场反构型无电极洛伦兹力推力器研究进展

场反构型洛伦兹力推力器利用旋转磁场驱动等离子体产生场反构型等离子体团(Filed Reversed Configuration-FRC),并利用洛伦兹力将其加速产生推力。由于该推力器不使用栅极加速,故不存在栅极溅射问题,大大延长推力器工作寿命。该技术借鉴自磁约束核聚变技术,推力密度大、功率扩展性好(MW级),在未来的深空探测和星际航行中具有广泛的应用前景。文章对场反构型洛伦兹力推力器发展现状进行了综述,并对工作原理、计算模型和技术瓶颈问题作了介绍,为中国等离子体推力器技术发展提供参考。

反场构型等离子体中Grad-Shafranov方程的数值解

基于反场构型(field-reversed configuration)渐近理论,编写了反场构型等离子体中二维Grad-Shafranov方程的数值模拟代码,研究了不同拉长形状的反场构型剖面.通过模拟,得到了磁面坐标系中反场构型等离子体压强及梯度分布,同时求解了大拉长比、不同分界面(separatrix)类型的磁通量分布.研究结果表明,等离子体压强梯度随着磁通量呈线性增长,在分界面处发生突变;分界面处的等离子体压强越高,分界面内部的压强会更高,即具有更高的等离子体β值,反映了反场构型较好的约束效果.

双模异构配电场域网多径并发传输动态决策算法

为提高配电场域网节点间的传输速率和连通率,构建了具有高速电力线宽带载波和微功率无线通信能力的混合多径双模异构配电场域网。首先论述了该场域网的拓扑结构、组网过程以及维护机制。其次设计了一种滑动窗口加权平均链路度量方法,采用改进的跳数受限Bellman-ford最短路径算法计算混合多径路由,并使用最近最多使用策略对各节点路由进行分散更新。在此基础上设计了一种自适应多径并发数据传输动态决策算法。最后将构建的该场域网应用到配电信息采集系统中,并在实验室和工程现场对其性能进行了测试。测试结果表明,该场域网比单模场域网在提高抄收率和缩短抄收时间方面效果明显。

配合物构型场理论的研究与应用

将配合物的价键理论和晶体场理论有机地结合在一起,提出了研究配合物结构的构型场理论,应用该理论能更好研究配合物的结构,更全面地解释预测配合物的光谱性、磁性、稳定性、空间构型及构型畸变等性质.

耦合有限体积法的Brown构型场并行算法

基于FENE珠-簧链分子模型,采用耦合有限体积法的Brown构型场并行算法,对压力驱动、速度-压力同向或反向驱动的管道流进行数值模拟.数值算例验证了算法的有效性,获得了相应速度、应力及分子链拉伸量的信息.数值结果表明:链段数的增加使得流动达到稳态所需时间缩短;该并行算法有效地克服了Brown构型场方法计算量大、耗时长的缺点;当珠子数大于2时,并行效率可达85%以上.

反场构型平面薄膜电爆炸等离子体电流通道

Z箍缩负载初始化电流通道的形成建立过程、电流密度分布模式及其演化特征对研究等离子体动力学发展、分析等离子体不稳定性模式、开展磁流体数值模拟工作等具有重要意义.平面薄膜是研究这一问题中具有连续二维结构的理想构型.基于理想无限长平板假设下的反场薄膜-回流柱负载模型,通过理论对电感主导模式下的电流通道建立和演化过程、薄膜平面磁场分布特征和薄膜各部分受力特征进行了计算分析.通过开展对称型与非对称型下的平面薄膜电爆炸实验,以可见光分幅相机记录薄膜等离子体自辐射光分布为主要诊断手段开展了实验验证.结果显示,早期电流的建立与分布符合电感模型预期,薄膜等离子体表现出电流密度边缘聚集和钳状型等离子体发光形态.中后期图像显示发光强区会由薄膜边界向中心位置转移并导致峰状凸起型等离子体发光形态的演化,表明电流分配受等离子体发展影响,边界融蚀等离子体向心汇聚导致电流随之转移,最终造成电流通道的快速切换.

基于Brown构型场的黏弹性流体数值模拟算法

基于黏弹性流体的微宏观耦合模型,提出一种求解Brown构型场方程的含双参数的预估校正数值方法,并通过突然起动的平板Couette流动验证所提出方法的有效性.数值结果表明,所提出的含双参数预估校正方法所得到构型场的应力演化的随机误差大幅度下降,应力场时间演化更加平稳.

农村社区组织系统建构的三维框架阐释

在转型农村社区组织系统的"结构—行动"互构性解释框架的视野下,系统结构和系统主体互动效果的体现,都是在具体情境场域空间进行展示的。农村社区组织场域系统制度、行动者和环境三要素互动的规则和秩序,在组织的社会行动和制度博弈的过程中逐渐产生结构化趋势的同时,具体可交易的场景也对社会互动与后果呈现出一定程度的制度性限制。这种彼此塑造的甚至矛盾化的发展过程,推进着农村社会机制创新和结构变迁,实现着农村社区组织系统的动态发展和路径演化。

基于神经网络的混杂SiC颗粒增强铝基复合材料力学性能预测

目的提高混杂SiC颗粒增强铝基复合材料的韧性,利用卷积神经网络预测其力学性能,以得到力学性能关键因素的影响规律。方法首先,通过实验得到了铝基复合材料的力学性能数据。其次,基于相场裂纹扩展本构,采用Python代码批量生成了不同构型参数的代表性体积单元,并利用Abaqus软件进行了有限元仿真(FEM)。通过代码实现了建模与仿真的一体化构建,利用得到的仿真数据,建立了神经网络模型,并实现了对复合材料力学性能的预测。建模前,对数据进行预处理和筛选,以提高数据质量并降低模型复杂度。最后,建立卷积神经网络,并优化模型的超参数。结果通过建立的神经网络模型,实现了对复合材料力学性能的有效预测。极限强度的预测误差保持在−7%~8.5%,能耗的预测误差保持在−5%~6%,预测精度较高。结论通过结合实验、仿真和卷积神经网络模型,可以更有效地预测混杂SiC颗粒增强铝基复合材料的力学性能,从而为材料设计和制备提供指导。

深空探测聚变推进装置技术路线与研究现状综述

聚变推进技术凭借其能量密度大和高比冲等显著优势,在深空探测研究中受到广泛关注。本文介绍了三种前沿聚变推进装置(反场构型感应驱动金属衬层压缩聚变推进探测器、梯度场内爆衬层聚变推进探测器和普林斯顿反场构型直接聚变驱动探测器)的研究进展,从聚变堆设计原理、深空探测任务参数与实验进展等角度,对三种技术路线进行了分析和总结。

小浪底水库诱发地震预测研究

通过实地考察并结合前人研究成果 ,对黄河小浪底水库及其邻区地质构造特征和地震活动性进行了分析 .认为该地区地质构造背景较为复杂 ,地震活动性相对较弱 .在此基础上 ,采用概率预测法对小浪底水库诱发地震的可能性进行了研究 .利用逻辑信息法和灰色聚类法对诱发地震的强度进行了预测 .结果表明 ,该水库存在诱发地震的可能性 ,最可能发生诱发地震的地段为库区中段 ,震级上限可达 5级 .

Measurement of wind field characteristics at a long-span suspension bridge

In order to provide a reliable basis for wind resistant evaluation of a long-span suspension bridge, a structural health monitoring system is installed on a bridge in the East China Sea and the simultaneous wind data at the bridge deck and at the top of the bridge tower are recorded. The average wind speeds and directions, variations of wind speeds with height, turbulent characteristics, spatial correlation and characteristics of wind flow around the bridge deck are analyzed by using statistical methods and spectral analysis. It is found that the average wind speeds along the bridge girder are almost identical; however, the mean wind directions vary greatly at different locations. The dimensionless exponent decreases as the average wind speed increases. The measured turbulence intensities are greater than the recommended values, and the turbulence power spectrum can well fit the standard spectrum. However, the measured spectral values are considerably smaller in low frequency ranges. The mean wind speed of the wake flow decreases and the turbulence intensity increases significantly, and the spectral characteristics of the wake flow change obviously while the feature frequency of vortex shedding has not yet been observed.

基于箍缩装置的高能量密度物理实验研究进展

基于脉冲功率技术的箍缩装置能够在cm空间尺度和百ns时间尺度产生极端的高温、高压、高密度以及强辐射环境。中物院流体物理研究所在已建成的10 MA级的大型箍缩装置上开展多种负载构型的高能量密度物理实验研究。利用Z箍缩动态黑腔创造出了惯性约束聚变研究所需的高温辐射场;研究了金属箔套筒和固体套筒的内爆动力学特性;利用中低Z材料内爆获得了可观的K壳层线辐射并用于X射线热-力学效应实验研究;磁驱动准等熵加载和冲击加载为材料动态特性研究提供了新的实验能力;采用环形二极管和反射三极管技术的轫致辐射源获得了高剂量(率)的X射线和γ射线;利用磁驱动的径向金属箔模拟了天体物理中恒星射流的形成及其辐射的产生。此外,还介绍了利用反场构型磁化靶聚变装置开展的预加热磁化等离子体靶形成等实验结果。

高功率等离子体电推进技术研究进展

高功率场反构型等离子体推力器具有高比冲、长寿命、大推力、高功率和高效率的特点,是未来深空探测任务最具竞争力的推进方案之一。针对国内外当前高功率电推力器的技术研究现状,分析了场反构型等离子体推力器的优势。结合场反构型等离子体电推力器的结构和工作原理,梳理了高功率场反构型等离子体的产生、等离子体约束和控制、地面测试设备等关键技术,从性能提升的角度分析了场反构型等离子体推力器的发展趋势,为我国高功率等离子体推力器技术研发提供参考。

On Structure,production,and market of bamboo-based panels in China

Since bamboo has the advantages of straight grain, beautiful color, high strength and toughness, and excellent abrasion resistance, bamboo-based panels have been widely used in the fields of vehicle, construction, ship building, furniture, and decoration to partly take the place of wood, steel, plastic etc in China. This paper briefly described the basic component units, including strip, sliver, and particle, of bamboo-based panel and pointed out that to design the structure of bamboo-based panels should follow the principle of symmetric structure, surface forming method, and structuring principle of equalizing stress. According to the processing methods and formation of component units, the authors classified the bamboo-based panels in China into 13 types and presented the manufacturing technique and uses of the bamboo products, such as plybamboo, bamboo flooring, and bamboo-wood composite products in detail. In the last part of the paper, much information were offered on the output, market, and selling prospect of each type of bamboo-based panels.

Decay rates and time lags of heat conduction in building construction under field conditions

The field measurements of decay rates and time lags of heat conduction in a building construction taken in Nanjing during the summer of 2001 are presented.The decay rates and time lags are calculated according to the frequency responses of the heat absorbed by the room＇s internal surfaces,inside surface temperature,indoor air temperature and outdoor synthetic temperature.The measured results match very well with the theoretical results of the zeroth and the first order values of the decay rates and time lags of heat conduction in the building construction,but the difference between the measured values and the theoretical values for the second order is too great to be accepted.It is therefore difficult to accurately test the second order value.However,it is still advisable to complete the analysis using the zeroth-and the first-orders values of the decay rates and time lags of heat conduction in building construction under field conditions,because in these cases the decay rates of heat conduction reach twenty which meets the requirements of engineering plans.

Comparable study on typhoon and strong northern wind characteristics of the Runyang Suspension Bridge based on field tests

The strong wind characteristics of the Runyang Suspension Bridge（ RSB） including the wind speed and direction, the turbulence intensity, the turbulence integral length and power spectrum are analyzed based on measurement data from the wind environment monitoring subsystem of the structural health monitoring system （SHMS）of the RSB and field tests during strong winds. The differences between the typhoon and the strong northern wind are especially studied. It is found that the mean wind speed of the strong northern wind is a little smaller and the mean wind direction is more stable than that of the typhoon. The turbulence intensity of both the typhoon and the strong northern wind is greater than the values suggested in Chinese code, and the turbulence integral length difference between the typhoon and a strong northern wind is not clear. As for the along-wind turbulence power spectrum, the spectrum of the strong northern wind can fit the Kaimal spectrum better than that of the typhoon. The obtained results can provide measurement data for founding a strong wind characteristic database and determining the strong wind characteristic parameter values of the RSB.

Measurement and theoretical analysis of solar temperature field in steel-concrete composite girder

The solar temperature field of a large three-span continuous bridge with steel-concrete composite box girder and variable cross-section is measured to verify a calculation method for the temperature field of steel-concrete composite beams. The test results show that the temperature of an external steel web- plate is higher than that of an internal web-plate due to the difference in solar radiation. Air temperature inside the box matches the average temperature of the whole steel box. Based on actual measurements, a transient thermal analysis with multiple boundary conditions is also carried out by a software program ANSYS. Convective boundary situation and states of solar radiation on steel web plates in different situations are determined in the analysis. The feature of the temperature field is preliminarily achieved through a comparative study between the actual measurement and the finite element analysis. The computed results are in good consistence with the actual measurement results, with the maximum difference within 2 ℃. This indicates that the theoretical calculation method is reliable and it provides a foundation for further research on temperature field distribution in the steel-concrete composite box girder.

Static Induction Devices with Planar Type Buried Gate

Based on the surface-gate and buried-gate structures,a novel buried-gate structure called the planar type buried-gate (PTBG) structure for static induction devices (SIDs) is proposed.An approach to realize a buried-gate type static induction transistor by conventional planar process technology is presented.Using this structure,it is successfully avoided the second epitaxy with a high degree of difficulty and the complicated mesa process in conventional buried gate.The experimental results demonstrate that this structure is desirable for application in power SIDs.Its advantages are high breakdown voltage and blocking gain.

Phase-field study on competition precipitation process of Ni-Al-V alloy

With microscopic phase-field kinetic model, atomic-scale computer simulation program for the precipitation sequence and microstructure evolution of the ordered intermetallic compound γ＇ and θ in ternary Ni75AlxV25-x alloy were studied. The simulation results show that Al concentration has important effects on the precipitation sequence. When Al concentration in Ni75AlxV25-x alloy is low, 0（Ni3V） ordered phase will be firstly precipitated, followed by γ＇（Ni3Al） ordered phase. With Al concentration increasing, θ and γ＇ ordered phases are simultaneously precipitated. With A1 concentration further increasing, γ＇ ordered phase is firstly precipitated, followed by θ ordered phase. There is a competition relationship between θ and γ＇ ordered phases during growth and coarsening process. No matter which first precipitates, θ ordered phase always occupies advantage in the competition process of coarsening, thus, the microstructure with preferred orientation is formed.