并发程序执行的一种粒度分析方法

文章讨论基于交替计算模式的并发程序执行行为的可信性问题。通过比较共享变量程序的交替计算与实际重叠执行，对并发程序的执行过程进行粒度分析──首先提出一种粒度细化、求精方法，限制单个原子转换包含的临界事件数目；继而引入一种限制临界引用（ＬＣＲ）条件，进一步限制每一与语句相关的转换至多执行一次临界引用；对任一程序，通过转换算法将其转化为与之等价的ＬＣＲ程序，且ＬＲ程序的交替计算结果与实际的重叠执行结果是一致的。     

DVB系统原理与Systemview仿真实现

数字视频广播DVB（Digital Video Broadcasting）标准是欧洲数字电视的传输标准,它包括数字信源压缩编码、节目数据流的统计复用、信道纠错编码、调制等数字传输链路各相关环节所采用的技术及接口标准。本文在介绍DVB技术原理的基础上,深入探讨了DVB系统的构成及调制、解调原理,并在Systemview下对该系统进行了完整仿真。通过信号观察窗对比信号波形发现,输入输出基本一致,说明该系统在通常信噪比条件下可以满足可靠传输的基本要求,达到了预期目的,证明了系统的可靠性。     

Strategic attack on the shrinking generator

The shrinking generator is a simple keystream generator with applications in stream ciphers, which is still considered as a secure generator. This work shows that, in order to cryptanalyze it, fewer intercepted bits than indicated by the linear complexity are necessary. Indeed, whereas the linear complexity of shrunken sequences is between A⋅2^(S−2)$A\cdot 2^{(S-2)}$ and A⋅2^(S−1)$A\cdot 2^{(S-1)}$, we claim that the initial states of both component registers are easily computed with fewer than A⋅S$A\cdot S$ shrunken bits located at particular positions. Such a result is proven thanks to the definition of shrunken sequences as interleaved sequences. Consequently, it is conjectured that this statement can be extended to all interleaved sequences. Furthermore, this paper confirms that certain bits of the interleaved sequences have a greater strategic importance than others, which must be considered as a proof of weakness of interleaved generators.     

Visual Studio.NET功能强大的数组类System.Array

本文系统介绍了System．Array类基本特点和常见用法，并通过一系列实例就在Visual Basic．NET中如何创建索引基于非零的数组、复制数组、数组元素的排序、数组元素的删除、复制与移动、搜索特定元素以及交错数组等问题进行了条分缕析。     

基于改进交错组卷积的眼底硬性渗出物自动分割

在临床诊断中,眼底硬性渗出物的检测结果是判断糖尿病视网膜病变程度的重要参考。现有眼底硬性渗出物检测模型通过加深网络层数以有效分割硬性渗出物的病灶特征,但是容易产生冗余卷积单元且难以准确提取全部有效特征,影响整体分割性能。提出一种融合交错组卷积与双重注意力机制的眼底硬性渗出物自动分割模型。利用改进的交错组卷积模块代替原始U型网络编码部分,在减少分割模型参数的同时提取更丰富的病灶特征。同时通过位置注意力模块联系局部上下文信息,捕获更广泛的感受野以及更深层次的病灶特征,利用通道注意力模块增加提取关键特征的通道权重,提升重要特征的可辨别性。实验结果表明,该模型在e-Ophtha EX数据集上灵敏度、精确度和F-Score分别为91.43%、86.49%和87.32%,在DIARETDB1数据集上灵敏度、特异性和准确性分别达到97.83%、96.16%和97.51%,能够有效改善原始U型网络对眼底硬性渗出物的分割效果。     

SPWM控制的交叉反激变换器设计

设计的SPWM控制的交叉反激变换器,结合了交叉反激变换器的优点与SPWM响应速度快、稳定性高的特性,具有拓扑简单、输出纹波小、稳定性高、关断电压尖峰小等优点。介绍了SPWM波控制交叉反激电路输出互补实现直流正弦半波变换的原理;分析了DSP生成SPWM波的原理和方法;实验验证了设计的合理性不仅提高了电路的整体性能,且没有增加硬件电路设计的负担。     

MPPT controller for an interleaved boost dc–dc converter used in fuel cell electric vehicles

Fuel cell electric vehicle (FCEV) has recently attracted increasing research interest. This paper investigates the performances of MPPT-FC generators supplying electric vehicle power train through an interleaved boost DC/DC converter (IBC). The accent is made on forcing the FC generator to operate at its maximum power point by using perturb and observe (P&O) algorithm integrated to the IBC control. However, the MPPT-FC control creates rapid changes in the power output from the fuel cell, which cause serious life shortening, severe cell degradation, and decrease the system efficiency. To overcome these shortcomings, the control of air generation system was designed to improve the power quality and to prevent fuel starvation phenomenon during rapid power transitions. The work involves the modeling and the simulation of the fuel cell power train in the vehicular application using the experimental data obtained in previous works. The experimental part of the proposed FCEV is based on a low-cost, low-power consumption microcontroller, which controls the IBC and performs the MPPT-FC operation. A microcontroller is used to measure the FC output power and to change the duty ratio of the IBC control signals.     

基于交错螺旋矩阵加密的自动信任协商模型

针对自动信任协商(ATN)中的敏感信息保护问题,提出了基于交错螺旋矩阵加密(ISME)的自动信任协商模型。此模型采用交错螺旋矩阵加密算法以及策略迁移法,对协商中出现的3种敏感信息进行保护。与传统的螺旋矩阵加密算法相比,交错螺旋矩阵加密算法增加了奇偶数位和三元组的概念。为了更好地应用所提模型,在该协商模型的证书中,引入了属性密钥标志位的概念,从而在二次加密时更有效地记录密钥所对应的加密敏感信息,同时列举了在协商模型中如何用加密函数对协商规则进行表示。为了提高所提模型协商成功率和效率,提出了0-1图策略校验算法。该算法利用图论中的有向图构造了6种基本命题分解规则,可以有效地确定由访问控制策略抽象而成的命题种类。之后为了证明在逻辑系统中此算法的语义概念与语法概念的等价性,进行了可靠性、完备性证明。仿真实验表明,该模型在20次协商中策略披露的平均条数比传统ATN模型少15.2条且协商成功率提高了21.7%而协商效率提高了3.6%。     

Interleaved soft-switched active-clamped L–L type current-fed half-bridge DC–DC converter for fuel cell applications

In this paper, an interleaved soft-switched active-clamped L–L type current-fed half-bridge isolated dc–dc converter has been proposed. The L–L type active-clamped current-fed converter is able to maintain zero-voltage switching (ZVS) of all switches for the complete operating range of wide fuel cell stack voltage variation at full load down to light load conditions. Active-clamped circuit absorbs the turn-off voltage spike across the switches. Half-bridge topology maintains higher efficiency due to lower conduction losses. Soft-switching permits higher switching frequency operation, reducing the size, weight and cost of the magnetic components. Interleaving of the two isolated converters is done using parallel input series output approach and phase-shifted modulation is adopted. It reduces the input current ripple at the fuel cell input, which is required in a fuel cell system and also reduces the output voltage ripples. In addition, the size of the magnetic/passive components, current rating of the switches and voltage ratings of the rectifier diodes are reduced.     

A family of high gain fuel cell front-end converters with low input current ripple for PEMFC power conditioning systems

Since the output voltage of the proton exchange membrane fuel cell (PEMFC) is relatively low and load-dependent, a high-performance fuel cell front-end converter is required to achieve boost and power regulation in PEMFC systems. In response, a novel family of high gain fuel cell front-end converters with low input current ripple is proposed. The proposed topologies can substantially improve the voltage gain through the expansion and combination of active switched-inductor networks and passive switched-capacitor units. The introduced interleaved parallel structure is convenient to limit the current ripple on the input side to prevent accelerated aging of fuel cells, which is another prominent advantage. Meanwhile, the converters can achieve the automatic current sharing between parallel inductors and the low voltage stress on active switches and diodes. In this paper, the fuel cell model and topology derivation of the high gain fuel cell front-end converters are first analyzed. Then, it further describes the operating mode and steady-state performance of converters under the inductor current continuous conduction mode. The comparison with other converters shows that this converter is suitable for connecting the PEMFC to the high voltage DC bus. Finally, a 200 W, 20/180 V converter prototype is implemented, and the simulation and experiment prove the theoretical correctness and validate the superior performances of the proposed converters.