共查询到20条相似文献,搜索用时 78 毫秒
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闵桂荣 《中国空间科学技术》1991,11(3):1-6
总结了我国卫星的发展道路。指出20年来我国卫星的发展主攻方向是应用卫星,主要目标是高中低三类轨道的通信、遥感和科学实验卫星,发展的步骤采取了步数少、步距大、起点高的途径,发展方针是依靠自力更生和全国大协作。文章扼要介绍了自80年代我国卫星转入应用后的情况,已在教育、广播、通信、资源、测绘、气象、科学研究和国防建设等领域应用并作出了巨大贡献。文章最后指出了我国90年代卫星应用的光明前景。 相似文献
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以临近空间飞艇为对象,针对传统外形设计方法中存在的问题,提出了新的优化设计方法,搭建了流程框架,编制了优化程序。首先研究了遗传算法及多学科设计理论,进而在此基础上建立了飞艇阻力、体面比、应力模型,利用多学科设计理念对飞艇气动、结构、强度进行了一体化设计。其次将遗传算法引入到优化设计当中,并利用Matlab和Fluent开展了联合仿真研究。最后结合实际应用需求进行了算例分析,验证了该方法的可行性和效果。 相似文献
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<正>1970年4月24日,我国成功地研制并发射了第一颗人造地球卫星东方红-1,拉开了中国航天活动的序幕。45年来,中国的航天事业在人造卫星、载人航天和深空探测三个领域都取得了辉煌成就,进一步增强了中国的经济、国防、科技实力和民族凝聚力。首先,我国已建立了配套的航天基础设施。这些基础设施包括运载火箭、航天器、发射场、 相似文献
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Lanfang H. Levine Patricia A. Bisbee Jeffrey T. Richards Michele N. Birmele Ronald L. Prior Michele Perchonok Mike Dixon Neil C. Yorio Gary W. Stutte Raymond M. Wheeler 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(5):754-762
This study addresses whether reduced atmospheric pressure (hypobaria) affects the quality traits of radish grown under such environments. Radish (Raphanus sativus L. cv. Cherry Bomb Hybrid II) plants were grown hydroponically in specially designed hypobaric plant growth chambers at three atmospheric pressures; 33, 66, and 96 kPa (control). Oxygen and carbon dioxide partial pressures were maintained constant at 21 and 0.12 kPa, respectively. Plants were harvested at 21 days after planting, with aerial shoots and swollen hypocotyls (edible portion of the radish referred to as the “root” hereafter) separated immediately upon removal from the chambers. Samples were subsequently evaluated for their sensory characteristics (color, taste, overall appearance, and texture), taste-determining factors (glucosinolate and soluble carbohydrate content and myrosinase activity), proximate nutrients (protein, dietary fiber, and carbohydrate) and potential health benefit attributes (antioxidant capacity). In roots of control plants, concentrations of glucosinolate, total soluble sugar, and nitrate, as well as myrosinase activity and total antioxidant capacity (measured as ORACFL), were 2.9, 20, 5.1, 9.4, and 1.9 times greater than the amount in leaves, respectively. There was no significant difference in total antioxidant capacity, sensory characteristics, carbohydrate composition, or proximate nutrient content among the three pressure treatments. However, glucosinolate content in the root and nitrate concentration in the leaf declined as the atmospheric pressure decreased, suggesting perturbation to some nitrogen-related metabolism. 相似文献
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Shuanggen Jin Sundaram Arivazhagan Hiroshi Araki 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The moon has longstanding questions such as lunar environments, origin, formation and evolution, magnetization of crustal rocks, internal structure and possible life. The recent lunar missions, e.g., SELenological and ENgineering Explorer “KAGUYA” (SELENE), Chang’E-1, Chandrayaan-1, and Lunar Reconnaissance Orbiter/Lunar CRater Observation and Sensing Satellite (LRO/LCROSS), have provided new opportunities to explore and understand these issues. In this paper, we reviewed and presented the results and findings in the fields of lunar gravity, magnetic field, atmosphere, surface geomorphology and compositional variations, volcano, craters, internal structure, water and life science from new lunar exploration missions. In addition, the new objectives and scientific questions on lunar explorations in near future are presented and discussed. 相似文献
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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(7):3005-3021
Precipitation is an important component of the hydrological and energy cycles, as well as a key input parameter for many applications in the fields of hydrology, climatology, meteorology, and weather forecasting research. As a result, estimating precipitation accurately is critical. The purpose of this research is to conduct a comprehensive and comparative evaluation of grid-based precipitation products over Turkey's Mediterranean region from 2017 to 2021 at monthly and grid scales, using data from 193 ground-based meteorological stations as a reference. PERCIANN CCS, PDIR-Now, GSMaP MVK, PERSIANN CDR, CHIRPS, IMERG v6, GSMaP Gauge, and ERA5 are the eight grid-based precipitation products. Several prospective were used to evaluate the products, including magnitude agreement with gauge stations for the entire region and the six hydrological sub-basins included in the region, performance in capturing various intensity categories, and elevation dependency. According to the evaluation results, PERCIANN CDR, CHIRPS, IMERG v6, GSMaP Gauge, and ERA5 performed well in all evaluation aspects, whereas PERCIANN CCS, PDIR-Now, and GSMaP MVK performed poorly in all metrics. The majority of the products underestimated heavy rainfall events, while all products performed better at low and moderate precipitation events. As a result, the products performed better in the summer and spring months (March to October) than in the winter months (December to February). Furthermore, the results showed that the performance of the majority of the products degraded for elevations greater than 1000 m. The evaluation suggests that PERSIANN CDR, CHIRPS, IMERG v6, GSMaP Gauge, and ERA5 can be used as good precipitation data sources and as a complement to ground-based meteorological stations in Turkey's Mediterranean region. 相似文献
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飞机板金成形数据库的开发 总被引:2,自引:1,他引:1
为了配合航空工业进一步技术更新,以信息化技术提升传统的飞机板金工艺,根据航空工业飞机生产、型号预研、板金工艺手册、工艺实验等大量数据信息,基于Sybase数据库管理系统,应用PowerBuilder开发软件,研究开发了一套集板材性能、成形工艺、机床设备、工装模具等数据资料的飞机板金成形数据库系统(Ashbase).对该系统在设计思想、总体结构、系统功能、数据表现等方面的设计与实现方法进行了分析. 相似文献
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国外高光谱遥感载荷发展分析 总被引:1,自引:1,他引:0
高光谱遥感是当前遥感领域发展的前沿。首先介绍了高光谱遥感的成像原理、典型成像方式及主要特点等基础理论,之后从机载和星载两个方面,系统梳理了美国、加拿大、欧洲、日本等主要国家高光谱遥感载荷的发展现状,分析了相关载荷的主要性能指标(以空间分辨率、频谱分辨率等为代表),总结、归纳了高光谱遥感在民用商用、国防安全及行星探测三个领域中的应用情况,最后从提升分辨率、优化探测模式及实现小型化三个方面,总结了高光谱遥感载荷的发展趋势。 相似文献
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为提高机器人的负载能力,基于几何分析和螺旋理论的基本原理,对绳驱动 拟人臂机器人的构型设计、钢绳传动方式和运动学控制问题进行了深入的分析.首先针对绳 驱动走线方式的多样性选择,设计了一种具有肘、腕关节耦合和肩、肘关节耦合的绳驱动传 动机构;然后以肩、肘、腕7-DOF关节为中间媒介对机器人末端和驱动钢绳间的运动学关系 进行了分析,即先考虑机器人末端位姿和各关节角度之间的关系,再研究各关节角度和其相 应的驱动钢绳绳长之间的关系,从而得到绳驱动机器人的运动学解;最后进行了仿真研究. 仿真结果显示机器人的关节角度和绳长变化曲线十分平滑,末端的实际轨迹跟踪理想轨迹的 误差非常微小,说明建议的算法正确,绳驱动机器人运行理想,可以有效克服常规机器 人自重过大带来的负面影响. 相似文献
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面向领域的仿真设计建模工具SIMDEMO 总被引:2,自引:0,他引:2
讨论了面向领域的仿真设计建模工具SIMDEMO的设计和实现.基于透明性、正交性、层次性的视图分解原理,对处于不同阶段、面向不同用户、涉及不同方面的系统模型采用多视图进行分解,建立了以多视图为核心理念的系统协同建模方法,给出了该建模方法下建模所需遵循的过程指导.针对领域模型描述、表示以及操作等多个方面对工具重构的需求,研究得到了基于元对象反射模型的工具架构;架构具有良好适应性,使得工具重构更灵活、简捷.对SIMDEMO的功能结构进行了简介,给出了系统实现方案.最后,将SIMDEMO与典型同类工具作了比较. 相似文献
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航天微波部件的无源互调抑制方法研究进展 总被引:2,自引:0,他引:2
无源互调(passive intermodulation,PIM)问题广泛存在于大功率微波无源部件及系统中,对卫星及地面通信系统造成严重的干扰.无源互调抑制方法是无源互调基础研究和工程应用中的重点关注领域,是解决无源互调问题的核心关键.在阐述无源互调产生机理的基础上,分别从工艺、结构、电设计及信号处理等多个方面系统地归... 相似文献