基于矢量网络分析仪的相对介电常数扫频测量

采用波导短路法对介质材料的相对介电常数进行扫频自动测量,通过VC＋＋开发了一套宽频带（8GHz~18GHz）复介电常数自动测量系统。用矢量网络分析仪对波导采样器进行扫频测量,不仅可以得到被测材料介电常数的频率特性,而且能够解决超越方程多值解的判断问题,并减少了测量中的误差。通过对介质样品的实际测量,可以发现,该自动测量系统操作简单、测量速度快,测量结果能够达到较高准确度,结果令人满意。     

利用六端口反射计测量介质材料的ε_r 和μ_r

文章介绍了利用六端口反射计自动测量微波材料的复介电常数ε,和复导磁率μ(?)的原理、测量方法,给出了一些材料样品的测试结果。     

Ku波段波导扫频双六端口网络分析仪

介绍研制的一种实用Ku波段扫频双六端口网络分析仪。该仪器能同时测量双口网络的4个散射参数及单口网络的复反射系数。     

利用六端口反射计测量复介电常数的研究

本文从测量复介电常数的基本原理出发,简单分析了开口同轴线直接同被测平面介质接触时的等效电路,利用保角变换的方法计算等设电容 C_(?)们 C_(?),从而提出了一种利用六端口反射计开口测量复介电常数的新方法。     

HP8409C自动网络分析仪在雷达截面测量中的应用

进行雷达截面(RCS)测量时,主要问题是需要消除测量数据中非期望信号的影响.为此,提出了一种使用 HP8409C 自动网络分析仪测量目标 RCS 的方法,介绍了测试系统的设置和工作原理,以及借助仪器校准功能和所扩展的时域能力完成非期望信号的消除处理.说明 RCS非暗室测量的可行性,简述了 HP8409C 的扫频测量、校准步骤以及外场测试的结果。     

一种新的动态压力校准装置

介绍了最新研制的动态压力传感器频率特性连续校准装置.该装置既可作为正弦压力校准装置使用,也可作为扫频测量装置对压力传感器进行扫频测量,直接获得压力传感器的幅频特性和相频特性曲线,从而达到对动态压力传感器频率特性连续校准的目的.装置单频测量压力幅值比与扫频测量压力幅值比的误差低于±1％,相位误差低于±0.5°.装置的扫频频率范围为(0.1～10 000)Hz,工作压力范围为(0.25～10)MPa.     

汉语自动分词知识

汉语分词是汉语言计算机处理的一项不可缺少的工作。使用自动分词知识可以进一步提高自动切分精度,满足高标准的需求。本文在[1][2][3]的研究基础上,介绍了一些行之有效的自动分词知识。根据对4(?)092个汉字的语言材料统计结果表明(统计材料分社会科学和自然科学两部分),这些自动分词知识可以处理90％左右的多义切分字段。     

谐振腔法复介电常数测量系统的谐振频率标定

微波介质材料的复介电常数,或称相对介电常数和介质损耗角正切参数是表征其介电特性的最重要的物理参数。目前对于微波介质材料普遍采用谐振法进行测试,但仍然存在测试频率不够高、测量结果一致性不理想等诸多问题。本文以本单位自行研制的基于分离圆柱体谐振腔法的材料复介电常数测量夹具所建立的微波复介电常数测量系统为研究对象,通过实验的方法,对该测量系统的TE_(011)的谐振频率这一关键指标的最优测试条件、标定方法和结果、稳定性等进行了系统地研究,实验结果表明,该谐振腔法测量系统非常适合作为计量标准装置,用于微波介质材料标准样片的复介电常数的计量和校准。     

激光雷达复材型面测量精度分析方法

针对激光雷达复材型面测量时测量精度的评定需求，提出了一种基于激光雷达回波信号信噪比（SNR）的精度分析方法。通过对复材型面检测结果进行评价，获取零件脱模后准确的变形量结果，有利于实现精准修模。所提方法考虑了测量工程中待测距离、入射角、材料属性等因素对测量结果产生的影响，研究激光雷达型面测量过程中回波信号信噪比与测量精度的联系，利用信噪比的变化规律，结合仪器不确定度，确定测量点云不同区域的精度修正因子，实现激光雷达大尺寸复材型面变形量检测结果的测量精度分析，减小了测量误差对变形量的影响。所提方法能准确评价测量结果的精度，获取复材型面的真实变形量。      

X波段波导自动测量线系统

本文叙述一个用传统的开槽测量线配以Apple-Ⅱ微机构成的波导自动测量系统,其核心部分是可程控测量线和可程控短路活塞。由于传统测量线有性能稳定可靠、价格低廉的优点,现加上计算机高速计算和自动控制的功能,就实现了一种新颖的价廉物美的微波自动测量系统。它由不十分复杂的硬件配以合适的软件支持,可以使测量精度优于手动测量线,测量速度大大提高。本文还讨论了扩展动态范围、提高测量精度的方法,提出了解决宽带测量的方法。本文中还给出了测波源驻波系数、双口网络复S参数和无耗双口网络端面小反射等三个应用实例。     

Stochastic particle acceleration by the forced interaction of relativistic current sheets

We address the problem of interacting relativistic current sheets in self-consistent kinetic plasma simulations within the framework of the Particle-In-Cell model. The interaction is enforced in head-on collisions of up to 10 current sheets at relativistic bulk speeds. The simulations are motivated by the general problem of Poynting flux dissipation in ‘striped wind’ configurations presumably governing the relativistic outflows pervasive in pulsar winds and gamma-ray bursts. We identify the generation of non-thermal particles and formation of a stable power-law shape in the particle energy distributions f(γ) dγ ∝ γ^−s dγ. In 1D, a spectral index s ∼ 2 is observed and attributed to a stochastic Fermi-type acceleration mechanism. In 2D, the generic index of s ∼ 3–4 is retained as in previous simulations of individual current sheets. Whereas in 2D the high energy cut-off is constrained by the limited dissipation of magnetic energy, in 1D the process converts the bulk motion of current sheets towards directed particle momentum of an exclusive class of non-thermal particles.     

Concept options for the aerial survey of Titan

Various aerial platforms intended for long endurance survey of the Titan surface are presented. A few novel concepts are introduced, including a heated methane balloon and a balloon with a tethered wind turbine. All the concept options are predicted to have lower scientific payload fractions than the Huygens probe. It is concluded that the selection of the best aerial platform option depends on more accurate mass estimates and a clear decision on whether, or not, in situ surface composition measurements are required in conjunction with aerial remote sensing.     

Heterogeneous solid/gas chemistry of organic compounds related to comets,meteorites, Titan,and Mars: Laboratory and in lower Earth orbit experiments

To understand the evolution of organic molecules involved in extraterrestrial environments and with exobiological implications, many experimental programs in the laboratory are devoted to photochemical studies in the gaseous phase as well as in the solid state. The validity of such studies and their applications to extraterrestrial environments can be questioned as long as experiments conducted in space conditions, with the full solar spectrum, especially in the short wavelength domain, have not been implemented. The experiments that are described here will be carried out on a FOTON capsule, using the BIOPAN facility, and on the International Space Station, using the EXPOSE facility. Vented and sealed exposition cells will be used, which will allow us to study the chemical evolution in the gaseous phase as well as heterogeneous processes, such as the degradation of solid compounds and the release of gaseous fragments.     

基于LuGre模型的电液加载系统摩擦补偿

为了提高电液加载系统控制精度,针对摩擦问题提出了基于LuGre摩擦模型的前馈补偿方法.建立了用于摩擦仿真分析和补偿器设计的电液加载系统数学模型;通过实验获取并分析了相关的摩擦数据;基于实验数据进行LuGre模型参数辨识,把LuGre模型和辨识结果引入电液加载系统数学模型,并进行仿真结果与实际摩擦数据的对照,证明了LuGre摩擦模型的准确性.设计前馈补偿器,进行了实验对比,实验结果表明前馈补偿器可将摩擦产生的控制误差有效地降至未补偿时的30%左右.      

CoRoT and Kepler results: Solar-like oscillators

The space-borne observatories CoRoT (Convection Rotation and planetary Transits) and Kepler have provided photometric time series data of unprecedented precision for large numbers of stars. These data have revolutionized the fields of transiting exoplanets and asteroseismology. In this review some important asteroseismic results obtained using data from the CoRoT and Kepler space missions concerning stars that show solar-like oscillations are discussed. These results comprise, among others, measurements of the location of the base of the convection zone and helium second-ionization zone in main-sequence stars, the presence (or not) of core-helium burning in red-giant stars, as well as differential rotation in these stars.     

The ESA scientific programme

The ESA scientific programme has, so far, provided several significant astrophysics experiments and further important missions are scheduled for execution during the next decade. These missions are briefly summarised together with several astrophysics investigations presently under study.     

HELIO: The Heliophysics Integrated Observatory

Heliophysics is a new research field that explores the Sun–Solar System Connection; it requires the joint exploitation of solar, heliospheric, magnetospheric and ionospheric observations.     

Radioactivity of the Moon and planets

In this report the main results of the study of radioactivity of the solar sistem bodies are considered. The radioactivity of the Moon and planets was measured by means of vehicles in situ. The radioactivity of the lunar samples, brought to the Earth was studied with laboratory equipment.     

一种提高螺栓联接强度的新方法

根据山本晃教授对螺栓，螺母，螺纹牙受力及其变形研究的成果，导出了该理论条件下受拉螺栓在等载荷受力状态下，当螺栓螺纹采用标准尺寸，螺母螺纹的螺旋线形状，并依据实用性，从螺母螺纹加工方便考虑，提出了近似等负荷螺纹。     

直尺反转组合法测量直线度的理论分析

对直尺反转组合法的测量原理进行了较为深入的理论分析，指出测量的准确性受测头误差、采样点定位误差、直尺尺面斜率、直尺再定位误差、直尺各点直线度误差的变化率等五个方面共同作用。其中，采样点定位误差和直尺安装斜率影响直线度测量准确度这一结论，将适用于其他的直尺直线度测量方法，因而具有普遍的指导意义。