The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries.Investigating the combustion and explosion hazards of lithium-ion ba...The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries.Investigating the combustion and explosion hazards of lithium-ion batteries vent gas can provide guidance for rescue and protection in explosion accidents in energy storage stations and new energy vehicles,thereby promoting the application and development of lithium-ion batteries.Based on this understanding and combined with previous research on gas production from lithium-ion batteries,this article conducted a study on the combustion and explosion risks of vent gas from thermal runaway of 18650 LFP batteries with different states of charge(SOCs).The explosion limit of mixed gases affected by carbon dioxide inert gas is calculated through the“elimination”method,and the Chemkin-Pro software is used to numerically simulate the laminar flame speed and adiabatic flame temperature of the battery vent gas.And the concentration of free radicals and sensitivity coefficients of major elementary reactions in the system are analyzed to comprehensively evaluate the combustion explosion hazard of battery vent gas.The study found that the 100%SOC battery has the lowest explosion limit of the vent gas.The inhibitory elementary reaction sensitivity coefficient in the reaction system is lower and the concentration of free radicals is higher.Therefore,it has the maximum laminar flame speed and adiabatic flame temperature.The combustion and explosion hazard of battery vent gas increases with the increase of SOC,and the risk of explosion is the greatest and most harmful when SOC reaches 100%.However,the related hazards decrease to varying degrees with overcharging of the battery.This article provides a feasible method for analyzing the combustion mechanism of vent gas from lithium-ion batteries,revealing the impact of SOC on the hazardousness of battery vent gas.It provides references for the safety of storage and transportation of lithium-ion batteries,safety protection of energy storage stations,and the selection of related fire extinguishing agents.展开更多
The evolution of hardness and microstructures of 1050 aluminum alloy prepared by hot rolling and subsequent equal- channel angular pressing at cryogenic temperature (cryoECAP) after annealing at 150?400 °C for 1 ...The evolution of hardness and microstructures of 1050 aluminum alloy prepared by hot rolling and subsequent equal- channel angular pressing at cryogenic temperature (cryoECAP) after annealing at 150?400 °C for 1 h without and with magnetic field of 12 T was investigated. The electron back scattering diffraction pattern (EBSD) and transmission electron microscopy (TEM) were utilized to characterize the grain microstructures and dislocations. It is demonstrated that the hot rolling before cryoECAP produces more equiaxed grains with a smaller average size and a higher fraction of high angle boundaries (HABs) in the subsequent cryoECAPed 1050 aluminum alloy, thus accelerating the recovery and recrystallization of cryoECAPed alloy and produces more homogeneous microstructure during annealing. The magnetic field promotes the recovery and recrystallization and leads to much lower hardness at 150?250 °C, while it can suppress the abnormal grain growth and form more homogeneous grain size distributions annealed at 300?400 °C.展开更多
50%diamond particle (5μm) reinforced 2024 aluminum matrix (diamond/2024 Al) composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, ...50%diamond particle (5μm) reinforced 2024 aluminum matrix (diamond/2024 Al) composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion (CTE) of diamond/2024 Al composites was about 8.5×10-6 °C-1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/2024 Al composites was about 100 W/(m?K), and it was slightly increased after annealing while decreased after aging treatment.展开更多
Magnesium carbonate whisker as precursor was prepared from the low-grade magnesite tailings by the route of calcination, hydration, carbonation and thermal decomposition, and then MgO whisker was prepared by calcining...Magnesium carbonate whisker as precursor was prepared from the low-grade magnesite tailings by the route of calcination, hydration, carbonation and thermal decomposition, and then MgO whisker was prepared by calcining the precursor. In addition, the effect of MgO whisker addition on sintering and thermal shock resistance of refractory was also investigated. The results show that the thermal decomposition product is MgCO3·3H2O and its morphology is remarkably influenced by the types of additives, and magnesium carbonate whisker with the length of 10-60 μm and length-diameter ratio of 10-20 is successfully prepared when a type of soluble magnesium salt is added. MgO whisker with the length of 10-40 μm is derived from precursor with the heating rate of 1 ℃/min. The thermal shock resistance of refractory is significantly improved by the addition of MgO whisker due to its effect on binding and preventing crack expanding, and the proper amount of whisker addition is around 3%.展开更多
Numerous coal fires burn underneath the Datong coalfield because of indiscriminate mining.Landsat TM/ETM,unmanned aerial vehicle(UAV),and infrared thermal imager were employed to monitor underground coal fires in th...Numerous coal fires burn underneath the Datong coalfield because of indiscriminate mining.Landsat TM/ETM,unmanned aerial vehicle(UAV),and infrared thermal imager were employed to monitor underground coal fires in the Majiliang mining area.The thermal field distributions of this area in 2000,2002,2006,2007,and 2009 were obtained using Landsat TM/ETM.The changes in the distribution were then analyzed to approximate the locations of the coal fires.Through UAV imagery employed at a very high resolution(0.2 m),the texture information,linear features,and brightness of the ground fissures in the coal fire area were determined.All these data were combined to build a knowledge model of determining fissures and were used to support underground coal fire detection.An infrared thermal imager was used to map the thermal field distribution of areas where coal fire is serious.Results were analyzed to identify the hot spot trend and the depth of the burning point.展开更多
Pre-compression and heat treatment were performed on an extruded AZ31 Mg alloy,and their effects on subsequent deformation behavior were investigated.The results show that at low temperature annealing(170 ℃ for 4 h),...Pre-compression and heat treatment were performed on an extruded AZ31 Mg alloy,and their effects on subsequent deformation behavior were investigated.The results show that at low temperature annealing(170 ℃ for 4 h),the extruded samples with and without annealing exhibit a nearly equivalent yield stress(~148 MPa) because their microstructures are nearly unchanged.However,under the same annealing condition,the yield stress of sample with pre-twinning and subsequent annealing(~225 MPa) is higher than that of the pre-twinned one(~200 MPa).The former sample presents a hardening effect because the solute atoms segregated on twin boundaries lead to a strengthening effect.The pre-twinned sample annealed at 400 ℃ for 1 h shows a higher ultimate elongation(~28%) than the pre-twinned one(~15%),but its yield stress(~125 MPa) is much lower than that of the pre-twinned one(~200 MPa).展开更多
The powders of Mo2FeB2 cermet were prepared with Mo powders, Fe-B alloy powders and Fe powders as raw materials. Mo2FeB2 cermet coatings were prepared on Q235 steel by reactive thermal spraying (RTS) method and heat...The powders of Mo2FeB2 cermet were prepared with Mo powders, Fe-B alloy powders and Fe powders as raw materials. Mo2FeB2 cermet coatings were prepared on Q235 steel by reactive thermal spraying (RTS) method and heated at 1 000 ℃ in vacuum oven of 1 kPa for 5 h. The properties of coatings were investigated. The results indicate that Fe2B appears after milling for 15 h in the powder at room temperature, a part of ternary borides (Mo2FeB2) are generated in powder sintered at 900 ℃. The coatings are composed of the major phases Mo2FeB2 and a-Fe, a little of Fe203, FeO and some pores. The bonding strength between the substrate and the ceramic coating is 32.73 MPa, the thermal-shock times is about 43 and the wear resistance is enhanced by approximately 5.28 times compared with that of the substrate, respectively. The comprehensive properties of Mo2FeB2 cermet coatings can be imoroved further after vacuum heat-treatment at 1 000 ℃ for 5 h.展开更多
[Objective] This study aimed to establish a determination method for iprobenfos residue in rice straw and husked rice. [Method] The rice straw and husked rice samples were extracted by acetone-ethyl acetate mixed solv...[Objective] This study aimed to establish a determination method for iprobenfos residue in rice straw and husked rice. [Method] The rice straw and husked rice samples were extracted by acetone-ethyl acetate mixed solvent. The extracts were purified using SPE C18 column and SPE NH2 column, and the iprobenfos residues were determined by GC-FTD. [Result] In the concentration range of 0.005-5.0 mg/kg, iprobenfos concentration showed a good linear relationship with peak area (r=0.999 8). When the iprobenfos concentrations were 0.01, 0.1 and 1.0 mg/kg respectively, the recoveries of added iprobenfos from rice straw ranged from 72.6% to 99.7% with relative standard deviation ranging from 5.65% to 8.48%; the recoveries of added iprobenfos from husked rice ranged from 81.6% to 97.6% with relative standard deviation ranging from 3.74% to 7.63%. The minimum detectable quantity of iprobenfos was 5×10^-12 g, and the minimum detectable concentrations of iprobenfos in rice straw and husked rice samples were 2.0 and 0.5 μg/kg, respec- tively. [Conclusion] The established determination method is characterized by low de- termination limit, high sensitivity, good reproducibility and high operability, which all meet the requirements by Guideline on Pesticide Residue Trials of the Ministry of Agriculture.展开更多
Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2(x=0,1,3,5) bulk metallic glasses were investigated.The Fe41Co7-xNixCr15Mo14C15B6Y2(x=0,1,3,5) ...Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2(x=0,1,3,5) bulk metallic glasses were investigated.The Fe41Co7-xNixCr15Mo14C15B6Y2(x=0,1,3,5) metallic glasses were fabricated by copper mold casting method.The thermal stability and crystallization behavior of the metallic glass rods were investigated by differential scanning calorimetry and isothermal experiments.Hardness measurements for samples annealed at different temperatures for different time were carried out at room temperature by the Vickers hardness tester,and magnetic measurements were performed at different temperatures by the vibrating sample magnetometer.It is shown that the addition of Ni does not play a positive role for enlarging ΔTx and GFA from parameter γ(=Tx/(Tg+Tl)),and it can,however,increase the activation energy in the initial stage of crystallization by changing the initial crystallization behavior.The minor addition of Ni can refine the crystal grain obtained from the full crystallization experiment.The primary crystallization causes the decrease of hardness in these alloys,and as the crystallization continues,the hardness in all samples increases instead due to the precipitation of carbide and boride.The annealing temperature has an obvious effect on magnetic properties of these alloys,and the minor addition of Ni can effectively prevent the alloy annealed at high temperature to transform from paramagnetic to ferromagnetic state.展开更多
The investigation on proton irradiation and thermal annealing of AlGaAs/GaAs solar cells has been reported.The energy of the proton irradiation is 325keV and the fluences are ranging from 5×10 10 to 1×1...The investigation on proton irradiation and thermal annealing of AlGaAs/GaAs solar cells has been reported.The energy of the proton irradiation is 325keV and the fluences are ranging from 5×10 10 to 1×10 13 cm -2 .It is demonstrated that the irradiation-induced degradation in the photovoltaic performance of the solar cells exists mainly in the short circuit current and the irradiation damage can be partly recovered by low temperature annealing at 200℃.In addition,it is found that the borosilicate cover glass has an obvious protection effect against the proton irradiation.展开更多
We report a facile approach to water-dispersible polydiacetylene/rare earth ions nanocomposites with reversible thermochromism. The nanocomposites were prepared by doping rare earth ions Dy^3+ or Sin^3+ into layer-s...We report a facile approach to water-dispersible polydiacetylene/rare earth ions nanocomposites with reversible thermochromism. The nanocomposites were prepared by doping rare earth ions Dy^3+ or Sin^3+ into layer-structured 10,12-pentacosadiynoic acid (PCDA) nanopar- ticles to obtain PCDA/rare earth ions nanocomposites (PCDA-RE) and subsequently annealing PCDA-RE at the temperature slightly higher than the melting point of pure PCDA crystals, followed by topochemically polymerizing the annealed PCDA-RE. The polymerized PCDA-RE, i.e. poly(10,12-pentacosadiynoic acid)/rare earth ions nanocomposites (PDARE: PDA-Dy or PDA-Sm), are largely reversible (PDA-Sm) or even completely reversible (PDA-Dy) in the thermochromism, while, without the doping, pure PDA is completely irreversible. It is confirmed that, PDA-RE are also layer-structured with a d-spacing of 5.4 nm, higher than the d-spacing of pure PDA (4.7 nm). In PDA-RE, the rare earth ions form a layer in-between and interact strongly with the PDA bilayers, being responsible for the high degree or even the complete reversibility. This is the first example to make PDA completely reversible through the doping of rare earth ions; the annealing process is essential for the complete reversibility since it removes any defects in the structure.展开更多
The chemical compositions and microstructures of the armor strips excavated from the Emperor Qin Shi Huang's mausoleum were examined systematically by using optical microscopy and electron microscopy.It was found ...The chemical compositions and microstructures of the armor strips excavated from the Emperor Qin Shi Huang's mausoleum were examined systematically by using optical microscopy and electron microscopy.It was found that the armor strips were made of pure copper.Based on the morphology of α-Cu recrystal grain and copper sulphide(Cu2S) inclusions in the armor strips,the manufacturing techniques were proposed as follows:smelting pure copper,casting a lamellar plate,forming the cast ingots into sheets through repeated cold forging combined with annealing heat treatment,and finally cutting the sheets into filaments.Furthermore,through the deformation of copper sulphide(Cu2S) inclusions in the strips,the work rate during forging was evaluated and calculated to be close to 75%.展开更多
This paper describes a mathematical model developed to study the behavior of liquefied petroleum gas (LPG) tanks when subjected to jet fire. The model consists of a number of field and zone sub-models which are used t...This paper describes a mathematical model developed to study the behavior of liquefied petroleum gas (LPG) tanks when subjected to jet fire. The model consists of a number of field and zone sub-models which are used to simulate the various physical phenomena taking place during the tank engulfment period. The model can be used to predict the pressure and temperature of the LPG in the tank, the temperature of the wall of tank, and the time of tank explosion. The comparisons between the model predicted results and the test data show good agreement. The results show that the jet fire partially impinging on tank wall led to higher wall temperature and the time to failure was shorter than that in engulfing pool fire. And the exposure of the upper wall in the vapor zone to the fire is more dangerous than that of the LPG contacted wall.展开更多
By analyzing the characteristics of combustion and billet heating process, a 3-D transient computer fluid dynamic simulation system based on commercial software CFX4.3 and some self-programmed codes were developed to ...By analyzing the characteristics of combustion and billet heating process, a 3-D transient computer fluid dynamic simulation system based on commercial software CFX4.3 and some self-programmed codes were developed to simulate the thermal process in a continuous heating furnace using high temperature air combustion technology. The effects of different switching modes on injection entrancement of multi burners, combustion and billet heating process in furnace were analyzed numerically, and the computational results were compared with on-site measurement, which verified the practicability of this numerical simulation system. The results indicate that the flow pattern and distribution of temperature in regenerative reheating furnace with partial same-side-switching combustion mode are favorable to satisfy the high quality requirements of reheating, in which the terminal heating temperature of billets is more than 1 460 K and the temperature difference between two nodes is not more than 10 K. But since the surface average temperature of billets apart fi'om heating zone is only about 1 350 K and continued heating is needed in soaking zone, the design and operation of current state are still needed to be optimized to improve the temperature schedule of billet heating. The distribution of velocity and temperature in regenerative reheating furnace with same-side-switching combustion mode cannot satisfy the even and fast heating process. The terminal heating temperature of billets is lower than that of the former case by 30 K. The distribution of flow and temperature can be improved by using cross-switching combustion mode, whose terminal temperature of billets is about 1 470 K with small temperature difference within 10 K.展开更多
WT8.BZ]The effects of postgrowth rapid thermal annealing have been studied on the optical properties of 3-nm-height InAs/GaAs quantum dots covered by 3-nm-thick In xGa 1-x As (x=0,0 1 and 0 2) overgrowth layer...WT8.BZ]The effects of postgrowth rapid thermal annealing have been studied on the optical properties of 3-nm-height InAs/GaAs quantum dots covered by 3-nm-thick In xGa 1-x As (x=0,0 1 and 0 2) overgrowth layer.At a higher annealing temperature (T≥750℃),the photoluminescence peak of InGaAs layer has been observed at the lower-energy side of InAs quantum-dot peak.In addition,a similar blueshift in photoluminescence (PL) emission energy is observed for all samples when the annealing temperature increases from 650 to 850℃.However,the trend of photoluminescence linewidth towards narrowing is totally different for InAs quantum dots with different In mole fraction in InGaAs overgrowth layer.The results suggest that the intermixing in the lateral direction plays an important role in obtaining a better understanding of the modification of optical properties induced by the rapid thermal annealing.展开更多
The morphous silicon films prepared by PECVD at substrate temperatures of 30℃ have been crystallized by rapid thermal annealing method, the budget of time-temperature in the annealing process is 600℃ for 120s, 850℃...The morphous silicon films prepared by PECVD at substrate temperatures of 30℃ have been crystallized by rapid thermal annealing method, the budget of time-temperature in the annealing process is 600℃ for 120s, 850℃ for 120s, and 950℃ for 120s. The results indicate the crystallization at 850℃ and 950℃ are better as shown in micro-Raman scattering and scanning electronic microscope.展开更多
The purpose of this paper is to investigate the feasibility of high-frequency induction heat for the line heating process through a series of experimental studies and numerical calculations. The results show that the ...The purpose of this paper is to investigate the feasibility of high-frequency induction heat for the line heating process through a series of experimental studies and numerical calculations. The results show that the heating temperature of induction heating meets the demands of steel plate bending, and the deformation of a steel plate heated by induction heating can achieve the same effect as flame heating. Meanwhile, the finite element model of moving induction heating of the plate is developed, and the comparison of the residual strain fields and transverse shrinkage between these two kinds of heating shows that great similarity has been achieved.展开更多
According to inverse heat transfer theory, the evolutions of synthetic surface heat transfer coefficient(SSHTC) of the quenching surface of 7B50 alloy during water-spray quenching were simulated by the Pro CAST soft...According to inverse heat transfer theory, the evolutions of synthetic surface heat transfer coefficient(SSHTC) of the quenching surface of 7B50 alloy during water-spray quenching were simulated by the Pro CAST software based on accurate cooling curves measured by the modified Jominy specimen and temperature-dependent thermo-physical properties of 7 B50 alloy calculated using the JMat Pro software. Results show that the average cooling rate at 6 mm from the quenching surface and 420-230 ℃(quench sensitive temperature range) is 45.78℃/s. The peak-value of the SSHTC is 69 kW/(m^2·K) obtained at spray quenching for 0.4 s and the corresponding temperature of the quenching surface is 160 ℃. In the initial stage of spray quenching, the phenomenon called "temperature plateau" appears on the cooling curve of the quenching surface. The temperature range of this plateau is 160-170℃ with the duration about 3 s. During the temperature plateau, heat transfer mechanism of the quenching surface transforms from nucleate boiling regime to single-phase convective regime.展开更多
基金supported by the National Natural Science Foundation of China(52106284)the Natural Science Foundation of Hebei Province(B2021507001)support of Project to Promote Innovation in Doctoral Research at CPPU(BSKY202302).
文摘The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries.Investigating the combustion and explosion hazards of lithium-ion batteries vent gas can provide guidance for rescue and protection in explosion accidents in energy storage stations and new energy vehicles,thereby promoting the application and development of lithium-ion batteries.Based on this understanding and combined with previous research on gas production from lithium-ion batteries,this article conducted a study on the combustion and explosion risks of vent gas from thermal runaway of 18650 LFP batteries with different states of charge(SOCs).The explosion limit of mixed gases affected by carbon dioxide inert gas is calculated through the“elimination”method,and the Chemkin-Pro software is used to numerically simulate the laminar flame speed and adiabatic flame temperature of the battery vent gas.And the concentration of free radicals and sensitivity coefficients of major elementary reactions in the system are analyzed to comprehensively evaluate the combustion explosion hazard of battery vent gas.The study found that the 100%SOC battery has the lowest explosion limit of the vent gas.The inhibitory elementary reaction sensitivity coefficient in the reaction system is lower and the concentration of free radicals is higher.Therefore,it has the maximum laminar flame speed and adiabatic flame temperature.The combustion and explosion hazard of battery vent gas increases with the increase of SOC,and the risk of explosion is the greatest and most harmful when SOC reaches 100%.However,the related hazards decrease to varying degrees with overcharging of the battery.This article provides a feasible method for analyzing the combustion mechanism of vent gas from lithium-ion batteries,revealing the impact of SOC on the hazardousness of battery vent gas.It provides references for the safety of storage and transportation of lithium-ion batteries,safety protection of energy storage stations,and the selection of related fire extinguishing agents.
基金Project(2011CB606403)supported by the State Basic Research Development Program of ChinaProjects(51171044,51174058)supported by the National Natural Science Foundation of ChinaProject(2012CB723307)supported by the State Basic Research Development Program of China
文摘The evolution of hardness and microstructures of 1050 aluminum alloy prepared by hot rolling and subsequent equal- channel angular pressing at cryogenic temperature (cryoECAP) after annealing at 150?400 °C for 1 h without and with magnetic field of 12 T was investigated. The electron back scattering diffraction pattern (EBSD) and transmission electron microscopy (TEM) were utilized to characterize the grain microstructures and dislocations. It is demonstrated that the hot rolling before cryoECAP produces more equiaxed grains with a smaller average size and a higher fraction of high angle boundaries (HABs) in the subsequent cryoECAPed 1050 aluminum alloy, thus accelerating the recovery and recrystallization of cryoECAPed alloy and produces more homogeneous microstructure during annealing. The magnetic field promotes the recovery and recrystallization and leads to much lower hardness at 150?250 °C, while it can suppress the abnormal grain growth and form more homogeneous grain size distributions annealed at 300?400 °C.
基金Project (AWJ-M13-15) supported by the Open Fund of State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology,China
文摘50%diamond particle (5μm) reinforced 2024 aluminum matrix (diamond/2024 Al) composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion (CTE) of diamond/2024 Al composites was about 8.5×10-6 °C-1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/2024 Al composites was about 100 W/(m?K), and it was slightly increased after annealing while decreased after aging treatment.
基金Projects(50874130,50974034)supported by the National Natural Science Foundation of ChinaProject(FMRU2008K01)supported by the Open Research Fund of Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education,Wuhan University of Science and Technology,China
文摘Magnesium carbonate whisker as precursor was prepared from the low-grade magnesite tailings by the route of calcination, hydration, carbonation and thermal decomposition, and then MgO whisker was prepared by calcining the precursor. In addition, the effect of MgO whisker addition on sintering and thermal shock resistance of refractory was also investigated. The results show that the thermal decomposition product is MgCO3·3H2O and its morphology is remarkably influenced by the types of additives, and magnesium carbonate whisker with the length of 10-60 μm and length-diameter ratio of 10-20 is successfully prepared when a type of soluble magnesium salt is added. MgO whisker with the length of 10-40 μm is derived from precursor with the heating rate of 1 ℃/min. The thermal shock resistance of refractory is significantly improved by the addition of MgO whisker due to its effect on binding and preventing crack expanding, and the proper amount of whisker addition is around 3%.
基金Project(201412016)supported by the Special Fund for Public Projects of National Administration of Surveying,Mapping and Geoinformation of ChinaProject(51174287)supported by the National Natural Science Foundation of China
文摘Numerous coal fires burn underneath the Datong coalfield because of indiscriminate mining.Landsat TM/ETM,unmanned aerial vehicle(UAV),and infrared thermal imager were employed to monitor underground coal fires in the Majiliang mining area.The thermal field distributions of this area in 2000,2002,2006,2007,and 2009 were obtained using Landsat TM/ETM.The changes in the distribution were then analyzed to approximate the locations of the coal fires.Through UAV imagery employed at a very high resolution(0.2 m),the texture information,linear features,and brightness of the ground fissures in the coal fire area were determined.All these data were combined to build a knowledge model of determining fissures and were used to support underground coal fire detection.An infrared thermal imager was used to map the thermal field distribution of areas where coal fire is serious.Results were analyzed to identify the hot spot trend and the depth of the burning point.
基金Project(XDJK2013C106)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(51201140)supported by the National Natural Science Foundation of China
文摘Pre-compression and heat treatment were performed on an extruded AZ31 Mg alloy,and their effects on subsequent deformation behavior were investigated.The results show that at low temperature annealing(170 ℃ for 4 h),the extruded samples with and without annealing exhibit a nearly equivalent yield stress(~148 MPa) because their microstructures are nearly unchanged.However,under the same annealing condition,the yield stress of sample with pre-twinning and subsequent annealing(~225 MPa) is higher than that of the pre-twinned one(~200 MPa).The former sample presents a hardening effect because the solute atoms segregated on twin boundaries lead to a strengthening effect.The pre-twinned sample annealed at 400 ℃ for 1 h shows a higher ultimate elongation(~28%) than the pre-twinned one(~15%),but its yield stress(~125 MPa) is much lower than that of the pre-twinned one(~200 MPa).
基金Project(2007T069)supported by Liaoning Education Department Innovation Team,China
文摘The powders of Mo2FeB2 cermet were prepared with Mo powders, Fe-B alloy powders and Fe powders as raw materials. Mo2FeB2 cermet coatings were prepared on Q235 steel by reactive thermal spraying (RTS) method and heated at 1 000 ℃ in vacuum oven of 1 kPa for 5 h. The properties of coatings were investigated. The results indicate that Fe2B appears after milling for 15 h in the powder at room temperature, a part of ternary borides (Mo2FeB2) are generated in powder sintered at 900 ℃. The coatings are composed of the major phases Mo2FeB2 and a-Fe, a little of Fe203, FeO and some pores. The bonding strength between the substrate and the ceramic coating is 32.73 MPa, the thermal-shock times is about 43 and the wear resistance is enhanced by approximately 5.28 times compared with that of the substrate, respectively. The comprehensive properties of Mo2FeB2 cermet coatings can be imoroved further after vacuum heat-treatment at 1 000 ℃ for 5 h.
基金Supported by Pesticide Registration Residual Test of Institute for the Control of Agrochemicals,Ministry of Agriculture(2013F216)~~
文摘[Objective] This study aimed to establish a determination method for iprobenfos residue in rice straw and husked rice. [Method] The rice straw and husked rice samples were extracted by acetone-ethyl acetate mixed solvent. The extracts were purified using SPE C18 column and SPE NH2 column, and the iprobenfos residues were determined by GC-FTD. [Result] In the concentration range of 0.005-5.0 mg/kg, iprobenfos concentration showed a good linear relationship with peak area (r=0.999 8). When the iprobenfos concentrations were 0.01, 0.1 and 1.0 mg/kg respectively, the recoveries of added iprobenfos from rice straw ranged from 72.6% to 99.7% with relative standard deviation ranging from 5.65% to 8.48%; the recoveries of added iprobenfos from husked rice ranged from 81.6% to 97.6% with relative standard deviation ranging from 3.74% to 7.63%. The minimum detectable quantity of iprobenfos was 5×10^-12 g, and the minimum detectable concentrations of iprobenfos in rice straw and husked rice samples were 2.0 and 0.5 μg/kg, respec- tively. [Conclusion] The established determination method is characterized by low de- termination limit, high sensitivity, good reproducibility and high operability, which all meet the requirements by Guideline on Pesticide Residue Trials of the Ministry of Agriculture.
基金Project(2012CB825700) supported by the National Basic Research Program of China
文摘Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2(x=0,1,3,5) bulk metallic glasses were investigated.The Fe41Co7-xNixCr15Mo14C15B6Y2(x=0,1,3,5) metallic glasses were fabricated by copper mold casting method.The thermal stability and crystallization behavior of the metallic glass rods were investigated by differential scanning calorimetry and isothermal experiments.Hardness measurements for samples annealed at different temperatures for different time were carried out at room temperature by the Vickers hardness tester,and magnetic measurements were performed at different temperatures by the vibrating sample magnetometer.It is shown that the addition of Ni does not play a positive role for enlarging ΔTx and GFA from parameter γ(=Tx/(Tg+Tl)),and it can,however,increase the activation energy in the initial stage of crystallization by changing the initial crystallization behavior.The minor addition of Ni can refine the crystal grain obtained from the full crystallization experiment.The primary crystallization causes the decrease of hardness in these alloys,and as the crystallization continues,the hardness in all samples increases instead due to the precipitation of carbide and boride.The annealing temperature has an obvious effect on magnetic properties of these alloys,and the minor addition of Ni can effectively prevent the alloy annealed at high temperature to transform from paramagnetic to ferromagnetic state.
文摘The investigation on proton irradiation and thermal annealing of AlGaAs/GaAs solar cells has been reported.The energy of the proton irradiation is 325keV and the fluences are ranging from 5×10 10 to 1×10 13 cm -2 .It is demonstrated that the irradiation-induced degradation in the photovoltaic performance of the solar cells exists mainly in the short circuit current and the irradiation damage can be partly recovered by low temperature annealing at 200℃.In addition,it is found that the borosilicate cover glass has an obvious protection effect against the proton irradiation.
基金V.ACKNOWLEDGEMENTSThisworkwassupportedbytheNationalNatu-ralScienceFoundationofChina(No.21334001andNo.91127030).V. ACKNOWLEDGEMENTS This work was supported by the National Natu- ral Science Foundation of China (No.21334001 and No.91127030).
文摘We report a facile approach to water-dispersible polydiacetylene/rare earth ions nanocomposites with reversible thermochromism. The nanocomposites were prepared by doping rare earth ions Dy^3+ or Sin^3+ into layer-structured 10,12-pentacosadiynoic acid (PCDA) nanopar- ticles to obtain PCDA/rare earth ions nanocomposites (PCDA-RE) and subsequently annealing PCDA-RE at the temperature slightly higher than the melting point of pure PCDA crystals, followed by topochemically polymerizing the annealed PCDA-RE. The polymerized PCDA-RE, i.e. poly(10,12-pentacosadiynoic acid)/rare earth ions nanocomposites (PDARE: PDA-Dy or PDA-Sm), are largely reversible (PDA-Sm) or even completely reversible (PDA-Dy) in the thermochromism, while, without the doping, pure PDA is completely irreversible. It is confirmed that, PDA-RE are also layer-structured with a d-spacing of 5.4 nm, higher than the d-spacing of pure PDA (4.7 nm). In PDA-RE, the rare earth ions form a layer in-between and interact strongly with the PDA bilayers, being responsible for the high degree or even the complete reversibility. This is the first example to make PDA completely reversible through the doping of rare earth ions; the annealing process is essential for the complete reversibility since it removes any defects in the structure.
文摘The chemical compositions and microstructures of the armor strips excavated from the Emperor Qin Shi Huang's mausoleum were examined systematically by using optical microscopy and electron microscopy.It was found that the armor strips were made of pure copper.Based on the morphology of α-Cu recrystal grain and copper sulphide(Cu2S) inclusions in the armor strips,the manufacturing techniques were proposed as follows:smelting pure copper,casting a lamellar plate,forming the cast ingots into sheets through repeated cold forging combined with annealing heat treatment,and finally cutting the sheets into filaments.Furthermore,through the deformation of copper sulphide(Cu2S) inclusions in the strips,the work rate during forging was evaluated and calculated to be close to 75%.
文摘This paper describes a mathematical model developed to study the behavior of liquefied petroleum gas (LPG) tanks when subjected to jet fire. The model consists of a number of field and zone sub-models which are used to simulate the various physical phenomena taking place during the tank engulfment period. The model can be used to predict the pressure and temperature of the LPG in the tank, the temperature of the wall of tank, and the time of tank explosion. The comparisons between the model predicted results and the test data show good agreement. The results show that the jet fire partially impinging on tank wall led to higher wall temperature and the time to failure was shorter than that in engulfing pool fire. And the exposure of the upper wall in the vapor zone to the fire is more dangerous than that of the LPG contacted wall.
基金Project(20010533009) supported by the Special Foundation for Doctorate Discipline of China
文摘By analyzing the characteristics of combustion and billet heating process, a 3-D transient computer fluid dynamic simulation system based on commercial software CFX4.3 and some self-programmed codes were developed to simulate the thermal process in a continuous heating furnace using high temperature air combustion technology. The effects of different switching modes on injection entrancement of multi burners, combustion and billet heating process in furnace were analyzed numerically, and the computational results were compared with on-site measurement, which verified the practicability of this numerical simulation system. The results indicate that the flow pattern and distribution of temperature in regenerative reheating furnace with partial same-side-switching combustion mode are favorable to satisfy the high quality requirements of reheating, in which the terminal heating temperature of billets is more than 1 460 K and the temperature difference between two nodes is not more than 10 K. But since the surface average temperature of billets apart fi'om heating zone is only about 1 350 K and continued heating is needed in soaking zone, the design and operation of current state are still needed to be optimized to improve the temperature schedule of billet heating. The distribution of velocity and temperature in regenerative reheating furnace with same-side-switching combustion mode cannot satisfy the even and fast heating process. The terminal heating temperature of billets is lower than that of the former case by 30 K. The distribution of flow and temperature can be improved by using cross-switching combustion mode, whose terminal temperature of billets is about 1 470 K with small temperature difference within 10 K.
文摘WT8.BZ]The effects of postgrowth rapid thermal annealing have been studied on the optical properties of 3-nm-height InAs/GaAs quantum dots covered by 3-nm-thick In xGa 1-x As (x=0,0 1 and 0 2) overgrowth layer.At a higher annealing temperature (T≥750℃),the photoluminescence peak of InGaAs layer has been observed at the lower-energy side of InAs quantum-dot peak.In addition,a similar blueshift in photoluminescence (PL) emission energy is observed for all samples when the annealing temperature increases from 650 to 850℃.However,the trend of photoluminescence linewidth towards narrowing is totally different for InAs quantum dots with different In mole fraction in InGaAs overgrowth layer.The results suggest that the intermixing in the lateral direction plays an important role in obtaining a better understanding of the modification of optical properties induced by the rapid thermal annealing.
文摘The morphous silicon films prepared by PECVD at substrate temperatures of 30℃ have been crystallized by rapid thermal annealing method, the budget of time-temperature in the annealing process is 600℃ for 120s, 850℃ for 120s, and 950℃ for 120s. The results indicate the crystallization at 850℃ and 950℃ are better as shown in micro-Raman scattering and scanning electronic microscope.
基金Supported by the National Natural Science Foundation of China (50805016)
文摘The purpose of this paper is to investigate the feasibility of high-frequency induction heat for the line heating process through a series of experimental studies and numerical calculations. The results show that the heating temperature of induction heating meets the demands of steel plate bending, and the deformation of a steel plate heated by induction heating can achieve the same effect as flame heating. Meanwhile, the finite element model of moving induction heating of the plate is developed, and the comparison of the residual strain fields and transverse shrinkage between these two kinds of heating shows that great similarity has been achieved.
基金Project(2016YFB0300801)supported by the National Key Research and Development Program of ChinaProject(51371045)supported by the National Natural Science Foundation of China
文摘According to inverse heat transfer theory, the evolutions of synthetic surface heat transfer coefficient(SSHTC) of the quenching surface of 7B50 alloy during water-spray quenching were simulated by the Pro CAST software based on accurate cooling curves measured by the modified Jominy specimen and temperature-dependent thermo-physical properties of 7 B50 alloy calculated using the JMat Pro software. Results show that the average cooling rate at 6 mm from the quenching surface and 420-230 ℃(quench sensitive temperature range) is 45.78℃/s. The peak-value of the SSHTC is 69 kW/(m^2·K) obtained at spray quenching for 0.4 s and the corresponding temperature of the quenching surface is 160 ℃. In the initial stage of spray quenching, the phenomenon called "temperature plateau" appears on the cooling curve of the quenching surface. The temperature range of this plateau is 160-170℃ with the duration about 3 s. During the temperature plateau, heat transfer mechanism of the quenching surface transforms from nucleate boiling regime to single-phase convective regime.