Chosen plaintext attack on a cryptosystem with discretized skew tent map

An encryption system with discretized skew tent map has been proposed recently by N. Masuda . However, there is a fundamental weakness with this chaotic cryptographic scheme. In this paper, a chosen plaintext attack requiring only two plaintexts is proposed. An improved version of this attack that narrows the key space need to be searched is also suggested. The test results demonstrate that this encryption cryptosystem is easily broken under the proposed chosen plaintext attack.     

A new scheme for bidirectional WDM-PON using upstream and downstream channels generated by optical carrier suppression and separation technique

We propose a new bidirectional dense wavelength-division-multiplexing (DWDM)-based passive optical network using optical carrier suppression and separation technique to generate both upstream and downstream wavelength channels from a single laser. Thirty-two DWDM channels have been generated, and symmetric 10-Gb/s data transmission of a wavelength pair has been demonstrated.     

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川东地区石炭系气藏的气水界面主要分布在两个范围内，一是潜伏构造气藏的气水界面海拔较深，一般为-3800～-4700m；另一是主体构造气藏的较浅，一般为-1600～-2600m。各构造带之间相邻的潜伏圈闭气藏往往受同一大向斜内的水域相隔，并在原始状态下相互维系了气水的压力平衡，因此同一向斜内某一构造的水井资料就可用于计算另一构造同一气藏的气水界面。基于这种认识，章根据同向斜域内相邻构造的水井资料计算卧龙河、双家坝、云和寨、高峰场、胡家坝等气田的原始气水界面，得到的气水界面与实际误差为-3～-18m。说明该方法在实际应用中可靠性较好，可节省钻井投资，缩短气田的评价周期。     

Nonlinear Thermal Analysis for Qing-Tibet Railway Embankments in Cold Regions

Heat convection in ballast mass in railway embankments is a problem of heat convection in porous media. In order to calculate the temperature distribution of the Qing-Tibet railway embankment from the governing equations used to study forced convection for incompressible fluids porous media, detailed finite-element formulas for heat convection in porous media are derived using Galerkin’s method. The temperature distributions on central lines of the traditional railway embankment, the ripped-rock embankment, and the ripped-rock revetment embankment that were constructed on July 15, 2002 have been analyzed and compared on July 15, October 15 in the 24th year after construction, and January 15 in the 25th year after construction under the climatic and geological conditions on the Qing-Tibet Railway. The calculated results indicate that the traditional railway embankment will raise the permafrost temperature under the embankment base and make the permafrost embankment thermally unstable. The ripped-rock embankment and the ripped-rock revetment embankment will reduce the permafrost temperature under the embankment base in cold regions, therefore maintaining the thermal stability of permafrost. However, the ripped-rock embankment needs more rock mass while the ripped-rock revetment embankment need less rock mass, and its construction cost is lower than that of the former. Therefore, it is highly recommended that the ripped-rock revetment embankment be used for the Qing-Tibet railway embankment structure in high temperature permafrost regions so that the permafrost embankment can be protected as much as possible.     

近年太钢烧结技术发展回顾与展望

近年来太钢由于烧结技术进步，烧结矿质量不断改善，固体燃耗降低，促进了高炉炉料结构的优化。为高炉技术经济指标提高奠定了基础。     

四坐标数控加工原理及算法研究

本文对四坐标数控加工原理和算法作了详细介绍，尤其对四坐标加工的刀轴矢量算法进行了研究，提出了用垂直于回转轴的平面与刀具运动方向和前导角形成的圆锥面求交，生成刀轴矢量的方法，该方法具有立意新颖、思路清晰，性能可靠，易于在微机上实现等特点，对复杂曲面零件的加工编程，具有重要的实用价值。     

贮存稳定的聚氨酯干式复合胶粘剂的研究

研制了一种具有高固含量、低粘度的干式复合用双组分聚氨酯胶粘剂，考察了聚酯多元醇，扩链剂丙三醇／乙二醇（摩尔比）、NCO／OH（摩尔比），双组分胶配比以及缓凝剂等因素对该胶粘剂性能的影响，并用红外光谱对胶的固化过程进行了表征。结果表明，该胶粘剂具有较高的粘接强度，优良的低温流动性和贮存稳定性。     

机载雷达空时二维信号处理自适应权值训练的距离分段递推算法

本文针对机载预警雷达的杂波环境，分析了杂波数据的非平稳性，由此提出在距离上分段实现空时二维自适应处理（STAP）的方法，并通过分析杂波于空间的距离来确定分段的方法。在同时考虑实时性和处理器性能的前提下，给出了一种自适应权值计算的递推算法。理论分析和计算机仿真结果均表明，本文提出的分段递推算法是有效的。