Analysis on Potential Conflict Frequency of Intersected Air Routes in Terminal Airspace Design

In order to obtain accurate conflict risks in terminal airspace design, the concept and calculation model of potential conflict frequency for intersected routes are proposed. Conflict frequency is represented by the product of horizontal conflict frequency and vertical conflict probability. The horizontal conflict frequency is derived from the probability density distribution of conflicts in a period of time. Based on the recorded radar trajectory data, the concept and model of ROUTE distance are proposed, and the probability density function of aircraft height at a specified ROUTE distance is deduced by kernel density estimation. Furthermore, vertical conflict probability and its horizontal distribution are achieved. Examples of three intersected arrival and departure route design schemes are studied. Compared with scheme 1, the conflict frequency values of the other two improved schemes decrease to 53 % and 24%, respectively. The results show that the model can quantify potential conflict frequency of intersec ted routes.     

新型宽带SiC功率器件在电力电子中的应用

新型宽带SiC功率器件由于其突出的性能优势在电力电子领域得到了广泛应用。首先介绍了SiC功率器件的发展现状,其次阐述了其性能特点,最后给出了SiC功率器件目前在新能源、民用输配电、航空航天等场合的应用情况,指出了SiC器件在电力电子领域的应用前景。     

论大学生思想政治教育新媒体利用的机遇与挑战

在技术发展、教育时空领域扩大、党和政府政策支持、师生媒介素养提升的条件下,大学生思想政治教育新媒体利用迎来了一系列的机遇。与此同时,也遭遇了以下挑战：信息风暴带来了大学生思想政治教育新媒体利用的难以分辨和选择;虚拟空间交往方式的异化产生了大学生思想政治教育新媒体利用的隐痛;依赖的强化造就了大学生思想政治教育新媒体利用过程中的控制和反控制;身心健康受影响,成为大学生思想政治教育新媒体利用的忧患。     

高职聋哑生就业指导中的思想政治教育问题研究

聋哑人作为社会的弱势群体,在接受高等教育之后,同样需要面临着就业问题,由十其身体的缺陷造成的心理的问题,对于其就业产生了极大的问题和障碍,因此,在高职聋哑学校对学生的就业指导中加强思想政治教育就显的十分重要。本文就高职聋哑生就业指导中的思想政治教育对策相关内容进行了研究。     

姿态角幅值约束下的太阳帆Lissajous轨道保持控制

太阳帆航天器以两姿态角作为轨道控制输入时, 其轨道动力学方程具有非仿射非线性特性. 通过人工平动点处线性化获得的线性系统可完成太阳帆航天器轨道保持控制器的分析与设计. 由于线性近似模型为有误差模型, 存在近似有效范围约束, 表现为轨道高度约束和姿态角幅值约束. 本文研究了姿态角幅值约束对线性近似模型有效性的影响, 通过计算给出满足近似误差要求的姿态角幅值约束. 当控制输入存在幅值约束时, 控制器轨道修正能力受到束缚. 通过研究姿态角幅值约束下的最大允许入轨误差, 设计了最大允许入轨误差下线性二次型调节器(LQR)用于轨道保持控制, 并将控制器应用于太阳帆日地三体系统非线性模型中, 实现了日地人工L₁点Lissajous轨道最大允许入轨误差的控制收敛和良好精度下的轨道保持控制.      

New trade tree for manned mars missions

Recent studies on human missions to Mars suggest revisiting the parameters that have the most important impact on the complexity, the initial mass in low Earth orbit, the risks and the development costs for the first journey to the red planet. In the last NASA reference mission, a trade tree is proposed.     

United Nations Human Space Technology Initiative (HSTI)

The Human Space Technology Initiative was launched in 2010 within the framework of the United Nations Programme on Space Applications implemented by the Office for Outer Space Affairs of the United Nations. It aims to involve more countries in activities related to human spaceflight and space exploration and to increase the benefits from the outcome of such activities through international cooperation, to make space exploration a truly international effort.     

Self-perspiration garment for extravehicular activity improves skin cooling effects without raising humidity

Introduction

The current U.S. extravehicular activity (EVA) suit in space includes liquid cooling and ventilation garment (LCVG) to control thermal condition. Tubes knitted in LCVG for flowing water interrupt evaporation of perspiration, and astronauts feel discomfort. In the present study, we hypothesized that a self-perspiration garment would effectively lower the skin temperature without raising humidity in the garment. Thus, we developed and examined the effects of the garment.

Methods

Eight healthy subjects were studied with a cyclic ergometer of 30, 60 90 and 120 W loading for 3 min each. Skin temperature and humidity on the back were measured continuously. Subjects wore and tested three types of garments i.e., a spandex wear without any cooling device (Normal), a simulated LCVG (s-LCVG) or the spandex wear knitted a vinyl tube for flowing water, and the spandex wear with a tube, which flows water and self-perspiration with oozing water for evaporative cooling (SPEC).

Results

All measurements were reached to steady state 2–3 min after the setting. The s-LCVG decreased skin temperature 0.39±0.14 °C during 12 min of cooling. With SPEC, skin temperature did not decrease significantly until 6–9 min after starting the cooling. However, the temperature decreased rapidly and significantly after that, and finally decreased 1.59±0.32 °C. Humidity in the SPEC was significantly lower than that in s-LCVG.

Discussion

SPEC was effective for lowering skin temperature without raising humidity in the garment. The concept is expected to use as a better cooling system during EVA.     

An innovative navigation scheme of powered descent phase for Mars pinpoint landing

Pinpoint landing (within 100 m from the target) is essential for future Mars exploration missions. This paper deals with one aspect of the pinpoint landing architecture—the navigation performance improvement during the powered descent phase, and proposes an innovative navigation scheme to obtain the vehicle complete and accurate states. On the basis of dead reckoning relying on the Inertial Measurement Unit, measurements of the Integrated Doppler Radar are adopted to correct the vehicle velocity and altitude. Distance between the vehicle and one Mars Orbiter as well as their line-of-sight relative velocity is measured by a radio sensor, and integrated in the filter to correct the vehicle horizontal position. The innovative navigation system is based on an Extend Kalman Filter. Two observation schemes are developed. One considers measurements of the Integrated Doppler Radar and radio range measurement. Another further considers radio velocity measurement. The performance of the innovative navigation scheme is greatly influenced by the position of the Mars Orbiter with respect to the target. Stochastic analyses are performed to obtain optimal locations of Mars Orbiter. Finally, the innovative navigation scheme performances are assessed through stochastic simulations. Its performance improvements are demonstrated by comparison with the Integrated Doppler Radar only navigation scheme.