Temperature inversion enables superior stability for low-temperature Zn-ion batteries

It is challenging for aqueous Zn-ion batteries(ZIBs)to achieve comparable low-temperature(low-T)performance due to the easy-frozen electrolyte and severe Zn dendrites.Herein,an aqueous electrolyte with a low freezing point and high ionic conductivity is proposed.Combined with molecular dynamics simulation and multi-scale interface analysis(time of flight secondary ion mass spectrometry threedimensional mapping and in-situ electrochemical impedance spectroscopy method),the temperature independence of the V_(2)O_(5)cathode and Zn anode is observed to be opposite.Surprisingly,dominated by the solvent structure of the designed electrolyte at low temperatures,vanadium dissolution/shuttle is significantly inhibited,and the zinc dendrites caused by this electrochemical crosstalk are greatly relieved,thus showing an abnormal temperature inversion effect.Through the disclosure and improvement of the above phenomena,the designed Zn||V_(2)O_(5)full cell delivers superior low-T performance,maintaining almost 99%capacity retention after 9500 cycles(working more than 2500 h)at-20°C.This work proposes a kind of electrolyte suitable for low-T ZIBs and reveals the inverse temperature dependence of the Zn anode,which might offer a novel perspective for the investigation of low-T aqueous battery systems.

Evaluation of Cold Resistance and Semi-lethal Low Temperature(LT_(50))of Nine Pear Cultivars

[Objectives]To evaluate the cold resistance and semi-lethal temperature of pear cultivars,and provide a theoretical basis for the regional extension and breeding of cold-resistant pear cultivars.[Methods]Nine pear cultivars were used to study the changes in relative conductivity and cell injury rate of pear branches under low temperature stress,and the semi-lethal temperature(LT_(50))of pear branches was analyzed by fitting Logistic equation.[Results]The relative conductivity and cell injury rate of pear branches took on the trend of slow increase,rapid increase,and slow increase the decrease of treatment temperature.The LC_(50) of the nine pear cultivars were as follows:Nanguo pear-33.9℃,Wanyu-32.3℃,Red D Anjou-31.8℃,Jinfeng-31.3℃,Wujiuxiang-29.2℃,20 th Century Pear-29.1℃,Hanxiang-35.1℃,Yuluxiang-27.9℃ and Korla Fragrant Pear-29.2℃.[Conclusions]The semi-lethal temperature could reflect the cold resistance of pear trees,and Wanxiang had better cold resistance.The evaluation of cold resistance and semi-lethal temperature of pear cultivars can provide theoretical basis for regional extension and breeding of cold-resistant pear cultivars.

Effects of Cold Acclimation on Several Enzyme Activities in Euonymus radicans ‘Emorald & Gold’and Its Relation to Semi-lethal Temperature

The changes in activities of superoxide dismutase (SOD), peroxidase (POD) and ATPase in the leaves of Euonymus radicans were studied when seedlings were cold-acclimated (at 4 ℃) for 1 week, 2 weeks, 3 weeks and then treated for 1 d under low temperature stress (at 5 ℃). The semi-lethal temperatures of acclimated and unacclimated seedlings were also investigated. The results indicated that the activities of the three enzymes in the leaves of the seedlings treated at 4 ℃ for 1, 2 and 3 weeks were all higher than those of unacclimated seedings (treated at 22 ℃ as controls). The activities of SOD and POD increased continuously with the prolongation of the time of cold acclimation, but stepped up to summits then down to the levels of the controls. The activities of SOD culminated at the first week, and the activities of POD at the second week. When acclimated and unacclimated seedlings were both treated at 5 ℃ for 1 d, the activities of the three enzymes in the leaves of acclimated seedlings were a little lower than those before stress, but higher than those of the controls. Moreover, the decrease rate of enzyme activities was greatly lower than that of the controls. The results showed that cold acclimation could enhance the stability of the three enzymes in the leaves of seedlings under low temperature stress; the semi-lethal temperature was 19.1 ℃ when the seedlings were treated at 4 ℃ for 3 weeks, but it was 5.4 ℃ when the seedlings were treated at 22 ℃. The decline of the semi-lethal temperature caused by the adaptive changes of enzyme activities was one of the foundations of enhancing the cold tolerance.

Exploring the Low-Temperature Oxidation Chemistry of Cyclohexane in a Jet-Stirred Reactor:an Experimental and Kinetic Modeling Study

We report the investigation on the low-temperature oxidation of cyclohexane in a jet-stirred reactor over 500-742 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry （SVUV-PIMS） was used for identifying and quantifying the oxidation species. Major products, cyclic olefins, and oxygenated products including reactive hydroperoxides and high oxygen compounds were detected. Compared with n-alkanes, a narrow low-temperature window （-80 K） was observed in the low-temperature oxidation of cyclohexane. Besides, a kinetic model for cyclohexane oxidation was developed based on the CNRS model [Combust. Flame 160, 2319 （2013）], which can better capture the experimental results than previous models. Based on the modeling analysis, the 1,5-H shift dominates the crucial isomerization steps of the first and second O2 addition products in the low-temperature chain branching process of cyclohexane. The negative temperature coefficient behavior of cyclohexane oxidation results from the reduced chain branching due to the competition from chain inhibition and propagation reactions, i.e. the reaction between cyclohexyl radical and O2 and the de- composition of cyclohexylperoxy radical, both producing cyclohexene and HO2 radical, as well as the decomposition of cyclohexylhydroperoxy radical producing hex-5-en-l-al and OH radical.

Boosting energy-storage capability in carbon-based supercapacitors using low-temperature water-in-salt electrolytes

Supercapacitors(SCs) are high-power energy storage devices with ultra-fast charge/discharge properties.SCs using concentrated aqueous-based electrolytes can work at low temperatures due to their intrinsic properties, such as higher freezing point depression(FPD) and robustness. Besides the traditional organic-and aqueous-based(salt-in-water) electrolytes used in SCs, water-in-salt(WISE) sodium perchlorate electrolytes offer high FPD, non-flammability, and low-toxicity conditions, allowing the fabrication of safer, environmentally friendly, and more robust devices. For the first time, this work reports a comprehensive study regarding WISE system’s charge-storage capabilities and physicochemical properties under low-temperature conditions(T < 0 ℃) using mesoporous carbon-based electrodes. The effect of temperature reduction on the electrolyte viscosity and electrical properties was investigated using different techniques and the in-situ(or operando) Raman spectroscopy under dynamic polarization conditions.The cell voltage, equivalent series resistance, and specific capacitance were investigated as a function of the temperature. The cell voltage(U) increased ~ 50%, while the specific capacitance decreased ~20%when the temperature was reduced from 25 ℃ to -10 ℃. As a result, the maximum specific energy(E = CU^(2)/2) increased ~ 100%. Therefore, low-temperature WISEs are promising candidates to improve the energy-storage characteristics in SCs.

The Application of Thermomechanical Dynamics (TMD) to the Analysis of Nonequilibrium Irreversible Motion and a Low-Temperature Stirling Engine

We applied the method of Thermomechanical Dynamics (TMD) to a low-temperature Stirling engine, and the dissipative equation of motion and time-evolving physical quantities are self-consistently calculated for the first time in this field. The thermomechanical states of the heat engine are in Nonequilibrium Irreversible States (NISs), and time-dependent thermodynamic work W(t), internal energy E(t), energy dissipation or entropy Qd(t), and temperature T(t), are precisely studied and computed in TMD. We also introduced the new formalism, Q(t)-picture of thermodynamic heat-energy flows, for consistent analyses of NISs. Thermal flows in a long-time uniform heat flow and in a short-time heat flow are numerically studied as examples. In addition to the analysis of time-dependent physical quantities, the TMD analysis suggests that the concept of force and acceleration in Newtonian mechanics should be modified. The acceleration is defined as a continuously differentiable function of Class C2 in Newtonian mechanics, but the thermomechanical dynamics demands piecewise continuity for acceleration and thermal force, required from physical reasons caused by frictional variations and thermal fluctuations. The acceleration has no direct physical meaning associated with force in TMD. The physical implications are fundamental for the concept of the macroscopic phenomena in NISs composed of systems in thermal and mechanical motion.

A New Method for Predicting Wall Sticking Occurrence Temperature of High Water Cut Crude Oil

In crude oil transportation, adhesion of oil on pipe wall can cause partial or total blockage of the pipe. This process is significantly affected by wall sticking occurrence temperature(WSOT). In this work, an efficient approach for estimating WSOT of high water-cut oil, which can agree well with the actual environment of multiphase transportation pipeline, is proposed. Based on the energy dissipation theory, it is possible to make comparison of average shear rates between the stirred vessel and the flow loop. The impacts of water content and shear rate on WSOT are investigated using the stirred vessel and the flow loop. Good agreement has been observed between the stirred vessel and the flow loop results with the maximum and the average absolute deviations equating to 3.30 °C and 2.18 °C, respectively. The development of gathering scheme can enjoy some benefits from this method.

Effect of Heat-treatment Temperature on HA-coated Titanium Materials

Homogeneous HA coating materials were prepared on porous titanium by the low-temperature combustion synthesis. It was found that the mechanical properties of the specimen depend on the coating process and the heat treatment, and the bending strength would be reduced during the coating process but could be improved by heat treatment. The effects of the temperature during heat- treatment on the phase composition and microstructure of the as-prepared coating, and the bending strength of the specimen were investigated by XRD and SEM. The experimental results show that in the coating process, slight oxidation of the substrate may give rise to a drop in bending strength ; however, it could be increased by the reaction of HA and TiO2 , and the sintering of the coating during heat treatment. The HA particles in the coating, with very fine sized particles. were pretty active and would decompose at 800℃.

The dynamic change of pore structure for low-rank coal under refined upgrading pretreatment temperatures

Pore structure characteristics are significant factor in the evaluation of the physical characteristics of low-rank coal.In this study,three low-rank coal samples were collected from the Xishanyao Formation,Santanghu Basin,and low-temperature liquid-nitrogen adsorption(LP-N2A)measurements were taken under various pretreatment temperatures.Owing to the continuous loss of water and volatile matter in low-rank coal,the total pore volume assumes a three-step profile with knee temperatures of 150°C and 240°C.However,the ash in the coal can protect the coal skeleton.Pore collapse mainly occurs for mesopores with aperture smaller than 20 nm.Mesopores with apertures smaller than 5 nm exhibit a continuous decrease in pore volume,whereas the pore volume of mesopores with apertures ranging from 5 to 10 nm increases at lower pretreatment temperatures(<150°C)followed by a faint decrease.As for mesopores with apertures larger than 10 nm,the pore volume increases significantly when the pretreatment temperature reaches 300°C.The pore structure of low-rank coal features a significant heating effect,the pretreatment temperature should not exceed 150°C when the LP-N2A is used to evaluate the pore structure of low-rank coal to effectively evaluate the reservoir characteristics of low-rank coal.

Responses of electrical properties of tea leaves to low-temperature stress

Critical temperature is one of the most important parameters for the control of crop frost protection through airflow disturbance.It changes with complex weather conditions,thus it is difficult to be determined.A method of testing electrical property of tea leaves under cold stress was put forward to indicate critical temperature.The testing system was established to measure the capacitance,impedance,resistance and reactance of the samples under different air temperatures,air humidities and airflow velocities.The variation of the electrical property was also analyzed.The results show that at humidity below 70%and airflow velocity of 0 m/s the impedance and resistance increased slowly,while the reactance kept steady when air temperature decreased from 8.0°C to around−6.3°C,and then increased rapidly from around−6.3°C to−15.0°C.There were no significant differences of the above parameters and variation trend under different airflow velocities.There was an exponential relationship between the impedance and the temperature.The capacitance was rather small and almost no change occurred with air temperature under different conditions of air velocity and humidity,except a few abrupt peaks.The maximum peak capacitance was representative of its response at certain humidity and airflow velocity.The typical temperatures were close to a range,where the other three parameters began to increase rapidly.The typical temperature dropped to the lowest of−7.8°C at the airflow velocity of 0 m/s.Therefore,the characteristic response of the capacitance could indicate critical temperature of tea leaves.

电导法对32个辣椒品种组合抗寒性的测定及配合力分析

为了比较辣椒品种的抗寒性,以32个线椒杂交组合为试材,在人工气候箱下进行低温处理,应用电导法测定叶片相对电导率(REC)。通过Logistic曲线方程拟合求出拐点温度(即半致死温度)(LT50),作为各试材抗寒性评价的参考指标,并将32个线椒组合的半致死温度(LT50)进行比较。结果表明:随处理温度的降低,相对电导率不断升高,变化过程呈"S"型曲线。32个线椒组合抗寒性顺序依次为:H2>H13≈H28>H31≈H1≈H23>H24>H26>H30>H8>H27≈H19>H5≈H12>H21>H3>H18>H15≈H14>H22>H17>H7≈H29>H4>H11>H10≈H16>H20>H6>H9>H25>H32。配合力分析表明,相对电导率的GCA效应值以亲本P1和P2最低,SCA效应值以P1×P2最低。

Thermodynamic optimization and fluid selection of organic Rankine cycle driven by a latent heat source

Organic Rankine cycle(ORC) is applicable for the heat-work conversion. Whereas, there also exist a lot issues that influence the efficiency and the cost of the system. In this work, eleven pure working fluids(as categorized into alkanes, and fluorinated alkanes) are investigated based on the first and second law of thermodynamics. The major objective is to obtain the most suitable working fluid for the latent heat source. The results show that the working fluid is an important factor of the system performance. The heat absorption of the working fluid in the evaporator is inversely proportional to the evaporating temperature, but the thermal and exergetic efficiencies are just the opposite. RC318 has the highest net power output and the lowest outlet temperature of the heat source, but its global warming potential(GWP) value is too high. The cyclohexane shows the highest thermal efficiency among the fluids investigated. Moreover, the figure of merit(FOM) of the isobutane is higher than that of other working fluids. Overall, the cyclohexane shows that the optimal comprehensive performance is more feasible for medium grade heat source in engineering applications.

Hypocotyl elongation based on HY5 transcription factor in cold resistant winter rapeseed(Brassica napus L.)

Winter rape(Brassica napus L.)is better than other edible oil crops in China,but poor cold resistance is the key factor restricting its development.Hypocotyl length was found closely related to cold tolerance.The correlation between hypocotyl length and semi-lethal low temperature was significant,and the highest correlation between hypocotyl length and LT50 of autumn sowing was 0.9557.When the hypocotyl were treated at low temperature,the cells were seriously damaged and formed cavity structures,with cell walls seriously damaged or merged into each other.The positive regulation gene of hypocotyl length in resistant line of VHTSG 10 was identified as HY5(transcription factor HY5-like)by qPCR,and bZIP transcription factor was found to be its conserved domain.Fused gene by GFP and HY5 from VHTSG 10 was transient transferred into Nicotiana benthamiana cells.Corresponding to the 35S:GFP widely distributed in plasma membrane of leaf epidermis,the fusion protein 35S:HY5-GFP was mainly distributed in nucleus.Thus we regarded BnHY5 gene is a key gene related to cold tolerance and hypocotyl length in B.napus.

Test on dynamic characteristics of subgrade of heavy-haul railway in cold regions

Dynamic characteristics of heavy-haul railway subgrade under vibratory loading in cold regions are investigated via low-temperature dynamie triaxial tests with multi-stage eyelic loading process. The relationship between dynamic shear stress and dynamic shear strain of frozen soil of subgrade under train loading and the influence of freezing temperatures on dynamic constitutive relation, dynamic shear modulus and damping ratio are observed in this study. Test results show that the dynamic constitutive relations of the frozen soils with different freezing temperatures comply with the hyperbolic model, in which model parameters a and b decrease with increasing freezing temperature. The dynamic shear modulus of the frozen soils decreases with increasing dynamic shear strains initially, followed by a relatively smooth attenuation tendency, whereas increases with decreasing freezing temperatures. The damping ratios decrease with decreasing freezing temperatures. Two linear functions are defined to express the linear relationships between dynamic shear modulus （damping ratio） and freezing temperature, respectively, in which corresponding linear coefficients are obtained through multiple regression analysis of test data.

Low temperature densification mechanism and properties of Ta_(1-x)Hf_(x)C solid solutions with decarbonization and phase transition of Cr_(3)C_(2)

As a novel member of the ultra-high temperature ceramic family,which have extremely high melting points and remarkable hardness,Ta1-xHfxC solid solution ceramics are promising for applications in thermal protection systems.Ta_(1-x)Hf_(x)C(x=0,0.2,0.5,0.8,and 1.0)with 2 vol%Cr_(3)C_(2),were densified up to 98.8%at 2000℃ using a two-step spark plasma sintering process.Effect of Cr_(3)C_(2) on the linear shrinkage of Ta1-xHfxC was investigated.Possible‘eutectic’reaction within TaCeCr_(3)C_(2) ceramic was inferred to contribute to the shrinkage at 1462 C.High-angle annular dark-field scanning transmission electron microscopy combined with energy-dispersive spectroscopy was employed to further confirm the mutual diffusion between rock-salt structured‘CrCx’and TaC.Flexural strength,fracture toughness and Vicker’s hardness of Ta1-xHfxC ceramics were in the range of 439e492 MPa,4.0e5.8 MPa∙m^(1/2) and 14.9e19.9 GPa respectively.The coefficient of thermal expansion(in the temperature range of 25e1000℃)and thermal conductivity(at 1000℃)of Ta_(1-x)Hf_(x)C varied from 7.17 to 7.51×10^(-6) K^(-1) and 31.9e42.9 W/m·K,respectively.The high-temperature strength of Ta_(0.5)Hf_(0.5)C decreased to 165 MPa up to 1600℃,approximately 34%of room-temperature strength,and a‘zig-zag’load-displacement curve was observed.

Analysis on First-stage Ignition of n-Heptane at Low Temperatures with a Lumped Skeletal Mechanism

Two-stage ignition exists in the low-temperature combustion process of n-heptane and the first-stage ignition also shows a negative temperature coefficient(NTC) phenomenon. To study key reactions and understand chemical principles affecting the first-stage ignition of n-heptane, a lumped skeletal mechanism with 62 species is obtained based on the detailed NUIGMech1.0 mechanism using the directed relation graph method assisted by sensitivity analysis and isomer lumping. The lumped mechanism shows good performance on ignition delay time under wide conditions. The study revealed that the temperature after the first-stage ignition is higher and a larger amount of fuel is consumed at lower initial temperatures. The temperature at the first-stage ignition is relatively insensitive to the initial temperature. Further sensitivity analysis and reaction path analysis carried out based on the lumped mechanism show that the decomposition of RO_(2) to produce alkene and HO_(2) is the most important reaction to inhibit the first-stage ignitions. The chain branching explosion closely related to the first-stage ignition will be terminated when the rate constant for the RO_(2) decomposition is larger than that of the isomerization of RO_(2) to produce QOOH. The NTC behavior as well as other characteristics of the first-stage ignition can be rationalized from the competition between these two reactions.

Control of Secondary Phases by Solution Treatment in a N-Alloyed High-Mn Cryogenic Steel

The secondary phases of the steels have significant effects on the microstructure and mechanical properties, making controlling these secondary phases important. The control of MnS inclusions and A1N precipitates in a N-alloyed high-Mn twin-induced plastic cryogenic steel via solution treatment was investigated with several different techniques including microstructural characterization, 298 K tensile testing, and 77 K impact testing. The solutionizing temperature （ST） increased from 1323 to 1573 K, where the elongated MnS inclusions and large-sized AlN precipitates became spheroidized and dissolved. The aspect ratio of the MnS inclusions decreased as the ST increased and the number density increased. The impact toughness of the steels showed anisotropy and low impact energy values, due to the elongated MnS inclusions and large-sized AIN precipitates. The anisotropy was eliminated by spheroidizing the MnS inclusions. The impact energy was improved by dissolving the large-sized AlN precipitates during the solution treatment. The austenite grain size increased when the dissolution of the AlN precipitate increased, but the effect of the grain size on the yield strength, toughness, and the strength--ductility balance was weak.

Sintering behaviour and microwave dielectric properties of MgO-2B_(2)O_(3)--xwt%BaCu(B_(2)O_(5))-ywt%H_(3)BO_(3) ceramics

This study investigates the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) series ceramics synthesised by solid-state reaction.According to the X-ray diffraction and microstructural analyses,the as-prepared MgO-2B_(2)O_(3) ceramics possess a single-phase structure with a rod-like morphology.The effects of different quantities of H_(3)BO_(3) and BaCu(B_(2)O5)(BCB)on the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) ceramics were investigated.Accordingly,the optimal sintering temperature was obtained by adding 30 wt%H_(3)BO_(3) and 8 wt%BCB.We also reduced the sintering temperature to 825°C.Furthermore,the addition of 40 wt%H_(3)BO_(3) and 4 wt%BCB increased the quality factor,permittivity,and temperature coefficient of resonance frequency of MgO-2B_(2)O_(3) to 44,306 GHz(at 15 GHz),5.1,and-32 ppm/℃,respectively.These properties make MgO-2B_(2)O_(3) a viable low-temperature co-fired ceramic with broad applications in microwave dielectrics.