同频法在呼图壁梯级水库洪水计算中的应用

同频率地区组成法是选定某一分区出现与下游设计断面同频率的洪量,其余分区的相应洪量总数则按水量平衡原理推求。根据呼图壁河流域概况,利用坝址同频法和区间同频法对该流域建石门水库入库洪水进行计算,并对两种计算结果进行对比分析。坝址同频法计算成果洪峰流量要略小于区间同频法,而时段洪量要略大于区间同频法,两种方法计算成果总体相差不大。根据下游不同防洪对象应按照对工程最不利影响进行选择。石门水电站推荐坝址同频法;齐古水库推荐区间同频法。

同频法计算控制站地表径流汇出特征分析

利用均匀分布的特征降水与汇出径流同频假定计算控制站地表径流的汇出特征,回避了区域水资源开发利用调查给汇出地表径流系列带来的偏差,并应用次方法计算了天津市入境特征水量,回避了上游水资源开发不同阶段不同程度对径流系列的影响以及该影响给入境水量计算带来的困难。另外,针对不同阶段不同程度的降水径流关系,利用同频法还可以计算和复核相应阶段相应程度下的区域汇出径流水平特征和水资源开发差值,为分析区域建设和规划的基础数据提供相应的计算方法。

关于岩溶地区非闭合流域水库设计径流计算方法的探讨

在新建水库规模论证、供水量计算时,需要进行径流计算。归化河流域为非闭合流域,归化水库坝址有特性不同的5个地表和地下集流区,集水面积为276.0 km 2。归化水库坝址径流计算采用水文比拟法和降水径流同频率相应法两种方法推求年径流,并按照“分块计算再叠加”的方法进行推求。经过水文比拟法与降水径流同频率相应法对比分析,最终推荐水文比拟法径流成果。

无资料流域水库径流计算方法的探讨

在新建水库规模论证、供水量计算时需要进行径流计算。羊叉河水库所在河流为乌江支流猫跳河的一级支流羊叉河上,流域内无实测降雨及径流资料。坝址径流计算以麦翁水文站为参证站采用水文比拟法,以麦格寨雨量站、清镇气象站为参证站采用降水径流同频率相应法推求年径流,并分别采用对应自身降水分配过程和麦翁水文站的径流分配过程进行分配,根据设计流域特性、周边测站分布情况及兴利安全等方面对不同方法的计算结果进行对比分析,最终推荐以麦格寨雨量站为参证站,采用降水径流同频率相应法推求年径流,以麦翁水文站的径流过程进行分配的径流成果,为无资料流域水库的径流计算及成果选择提供参考。

关于闭合流域与袭夺外流域水库径流计算方法的探讨

在新建水库规模论证、供水量计算时需要进行径流计算。赖子河水库所在河流为乌江干流三岔河上游二塘河段,坝址径流计算以阳长水文站为参证站采用水文比拟法,以威宁气象站为参证站采用降水径流同频率相应法推求年径流。经过水文比拟法与降水径流同频率相应法对比分析,最终推荐以威宁气象站为参证站降水径流同频率相应法叠加袭夺外流域径流成果,为闭合流域与袭夺外流域水库径流计算及成果选择提供参考。

Robust Joint Timing and Frequency Synchronization Algorithm for IEEE802.16e OFDM System

Based on the structures of the short preamble and long preamble, which are defined for synchronization in IEEES02.16e specification, the robust synchronization algorithm for IEEES02.16e OFDM system is proposed. The correlations among the sample sequences in the preamble are investigated, especially the correlation between the first sample sequence and the last sample sequence in the long preamble. The conventional joint timing and frequency synchronization algorithm is reviewed based on the short preamble referring to the algorithm proposed by Schmidl, then a robust joint timing and frequency synchronization algorithm is proposed based on the long preamble. The simulations in the multi-path and frequency selective fading channel show that the proposed algorithm has improved the performances of timing metric plateau, timing offset and synchronization acquisition time even when signal-to-noise ratio is less than -5 dB.

Cooperative detection algorithm of spectrum holes in cognitive radio

To improve the detection performance of sensing users for primary users in the cognitive radio, an optimal cooperative detection algorithm for many sensing users is proposed. In this paper, optimal decision thresholds of each sensing user are discussed. Theoretical analysis and simulation results indicate that the detection probability of optimal decision threshold rules is better than that of determined threshold rules when the false alarm of the fusion center is constant. The proposed optimal cooperative detection algorithm improves the detection performance of primary users as the attendees grow. The 2 dB gain of detection probability can be obtained when a new sensing user joins in, and there is a 17 dB improvement when the accumulation number increases from 1 to 50.

Application of Bit Error Rate Information Based on Weighted Error Estimating Code

Error Estimating Code (EEC) is a new channel coding method to estimate the Bit Error Rate (BER) information of the transmitted sequence. However, the estimated BER is not precise enough if the practical value of BER is high. A weighted EEC estimation method is proposed to improve the accuracy performance of BER estimation by classifying the raw estimation results into intervals and multiplying them by different coefficients separately. The applications of weighted EEC in modulation selection scheme and distributed video coding are discussed. Simulation results show that the EEC-based modulation selection method can achieve better performance at a cost of little redundancy and computation, and the EEC-based rate estimation method in distributed video coding can save the decoding time.