Objective The use of lasers has been an important part of urology in the treatment of stone and prostate disease.The thermal effects of lasers in lithotripsy have been a subject of debate over the years.The objective ...Objective The use of lasers has been an important part of urology in the treatment of stone and prostate disease.The thermal effects of lasers in lithotripsy have been a subject of debate over the years.The objective of this review was to assess the current state of knowledge available on the thermal effects of lasers in lithotripsy,as well as explore any new areas where studies are needed.Methods In August 2022,a keyword search on Google Scholar,PubMed,and Scopus for all papers containing the phrases“thermal effects”AND“laser”AND“lithotripsy”AND“urology”was done followed by citation jumping to other studies pertaining to the topic and 35 relevant papers were included in our study.The data from relevant papers were segregated into five groups according to the factor studied and type of study,and tables were created for a comparison of data.Results Temperature above the threshold of 43℃ was reached only when the power was>40 W and when there was adequate irrigation(at least 15–30 mL/min).Shorter lasing time divided by lithotripsy time or operator duty cycles less than 70%also resulted in a smaller temperature rise.Conclusion At least eight factors modify the thermal effects of lasers,and most importantly,the use of chilled irrigation at higher perfusion rates,lower power settings of<40 W,and with a shorter operator duty cycle will help to prevent thermal injuries from occurring.Stones impacted in the ureter or pelvi-ureteric junction further increase the probability of thermal injuries during laser firing.展开更多
During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configura...During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path.To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths,this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method.This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis.A simplified analytical model of the flow field region in complex internal channels was established,and regions with similar thermal blooming effect were divided within this model.Based on the calculated optical path differences within these regions,numerical simulations of phase distortion caused by thermal blooming were conducted.The calculated result were compared with those obtained using the existing methods.The findings reveal that for complex optical paths,the discrepancy between the two approaches is less than 3.6%,with similar phase distortion patterns observed.For L-type units,this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation.This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions.The results show that phase distortion varies with changes in the direction of gravity,and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis.Compared to the existing methods,this approach offers greater flexibility,obviates the need for complex custom analysis programming.The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel.This is especially useful during the engineering design.These results also provide crucial references for developing strategies to suppress thermal blooming effect.展开更多
A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite ...A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite element analysis was employed to model the delamination process,incorporating a contact cohesive zone model.This model couples the traction⁃separation law,the contact law,and the Coulomb friction law simultaneously.The thermomechanical analysis in this study is performed using a sequentially coupled approach,implemented with the finite element software ABAQUS.The findings underscore the importance of this study.展开更多
The stimulation of shale reservoirs frequently involves significant shear failure,which is crucial for creating fracture networks and enhancing permeability to boost production.As the depth of extraction increases,the...The stimulation of shale reservoirs frequently involves significant shear failure,which is crucial for creating fracture networks and enhancing permeability to boost production.As the depth of extraction increases,the impact of elevated temperatures on the anisotropic shear strength and failure mechanisms of shale becomes pronounced,yet there is a notable lack of relevant research.This study conducts,for the first time,direct shear experiment on shales at four different temperatures and seven bedding angles.By employing acoustic emission(AE)and digital image correlation(DIC)techniques,the evolution of damage and the mechanism of crack propagation under anisotropic direct shearing at varying temperatures is revealed.The results indicate that both shear displacement and strength of shale increase with temperature across different bedding angles.Additionally,shale demonstrates distinct brittle failure characteristics under various conditions during direct shearing tests.The types of anisotropic shear failure observed under the influence of temperature include central shearing fracture,central shearing with secondary fracture,and deflected slip along the bedding.Moreover,the temperature effect enhances shear-induced crack propagation along bedding planes.Shear failure in shale predominantly occurs during higher loading stages,which coincide with a substantial amount of AE signals.Finally,the introduction of the anisotropy index and temperature sensitivity coefficient further elucidates the interaction mechanism between thermal effects and anisotropy.This study offers a novel methodology to explore the anisotropic shear failure behavior of shale under elevated temperatures,and also provides crucial theoretical and experimental insights into shear failure behavior relevant to practical shale reservoir stimulation.展开更多
The exploitation of organic-inorganic hybrid perovskites(OIHPs) as active layer materials for typical sandwich-structured resistive memories has attracted widespread interest due to the property of low power consumpti...The exploitation of organic-inorganic hybrid perovskites(OIHPs) as active layer materials for typical sandwich-structured resistive memories has attracted widespread interest due to the property of low power consumption and fast switching. However, the inherent thermal instability of perovskites limits the application of OIHPs-based resistive memories under extreme conditions, while the infiuence of thermal effects on their resistance change characteristics remains unclear. Herein, a novel 2D <100>-oriented high-temperature resistant OIHP [(BIZ-H)_(2)(PbBr_(4))]n(BIZ = benzimidazole) is prepared as an active layer material to fabricate FTO/[(BIZ-H)_(2)(PbBr_(4))]n/Ag resistive memory with excellent thermal reproducibility and stability up to 120℃. The increase in temperature leads to a decrease in the PbBr_(6) octahedral distortion in the crystal structure, an increase in hydrogen bonding between the(BIZ-H)+cation and the(PbBr_(4))_(n)^(2n-)layer, and a shortening of the spacing of the inorganic layers, which is found to result in the creation and predominance of thermally activated traps with increasing temperature. This work provides a new direction for the next generation of OIHPs-based resistive memories with high-temperature tolerance.展开更多
The monument thermal effect(MTE)displacements could result in periodical signals with several mil-limeters magnitudes in the vertical and horizontal GPS position time series.However,the interaction ofvarious origins o...The monument thermal effect(MTE)displacements could result in periodical signals with several mil-limeters magnitudes in the vertical and horizontal GPS position time series.However,the interaction ofvarious origins of periodic signals in GPS observations makes it difficult to isolate the millimeter-levelMTE displacement from other signals and noises.In this study,to assess the diurnal and semidiurnalsignals induced by MTE,we processed 12 very short GPS baselines(VSGB)with length<150 m.Themonument pairs for each baseline differ in their heights,horizontal structure,or base foundations.Meanwhile,two zero-baselines were also processed as the control group.Results showed that the sea-sonal signals observed in VSGB time series in the horizontal and vertical directions,were mainly inducedby seasonal MTE.Time-varying diurnal and semidiurnal signals with amplitude up to 4 mm wereobserved in the vertical direction for baselines with monument height difference(MHD)larger than10 m.Horizontal diurnal signal with an amplitude of about 2 mm was also detected for baselines withnon-axisymmetric monument structure.The orientation of the detected horizontal displacement wascoherent with the direction of daily temperature variation(DTV)driven by direct solar radiation,whichindicates that the diurnal and semidiurnal signals are likely induced by MTE.The observed high-frequency MTE displacements,if not well modeled and removed,may propagate into spurious long-term signals and bias the velocity estimation in the daily GPS time series.展开更多
Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting o...Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting of twisted fibers as temperature increases due to greater radial than axial thermal expansion,is crucial to the actuation performance of these artificial muscles.This study explores the thermal torsion effect of polymer muscles made of twisted Nylon 6 fibers in experimental and theoretical aspects,focusing on the interplay between material properties and temperature.It is revealed that the thermal torsion effect enhances the actuation performance of the twisted polymer actuator while the thermal softening effect diminishes it.A thermal-mechanical model incorporating both the thermal torsion effect and thermal softening effect is used to predict the recovered torque of the twisted polymer actuators.An optimal bias angle and operating temperature are identified to maximize the recovered torque.Analysis of strain and stress distributions in the cross-section of the twisted polymer fiber shows that the outer layers of the fiber predominantly contribute to the torsional actuation.This work aids in the precise control and structural optimization of the thermally-activated twisted polymer actuators.展开更多
The present study investigates the influence of thermal dispersion on the natural convective flow of a Casson fluid along an inclined plate embedded in a non-Darcy porous medium.The governing equations,representing mo...The present study investigates the influence of thermal dispersion on the natural convective flow of a Casson fluid along an inclined plate embedded in a non-Darcy porous medium.The governing equations,representing momentum and energy conservations,are transformed into non-dimensional form using similarity transformations.To address the complexity of the resulting equations,a bivariate spectral quasilinearisation method is employed.The effects of relevant parameters—including thermal dispersion,Casson parameter,Biot number,Forchheimer number,inclination angle and nonlinear thermal convection parameter—are thoroughly examined.The results show that the drag coefficient and heat transfer rate increase with the nonlinear thermal convection parameter,Casson parameter and Biot number.In contrast,they decrease as the Forchheimer number and inclination angle increase.The velocity near the surface of the inclined plate increases with the Biot number,Casson parameter and nonlinear thermal convection parameter.However,it decreases farther from the plate.Additionally,the temperature of the Casson fluid increases with most parameters,except the Casson and nonlinear thermal convection parameters.展开更多
As the size of transistors shrinks and power density increases,thermal simulation has become an indispensable part of the device design procedure.However,existing works for advanced technology transistors use simplifi...As the size of transistors shrinks and power density increases,thermal simulation has become an indispensable part of the device design procedure.However,existing works for advanced technology transistors use simplified empirical models to calculate effective thermal conductivity in the simulations.In this work,we present a dataset of size-dependent effective thermal conductivity with electron and phonon properties extracted from ab initio computations.Absolute in-plane and cross-plane thermal conductivity data of eight semiconducting materials(Si,Ge,GaN,AlN,4H-SiC,GaAs,InAs,BAs)and four metallic materials(Al,W,TiN,Ti)with the characteristic length ranging from 5 nm to 50 nm have been provided.Besides the absolute value,normalized effective thermal conductivity is also given,in case it needs to be used with updated bulk thermal conductivity in the future.展开更多
The case study is about obtaining the flow rate and saturation temperature of steam that makes it possible to heat a solution of water and ammonia nitrate (<i>ANSOL</i>) in a shell and helical coil tube he...The case study is about obtaining the flow rate and saturation temperature of steam that makes it possible to heat a solution of water and ammonia nitrate (<i>ANSOL</i>) in a shell and helical coil tube heat exchanger, within a time interval, without that the crystallization of the <i>ANSOL</i> solution occurs. The desired production per batch of the solution is 5750 kg in 80 minutes. The analysis uses the concepts of efficiency and effectiveness to determine the heat transfer rate and temperature profiles that satisfy the imposed condition within a certain degree of safety and with the lowest possible cost in steam generation. Intermediate quantities necessary to reach the objective are the Reynolds number, Nusselt number, and global heat transfer coefficient for the shell and helical coil tube heat exchanger. Initially, the water is heated for a specified period and, subsequently, the ammonium nitrate is added to a given flow in a fixed mass flow rate.展开更多
The work’s objective is to analyze the influence of the saturation temperature of the R134a refrigerant on the thermal performance of a shell and tube type condenser, with water and aluminum oxide (Al<sub>2<...The work’s objective is to analyze the influence of the saturation temperature of the R134a refrigerant on the thermal performance of a shell and tube type condenser, with water and aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) nanoparticles flowing into the tube. For analysis, the heat exchanger is subdivided into three regions: subcooled liquid, saturated steam, and superheated steam. The shell and tube heat exchanger assumed as the basis for the study has 36 tubes, with rows of 4 tubes in line and three passes into the tube in each region. The parameters used to analyze the performance are efficiency and effectiveness, through variations of quantities such as saturation temperature, the nanofluid’s mass flow rate, fraction in the nanoparticles’ volume, and the number of passes in the tube in each region of the heat exchanger. The obtained results demonstrate that the efficiency is relatively high in all the analyzed situations. In each saturation temperature, the effectiveness can be increased by introducing fractions of nanoparticles in the water or increasing the number of passes in the tube.展开更多
The concentrically layered thermal cloaks with isotropic materials could realize the equivalent thermal cloaking effect with Pendry＇s cloak, while the effectiveness is scarcely investigated quantitatively. Here we ex...The concentrically layered thermal cloaks with isotropic materials could realize the equivalent thermal cloaking effect with Pendry＇s cloak, while the effectiveness is scarcely investigated quantitatively. Here we examine the cloaking effectiveness quantitatively by evaluating the standard deviation of the temperature difference between the simulated plane with the layered thermal cloak and Pendry＇s thermal cloak. The design rules for the isotropic materials in terms of thermal conductivity and layer thickness are presented. The present method could quan- titatively evaluate the cloaking effectiveness, and could open avenues for analyzing the cloaking effect, detecting the （anti-） cloaks, etc.展开更多
Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temper...Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.展开更多
The research on the thermal property of the hydrate has recently made great progress,including the understanding of hydrate thermal conductivity and effective thermal conductivity(ETC)of hydratebearing sediment.The th...The research on the thermal property of the hydrate has recently made great progress,including the understanding of hydrate thermal conductivity and effective thermal conductivity(ETC)of hydratebearing sediment.The thermal conductivity of hydrate is of great significance for the hydrate-related field,such as the natural gas hydrate exploitation and prevention of the hydrate plugging in oil or gas pipelines.In order to obtain a comprehensive understanding of the research progress of the hydrate thermal conductivity and the ETC of hydrate-bearing sediment,the literature on the studies of the thermal conductivity of hydrate and the ETC of hydrate-bearing sediment were summarized and reviewed in this study.Firstly,experimental studies of the reported measured values and the temperature dependence of the thermal conductivity of hydrate were discussed and reviewed.Secondly,the studies of the experimental measurements of the ETC of hydrate-bearing sediment and the effects of temperature,porosity,hydrate saturation,water saturation,thermal conductivity of porous medium,phase change,and other factors on the ETC of hydrate-bearing sediment were discussed and reviewed.Thirdly,the research progress of modeling on the ETC of the hydrate-bearing sediment was reviewed.The thermal conductivity determines the heat transfer capacity of the hydrate reservoir and directly affects the hydrate exploitation efficiency.Future efforts need to be devoted to obtain experimental data of the ETC of hydrate reservoirs and establish models to accurately predict the ETC of hydrate-bearing sediment.展开更多
Dielectric barrier discharge(DBD)plasma excited by a high-frequency alternating-current(AC)power supply is widely employed for the degradation of volatile organic compounds(VOCs).However,the thermal effect generated d...Dielectric barrier discharge(DBD)plasma excited by a high-frequency alternating-current(AC)power supply is widely employed for the degradation of volatile organic compounds(VOCs).However,the thermal effect generated during the discharge process leads to energy waste and low energy utilization efficiency.In this work,an innovative DBD thermally-conducted catalysis(DBD-TCC)system,integrating high-frequency AC-DBD plasma and its generated thermal effects to activate the Co/SBA-15 catalyst,was employed for toluene removal.Specifically,Co/SBA-15 catalysts are closely positioned to the ground electrode of the plasma zone and can be heated and activated by the thermal effect when the voltage exceeds 10 k V.At12.4 k V,the temperature in the catalyst zone reached 261℃ in the DBD-TCC system,resulting in an increase in toluene degradation efficiency of 17%,CO_(2)selectivity of 21.2%,and energy efficiency of 27%,respectively,compared to the DBD system alone.In contrast,the DBD thermally-unconducted catalysis(DBD-TUC)system fails to enhance toluene degradation due to insufficient heat absorption and catalytic activation,highlighting the crucial role of AC-DBD generated heat in the activation of the catalyst.Furthermore,the degradation pathway and mechanism of toluene in the DBD-TCC system were hypothesized.This work is expected to provide an energy-efficient approach for high-frequency AC-DBD plasma removal of VOCs.展开更多
Aerogel nanoporous materials possess high porosity, high specific surface area, and extremely low density due to their unique nanoscale network structure. Moreover, their effective thermal conductivity is very low, ma...Aerogel nanoporous materials possess high porosity, high specific surface area, and extremely low density due to their unique nanoscale network structure. Moreover, their effective thermal conductivity is very low, making them a new type of lightweight and highly efficient nanoscale super-insulating material. However, prediction of their effective thermal conductivity is challenging due to their uneven pore size distribution. To investigate the internal heat transfer mechanism of aerogel nanoporous materials, this study constructed a cross-aligned and cubic pore model(CACPM) based on the actual pore arrangement of SiO_(2) aerogel. Based on the established CACPM, the effective thermal conductivity expression for the aerogel was derived by simultaneously considering gas-phase heat conduction, solid-phase heat conduction, and radiative heat transfer. The derived expression was then compared with available experimental data and the Wei structure model. The results indicate that, according to the model established in this study for the derived thermal conductivity formula of silica aerogel, for powdery silica aerogel under the conditions of T = 298 K, a_(2)= 0.85, D_(1)= 90 μm, ρ = 128 kg/m^(3), within the pressure range of 0–10^(5)Pa, the average deviation between the calculated values and experimental values is 10.51%. In the pressure range of 10^(3)–10^(4)Pa, the deviation between calculated values and experimental values is within 4%. Under these conditions, the model has certain reference value in engineering verification. This study also makes a certain contribution to the research of aerogel thermal conductivity heat transfer models and calculation formulae.展开更多
The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package...The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package.Our study revealed significant spin-splitting within the Janus VSTe monolayer,which induced spin currents under a temperature gradient across the device.By applying a 1%tensile strain,the Janus VSTe monolayer exhibited a perfect thermal spin filtering effect(SFE),with the spin-up current nearly suppressed to zero.Both the unstrained and strained Janus VSTe monolayers demonstrated excellent spin caloritronic properties,with spin figures of merit of 10.915 and 8.432 at an average temperature of 100 K,respectively.Notably,these properties were found to be sensitive to temperature,performing optimally at lower temperatures.These results suggest a promising avenue for designing spin caloritronic devices aimed at efficient waste heat recovery.展开更多
Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature dis...Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.展开更多
A DC to 5GHz series MEMS switch is designed and fabricated for wireless communication applications,and thermal effect and power handling of the series switch are discussed.The switch is made on glass substrate,and gol...A DC to 5GHz series MEMS switch is designed and fabricated for wireless communication applications,and thermal effect and power handling of the series switch are discussed.The switch is made on glass substrate,and gold platinum contact is used to get a stable and little insert loss.From DC to 5GHz,0 6dB insertion loss,30dB isolation,and 30μs delay are demonstrated.Thermal effect of the switch is tested in 85℃ and -55℃ atmosphere separately.From DC to 4GHz,the insert loss of the switch increases 0 2dB in 85℃ and 0 4dB in -55℃,while the isolation holds the same value as that in room temperature.To measure the power handling capability of the switch,we applied a continuous RF power increasing from 10dBm to 35 1dBm with the step of 1 0dBm across the switch at 4GHz.The switch keeps working and shows a decrease of the insert loss for 0 1～0 6dB.The maximum continuous power handling (35 1dBm,about 3 24W) is higer than the reported value of shunt switch (about 420mW),which implies series switches have much better power handling capability.展开更多
This work describes the discharge characteristics and acetone degradation with plasma under different electric fields based on a coaxial cylindrical dielectric barrier discharge(DBD)device energized by pulsed power.It...This work describes the discharge characteristics and acetone degradation with plasma under different electric fields based on a coaxial cylindrical dielectric barrier discharge(DBD)device energized by pulsed power.It is found that the segmented electrodes with appropriate spacing in coaxial cylindrical DBD are beneficial to the plasma ionization.In this work,the plasma distribution,discharge thermal effect,ionization of reactive species,and acetone degradation performance in coaxial cylindrical DBD with different segmented electrodes are systematically investigated.The experimental results show that segmented electrodes with a certain distance can cause additional ionization in the non-electrode-covered region between adjacent electrodes,thus enlarging the plasma region compared with a single electrode with equivalent total electrode length.The additional ionization involved the inner volume discharge between the quartz tubes and the outer surface discharge along the surface of the external quartz tube.The spatial distributions of the inner volume discharge and external surface discharge were predominantly governed by the radial and axial components of the inter-electrode electric field,respectively.The external surface discharge exhibited significant suppression when the electrode spacing was<1.5 mm,and it reached its maximum length at 3 mm spacing.When the electrode distance increased to 7-9 mm,a weak ionizing region appeared in the middle of the adjacent electrodes,which could be attributed to the gradual attenuation of the radial component with the increasing electrode spacing.A higher thermal effect and better oxidation of acetone to CO_(x)(CO and CO_(2))were achieved with the segmented electrode;the dual-segment configuration(3 mm per electrode)achieved a reactor temperature of 63.4℃,representing a 10℃enhancement over comparable single-electrode systems.Similarly,the CO_(2)and CO concentration reached 328.8 mg/m3and 105.7 mg/m3,respectively,in two 3 mm long segmented electrodes,which was an increase of 12.2%and 25.6%,respectively,compared with the single electrode.Notably,considering the equivalent ionization of the inner discharge with different electrodes,the enhanced thermal effects and CO_(x)conversion efficiency directly correlate with the expanded plasma zone induced by electrode segmentation.This work provides critical insights into optimizing electrode configurations for efficient plasma-assisted volatile organic compound degradation systems.展开更多
文摘Objective The use of lasers has been an important part of urology in the treatment of stone and prostate disease.The thermal effects of lasers in lithotripsy have been a subject of debate over the years.The objective of this review was to assess the current state of knowledge available on the thermal effects of lasers in lithotripsy,as well as explore any new areas where studies are needed.Methods In August 2022,a keyword search on Google Scholar,PubMed,and Scopus for all papers containing the phrases“thermal effects”AND“laser”AND“lithotripsy”AND“urology”was done followed by citation jumping to other studies pertaining to the topic and 35 relevant papers were included in our study.The data from relevant papers were segregated into five groups according to the factor studied and type of study,and tables were created for a comparison of data.Results Temperature above the threshold of 43℃ was reached only when the power was>40 W and when there was adequate irrigation(at least 15–30 mL/min).Shorter lasing time divided by lithotripsy time or operator duty cycles less than 70%also resulted in a smaller temperature rise.Conclusion At least eight factors modify the thermal effects of lasers,and most importantly,the use of chilled irrigation at higher perfusion rates,lower power settings of<40 W,and with a shorter operator duty cycle will help to prevent thermal injuries from occurring.Stones impacted in the ureter or pelvi-ureteric junction further increase the probability of thermal injuries during laser firing.
文摘During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path.To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths,this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method.This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis.A simplified analytical model of the flow field region in complex internal channels was established,and regions with similar thermal blooming effect were divided within this model.Based on the calculated optical path differences within these regions,numerical simulations of phase distortion caused by thermal blooming were conducted.The calculated result were compared with those obtained using the existing methods.The findings reveal that for complex optical paths,the discrepancy between the two approaches is less than 3.6%,with similar phase distortion patterns observed.For L-type units,this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation.This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions.The results show that phase distortion varies with changes in the direction of gravity,and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis.Compared to the existing methods,this approach offers greater flexibility,obviates the need for complex custom analysis programming.The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel.This is especially useful during the engineering design.These results also provide crucial references for developing strategies to suppress thermal blooming effect.
文摘A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite element analysis was employed to model the delamination process,incorporating a contact cohesive zone model.This model couples the traction⁃separation law,the contact law,and the Coulomb friction law simultaneously.The thermomechanical analysis in this study is performed using a sequentially coupled approach,implemented with the finite element software ABAQUS.The findings underscore the importance of this study.
基金supported by the National Natural Science Fund of China (Grant Nos.U22A20166 and 52374131)the Shenzhen Science and Technology Program (Grant No.JCYJ20220531102012028)the Young Elite Scientists Sponsorship Program by CAST.
文摘The stimulation of shale reservoirs frequently involves significant shear failure,which is crucial for creating fracture networks and enhancing permeability to boost production.As the depth of extraction increases,the impact of elevated temperatures on the anisotropic shear strength and failure mechanisms of shale becomes pronounced,yet there is a notable lack of relevant research.This study conducts,for the first time,direct shear experiment on shales at four different temperatures and seven bedding angles.By employing acoustic emission(AE)and digital image correlation(DIC)techniques,the evolution of damage and the mechanism of crack propagation under anisotropic direct shearing at varying temperatures is revealed.The results indicate that both shear displacement and strength of shale increase with temperature across different bedding angles.Additionally,shale demonstrates distinct brittle failure characteristics under various conditions during direct shearing tests.The types of anisotropic shear failure observed under the influence of temperature include central shearing fracture,central shearing with secondary fracture,and deflected slip along the bedding.Moreover,the temperature effect enhances shear-induced crack propagation along bedding planes.Shear failure in shale predominantly occurs during higher loading stages,which coincide with a substantial amount of AE signals.Finally,the introduction of the anisotropy index and temperature sensitivity coefficient further elucidates the interaction mechanism between thermal effects and anisotropy.This study offers a novel methodology to explore the anisotropic shear failure behavior of shale under elevated temperatures,and also provides crucial theoretical and experimental insights into shear failure behavior relevant to practical shale reservoir stimulation.
基金financially supported by the Ph.D. start-up funds of Jiangxi Science and Technology Normal University (Nos. 2023BSQD11, 2023BSQD13)Jiangxi Province Key Laboratory of Organic Functional Molecules (No. 2024SSY05141)。
文摘The exploitation of organic-inorganic hybrid perovskites(OIHPs) as active layer materials for typical sandwich-structured resistive memories has attracted widespread interest due to the property of low power consumption and fast switching. However, the inherent thermal instability of perovskites limits the application of OIHPs-based resistive memories under extreme conditions, while the infiuence of thermal effects on their resistance change characteristics remains unclear. Herein, a novel 2D <100>-oriented high-temperature resistant OIHP [(BIZ-H)_(2)(PbBr_(4))]n(BIZ = benzimidazole) is prepared as an active layer material to fabricate FTO/[(BIZ-H)_(2)(PbBr_(4))]n/Ag resistive memory with excellent thermal reproducibility and stability up to 120℃. The increase in temperature leads to a decrease in the PbBr_(6) octahedral distortion in the crystal structure, an increase in hydrogen bonding between the(BIZ-H)+cation and the(PbBr_(4))_(n)^(2n-)layer, and a shortening of the spacing of the inorganic layers, which is found to result in the creation and predominance of thermally activated traps with increasing temperature. This work provides a new direction for the next generation of OIHPs-based resistive memories with high-temperature tolerance.
基金funded by the Independent Innovation Project of Changjiang Institute of Survey,Planning,Design and Research Corporation (CX2020Z32)supported by the National Natural Science Foundation of China (Grant Numbers42204006 and 42104028)the Open Fund of Hubei Luojia Laboratory (Grant Numbers 230100020 and 230100019)
文摘The monument thermal effect(MTE)displacements could result in periodical signals with several mil-limeters magnitudes in the vertical and horizontal GPS position time series.However,the interaction ofvarious origins of periodic signals in GPS observations makes it difficult to isolate the millimeter-levelMTE displacement from other signals and noises.In this study,to assess the diurnal and semidiurnalsignals induced by MTE,we processed 12 very short GPS baselines(VSGB)with length<150 m.Themonument pairs for each baseline differ in their heights,horizontal structure,or base foundations.Meanwhile,two zero-baselines were also processed as the control group.Results showed that the sea-sonal signals observed in VSGB time series in the horizontal and vertical directions,were mainly inducedby seasonal MTE.Time-varying diurnal and semidiurnal signals with amplitude up to 4 mm wereobserved in the vertical direction for baselines with monument height difference(MHD)larger than10 m.Horizontal diurnal signal with an amplitude of about 2 mm was also detected for baselines withnon-axisymmetric monument structure.The orientation of the detected horizontal displacement wascoherent with the direction of daily temperature variation(DTV)driven by direct solar radiation,whichindicates that the diurnal and semidiurnal signals are likely induced by MTE.The observed high-frequency MTE displacements,if not well modeled and removed,may propagate into spurious long-term signals and bias the velocity estimation in the daily GPS time series.
基金support from the National Natural Science Foundation of China(Grant No.12272146)the Fundamental Research Funds for the Central Universities(Grant No.2024BRA009)the Young Top-notch Talent Cultivation Program of Hubei Province,is appreciated.
文摘Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting of twisted fibers as temperature increases due to greater radial than axial thermal expansion,is crucial to the actuation performance of these artificial muscles.This study explores the thermal torsion effect of polymer muscles made of twisted Nylon 6 fibers in experimental and theoretical aspects,focusing on the interplay between material properties and temperature.It is revealed that the thermal torsion effect enhances the actuation performance of the twisted polymer actuator while the thermal softening effect diminishes it.A thermal-mechanical model incorporating both the thermal torsion effect and thermal softening effect is used to predict the recovered torque of the twisted polymer actuators.An optimal bias angle and operating temperature are identified to maximize the recovered torque.Analysis of strain and stress distributions in the cross-section of the twisted polymer fiber shows that the outer layers of the fiber predominantly contribute to the torsional actuation.This work aids in the precise control and structural optimization of the thermally-activated twisted polymer actuators.
文摘The present study investigates the influence of thermal dispersion on the natural convective flow of a Casson fluid along an inclined plate embedded in a non-Darcy porous medium.The governing equations,representing momentum and energy conservations,are transformed into non-dimensional form using similarity transformations.To address the complexity of the resulting equations,a bivariate spectral quasilinearisation method is employed.The effects of relevant parameters—including thermal dispersion,Casson parameter,Biot number,Forchheimer number,inclination angle and nonlinear thermal convection parameter—are thoroughly examined.The results show that the drag coefficient and heat transfer rate increase with the nonlinear thermal convection parameter,Casson parameter and Biot number.In contrast,they decrease as the Forchheimer number and inclination angle increase.The velocity near the surface of the inclined plate increases with the Biot number,Casson parameter and nonlinear thermal convection parameter.However,it decreases farther from the plate.Additionally,the temperature of the Casson fluid increases with most parameters,except the Casson and nonlinear thermal convection parameters.
基金Project supported by the National Key R&D Project from Ministry of Science and Technology of China(Grant No.2022YFA1203100)the National Natural Science Foundation of China(Grant No.52122606)the funding from Shanghai Polytechnic University.
文摘As the size of transistors shrinks and power density increases,thermal simulation has become an indispensable part of the device design procedure.However,existing works for advanced technology transistors use simplified empirical models to calculate effective thermal conductivity in the simulations.In this work,we present a dataset of size-dependent effective thermal conductivity with electron and phonon properties extracted from ab initio computations.Absolute in-plane and cross-plane thermal conductivity data of eight semiconducting materials(Si,Ge,GaN,AlN,4H-SiC,GaAs,InAs,BAs)and four metallic materials(Al,W,TiN,Ti)with the characteristic length ranging from 5 nm to 50 nm have been provided.Besides the absolute value,normalized effective thermal conductivity is also given,in case it needs to be used with updated bulk thermal conductivity in the future.
文摘The case study is about obtaining the flow rate and saturation temperature of steam that makes it possible to heat a solution of water and ammonia nitrate (<i>ANSOL</i>) in a shell and helical coil tube heat exchanger, within a time interval, without that the crystallization of the <i>ANSOL</i> solution occurs. The desired production per batch of the solution is 5750 kg in 80 minutes. The analysis uses the concepts of efficiency and effectiveness to determine the heat transfer rate and temperature profiles that satisfy the imposed condition within a certain degree of safety and with the lowest possible cost in steam generation. Intermediate quantities necessary to reach the objective are the Reynolds number, Nusselt number, and global heat transfer coefficient for the shell and helical coil tube heat exchanger. Initially, the water is heated for a specified period and, subsequently, the ammonium nitrate is added to a given flow in a fixed mass flow rate.
文摘The work’s objective is to analyze the influence of the saturation temperature of the R134a refrigerant on the thermal performance of a shell and tube type condenser, with water and aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) nanoparticles flowing into the tube. For analysis, the heat exchanger is subdivided into three regions: subcooled liquid, saturated steam, and superheated steam. The shell and tube heat exchanger assumed as the basis for the study has 36 tubes, with rows of 4 tubes in line and three passes into the tube in each region. The parameters used to analyze the performance are efficiency and effectiveness, through variations of quantities such as saturation temperature, the nanofluid’s mass flow rate, fraction in the nanoparticles’ volume, and the number of passes in the tube in each region of the heat exchanger. The obtained results demonstrate that the efficiency is relatively high in all the analyzed situations. In each saturation temperature, the effectiveness can be increased by introducing fractions of nanoparticles in the water or increasing the number of passes in the tube.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51576078 and 51376070
文摘The concentrically layered thermal cloaks with isotropic materials could realize the equivalent thermal cloaking effect with Pendry＇s cloak, while the effectiveness is scarcely investigated quantitatively. Here we examine the cloaking effectiveness quantitatively by evaluating the standard deviation of the temperature difference between the simulated plane with the layered thermal cloak and Pendry＇s thermal cloak. The design rules for the isotropic materials in terms of thermal conductivity and layer thickness are presented. The present method could quan- titatively evaluate the cloaking effectiveness, and could open avenues for analyzing the cloaking effect, detecting the （anti-） cloaks, etc.
基金This work is supported by the National Natural Science Foundation of China(Nos.51578491 and 52238001).
文摘Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.
基金supported by the National Natural Science Foundation of China(U19B2005,21808238,U20B6005,22127812)the State Key Laboratory of Heavy Oil Processing,China University of Petroleumthe National Key Research and Development Program of China(2021YFC2800902)
文摘The research on the thermal property of the hydrate has recently made great progress,including the understanding of hydrate thermal conductivity and effective thermal conductivity(ETC)of hydratebearing sediment.The thermal conductivity of hydrate is of great significance for the hydrate-related field,such as the natural gas hydrate exploitation and prevention of the hydrate plugging in oil or gas pipelines.In order to obtain a comprehensive understanding of the research progress of the hydrate thermal conductivity and the ETC of hydrate-bearing sediment,the literature on the studies of the thermal conductivity of hydrate and the ETC of hydrate-bearing sediment were summarized and reviewed in this study.Firstly,experimental studies of the reported measured values and the temperature dependence of the thermal conductivity of hydrate were discussed and reviewed.Secondly,the studies of the experimental measurements of the ETC of hydrate-bearing sediment and the effects of temperature,porosity,hydrate saturation,water saturation,thermal conductivity of porous medium,phase change,and other factors on the ETC of hydrate-bearing sediment were discussed and reviewed.Thirdly,the research progress of modeling on the ETC of the hydrate-bearing sediment was reviewed.The thermal conductivity determines the heat transfer capacity of the hydrate reservoir and directly affects the hydrate exploitation efficiency.Future efforts need to be devoted to obtain experimental data of the ETC of hydrate reservoirs and establish models to accurately predict the ETC of hydrate-bearing sediment.
基金supported by National Natural Science Foundation of China(No.52177130)the Key Projects for Industrial Prospects and Core Technology Research in Suzhou City(No.SYC2022029)。
文摘Dielectric barrier discharge(DBD)plasma excited by a high-frequency alternating-current(AC)power supply is widely employed for the degradation of volatile organic compounds(VOCs).However,the thermal effect generated during the discharge process leads to energy waste and low energy utilization efficiency.In this work,an innovative DBD thermally-conducted catalysis(DBD-TCC)system,integrating high-frequency AC-DBD plasma and its generated thermal effects to activate the Co/SBA-15 catalyst,was employed for toluene removal.Specifically,Co/SBA-15 catalysts are closely positioned to the ground electrode of the plasma zone and can be heated and activated by the thermal effect when the voltage exceeds 10 k V.At12.4 k V,the temperature in the catalyst zone reached 261℃ in the DBD-TCC system,resulting in an increase in toluene degradation efficiency of 17%,CO_(2)selectivity of 21.2%,and energy efficiency of 27%,respectively,compared to the DBD system alone.In contrast,the DBD thermally-unconducted catalysis(DBD-TUC)system fails to enhance toluene degradation due to insufficient heat absorption and catalytic activation,highlighting the crucial role of AC-DBD generated heat in the activation of the catalyst.Furthermore,the degradation pathway and mechanism of toluene in the DBD-TCC system were hypothesized.This work is expected to provide an energy-efficient approach for high-frequency AC-DBD plasma removal of VOCs.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51764046 and 52160013)the Inner Mongolia Autonomous Region Postgraduate Research Innovation Project of China (Grant No. S20231165Z)the Research Program of Science and Technology at Universities of Inner Mongolia Autonomous Region of China (Grant Nos. 2023RCTD016 and 2024RCTD008)。
文摘Aerogel nanoporous materials possess high porosity, high specific surface area, and extremely low density due to their unique nanoscale network structure. Moreover, their effective thermal conductivity is very low, making them a new type of lightweight and highly efficient nanoscale super-insulating material. However, prediction of their effective thermal conductivity is challenging due to their uneven pore size distribution. To investigate the internal heat transfer mechanism of aerogel nanoporous materials, this study constructed a cross-aligned and cubic pore model(CACPM) based on the actual pore arrangement of SiO_(2) aerogel. Based on the established CACPM, the effective thermal conductivity expression for the aerogel was derived by simultaneously considering gas-phase heat conduction, solid-phase heat conduction, and radiative heat transfer. The derived expression was then compared with available experimental data and the Wei structure model. The results indicate that, according to the model established in this study for the derived thermal conductivity formula of silica aerogel, for powdery silica aerogel under the conditions of T = 298 K, a_(2)= 0.85, D_(1)= 90 μm, ρ = 128 kg/m^(3), within the pressure range of 0–10^(5)Pa, the average deviation between the calculated values and experimental values is 10.51%. In the pressure range of 10^(3)–10^(4)Pa, the deviation between calculated values and experimental values is within 4%. Under these conditions, the model has certain reference value in engineering verification. This study also makes a certain contribution to the research of aerogel thermal conductivity heat transfer models and calculation formulae.
基金Project(2022JJ30049)supported by the Natural Science Foundation of Hunan Province,China。
文摘The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package.Our study revealed significant spin-splitting within the Janus VSTe monolayer,which induced spin currents under a temperature gradient across the device.By applying a 1%tensile strain,the Janus VSTe monolayer exhibited a perfect thermal spin filtering effect(SFE),with the spin-up current nearly suppressed to zero.Both the unstrained and strained Janus VSTe monolayers demonstrated excellent spin caloritronic properties,with spin figures of merit of 10.915 and 8.432 at an average temperature of 100 K,respectively.Notably,these properties were found to be sensitive to temperature,performing optimally at lower temperatures.These results suggest a promising avenue for designing spin caloritronic devices aimed at efficient waste heat recovery.
基金Project (50925521) supported by the National Natural Science Fund for Distinguished Young Scholars of China
文摘Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.
文摘A DC to 5GHz series MEMS switch is designed and fabricated for wireless communication applications,and thermal effect and power handling of the series switch are discussed.The switch is made on glass substrate,and gold platinum contact is used to get a stable and little insert loss.From DC to 5GHz,0 6dB insertion loss,30dB isolation,and 30μs delay are demonstrated.Thermal effect of the switch is tested in 85℃ and -55℃ atmosphere separately.From DC to 4GHz,the insert loss of the switch increases 0 2dB in 85℃ and 0 4dB in -55℃,while the isolation holds the same value as that in room temperature.To measure the power handling capability of the switch,we applied a continuous RF power increasing from 10dBm to 35 1dBm with the step of 1 0dBm across the switch at 4GHz.The switch keeps working and shows a decrease of the insert loss for 0 1～0 6dB.The maximum continuous power handling (35 1dBm,about 3 24W) is higer than the reported value of shunt switch (about 420mW),which implies series switches have much better power handling capability.
文摘This work describes the discharge characteristics and acetone degradation with plasma under different electric fields based on a coaxial cylindrical dielectric barrier discharge(DBD)device energized by pulsed power.It is found that the segmented electrodes with appropriate spacing in coaxial cylindrical DBD are beneficial to the plasma ionization.In this work,the plasma distribution,discharge thermal effect,ionization of reactive species,and acetone degradation performance in coaxial cylindrical DBD with different segmented electrodes are systematically investigated.The experimental results show that segmented electrodes with a certain distance can cause additional ionization in the non-electrode-covered region between adjacent electrodes,thus enlarging the plasma region compared with a single electrode with equivalent total electrode length.The additional ionization involved the inner volume discharge between the quartz tubes and the outer surface discharge along the surface of the external quartz tube.The spatial distributions of the inner volume discharge and external surface discharge were predominantly governed by the radial and axial components of the inter-electrode electric field,respectively.The external surface discharge exhibited significant suppression when the electrode spacing was<1.5 mm,and it reached its maximum length at 3 mm spacing.When the electrode distance increased to 7-9 mm,a weak ionizing region appeared in the middle of the adjacent electrodes,which could be attributed to the gradual attenuation of the radial component with the increasing electrode spacing.A higher thermal effect and better oxidation of acetone to CO_(x)(CO and CO_(2))were achieved with the segmented electrode;the dual-segment configuration(3 mm per electrode)achieved a reactor temperature of 63.4℃,representing a 10℃enhancement over comparable single-electrode systems.Similarly,the CO_(2)and CO concentration reached 328.8 mg/m3and 105.7 mg/m3,respectively,in two 3 mm long segmented electrodes,which was an increase of 12.2%and 25.6%,respectively,compared with the single electrode.Notably,considering the equivalent ionization of the inner discharge with different electrodes,the enhanced thermal effects and CO_(x)conversion efficiency directly correlate with the expanded plasma zone induced by electrode segmentation.This work provides critical insights into optimizing electrode configurations for efficient plasma-assisted volatile organic compound degradation systems.
