航天器对接相对位置姿态自主测量方法研究

航天器间相对位置姿态的准确测量是实现自主自动对接的先决条件。将三圆标志靶安装在目标航天器上;追踪航天器用数码相机对靶拍照。设计了亚像素处理方法实时处理数字照片,可精确测定圆心像点位置和特征直径的像长;用其作为基本特征参数,基于透视投影原理,建立了求圆心物空间坐标的公式,求出靶面的平面方程,可用来求两航天器间的相对位置姿态参数和实时标定相机的可变参数。计算机仿真结果表明,测距为2m时,测圆心像点位置的误差小于0.03个像素,测距误差小于1mm,测姿态角的误差小于0.01°。该方法也适用于无人直升飞机定点着陆时自主测量其相对位姿参数。     

基于孔口出流模型的实验研究及理论分析

基于孔口出流模型对底部有小孔的圆柱体容器中液体液面高度随时间的变化规律进行了实验研究,并通过计入液体表面张力引起的孔口收缩和流体黏滞力导致的能量损失对实验结果进行了理论分析,与实验结果一致.     

气粒混合物非灰辐射特性合并宽窄谱带K分布模型

气粒混合物辐射问题具有全场性、非灰性、耦合性等特点,准确预估高温燃气/粒子非灰辐射特性是非常重要的。本文将合并宽窄谱带K分布模础(CWNBCK)与离散坐标法(DOM)结合,开展了非灰气粒混合物辐射换热问题的模拟工作,分别验证了一维和三维情况下应用该模型的准确性,给出不同工况下的热流源项、壁面热流或辐射热流等。结果表明:该模型能够给出与SNB模型精度基本相同的结果,考虑其计算效率的提高,可以在工程实际中应用该模型计算非灰气粒混合物辐射换热。     

Brightness Temperature Emitted by Radiometer Calibration Load at Millimeter Wave Band

In this paper, the DVRT (vector radiative transfer theory of densely distributed random discrete scatters) model to calculate the brightness temperature emitted by radiometer calibration load is presented. It takes the multiple scattering of isolation layer into account, which is neglected by the incoherent homogeneous model often used in calibration. Hence, it works much better than incoherent homogeneous model at millimeter wave band. Furthermore, the iteration of DVRT model is presented, and it proves that the incoherent homogeneous model is just the zero-order solution of DVRT model. Some numerical results are provided in the end.     

Like‐Charge Attraction: A Combined Electrostatic–Hydrodynamic Approach

Abstract

This article discusses the like‐charge attraction of colloidal spheres close to a charged plate and compares results produced by an electrostatic and a hydrodynamic model with experimental data. Hydrodynamic coupling is shown to be the dominating effect, while the electrostatic influence may often be neglected. Some observations, however, can be explained only by means of a combined electrostatic–hydrodynamic model, which is derived in this work. The combined model is able to predict not only the attractive force between particles of similar charge close to a charged plate but also the change to a purely repulsive force once the sphere‐plate distance is further reduced. This prediction matches qualitatively results of experiments reported in the literature.     

A System for Determination of Precise Isotopic Vapor Pressure Differences from —20 to 110 °C,including Temperature Control to 0·001 over that Range)

An experimental system for the precise measurement of small vapor pressure differences over the range —20 to 110°C is described.     

Einfluß der Nachimpulse des Photosekundärelektronenvervielfachers bei Flüssigkeitsszintillationszählungen

Der Einfluβder Nachimpulse einiger Exemplare des Vervielfachertyps S 12 FS 35 vom VEB Carl Zeiss Jena auf die Flüssigkeitsszintillationszählung wurde in Abhängigkeit von verschiedenen Parametern untersucht. Daraus ergeben sich praktische Hinweise zur Vermeidung von Fehlmessungen durch Nachimpulse, die bei absoluten Aktivitätsbestimmungen mit dem Flüssigkeitsszintillationszähler (z. B. Meβkopf Nr. 25510 der Firma E. Zimmermann, Leipzig) unbedingt zu berücksichtigen sind.     

Direct observations of the leaching of a simulated nuclear waste glass in a radiation environment

The durability of the media proposed for the containment of commercial nuclear waste will be affected not only by the differences in groundwater composition that they might encounter but also by the changes that their own irradiation fields will make to these solutions. Experimental results that question the ability of current leaching experiments to predict the stability of nuclear waste composites are presented.     

DARBOUX POLYNOMIALS FOR LOTKA–VOLTERRA SYSTEMS IN THREE DIMENSIONS

We consider Lotka–Volterra systems in three dimensions depending on three real parameters. By using elementary algebraic methods we classify the Darboux polynomials (also known as second integrals) for such systems for various values of the parameters, and give the explicit form of the corresponding cofactors. More precisely, we show that a Darboux polynomial of degree greater than one is reducible. In fact, it is a product of linear Darboux polynomials and first integrals.     

Effect of long-period stacking ordered phase on thermal stability of refined grains in Mg-RE-based alloys

The refined grains in both as-cast Mg-10Y-1Zn-2Zr (WZ101?K, wt.%) and Mg-10Y-1Al (WA101, wt.%) alloys have been found to have superior thermal stability after solution treatment. Plate-shaped, but different polytypes of long-period stacking ordered (LPSO) phases distributed along grain boundaries are considered as the predominant inhibitors of grain growth. Based on the plate-shaped features of the LPSO phases, a modified Zener’s model is established and the predicted limiting grain sizes are in a good agreement with the experimental results. Therefore, this model has strong potential for designing advanced Mg-RE-based alloys with high strength and high creep resistance at high temperatures.