Cooling rate controlled basal precipitates and age hardening response of solid-soluted Mg-Gd-Er-Zn-Zr alloy

The precipitation and age hardening response of the solid-soluted Mg–10Gd–1Er–1Zn–0.6Zr(wt.%)alloy performed by water-quenching(QC),air-cooling(AC)and furnace-cooling(FC)in terms of the volume fraction of precipitates and tensile properties were investigated in present paper.Results indicated the solid-soluted alloy contained stacking faults(SFs)and long period stacking ordered(LPSO)phase on the basal planes regardless of the cooling rate,but a larger volume fraction of the LPSO phase was formed with decreasing in the cooling rate.After aging,βandβ1 phases precipitated on the prismatic planes,and their number density decreased but mean particle size increased with decreasing in the cooling rate.The solid-soluted alloys(QC,AC and FC samples)showed no apparent difference in yield strength(YS),but their correspondent peak-aged alloys exhibited sharp difference in hardening response.The strongest hardening response took place in the QC sample and showed 82MPa enhancement in YS,which was much larger than that of AC(+26MPa)and FC samples(+5MPa).The reason lies in that the higher cooling rate promotes the precipitation and reduces the average size ofβprecipitate.A novel cooling-rate controlled precipitation model with respect to the correlation of precipitates on basal and prismatic planes was established.From this model,the basal precipitates showed a restrictive effect on the growth and/or coarsening ofβprecipitate,and composite precipitates containing theβphase with fine size as well as high area-number density and lower volume fraction of the LPSO phase are preferred to strengthen the Mg–10Gd–1Er–1Zn–0.6Zr alloy.

Innovative Design and Additive Manufacturing of Regenerative Cooling Thermal Protection System Based on the Triply Periodic Minimal Surface Porous Structure

The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of hypersonic vehicles.Triply periodic minimal surface(TPMS)is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics.In this study,test pieces were manufactured using Ti6Al4V lightweight material.We designed three types of porous test pieces,and the interior was filled with a TPMS lattice(Gyroid,Primitive,I-WP)with a porosity of 30%.All porous test pieces were manufactured via selective laser melting technology.A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system.Hence,the relationship between the geometry and mechanical properties of a unit cell is established,and the deformation mechanism of the porous unit cell is clarified.Among the three types of porous test pieces,the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%,the average tensile strength was reduced by 17.7%compared to the solid test piece,while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5%and 33.3%,respectively.Compared with the other two types of unit cells,Gyroid exhibited better mechanical conductivity characteristics.Its deformation process was characterised by stretching,shearing,and twisting,while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation,respectively.The finite element predictions in the study agree well with the experimental results.The results can provide a basis for the design of regenerative cooling thermal protection system.

DFA-ODENets:面向周期多阶段复杂系统的预测仿真框架

部分复杂系统受内外部因素影响在运行时会呈现出周期性的阶段变化,且在不同阶段具有完全不同的动态特性.因此在使用数据驱动方法解决此类系统的预测和仿真问题时,使用单一结构模型难以准确地学习系统在不同阶段的动态特性.本研究提出了基于确定性有限状态机-常微分方程网络的预测仿真框架(DFA-ODENets),以建模周期多阶段系统.该模型由多个ODENet组成,每个ODENet能够从不规则采样的序列数据中学习系统在各个阶段内的动态特性.同时模型集成了基于确定性有限状态自动机思想的阶段转换预测器以实现模型预测时在不同阶段之间自动转换.最后,将DFA-ODENet框架应用于某计算中心制冷系统的预测仿真场景中.模型能够在给定系统运行过程中的服务器负载和环境温度下模拟系统运行过程,并对系统的制冷功率、进气口温度等主要输出变量进行预测.其中,对于制冷系统能耗预测的平均相对误差在5%以内.同时,利用制冷系统仿真模型优化了系统停止制冷时的温度设定值,通过仿真实验表明该优化最高可以节省18%的制冷能耗.

Thermoelastic stress analysis of multilayered films in a micro-thermoelectric cooling device

This paper presents an analytical solution for the thermoelastic stress in a typical in-plane＇s thin-film micro- thermoelectric cooling device under different operating con- ditions. The distributions of the permissible temperature fields in multilayered thin-films are analytically obtained, and the characteristics, including maximum temperature dif- ference and maximum refrigerating output of the thermo- electric device, are discussed for two operating conditions. Analytical expressions of the thermoelastic stresses in the layered thermoelectric thin-films induced by the tempera- ture difference are formulated based on the theory of mul- tilayer system. The results demonstrate that, the geometric dimension is a significant factor which remarkably affects the thermoelastic stresses. The stress distributions in layers of semiconductor thermoelements, insulating and support- ing membrane show distinctly different features. The present work may profitably guide the optimization design of high- efficiency micro-thermoelectric cooling devices.

Effect of cooling rate on evolution of superconducting phases during decomposition and recrystallization of (Bi,Pb)-2223 core in Ag-sheathed tape

The reformation of (Bi,Pb)-2223 from the liquid or melt is very important for a melting process of (Bi,Pb)-2223 tape. By combination of quenching experiment with X-ray diffraction (XRD) analysis, the effect of cooling rate on the evolution of three superconducting phases in the (Bi,Pb)-2223 core of Ag-sheathed tape was investigated. The results show that (Bi,Pb)-2223 reformation from the melt seems to experience different routes during slowly cooling at different rates. One is that (Bi,Pb)-2223 phase reformed directly from the melt, and no Bi-2212 participate in this process. The other is that (Bi,Pb)-2223 is converted from the intermediate product, Bi-2212, which formed from the melt during the first cooling stage. Due to the inherent sluggish formation kinetics of (Bi,Pb)-2223 from Bi-2212, only partial (Bi,Pb)-2223 can finally be reformed with the second route.

Periodic oscillation and fine structure of wedge-induced oblique detonation waves

An oblique detonation wave for a Mach 7 inlet flow over a long enough wedge of 30 turning angle is simulated numerically using Euler equation and one-step rection model.The fifth-order WENO scheme is adopted to capture the shock wave.The numerical results show that with the compression of the wedge wall the detonation wave front structure is divided into three sections：the ZND model-like strcuture,single-sided triple point structure and dual-headed triple point strucuture.The first structure is the smooth straight,and the second has the characteristic of the triple points propagating dowanstream only with the same velocity,while the dual-headed triple point structure is very complicated.The detonation waves facing upstream and downstream propagate with different velocities,in which the periodic collisions of the triple points cause the oscillation of the detonation wave front.This oscillation process has temporal and spatial periodicity.In addition,the triple point trace are recorded to obtain different cell structures in three sections.

基于生物质气化的内燃机-吸收式制冷联合冷热电系统分析

可再生能源发电技术是解决能源短缺和环境污染问题的有效途径之一,本文提出了基于生物质气化的联合冷热电(combined cooling heating and power,CCHP)系统。该系统以生物质气化气为燃料,通过内燃机(internal combustion engine,ICE)发电。为提高燃料的整体利用水平,对内燃机排气的低温余热由吸收式制冷及热水系统进行回收。气化炉模型考虑了热解、还原及氧化反应,内燃机模型考虑了气缸内压力、温度随转角的变化。对于单效溴化锂–水吸收式制冷单元,研究了发生器和吸收器工作温度对制冷量的影响。研究结果表明:采用气化气为燃料的内燃机热效率可达37%。增大内燃机转速使系统电效率提高2%,整体冷热电效率为47%;压缩比的增大使系统电效率提高1%,冷热电效率几乎不变。降低吸收器工作温度和提高发生器工作温度可增大制冷量并提高制冷性能,效能系数可以达到77%。整个联合冷热电系统的电效率为22%,冷热电联合效率可以达到48%,投资回收期为3~4 a。

2022-2023年黑龙江省1月延伸期强降温过程预报检验

利用黑龙江省83个气象观测站2022年和2023年1月的逐日温度资料,以单站日平均温度24 h内降温幅度>8℃为标准,对强降温事件进行统计,并对CFSv2延伸期预报进行检验。结果表明:两年共发生6次强降温过程,发布延伸期强降温过程12次,预报准确率为33%,空报过程10次,漏报4次,2023年预报准确率高于2022年。对比不同预报时效的结果,发现延伸期预报效果与起报时间并没有显著联系。CFSv2模式对大范围强降温过程的预报有一定技巧,超前10 d预报的旬气温距平也具有参考价值,与实况相比,延伸期强降温过程预报的时段和强度略有偏差,但是预报的变化趋势基本一致,可以为黑龙江省1月强降温预报提供参考。

A New Critical Value Concerning the Genealogy of Long Period Families at L_4 in the Restricted Three-body Problem

We found another critical mass ratio value -↑μ between μ4 and μ5 concerning the genealogy of the long period family around the equilateral equilibrium point L4 in the restricted three-body problem. This value has not been pointed out before. We used numerical computations to show how the long period family evolves around this critical value. The case is similar to that of the critical values between μ2 and μ4, with slight difference in evolution details.

On the Period Variation of the W UMa-type Contact Binary V502 Ophiuchi

The variation in the orbital period of the W UMa type contact binary V502 Oph is analyzed. The orbital period exhibits a wavelike variation with a periodicity of 23.0 years and an amplitude of AP = 1.24 ×10^-5 days superimposed on secular decrease of dP/dt = 1.68× 10^-7 day per year. The long-term decrease may be accompanied by the contraction of the secondary at a rate of 83 m per year and a mass transfer rate from the primary to the secondary of 4.28×10^-8M· per year. The short-term oscillation may be explained by the presence of a third component. Orbital elements of the third body and its possible mass are presented.

Performance analysis of thermal storage unit with possible nano enhanced phase change material in building cooling applications

The heat transfer performance of the phase change materials used in free cooling and air conditioning applications is low,due to the poor thermal conductivity of the materials.The recent phenomenal advancement in nano technology provides an opportunity for an appreciable enhancement in the thermal conductivity of the phase change materials.In order to explore the possibilities of using nano technology for various applications,a detailed parametric study is carried out,to analyse the heat transfer enhancement potential with the thermal conductivity of the conventional phase change materials and nano enhanced phase change materials under various flow conditions of the heat transfer fluid.Initially,the theoretical equation,used to determine the time for outward cylindrical solidification of the phase change material,is validated with the experimental results.It is inferred from the parametric studies,that for paraffinic phase change materials with air as the heat transfer fluid,the first step should be to increase the heat transfer coefficient to the maximum extent,before making any attempt to increase the thermal conductivity of the phase change materials,with the addition of nano particles.When water is used as the phase change material,the addition of nano particles is recommended to achieve better heat transfer,when a liquid is used as the heat transfer fluid.

Effects of Electrical Stimulation During Absolute Refractory Period on Contraction and Relaxation of Cardiomyocytes from Normal Guinea - pigs

Objectives To investi-gate the effect of electrical stimulation during absolute refractory period on contraction and relaxation of ventricular myocytes from normal guinea - pigs. Methods The guinea - pig ventricular myocytes were obtained by enzyme digesting, and the extent of its contraction and relaxation and Ca2+ transient were recorded through the motion edge detection system. Results (1) The contracting extent of guinea - pig ventricular myocytes increased 15.45±6.48% , and the peak velocity of shorting (contraction) and the peak veloci ty of relengthening (relaxation) increased 15.97 ± 8.37% and 21. 63±8. 06% respectively (n = 10); (2) The extent of ventricular myocytes fluorescence ra tio(360/380) (F360/F380) increased 22. 55±9. 08%, and the peak velocity of ventricular myocytes F360 /F380 increased 36. 75 ± 9. 77% and 23. 62±4. 47% during shorting and relengthening respectively (n = 6) . Conclusions Appropriate electrical stimulation may strengthen the contracting and relaxing function of normal guinea - pig ventricular myocytes.

5-单硝酸异山梨酯结晶工艺研究

5-单硝酸异山梨酯主要用于预防心绞痛、治疗冠心病、心肌梗死以及持续性心绞痛,适宜的结晶工艺是药物生产的关键。采用动态法测定了5-单硝酸异山梨酯在乙二醇中的溶解度,使用Apelblat model,Van’t Hoff model对溶解度数据进行了拟合,采用降温结晶法研究5-单硝酸异山梨酯在乙二醇中的结晶介稳区和诱导期,考察了初始浓度、搅拌速率、降温速率、终点温度和晶种加入量等因素对5-单硝酸异山梨酯降温结晶收率的影响,并进行了工艺条件优化。结果表明,适宜的操作条件为初始浓度1.797 mol/L,搅拌速率400 r/min,降温速率0.9 K/min,终点温度273 K,晶种加入量为溶质质量的0.5%,在该条件下收率为33.2%。该研究为5-单硝酸异山梨酯结晶新工艺的开发提供了依据。

生物钟基因Period2对卵巢癌裸鼠移植瘤生长抑制作用的机制研究

目的:探讨生物钟基因Period2对卵巢癌裸鼠移植瘤生长抑制的作用机制。方法:采用卵巢癌SKVO3细胞株构建裸鼠卵巢癌移植瘤,利用基因转染技术外源性导入重组基因质粒Period2。采用Real-time PCR法和Western bolt法检测移植瘤中Period2表达,治疗期间测量移植瘤体积。治疗后2周处死裸鼠,称取瘤重,采用Real-time PCR和Western blot法检测肿瘤组织中Bcl-2和Bax基因的表达。结果:外源性导入Period2基因在裸鼠移植瘤肿瘤组织中成功稳定表达。与对照组比较,Period2基因过表达组的肿瘤生长速度减慢,肿瘤体积和重量降低,抑瘤率升高,凋亡基因Bax表达明显升高,凋亡抑制基因Bcl-2表达明显降低,差异均有统计学意义(P<0.05)。结论:Period2可能通过下调肿瘤凋亡抑制基因Bcl-2,促进凋亡基因Bax表达,促进肿瘤细胞凋亡,从而抑制卵巢癌的生长转移,发挥抑瘤作用。

热变形过程中γ→α相变开始温度的预测——C-Mn钢与Nb-v微合金钢

以Cahn理论和Scheil法则为基础,讨论了热变形过程对γ α相变的影响,预测了C Mn钢变形过程铁素体析出的开始温度Ar3d和Nb V钢连续冷却转变开始温度Ar3·结果表明,同样变形条件下,碳含量或锰含量越低的钢种Ar3d越高;同一成分钢种,随着变形量增大或变形速率降低Ar3d提高;随着冷却速率的增加,Ar3温度降低;变形可以提高Ar3温度·用该方法进行的计算机模拟结果和实验结果吻合良好,表明这种理论处理方法可用来模拟这种相变过程·

周期性喷雾蒸发冷却最佳气-水比的试验研究

喷雾蒸发冷却是一种高效的冷却方式。采用试验的方法研究了周期性喷雾蒸发冷却气-水比的变化对换热器换热性能的影响。结果表明,在不同气-水总压力、不同进水温度下,存在一个最佳气-水压力比(1.0),相应的气-水质量比为0.31。

HTR-10物理实验方法及数据处理

针对高温气冷实验反应堆(HTR-10)的实际情况,重点介绍了周期法的原理以及在各项物理实验中的应用。特别分析了实验数据的选取和处理原则,利用Excel强大的数据处理能力进行数据处理和分析的方法,并用多种方法分析了测量数据的有效性。

北疆冷凉区玉米品种筛选试验

为了提高玉米产量,促进农业增产、农民增收,开展了品种筛选试验,以筛选出适宜北疆冷凉区种植的优良玉米品种。结果表明,参试的13个玉米品种熟期相对适中,各品种生育期均早于对照丰垦139,早熟2~7 d,说明各品种在此种植区域皆能安全成熟。KWS9384、兆合402、新玉76、KWS7461这4个品种综合性状表现优良,产量超过对照丰垦139,增产幅度6.24%~11.76%,其中以KWS9384增产较明显,增产幅度达11.76%;KWS7461虽然较丰垦139增产,但其株高、穗位高较高,生产上易发生倒伏;吉单494产量略低于对照丰垦139,但熟期适中,抗倒伏能力强,收获时籽粒含水率较低。综合分析各玉米品种的生育期、产量等因素,适宜北疆冷凉区种植的优良玉米品种有KWS9384、兆合402、新玉76和吉单494。

The biosynthesis of alarm pheromone in the wheat aphid Rhopalosiphum padi is regulated by hormones via fatty acid metabolism

Aphids are major insect pests in agriculture and forestry worldwide.Following attacks by natural enemies,many aphids release an alarm pheromone to protect their population.In most aphids,the main component of the aphid alarm pheromone(AAP)is the sesquiterpene hydrocarbon(E)-β-farnesene(EβF).However,the mechanisms behind its biosynthesis and regulation remain poorly understood.In this study,we used the bird cherry–oat aphid Rhopalosiphum padi,which is an important wheat aphid,to investigate the regulatory mechanisms of EβF biosynthesis.Our results showed that EβF biosynthesis occurs during the mature embryo period and the molting period of the 1st-and 2nd-instar nymphs.Triglycerides provide the prerequisite material for EβF production and release.Based on transcriptome sequencing,RNAi analysis,hormone treatments,and quantitative measurements,we found that the biosynthesis of EβF utilizes acetyl coenzyme A produced from fatty acid degradation,which can be suppressed by juvenile hormone but it is promoted by 20-hydroxyecdysone through the modulation of fatty acid metabolism.This is the first systemic study on the modulation of EβF production in aphids.The results of our study provide insights into the molecular regulatory mechanisms of AAP biosynthesis,as well as valuable information for designing potential aphid control strategies.

HTR-10燃料球和石墨球反应性当量测量实验

10MW高温气冷实验堆(HTR-10)是球床型反应堆,燃料元件的装卸和循环可不停堆,为了保证其安全运行,必须准确地知道燃料元件的装卸和循环过程可能引起的反应性变化,尤其是向堆芯装料时引入的反应性变化。HTR-10首次临界后对燃料球和石墨球的反应性价值进行了测量。本文介绍了燃料球和石墨球反应性当量刻度的方法,给出了初始装载堆芯和空气气氛下的燃料球和石墨球反应性当量实验测量结果。