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排序方式: 共有274条查询结果,搜索用时 15 毫秒
1.
随着TD-LTE网络建设规模的加大,并且引入双频组网和载波聚合的技术,现有PTN接入层网络结构无法满足TD-LTE基站的回传需求.通过对PTN接入层网络现状以及TD-LTE业务发展需求的分析,对不同接入场景下的PTN接入层网络提出相应的方案,为LTE传送网接入层演进策略提供参考.  相似文献   
2.
光网络设备(Optical Network Terminal,ONT)是XPON网络接入方案中的产品,是一种应用在用户端的光网络终端,有GPON和EPON。介绍以PON ONU SOC为主控芯片的16线POTS ONT的硬件设计及遇到的问题以及如何解决这些问题。此设计是一款基于GPON(ITU-T G. 984)标准并支持以太网和语音接口的ONT,适用于北美市场,满足NEBS1标准。本设计的特点是有16线的语音用户接口和1个GE的接口,上联是GPON,支持Dying Gasp且功耗低。  相似文献   
3.
Stability analysis is an essential issue in Min–Max multiregulator control strategy for commercial aircraft engines. In this paper, a Min–Max selector scheme along with a stability analysis method is provided for aeroengine propulsion control. It is assumed that the main regulator is a dynamic compensator and the limit regulators are constant gains. The regulators are determined in such a way that the individual control loops are stable. However, due to the switching nature of Min–Max structure, the stability of single loops does not necessarily ensure the overall system stability. In order to analyze the stability of the presented Min–Maxapproach, the architecture of the control system is transformed into the canonical form of Lure’s system and the condition for absolute stability is specified using Multivariable Circle Criterion. The theoretical results can also be applied to investigate the stability of min-only or max-only schemes. Afterwards, using the provided methodology, the global asymptotic stability is proved for the control system of a high bypass two-spool turbofan engine and the performance of the designed Min–Max controller in tracking a desired fan speed and limit protection in fault-free and fault tolerant situations is compared with the well-known Min–Max/SMC approach.  相似文献   
4.
This paper proposes a new multi-objective framework for optimal placement and sizing of the active power filters (APFs) with satisfactory and acceptable standard levels. total harmonic distortion (THD) of voltage, harmonic transmission line loss (HTLL), motor load loss function (MLLF), and total APFs currents are the four objectives considered in the optimization, while harmonic distortions within standard level, and maximum allowable APF size, are modeled as constraints. The proposed model is one of non-convex optimization problem having a non-linear, mixed-integer nature. Since, a new modified harmony search algorithm (MHSA) is used and followed by a min–max technique in order to obtain the final optimal solution. The harmony search algorithm is a recently developed optimization algorithm, which imitates the music improvisation process. In this process, the Harmonists improvise their instrument pitches searching for the perfect state of harmony. The newly developed method has been applied on the IEEE 18-bus test system and IEEE 30-bus test system by different scenarios and cases to demonstrate the feasibility and effectiveness of the proposed method. The detailed results of the case studies are presented and thoroughly analyzed. The obtained results illustrate the sufficiency and profitableness of the newly developed method in the placement and sizing of the multiple active power filters, when compared with other methods.  相似文献   
5.
Effective conservation planning relies on the accurate identification of anthropogenic land cover. However, accessing localized information can be difficult or impossible in developing countries. Additionally, global medium-resolution land use land cover datasets may be insufficient for conservation planning purposes at the scale of a country or smaller. We thus introduce a new tool, GE Grids, to bridge this gap. This tool creates an interactive user-specified binary grid laid over Google Earth's high-resolution imagery. Using GE Grids, we manually identified anthropogenic land conversion across East Africa and compared this against available land cover datasets. Nearly 30% of East Africa is converted to anthropogenic land cover. The two highest-resolution comparative datasets have the greatest agreement with our own at the regional extent, despite having as low as 44% agreement at the country level. We achieved 83% consistency among users. GE Grids is intended to complement existing remote sensing datasets at local scales.  相似文献   
6.
The efficacy of grape seed extract (GE), citric acid (CA) or lactic acid (LA) on the inactivation of Vibrio parahaemolyticus in shucked oysters was studied. The minimum inhibitory concentration (MIC) of GE, CA or LA against V. parahaemolyticus in TSB-1% NaCl was also determined. The shucked oysters were artificially inoculated with V. parahaemolyticus, the inoculated shucked oysters (25 g) were then dipped in solution of GE (0.0, 10.0, 20.0, 50.0, 100, 200, 300 and 500 mg mL−1), CA (0.0, 5.0, 10.0, 15.0, 20.0, 50.0, 100, 200 and 300 mg mL−1) or LA (0.0, 1.0, 5.0, 10.0, 15.0, 20.0, 50.0, 100 and 150 mg mL−1) for 10 min. The population of V. parahaemolyticus in shucked oysters was determined. The MICs of GE, CA or LA against V. parahaemolyticus were 10.0, 5.0 or 1.0 mg mL−1, respectively. A 500, 300 or 150 mg mL−1 GE, CA or LA solutions were needed to reduce the population of V. parahaemolyticus to below the detection level (1.0 log g−1) in shucked oysters.  相似文献   
7.
输电工程中线路路径的选择决定着工程的合理性、经济性,关系着电网的可靠运行与维护,其最优路径选择至关重要.阐述了输电工程的传统设计方法,并着重介绍了影像地图在输电工程野外终勘中的应用.对提高输电工程设计工作效率具有参考意义.  相似文献   
8.
简要地介绍了某地市移动公司接入网的现状,分析了接入层不同的网络场景,针对TD-LTE对传输网的需求,提出了可行的PTN接入网的优化方案。  相似文献   
9.
10.
陈元招 《电气技术》2012,(7):40-43,47
某生活小区原供水系统依靠阀门实现水量控制,水泵在额定状态下运行,机械磨损较大,使用成本高。通过采用GE300和变频器组合的控制系统改造,完成系统的软硬件设计及参数设置,能自动控制水泵投入的台数和电机转速,达到恒压供水目的。运行结果表明,该系统具有压力恒定,机械损耗小,节能效果显著等优点。  相似文献   
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