大坳水电站全计算机监控系统水力机械自动化设计

大坳水电站是江西省首家采用全计算机监控模式并取消常规监控设备的电站 详细介绍了电站水力机械部分自动化系统的设计与基础自动化元件的配置 ,并根据自己的体会提出几点建议     

AN IMPROVED EPON UPSTREAM TRANSMISSION SCHEME WITH ZERO INTER-PERIOD IDLE LOSS

Existing Ethernet Passive Optical Network (EPON) Dynamic Bandwidth Allocation (DBA) algorithms suffer from the disadvantage of idle time loss,which lower the upstream bandwidth utilization.This letter ...     

Distributed channel selection in CRAHNs: A non-selfish scheme for mitigating spectrum fragmentation

In this paper, we consider the problem of spectrum sharing in CRAHNs and propose a distributed channel selection scheme. The key functionality of our proposal, best-fit channel selection (BFC) is that it accounts both the primary channel traffic activity and CR traffic activity in channel selection. We assume CR nodes have the capability of estimating the primary channel traffic activities. In BFC, each CR selects a channel among the primary user (PU) channels for transmission that best fits to its transmission time requirement. We compare the performance of BFC to the widely known longest idle time channel selection (LITC) scheme. In LITC, a CR selects the channel that has the longest expected idle time independent of its transmission needs. In a multi-user CRN, this may degrade the network performance compared to the non-selfish BFC approach. LITC is considered selfish since each CR aims to maximize its own benefit and thus wastes resources that may be utilized by other nodes in the network. BFC providing an efficient spectrum sharing mechanism implicitly mitigates the effect of spectrum fragmentation which is a significant issue degrading the CR spectrum utilization. In CRNs, spectrum may be fragmented in various dimensions, e.g. time and frequency, such that some parts of the spectrum can not be used although being idle. Our proposal provides a solution to the spectrum fragmentation issue in time dimension at the medium access control (MAC) layer. By a set of simulations, we highlight the performance improvement by BFC over the conventional LITC under various CR/PU traffic, number of CRs, estimation accuracy and buffering capability. Simulation results show that the performance of the proposed BFC is significantly superior to that of LITC in terms of probability of successful transmission, spectrum opportunity utilization and fragmentation.     

基于微结构的光谱特征控制技术

制导武器的发展,对目标的隐身以及多波段隐身提出了更高的要求.提出了通过控制目标表面的微结构来控制目标表面光谱特性的一种新技术.利用麦克斯韦电磁场理论,建立了表面微结构与表面光谱特性关系的理论模型,研究了不同材料以及材料表面微结构对光谱特征的影响,并对微结构光谱特征控制技术在红外隐身中应用的可能性进行了分析.研究结果表明:通过控制目标表面的微结构,可以达到控制目标光谱特征的目的,实现目标的红外隐身,为目标的隐身设计提供了一种新思路.     

谈长龙灌区渠道整治措施

本文根据江西省赣州市中型灌区节水配套改造项目原则和要求,针对兴国县长龙灌区渠系及其建筑物目前存在的问题,分别提出了相应的整治措施,为确保灌区渠道输水安全,进一步提高灌区水的利用率和灌溉保证率,从设计方法上提供有益的经验.     

减少频谱泄漏的一种新的等角度间隔采样递推算法

提出并证明了离散傅里叶变换的基相量循环移位性质.就减少频谱泄漏问题,根据基相量循环移位性质提出了一种新的等角度间隔采样算法,并证明了该算法的递推特性.仿真结果表明该算法不仅减少了频谱泄漏,提高了谐波分析精度,而且由于算法具有递推特性,使计算量很小,从而保证了分析实时性.有较强的应用价值.     

直接序列扩频在电力通信中的应用

论述了直接序列扩频技术原理,并设计了实际电力线直扩载波系统方案.通过实验和分析知,基于直接序列扩频技术的电力线通信具有良好的抗干扰性和保密性,是可行、有效的.     

大型水力发电机主保护配置方案综述

大容量发电机的主保护的配置,对发电机本身及整个电网的安全稳定都具有重要意义。针对大型水轮发电机主保护配置方案的应用现状,分析了发电机运行中定子绕组开焊故障时主保护的动作行为,并给出了发电机主保护配置建议。