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蒋慧君 《西安航空技术高等专科学校学报》2000,18(3):19-21
本以自然通风顶层房间夏季室内热环境的研究对象,运用周期性传热理论,分别针对蓄水、覆土种植和普通传统隔热三种屋面,建立了顶层房间夏季室内热环境的数学模型并进行了验证。 相似文献
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陕西是西部大开发投资的理想首选地,是西部大开发的“桥头堡”,陕西要大有作为,必须有良好的投资环境。陕西的投资环境在基础设施、市场体系、法制环境、服务意识、宣传、人才环境等方面还存在一些问题。因此,陕西必须结合实际,优化投资环境,必须改善基础设施。 相似文献
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一、引言民航空管系统在“三句话、八个字、一严两抓”的总体要求下,以保证空管安全为核心,狠抓各项工作的落实,保持了较好的安全形式,然而空中危险接近和小于间隔飞行仍时有发生。究其原因,并非设备和复杂的技术原因,多为管制员在工作中的人为因素引起的。著名的“木桶效应”告诉我们:木桶的蓄水能力是由其中最短的一块板决定的。空管安全牵涉到方方面面因素, 相似文献
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试论提高我国农村居民消费水平的途径 总被引:3,自引:0,他引:3
付岳瑛 《西安航空技术高等专科学校学报》2005,23(4):37-40
我国农村居民增收缓慢,其中,存在着城乡差别、消费观念守旧,农村消费环境差等因素,使得农村居民的恩格尔系数偏高,消费结构不合理且升级速度缓慢,消费水平难以提升。事实证明,通过加强国家政策扶持,改善消费环境,更新消费观念,推进城市化进程等途径切实增加农民收入,增强购买力,是推动我国农业的可持续性发展,最终全面实现小康社会的必由之路。 相似文献
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谢泗薪 《中国民航学院学报》1999,17(4):69-73
将科技人才成长环境分成外部环境和内部环境两个部分,以及一般环境和具体环境两个层次,提出了成长环境对科技人才成长的作用方式及其影响。在环境管理方面,提出了环境激励和环境管理的涵义、人才成长及流动环境激励的基本模式、科技人才成长环境管理十大设计原则等。初步提出了科技人才成长环境系统优化概念。 相似文献
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介绍了在LabVIEW和Lab Windows/CVI环境下进行测试软件的开发方法,说明了LabVIEW与C语言混合编程的接口技术,以及Lab Windows/CVI环境回调函数的编程和事件驱动编程等高级程序设计技术,并给出一些虚拟仪器应用实例。 相似文献
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Monitoring Changes in Continental Water Storage with GRACE 总被引:1,自引:0,他引:1
The Gravity Recovery and Climate Experiment, GRACE , will enable the recovery of monthly estimates of changes in water storage,
on land and in the ocean, averaged over arbitrary regions having length scales of a few hundred km and larger. These data
will allow the examination of changes in the distribution of water in the ocean, in snow and ice on polar ice sheets, and
in continental water and snow storage. Extracting changes in water storage from the GRACE dataset requires the use of averaging
kernels which can isolate a particular region. To estimate the accuracy to which continental water storage changes in a few
representative regions may be recovered, we construct a synthetic GRACE dataset from global, gridded models of surface-mass
variability. We find that regional changes in water storage can be recovered with rms error less than 1 cm of equivalent water
thickness, for regions having areas of 4 × 105 km2 and larger. Signals in smaller regions may also be recovered; however, interpretations of such results require a careful
consideration of model resolution, as well as the nature of the averaging kernel.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Ehrlich G.M. Hellen R.M. Marsh Orndorh C. Dougherty T.A. 《Aerospace and Electronic Systems Magazine, IEEE》1997,12(9):7-11
Lithium-ion (Li-ion) batteries have demonstrated the ability to fulfill the energy storage needs of many new technologies. The most significant drawbacks of currently available technologies, such as LiCoO 2 based Li-ion cells, is their high cost and significant environmental hazards. Li-ion cells which use a lithium manganese oxide (LiMn2O4) spinel based cathode material should be much less costly and safer than LiCoO2 based cells. Performance data from prismatic design cells which use a LiMn2O4 based cathode material is presented and shown to meet many military performance criteria. The most significant drawback of this technology is the short cycle life 相似文献
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Flywheel technology: past, present, and 21st century projections 总被引:2,自引:0,他引:2
This paper describes the present status of flywheel energy storage technology, or mechanical batteries, and discusses realistic future projections that are possible based on stronger composite materials and advancing technology. The origins and use of flywheel technology for mechanical energy storage began several hundred years ago and was developed throughout the Industrial Revolution. One of the first “modern” dissertations on the theoretical stress limitations of rotational disks (isotropic only) is the seminal work by A. Stodola whose first translation to English was made in 1917. The next big milestones were during the 1960s and 1970s when NASA sponsored programs proposed energy storage flywheels as possible primary sources for space missions. However, it was not until the 1980's when microelectronics, magnetic bearing systems and high power density motor-generators became enabling technologies. The next decade proved that a mechanical battery could surpass chemical batteries for many applications 相似文献
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Regenerative Fuel Cell System (RFCS) technology for energy storage has been a NASA power system concept for many years. Compared to battery-based energy storage systems, RFCS has received relatively little attention or resources for development because the energy density and electrical efficiency were not sufficiently attractive relative to advanced battery systems. Even today, RFCS remains at a very low technology readiness level (TRL of about 2 indicating feasibility has been demonstrated). Commercial development of the Proton Exchange Membrane (PEM) fuel cells for automobiles and other terrestrial applications and improvements in lightweight pressure vessel design to reduce weight and improve performance make possible a high energy density RFCS energy storage system. The results from this study of a lightweight RFCS energy storage system for a remotely piloted, solar-powered, high altitude aircraft indicate an energy density up to 790 wh/kg with electrical efficiency of 53.4% is attainable. Such an energy storage system would allow a solar-powered aircraft to carry hundreds of kilograms of payload and remain in flight indefinitely for use in atmospheric research, Earth observation, resource mapping, and telecommunications. Future developments in the areas of hydrogen and oxygen storage, pressure vessel design, higher temperature and higher pressure fuel cell operation, unitized regenerative fuel cells, and commercial development of fuel cell technology will improve both the energy density and electrical efficiency of the RFCS 相似文献
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This paper describes the current effort to develop a standardized data set, or suite of digital video sequences, that can be used for test and evaluation of digital video motion detectors (VMDs) for exterior applications. We have drawn from an extensive video database of typical application scenarios to assemble a comprehensive data set. These data, some existing for many years on analog videotape, have been converted to a reproducible digital format and edited to generate test sequences several minutes long for many scenarios. Sequences include non-alarm video, intrusions and nuisance alarm sources, taken with a variety of imaging sensors including monochrome CCD cameras and infrared (thermal) imaging cameras, under a variety of daytime and nighttime conditions. The paper presents an analysis of the variables and estimates the complexity of a thorough data set. Some of this video data test has been digitized for CD-ROM storage and playback. We are considering developing a DVD disk for possible use in screening and testing VMDs prior to government testing and deployment. In addition, this digital video data may be used by VMD developers for further refinement or customization of their product to meet specific requirements. These application scenarios may also be used to define the testing parameters for future procurement qualification. A personal computer may be used to play back either the CD-ROM or the DVD video data. A consumer electronics-style DVD player may be used to replay the DVD disk. This paper also discusses various aspects of digital video storage including formats, resolution, CD-ROM and DVD storage capacity, formats, editing and playback 相似文献
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For many military applications, low-frequency oscillators are required which maintain their frequency within 5 parts in 104 after they have been exposed to an acceleration of 30 000 g and also after a storage period of 5 years. In addition, the same stability must exist while a constant acceleration of, say, 5000 g is applied. The characteristics of mechanical systems and various electrical circuits proposed for time bases will be summarized. It will be shown that oscillators, based on the use of RC networks and solid-state negative feedback amplifiers, can fulfill the requirements. It will also be shown that, for cost reduction, the conventional amplitude control over many cycles can be replaced by an instantaneous limiter without detrimental effects on stability. A hybrid timer, consisting of an electronic oscillator, synchronizing a spring-driven mechanical clock, is suggested. 相似文献
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针对"长期贮存,一次使用"装备初始贮存方案评估及优化问题,分析了常见寿命分布组件的可靠度模型,建立了贮存期内组件及装备完好数量评估模型;以达标概率指标为约束条件,组件初始购置费用为优化目标,建立了组件初始贮存方案优化模型,提出了基于边际效益值的优化方法,开展了算法复杂性分析。算例分析表明,所建初始贮存方案评估模型的评估精度较高,优化后的初始贮存方案能够在满足达标概率要求的同时,使得组件购置费用最低。边际优化算法在保持计算精度的同时有效提高了计算效率。提出的模型和优化算法能够为装备保障人员制定合理的装备单元贮存方案提供决策支持。 相似文献
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基于秩相关系数的加速贮存退化失效机理一致性检验 总被引:2,自引:1,他引:1
利用加速贮存试验数据推断长贮产品贮存寿命的前提是,提高应力水平仅仅增大失效速率而不改变失效机理.提出了基于Spearman秩相关系数的贮存退化失效机理一致性检验的非参数定量方法.分析了加速贮存退化失效机理一致性检验的内涵就是检验退化曲线形状的一致性;然后给出了基于Spearman秩相关系数检验配对样本序列一致性的原理和步骤;进一步,通过某型发射药实例数据和单调递减退化仿真数据,验证了方法的有效性. 相似文献
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近年高密度航天发射任务和不断提升的数据采集处理能力使得试验数据规模呈几何级数增长,但目前采用的传统试验数据存储管理和应用服务手段已难以适应任务发展的形势要求.针对航天任务参试系统多、地域跨度广、试验数据采集源多、规模增长迅速、业务应用复杂及用户多样等特征需求,采用云存储和云计算技术,提出了一种基于云平台的分布式数据中心架构,论述了基于两级数据中心的应用服务模式,实现了两级数据中心的整体设计,支持全系统计算资源、存储资源、网络资源和业务资源的统一调度管理,支持计算节点、存储节点和网络节点的动态扩展,能够较好地满足海量飞行试验数据的长期存储管理和高效应用服务需求. 相似文献