一类Feistel密码的线性分析

该文提出一种新的求取分组密码线性偏差上界的方法，特别适用于密钥线性作用的Feistel密码．该分析方法的思路是，首先对密码体制线性偏差进行严格的数学描述，分别给出密码线性偏差与轮函数F及S盒的线性偏差的数学关系；然后通过求取线性方程组最小重量解，确定密码线性偏差的上界．     

合成己二腈反应技术研究——(Ⅴ)己二腈工业反应过程模拟与反应器改造

对己二腈工业反应器提出了两釜串联带回流的模型,通过模拟计算得出模型的级间返混系数 f=6的结论。该模型能较好地预测工业反应器中物料组分浓度变化和气、液两相的流动特性;指出了现工业反应器的鼓泡中和段体积偏小是造成己二酸浓度偏高的关键;提出了可以通过增加串连一个鼓泡预反应段的改造方案,能有效地降低己二酸的浓度,从7%降至4%左右,从而能较好地减缓腐蚀和结焦。     

Cd-ZSM-5沸石催化剂的制备、表征和芳构化催化性能

采用离子交换、浸渍和混合三种方法制备镉改性ZSM-5沸石催化剂,考察了改性方法和镉含量对催化剂的表面酸性和Cd状态以及芳构化性能的影响。结果表明,加入镉降低了B酸性,Cd~(2+)与沸石结合形成了L_(1612)酸中心,其生成量取决于改性方法和Cd含量,并与芳构化活性提高有直接关系。     

氧化铝陶瓷缺口件循环疲劳及断裂机理

用实验方法研究了Ａｌ＿２Ｏ＿３陶瓷缺口试件在循环载荷作用下的疲劳寿命。结果表明，缺口导致的应力集中效应显著降低了循环疲劳寿命；若用缺口根部最大应力为应力水平，则不同缺口半径陶瓷试件具有相同疲劳断裂规律，说明陶瓷材料的疲劳集中系数和理论应力集中系数相同。本文还分析讨论了陶瓷材料的循环疲劳寿命表达式和循环疲劳断裂机理。     

An algebraic theory of object-oriented systems

The paper presents an algebraic specification of net objects. By net objects we mean those that are defined in object-oriented paradigms and those defined with nested relations in complex database models. An algebraic specification is set up that involves structures of net objects, accesses of net objects, and some features of object-oriented programming, such as multiple inheritance and polymorphism. Objects and their relationships are then characterized formally in the modeling, which utilizes the hierarchical approach in the algebraic theory of abstract data types, and is further developed by adding mechanisms from existing object systems. Categories of net objects are presented with the properties of accesses among them     

聚氧乙烯油酸酯的合成与物性

论述了合成聚氧乙烯油酸酯的较佳反应条件,探讨了不同EO加成数的聚氧乙烯油酸脂的表面物性规律。     

COATES GRAPH APPROACH FOR GENERATING SYMBOLIC NETWORK FUNCTION

In this paper, symbolic code matrix ,constant matrix and count matrix are defined .The first twomatrices are used to describe the elemental expression of augmented matrix and the nede admittance equa-tion is thus obtained. The third matrix is used to obtain the incoming degree matrix, and according to thematrix all the 1- factors of the Coates graph are given. By using the data code, the determinant is expandedand the same items in the expansion are merged. Thus the symbolic network function in which no term can-cellation occurs is generated.     

新疆伊犁托海水电站拱坝坝体变形监测分析

根据托海拱坝5号坝段、7号坝段例垂线实测资料分析，说明了新疆寒冷地区坝体采取聚胺脂喷涂施工措施后对坝体变形的影响，以及右坝肩渗漏对右坝肩岩体的影响，分析结果为托海水电站通过国家电力公司大坝安全监察中心大坝安全首次定检提供了科学依据。     

薄板坯连铸工艺液芯压下的有限元分析

简要介绍世界几种主要薄板坯连铸工艺。着重叙述应用大型通用商业软件MSC.MARC。模拟液芯压下时铸坯的变形，确定最佳压下方案的有限元分析，液芯压下应该在结晶器出口处及二冷区扇形段开始部分进行，这样能减小铸坯的应变。     

LDPC-based space-time coded OFDM systems over correlated fadingchannels: Performance analysis and receiver design

We consider a space-time coded (STC) orthogonal frequency-division multiplexing (OFDM) system with multiple transmitter and receiver antennas over correlated frequency- and time-selective fading channels. It is shown that the product of the time-selectivity order and the frequency-selectivity order is a key parameter to characterize the outage capacity of the correlated fading channel. It is also observed that STCs with large effective lengths and ideal built-in interleavers are more effective in exploiting the natural diversity in multiple-antenna correlated fading channels. We then propose a low-density parity-check (LDPC)-code-based STC-OFDM system. Compared with the conventional space-time trellis code (STTC), the LDPC-based STC can significantly improve the system performance by exploiting both the spatial diversity and the selective-fading diversity in wireless channels. Compared with the previously proposed turbo-code-based STC scheme, LDPC-based STC exhibits lower receiver complexity and more flexible scalability. We also consider receiver design for LDPC-based STC-OFDM systems in unknown fast fading channels and propose a novel turbo receiver employing a maximum a posteriori expectation-maximization (MAP-EM) demodulator and a soft LDPC decoder, which can significantly reduce the error floor in fast fading channels with a modest computational complexity. With such a turbo receiver, the proposed LDPC-based STC-OFDM system is a promising solution to highly efficient data transmission over selective-fading mobile wireless channels