High rock temperature is a great challenge frequently encountered during subsurface resource recovery and deep underground space utilization,and it is still unclear how the granitic rock responds to realtime high temp...High rock temperature is a great challenge frequently encountered during subsurface resource recovery and deep underground space utilization,and it is still unclear how the granitic rock responds to realtime high temperature upon shear loading.To better understand the shear fracture behavior and underlying processes of intact granite exposed to thermal-mechanical coupling loading,direct shear tests were conducted utilizing a newly built testing apparatus at varied normal stresses and high temperatures.Influencesof different temperatures and different heating methods(real-time heating and thermal treatment)on the shear mechanical behavior were compared and discussed.Results indicate that shear stress fluctuationswith some small stress drops occur as shear stress is approaching the peak strength under real-time heating,accompanied by more and earlier AE signal uprushes.This suggests that greater cracking events occur earlier during real-time heating than after thermal treatment,resulting in a lower peak shear strength.Furthermore,the peak shear strength,post-peak stress drop,and cohesion rise from room temperature(RT)to 200℃(the peak strength increases by 8%,5.8%,and 9.9%under normal stress of 5 MPa,15 MPa,and 20 MPa,correspondingly),and subsequently decline from 200℃to 400℃.Temperature has a limited impact on shear stiffness from RT to 200℃,but significantlyreduces it from 200℃to 400℃,with drops of 15%,7.9%,and 10%under normal stress of 5 MPa,15 MPa,and 20 MPa,respectively.Moreover,the shear strength and stiffness under real-time heating are lower than those for the thermally treated specimens.The strengthening of intact granite below 200℃upon shear is associated with loss of water and a more compacted structure,while the weakening effect of temperature on shear strength from 200℃to 400℃is due to the new thermal cracks and less brittle and stiff of minerals.展开更多
An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition b...An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition behavior of a composite propellant(CP)comprising ammonium nitrate(AN)as an oxidizer and magnesium(Mg)as a fuel.Optimization of the propellant formulation was conducted using Chemical Equilibrium with Applications-National Aeronautics and Space Administration(CEA-NASA)software,which demonstrated an increase in specific impulse by 12.09 s when the binder contained 50%NC.Fourier-transform infrared spectroscopy(FTIR)analysis confirmed the excellent compatibility between the components,and density measurements revealed an increase of 6.4%with a higher NC content.Morphological analysis using optical microscopy showed that NC doping improved the uniformity and compactness of the surface,reduced cavities,and achieved a more homogeneous particle distribution.Differential scanning calorimetry(DSC)analysis indicated a decrease in the decomposition temperature of the propellant as the NC content increased,while kinetic studies revealed a 48.68%reduction in the activation energy when 50%NC was incorporated into the binder.These findings suggest that the addition of NC enhances combustion efficiency and improves overall propellant performance.This study highlights the potential of the new HTPB-NC energetic binder as a promising approach for advancing solid propellant technology.展开更多
High-strength Al-Zn-Mg-Cu alloys are widely utilized,but their strength deteriorates as strengthening precipitates coarsen rapidly at elevated temperatures,limiting their applications above 150℃.This study systematic...High-strength Al-Zn-Mg-Cu alloys are widely utilized,but their strength deteriorates as strengthening precipitates coarsen rapidly at elevated temperatures,limiting their applications above 150℃.This study systematically investigates the microstructure evolution and its impact on the properties of peak-aged Al-Zn-Mg-Cu alloys with varying Zn/Mg ratios during thermal exposure at a series of temperatures from 150 to 300℃ for 500 h.The results reveal that alloys A1 and A2 with an optimal Zn/Mg ratio(1.50-2.14)and relatively lower(Zn+Mg)content(7.0-8.8 wt.%),exhibit superior heat resistance properties compared to the other three alloys.Despite having lower strength relative to alloys with higher solute content,peak-aged alloys A1 and A2 retain the highest strength after thermal exposure.This performance is attributed to the high proportion(over 80%)of T'/T phases in the precipitates for alloys A1 and A2,which demonstrate better thermal stability in comparison to η'/η phases.Additionally,the lower solute content reduces the driving force for diffusion of Zn and Mg atoms,thus inhibiting the coarsening of precipitates.Moreover,the study elucidates that the coarsening mechanism of precipitates transitions from interfacial diffusion control at 150℃ to matrix diffusion control at 200-300℃.These insights into the composition-dependent coarsening behavior of precipitates in dual-phase strengthened Al-Zn-Mg-Cu alloys offer valuable guidance for designing heat-resistant aluminum alloys with enhanced performance at elevated temperatures.展开更多
Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a ser...Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a series of dynamic compression tests were conducted on granite treated by cyclic thermal shocks at different temperatures.We analyzed the effects of cyclic thermal shock on the thermal-related physical and dynamic mechanical behaviors of granite.Specifically,the P-wave velocity,dynamic strength,and elastic modulus of the tested granite decrease with increasing temperature and cycle number,while porosity and peak strain increase.The degradation law of dynamic mechanical properties could be described by a cubic polynomial.Cyclic thermal shock promotes shear cracks propagation,causing dynamic failure mode of granite to transition from splitting to tensile-shear composite failure,accompanied by surface spalling and debris splashing.Moreover,the thermal shock damage evolution and coupled failure mechanism of tested granite are discussed.The evolution of thermal shock damage with thermal shock cycle numbers shows an obvious S-shaped surface,featured by an exponential correlation with dynamic mechanical parameters.In addition,with increasing thermal shock temperature and cycles,granite mineral species barely change,but the length and width of thermal cracks increase significantly.The non-uniform expansion of minerals,thermal shock-induced cracking,and water-rock interaction are primary factors for deteriorating dynamic mechanical properties of granite under cyclic thermal shock.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 growing demand for geothermal energy exploration and deep engineering projects necessitates a deeper understanding of rock behavior under extreme thermal conditions.This study investigates the effect of thermal tr...The growing demand for geothermal energy exploration and deep engineering projects necessitates a deeper understanding of rock behavior under extreme thermal conditions.This study investigates the effect of thermal treatment on the shear behavior of sedimentary sandstone and igneous granite,which are abundant in the Earth's crust.Direct shear tests were conducted on rock joints at room temperature(RT),250℃,and 500℃.The results show that the joints in sandstone and granite exhibit improved compressive and shear strength up to a temperature threshold of 200℃–350℃,followed by significant weakening beyond this range.This study investigated key parameters,including normal and shear stiffness,maximum joint closure,peak and residual shear strengths,internal friction angle,dilation angle,and cohesion.The compressive behavior of both rock types followed a modifiedBandis's equation.The peak shear strength followed Patton's bilinear and Jaeger's nonlinear failure criteria more accurately than the Mohr–Coulomb criterion.The results of this study provide valuable insights into the temperature-dependent behavior of sandstone and granite joints under compressive and shear loads,and their interoperation was strongly dependent on the mineralogical and structural components of the two rock types.These results have advanced our understanding of the temperature-dependent behavior of rock fractures,improving the safety of underground structures under thermal effects.展开更多
High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subject...High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subjected to heating–water cooling treatments at temperatures ranging from 25℃ to 400℃.Changes in physical properties,including volume expansion,mass loss,and P-wave velocity,were examined to quantify the extent of thermal damage.Results show that visible surface cracking occurs on granite samples treated above 300℃,with P-wave velocity being the most sensitive indicator of thermal damage.Uniaxial and triaxial compression tests were conducted to explore the effects of temperature and confining pressure on granite’s strength,deformation,failure modes,energy evolution,and brittleness.While peak strength remains largely unaffected by temperature,failure modes transition from axial splitting to shear as confining pressure increases.Thermal damage reduces the rock’s energy storage capacity and increases energy dissipation during loading.The brittleness index decreases with temperature and confining pressure,though granite still exhibits pronounced brittle behavior within the studied range.Distinct differences were observed in the AE temporal characteristics and energy evolution of granite samples under uniaxial and triaxial compression conditions.As the specimen approaches failure,the abrupt increase in AE hit rate occurs earlier than the corresponding rise in AE energy.The global b-value of the granite samples increased with treatment temperature,and the global b-value in triaxial compression tests was higher than that in uniaxial compression tests.The evolution of timedependent b-value also varied with increasing confining pressure.These findings,particularly the AE temporal characteristics and distinct b-value evolution under confinement of thermally damaged granite,provide important implications for microseismic-based stability assessment and early warning in thermally damaged rock masses.展开更多
Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance i...Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance in developing novel PS devices.In this paper,we develop a general temperature-deformation-polarization-carrier(TDPC)coupling model for sandwich-type PS beams involving pyroelectricity under thermal loadings,based on three-dimensional(3D)basic equations of the thermo-piezoelectric semiconductor(TPS).We derive analytical solutions for extensional,bending,and buckling deformations of simply-supported sandwich n-type PS beams subjected to open-circuit and electrically isolated boundary conditions.The accuracy of the proposed model in this paper is verified through finite element simulations implemented in the COMSOL software.Numerical results show that the initial electron concentration and the thickness ratio of the PS layer to the beam's total thickness have a significant effect on thermally induced extensional and bending responses,as well as critical buckling mechanical and thermal loadings.This study provides a theoretical framework and guidance for designing semiconductor devices based on sandwich PS beam structures.展开更多
In this study,we simulated the thermal behavior of the mud-brick walls of a Nubian vault.We used EnergyPlus software for the simulation.The results obtained showed that the indoor temperature varies from 25.5℃ to 26....In this study,we simulated the thermal behavior of the mud-brick walls of a Nubian vault.We used EnergyPlus software for the simulation.The results obtained showed that the indoor temperature varies from 25.5℃ to 26.5℃ for the period of January 2018.It varies from 33.2℃ to 33.6℃ with an average value of 33.1℃ for the month of April 2018.For the period of July 2018,it varies from 30.3℃ to 32.2℃ with an average value of 31.2℃..Relative humidity for the period of July ranged from 62.3%to 73.5%,with an average value of 67.9%.The simulation enabled us to compare simulated and measured temperature and humidity values.We found that the level of thermal comfort in the Nubian vault is acceptable in both cool and hot periods.In view of these results,we can say that the Nubian vault is an architecture suited to our climate.The technical concept of the Nubian vault is adapted to the climatic conditions and traditional know-how of the Sahel.We also found that the use of raw earth,a locally available material,and the Nubian vault architectural process,contribute to thermal comfort and a reappropriation of local and adapted know-how.展开更多
In integrated circuit packaging,thermal interface materials(TIMs)must exhibit high thermal conductivity and electrical resistivity to prevent short circuits,enhance reliability,and ensure safety in high-voltage applic...In integrated circuit packaging,thermal interface materials(TIMs)must exhibit high thermal conductivity and electrical resistivity to prevent short circuits,enhance reliability,and ensure safety in high-voltage applications.We proposed the thermal-percolation electrical-resistive TIM incorporating binary fillers of both insulating and metallic nanowires with an orientation in the insulating polymer matrix.High thermal conductivity can be achieved through thermal percolation,while electrical non-conductivity is preserved by carefully controlling the electrical percolation threshold through metallic nanowire orientation.The electrical conductivity of the composite can be further regulated by adjusting the orientation and aspect ratio of the metallic fillers.A thermal conductivity of 10 W·m^(-1)·K^(-1)is achieved,with electrical non-conductive behavior preserved.This approach offers a pathway to realizing“thermal-percolation electrical-resistive”in hybrid TIMs,providing a strategic framework for designing high-performance TIMs.展开更多
An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microst...An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus,thermal shock damage resistance parameters,retainment of elastic modulus after thermal shock,and scanning electron microscopy.The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens.The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder.The presence of a martensitic phase transformation in partially unstable ZrO2 and thermal mismatches among various phases contributed to a controlled formation of microcracks.And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks.This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories,consequently prolonging their service life.展开更多
This work quantifies the thermal performance of natural composite blocks made from Yapatera diatomaceous earth reinforced with sugarcane bagasse fibres.Prismatic specimens(185×185 mm)with three thicknesses(≈76 m...This work quantifies the thermal performance of natural composite blocks made from Yapatera diatomaceous earth reinforced with sugarcane bagasse fibres.Prismatic specimens(185×185 mm)with three thicknesses(≈76 mm,100 mm,and 150 mm)and bagasse contents of 5–15%(wt.)were tested at hot-face temperatures of 100,250,and 450℃in a full-factorial 3×3×3 plan(54 tests).Thermal conductivity(k)was measured using a guarded hot-plate device aligned with ASTM D5470/E1530/C177.The measured k averaged 0.125 W/m·K(range~0.088–0.220 W/m·K)and remained stable in function up to 500℃.ANOVA showed that temperature and thickness significantly increased k(p<0.05),while fibre content had a weaker,non-monotonic effect beyond~10%.A response-surface model(RSM)provided accurate predictions(R^(2)≈0.95).For design purposes,thermal resistance was computed as R=Δx/k.A 150 mm block yielded R≈1.20 m^(2)K/W,comparable to~0.40 m of hollow ceramic brick and>1.0 m of concrete to reach a similar R.The composite therefore occupies a distinct niche:medium-performance insulation with high-temperature stability(≤500℃),low embodied energy(air-dried manufacturing,agro-waste feedstock),and competitive cost potential.These results support its use in industrial and building applications where conventional insulators are unsustainable or operate below the required temperature window.展开更多
This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-i...This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-ideal FG-GPLRC beams in which the ideal beams have smooth profiles of material distributions and another beams have layer-wise distributions of materials.The material profiles of the ideal beams are utilized as the controlling tracks for producing the material distributions of the non-ideal beams via a layer-to-layer integration technique.This technique confirms that the overall weight fraction of the materials is the same for both types of beams.The proposed models can be used to determine the material properties of the beams for further investigation on thermal buckling and post-buckling of the beams.Third-order shear deformation theory is employed to construct the energy equations of the problems,and then they are solved by the implementation of the Jacobi-Ritz method cooperating with the direct iteration procedure and Newton-Raphson technique.From our investigation,it can be disclosed that when non-ideal beams are created using ideal beams parabolic profile,the results differ significantly.However,the differences between the results of ideal and non-ideal beams can be eliminated by adding more layers.展开更多
The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF...The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.展开更多
The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be de...The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be decomposed and recovered through conventional oxidative roasting and hydrochloric acid leaching process.An efficient,clean,and economical process called the"combined method"was proposed for the utilization of the Mountain Pass mine to extract rare earths from Mountain Pass rare earth concentrate(MPREC).The main steps of this process include weak oxidation atmosphere roasting,step leaching of hydrochloric acid,solid-liquid separation,the monazite slag with sulfuric acid roasting water leaching,etc.In this paper,the roasting process of MPREC under a weak oxidation atmosphere was investigated.The study examines the thermal decomposition kinetics,phase transition process,and leaching behavior of MPREC in air/CO_(2)atmosphere.Results show that,the activation energy(Ea)for MPREC thermal decomposition in air and CO_(2)atmosphere are 146 and 320 kJ/mol,respectively.At temperature above 500℃in air or above 700℃in CO_(2)atmosphere,REOF are generated from bastnaesite through an in-situ reaction with CaO,which is decomposed from CaCO_(3),to form CaF_(2)and rare earth oxide(REO).Thus,F is regulated into solid phase.In an oxidizing atmosphere,the thermal decomposition of bastnaesite is accompanied by the rapid oxidation of Ce(Ⅲ).In co ntrast,the oxidation of Ce(Ⅲ)in a CO_(2)atmosphere is significantly inhibited.At 700℃,the oxidation rate of Ce in air is 74.09%,while in a CO_(2)atmosphere,it is only 33.83%.The hydrochloric acid leaching experiment shows that,the leaching rate of rare earth after roasting at 600℃under an air atmosphere reaches to 82.9%,and it reaches 87%after roasting at 800℃under a CO_(2)atmosphere.The reduction of Ce oxidation in a weak oxidizing atmosphere significantly improves the leaching rate of Ce.展开更多
Non-isothermal aging(NIA)is a composite heat treatment process that involves heating aging,cooling aging,and complex solute precipitation sequences.The precipitation behavior and the strengthening and toughening mecha...Non-isothermal aging(NIA)is a composite heat treatment process that involves heating aging,cooling aging,and complex solute precipitation sequences.The precipitation behavior and the strengthening and toughening mechanisms of the 2014 Al alloy during NIA were studied by employing tensile,fatigue crack growth,hardness,and electronic conductivity tests,as well as high-resolution transmission electron microscopy and scanning electron microscopy.The results show that during NIA,theθ′phase exhibits a complex process of nucleation,nucleation and growth,nucleation and growth and coarsening,growth and coarsening,nucleation and growth,and nucleation.NIA treatment imparts a mixed precipitation characteristic on the alloy,which is manifested as coherent precipitates,including GP zones,θ′′phases,small-sizedθ′phases,and semi-coherent or non-coherent precipitates such as large-sizedθ′phases and equilibriumθphases.The simultaneous strengthening and toughening of the NIA-treated 2014 Al alloy is caused by the synergistic effects of the particle-shearing mechanism and Orowan bypassing mechanism.展开更多
Effective thermal management is paramount for successfully deploying lithium-ion batteries in residential settings as storage systems for the exploitation of renewable sources.Uncontrolled temperature increases within...Effective thermal management is paramount for successfully deploying lithium-ion batteries in residential settings as storage systems for the exploitation of renewable sources.Uncontrolled temperature increases within battery packs can lead to critical issues such as cell overheating,potentially culminating in thermal runaway events and,in extreme cases,leading to fire or explosions.Thiswork presents a comprehensive numerical thermalmodel of a battery pack made of prototype pouch cells based on lithium ferrophosphate(LFP)chemistry.The multi-physical model is specifically developed to investigate real-world operating scenarios and to assess safety considerations.The considered energy storage system is a battery designed for residential applications,in its integration with a photovoltaic(PV)installation.The actual electrochemical behavior of the prototype cell during the charging and discharging processes is modeled and validated on the ground of experimental data.The essential steps leading to the numerical schematization of the battery pack are then presented to apply themodel to two different use scenarios,differing for the user loads.The first scenario corresponds to a typical residential load,with standby lights being active during the night,solar generation with its peak at noon,and appliance use shifting in the afternoon and the evening.In the second scenario,a double demand for energy is present thatmakes the battery never reach 100%of the State of Charge(SoC)and dischargemore rapidly with respect to what occurs under the first scenario.Comparing the simulated temperature with the assumed C-rate,namely the charge or discharge current divided by the battery nominal capacity,it is found that peaks coincide with the charging phase;subsequently,the current tends to a zero value,and consequently,the temperature suddenly reaches the value of the environment.Finally,the model is also utilized to simulate a condition of thermal runaway by introducing critical conditions within a specific pouch cell.In this simulation,the thermal exchange between the cell in thermal runaway and the rest of the system remains within acceptable limits.This occurs due to the short duration of the process and to the module casing coated with an insulating material.The work provides an essential foundation for conducting numerical simulations of battery packs operating also at higher power levels.展开更多
This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carb...This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carbon fibers T700SC(SCF)within a temperature range of 330375℃.The research focuses on the PN75 monomer and DCBA blend reinforced SCF composites with varying SCF content,examining mass loss and changes in flexural strength after thermal aging for 50 h(h).Results show that the SCF-reinforced composites based on the PN75/DCBA blend consistently outperform the neat blend in flexural strength,both at room temperature and after thermal aging.The introduction of the SCF significantly improves the composites'thermal stability and mechanical retention,with higher SCF content correlating to better performance.Notably,after aging at 350℃,the SCF-reinforced composites based(30%(mass)SCF)retained 88.8%of its flexural strength,compared to 61.1%for the neat blend.Morphological analysis reveals that while thermal aging causes degradation of the PN75/DCBA blend layer on SCF surfaces,the overall composite structure maintains good mechanical properties up to 350℃.At 375℃,significant degradation occurs,yet the composites still retain flexural strengths above 78 MPa.This study demonstrates the potential of the SCF-reinforced composites based on PN75/DCBA blend for high-temperature applications,establishing their upper-temperature limit for long-term use in oxidative environments.展开更多
Investigation of thermal effects on the strain rate-dependent properties of compacted bentonite is crucial for the long-term safety assessment of deep geological repository for disposal of high-level radioactive waste...Investigation of thermal effects on the strain rate-dependent properties of compacted bentonite is crucial for the long-term safety assessment of deep geological repository for disposal of high-level radioactive waste.In the present work,cylindrical GMZ01 bentonite specimens were compacted with suction-controlled by the vapor equilibrium technique.Then,a series of temperature-and suction-controlled stepwise constant rate of strain(CRS)tests was performed and the rate-dependent compressibility behavior of the highly compacted GMZ01 bentonite was investigated.The plastic compressibility parameterλ,the elastic compressibility parameterκ,the yield stress p0,as well as the viscous parameterαwere determined.Results indicate thatλ,κandαdecrease and p0 increases as suction increases.Upon heating,parametersλ,αand p0 decrease.It is also found that p0 increases linearly with increasing CRS in a double-logarithm coordinate.Based on the experimental results,a viscosity parameterα(s,T)was fitted to capture the effects of suction s and temperature T on the relationship between yield stress and strain rate.Then,an elastic-thermo-viscoplastic model for unsaturated soils was developed to describe the thermal effects on the rate-dependent behavior of highly compacted GMZ01 bentonite.Validation showed that the calculated results agreed well to the measured ones.展开更多
Behavior recognition of Hu sheep contributes to their intensive and intelligent farming.Due to the generally high density of Hu sheep farming,severe occlusion occurs among different behaviors and even among sheep perf...Behavior recognition of Hu sheep contributes to their intensive and intelligent farming.Due to the generally high density of Hu sheep farming,severe occlusion occurs among different behaviors and even among sheep performing the same behavior,leading to missing and false detection issues in existing behavior recognition methods.A high-low frequency aggregated attention and negative sample comprehensive score loss and comprehensive score soft non-maximum suppression-YOLO(HLNC-YOLO)was proposed for identifying the behavior of Hu sheep,addressing the issues of missed and erroneous detections caused by occlusion between Hu sheep in intensive farming.Firstly,images of four typical behaviors-standing,lying,eating,and drinking-were collected from the sheep farm to construct the Hu sheep behavior dataset(HSBD).Next,to solve the occlusion issues,during the training phase,the C2F-HLAtt module was integrated,which combined high-low frequency aggregation attention,into the YOLO v8 Backbone to perceive occluded objects and introduce an auxiliary reversible branch to retain more effective features.Using comprehensive score regression loss(CSLoss)to reduce the scores of suboptimal boxes and enhance the comprehensive scores of occluded object boxes.Finally,the soft comprehensive score non-maximal suppression(Soft-CS-NMS)algorithm filtered prediction boxes during the inferencing.Testing on the HSBD,HLNC-YOLO achieved a mean average precision(mAP@50)of 87.8%,with a memory footprint of 17.4 MB.This represented an improvement of 7.1,2.2,4.6,and 11 percentage points over YOLO v8,YOLO v9,YOLO v10,and Faster R-CNN,respectively.Research indicated that the HLNC-YOLO accurately identified the behavior of Hu sheep in intensive farming and possessed generalization capabilities,providing technical support for smart farming.展开更多
基金support from the Taishan Scholars Program,Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS),Grant No.ZDBS-LY-DQC022Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering Safety,Grant No.SKLGME023003.
文摘High rock temperature is a great challenge frequently encountered during subsurface resource recovery and deep underground space utilization,and it is still unclear how the granitic rock responds to realtime high temperature upon shear loading.To better understand the shear fracture behavior and underlying processes of intact granite exposed to thermal-mechanical coupling loading,direct shear tests were conducted utilizing a newly built testing apparatus at varied normal stresses and high temperatures.Influencesof different temperatures and different heating methods(real-time heating and thermal treatment)on the shear mechanical behavior were compared and discussed.Results indicate that shear stress fluctuationswith some small stress drops occur as shear stress is approaching the peak strength under real-time heating,accompanied by more and earlier AE signal uprushes.This suggests that greater cracking events occur earlier during real-time heating than after thermal treatment,resulting in a lower peak shear strength.Furthermore,the peak shear strength,post-peak stress drop,and cohesion rise from room temperature(RT)to 200℃(the peak strength increases by 8%,5.8%,and 9.9%under normal stress of 5 MPa,15 MPa,and 20 MPa,correspondingly),and subsequently decline from 200℃to 400℃.Temperature has a limited impact on shear stiffness from RT to 200℃,but significantlyreduces it from 200℃to 400℃,with drops of 15%,7.9%,and 10%under normal stress of 5 MPa,15 MPa,and 20 MPa,respectively.Moreover,the shear strength and stiffness under real-time heating are lower than those for the thermally treated specimens.The strengthening of intact granite below 200℃upon shear is associated with loss of water and a more compacted structure,while the weakening effect of temperature on shear strength from 200℃to 400℃is due to the new thermal cracks and less brittle and stiff of minerals.
文摘An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition behavior of a composite propellant(CP)comprising ammonium nitrate(AN)as an oxidizer and magnesium(Mg)as a fuel.Optimization of the propellant formulation was conducted using Chemical Equilibrium with Applications-National Aeronautics and Space Administration(CEA-NASA)software,which demonstrated an increase in specific impulse by 12.09 s when the binder contained 50%NC.Fourier-transform infrared spectroscopy(FTIR)analysis confirmed the excellent compatibility between the components,and density measurements revealed an increase of 6.4%with a higher NC content.Morphological analysis using optical microscopy showed that NC doping improved the uniformity and compactness of the surface,reduced cavities,and achieved a more homogeneous particle distribution.Differential scanning calorimetry(DSC)analysis indicated a decrease in the decomposition temperature of the propellant as the NC content increased,while kinetic studies revealed a 48.68%reduction in the activation energy when 50%NC was incorporated into the binder.These findings suggest that the addition of NC enhances combustion efficiency and improves overall propellant performance.This study highlights the potential of the new HTPB-NC energetic binder as a promising approach for advancing solid propellant technology.
基金supported by the Natural Science Foundation of Chongqing(Nos.CSTB2022NSCQ-LZX0002 and CSTB2022NSCQ-BHX0624)the Chongqing Key Project for Technological Innovation and Application(No.CSTB2022TIAD-KPX0073)+1 种基金the Opening Project of State Key Laboratory for Advanced Metals and Materials(No.2022-Z03)the Science and Technology Research Program of Chongqing Municipal Education Commission(No.KJQN202200810).
文摘High-strength Al-Zn-Mg-Cu alloys are widely utilized,but their strength deteriorates as strengthening precipitates coarsen rapidly at elevated temperatures,limiting their applications above 150℃.This study systematically investigates the microstructure evolution and its impact on the properties of peak-aged Al-Zn-Mg-Cu alloys with varying Zn/Mg ratios during thermal exposure at a series of temperatures from 150 to 300℃ for 500 h.The results reveal that alloys A1 and A2 with an optimal Zn/Mg ratio(1.50-2.14)and relatively lower(Zn+Mg)content(7.0-8.8 wt.%),exhibit superior heat resistance properties compared to the other three alloys.Despite having lower strength relative to alloys with higher solute content,peak-aged alloys A1 and A2 retain the highest strength after thermal exposure.This performance is attributed to the high proportion(over 80%)of T'/T phases in the precipitates for alloys A1 and A2,which demonstrate better thermal stability in comparison to η'/η phases.Additionally,the lower solute content reduces the driving force for diffusion of Zn and Mg atoms,thus inhibiting the coarsening of precipitates.Moreover,the study elucidates that the coarsening mechanism of precipitates transitions from interfacial diffusion control at 150℃ to matrix diffusion control at 200-300℃.These insights into the composition-dependent coarsening behavior of precipitates in dual-phase strengthened Al-Zn-Mg-Cu alloys offer valuable guidance for designing heat-resistant aluminum alloys with enhanced performance at elevated temperatures.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(Grant Nos.52225904 and 52039007)the Natural Science Foundation of Sichuan Province(Grant No.2023NSFSC0377)supported by the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a series of dynamic compression tests were conducted on granite treated by cyclic thermal shocks at different temperatures.We analyzed the effects of cyclic thermal shock on the thermal-related physical and dynamic mechanical behaviors of granite.Specifically,the P-wave velocity,dynamic strength,and elastic modulus of the tested granite decrease with increasing temperature and cycle number,while porosity and peak strain increase.The degradation law of dynamic mechanical properties could be described by a cubic polynomial.Cyclic thermal shock promotes shear cracks propagation,causing dynamic failure mode of granite to transition from splitting to tensile-shear composite failure,accompanied by surface spalling and debris splashing.Moreover,the thermal shock damage evolution and coupled failure mechanism of tested granite are discussed.The evolution of thermal shock damage with thermal shock cycle numbers shows an obvious S-shaped surface,featured by an exponential correlation with dynamic mechanical parameters.In addition,with increasing thermal shock temperature and cycles,granite mineral species barely change,but the length and width of thermal cracks increase significantly.The non-uniform expansion of minerals,thermal shock-induced cracking,and water-rock interaction are primary factors for deteriorating dynamic mechanical properties of granite under cyclic thermal shock.
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the ORSP at Abu Dhabi University,UAE,for funding this project(Grant No.19300751).
文摘The growing demand for geothermal energy exploration and deep engineering projects necessitates a deeper understanding of rock behavior under extreme thermal conditions.This study investigates the effect of thermal treatment on the shear behavior of sedimentary sandstone and igneous granite,which are abundant in the Earth's crust.Direct shear tests were conducted on rock joints at room temperature(RT),250℃,and 500℃.The results show that the joints in sandstone and granite exhibit improved compressive and shear strength up to a temperature threshold of 200℃–350℃,followed by significant weakening beyond this range.This study investigated key parameters,including normal and shear stiffness,maximum joint closure,peak and residual shear strengths,internal friction angle,dilation angle,and cohesion.The compressive behavior of both rock types followed a modifiedBandis's equation.The peak shear strength followed Patton's bilinear and Jaeger's nonlinear failure criteria more accurately than the Mohr–Coulomb criterion.The results of this study provide valuable insights into the temperature-dependent behavior of sandstone and granite joints under compressive and shear loads,and their interoperation was strongly dependent on the mineralogical and structural components of the two rock types.These results have advanced our understanding of the temperature-dependent behavior of rock fractures,improving the safety of underground structures under thermal effects.
基金supported by the CHN Energy Investment Group,grant numbers GJNY-23-86 and GJNY-23-92.
文摘High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subjected to heating–water cooling treatments at temperatures ranging from 25℃ to 400℃.Changes in physical properties,including volume expansion,mass loss,and P-wave velocity,were examined to quantify the extent of thermal damage.Results show that visible surface cracking occurs on granite samples treated above 300℃,with P-wave velocity being the most sensitive indicator of thermal damage.Uniaxial and triaxial compression tests were conducted to explore the effects of temperature and confining pressure on granite’s strength,deformation,failure modes,energy evolution,and brittleness.While peak strength remains largely unaffected by temperature,failure modes transition from axial splitting to shear as confining pressure increases.Thermal damage reduces the rock’s energy storage capacity and increases energy dissipation during loading.The brittleness index decreases with temperature and confining pressure,though granite still exhibits pronounced brittle behavior within the studied range.Distinct differences were observed in the AE temporal characteristics and energy evolution of granite samples under uniaxial and triaxial compression conditions.As the specimen approaches failure,the abrupt increase in AE hit rate occurs earlier than the corresponding rise in AE energy.The global b-value of the granite samples increased with treatment temperature,and the global b-value in triaxial compression tests was higher than that in uniaxial compression tests.The evolution of timedependent b-value also varied with increasing confining pressure.These findings,particularly the AE temporal characteristics and distinct b-value evolution under confinement of thermally damaged granite,provide important implications for microseismic-based stability assessment and early warning in thermally damaged rock masses.
基金Project supported by the National Natural Science Foundation of China(No.11672265)。
文摘Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance in developing novel PS devices.In this paper,we develop a general temperature-deformation-polarization-carrier(TDPC)coupling model for sandwich-type PS beams involving pyroelectricity under thermal loadings,based on three-dimensional(3D)basic equations of the thermo-piezoelectric semiconductor(TPS).We derive analytical solutions for extensional,bending,and buckling deformations of simply-supported sandwich n-type PS beams subjected to open-circuit and electrically isolated boundary conditions.The accuracy of the proposed model in this paper is verified through finite element simulations implemented in the COMSOL software.Numerical results show that the initial electron concentration and the thickness ratio of the PS layer to the beam's total thickness have a significant effect on thermally induced extensional and bending responses,as well as critical buckling mechanical and thermal loadings.This study provides a theoretical framework and guidance for designing semiconductor devices based on sandwich PS beam structures.
文摘In this study,we simulated the thermal behavior of the mud-brick walls of a Nubian vault.We used EnergyPlus software for the simulation.The results obtained showed that the indoor temperature varies from 25.5℃ to 26.5℃ for the period of January 2018.It varies from 33.2℃ to 33.6℃ with an average value of 33.1℃ for the month of April 2018.For the period of July 2018,it varies from 30.3℃ to 32.2℃ with an average value of 31.2℃..Relative humidity for the period of July ranged from 62.3%to 73.5%,with an average value of 67.9%.The simulation enabled us to compare simulated and measured temperature and humidity values.We found that the level of thermal comfort in the Nubian vault is acceptable in both cool and hot periods.In view of these results,we can say that the Nubian vault is an architecture suited to our climate.The technical concept of the Nubian vault is adapted to the climatic conditions and traditional know-how of the Sahel.We also found that the use of raw earth,a locally available material,and the Nubian vault architectural process,contribute to thermal comfort and a reappropriation of local and adapted know-how.
基金supported by the National Key R&D Program(Grant No.2022YFA1203-100)sponsorship by Shanghai Sailing Program(Grant No.24YF2713800)+2 种基金financial support from the Local College Capacity Building Project of Shanghai Municipal Science and Technology Commission(Grant No.20010500700)the Natural Science Foundation of Shanghai(Grant No.23ZR1424300)Shanghai Shuguang Program(Grant No.22SG56)。
文摘In integrated circuit packaging,thermal interface materials(TIMs)must exhibit high thermal conductivity and electrical resistivity to prevent short circuits,enhance reliability,and ensure safety in high-voltage applications.We proposed the thermal-percolation electrical-resistive TIM incorporating binary fillers of both insulating and metallic nanowires with an orientation in the insulating polymer matrix.High thermal conductivity can be achieved through thermal percolation,while electrical non-conductivity is preserved by carefully controlling the electrical percolation threshold through metallic nanowire orientation.The electrical conductivity of the composite can be further regulated by adjusting the orientation and aspect ratio of the metallic fillers.A thermal conductivity of 10 W·m^(-1)·K^(-1)is achieved,with electrical non-conductive behavior preserved.This approach offers a pathway to realizing“thermal-percolation electrical-resistive”in hybrid TIMs,providing a strategic framework for designing high-performance TIMs.
基金supported by the Key Project of the National Natural Science Foundation of China(Grant No.U21A2058)the Hebei Guoliang New Materials Co.,Ltd.(Grant No.22150239J).
文摘An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus,thermal shock damage resistance parameters,retainment of elastic modulus after thermal shock,and scanning electron microscopy.The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens.The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder.The presence of a martensitic phase transformation in partially unstable ZrO2 and thermal mismatches among various phases contributed to a controlled formation of microcracks.And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks.This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories,consequently prolonging their service life.
基金supported by the 2022 Teaching Research Projects Competition of Santo Toribio de Mogrovejo Catholic University(USAT),under grant number 1 under the title:“Adding Value to Sugar Cane Bagasse and Yapatera Diatomaceous Earth as a Composite Material for Thermal Insulation”.
文摘This work quantifies the thermal performance of natural composite blocks made from Yapatera diatomaceous earth reinforced with sugarcane bagasse fibres.Prismatic specimens(185×185 mm)with three thicknesses(≈76 mm,100 mm,and 150 mm)and bagasse contents of 5–15%(wt.)were tested at hot-face temperatures of 100,250,and 450℃in a full-factorial 3×3×3 plan(54 tests).Thermal conductivity(k)was measured using a guarded hot-plate device aligned with ASTM D5470/E1530/C177.The measured k averaged 0.125 W/m·K(range~0.088–0.220 W/m·K)and remained stable in function up to 500℃.ANOVA showed that temperature and thickness significantly increased k(p<0.05),while fibre content had a weaker,non-monotonic effect beyond~10%.A response-surface model(RSM)provided accurate predictions(R^(2)≈0.95).For design purposes,thermal resistance was computed as R=Δx/k.A 150 mm block yielded R≈1.20 m^(2)K/W,comparable to~0.40 m of hollow ceramic brick and>1.0 m of concrete to reach a similar R.The composite therefore occupies a distinct niche:medium-performance insulation with high-temperature stability(≤500℃),low embodied energy(air-dried manufacturing,agro-waste feedstock),and competitive cost potential.These results support its use in industrial and building applications where conventional insulators are unsustainable or operate below the required temperature window.
基金supported by the Thailand Science Research and Innovation Fund(Grant No.FRB660041/0227).
文摘This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-ideal FG-GPLRC beams in which the ideal beams have smooth profiles of material distributions and another beams have layer-wise distributions of materials.The material profiles of the ideal beams are utilized as the controlling tracks for producing the material distributions of the non-ideal beams via a layer-to-layer integration technique.This technique confirms that the overall weight fraction of the materials is the same for both types of beams.The proposed models can be used to determine the material properties of the beams for further investigation on thermal buckling and post-buckling of the beams.Third-order shear deformation theory is employed to construct the energy equations of the problems,and then they are solved by the implementation of the Jacobi-Ritz method cooperating with the direct iteration procedure and Newton-Raphson technique.From our investigation,it can be disclosed that when non-ideal beams are created using ideal beams parabolic profile,the results differ significantly.However,the differences between the results of ideal and non-ideal beams can be eliminated by adding more layers.
基金National Natural Science Foundation of China(11875039)Shanxi Scholarship Council of China(2023-033)+2 种基金Fundamental Research Program of Shanxi Province(202303021221071)China Baowu Low Carbon Metallurgical Innovation Foundation(2022)2023 Anhui Major Industrial Innovation Plan Project。
文摘The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.
基金supported by the National Key Research and Development Program of China(2020YFC1909104)National Natural Science Foundation of China(52274355)Major Science and Technology Project of Inner Mongolia Autonomous Region(2021ZD0016)。
文摘The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be decomposed and recovered through conventional oxidative roasting and hydrochloric acid leaching process.An efficient,clean,and economical process called the"combined method"was proposed for the utilization of the Mountain Pass mine to extract rare earths from Mountain Pass rare earth concentrate(MPREC).The main steps of this process include weak oxidation atmosphere roasting,step leaching of hydrochloric acid,solid-liquid separation,the monazite slag with sulfuric acid roasting water leaching,etc.In this paper,the roasting process of MPREC under a weak oxidation atmosphere was investigated.The study examines the thermal decomposition kinetics,phase transition process,and leaching behavior of MPREC in air/CO_(2)atmosphere.Results show that,the activation energy(Ea)for MPREC thermal decomposition in air and CO_(2)atmosphere are 146 and 320 kJ/mol,respectively.At temperature above 500℃in air or above 700℃in CO_(2)atmosphere,REOF are generated from bastnaesite through an in-situ reaction with CaO,which is decomposed from CaCO_(3),to form CaF_(2)and rare earth oxide(REO).Thus,F is regulated into solid phase.In an oxidizing atmosphere,the thermal decomposition of bastnaesite is accompanied by the rapid oxidation of Ce(Ⅲ).In co ntrast,the oxidation of Ce(Ⅲ)in a CO_(2)atmosphere is significantly inhibited.At 700℃,the oxidation rate of Ce in air is 74.09%,while in a CO_(2)atmosphere,it is only 33.83%.The hydrochloric acid leaching experiment shows that,the leaching rate of rare earth after roasting at 600℃under an air atmosphere reaches to 82.9%,and it reaches 87%after roasting at 800℃under a CO_(2)atmosphere.The reduction of Ce oxidation in a weak oxidizing atmosphere significantly improves the leaching rate of Ce.
基金supported by the Science Foundation of Hunan Province,China(No.2020JJ5215)Scientific Research Project of Hunan Provincial Department of Education,China(No.21B0594)the Open Fund of Hunan Key Laboratory of Electromagnetic Equipment Design and Manufacturing,China(No.DC202007)。
文摘Non-isothermal aging(NIA)is a composite heat treatment process that involves heating aging,cooling aging,and complex solute precipitation sequences.The precipitation behavior and the strengthening and toughening mechanisms of the 2014 Al alloy during NIA were studied by employing tensile,fatigue crack growth,hardness,and electronic conductivity tests,as well as high-resolution transmission electron microscopy and scanning electron microscopy.The results show that during NIA,theθ′phase exhibits a complex process of nucleation,nucleation and growth,nucleation and growth and coarsening,growth and coarsening,nucleation and growth,and nucleation.NIA treatment imparts a mixed precipitation characteristic on the alloy,which is manifested as coherent precipitates,including GP zones,θ′′phases,small-sizedθ′phases,and semi-coherent or non-coherent precipitates such as large-sizedθ′phases and equilibriumθphases.The simultaneous strengthening and toughening of the NIA-treated 2014 Al alloy is caused by the synergistic effects of the particle-shearing mechanism and Orowan bypassing mechanism.
文摘Effective thermal management is paramount for successfully deploying lithium-ion batteries in residential settings as storage systems for the exploitation of renewable sources.Uncontrolled temperature increases within battery packs can lead to critical issues such as cell overheating,potentially culminating in thermal runaway events and,in extreme cases,leading to fire or explosions.Thiswork presents a comprehensive numerical thermalmodel of a battery pack made of prototype pouch cells based on lithium ferrophosphate(LFP)chemistry.The multi-physical model is specifically developed to investigate real-world operating scenarios and to assess safety considerations.The considered energy storage system is a battery designed for residential applications,in its integration with a photovoltaic(PV)installation.The actual electrochemical behavior of the prototype cell during the charging and discharging processes is modeled and validated on the ground of experimental data.The essential steps leading to the numerical schematization of the battery pack are then presented to apply themodel to two different use scenarios,differing for the user loads.The first scenario corresponds to a typical residential load,with standby lights being active during the night,solar generation with its peak at noon,and appliance use shifting in the afternoon and the evening.In the second scenario,a double demand for energy is present thatmakes the battery never reach 100%of the State of Charge(SoC)and dischargemore rapidly with respect to what occurs under the first scenario.Comparing the simulated temperature with the assumed C-rate,namely the charge or discharge current divided by the battery nominal capacity,it is found that peaks coincide with the charging phase;subsequently,the current tends to a zero value,and consequently,the temperature suddenly reaches the value of the environment.Finally,the model is also utilized to simulate a condition of thermal runaway by introducing critical conditions within a specific pouch cell.In this simulation,the thermal exchange between the cell in thermal runaway and the rest of the system remains within acceptable limits.This occurs due to the short duration of the process and to the module casing coated with an insulating material.The work provides an essential foundation for conducting numerical simulations of battery packs operating also at higher power levels.
基金funded by the Innovative Research Group project of the National Natural Science Foundation of China(52373003).
文摘This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carbon fibers T700SC(SCF)within a temperature range of 330375℃.The research focuses on the PN75 monomer and DCBA blend reinforced SCF composites with varying SCF content,examining mass loss and changes in flexural strength after thermal aging for 50 h(h).Results show that the SCF-reinforced composites based on the PN75/DCBA blend consistently outperform the neat blend in flexural strength,both at room temperature and after thermal aging.The introduction of the SCF significantly improves the composites'thermal stability and mechanical retention,with higher SCF content correlating to better performance.Notably,after aging at 350℃,the SCF-reinforced composites based(30%(mass)SCF)retained 88.8%of its flexural strength,compared to 61.1%for the neat blend.Morphological analysis reveals that while thermal aging causes degradation of the PN75/DCBA blend layer on SCF surfaces,the overall composite structure maintains good mechanical properties up to 350℃.At 375℃,significant degradation occurs,yet the composites still retain flexural strengths above 78 MPa.This study demonstrates the potential of the SCF-reinforced composites based on PN75/DCBA blend for high-temperature applications,establishing their upper-temperature limit for long-term use in oxidative environments.
基金the support of the National Natural Science Foundation of China(Grant Nos.42030714,42177138 and 41907239).
文摘Investigation of thermal effects on the strain rate-dependent properties of compacted bentonite is crucial for the long-term safety assessment of deep geological repository for disposal of high-level radioactive waste.In the present work,cylindrical GMZ01 bentonite specimens were compacted with suction-controlled by the vapor equilibrium technique.Then,a series of temperature-and suction-controlled stepwise constant rate of strain(CRS)tests was performed and the rate-dependent compressibility behavior of the highly compacted GMZ01 bentonite was investigated.The plastic compressibility parameterλ,the elastic compressibility parameterκ,the yield stress p0,as well as the viscous parameterαwere determined.Results indicate thatλ,κandαdecrease and p0 increases as suction increases.Upon heating,parametersλ,αand p0 decrease.It is also found that p0 increases linearly with increasing CRS in a double-logarithm coordinate.Based on the experimental results,a viscosity parameterα(s,T)was fitted to capture the effects of suction s and temperature T on the relationship between yield stress and strain rate.Then,an elastic-thermo-viscoplastic model for unsaturated soils was developed to describe the thermal effects on the rate-dependent behavior of highly compacted GMZ01 bentonite.Validation showed that the calculated results agreed well to the measured ones.
文摘Behavior recognition of Hu sheep contributes to their intensive and intelligent farming.Due to the generally high density of Hu sheep farming,severe occlusion occurs among different behaviors and even among sheep performing the same behavior,leading to missing and false detection issues in existing behavior recognition methods.A high-low frequency aggregated attention and negative sample comprehensive score loss and comprehensive score soft non-maximum suppression-YOLO(HLNC-YOLO)was proposed for identifying the behavior of Hu sheep,addressing the issues of missed and erroneous detections caused by occlusion between Hu sheep in intensive farming.Firstly,images of four typical behaviors-standing,lying,eating,and drinking-were collected from the sheep farm to construct the Hu sheep behavior dataset(HSBD).Next,to solve the occlusion issues,during the training phase,the C2F-HLAtt module was integrated,which combined high-low frequency aggregation attention,into the YOLO v8 Backbone to perceive occluded objects and introduce an auxiliary reversible branch to retain more effective features.Using comprehensive score regression loss(CSLoss)to reduce the scores of suboptimal boxes and enhance the comprehensive scores of occluded object boxes.Finally,the soft comprehensive score non-maximal suppression(Soft-CS-NMS)algorithm filtered prediction boxes during the inferencing.Testing on the HSBD,HLNC-YOLO achieved a mean average precision(mAP@50)of 87.8%,with a memory footprint of 17.4 MB.This represented an improvement of 7.1,2.2,4.6,and 11 percentage points over YOLO v8,YOLO v9,YOLO v10,and Faster R-CNN,respectively.Research indicated that the HLNC-YOLO accurately identified the behavior of Hu sheep in intensive farming and possessed generalization capabilities,providing technical support for smart farming.
