基于PD控制的航天飞行器控制系统的设计与实现

当前的飞行器控制系统在运行过程中容易受到噪声因素的干扰,对飞行器的控制存在滞后性和片面性,无法直观描述飞行器的运行状态,设计并实现了一种抗干扰能力强的航天飞行器控制系统,给出了无刷直流电机、电源电路、无线通信模块以及RS-232接口的硬件设计原理,给出了系统主控中心的人机交互界面组成;通过PD算法运算出不同电机的调整量,按照运算出的调整量控制电机的PCA模块,进而控制飞行器电机的转速,调整飞行器的姿态,克服干扰;实验结果说明,该种系统可对飞行器的各种飞行攻角进行准确的控制,该种系统的控制效率参数优于传统系统。     

Cryptanalyzing a novel image fusion encryption algorithm based on DNA sequence operation and hyper-chaotic system

Recently, an image fusion encryption algorithm [Optik 124 (18) (2013) 3596–3600] was proposed based on DNA sequence operation and hyper-chaotic system. The security of this algorithm depends mainly on both five keys as the initial conditions of hyper-chaotic system and a key image. In this paper, we cryptanalyze the algorithm and find that two chaotic keystream determined by the five keys keep unchanged for different image encryption processes. The two chaotic keystream can be revealed and the computational complexity is approximately O(mn), where m and n represent the height and width, respectively. In addition, the key image needs to be changed for each encryption. Finally, experimental results also verify our idea.     

AFRA: Argumentation framework with recursive attacks

The issue of representing attacks to attacks in argumentation is receiving an increasing attention as a useful conceptual modelling tool in several contexts. In this paper we present AFRA, a formalism encompassing unlimited recursive attacks within argumentation frameworks. AFRA satisfies the basic requirements of definition simplicity and rigorous compatibility with Dung’s theory of argumentation. This paper provides a complete development of the AFRA formalism complemented by illustrative examples and a detailed comparison with other recursive attack formalizations.     

代数免疫度为1的布尔函数

布尔函数的代数免疫度是在流密码的代数攻击中所产生的重要概念.研究了代数免疫度为1的布尔函数,得到的主要结果有:对代数免疫度为1的布尔函数给出了一个谱刻画,给出了其个数的精确计数公式,最后给出了此类函数的非线性度的紧的上界.     

水下高速射弹超空泡运动建模与仿真

建立并简化了水下高速射弹动力学和运动学模型。基于空泡模型假设和空泡截面独立扩张原理,确定了空化数与速度、深度的耦合计算关系;定义了水下射弹尾翼穿刺前的临界空化数;对水下高速射弹弹道特性进行了仿真研究。仿真计算结果表明：水下射弹有效射程受初始入射角影响较大;随着初始入射角的增大,有效射程逐渐减小;提升初速度可以带来有效射程的增大,但增幅效果不显著,在满足预定指标条件下应合理选择初速度;初始攻角对射弹弹道散布影响较大,初始角速度对其影响很小,但较大的初始角速度会带来明显的攻角变化。     

Dramatic substituent effects on the mechanisms of nucleophilic attack on Se—S bridges

The reactions of XSeSX, XSeSY, and YSeSX (X, Y = CH₃, NH₂, OH, F) with F^? and CN^? nucleophiles have been investigated by means of B3PW91/6‐311+G(2df,p) and G4 calculations. In systems where the two substituents are not identical (XSeSY), the more stable of the two possible isomers corresponds to those in which the most electronegative substituent is attached to Se. Nucleophilic attack takes place at Se, independent of the nature of the nucleophile, with the only exception being XSeSF (X = CH₃, NH₂, OH), in which case the attack occurs at S. In agreement with recent results for disulfide and diselenide linkages, the mechanisms leading to Se—S bond cleavage are not always the more favorable ones because for highly electronegative substituents the most favorable process is fission of the chalcogen‐substituent bond. These dissimilarities in the observed reactivity pattern as a function of the electronegativity of the substituents are due to the fact that the σ‐type Se—S antibonding orbital, which for low‐electronegative substituents is the lowest unnoccupied molecular orbital (LUMO), becomes strongly destabilized when the electronegativity of the substituent increases, and is replaced by an antibonding π‐type Se‐X (or S‐X) orbital. In contrast, however, with what has been found for disulfide and diselenide derivatives, the observed reactivity does not change with the nature of the nucleophile. The activation strain model provides interesting insight into these processes, showing that in most cases the activation barriers are the consequence of subtle differences in the strain or in the interaction energies. © 2013 Wiley Periodicals, Inc.     

REACTION OF (2-BENZOTHIAZOLYL)-SULFENAMIDES WITH P-CONTAINING REAGENTS

Abstract

The title reaction was investigated to find that only substitution reaction on amino group occurred when (2-benzothiazolyl)sulfenamides 1 reacted with P(NR₂,)₃, whereas the treatment of 1 with (RO)P(NR₂,)₂, gave derivatives of phosphorodiarnidothioic acid together with 2-alkylthiobenzothiazole and its isomer in addition to substitution products, and no substitution products obtained when N-substituted analogues of 1 were treated similarly.     

基于弱相干光的实际QKD系统的安全性研究

实际量子密钥分发系统使用的单光子源主要是由弱激光脉冲经衰减得到。它不是理想单光子源而是服从泊松分布的准单光子源。每个非空光脉冲中包含多光子的概率不为零,强大的窃听者可利用此获得一些关于最终密钥的信息。因此,有必要研究实际QKD系统的安全性。采用对多光子进行分束窃听、单光子最佳攻击相结合的方案,用Shannon信息理论分析了基于弱相干光的实际QKD系统的安全性。研究结果表明实际QKD系统对于分束窃听和最佳攻击是安全的,并给出合法通信双方在该攻击方案下所容忍的误码率上限。     

进口预旋对离心叶轮气动性能影响机理的研究

将理论推导和数值模拟相结合,对典型离心压缩机Eckardt叶轮流场进行分析,探讨了不同进气预旋对叶轮气动性能的影响;从叶片进口攻角、叶尖相对马赫数和流向压力变化的角度,阐述了预旋对内部流动以及气动性能的影响机理.结果表明:预旋角对进口攻角和叶尖相对马赫数同时产生显著影响,正预旋会降低进口来流的攻角及相对马赫数,使叶片前...     

EQUIVALENT MODEL OF EXPANSION OF CEMENT MORTAR UNDER SULPHATE EROSION

The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods. First, cement mortars are fabricated with the ratio of water to cement of 0.4, 0.6, and 0.8. Secondly, the expansion of specimen immerged in sulphate solution is measured at different times. Thirdly, a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method. In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account. Finally, the numerical calculation is results indicate that the model perfectly describes performed. The numerical and experimental the expansion of the cement mortar.