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91.
航天器在轨运行过程中面临的空间环境复杂多变,高能电子、等离子体环境、低气压、大温差等环境因素会引起航天器发生静电带电和放电效应,对航天器的安全运行造成严重影响。基于国内外试验数据和案例分析了空间环境引起的航天器故障,从数值仿真软件、地面模拟技术、强场诱发放电以及防护技术等方面介绍了空间环境作用下航天器充放电效应研究进展,对我国目前研究差距和未来研究方向进行了展望。研究表明:我国航天器充放电效应防护技术研究取得了进步,下一步重点针对空间站、深空探测、探月工程等新任务,进一步拓展空间环境作用下航天器充放电效应机理和防护新技术研究,为提升我国航天器的安全性和可靠性提供技术支撑。 相似文献
92.
In the optical multicast network, node and link failures have very important influence on the network survivability which may lead to multiple destinations cannot receive data. Based on the wavelength layered-graph method, a method of efficiency-score based on heuristic algorithm of pre-configured cycle (p-Cycle) based-segment protection (ESHS) for dynamic multicast with limited-range wavelength conversion was presented in this paper. By finding the multicast tree segment protection, the total available p-Cycles are constructed for the multicast. Then we calculate each p-Cycle efficiency-score, the highest efficient-score p-Cycle is selected as the multicast route protection p-Cycle. The simulation results show that the ESHS can get higher performance than the existing ESHT algorithm, in terms of multicast request blocking probability and wavelength utilization. 相似文献
93.
同步降压型DC/DC稳压器XD3407具有使用方便、性能稳定、价格低廉等优点,因此在掌上型个人电脑、蜂窝电话、无线与DSL调制解调器、数码相机和便携式媒体播放器等便携式电子产品领域得到了广泛的应用。主要介绍了XD3407的基本功能和特点,提出了XD3407过流保护模块的电路设计原理、设计分析、计算,并用HSpice软件对结果进行了仿真验证。 相似文献
94.
95.
李明云 《宁波大学学报(理工版)》1998,(3)
象山港毛蚶群体组成以2龄贝为主,占66.10%。体重与壳长之间关系为W=10-4×1.1.175L.其生长规律可用Logitic自然生长方程L1=39.2739/1(1+(为月份)描述。壳长生长曲线的拐点为30月龄,体重生长曲线的拐点为66月龄,合理采捕时间应在生长转折点以后,主要采捕28~34mm大规格的4龄贝,黄墩港和铁港两支港毛蚶的资源实际结算量为929.25t,理论估算量为924.78t,合理捕捞量估算为270~370t采捕季节规定为12月至翌年3月为宜。 相似文献
96.
Amr?T.?Abdel-HamidEmail author Sofiéne?Tahar El?Mostapha?Aboulhamid 《Design Automation for Embedded Systems》2004,9(3):211-227
Intellectual property (IP) block reuse is essential for facilitating the design process of system-on-a-chip. Sharing IP designs poses significant high security risks. Recently, digital watermarking emerged as a candidate solution for copyright protection of IP blocks. In this paper, we survey and classify different techniques used for watermarking IP designs. To this end, we defined several evaluation criteria, which can also be used as a benchmark for new IP watermarking developments. Furthermore, we established a comprehensive set of requirements for future IP watermarking techniques. 相似文献
97.
98.
以某固态放大器控保电路的设计为例,分析在大功率电路中应用CPLD所存在的电源系统干扰、电路干扰、地线噪声干扰和辐射干扰等电磁干扰,并分析这些电磁干扰产生的主要原因.为了抗干扰,从结构设计、电路设计、PCB设计和元器件布局等方面考虑,采用了隔离、屏蔽、滤波、合理接地等具体措施. 相似文献
99.
Wireless LAN technologies such as IEEE 802.11a and 802.11b support high bandwidth and multi-rate data transmission to match
the channel condition (i.e., signal to noise ratio). While some wireless packet fair queuing algorithms to achieve the per-flow
throughput fairness have been proposed, they are not appropriate for guaranteeing QoS in multi-rate wireless LAN environments.
We propose a wireless packet scheduling algorithm that uses the multi-state (multi-rate) wireless channel model and performs
packet scheduling by taking into account the channel usage time of each flow. The proposed algorithm aims at per-flow protection
by providing equal channel usage time for each flow. To achieve the per-flow protection, we propose a temporally fair scheduling
algorithm called Contention-Aware Temporally fair Scheduling (CATS) which provides equal channel usage time for each flow.
Channel usage time is defined as the sum of the packet transmission time and the contention overhead time due to the CSMA/CA
mechanism. The CATS algorithm provides per-flow protection in wireless LAN environments where the channel qualities of mobile
stations are dynamic over time, and where the packet sizes are application-dependent. We also extend CATS to Decentralized-CATS
(D-CATS) to provide per-flow protection in the uplink transmission. Using an NS-2 simulation, we evaluate the fairness property
of both CATS and D-CATS in various scenarios. Simulation results show that the throughput of mobile stations with stable link
conditions is not degraded by the mobility (or link instability) of other stations or by packet size variations. D-CATS also
shows less delay and less delay jitter than FIFO. In addition, since D-CATS can coordinate the number of contending mobile
stations, the overall throughput is not degraded as the number of mobile stations increases.
This work was supported in part by the Brain Korea 21 project of Ministry of Education and in part by the National Research
Laboratory project of Ministry of Science and Technology, 2004, Korea. 相似文献
100.
简要介绍了数字音视频接口的发展背景和技术优势,分析了现有各种数字音视频接口规范,包括DVI、HDMI、UDI和Display Port,重点比较了Display Port和HDMI、DVI的性能,指出数字接口标准存在的问题,并对我国标准化工作提出建议. 相似文献