effects and establishing a dynamic Фeff correction model.

Abstract There is a global need for clean and renewable energy sources. This study investigated thermoelectric generators (TEGs) as a possible method for harvesting solar power. The TEG prototype tested here consisted of two equally sized pieces of roof sheeting, with one side exposed to a light source and the other side shaded. Experiments were carried out with the necessary testing components to investigate the effects that two variables have on the amount of power generated: first, the colour of metal inverted box rib (IBR) sheeting and, second, the ideal electrical arrangement for scalability of Peltier tiles for maximum power output. Black-coated sheets generated maximum power (Pmax) output of the TEGs. The TEGs in series configuration generated the highest Pmax when located closest to the light source. The conclusion from the experiment is that TEGs are a potential method of harvesting solar energy on IBR sheeting, specifically in a vertical position. However, applications of different orientations and geographical locations require further investigation, including into the use of TEGs on IBR sheeting for harvesting solar energy on a larger scale.

Massive high-strength concrete generates significant hydration heat during casting, which indirectly influences the risk of structural cracking by affecting the internal temperature gradient distribution. This paper investigated the effect of layered pouring methods on internal temperature gradients in massive concrete using the precast bent caps of a Shanghai bridge project as a case study. The temperature-time development patterns of each poured layer were studied through three sets of physical experiments. Temperature gradient distribution functions were established to specify the spatial temperature distribution trends of each layer. The interconnectedness between the spatial temperature distributions of adjacent poured layers was explored based on the established distribution functions. Targeted anticracking suggestions for layered poured concrete were provided based on these correlations. Additionally, a novel temperature control measure for managing hydration heat was proposed. The feasibility of this measure was verified through practical experiments. Moreover, corresponding finite element models were established to investigate the influence of parameters such as structural lead, outer wall pipe radius, and cooling water flow rate on the internal temperature field of concrete. The hydration heat-time patterns of the poured layers all showed a skewed single-peak distribution. The hydration heat of odd- and even-numbered layers exhibited different Gaussian distribution patterns in the lateral direction; the correlation between the spatial temperature distributions of adjacent layers could be quantified by the ratio of the standardized variance of the Gaussian distribution function of temperature for each corresponding layer. Implementing temperature control measures at specific reasonable positions and using a natural logarithmic function to calculate the design limits of structural dimensions could effectively prevent structural cracking. The newly proposed hydration heat control measure improved the temperature gradient distribution within the concrete. Reducing the structural lead, increasing the outer wall pipe radius, and increasing the cooling water flow rate all resulted in a decrease in the peak temperature inside the concrete. Finally, a structural lead of 0.4 was recommended for actual construction projects, for which the outer wall pipe radius should not exceed 30 mm.

The bentonite material is currently used in a variety of applications ranging from hydraulic barriers and waste-buffer protection to other special uses in industry and underground disposal of high-level nuclear waste. In the deep geological repository for high-level radioactive waste, the clay acting as a buffer material between the host rock and the canister is subjected to thermal load, which could impact its geotechnical properties. Thus this study is aimed at investigating the swell and compressibility of bentonite subjected to heating at 200 °C, 400 °C, and 600 °C. The impact of heating on the index properties, the swell and compression and hydraulic conductivity is explored. The change in temperature due to weather fluctuations was found to have a minor effect on physical behavior, but this effect is found to be significant when the temperature is raised to high levels in the order of 200 °C–600 °C (Celsius). The rate at which swell and hydraulic conductivity is developed is presented in this study. The result indicated an elimination of the swellable clay minerals effect in the bentonite clay upon exposure to a temperature of 600 °C. This study introduces useful information and data for modeling the behavior of bentonite when subjected to elevated temperatures for use in application for deep geological repository for high-level radioactive waste storage and other applications.