With the goal of minimizing the enciphered data redundancy R , we first make a feasibility analysis on the PKCS which is based on the PR method, indicating its difficulties in real ap...With the goal of minimizing the enciphered data redundancy R , we first make a feasibility analysis on the PKCS which is based on the PR method, indicating its difficulties in real applications. Then we generalize the method to such a case that an arbitrary number system can be utilized in the system. We form some conditions that should be satisfied when we want to create security keys, to encipher plaintexts or to decipher cryptograms. Finally, a qualitative analysis is made on the improved PR method with the results that the data redundancy R of enciphered text for the improved PR method is far smaller than that of the primitive PR method and its enciphering and deciphering procedures are accordingly sped up. Moreover, the security of the new scheme is by no means worse than that of the old one.展开更多
Uneven roads surface can be observed on bituminous pavements. This is due to moving loads and climate conditions. If the observed deformations exceed the elastic limit, important damages can occur, so new materials ar...Uneven roads surface can be observed on bituminous pavements. This is due to moving loads and climate conditions. If the observed deformations exceed the elastic limit, important damages can occur, so new materials are used to improve the stiffness modulus of bituminous mixtures. To achieve this, a modified bituminous concrete by addition of the PR PLAST Sahara (produced by PR industries and PLAST for Plastic) mainly used in arid region has been studied. The use of this additive at various percentages 0.1, 0.3, 0.6 and 0.9 by weight of bituminous concrete has been investigated to determine its stiffness modulus. An experimental design using the Taguchi tables has been elaborated to reduce the number of tests. Marshall and NAT (Nottingham asphalt tester) tests have been carried out, and a mathematical model of the stiffness modulus has been proposed.展开更多
为解决电气化铁路牵引供电系统中三相网侧谐波、无功和负序等电能质量问题,同时满足电气化铁路补偿容量大的要求,提出了采用并联型铁路功率调节器(railway static power conditioner,RPC)配合降压变压器的综合补偿方案,具体研究了并联型...为解决电气化铁路牵引供电系统中三相网侧谐波、无功和负序等电能质量问题,同时满足电气化铁路补偿容量大的要求,提出了采用并联型铁路功率调节器(railway static power conditioner,RPC)配合降压变压器的综合补偿方案,具体研究了并联型RPC的控制策略并进行了仿真分析。提出了对RPC的指令电流检测采用平衡补偿电流检测法,对RPC的补偿电流控制采用基于比例谐振(proportion resonance,PR)控制器的三角波比较控制方式,同时将载波相移(carrier phase shift,CPS)技术应用于RPC的控制。最后,利用MATLAB/Simulink搭建了由2个RPC并联构成的补偿方案的仿真模型。仿真结果表明:RPC投入运行后,三相网侧电流为与电网电压同相位的三相正弦对称电流,只含有开关频率整数倍次的高次谐波;通过进一步采用CPS技术,开关频率奇数倍次的高次谐波被有效滤除,三相网侧电流总谐波畸变率由8.04%降低为2.24%。仿真结果验证了并联型RPC在解决牵引供电系统中三相网侧电流谐波、无功和负序等电能质量问题方面的可行性与优越性,为并联型RPC的工程应用提供了有价值的参考。展开更多
文摘With the goal of minimizing the enciphered data redundancy R , we first make a feasibility analysis on the PKCS which is based on the PR method, indicating its difficulties in real applications. Then we generalize the method to such a case that an arbitrary number system can be utilized in the system. We form some conditions that should be satisfied when we want to create security keys, to encipher plaintexts or to decipher cryptograms. Finally, a qualitative analysis is made on the improved PR method with the results that the data redundancy R of enciphered text for the improved PR method is far smaller than that of the primitive PR method and its enciphering and deciphering procedures are accordingly sped up. Moreover, the security of the new scheme is by no means worse than that of the old one.
文摘Uneven roads surface can be observed on bituminous pavements. This is due to moving loads and climate conditions. If the observed deformations exceed the elastic limit, important damages can occur, so new materials are used to improve the stiffness modulus of bituminous mixtures. To achieve this, a modified bituminous concrete by addition of the PR PLAST Sahara (produced by PR industries and PLAST for Plastic) mainly used in arid region has been studied. The use of this additive at various percentages 0.1, 0.3, 0.6 and 0.9 by weight of bituminous concrete has been investigated to determine its stiffness modulus. An experimental design using the Taguchi tables has been elaborated to reduce the number of tests. Marshall and NAT (Nottingham asphalt tester) tests have been carried out, and a mathematical model of the stiffness modulus has been proposed.