Demonstration of a high sensitivity GNSS software receiver for indoor positioning

Advances in signal processing techniques contributed to the significant improvements of GNSS receiver performance in dense multipath environments and created the opportunities for a new category of high-sensitivity GNSS (HS-GNSS) receivers that can provide GNSS location services in indoor environments. The difficulties in improving the availability, reliability, and accuracy of these indoor capable GNSS receivers exceed those of the receivers designed for the most hostile urban canyon environments. The authors of this paper identified the vector tracking schemes, signal propagation statistics, and parallel processing techniques that are critical to a robust HS-GNSS receiver for indoor environments and successfully incorporated them into a fully functional high-sensitivity software receiver. A flexible vector-based receiver architecture is introduced to combine these key indoor signal processing technologies into GSNRx-hs™ – the high sensitivity software navigation receiver developed at the University of Calgary. The resulting receiver can perform multi-mode vector tracking in indoor environment at various levels of location and timing uncertainties. In addition to the obvious improvements in time-to-first-fix (TTFF) and signal sensitivity, the field test results in indoor environments surrounded by wood, glass, and concrete showed that the new techniques effectively improved the performance of indoor GNSS positioning. With fine GNSS timing, the proposed receiver can consistently deliver indoor navigation solution with the horizontal accuracy of 2–15 m depending on the satellite geometry and the indoor environments. If only the coarse GNSS timing is available, the horizontal accuracy of the indoor navigation solution from the proposed receiver is around 30 m depending on the coarse timing accuracy, the satellite geometry, and the indoor environments. From the preliminary field test results, it has been observed that the signal processing sensitivity is the dominant factor on the availability of the indoor navigation solution, while the GNSS timing accuracy is the dominant factor on the accuracy of the indoor navigation solution.     

陕西省县域经济发展浅探

党的十六大提出"壮大县域经济"以来,县域经济作为社会经济一种新的发展模式已受到社会各界越来越多的关注.发展壮大县域经济,增强县城经济活力和竞争力,也是陕西省目前经济发展的重要任务之一.通过对陕西省县域经济现状的阐述,指出了存在的问题,提出了强化特色意识、环境意识、开放意识和推进"三化"进程等发展壮大陕西省县域经济的建议和措施.     

航天器环境工程回顾与展望

文章回顾了 2 0世纪航天器环境工程发展的三个主要方面 :在航天器研制中 ,环境工程和环境试验起着重要的作用 ,是验证工作的主要组成部分 ;环境效应、环境模拟试验方法等方面的研究则是环境工程的基础 ;而计算机和数字技术大大促进了整个环境工程和试验技术的发展。在新的世纪 ,环境工程的发展在继续努力降低环境试验的费用和时间的同时 ,提高环境试验的效果 ,使整个环境工程对保证航天器可靠性起到更重要的作用。文章提出了中国在 2 1世纪发展航天器环境工程需要努力的若干方面。     

UWB与GNSS结合的室内外一体化定位系统设计

针对电力北斗安全应用、自动驾驶导航等应用场景对室内外一体化无缝定位的迫切需求,设计了一种将UWB与GNSS结合的一体化无缝定位系统.通过将UWB标签与小型化GNSS模块集成到手持智能设备上形成一体化定位终端,服务器软件对卫导结果与超宽带定位结果进行融合,输出连续定位结果.实验结果表明,该系统可以实现人员的室内外一体化无...     

浅谈高效应力筛选与电子产品可靠性

指出高效应力筛选是保证电子产品可靠性的有效途径。并结合号可靠性工程实际介绍了高效应力筛选的应用情况、典型结果和实践经验，并提出了开展筛选试验的注意事项和当前亟待解决的问题。     

环境因子的分析及应用

本文通过对现行指数分布环境因子的分析，得出了两种环境条件下，产品参数随机变量之间的线性关系，进而对典型正态分布的环境因子的分析，提出了环境因子的二因子法，指出其普遍适用性，给出了应用环境因子对试验数据进行综合的一般步骤，且以实例予以说明。     

Multi-input multi-output random vibration control using Tikhonov filter

Noises always disturb the control effect of an environment test especially in multi-input multi-output (MIMO) systems. If the frequency response function matrices are ill-conditioned, the noises in the driving forces will be amplified and the response spectral lines may awfully exceed their tolerances. Most of the major biases between the response spectra and the reference spectra are pro-duced by the amplified noises. However, ordinary control algorithms can hardly reduce the level of noises. The influences of the noises on both the auto-and cross-power spectra are analyzed in this paper. As a conventional frequency domain method on the inverse problem, the Tikhonov filter is adopted in the environment test to suppress the exceeding spectral lines. By altering regularization parameters gradually, the auto-power spectra can be improved in a closed control loop. Instead of using the traditional way of selecting regularization parameters, we observe the coherence change to estimate noise eliminations. Incidentally, the requirement of coherence control can be realized. The errors of the phase are then studied and a phase control algorithm is introduced at the end as a sup-plement of cross-power spectra control. The Tikhonov filter and the proposed phase control algo-rithm are tested numerically and experimentally. The results show that the noises in the vicinity of lightly damped resonant peaks are more stubborn. The response spectra are able to be greatly improved by the combination of these two methods.     

A novel environmental control system based on membrane dehumidification

This paper conducts a simulation study of a novel aircraft environmental control system based on membrane dehumidification(MD-ECS),and compares the system with the up-to-date four-wheel high pressure de-water system(4WHPDW-ECS).Mathematical models for the two systems are established,and a system simulation using a numerical technique is performed to analyze and compare the cooling performance of the two systems.Simulation results show that the cooling capacity of MD-ECS is much higher than that of 4WHPDW-ECS under the same working conditions,indicating that the novel system is theoretically feasible and promising.The effects of the sweep ratio of the membrane dehumidifier on the dehumidification and cooling performance of the system is also investigated.     

Extraterrestrial environmental impact assessments – A foreseeable prerequisite for wise decisions regarding outer space exploration,research and development

Although existing international instruments such as the Outer Space Treaty and Moon Agreement generally express sentiments for minimizing missions' extraterrestrial environmental impacts, they tend to be limited in scope, vague and generally unenforceable. There is no formal structure for assessing how and to what extent we affect those environments, no opportunity for public participation, no uniform protocol for documenting and registering the effects of our actions and no requirement to mitigate adverse impacts or take them into consideration in the decision-making process. Except for precautions limiting forward biological contamination and issues related to Earth satellites, environmental impact analysis, when done at all, remains focused on how missions affect the Earth and near-Earth environments, not how our actions affect the Moon, Mars, Europa, comets and other potential destinations. Extraterrestrial environmental impacts are potentially counterproductive to future space exploration, exploitation and scientific investigations. Clear, consistent and effective international protocols guiding a process for assessing such impacts are warranted. While instruments such as the US National Environmental Policy Act provide legally tested and efficient regulatory models that can guide impact assessment here on Earth, statutory legal frameworks may not work as well in the international environment of outer space. A proposal for industry-driven standards and an environmental code of conduct based, in part, on best management practices are offered for consideration.     

浅谈环境会计核算方法

生态环境的恶化使环境保护问题日益受到关注,各国不断加强对环境会计核算体系的研究,并取得一定的成果。但是,在我国有关环境会计核算的理论和实务研究尚处于起步阶段。本文从环境会计的内涵着手,对企业环境会计事项包含的内容,以及大循环成本理论下的账户设置进行了较为深入的探讨和研究。以期能对我国相关会计准则的建设、提高环境会计信息的可比性有所助益。