临近空间飞艇内部自然对流换热计算研究

综合考虑太阳辐射、长波辐射、对流换热等热环境因素对临近空间飞艇热特性的影响,建立飞艇热特性的数学模型,编写程序并计算得到蒙皮表面温度分布。以此作为热边界条件,采用Fluent软件模拟其内部自然对流的流动状态和温度分布,对不同季节不同时刻飞艇内部自然对流换热系数进行了计算分析,并对四个自然对流经验公式进行了评价分析。结果表明,Eckert-Jackson和Bayley公式更适用于计算浮空器内部自然对流换热,与数值模拟结果相比,平均绝对误差（MAD）分别为22.6%和24.1%。     

卫星导航地面试验验证的平行系统方法

应用平行系统理论,研究全球卫星导航系统（GNSS）人工建模、计算实验和平行执行的方法。首先构建GNSS平行系统框架,分析GNSS平行系统人工建模的关键技术,提出基于代理（Agent）的导航系统实体建模方法;然后根据计算实验需求,设计GNSS平行系统在人工建模、试验支持与运行维护等方面的计算实验方法及流程。在此基础上,给出GNSS平行系统的运行模式及其平行执行过程。最后,以GNSS平行系统在人员培训方面的应用为例,说明GNSS平行系统在实际GNSS运行维护方面的应用。研究结果表明,建立GNSS平行系统是提高GNSS建设和运行维护效率的有效方法。     

有无涵道动力下的类BWB低速布局气动特性研究

随着航空飞行器的不断发展,新型非常规气动布局研究早已成为世界航空大国的关注焦点。基于TRIP 3.0软件平台通过等效盘模型应用到涵道风扇内外流一体化模拟中,完成对类BWB低速布局有无涵道风扇动力下的气动特性和流场影响分析。首先,对某单独螺旋桨验证算例进行分析;然后,对单独涵道风扇进行计算,得到设计推力下的涵道动力叶片数、安装角及转速等参数;最后,将设计推力下涵道动力参数应用到类BWB低速布局全机有无动力模拟中。结果表明:计算拉力和扭矩值与试验值吻合较好;尾部布置的涵道动力对机身后段及尾翼压力分布影响显著;涵道对前方气流抽吸作用,加速机身后段上表面气流流速,减小内侧平尾有效迎角,对机身和平尾升力以及俯仰力矩系数影响较大;在小迎角状态下,涵道动力对机身增升作用明显,会产生明显低头力矩,但对平尾作用正好相反,且两者增量大小相当,使得全机增升效果不显著,且俯仰力矩变化较小。     

Predicting the probability of occurrence of spread-F over Brazil using neural networks

The probability of occurrence of spread-F can be modeled and predicted using neural networks (NNs). This paper presents a feasibility study into the development of a NN based model for the prediction of the probability of occurrence of spread-F over selected equatorial stations within the Brazilian sector. The input space included the day number (seasonal variation), hour (diurnal variation), sunspot number (measure of the solar activity), magnetic index (measure of the magnetic activity) and magnetic position. Twelve years of spread-F data from Brazil (covering the period 1978–1989) measured at the equatorial site Fortaleza (3.9°S, 38.45°W) and low latitude site Cachoeira Paulista (22.6°S, 45.0°W) are used in the development of an input space and NN architecture for the model. Spread-F data that is believed to be related to plasma bubble developments (range spread-F) was used in the development of the model. The model results show the probability of spread-F occurrence as a function of local time, season and latitude. Results from the Brazilian Sector NN (BSNN) based model are presented in this paper, as well as a comparative analysis with a Brazilian model developed for the same purpose.     

Russia's resurgence: Prospects for space policy and international cooperation

Based on a joint study initiated in 2007–2008 by the Policy planning staff (CAP) of the French Foreign Ministry and the space agency CNES, which brought together experts, researchers and industry insiders, this article considers the factors behind Russia's recent resurgence and the possible revival of its space programme. It examines how far the latter will require international cooperation in order to progress further and discusses likely areas of profitable collaboration with Europe in general and France in particular, given that country's long history of space cooperation with Russia and the need in the mid-term future to share the burden of developing ambitious new space programs. While there is in principle much potential, especially in the area of space transportation, there are also numerous challenges and uncertainties. How these are resolved will affect the level and success of any cooperative efforts of both sides.     

Lunar astrobiology: a review and suggested laboratory equipment

In October of 2005, the European Space Agency (ESA) and Alcatel Alenia Spazio released a "call to academia for innovative concepts and technologies for lunar exploration." In recent years, interest in lunar exploration has increased in numerous space programs around the globe, and the purpose of our study, in response to the ESA call, was to draw on the expertise of researchers and university students to examine science questions and technologies that could support human astrobiology activity on the Moon. In this mini review, we discuss astrobiology science questions of importance for a human presence on the surface of the Moon and we provide a summary of key instrumentation requirements to support a lunar astrobiology laboratory.     

速率偏频激光陀螺偏频速率模糊PID自适应控制的设计与实现

应用模糊 PID自适应技术设计并实现了激光陀螺偏频速率的控制系统,结果表明 :偏频台速率平稳性优于 3.1 2× 1 0 - 4;角速率正反换向速度快,在± 60°/ s之间的转换时间约为 1 4 ms,而且换向过程速率超调很小。该控制系统在实际系统中得到了良好的应用     

Contributions from nearby pulsars to the local cosmic ray electron spectrum

PSR J0437-4715 is one of the closest millisecond pulsars (MSPs) to Earth, lying at a distance of ∼140 pc. This pulsar has a characteristic age of 4.9 Gyr and a relatively low spindown power of ∼10³⁴ ergs/s. During its rather long lifetime, a large fraction of the energy output has been in the form of multi-TeV electrons. In this paper, we investigate the possible contribution of this nearby MSP to the local interstellar electron spectrum (LIS). The old age of the system justifies a steady-state evaluation of the contribution from this pulsar to the LIS. We calculate the electron spectrum at the light cylinder in the framework of a General Relativistic polar cap (PC) model, and use this as an injection spectrum in a diffusion model. The younger Geminga pulsar is also very close to Earth and warrants investigation. A steady-state approach is however no longer justified, so we use an impulsive injection model. We will present results of a study of the contribution from these pulsars to the cosmic ray (CR) LIS. Our calculations show that pulsars like Geminga can make a non-negligible contribution to the LIS.     

Teaching astronomy for pre-service elementary teachers: A comparison of methods

This study investigates the effect of text structure and “hands-on” methods in the acquisition of the concepts of moon phases and seasons for pre-service elementary teachers. The goal is to evaluate the most appropriate method for facilitating conceptual change. The presentation of two main misconceptions associated with each concept (moon phases and seasons) is tested. Sixty pre-service elementary teachers are divided into three same size experimental groups after a pre-test on their knowledge about astronomy: one group read a simple expository text that presents factual information about seasons and moon phases, another group read a refutation text that moreover presents explicitly two main and usual misconceptions about each concept and arguments to refute them; the last group participates to a refutation modelling activity by testing, for each concept, three hypothesis: the scientific explanation and the two common misconceptions. The hands-on method is used as a way to refute the pre-conceptions thanks to a collaborative activity in small groups.     

Astrobiologically interesting stars within 10 parsecs of the sun

The existence of life based on carbon chemistry and water oceans relies upon planetary properties, chiefly climate stability, and stellar properties, such as mass, age, metallicity, and galactic orbits. The latter can be well constrained with present knowledge. We present a detailed, up-to-date compilation of the atmospheric parameters, chemical composition, multiplicity, and degree of chromospheric activity for the astrobiologically interesting solar-type stars within 10 parsecs of the Sun. We determined their state of evolution, masses, ages, and space velocities, and produced an optimized list of candidates that merit serious scientific consideration by the future space-based interferometry probes aimed at directly detecting Earthsized extrasolar planets and seeking spectroscopic infrared biomarkers as evidence of photosynthetic life. The initially selected stars number 33 solar-type within the total population (excluding some incompleteness for late M-dwarfs) of 182 stars closer than 10 parsecs. A comprehensive and detailed data compilation for these objects is still lacking; a considerable amount of recent data has so far gone unexplored in this context. We present 13 objects as the nearest "biostars," after eliminating multiple stars, young, chromospherically active, hard x-ray- emitting stars, and low metallicity objects. Three of these "biostars"-- Zeta Tucanae, Beta Canum Venaticorum, and 61 Virginis -- closely reproduce most of the solar properties and are considered as premier targets. We show that approximately 7% of the nearby stars are optimally interesting targets for exobiology.