同位素氢化钾中含氚量的气压测量法研究

根据氚的衰变特性和同位素氢化锂的贮存条件,利用贮存容器的气压变化量,气体温度和贮存时间等参数,设计了一种新的测量其含氚量的气压测量法。此方法无需特殊的测量系统,测量一次只需几分钟,速度比原来的“量热法”提高了几百倍,具有显的社会,经济效益。     

同位素氢化锂中含氚量的气压测量法研究

根据氚的衰变特性和同位素氢化锂的贮存条件,利用贮存容器的气压变化量、气体温度和贮存时间等参数,设计了一种新的测量其含氚量的气压测量法.此方法无需特殊的测量系统,测量一次只需几分钟,速度比原来的量热法提高了几百倍,具有显著的社会、经济效益.     

LaNi4.25A10.75床氚滞留量的测量

分别采用直接测量法、同位素交换法和溶解法测量LaNi4.25A10.75床中的氚滞留量，并分析了这3种测量方法在本实验条件下的误差。直接测量法测量LaNi4.25A10.75床的氚滞留量的结果如下：LaNi4.25A10.75床的氚滞留量为3．65％（（0．097±0．00092）mmol T2／g LaNi4.25A10.75），当压力读数在1．5-133.332kPa之间时，其PVT测量法的标准差小于0．95％；同位素交换法测量LaNi4.25A10.75床氚的结果如下：加热充分解吸过的LaNi4.25A10.75床经多次同位素交换后，其交换效率仅为1．92％，即不到2％的氚被氘气载带出来，其同位素交换法测量的标准差为7．35％。溶解法能够定量地测量LaNi4.25A10.75床中滞留的氚，其溶解法测量的标准差为6．49％。     

液态锂铅与阻氚涂层材料相容性的研究进展

在聚变堆液态锂铅包层设计中,结构材料表面需覆盖一层阻氚涂层。涂层一般需要兼顾两方面功能：(1)高阻氢渗透因子,能够稳定地抑制氢渗透以维持反应堆的氚安全;(2)较高的耐腐蚀性能,以保证结构材料的结构完整性及热力学性能稳定性。阻氚涂层与锂铅直接接触会发生腐蚀,产生缺陷(如腐蚀坑等),影响涂层结构稳定性和阻氢渗透效率,进而直接影响涂层的服役寿命。本文重点综述了液态锂铅与阻氚涂层的相容性以及液态锂铅腐蚀对阻氚涂层阻氢性能影响的相关研究进展。已有的研究显示,Cr₂O₃-Er₂O₃-ZrO₂涂层、铝基涂层等在静止液态锂铅环境中均展现了良好的相容性和稳定的阻氢性能。本文还指出了目前相关研究存在的共性问题及未来可能的研究发展趋势。相关领域还需进行更为全面、系统的研究,为未来聚变增殖包层中阻氚涂层的服役寿命评估提供支撑。     

对于风电预测数学模型的研究

风电厂发电功率的调整对于电力系统稳定运行具有十分重要的意义。而如何对风电场的发电功率进行尽可能准确地预测,是急需解决的问题。本文通过对多种预测模型进行研究,以较好地实现风电功率的短期预测。     

氢化锂薄膜的应用研究

阐述了氢化锂薄膜在惯性约束聚变中的应用背景,介绍了多层膜间隔层和惯性约束聚变中靶丸燃料的研究现状及存在的问题,展望了利用脉冲激光沉积技术制备氢化锂薄膜用作多层膜间隔层和靶丸燃料的发展方向。     

铝锂合金合金中氢含量的测定

本文在条件试验的基础上研究建立了铝锂合金中痕量氢的分析方法,样品分析结果表明,本方法简便、快速、准确、可靠.     

铝锂合金中痕量钾、钠的测定

本文采用原子吸收光谱法研究建立了铝锂合金中0.0005%～0.01%钾、钠的分析方法,该方法是在深入研究铝锂合金环境下钾、钠的分析行为基础上建立的,包括测量过程中基体及共存元素的干扰、电离干扰、酸介质的影响、降低空白、测量条件的选择等.实际样品的分析结果表明,该方法快速、准确、可行.方法的检出限为K:0.0045μg/ml,Na:0.0044μg/ml.     

水泥质量控制的数学模型

通过数理统计分析,可以揭示水泥质量的变化规律,发现其运动趋势,从而提高水泥质量控制的预见性和可控制性。     

靶丸材料及氘氚冰层分布对冷冻靶温度场的影响

冷冻靶靶丸氘氚(DT)内冰层均匀性直接影响到惯性约束聚变(ICF)点火成功率,衡量冰层均匀性的重要指标为靶丸表面温度均匀性。本文利用CFD软件对球腔内的温度场与速度场变化进行模拟,包括恒定冷臂温度下的稳态工况和非稳态降温过程,研究了不同烧蚀层材料以及冰层形貌下的冷冻靶丸传热特性和温度场分布。结果表明,高导热性烧蚀层材料对于提高冷冻靶温度场均匀性具有积极作用,当材料的导热系数高于400 W/(m·K)时,该球形冷冻靶靶丸外表面温差已小于0. 01 m K。在非稳态降温过程中,比热容和导热系数大的高密度碳(HDC)材料的靶丸外壁面温差比碳氢聚合物靶(CH)靶丸约减少81%。     

Numerical Modeling of Growth Kinetics of Pro-eutectoid Ferrite Transformed from Austenite in Fe-C-Σ X Alloys

In the present paper, a numerical modeling was developed to simulate the growth kinetics of ferrite transformed from austenite in Fe-C-∑X (X denotes substitution elements, such as Mn, Ni, Cr etc.) steels by solving the diffusion equation using finite difference method (FDM). Coupled with the kinetic modeling, thermodynamic calculations were carried out to determine the γ/α phase equilibrium conditions using a para-equilibrium (PE) model. The dissipation of free energy for γ→α phase transformation due to the so-called solute drag effect (SDE) was taken into account in the thermodynamic modeling. With this modeling, simulations on the growth kinetics of ferrite in the steels containing austenite-stabilizing and ferrite-stabilizing elements (such as Ni, Mn and Si, Cr, respectively) were performed, which indicates that it deviates from the parabolic growth rate law after the initial stage of transformation. The results were compared with the experimental values given by Bradley and Aaronson, showing that this model has a reasonably good accuracy to predict the growth kinetics of ferrite.     

A mixed-Weibull regression model for the analysis of automotive warranty data

This paper presents a case study regarding the reliability analysis of some automotive components based on field failure warranty data. The components exhibit two different failure modes, namely early and wearout failures, and are mounted on different vehicles, which differ among themselves for car model and engine type, thus involving different operating conditions. Hence, the failure time of each component is a random variable with a bimodal pdf which also depends upon a vector of covariates that indexes the specific operating condition. Then, a mixed-Weibull distribution, where the pdf of each subpopulation (namely the ‘weak’ and ‘strong’ subpopulation) depends on the covariates through the scale parameter, is used to analyze the component lifetime. A Fortran algorithm for the maximum likelihood estimation of model parameters has been implemented and a stepwise procedure, in its backwards version, has been used to test the significance of covariates and to construct the regression model. The presence of a weak subpopulation has been verified and the fraction of weak units in the population has also been estimated. Finally, the adequacy of the proposed model to fit the observed data has been assessed.     

Minimum Distance Estimation for the Generalized Pareto Distribution

The generalized Pareto distribution (GPD) is widely used for extreme values over a threshold. Most existing methods for parameter estimation either perform unsatisfactorily when the shape parameter k is larger than 0.5, or they suffer from heavy computation as the sample size increases. In view of the fact that k > 0.5 is occasionally seen in numerous applications, including two illustrative examples used in this study, we remedy the deficiencies of existing methods by proposing two new estimators for the GPD parameters. The new estimators are inspired by the minimum distance estimation and the M-estimation in the linear regression. Through comprehensive simulation, the estimators are shown to perform well for all values of k under small and moderate sample sizes. They are comparable to the existing methods for k < 0.5 while perform much better for k > 0.5.     

Fabrication and lithium intercalation properties of epitaxial Li2RuO3 thin films

Lithium intercalation in a lithium excess layered material Li₂RuO₃ was investigated using two-dimensional model electrodes with a restricted reaction plane of (002). Li₂RuO₃ films were synthesized on Al₂O₃(0001) substrate by a pulsed laser deposition, and X-ray diffraction measurements confirmed epitaxial growth of Li₂RuO₃(002). Electrochemical characterization using cyclic voltammetry and charge/discharge measurements indicated electrochemical reactions with a discharge capacity of 200 mAh g^− 1 for the film deposited at 400 °C followed by post-annealing at 550 °C. The electrochemical activity on the (002) plane indicated three-dimensional lithium diffusion in the two-dimensional layered rocksalt structure through the lithium sites in the transition metal layer.     

低温热色谱分离氢同位素

叙述了用“６０１”碳分子筛作托卡马克废气排出气的收集、纯化和低温热色谱的进样单元，以５Ａ分子筛柱在液氮（ＬＮ２）温度下吸附氕、氘，氚，随后把柱温回升至室温（２０℃～３０℃），为了提高分离效率、缩短分离时间和分离柱总长度，在两根分离柱间添加了ＨＤ、ＨＴ等歧化平衡器，经过四根分离柱组成的级联分离柱后氕、氘、氚获得了清晰分离。该装置的单次进样量为５标准升，日处理量为１２０～１８０标准升，流程气体总回收率＞９７％，氘丰度＞９９．９％时，氘、氚损失量（不计加热３００℃活化再生分离柱回收的氘、氚）＜５％，除氕效率＞９８％。     

The vacuum systems of ITER

ITER is a large vacuum facility which comprises many service, diagnostic and monitoring vacuum sub-systems as well as three large cryogenic pumping systems for evacuation and maintenance of the requested pressure levels. The presence of hydrogen (including the radioactive isotope tritium) and exclusion of other gases defines the parameters of fusion vacuum systems. This paper will focus on the areas of the ITER vacuum systems which require customized developments and cannot rely on commercial solutions. The complex pumps have been tailored for the very specific applications and requirements at ITER, characterized by high magnetic and radiation fields, excellent availability and maintainability and, especially, the need to be tritium-compatible. An outline of the development path which was needed to come up with a sound design for the ITER cryopumps is given and the status of the programme in view of the imminent manufacturing phase is described in this paper.     

Numerical modeling of self-pressurization and pressure control by a thermodynamic vent system in a cryogenic tank

This paper presents a numerical model of a system-level test bed—the multipurpose hydrogen test bed (MHTB) using the Generalized Fluid System Simulation Program (GFSSP). MHTB is representative in size and shape of a space transportation vehicle liquid hydrogen propellant tank, and ground-based testing was performed at NASA Marshall Space Flight Center (MSFC) to generate data for cryogenic storage. GFSSP is a finite volume-based network flow analysis software developed at MSFC and used for thermofluid analysis of propulsion systems. GFSSP has been used to model the self-pressurization and ullage pressure control by the Thermodynamic Vent System (TVS). A TVS typically includes a Joule–Thompson (J–T) expansion device, a two-phase heat exchanger (HEX), and a mixing pump and liquid injector to extract thermal energy from the tank without significant loss of liquid propellant. For the MHTB tank, the HEX and liquid injector are combined into a vertical spray bar assembly. Two GFSSP models (Self-Pressurization and TVS) were separately developed and tested and then integrated to simulate the entire system. The Self-Pressurization model consists of multiple ullage nodes, a propellant node, and solid nodes; it computes the heat transfer through multilayer insulation blankets and calculates heat and mass transfer between the ullage and liquid propellant and the ullage and tank wall. A TVS model calculates the flow through a J–T valve, HEX, and spray and vent systems. Two models are integrated by exchanging data through User Subroutines of both models. Results of the integrated models have been compared with MHTB test data at a 50% fill level. Satisfactory comparison was observed between tests and numerical predictions.     

翅片式蒸发器换热性能的数学模型

本文采用分布参数法对翅片式蒸发器建立了数学模型，通过计算局部换热系数和摩擦压降来简化翅片式蒸发器内复杂的三维流动关系，总结了文献已有的换热系数和摩擦压降的关联式，并添加到模型控制方程中，基于此模型，可对制冷剂在翅片式蒸发器中应用的换热性能进行模拟研究。     

R&D and design for the cryogenic and mechanical vacuum pumping systems of ITER

The next generation thermonuclear fusion machine ITER comprises large cryogenic pumping systems to process very high gas throughputs. The paper starts from a summary of the requirements for the torus exhaust pumping system and the neutral beam injection system for plasma heating and discusses the design solutions derived to match them. All ITER force-cooled cryopumps are based on a modular set-up and incorporate similar design of charcoal-coated cryopanels cooled to 4.5 K with supercritical helium. A systematic approach for how to design a tailor-made cryopump is presented. It is based on Monte Carlo simulation to calculate the overall capture coefficient being the primary design parameter. Experimental results measured with a model pump of representative scale are used to validate the design procedure. In the last part, the paper addresses the design issues to be solved for tritium-compatible forepumps with high pumping speeds.     

超精密车削表面粗糙度预测模型的建立

介绍了一种利用回归分析法来建立单点金刚石刀具超精车削表面粗糙度预测模型的新方法,并通过建立的粗糙度预测模型,研究了铝合金超精密车削过程中切削速度,进给量和切削深度等参数对表面粗糙度的影响。通过实验分析表明：二次预测方程比一次预测方程更有效,而且适用范围比一次模型大。利用优化设计中的约束变尺度法对所建立的表面粗糙度预测方程进行了优化,可以实现对切削参数的优选,从而达到加工前在特定的条件下预测和控制表