This paper aims to seek expedited fatigue analysis methods using the infrared self-heating technique.The fatigue analysis of NiTi shape memory alloys is obtained through a hybrid approach:fatigue tests to failure yiel...This paper aims to seek expedited fatigue analysis methods using the infrared self-heating technique.The fatigue analysis of NiTi shape memory alloys is obtained through a hybrid approach:fatigue tests to failure yield relatively shorter fatigue lives,while determining the fatigue limit,normally involving extremely high cycles approaching 107 cycles,is directly achieved via self-heating tests.This methodology significantly reduces testing cycles,costing only a fraction of the several-thousand-cycle tests typically required.The validity of this approach is successfully demonstrated through fatigue testing of 18Ni steel:the entire S–N curve is examined using the traditional fatigue test until a life of up to 10^(7) cycles,and the indicated fatigue limit agrees well with the one directly determined through the self-heating method.Subsequently,this developed approach is applied to the fatigue analysis of shape memory alloys under complex loading,enabling the concurrent estimation of the limits of phase transformation-dominated low-cycle fatigue and high-cycle fatigue in the elastic regime on a single specimen.The results obtained align well with other supporting evidence.展开更多
In order to reveal the nonlinear dynamics characteristics of unsteady self-heating process of sulfide ores, nine different kinds of sulfide ore samples from a pyrite mine in China were taken as experimental materials ...In order to reveal the nonlinear dynamics characteristics of unsteady self-heating process of sulfide ores, nine different kinds of sulfide ore samples from a pyrite mine in China were taken as experimental materials and their self-heating characteristics were measured in laboratory. Furthermore, the measured temperature was studied by integrating wavelet transform, nonlinear characteristic parameters extraction and fuzzy comprehensive evaluation. The results indicate that only the ore samples 1, 2, 6 and 9 have obvious self-heating phenomenon, and their self-heating initiative temperatures are 220 ℃, 239 ℃, 220 ℃ and 220 ℃, respectively, which means that they are difficult to produce self-heating under normal mining conditions. The correlation dimension of self-heating process is fraction and the maximum Lyapunov exponent is positive, which means that it is feasible to study the self-heating process based on chaotic dynamics theory. The nonlinearities of self-heating process of these four samples （ore samples 1, 2, 6 and 9） are 0.8227, 0.7521, 0.9401 and 0.8827 respectively and the order of the samples according to these results is： sample 6, sample 9, sample 1, sample 2, which is consistent with the measured results of self-heating characteristics. Therefore, the nonlinearity method can be used to evaluate the self-heating tendency of sulfide ores, and it is an effective verification of the reliability of measured results.展开更多
To obtain intrinsic overcharge boundary and investigate overcharge mechanism,here we propose an innovative method,the step overcharge test,to reduce the thermal crossover and distinguish the overcharge thermal behavio...To obtain intrinsic overcharge boundary and investigate overcharge mechanism,here we propose an innovative method,the step overcharge test,to reduce the thermal crossover and distinguish the overcharge thermal behavior,including 5%state of charge(SOC)with small current overcharge and resting until the temperature equilibrium under adiabatic conditions.The intrinsic thermal response and the self-excitation behaviour are analysed through temperature and voltage changes during the step overcharge period.Experimental results show that the deintercalated state of the cathode is highly correlated to self-heating parasitic reactions.Before reaching the upper limit of Negative/Positive(N/P)ratio,the temperature changes little,the heat generation is significantly induced by the reversible heat(endothermic)and ohmic heat,which could balance each other.Following that the lithium metal is gradually deposited on the surface of the anode and reacts with electrolyte upon overcharge,inducing selfheating side reaction.However,this spontaneous thermal reaction could be“self-extinguished”.When the lithium in cathode is completely deintercalated,the boundary point of overcharge is about 4.7 V(~148%SOC,>40℃),and from this point,the self-heating behaviour could be continuously triggered until thermal runaway(TR)without additional overcharge.The whole static and spontaneous process lasts for 115 h and the side reaction heat is beyond 320,000 J.The continuous self-excitation behavior inside the battery is attributed to the interaction between the highly oxidized cathode and the solvent,which leads to the dissolution of metal ions.The dissolved metal ions destroy the SEI(solid electrolyte interphase)film on the surface of the deposited Li of anode,which induces the thermal reaction between lithium metal and the solvent.The interaction between cathode,the deposited Li of anode,and solvent promotes the temperature of the battery to rise slowly.When the temperature of the battery reaches more than 60℃,the reaction between lithium metal and solvent is accelerated.After the temperature rises rapidly to the melting point of the separator,it triggers the thermal runaway of the battery due to the short circuit of the battery.展开更多
For exploiting advantages of electron beam air plasma in some unusual applications, a Monte Carlo （MC） model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasm...For exploiting advantages of electron beam air plasma in some unusual applications, a Monte Carlo （MC） model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasma by considering the self-heating effect. Based on the model, the electron beam induced temperature field and the related plasma properties are investigated. The results indicate that a nonuniform temperature field is formed in the electron beam plasma region and the average temperature is of the order of 600 K. Moreover, much larger volume pear-shaped electron beam plasma is produced in hot state rather than in cold state. The beam ranges can, with beam energies of 75 keV and 80 keV, exceed 1.0 m and 1.2 m in air at pressure of 100 torr, respectively. Finally, a well verified formula is obtained for calculating the range of high energy electron beam in atmosphere.展开更多
Original surface chemistry of sulphidesis altered upon contact with air, leading to ''oxidation'', which is accompanied by evolution of heat. The current study reports results of an investigation on ex...Original surface chemistry of sulphidesis altered upon contact with air, leading to ''oxidation'', which is accompanied by evolution of heat. The current study reports results of an investigation on extent of exothermicity of an experimental nickel-copper sulphide stockpile that was formed at a mining site in Sudbury, Canada. The ore contained pentlandite and chalcopyrite that are accompanied by a large quantity of pyrrhotite. The self-heating characteristics were recorded by temperature sensors placed inside the stockpile. Ambient conditions such as temperature, humidity, and wind velocity were simultaneously recorded. The inner temperature of the stockpile indicated significant fluctuations due to rapid changes, particularly in the outside temperature. The minimum and maximum temperatures recorded in the outside and inside were 5 and 10.5, 44.3 and 32 ℃, respectively. The self-heating capacity of the sulphide ore stockpile observed represents a mild case compared to that experienced by coals. Possible reasons are discussed.展开更多
The self-heating effect severely limits device performance and reliability.Although some studies have revealed the heat distribution ofβ-Ga_(2)O_(3) MOSFETs under biases,those devices all have small areas and have di...The self-heating effect severely limits device performance and reliability.Although some studies have revealed the heat distribution ofβ-Ga_(2)O_(3) MOSFETs under biases,those devices all have small areas and have difficulty reflecting practical con-ditions.This work demonstrated a multi-fingerβ-Ga_(2)O_(3) MOSFET with a maximum drain current of 0.5 A.Electrical characteris-tics were measured,and the heat dissipation of the device was investigated through infrared images.The relationship between device temperature and time/bias is analyzed.展开更多
CFD models have been developed to investigate the Iongwall goaf gas flow patternsunder different mining and geological control conditions.The Iongwall goaf wastreated as porous regions and gas flow was modelled as a m...CFD models have been developed to investigate the Iongwall goaf gas flow patternsunder different mining and geological control conditions.The Iongwall goaf wastreated as porous regions and gas flow was modelled as a momentum sink added to themomentum equation.Gas desorption from the caved goaf and destressed coal seamswithin the mining disturbed area was modelled as additional mass sources in the continuityequation.These CFD models were developed according to specific Iongwall layoutsand calibrated against field monitoring data.Two case studies were presented demonstratingthe application of CFD modelling of goaf gas flow characteristics for improved goafgas capture and the reduction of oxygen ingress into the goaf areas for self-heating prevention.Results from the case studies indicate that the optimum goaf drainage strategywould be a combination of shallow (near the face) and deep holes to improve the overalldrainage efficiency and gas purity.For gassy Iongwall faces retreating against the seam dip,it is recommended to conduct cross-measure roof hole drainage targeting the fracturedzones overlying the return corner,rather than high capacity surface goaf drainage deep inthe goaf.展开更多
Self-heating effect in amorphous InGaZnO thin-film transistors remains a critical issue that degrades device performance and stability, hindering their wider applications. In this work, pulsed current–voltage analysi...Self-heating effect in amorphous InGaZnO thin-film transistors remains a critical issue that degrades device performance and stability, hindering their wider applications. In this work, pulsed current–voltage analysis has been applied to explore the physics origin of self-heating induced degradation, where Joule heat is shortly accumulated by drain current and dissipated in repeated time cycles as a function of gate bias. Enhanced positive threshold voltage shift is observed at reduced heat dissipation time, higher drain current, and increased gate width. A physical picture of Joule heating assisted charge trapping process has been proposed and then verified with pulsed negative gate bias stressing scheme, which could evidently counteract the self-heating effect through the electric-field assisted detrapping process. As a result, this pulsed gate bias scheme with negative quiescent voltage could be used as a possible way to actively suppress self-heating related device degradation.展开更多
A thermal model of 4H-SiC MESFET is developed based on the temperature dependences of material parameters and three-region I - V model. The static current characteristics of 4H-SiC MESFET have been obtained with the c...A thermal model of 4H-SiC MESFET is developed based on the temperature dependences of material parameters and three-region I - V model. The static current characteristics of 4H-SiC MESFET have been obtained with the consideration of the self-heating effect on related parameters including electron mobility, saturation velocity and thermal conductivity. High voltage performances are analysed using equivalent thermal conductivity model. Using the physicalbased simulations, we studied the dependence of self-heating temperature on the thickness and doping of substrate. The obtained results can be used for optimization of the thermal design of the SiC-based high-power field effect transistors.展开更多
The influence of self-heating on the millimeter-wave(mm-wave)and terahertz(THz)performance of double-drift region(DDR)impact avalanche transit time(IMPATT)sources based on silicon(Si)has been investigated in this pape...The influence of self-heating on the millimeter-wave(mm-wave)and terahertz(THz)performance of double-drift region(DDR)impact avalanche transit time(IMPATT)sources based on silicon(Si)has been investigated in this paper.The dependences of static and large-signal parameters on junction temperature are estimated using a non-sinusoidal voltage excited(NSVE)large-signal simulation technique developed by the authors,which is based on the quantum-corrected drift-diffusion(QCDD)model.Linear variations of static parameters and non-linear variations of large-signal parameters with temperature have been observed.Analytical expressions representing the temperature dependences of static and large-signal parameters of the diodes are developed using linear and 2nd degree polynomial curve fitting techniques,which will be highly useful for optimizing the thermal design of the oscillators.Finally,the simulated results are found to be in close agreement with the experimentally measured data.展开更多
Dynamic self-heating effect(SHE)of silicon-on-insulator(SOI)MOSFET is comprehensively evaluated by ultrafast pulsed I-V measurement in this work.It is found for the first time that the SHE complete heating response an...Dynamic self-heating effect(SHE)of silicon-on-insulator(SOI)MOSFET is comprehensively evaluated by ultrafast pulsed I-V measurement in this work.It is found for the first time that the SHE complete heating response and cooling response of SOI MOSFETs are conjugated,with two-stage curves shown.We establish the effective thermal transient response model with stage superposition corresponding to the heating process.The systematic study of SHE dependence on workload shows that frequency and duty cycle have more significant effect on SHE in first-stage heating process than in the second stage.In the first-stage heating process,the peak lattice temperature and current oscillation amplitude decrease by more than 25 K and 4%with frequency increasing to 10 MHz,and when duty cycle is reduced to 25%,the peak lattice temperature drops to 306 K and current oscillation amplitude decreases to 0.77%.Finally,the investigation of two-stage(heating and cooling)process provides a guideline for the unified optimization of dynamic SHE in terms of workload.As the operating frequency is raised to GHz,the peak temperature depends on duty cycle,and self-heating oscillation is completely suppressed.展开更多
A new self-heating effect model for 4H-SiC MESFETs is proposed based on a combination of an analytical and a computer aided design （CAD） oriented drain current model. The circuit oriented expressions of 4H-SiC low-f...A new self-heating effect model for 4H-SiC MESFETs is proposed based on a combination of an analytical and a computer aided design （CAD） oriented drain current model. The circuit oriented expressions of 4H-SiC low-field electron mobility and incomplete ionization rate, which are related to temperature, are presented in this model, which are used to estimate the self-heating effect of 4H-SiC MESFETs. The verification of the present model is made, and the good agreement between simulated results and measured data of DC I - V curves with the self-heating effect is obtained.展开更多
A machine learning-based prediction of the self-heating characteristics and the negative temperature coefficient(NTC)effect detection of nanocomposites incorporating carbon nanotube(CNT)and carbon fiber(CF)is proposed...A machine learning-based prediction of the self-heating characteristics and the negative temperature coefficient(NTC)effect detection of nanocomposites incorporating carbon nanotube(CNT)and carbon fiber(CF)is proposed.The CNT content was fixed at 4.0 wt.%,and CFs having three different lengths(0.1,3 and 6 mm)at dosage of 1.0 wt.%were added to fabricate the specimens.The self-heating properties of the specimens were evaluated via self-heating tests.Based on the experiment results,two types of artificial neural network(ANN)models were constructed to predict the surface temperature and electrical resistance,and to detect a severe NTC effect.The present predictions were compared with experimental values to verify the applicability of the proposed ANN models.The ANN model for data prediction was able to predict the surface temperature and electrical resistance closely,with corresponding R-squared value of 0.91 and 0.97,respectively.The ANN model for data detection could detect the severe NTC effect occurred in the nanocomposites under the self-heating condition,as evidenced by the accuracy and sensitivity values exceeding 0.7 in all criteria.展开更多
The self-heating lunch box(SHLB)is a kind of popular instant food in China,yet little is known about the associated chemical release risk during its heating process.In this study,we investigated organophosphate esters...The self-heating lunch box(SHLB)is a kind of popular instant food in China,yet little is known about the associated chemical release risk during its heating process.In this study,we investigated organophosphate esters(OPEs)in original unheated food(UF),SHLB-heated processed food(HF)and potential OPE release from SHLB packaging materials.Significantly higher concentrations of OPEs were observed in HF(267±246 ng/g dry weight(dw))than in UF(163±211 ng/g dw)(p<0.001),suggesting an introduction of additional OPEs during heating processes.Tris(2-chloroethyl)phosphate,triethyl phosphate,and tris(2-chloroisopropyl)phosphate exhibited the highest absolute increased amounts,with 137,48.8,and 149%growth in HF than in UF,respectively.Migration testing revealed that packaging materials were rich in OPEs and can release considerable OPEs into food simulates(range,14.7-90.8 ng/g;mean,47.9±21.8).Influencing factors(temperature,contact time,oily food)on OPE migration from packaging materials to food were assessed.Higher temperature and longer contact time increased OPE contents in food simulates.Moreover,the presence of abundant OPEs in UF and significant correlations among different OPEs(p<0.05)suggested contamination happened during food processing and storage.With one SHLB meal a day,a 12-fold increase of OPE intake was observed for humans compared to those following a traditional dietary habit.In the high-exposure(95th percentile)scenario,hazard quotients of nine OPEs ranged from 0.00005 to 0.05.Our results suggested that the SHLB exposure pathway of OPEs should be particularly paid attention to in specific subpopulations that prefer this dietary habit.展开更多
We use an electro-thermal coupled Monte Carlo simulation framework to investigate the self-heating effect（SHE） in 14 nm bulk n Fin FETs with ambient temperature（TA） from 220 to 400 K. Based on this method, nonloca...We use an electro-thermal coupled Monte Carlo simulation framework to investigate the self-heating effect（SHE） in 14 nm bulk n Fin FETs with ambient temperature（TA） from 220 to 400 K. Based on this method, nonlocal heat generation can be achieved. Contact thermal resistances of Si/Metal and Si/Si O_2 are selected to ensure that the source and drain heat dissipation paths are the first two heat dissipation paths. The results are listed below：（i） not all input power（Q_（input） turns into heat generation in the device region and some is taken out by the thermal non-equilibrium carriers, owing to the serious non-equilibrium transport;（ii） a higher TA leads to a larger ratio of input power turning into heat generation in the device region at the same operating voltages;（iii） SHE can lead to serious degradation in the carrier transport, which will increase when TA increases;（iv） the current degradation can be 8.9% when Vds = 0.7 V, Vgs = 1 V and TA = 400 K;（v） device thermal resistance（Rth） increases with increasing of TA, which is seriously impacted by the non-equilibrium transport. Hence, the impact of TA should be carefully considered when investigating SHE in nanoscale devices.展开更多
Establishment of a new technique or extension of an existing technique for thermal and thermoelectric measurements to a more challenging system is an important task to explore the thermal and thermoelectric properties...Establishment of a new technique or extension of an existing technique for thermal and thermoelectric measurements to a more challenging system is an important task to explore the thermal and thermoelectric properties of various materials and systems. The bottleneck lies in the challenges in measuring the thermal contact resistance. In this work, we applied electron beam self-heating technique to derive the intrinsic thermal conductivity of suspended Molybdenum Disulfide （MoS2） ribbons and the thermal contact resistance, with which the interracial thermal resistance between few-layer MoS2 and Pt electrodes was calculated. The measured room temperature thermal conductivity of MoS2 is around -30 W/（m K）, while the estimated interracial thermal resistance is around -2 × 10 -6 m-2 K/W. Our experiments extend a useful branch in application of this technique for studying thermal properties of suspended layered ribbons and have potential application in investigating the interracial thermal resistance of different twodimensional （2D） heterojunctions.展开更多
The effects of self-heating and traps on the drain current transient responses of AlGaN/GaN HEMTs are studied by 2D numerical simulation. The variation of the drain current simulated by the drain turn-on pulses has be...The effects of self-heating and traps on the drain current transient responses of AlGaN/GaN HEMTs are studied by 2D numerical simulation. The variation of the drain current simulated by the drain turn-on pulses has been analyzed. Our results show that temperature is the main factor for the drain current lag. The time that the drain current takes to reach a steady state depends on the thermal time constant, which is 8μs in this case. The dynamics of the trapping of electron and channel electron density under drain turn-on pulse voltage are discussed in detail, which indicates that the accepter traps in the buffer are the major reason for the current collapse when the electric field significantly changes. The channel electron density has been shown to increase as the channel temperature rises.展开更多
The fact that traditional semiconductors have almost reached their performance limits in high power applications,is leading to failure in high power devices.This failure results from self-heating effects,leading to hi...The fact that traditional semiconductors have almost reached their performance limits in high power applications,is leading to failure in high power devices.This failure results from self-heating effects,leading to higher temperature and a breakdown of the electrical contact.The good thermal and mechanical properties of 4 H-SiC and Ti_(3)SiC_(2) and their good performance at high temperatures make them good candidates for high power applications.In order to improve the performance of electrical contacts,a thermo-mechanical simulation was carried out using the finite element method to study the self-heating effects in a high power PN diode made of a 4 H-SiC substrate with a Ti_(3)SiC_(2) electrical contact and Al_(3)Ti metallization.The three-dimensional model took into account the temperature dependency of several thermal and mechanical properties of the different materials to improve calculation accuracy.To simulate the self-heating,the power loss in the diode was calculated from the corresponding direct I-V characteristic.In addition,the interfacial thermal resistances(ITR)between the different layers were varied and studied in the thermo-mechanical investigation,in sequence to determine their effects on the heat dissipation and the resulting stresses in the model.The results show that for realistic ITR values,the ITR barely affects heat diffusion mechanical stresses of the model.Whereas,ITR may cause serious problem to the functionality and the efficiency of some electronic components.On the other hand,extremely large ITR leads to a decrease in the thermal stress in the diode.Good control on the ITR may help to improve the performance of high-power devices in the future,in addition to providing more efficient electrical contacts.展开更多
To reduce the self-heating effect of strained Si grown on relaxed SiGe-on-insulator（SGOI） n-type metal-oxide-semiconductor field-effect transistors（nMOSFETs）,this paper proposes a novel device called double step b...To reduce the self-heating effect of strained Si grown on relaxed SiGe-on-insulator（SGOI） n-type metal-oxide-semiconductor field-effect transistors（nMOSFETs）,this paper proposes a novel device called double step buried oxide（BOX） SGOI,investigates its electrical and thermal characteristics,and analyzes the effect of self-heating on its electrical parameters.During the simulation of the device,a low field mobility model for strained Si MOSFETs is established and reduced thermal conductivity resulting from phonon boundary scattering is considered.A comparative study of SGOI nMOSFETs with different BOX thicknesses under channel and different channel strains has been performed.By reducing moderately the BOX thickness under the channel,the channel temperature caused by the self-heating effect can be effectively reduced.Moreover,mobility degradation,off state current and a short-channel effect such as drain induced barrier lowering can be well suppressed.Therefore,SGOI MOSFETs with a thinner BOX under the channel can improve the overall performance and long-term reliability efficiently.展开更多
Considering the self-heating effect, an accurate expression for the global interconnection resistance per unit length in terms of interconnection wire width and spacing is presented. Based on the proposed resistance m...Considering the self-heating effect, an accurate expression for the global interconnection resistance per unit length in terms of interconnection wire width and spacing is presented. Based on the proposed resistance model and according to the trade-off theory, a novel optimization analytical model of delay, power dissipation and bandwidth is derived. The proposed optimal model is verified and compared based on 90 nm, 65 nm and 40 nm CMOS technologies. It can be found that more optimum results can be easily obtained by the proposed model. This optimization model is more accurate and realistic than the conventional optimization models, and can be integrated into the global interconnection design ofnano-scale integrated circuits.展开更多
基金National Natural Science Foundation of China,12272305,Yahui Zhang,12372123,Xiaojun GuBasic Research Program,JCKY2022603C016,Xiaojun Gu。
文摘This paper aims to seek expedited fatigue analysis methods using the infrared self-heating technique.The fatigue analysis of NiTi shape memory alloys is obtained through a hybrid approach:fatigue tests to failure yield relatively shorter fatigue lives,while determining the fatigue limit,normally involving extremely high cycles approaching 107 cycles,is directly achieved via self-heating tests.This methodology significantly reduces testing cycles,costing only a fraction of the several-thousand-cycle tests typically required.The validity of this approach is successfully demonstrated through fatigue testing of 18Ni steel:the entire S–N curve is examined using the traditional fatigue test until a life of up to 10^(7) cycles,and the indicated fatigue limit agrees well with the one directly determined through the self-heating method.Subsequently,this developed approach is applied to the fatigue analysis of shape memory alloys under complex loading,enabling the concurrent estimation of the limits of phase transformation-dominated low-cycle fatigue and high-cycle fatigue in the elastic regime on a single specimen.The results obtained align well with other supporting evidence.
基金Project(51304238)supported by the National Natural Science Foundation of ChinaProject(JSK200206)supported by the Foundation of Key Laboratory of Mine Thermo-motive Disaster and Prevention,Ministry of Education,China
文摘In order to reveal the nonlinear dynamics characteristics of unsteady self-heating process of sulfide ores, nine different kinds of sulfide ore samples from a pyrite mine in China were taken as experimental materials and their self-heating characteristics were measured in laboratory. Furthermore, the measured temperature was studied by integrating wavelet transform, nonlinear characteristic parameters extraction and fuzzy comprehensive evaluation. The results indicate that only the ore samples 1, 2, 6 and 9 have obvious self-heating phenomenon, and their self-heating initiative temperatures are 220 ℃, 239 ℃, 220 ℃ and 220 ℃, respectively, which means that they are difficult to produce self-heating under normal mining conditions. The correlation dimension of self-heating process is fraction and the maximum Lyapunov exponent is positive, which means that it is feasible to study the self-heating process based on chaotic dynamics theory. The nonlinearities of self-heating process of these four samples （ore samples 1, 2, 6 and 9） are 0.8227, 0.7521, 0.9401 and 0.8827 respectively and the order of the samples according to these results is： sample 6, sample 9, sample 1, sample 2, which is consistent with the measured results of self-heating characteristics. Therefore, the nonlinearity method can be used to evaluate the self-heating tendency of sulfide ores, and it is an effective verification of the reliability of measured results.
基金funded by the National Key Research and Development Program of China(2018YFB0104400)supported by the Beijing Natural Science Foundation(2214066)。
文摘To obtain intrinsic overcharge boundary and investigate overcharge mechanism,here we propose an innovative method,the step overcharge test,to reduce the thermal crossover and distinguish the overcharge thermal behavior,including 5%state of charge(SOC)with small current overcharge and resting until the temperature equilibrium under adiabatic conditions.The intrinsic thermal response and the self-excitation behaviour are analysed through temperature and voltage changes during the step overcharge period.Experimental results show that the deintercalated state of the cathode is highly correlated to self-heating parasitic reactions.Before reaching the upper limit of Negative/Positive(N/P)ratio,the temperature changes little,the heat generation is significantly induced by the reversible heat(endothermic)and ohmic heat,which could balance each other.Following that the lithium metal is gradually deposited on the surface of the anode and reacts with electrolyte upon overcharge,inducing selfheating side reaction.However,this spontaneous thermal reaction could be“self-extinguished”.When the lithium in cathode is completely deintercalated,the boundary point of overcharge is about 4.7 V(~148%SOC,>40℃),and from this point,the self-heating behaviour could be continuously triggered until thermal runaway(TR)without additional overcharge.The whole static and spontaneous process lasts for 115 h and the side reaction heat is beyond 320,000 J.The continuous self-excitation behavior inside the battery is attributed to the interaction between the highly oxidized cathode and the solvent,which leads to the dissolution of metal ions.The dissolved metal ions destroy the SEI(solid electrolyte interphase)film on the surface of the deposited Li of anode,which induces the thermal reaction between lithium metal and the solvent.The interaction between cathode,the deposited Li of anode,and solvent promotes the temperature of the battery to rise slowly.When the temperature of the battery reaches more than 60℃,the reaction between lithium metal and solvent is accelerated.After the temperature rises rapidly to the melting point of the separator,it triggers the thermal runaway of the battery due to the short circuit of the battery.
基金supported by National Natural Science Foundation of China (No.10905044)
文摘For exploiting advantages of electron beam air plasma in some unusual applications, a Monte Carlo （MC） model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasma by considering the self-heating effect. Based on the model, the electron beam induced temperature field and the related plasma properties are investigated. The results indicate that a nonuniform temperature field is formed in the electron beam plasma region and the average temperature is of the order of 600 K. Moreover, much larger volume pear-shaped electron beam plasma is produced in hot state rather than in cold state. The beam ranges can, with beam energies of 75 keV and 80 keV, exceed 1.0 m and 1.2 m in air at pressure of 100 torr, respectively. Finally, a well verified formula is obtained for calculating the range of high energy electron beam in atmosphere.
基金made possible through a visiting postdoctoral fellowship to A.H. Ozdeniz by the Scientific and Technological Research Council of Turkey (TUBITAK)An operating research grant through the Natural Sciences and Engineering Council of Canada (NSERC) is also acknowledged
文摘Original surface chemistry of sulphidesis altered upon contact with air, leading to ''oxidation'', which is accompanied by evolution of heat. The current study reports results of an investigation on extent of exothermicity of an experimental nickel-copper sulphide stockpile that was formed at a mining site in Sudbury, Canada. The ore contained pentlandite and chalcopyrite that are accompanied by a large quantity of pyrrhotite. The self-heating characteristics were recorded by temperature sensors placed inside the stockpile. Ambient conditions such as temperature, humidity, and wind velocity were simultaneously recorded. The inner temperature of the stockpile indicated significant fluctuations due to rapid changes, particularly in the outside temperature. The minimum and maximum temperatures recorded in the outside and inside were 5 and 10.5, 44.3 and 32 ℃, respectively. The self-heating capacity of the sulphide ore stockpile observed represents a mild case compared to that experienced by coals. Possible reasons are discussed.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant Nos.61925110,62004184 and 62234007the Key-Area Research and Development Program of Guangdong Province under Grant No.2020B010174002.
文摘The self-heating effect severely limits device performance and reliability.Although some studies have revealed the heat distribution ofβ-Ga_(2)O_(3) MOSFETs under biases,those devices all have small areas and have difficulty reflecting practical con-ditions.This work demonstrated a multi-fingerβ-Ga_(2)O_(3) MOSFET with a maximum drain current of 0.5 A.Electrical characteris-tics were measured,and the heat dissipation of the device was investigated through infrared images.The relationship between device temperature and time/bias is analyzed.
文摘CFD models have been developed to investigate the Iongwall goaf gas flow patternsunder different mining and geological control conditions.The Iongwall goaf wastreated as porous regions and gas flow was modelled as a momentum sink added to themomentum equation.Gas desorption from the caved goaf and destressed coal seamswithin the mining disturbed area was modelled as additional mass sources in the continuityequation.These CFD models were developed according to specific Iongwall layoutsand calibrated against field monitoring data.Two case studies were presented demonstratingthe application of CFD modelling of goaf gas flow characteristics for improved goafgas capture and the reduction of oxygen ingress into the goaf areas for self-heating prevention.Results from the case studies indicate that the optimum goaf drainage strategywould be a combination of shallow (near the face) and deep holes to improve the overalldrainage efficiency and gas purity.For gassy Iongwall faces retreating against the seam dip,it is recommended to conduct cross-measure roof hole drainage targeting the fracturedzones overlying the return corner,rather than high capacity surface goaf drainage deep inthe goaf.
基金Project supported by the National Key R&D Program of China(Grant No.2016YFB0400100)the National Natural Science Foundation of China(Grant No.91850112)+3 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20161401)the Priority Academic Program Development of Jiangsu Higher Education Institutions,Chinathe Science and Technology Project of State Grid Corporation of China(Grant No.SGSDDK00KJJS1600071)the Fundamental Research Funds for the Central Universities,China(Grant No.14380098)
文摘Self-heating effect in amorphous InGaZnO thin-film transistors remains a critical issue that degrades device performance and stability, hindering their wider applications. In this work, pulsed current–voltage analysis has been applied to explore the physics origin of self-heating induced degradation, where Joule heat is shortly accumulated by drain current and dissipated in repeated time cycles as a function of gate bias. Enhanced positive threshold voltage shift is observed at reduced heat dissipation time, higher drain current, and increased gate width. A physical picture of Joule heating assisted charge trapping process has been proposed and then verified with pulsed negative gate bias stressing scheme, which could evidently counteract the self-heating effect through the electric-field assisted detrapping process. As a result, this pulsed gate bias scheme with negative quiescent voltage could be used as a possible way to actively suppress self-heating related device degradation.
基金Project supported by the National Natural Science Foundation of China (Grant No 60606022)the State Key Development Program for Basic Research of China (Grant No 51327010101)Xi’an Applied Materials Innovation Fund,China (Grant No XA-AM-200702)
文摘A thermal model of 4H-SiC MESFET is developed based on the temperature dependences of material parameters and three-region I - V model. The static current characteristics of 4H-SiC MESFET have been obtained with the consideration of the self-heating effect on related parameters including electron mobility, saturation velocity and thermal conductivity. High voltage performances are analysed using equivalent thermal conductivity model. Using the physicalbased simulations, we studied the dependence of self-heating temperature on the thickness and doping of substrate. The obtained results can be used for optimization of the thermal design of the SiC-based high-power field effect transistors.
文摘The influence of self-heating on the millimeter-wave(mm-wave)and terahertz(THz)performance of double-drift region(DDR)impact avalanche transit time(IMPATT)sources based on silicon(Si)has been investigated in this paper.The dependences of static and large-signal parameters on junction temperature are estimated using a non-sinusoidal voltage excited(NSVE)large-signal simulation technique developed by the authors,which is based on the quantum-corrected drift-diffusion(QCDD)model.Linear variations of static parameters and non-linear variations of large-signal parameters with temperature have been observed.Analytical expressions representing the temperature dependences of static and large-signal parameters of the diodes are developed using linear and 2nd degree polynomial curve fitting techniques,which will be highly useful for optimizing the thermal design of the oscillators.Finally,the simulated results are found to be in close agreement with the experimentally measured data.
文摘Dynamic self-heating effect(SHE)of silicon-on-insulator(SOI)MOSFET is comprehensively evaluated by ultrafast pulsed I-V measurement in this work.It is found for the first time that the SHE complete heating response and cooling response of SOI MOSFETs are conjugated,with two-stage curves shown.We establish the effective thermal transient response model with stage superposition corresponding to the heating process.The systematic study of SHE dependence on workload shows that frequency and duty cycle have more significant effect on SHE in first-stage heating process than in the second stage.In the first-stage heating process,the peak lattice temperature and current oscillation amplitude decrease by more than 25 K and 4%with frequency increasing to 10 MHz,and when duty cycle is reduced to 25%,the peak lattice temperature drops to 306 K and current oscillation amplitude decreases to 0.77%.Finally,the investigation of two-stage(heating and cooling)process provides a guideline for the unified optimization of dynamic SHE in terms of workload.As the operating frequency is raised to GHz,the peak temperature depends on duty cycle,and self-heating oscillation is completely suppressed.
基金Project supported by the National Defense Foundation of China (Grant No 51327010101)the National Natural Science Foundation of China (Grant No 60606022)
文摘A new self-heating effect model for 4H-SiC MESFETs is proposed based on a combination of an analytical and a computer aided design （CAD） oriented drain current model. The circuit oriented expressions of 4H-SiC low-field electron mobility and incomplete ionization rate, which are related to temperature, are presented in this model, which are used to estimate the self-heating effect of 4H-SiC MESFETs. The verification of the present model is made, and the good agreement between simulated results and measured data of DC I - V curves with the self-heating effect is obtained.
基金This research was supported by Chungbuk National University Korea National University Development Project(2021).
文摘A machine learning-based prediction of the self-heating characteristics and the negative temperature coefficient(NTC)effect detection of nanocomposites incorporating carbon nanotube(CNT)and carbon fiber(CF)is proposed.The CNT content was fixed at 4.0 wt.%,and CFs having three different lengths(0.1,3 and 6 mm)at dosage of 1.0 wt.%were added to fabricate the specimens.The self-heating properties of the specimens were evaluated via self-heating tests.Based on the experiment results,two types of artificial neural network(ANN)models were constructed to predict the surface temperature and electrical resistance,and to detect a severe NTC effect.The present predictions were compared with experimental values to verify the applicability of the proposed ANN models.The ANN model for data prediction was able to predict the surface temperature and electrical resistance closely,with corresponding R-squared value of 0.91 and 0.97,respectively.The ANN model for data detection could detect the severe NTC effect occurred in the nanocomposites under the self-heating condition,as evidenced by the accuracy and sensitivity values exceeding 0.7 in all criteria.
基金supported by the National Natural Science Foundation of China (22276214,22022611,and 21777190)the Youth Innovation Promotion Association CAS (Y2022020).
文摘The self-heating lunch box(SHLB)is a kind of popular instant food in China,yet little is known about the associated chemical release risk during its heating process.In this study,we investigated organophosphate esters(OPEs)in original unheated food(UF),SHLB-heated processed food(HF)and potential OPE release from SHLB packaging materials.Significantly higher concentrations of OPEs were observed in HF(267±246 ng/g dry weight(dw))than in UF(163±211 ng/g dw)(p<0.001),suggesting an introduction of additional OPEs during heating processes.Tris(2-chloroethyl)phosphate,triethyl phosphate,and tris(2-chloroisopropyl)phosphate exhibited the highest absolute increased amounts,with 137,48.8,and 149%growth in HF than in UF,respectively.Migration testing revealed that packaging materials were rich in OPEs and can release considerable OPEs into food simulates(range,14.7-90.8 ng/g;mean,47.9±21.8).Influencing factors(temperature,contact time,oily food)on OPE migration from packaging materials to food were assessed.Higher temperature and longer contact time increased OPE contents in food simulates.Moreover,the presence of abundant OPEs in UF and significant correlations among different OPEs(p<0.05)suggested contamination happened during food processing and storage.With one SHLB meal a day,a 12-fold increase of OPE intake was observed for humans compared to those following a traditional dietary habit.In the high-exposure(95th percentile)scenario,hazard quotients of nine OPEs ranged from 0.00005 to 0.05.Our results suggested that the SHLB exposure pathway of OPEs should be particularly paid attention to in specific subpopulations that prefer this dietary habit.
基金supported by the National Key Technology Research and Development Program of China(No.2016YFA0202101)the National Natural Science Foundation of China(Nos.61421005,61604005)+1 种基金the National High-Tech R&D Program(863 Program)(No.2015AA016501)The simulation was carried out at National Supercomputer Center in Tianjin,with Tian He-1(A)
文摘We use an electro-thermal coupled Monte Carlo simulation framework to investigate the self-heating effect（SHE） in 14 nm bulk n Fin FETs with ambient temperature（TA） from 220 to 400 K. Based on this method, nonlocal heat generation can be achieved. Contact thermal resistances of Si/Metal and Si/Si O_2 are selected to ensure that the source and drain heat dissipation paths are the first two heat dissipation paths. The results are listed below：（i） not all input power（Q_（input） turns into heat generation in the device region and some is taken out by the thermal non-equilibrium carriers, owing to the serious non-equilibrium transport;（ii） a higher TA leads to a larger ratio of input power turning into heat generation in the device region at the same operating voltages;（iii） SHE can lead to serious degradation in the carrier transport, which will increase when TA increases;（iv） the current degradation can be 8.9% when Vds = 0.7 V, Vgs = 1 V and TA = 400 K;（v） device thermal resistance（Rth） increases with increasing of TA, which is seriously impacted by the non-equilibrium transport. Hence, the impact of TA should be carefully considered when investigating SHE in nanoscale devices.
基金supported by the National Natural Science Foundation of China(11674245 and 11334007)Shanghai Committee of Science and Technology in China(17142202100 and 17ZR1447900)supported by A*STAR Pharos Funding from the Science and Engineering Research Council of Singapore(Grant No.152 72 00015)
文摘Establishment of a new technique or extension of an existing technique for thermal and thermoelectric measurements to a more challenging system is an important task to explore the thermal and thermoelectric properties of various materials and systems. The bottleneck lies in the challenges in measuring the thermal contact resistance. In this work, we applied electron beam self-heating technique to derive the intrinsic thermal conductivity of suspended Molybdenum Disulfide （MoS2） ribbons and the thermal contact resistance, with which the interracial thermal resistance between few-layer MoS2 and Pt electrodes was calculated. The measured room temperature thermal conductivity of MoS2 is around -30 W/（m K）, while the estimated interracial thermal resistance is around -2 × 10 -6 m-2 K/W. Our experiments extend a useful branch in application of this technique for studying thermal properties of suspended layered ribbons and have potential application in investigating the interracial thermal resistance of different twodimensional （2D） heterojunctions.
基金Project supported by the National Natural Science Foundation of China(Nos.61376077,61201046,61204081)the Beijing Natural Science Foundation(Nos.4132022,4122005)+1 种基金the Guangdong Strategic Emerging Industry Project of China(No.2012A080304003)the Doctoral Fund of Innovation of Beijing University of Technology
文摘The effects of self-heating and traps on the drain current transient responses of AlGaN/GaN HEMTs are studied by 2D numerical simulation. The variation of the drain current simulated by the drain turn-on pulses has been analyzed. Our results show that temperature is the main factor for the drain current lag. The time that the drain current takes to reach a steady state depends on the thermal time constant, which is 8μs in this case. The dynamics of the trapping of electron and channel electron density under drain turn-on pulse voltage are discussed in detail, which indicates that the accepter traps in the buffer are the major reason for the current collapse when the electric field significantly changes. The channel electron density has been shown to increase as the channel temperature rises.
文摘The fact that traditional semiconductors have almost reached their performance limits in high power applications,is leading to failure in high power devices.This failure results from self-heating effects,leading to higher temperature and a breakdown of the electrical contact.The good thermal and mechanical properties of 4 H-SiC and Ti_(3)SiC_(2) and their good performance at high temperatures make them good candidates for high power applications.In order to improve the performance of electrical contacts,a thermo-mechanical simulation was carried out using the finite element method to study the self-heating effects in a high power PN diode made of a 4 H-SiC substrate with a Ti_(3)SiC_(2) electrical contact and Al_(3)Ti metallization.The three-dimensional model took into account the temperature dependency of several thermal and mechanical properties of the different materials to improve calculation accuracy.To simulate the self-heating,the power loss in the diode was calculated from the corresponding direct I-V characteristic.In addition,the interfacial thermal resistances(ITR)between the different layers were varied and studied in the thermo-mechanical investigation,in sequence to determine their effects on the heat dissipation and the resulting stresses in the model.The results show that for realistic ITR values,the ITR barely affects heat diffusion mechanical stresses of the model.Whereas,ITR may cause serious problem to the functionality and the efficiency of some electronic components.On the other hand,extremely large ITR leads to a decrease in the thermal stress in the diode.Good control on the ITR may help to improve the performance of high-power devices in the future,in addition to providing more efficient electrical contacts.
基金Project supported by the National Natural Science Foundation of China(Nos.60976068,60936005)the Cultivation Fund of the Key Scientific and Technical Innovation Project,Ministry of Education of China(No.708083)the Specialized Research Fund for the Doctoral Program of Higher Education,China(No.200807010010)
文摘To reduce the self-heating effect of strained Si grown on relaxed SiGe-on-insulator（SGOI） n-type metal-oxide-semiconductor field-effect transistors（nMOSFETs）,this paper proposes a novel device called double step buried oxide（BOX） SGOI,investigates its electrical and thermal characteristics,and analyzes the effect of self-heating on its electrical parameters.During the simulation of the device,a low field mobility model for strained Si MOSFETs is established and reduced thermal conductivity resulting from phonon boundary scattering is considered.A comparative study of SGOI nMOSFETs with different BOX thicknesses under channel and different channel strains has been performed.By reducing moderately the BOX thickness under the channel,the channel temperature caused by the self-heating effect can be effectively reduced.Moreover,mobility degradation,off state current and a short-channel effect such as drain induced barrier lowering can be well suppressed.Therefore,SGOI MOSFETs with a thinner BOX under the channel can improve the overall performance and long-term reliability efficiently.
基金supported by the National Natural Science Foundation of China(No.60606006)the Key Science&Technology Special Project of Shaanxi Province,China(No.2011KTCQ01-19)the National Defense Pre-Research Foundation of China(No.9140A23060111)
文摘Considering the self-heating effect, an accurate expression for the global interconnection resistance per unit length in terms of interconnection wire width and spacing is presented. Based on the proposed resistance model and according to the trade-off theory, a novel optimization analytical model of delay, power dissipation and bandwidth is derived. The proposed optimal model is verified and compared based on 90 nm, 65 nm and 40 nm CMOS technologies. It can be found that more optimum results can be easily obtained by the proposed model. This optimization model is more accurate and realistic than the conventional optimization models, and can be integrated into the global interconnection design ofnano-scale integrated circuits.
