基于FPGA的快速原地转置算法

随着合成孔径雷达成像系统对实时性要求的提高,基于FPGA平台的SAR成像系统越来越多。图像矩阵转置作为SAR成像系统的必要处理过程之一,其效率一直制约着SAR成像系统的实时性。本文提出了一种基于FPGA的快速原地转置算法,首先将矩阵分割为大小相等的子矩阵块,利用上位机预先计算出子矩阵块转置前后地址并生成地址序列表,在FPGA上依据地址序列表顺次移动子矩阵块。实验结果表明,相比非原地转置算法,这种原地转置算法使用的辅助空间仅为矩阵空间的0.2%,多耗费2%的时间。这种算法提高了转置效率,降低了转置存储开销,对SAR实时成像系统的有重要意义。     

Strand Current Distribution Modeling in Turbo-generators Using Finite-element Method Based on Proposed Dual Method

Abstract—The necessity of using a 3D model is one of the main problems for modeling Roebel bar transposition in turbo-generators by the finite-element method. This article proposes a 2D dual model for computing strand current distribution in the Roebel bar of turbo-generators. Considering the leakage and mutual inductances for each strand and the coupling inductances between them, the end winding region is modeled in this 2D dual model. In this article, the Roebel bar structure including 16 strands was considered, and these distributions are calculated for different transpositions using the finite-element method. In the finite-element method model, the circulating currents are calculated by subtracting a load current at each strand from the total of strand current. Also, for different transpositions, such as 90°, 180°, 360°, and 540°, the circulating currents are calculated using an analytical method. The obtained strand current distributions from the 2D dual model have good agreement with the obtained results from the analytical method for the 180° and 360° transposed coil models.     

A 1916 World War I notebook of Luigi Sacco

Letters, notes, and above all an original notebook by Luigi Sacco dated 1916 have shed new light on the establishment and development of the “Ufficio (or Reparto) Crittografico” of the Italian Army Headquarters in World War I. Three decrypted messages, unpublished until now, are included with Sacco’s comments.     

Transposition based contextual insertion on linear DNA strands with deletion precedence

Insertion and deletion operations are two most important operations in molecular computation, and recently these two operations gained interest in the context of molecular computation. In the proposed system, single contextual insertion and usual (with two contexts) contextual deletions are used. In addition, it is assumed that the deletion operation has higher precedence than insertions, if both are possible at a moment. Given a word t, called a context, and the single contextual insertion is performed as follows. For each occurrence of the context t in the given string y, the word t is replaced as txt. In practice, this can be achieved by a replicative transposition process. Similarly, given a pair of words (u, v), called a context, the (u, v)-contextual deletion removes the word in between u and v. Finally, the power of this system and some closure properties are studied.     

THE STATESMAN WHO COULD NOT READ HIS OWN MAIL

An enciphered enclosure missing from a 1678 letter is rediscovered and cryptanalyzed after more than 300 years. It contains information intended for the leading statesman of England at the time which, despite his efforts, he was never able to read.     

基于闭环控制的自动转位系统设计

针对某型设备自动转位系统控制及测角精度需要,采用步进电机驱动、机械机构及光栅测角细分的方法,设计了一种基于步进电机闭环控制的自动转位系统。该系统通过步进电机驱动细分和转台机械细分达到了0.5″的转位分辨率,利用光栅测角的正切法细分达到了1″的测角。实验表明：该系统控制精度达到6″,满足了系统设计精度为5″左右的要求。     

1000kV同塔双回线路感应电压和电流的计算分析

同塔双回输电线路在一回运行、一回检修时,检修回路及地线中会产生感应电压、电流。使用EMTP仿真计算了1 000 kV交流特高压同塔双回输电线路1回线路停运检修时,运行回路对检修回路和地线的感应电压、电流,并对输电线路和地线上的感应电压、电流的影响因素进行了分析。可为特高压同塔双回线路检修及带电作业等方面的工作提供参照依据。     

1000kV交流紧凑型输电线路潜供电流和恢复电压计算分析

1000kV特高压紧凑型线路潜供电流和恢复电压较特高压示范工程大,会降低单相重合闸的成功率,影响特高压系统的安全稳定性。为此,阐述了特高压紧凑型线路潜供电流和恢复电压的特点,基于两个500kV区域电网之间采用特高压紧凑型线路作为联络线的系统,用EMTP程序计算分析了紧凑型线路潜供电流和恢复电压的影响因素。研究结果表明：...     

彩超顺序分段分析法对矫正型大动脉转位的诊断价值

目的：探讨彩色多普勒超声心动图顺序分段分析法对矫正型大动脉转位（CTGA）的诊断价值。方法对11例 CTGA 患者采用彩色多普勒超声心动图顺序分段分析法判定心脏位置、连接关系及心内结构、功能和血流信号的变化。结果11例 CTGA 患者中,彩色多普勒超声心动图顺序分段分析法对 CTGA 的诊断符合率达100．0％（11/11）。SLL 型（心脏位置正常）9例（81．8％）,IDD 型（镜面右位心）2例（18．1％）。SLL 型合并室间隔缺损9例、合并肺动脉狭窄7例和合并解剖三尖瓣中度反流8例;合并房间隔缺损4例,其中 SLL 型3例,IDD 型1例;IDD 型合并室间隔缺损、肺动脉狭窄和解剖三尖瓣中度反流1例。均经手术证实。结论CTGA 的超声表现错综复杂,心房与心室连接不一致和心室与大动脉连接不一致是诊断 CTGA 的关键,运用其特征性能有效提高诊断符合率,部分替代心血管造影等检查,为心胸外科提供重要的诊断依据。