The effects of simulated microgravity on cultured chicken embryonic chondrocytes.

Using the cultured chicken embryonic chondrocytes as a model, the effects of simulated microgravity on the microtubular system of the cellular skeleton, extracellular matrix, alkaline phosphatase activity, intracellular free calcium concentration and mitochondrial ATP synthase activity with its oligomycin inhibition rate were studied with a clinostat. The microtubular content was measured by a flow cytometer. The decrease of microtubular content showed the impairment of the cellular skeleton system. Observation on the extracellular matrix by the scanning electron microscopy showed that it decreased significantly after rotating, and the fibers in the extracellular matrix were more tiny and disorderly than that of the control group. It can be concluded that the simulated microgravity can affect the secreting and assembly of the extracellular matrix. In contrast to the control, there was a time course decrease in alkaline phosphatase activity of chondrocytes, a marker of matrix mineralization. Meanwhile a significant drop in the intracellular calcium concentration happened at the beginning of rotation. These results indicate that simulated microgravity can suppress matrix calcification of cultured chondrocytes, and intracellular free calcium may be involved in the regulation of matrix calcification as the second signal transmitter. No significant changes happened in the mitochondrial ATP synthase activity and its oligomycin inhibition rate. Perhaps the energy metabolism wasn't affected by the simulated microgravity. The possible mechanisms about them were discussed.     

Design and testing of spacecraft power systems using VTB

A study is presented on the design and testing of spacecraft power systems using the virtual test bed (VTB). The interdisciplinary components such as solar array and battery systems were first modeled in native VTB format and validated by experiment data. The shunt regulator and battery charge controller were designed in Simulink according to the system requirements and imported to VTB. Two spacecraft power systems were then designed and tested together with the control systems.     

铝合金精密机箱整体铸造计算机模拟

介绍利用计算机模拟方法进行精密铸造整体机箱工艺设计的结果。     

VELOCITY FIELD OF THERMOCAPILLARY CONVECTION IN HIGH-TEMPERATURE OXIDE SOLUTION

We have investigated experimentally and theoretically the thermocapillary convec tive flow phenomena in a loop-shaped Pt wire heater of KNbO3 (20wt.%) and Li2B4O7 solutions. Optical evaluations in connection with thermocouple measure ments made it possible to get a new type of thermocapillary convective flow in the considered system. To study the kinematical behaviour of thermocapillary convec tion, we have measured the stream flow velocities. In a theoretical analysis, the flow velocity due to the thermocapillary effect alone was estimated by balancing the sur face tension forces by viscous forces. The velocity distribution in the solution near the margin of the heater was obtained, which is in agreement with the experimental result.     

Optimal Cooperative Sensing using a Team of UAVs

The authors investigates the joint optimal estimation of both the position and velocity of a ground moving target (GMT) using pulse Doppler radars on-board unmanned aerial vehicles (UAVs). The problem of cooperative estimation using a UAV team and the optimization of the team's configuration to achieve optimal GMT position and velocity estimates are addressed. Based on the Cramer-Rao bound, the minimum achievable error variance of the GMT position and velocity estimates is derived. The expression of the minimum achievable estimation error variance for unbiased estimation provided by the Cramer-Rao bound is minimized yielding the optimal configuration of the UAV team. Our solution is complete in that it addresses various GMT tracking scenarios and an arbitrary number of UAVs. Optimal sensor geometries for typical applications are illustrated     

500MHz超高速智能计数／定标器

在原子核科学其它许多高技术应用中，对脉冲信号进行计数和定标是一种最基本和应用最为广泛的数据获取方法。随着科学技术的发展，对计数／定标器（Ｃｏｕｎｔｅｒ／Ｔｉｍｅｒ）计数分辨力和仪器的智能化提出了越来越高的要求。目前，在国内核物理及其它科学技术领域所应用的计数／定标器的计数分辨力都不高，通常在１００～２００ＭＨｚ范围。本文报导我们最新研制的一种结构简单、性能优良的、计数率为５００ＭＨｚ的超高速计数／定标器，重点将介绍它的设计原理、研制技术和初步应用结果。     

硅液相外延生长的晶向自动偏离现象

通过对液相外延的薄膜Ｘ衍射测试，结果显示不论衬底是否偏离［１１１］晶向，外延层在同一衍射位置都出现了双峰。经比较分析，确认了硅（１１１）面在液相外延生长时存在晶向自动偏转现象。     

Fault tolerant control system design with explicit consideration of performance degradation

A new approach is proposed for active fault tolerant control systems (FTCS), which allows one to explicitly incorporate allowable system performance degradation in the event of partial actuator fault in the design process. The method is based on model-following and command input management techniques. The degradation in dynamic performance is accounted for through a degraded reference model. A novel method for,selecting such a model is also presented. The degradation in steady-state performance is dealt with using a command input adjustment technique. When a fault is detected by the fault detection and diagnosis (FDD) scheme, the reconfigurable controller is designed automatically using an eigenstructure assignment algorithm in an explicit model-following framework so that the dynamics of the closed-loop system follow that of the degraded reference model. In the mean time, the command input is also adjusted automatically to prevent the actuators from saturation. The proposed method has been evaluated using the lateral dynamics of an F-8 aircraft against actuator faults subject to constraints on the magnitude of actuator inputs. Very encouraging results have been obtained.     

Remote sounding of atmospheric gravity waves with satellite limb and nadir techniques

Recent advances in satellite techniques hold great potential for mapping global gravity wave (GW) processes at various altitudes. Poor understanding of small-scale GWs has been a major limitation to numerical climate and weather models for making reliable forecasts. Observations of short-scale features have important implication for validating and improving future high-resolution numerical models. This paper summarizes recent GW observations and sensitivities from several satellite instruments, including MLS, AMSU-A, AIRS, GPS, and CLAES. It is shown in an example that mountain waves with horizontal wavelengths as short as 30 km now can be observed by AIRS, reflecting the superior horizontal resolution in these modern satellite instruments. Our studies show that MLS, AMSU-A and AIRS observations reveal similar GW characteristics, with the observed variances correlated well with background winds. As a complementary technique, limb sounding instruments like CRISTA, CLAES, and GPS can detect GWs with better vertical but poorer horizontal resolutions. To resolve different parts of the broad GW spectrum, both satellite limb and nadir observing techniques are needed, and a better understanding of GW complexities requires joint analyses of these data and dedicated high-resolution model simulations.     

一种新的切换超平面设计法

本文在文献［１］、［４］的基础之上针对线性系统提出了一种切换超平面的鲁棒设计法。该方法考虑了系统参数的变化，具有强的鲁棒性。设计实例给出了将该方法用于某型海防导弹高度控制回路的仿真结果，其结果是相当令人满意的。