Optimum parameter matching obtained by experiments for coring drilling into lunar simulant

This paper performs a series of ground experiments (on the Earth) to obtain optimum parameter matching for a future core drill on the Moon. Three common stages, I, II, III, are recognized with respect to the cut per revolution (CPR), which is defined as the ratio between the feeding speed and the rotating speed. The optimum matching between the feeding speed and the rotating speed for drills locates at the boundary position between Stage II and Stage III, where the coring rate saturates and the weight on the bit and the driving torque are still low. Further data analysis of the ground experiments reveals that the optimum matching signifies a proportional relation between the maximum conveying rate (MCR) by the groove of the auger and its rotating speed. The kinetic analysis in an ideal condition without gravity, the friction from the auger groove and the pressure at the bit confirm a similar proportion. The correlation between the proportions needs further study to determine whether the optimum matching obtained on the ground can be directly applied to future drills on the Moon.     

浅议我国个人所得税实施中存在的问题及解决对策

个人所得税在调节个人收入、增加财政收入、维护国家权益等方面发挥了积极作用,但是随着我国经济的发展,在实施个人所得税中也逐渐暴露出一些问题.本文针对这些问题,进行了深刻的分析,并提出了解决的对策.     

嵌金属丝推进剂燃烧起始阶段增速特性研究

考虑了使用嵌金属丝装药的发动机工作过程中的多种因素,建立了金属丝与药柱、燃气间相互作用的控制方程组,并对方程组进行了数值求解,得到了嵌金属丝推进剂在燃烧起始阶段,增速比随时间的详细变化过程。结果表明,金属丝的热扩散率、熔点、直径和黑度以各自不同的方式影响金属丝的增速效果,熔点相对较低的金属丝可能会在内弹道曲线的初始阶段形成一个轻微的压强峰,固有燃速较低、着火温度较低的推进剂对嵌入金属丝较为敏感。文中数值方法计算量小,结果可靠,适于工程应用。     

基于数值模拟的超塑成形压力—时间曲线计算机辅助设计

确定压力随时间变化的关系曲线对于超塑成形工艺设计非常重要，本文在超塑成形压力计算时引入能量消耗控制策略，提出了一种压力－时间（Ｐ－Ｔ）曲线设计方法即恒能耗率法，实现了基于有际元数值模拟的超塑成形Ｐ－Ｔ曲线计算机辅助设计，文中对有关的压力控制算法及算式进行了较详细的介绍和推导，分别给出了半球壳自由胀形和圆筒形凹模约束成形过程的Ｐ－Ｔ曲线设计计算实例，并对计算结果进行了讨论，本文的研究拓宽了刚粘塑性有     

一类基于四面体组合单元的模块化构架式可展开天线机构

针对现有基于四面体单元的构架式天线机构结构复杂、收拢率低、运动副数量多等问题，基于3RR-3RRR四面体组合单元和基于3RR-3URU四面体对称组合单元分别提出了两种新型模块化可展结构。以3个组合单元组成的模块化结构为分析对象，首先，详细介绍了模块化结构的组成及虎克铰轴线布置，并利用组合单元本身的自由度数目及性质，采用拆杆-等效-复原的思想，应用螺旋理论和G-K公式分别对提出的两种模块化结构进行了自由度分析，得到了自由度数目及性质。其次，应用Adams动力学仿真软件对两种模块化结构进行运动仿真，仿真结果验证了自由度分析的正确性。以完全展开和完全收拢时机构所占的空间体积比值表征该机构的收拢率，计算现有基于四面体单元的非模块化机构与提出的模块化机构的收拢率。最后，对比分析非模块化机构与模块化机构的自由度数目、运动副数目及收拢率。分析结果表明，基于3RR-3URU四面体对称组合单元的模块化结构既能实现较大收拢率，自由度及运动副数目也相对减少，且组成大型天线时杆件类型较少。研究结果为该类模块化构架式可展天线结构的设计与分析提供一定理论依据。     

The evolution of mirror type magnetic fluctuations in the magnetosheath based on multipoint observations

Two orbits were selected in January–February 2006 when the separation between the Cluster spacecraft was large and mirror type magnetic field fluctuations were observed by all spacecraft in different regions of the terrestrial magnetosheath. Minimum variance analysis was applied to find the mirror type fluctuations, and the amplitude of the fluctuations was determined individually. Mirror mode structures are moving along the streamlines frozen in the plasma. A model was developed for the calculation of plasma flowtime from the bow shock to the observation point. The growth rate of the field strength perturbations was estimated by comparing the amplitudes of fluctuations observed simultaneously at distant locations (∼10,000 km) based on the assumption that δB ∼ exp(γt). The obtained growth rate values were about an order of magnitude smaller than those provided by linear models and they decreased in the inner regions of the magnetosheath, indicating some saturation in the growth of the waves when proceeding towards the magnetopause. The results of these two case studies suggest that mirror type fluctuations originate from the compression region downstream of the quasi-perpendicular bow shock, and the growth of the fluctuations cannot be described by linear approximations.     

极高真空技术的发展

总结了极高真空（XHV低于10^-9Pa的压力范围）获得和测量方法以及获得和测量极高真空的限制因素，描述了降低XHV系统器壁和元件（包括真空规或残余气体分析器）出气率采用的技术。     

高应变率下的玻璃钢力学性能的实验研究

利用分离式Ｈｏｐｋｉｎｓｏｎ压杆研究了国产环氧玻璃钢和聚脂玻璃钢在平均应变率约为１０＾３ｓ＾－１下的动态力学性能，给出这两种材料在冲击压缩下的弹性模量和能量吸收率，为新型飞行保护头盔的设计提供了材料的实验依据。     

A closed-form solution for moving source localization using LBI changing rate of phase difference only

Due to the deficiencies in the conventional multiple-receiver localization systems based on direction of arrival(DOA) such as system complexity of interferometer or array and amplitude/phase unbalance between multiple receiving channels and constraint on antenna configuration,a new radiated source localization method using the changing rate of phase difference(CRPD)measured by a long baseline interferometer(LBI) only is studied. To solve the strictly nonlinear problem, a two-stage closed-form solution is proposed. In the first stage, the DOA and its changing rate are estimated from the CRPD of each observer by the pseudolinear least square(PLS) method,and then in the second stage, the source position and velocity are found by another PLS minimization. The bias of the algorithm caused by the correlation between the measurement matrix and the noise in the second stage is analyzed. To reduce this bias, an instrumental variable(IV) method is derived. A weighted IV estimator is given in order to reduce the estimation variance. The proposed method does not need any initial guess and the computation is small. The Cramer–Rao lower bound(CRLB) and mean square error(MSE) are also analyzed. Simulation results show that the proposed method can be close to the CRLB with moderate Gaussian measurement noise.     

Transient simulation of regression rate on thrust regulation process in hybrid rocket motor

The main goal of this paper is to study the characteristics of regression rate of solid grain during thrust regulation process. For this purpose, an unsteady numerical model of regression rate is established. Gas–solid coupling is considered between the solid grain surface and combustion gas.Dynamic mesh is used to simulate the regression process of the solid fuel surface. Based on this model, numerical simulations on a H2O2/HTPB(hydroxyl-terminated polybutadiene) hybrid motor have been performed in the flow control process. The simulation results show that under the step change of the oxidizer mass flow rate condition, the regression rate cannot reach a stable value instantly because the flow field requires a short time period to adjust. The regression rate increases with the linear gain of oxidizer mass flow rate, and has a higher slope than the relative inlet function of oxidizer flow rate. A shorter regulation time can cause a higher regression rate during regulation process. The results also show that transient calculation can better simulate the instantaneous regression rate in the operation process.