Secure Polar Coding for the Primitive Relay Wiretap Channel

With the emergence of wireless networks, cooperation for secrecy is recognized as an attractive way to establish secure communications. Departing from cryptographic techniques, secrecy can be provided by exploiting the wireless channel characteristics; that is, some error-correcting codes besides reliability have been shown to achieve information-theoretic security. In this paper, we propose a polar-coding-based technique for the primitive relay wiretap channel and show that this technique is suitable to provide information-theoretic security. Specifically, we integrate at the relay an additional functionality, which allows it to smartly decide whether it will cooperate or not based on the decoding detector result. In the case of cooperation, the relay operates in a decode-and-forward mode and assists the communication by transmitting a complementary message to the destination in order to correctly decode the initial source’s message. Otherwise, the communication is completed with direct transmission from source to the destination. Finally, we first prove that the proposed encoding scheme achieves weak secrecy, then, in order to overcome the obstacle of misaligned bits, we implement a double-chaining construction, which achieves strong secrecy.     

The Uniformly 3-Homogeneous Subsets of PGL(2, q)

We use the character-table of PGL(2, q) to determine the subsets of that group acting uniformly 3-homogeneously on the projective line.     

Interlaminar fracture and low-velocity impact of carbon/epoxy composite materials

The interlaminar fracture and the low-velocity impact behavior of carbon/epoxy composite materials have been studied using width-tapered double cantilever beam (WTDCB), end-notched flexure (ENF), and Boeing impact specimens. The objectives of this research are to determine the essential parameters governing interlaminar fracture and damage of realistic laminated composites and to characterize a correlation between the critical strain energy release rates measured by interlaminar fracture and by low-velocity impact tests. The geometry and the lay-up sequence of specimens are designed to probe various conditions such as the skewness parameter, beam volume, and test fixture. The effect of interfacial ply orientations and crack propagation directions on interlaminar fracture toughness and the effect of ply orientations and thickness on impact behavior are examined. The critical strain energy release rate was calculated from the respective tests: in the interlaminar fracture test, the compliance method and linear beam theory are used; the residual energy calculated from the impact test and the total delamination area estimated by ultrasonic inspection are used in the low-velocity impact test. Results show that the critical strain energy release rate is affected mainly by ply orientations. The critical strain energy release rate measured by the low-velocity impact test lies between the mode I and mode II critical strain energy release rates obtained by the interlaminar fracture test. Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000). Published in Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 195–214, March–April, 2000.     

Large deflection analysis of the moderately thick general theta ply laminated plates on nonlinear elastic foundation with various boundary conditions

This paper presents a powerful method i.e. the kinetic Dynamic Relaxation for analyzing general theta ply laminated plates, resting on nonlinear elastic foundation with different boundary conditions. Comprehensive comparison and parametric studies prove accuracy and efficiency of the proposed approach with interesting specifications such as fully vector calculations, independency to configuration, situation and angle of plies so that general theta ply laminated plate with simultaneous coupling between membrane, bending and shear strains could be analyzed as simple as analyzing of symmetric cross ply plate. Moreover, the proposed technique could simply satisfy complicated boundary conditions such as free and movable edges.     

Generic security analysis framework for quantum secure direct communication

Quantum secure direct communication provides a direct means of conveying secret information via quantum states among legitimate users. The past two decades have witnessed its great strides both theoretically and experimentally. However, the security analysis of it still stays in its infant. Some practical problems in this field to be solved urgently, such as detector efficiency mismatch, side-channel effect and source imperfection, are propelling the birth of a more impeccable solution. In this paper, we establish a new framework of the security analysis driven by numerics where all the practical problems may be taken into account naturally. We apply this framework to several variations of the DL04 protocol considering real-world experimental conditions. Also, we propose two optimizing methods to process the numerical part of the framework so as to meet different requirements in practice. With these properties considered, we predict the robust framework would open up a broad avenue of the development in the field.     

超声速复合材料层合壁板结构的颤振特性分析

对超声速复合材料壁板结构的气动弹性颠振特性进行了分析研究.采用Hamilton原理和假设模态法建立结构的运动方程,采用活塞理论模拟超声速非定常气动力,通过求解本征值问题,得到结构的固有频率和阻尼比等物理量.数值计算了结构无量纲固有频率随气动压力的变化曲线,确定颤振临界气动压力(或颤振速度),并计算了结构的受迫振动时间响应历程曲线,分析比较了不同纤维铺设方式和不同铺设角度对超声速复合材料壁板结构气动弹性稳定性的影响.本文研究结果对超声速飞行器壁板结构的气动弹性稳定性分析和设计具有理论参考价值.     

基于符合测量机制的光学信息保护

提出了一种基于符合测量机制的光学信息保护方法.发送方选择一定的载波信号将待传输的信息加载在待成像的物体上,接收方进行符合测量,并根据双方之间的协议从测量得到的物体的空间分布信息中解密出信息.计算机仿真结果表明,该方案能够成功实现信息的保护,具有良好的安全性.     

复合材料水翼水动力与结构强度特性数值研究

针对复合材料水翼存在的流固耦合求解问题,结合其自身特有属性,对复合材料水翼结构变形特性进行了数值仿真计算研究.研究建立了复合材料水翼流固耦合数值计算模型,并将数值计算结果与Zarruk等的实验结果进行对比,验证模型的正确性,得出复合材料水翼尖端扭转角随雷诺数的增加而增加的研究结论.基于数值计算模型,系统地研究了不同铺层角对复合材料水翼水动力特性及强度特性的影响,结果表明:不同铺层角复合材料水翼的尖端扭转角,随铺层角的增大而减小,而其尖端位移量随铺层角的增大先减小后增大.为了削弱工程常数的影响对复合材料水翼变形的影响,研究提出了无量纲扭转角和无量纲位移量,进一步探究复合材料水翼结构的弯扭耦合作用对其变形特性的影响.最后利用蔡$\!$-$\!$-$\!$吴失效准则进行复合材料水翼强度特性的判断和分析,结果表明:不同铺层角复合材料水翼的蔡$\!$-$\!$-$\!$吴系数,随铺层角的增大呈现先减小后增大的趋势,其中0$^\circ$铺层时的复合材料水翼蔡$\!$-$\!$-$\!$吴系数最小,50$^\circ$铺层时的复合材料水翼的蔡$\!$-$\!$-$\!$吴系数最大.      

混沌同步在语音保密通讯中的应用

本文利用APD混沌同步控制技术,实现了对语音信号的双重保密,并通过计算机模拟了信号加密解密的全过程。本文还讨论了加密信号在传输过程中受到干扰时,对解密信号的质量产生的影响,同时提供了相应的抗干扰措施,该语音保密方法简单实用,安全可靠,有较好的应用前景。     

Stress analysis of cross-ply composite laminates with transverse cracks

A boundary-discontinuous Fourier expansion method to analyze the displacements and stresses in cross-ply composite laminates with transverse cracks is presented. The governing equations of the problem are derived on the basis of the generalized plane strain assumption and two-dimensional equations of elasticity. By employing the boundary-discontinuous Fourier expansion method, the governing equations in the form of coupled high-order ODEs are transformed to a set of systems of linear algebraic equations. The method is used to obtain solutions for which published results can be found for comparisons. Compared with the conventional numerical methods for solving coupled high-order ODEs, the method presented is more efficient. Further parametric studies are carried out for cracked laminates with various geometric and material properties. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 6, pp. 795–826, November–December, 2008.