首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   28篇
  免费   0篇
航空   15篇
航天技术   2篇
航天   11篇
  2018年   2篇
  2012年   2篇
  2011年   7篇
  2009年   2篇
  2008年   2篇
  2007年   1篇
  2006年   1篇
  2004年   1篇
  2003年   1篇
  1999年   1篇
  1997年   1篇
  1996年   1篇
  1994年   1篇
  1989年   1篇
  1985年   1篇
  1979年   1篇
  1975年   1篇
  1967年   1篇
排序方式: 共有28条查询结果,搜索用时 15 毫秒
11.
The Solar Wind Around Pluto (SWAP) instrument on New Horizons will measure the interaction between the solar wind and ions created by atmospheric loss from Pluto. These measurements provide a characterization of the total loss rate and allow us to examine the complex plasma interactions at Pluto for the first time. Constrained to fit within minimal resources, SWAP is optimized to make plasma-ion measurements at all rotation angles as the New Horizons spacecraft scans to image Pluto and Charon during the flyby. To meet these unique requirements, we combined a cylindrically symmetric retarding potential analyzer with small deflectors, a top-hat analyzer, and a redundant/coincidence detection scheme. This configuration allows for highly sensitive measurements and a controllable energy passband at all scan angles of the spacecraft.  相似文献   
12.
13.
14.
This work evaluated the performance of a commercially available face recognition algorithm for the verification of an individual's identity pertaining to three enrollment illumination levels. Existing facial recognition technology from still or video sources is becoming a practical tool for law enforcement, security, and counter-terrorist applications despite the limitations of the current technology. At this time, facial recognition has been implemented in limited applications, but has not been exhaustively studied in adverse conditions, which has initiated continuing study aimed at improving algorithms to compare images or representations of images to recognize a suspect (Paul, 2002). Moreover, this evaluation examined the influence of variations in illumination levels on the performance of a face recognition algorithm, specifically testing the significance between verification attempts and enrollment conditions with respect to factors of age, gender, ethnicity, facial characteristics, and facial obstructions. The results of this evaluation showed that for low and medium illuminance enrollments, there was a statistically significant difference between verification attempts made at low, medium, and high illuminance. However, for the high illuminance enrollment, there was no statistically significant difference between verification attempts made at low, medium, or high illuminance. Furthermore, this evaluation showed that the enrollment illumination level is a better indicator of the verification rate than the verification illumination level.  相似文献   
15.
Dextre: Improving maintenance operations on the International Space Station   总被引:1,自引:0,他引:1  
The Special Purpose Dexterous Manipulator (SPDM), known as “Dextre”, is currently slated to launch in February 2008 for deployment on the International Space Station (ISS) as the final component of Canada's Mobile Servicing System (MSS). Dextre's primary role on the Space Station is to perform repair and replacement (R&R) maintenance tasks on robotically compatible hardware such as Orbital Replaceable Units (ORUs), thereby eventually easing the burden on the ISS crew.This burden on the on-orbit crew translates practically into crew time being a limited resource on the ISS, and as such, finding ways to assist the crew in performing their tasks or offloading the crew completely when appropriate is a bonus to the ISS program. This is already accomplished very effectively by commanding as many non-critical robotics tasks as possible, such as powering up and free-space maneuvering of the Space Station Remote Manipulator System (SSRMS), known as “Canadarm2”, from the Ground.Thus, beyond its primary role, and based on an increasing clarity regarding the challenges of external maintenance on the ISS, Dextre is being considered for use in a number of ways with the objective of improving ISS operations while reducing and optimizing the use of crew time through the use of ground control for various tasks, pre-positioning hardware, acting as a temporary storage platform to break an Extra Vehicular Activity (EVA) day into manageable timelines, and extending the physical reach and range of the Canadarm2.This paper discusses the planned activities and operations for Dextre an rationale for how these will help optimize the use of crew resources on the ISS.  相似文献   
16.
This paper explores the possible relationship between space exploration and long swings in the economy and socio-technical systems. We posit that the early phases of long upswings are characterized by periods of optimism and the spirit of adventure that provided a motivation for large-scale explorations and other great infrastructure projects in the past. These Maslow Windows help us understand prior eras of exploration and cultural dynamism, and offer a hopeful scenario for space exploration in the next two decades. We offer some observations as to what the exploratory thrust might look like, including a return to the lunar surface combined with other activities. Of course, we also point out that the next great wave of space exploration will almost certainly have a much more international flavor than has heretofore been the case.  相似文献   
17.
18.
We introduce the notion of using adaptive (digital) prediction in an intrusion-detection application, where stimuli due to intruders are transient signals. The basic idea is to use an adaptive digital predictor for removing correlated noise. As such, this approach assists in reducing false (nuisance) alarms in the absence of intruder stimuli. It also yields an improvement in signal-to-noise ratio when intruder stimuli are present, thereby assisting in their detection. The performance of this approach is assessed in terms of a fixed-point arithmetic simulation. Some aspects of a corresponding hardware implementation that involves a commercial microprocessor are also included.  相似文献   
19.
Spaceflight personnel need treatment options that would enhance survival from radiation and would not disrupt task performance. Doses of prophylactic or therapeutic agents known to induce significant short-term (30-day) survival with minimal behavioral (locomotor) changes were used for 180-day survival studies. In protection studies, groups of mice were treated with the phosphorothioate WR-151327 (200 mg/kg, 25% of the LD(10)) or the immunomodulator, synthetic trehalose dicorynomycolate (S-TDCM; 8 mg/kg), before lethal irradiation with reactor-generated fission neutrons and gamma-rays (n/gamma=1) or 60Co gamma-rays. In therapy studies, groups of mice received either S-TDCM, the antimicrobial ofloxacin, or S-TDCM plus ofloxacin after irradiation. For WR-151327 treated-mice, survival at 180 days for n/gamma=1 and gamma-irradiated mice was 90% and 92%, respectively; for S-TDCM (protection), 57% and 78%, respectively; for S-TDCM (therapy), 20% and 25%, respectively; for ofloxacin, 38% and 5%, respectively; for S-TDCM combined with ofloxacin, 30% and 30%, respectively; and for saline, 8% and 5%, respectively. Ofloxacin or combined ofloxacin and S-TDCM increased survival from the gram-negative bacterial sepsis that predominated in n/gamma=1 irradiated mice. The efficacies of the treatments depended on radiation quality, treatment agent and its mode of use, and microflora of the host.  相似文献   
20.
In the highly technological aerospace world, paper is still widely used to document space system integration and test (I&T) operations. E-Logbook (electronic logbook) is a new technology designed to replace current documentation processes of space system I&T operations, such as connector mate and demate, flight hardware and flight software component installation, material mixes or electronic ground support equipment (EGSE) validation. It also includes new documentation concepts, such as the shift log, which improves project awareness and optimizes the shift hand-over process, and the configuration log, which instantly reports on the global I&T state of the space system and greatly enhances information gathering prior to major test events or project reviews. The design of E-Logbook focuses not only on a reliable and efficient relational database, but also on an ergonomic human-computer interactive (HCI) system of graphical user interfaces (GUI) that can help reduce human error and improve I&T discipline and management oversight. E-Logbook has been used for the I&T of the large area telescope (LAT) of the gamma-ray large area space telescope (GLAST) scientific satellite at the Stanford Linear Accelerator Center (SLAC). After 19 months of operation, more than 41,000 records have been created for the different documentation components or I&T Logs, with no data having been corrupted or critically lost. 94% of the operators and 100% of the management exposed to E-Logbook prefer it to paper logbooks and recommend its use in the aerospace industry.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号