Dependence of impact regime boundaries on the initial temperatures of projectiles and targets

Towards higher impact velocities,ballistic events are increasingly determined by the material temperatures.Related effects might range from moderate thermal softening to full phase transition.In particular,it is of great interest to quantify the conditions for incipient or full melting of metals during impact interactions,which result in a transition from still strength-affected to hydrodynamic material behavior.In this work,we investigate to which extent the respective melting thresholds are also dependent on the initial,and generally elevated,temperatures of projectiles and targets before impact.This is studied through the application of a model developed recently by the authors to characterize the transition regime between high-velocity and hypervelocity impact,for which the melting thresholds of materials were used as the defining quantities.The obtained results are expected to be of general interest for ballistic application cases where projectiles or targets are preheated.Such conditions might result,for example,from aerodynamic forces acting onto a projectile during atmospheric flight,explosive shapedcharge-jet formation or armor exposure to environmental conditions.The performed analyses also broaden the scientific understanding of the relevance of temperature in penetration events,generally known since the 1960s,but often not considered thoroughly in impact studies.

Influence of High Temperature Stress on Net Photosynthesis, Dry Matter Partitioning and Rice Grain Yield at Flowering and Grain Filling Stages

Climate change is recognized to increase the frequency and severity of extreme temperature events. At flowering and grain filling stages, risk of high temperature stress （HTS） on rice might increase, and lead to declining grain yields. A regulated cabinet experiment was carried out to investigate effects of high temperature stress on rice growth at flowering and grain- filling stages. Results showed that no obvious decrease pattern in net photosynthesis appeared along with the temperature rising, but the dry matter allocation in leaf, leaf sheath, culm, and panicle all changed. Dry weight of panicle decreased, and ratio of straw to total above ground crop dry weight increased 6-34% from CK, which might have great effects on carbon cycling and green house gas emission. Grain yield decreased significantly across all treatments on average from 15 to 73%. Occurrence of HTS at flowering stage showed more serious influence on grain yield than at grain filling stage. High temperature stress showed negative effects on harvest index. It might be helpful to provide valuable information for crop simulation models to capture the effects of high temperature stress on rice, and evaluate the high temperature risk.

Effect of quenching temperature on the microstructure of Si-containing steel during quenching and partitioning

This study aims to investigate the effect of the 1-step quenching and partitioning （Q＆P） process on the microstructure and the resulting Vicker＇ s hardness of 0.3C-1.5Si-1.5Mn steel by using in-situ dilatometry ,optical microscopy （ OM ）, scanning electron microscopy （ SEM ）, X-ray diffractometry （ XRD ）, and Vicker ＇ s hardness measurement. Systematic analyses indicate that the microstructure of the specimens quenched and partitioned at 150℃ ,200 ℃ ,250℃ ,and 300℃ mainly comprises lath martensite and retained austenite. The dilatometry curve of the specimen partitioned at 150℃ is presumably ascribed to the formation of isothermal martensite. In the early stages of partitioning at 200℃,the nearly unchanged dilatation curve is closely related to the synergistic effect of isothermal martensite formation and transitional epsilon carbide precipitation. In the later stages of partitioning at 200 ℃ ,the slight increase in the dilatation curve is due to the continuous isothermal martensite formation. With further increase in partitioning temperature to 250℃, the dilatation increases gradually up to 3600 s, which is related to carbon partitioning and lower bainite formation. Partitioning at a higher temperature of 300 ℃ causes a rapid increase in the dilatation curve during the initial stages, which subsequently levels off upon prolonging the partitioning time. This is mainly attributed to the rapid diffusion of carbon from athermal martensite to retained austenite and continuous formation of lower bainite.

PARTITION RATIO AT SOLID-LIQUID INTERFACE UNDER INFLUENCE OF TEMPERATURE GRADIENT AND EXTERNAL FORCE FIELD

The relationship between the partition ratio at a solid-liquid interface and the temperature gradient or the external force field has been theoretically analysed.It is shown that under the influence of a temperature gradient or an external force field,the partition ratio at a solid-liquid interface will deviate from the equilibrium value.

Multifunctional interlayer with simultaneously capturing and catalytically converting polysulfides for boosting safety and performance of lithium-sulfur batteries at high-low temperatures

Lithium-sulfur(Li-S) batteries as extremely promising high-density energy storage devices have attracted extensive concern. However, practical applications of Li-S batteries are severely restricted by not only intrinsic polysulfides shuttle resulting from their concentration gradient diffusion and sluggish conversion kinetics but also serious safety issue caused by thermolabile and combustible polymer separators.Herein, it is presented for the first time that a robust and multifunctional separator with urchin-like Co-doped Fe OOH microspheres and multiwalled carbon nanotubes(MWCNTs) as an interlayer simultaneously achieves to suppress polysulfides shuttle as well as improves thermotolerance and nonflammability of commercial PP separator. Accordingly, Li-S batteries with modified separator exhibit remarkable performance in a wide range temperatures of-25–100 ℃. Typically, under 25 ℃, ultrahigh initial capacities of 1441 and 827.29 m A h g-1 at 1 C and 2 C are delivered, and remained capacities of 936 and 663.18 mA h g-1 can be obtained after 500 cycles, respectively. At 0.1 C, the S utilization can reach up to 97%. Significantly, at 1 C, the batteries also deliver an excellent performance with remained capacities of high to862.3, 608.4 and 420.6 m A h g-1 after 100, 300 and 450 cycles under 75, 0 and-25 ℃, respectively. This work provides a new insight for developing stable and safe high-performance Li-S batteries.

Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining

The hot deformation characteristics of 1.4462 duplex stainless steel （DSS） were analyzed by considering strain partitioning between austenite and ferrite constituents. The individual behavior of ferrite and austenite in microstructure was studied in an iso-stress condition. Hot compression tests were performed at temperatures of 800-1100~C and strain rates of 0.001-1 s-1. The flow stress was modeled by a hyperbolic sine constitutive equation, the corresponding constants and apparent activation energies were determined for the studied alloys. The constitutive equation and law of mixture were used to measure the contribution factor of each phase at any given strain. It is found that the contribution factor of ferrite exponentially declines as the Zener-HoUomon parameter （Z） increases. On the contrary, the austenite contribution polynomially increases with the increase of Z. At low Z values below 2.6. x 1015 （lnZ---35.5）, a negative contribution factor is determined for austenite that is attributed to dynamic recrystallization. At high Z values, the contribution factor of austenite is about two orders of magnitude greater than that of ferrite, and therefore, austenite can accommodate more strain. Microstructural characterization via electron back-scattered diffraction （EBSD） confirms the mechanical results and shows that austenite recrystallization is possible only at high temperature and low strain rate.

Line intensities of the asymptotic asymmetric-top radical HO_2 at high temperatures

The total internal partition sums were calculated in the product approximation at temperatures up to 5000 K for the asymptotic asymmetric-top HO2 molecule. The calculations of the rotational partition function and the vibrational partition function were carried out with the rigid-top model and in the harmonic oscillator approximation, respectively. Our values of the total internal partition sums are consistent with the data of HITRAN database with -0.14% at 296 K. Using the calculated partition functions, we have calculated the line intensities of υ2 band of HO2 at several high temperatures. The results showed that the calculated line intensities are in very good agreement with those of HITRAN database at temperatures up to 3000 K, which provides a strong support for the calculations of partition functions and line intensities at high temperatures. Then we have extended the calculation to higher temperatures. The simulated spectra of υ2 band of the asymptotic asymmetric-top HO2 molecule at 4000 and 5000 K are also obtained.

Study on high-temperature spectra of asymptotic asymmetric-top radical SiO_2

Total internal partition sums are calculated in the product approximation at temperatures up to 6000K for the asymptotic asymmetric-top SiO2 molecule. The rotational partition function and the vibrational partition function are calculated with the rigid-top model and in the harmonic oscillator approximation, respectively. Our values of the total internal partition sums are consistent with the calculated value in the Gaussian program within $-0.137$% at 296K. Using the calculated partition functions and the rotationless transition dipole moment squared as a constant, we calculate the line intensities of 001--000 band of SiO2 at normal, medium and high temperatures. Simulated spectra of the 001--000 band of the asymptotic asymmetric-top SiO2 molecule at 2000, 5000 and 6000K are also obtained.

High Temperature Spectrum for v3 Band of Carbon Dioxide

全部的内部分区和(尖端) 为 ~(12 ) 在温度被计算直到 6000 K C~(16 ) O_2。用计算分区函数，我们生产ν _ 的线紧张 ~(12 ) 的 3 乐队在几高温度的 C~(16 ) O_2。结果证明计算的线紧张在在直到 3000 K 的温度的 HITRAN 数据库的对那些的很好的同意，它在高温度为尖端和线紧张的计算提供强壮的支持。然后，计算被扩大推进高温度，和ν _ 的模仿的系列 ~(12 ) 的 3 乐队在 5000 和 6000 K 的 C~(16 ) O_2 被报导。

Temperature cycling and its effect on mechanical behaviours of highporosity chalks

Temperature history can have a significant effect on the strength of water-saturated chalk.In this study,hydrostatic stress cycles are applied to understand the mechanical response of chalk samples exposed to temperature cycling between each stress cycle,compared to the samples tested at a constant temperature.The total accumulated strain during a stress cycle and the irreversible strain are reported.Chalk samples from Kansas (USA) and Mons (Belgium),with different degrees of induration (i.e.amount of contact cementation),were used.The samples were saturated with equilibrated water (polar) and nonpolar Isopar H oil to quantify water weakening.All samples tested during 10 stress cycles with varying temperature (i.e.temperature cycled in between each stress cycle) accumulated more strain than those tested at constant temperatures.All the stress cycles were performed at 30 ℃.The two chalk types behaved similarly when saturated with Isopar H oil,but differently when saturated with water.When saturated with water,the stronger Kansas chalk accumulated more total strain and more irreversible strain within each stress cycle than the weaker Mons chalk.

Study on High-Temperature Spectra of Asymptotic Asymmetric-Top Molecule O_3

The line intensities of 001-000 transition of the asymptotic asymmetric-top 03 molecule at several tem- peratures are calculated by directly calculating the partition functions and regarding the rotationless transition dipole moment squared as a constant.The calculated values of the total internal partition sums (TIPS) are consistent with the data of HITRAN database with -0.61% at 296 K.The calculated line intensity data at 500 K and 3000 K are also in excellent agreement with the data in HITRAN database with less than 0.659% and 5.458% at 500 K and 3000 K, which provide a strong support for the calculations of partition function and line intensity at high temperature.Then we extend the calculation to higher temperatures.The line intensities and simulated spectra of v_3 band of the asymptotic asymmetric-top O_3 molecule at 4000 and 5000 K are reported.The results are of significance for the studying of the molecular high-temperature spectrum including experimental measurements and theoretical calculations.

Growth and Yield Responses of Switchgrass Ecotypes to Temperature

Varietal differences of switchgrass in growth and development, biomass yield and partitioning in response to temperature are not well documented. A study was conducted to quantify the effect of temperature on growth, development, and feedstock quality of switchgrass cultivars, and to determine differences between upland and lowland switchgrass. Two lowland (“Alamo” and “Kanlow”) and two upland (“Caddo” and “Cave-in-Rock”) cultivars of switchgrass were grown in pots filled with pure, fine sand in growth chambers. Four different temperature treatments of 23℃/15℃, 28℃/20℃, 33℃/25℃, and 38℃/30℃ with 14/10 hours day/night were imposed at four leaf stage. High temperature significantly decreased the biomass yield across all cultivars. Stem elongation rate (SER) and leaf elongation rate (LER) decreased at the highest temperature treatment but lowland cultivars had significantly higher SER and LER across the temperature treatments. Upland cultivars produced more tillers across the temperature treatment. Both shoot/root and leaf/stem ratios increased under the highest temperature in all cultivars, but upland cultivars partitioned more to the leaf and root at higher temperature. Concentration of cellulose decreased at the highest temperature but temperature had no effect on lignin concentration of leaf and stem biomass. In conclusion, although none of the cultivars studied showed strong tolerance to high temperature, differences were observed for many traits of switchgrass in response to temperature.

CONVECTIVE-STRATIFORM RAINFALL PARTITION BY RADIANCE-DERIVED CLOUD CONTENT:A MODELING STUDY

A new scheme that separates convective-stratiform rainfall is developed using threshold values of liquid water path(LWP) and ice water path(IWP).These cloud contents can be predicted with radiances at the Advanced Microwave Sounding Unit(AMSU) channels(23.8,31.4,89,and 150 GHz) through linear regression models.The scheme is demonstrated by an analysis of a two-dimensional cloud resolving model simulation that is imposed by a forcing derived from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment(TOGA COARE).The rainfall is considered convective if associated LWP is larger than 1.91 mm or IWP is larger than1.70 mm.Otherwise,the rainfall is stratiform.The analysis of surface rainfall budget demonstrates that this new scheme is physically meaningful.

The partitioning patterns of nutrients between pods and seeds of Zanthoxylum fruits impacted by environmental factors

The nutritive quality in plant organs is related to the different partitioning patterns of nutrient resources among the organs under various environmental conditions.This study examined the relationship between the nutritive quality of pods and seeds in Zanthoxylum and environmental factors, such as temperature and preciptation by using numerous samples collected from Southwest China to the East China of Shandong peninsula. The increasing accumulations of N, P and C in seeds implied that the nutritive quality in seeds was higher at the regions with relative higher mean annual temperature(MAT) and mean annual precipitation(MAP), while that in pods was on the contrary. By contrast, pod nutritive content was relatively high, but seed nutritive content was relatively low at the regions with relative high MAT and MAP. In addition, C:N ratio in pods was significantly and negatively correlated with MAT and MAP, while that in seed was significantly and positively correlated with MAT and MAP. The partitioning patterns of N-compounds between pods and seeds reflected different nitrogen translocations in the plant organs under various climate condition. The N:P ratios were negatively correlated with MAP, implying a higher proportional allocation of P to seeds than that of N in the areas with a relative high MAP. Therefore, the strategies to assess pod nutritional quality should be taken into accountfor nutritive translocation under various environmental conditions.

基于高低温分区热管网络的高轨通信卫星散热能力提升方法

针对我国高轨通信卫星不断提升的散热需求,提出采用基于高低温分区热管网络的热设计方法。在分析热管网络散热能力的基础上,进行设备分区布局设计、分区热管网络散热面设计和分区热管网络布局设计。该方法可在保证卫星仪器设备工作温度、不降低热设计可靠性、不增加分系统重量及功率需求的前提下,将卫星散热能力提升15%~20%。文章还结合近些年通信卫星研制中的经验和教训,归纳给出高低温分区热管网络设计中的注意事项,以期为相关工程设计提供有效指导。

基于机器学习的格点气温预报订正方法

使用2017年9月至2021年3月国家级业务化运行的智能网格实况分析产品和欧洲中期天气预报中心全球模式(EC)产品,根据湖北省的地理分布特征构建6个分区,采用基于LightGBM机器学习算法建立的气温预报方法,生成湖北省0.05°×0.05°格点气温预报产品。利用2021年4—9月的预报产品和格点实况资料进行检验,结果表明:基于机器学习的气温预报方法(MLT)取得了较好的预报效果,其在0~72 h时效内优于中央气象台下发的气温精细化指导预报(SCMOC)和EC产品;MLT在山区的误差较平原大,但山区的订正幅度大于平原,日最高气温的订正幅度大于日最低气温的订正幅度;4—9月MLT、SCMOC、EC产品的平均绝对误差(MAE)日变化都呈现了白天偏高、夜间偏低、午后凸起的单峰特征,MLT的MAE值较SCMOC和EC产品的更低,并且在转折性天气中仍具有优势;站点检验与格点检验结论一致,基于格点建模的气温预报产品对站点预报同样得到了订正。机器学习在格点气温的模式订正方面可以作为一个行之有效的手段。

Tensile behavior and deformation mechanism of quenching and partitioning treated steels at different deforming temperatures

The effects of deforming temperatures on the tensile behaviors of quenching and partitioning treated steels were investigated. It was found that the ultimate tensile strength of the steel decreased with the increasing temperature from 25 to 100 ℃, reached the maximum value at 300 ℃, and then declined by a significant extent when the temperature further reached 400 ℃. The total elongations at 100, 200 and 300 ℃are at about the same level. The steel achieved optimal mechanical properties at 300 ℃due to the proper transformation behavior of retained austenite since the stability of retained austenite is largely dependent on the deforming temperature. When tested at 100 and 200 ℃, the retained aus tenite was reluctant to transform, while at the other temperatures, about 10 vol. % of retained aus- tenite transformed during the tensile tests. The relationship between the stability of retained austenite and the work hardening behavior of quenching and partitioning treated steels at different deforming temperatures was also studied and discussed in detail. In order to obtain excellent mechanical properties, the stability of retained austenite should be carefully controlled so that the effect of transforma tion-induced plasticity could take place continuously during plastic deformation.

淬火冷却温度对工程机械用中锰钢淬火-配分后组织与性能的影响

对热轧态中锰钢进行淬火-配分处理,研究了淬火冷却温度(195,220,255,280℃)对其显微组织、物相组成、硬度和拉伸性能的影响。结果表明:淬火-配分处理后中锰钢中存在板条马氏体、块状马氏体和残余奥氏体;随着淬火冷却温度升高,板条马氏体含量减少,块状马氏体含量增加,残余奥氏体体积分数先增大后减小,当淬火冷却温度为220℃时最大,为19.81%;随着淬火冷却温度的升高,中锰钢的硬度增大,抗拉强度、屈服强度和断后伸长率先增大后减小,当淬火冷却温度为220℃时中锰钢的断后伸长率和强塑积最大,分别为15.6%和23.76 GPa·%。

基于分区模型的液氢贮箱地面温度与压力分布研究

针对传统商用软件计算液氢贮箱热分层时的计算量大且耗时长等问题,运用分区模型方法将地面液氢贮箱内部空间分为过热区、饱和区和过冷区3块区域,并离散气相/液相区的质量与能量守恒方程和热力学方程,在确定初始条件便求解液氢贮箱内温度与压力分布。对比分区模型与Fluent计算结果可知,该方法在大幅降低计算资源情况下,可获得液氢贮箱内温度与压力的精确分布,为后续流体混合计算提供初始条件。

隔姜灸温度-时间曲线分析

目的观察隔姜灸的温度-时间曲线的特点。方法将500 mg艾绒用底部直径15 mm、高度20 mm的模具做成圆锥型的艾炷,将艾炷置于厚度3 mm、直径25 mm的鲜生姜片上点燃,用红外热像仪系统,每30 s记录储存姜片底部的热像图,并进行分析处理,同样的实验重复进行3次,3次测得的姜片底部温度的平均值作为结果进行分析。结果500 mg的艾炷从点燃到燃烧完毕,姜片底部温度回到基本接近未施灸前的温度时的总时程是15 min。初始温度(点燃艾炷前的温度)为(27.7±0.2)℃。艾炷点燃后3 min,温度逐步上升,在第5.5分钟时,艾炷燃烧完毕,此时的姜片底部温度上升到(55.2±2.3)℃。在第7分钟时,姜片底部的温度达到最高峰的(60.7±1.2)℃。姜片底部的温度维持在(55.2±2.3)℃至(60.7±1.2)℃的时间达4.5 min。随后,在第10分钟,温度开始逐步下降,到第15分钟时姜片底部温度接近未施灸前的水平(29.3±0.9)℃。结论隔姜灸的温度时间曲线表现为温度逐步上升达到高峰,在高峰温度的时间较长,形成温度-时间曲线高峰中的平台,然后温度逐步下降的特点。