石英玻璃中羟基的结构特征

研究了2类石英玻璃中羟基的结构特征及其释放方式。四极质谱显示石英玻璃受热释放出H2和H2O。用红外光谱和魔角旋转固态核磁共振(MASNMR)研究了石英玻璃中羟基的结构特征，结合电子自旋共振(ESR)分析了玻璃结构中E′心对1H NMR的影响。结果 表明：气相水解法合成的石英玻璃有带氢链的羟基、相邻羟基对和孤立羟基；氢气气氛下电熔石英玻璃包含与Si-H邻近的羟基、与E′心邻近的羟基、孤立羟基3种主要存在形式。     

大型企业集团的财务管理和会计管理

针对当前我国大型企业集团在财务管理中存在的主要问题,探讨了怎样正确处理集权和分权的关系及会计与财务职能的分设问题。     

M-群与内超可解群

M-群的一个著名的结果是：超可解群是M-群，沿着这一方向已有结果：可解外超可解群是M-群；极小非超可解群是M-群．证明了：内超可解群不一定是M-群，即验证了四次交错群A4是内超可解的M-群，而特殊线性群SL(2，3)是内超可解的非M-群：而且给出了内超可解群是M-群的一个充分条件：若G是内超可解群，Φ(G)是G的Frattini子群(即G的所有极大子群的交)。那么G／Φ(G)是M-群．注意到，在这一假设下，G／Φ(G)也是一个内超可解群．     

电力系统同调机群的识别方法

在对电力系统中同调机群的识别方法进行研究的同时，并对以往的各种同调机群的识别方法也进行了归纳总结，针对这些方法所存在的问题，给出了一种新的较为实用的同调机群识别方法。     

Uniform Distribution, Distance and Expectation Problems for Geometric Features Processing

Complex geometric features such as oriented points, lines or 3D frames are increasingly used in image processing and computer vision. However, processing these geometric features is far more difficult than processing points, and a number of paradoxes can arise. We establish in this article the basic mathematical framework required to avoid them and analyze more specifically three basic problems: (1) what is a random distribution of features, (2) how to define a distance between features, (3) and what is the “mean feature” of a number of feature measurements? We insist on the importance of an invariance hypothesis for these definitions relative to a group of transformations that models the different possible data acquisitions. We develop general methods to solve these three problems and illustrate them with 3D frame features under rigid transformations. The first problem has a direct application in the computation of the prior probability of a false match in classical model-based object recognition algorithms. We also present experimental results of the two other problems for the statistical analysis of anatomical features automatically extracted from 24 three-dimensional images of a single patient's head. These experiments successfully confirm the importance of the rigorous requirements presented in this article.     

Development of Downdrag on Piles and Pile Groups in Consolidating Soil

Development of pile settlement (downdrag) of piles constructed in consolidating soil may lead to serious pile foundation design problems. The investigation of downdrag has attracted far less attention than the study of dragload over the years. In this paper, several series of two-dimensional axisymmetric and three-dimensional numerical parametric analyses were conducted to study the behavior of single piles and piles in 3×3 and 5×5 pile groups in consolidating soil. Both elastic no-slip and elasto-plastic slip at the pile–soil interface were considered. For a single pile, the downdrag computed from the no-slip elastic analysis and from the analytical elastic solution was about 8–14 times larger than that computed from the elasto-plastic slip analysis. The softer the consolidating clay, the greater the difference between the no-slip elastic and the elasto-plastic slip analyses. For the 5×5 pile group at 2.5 diameter spacing, the maximum downdrag of the center, inner, and corner piles was, respectively, 63, 68, and 79% of the maximum downdrag of the single pile. The reduction of downdrag inside the pile group is attributed to the shielding effects on the inner piles by the outer piles. The relative reduction in downdrag (Wr) in the 5×5 pile group increases with an increase in the relative bearing stiffness ratio (Eb/Ec), depending on the pile location in the group. Compared with the relative reduction in dragload (Pr), Wr at the corner pile is less affected by the group interaction for a given surcharge load. This suggests that the use of sacrificing piles outside the pile group will be more effective on Pr than on Wr. Based on the three cases studied, the larger the number of piles in a group, the greater the shielding effects on Wr. Relatively speaking, Wr is more sensitive to the total number of piles than to the pile spacing within a pile group.     

Axial offset control of PWR nuclear reactor core using intelligent techniques

Improved load following capability is one of the main technical performances of advanced PWR (APWR). Controlling the nuclear reactor core during load following operation encounters some difficulties. These difficulties mainly arise from nuclear reactor core limitations in local power peaking, while the core is subject to large and sharp variation of local power density during transients. Axial offset (AO) is the parameter usually used to represent of core power peaking, in form of a practical parameter. This paper, proposes a new intelligent approach to AO control of PWR nuclear reactors core during load following operation. This method uses a neural network model of the core to predict the dynamic behavior of the core and a fuzzy critic based on the operator knowledge and experience for the purpose of decision-making during load following operations. Simulation results show that this method can use optimum control rod groups maneuver with variable overlapping and may improve the reactor load following capability.     

Optimal evaluation of generalized Euler angles with applications to control

Given two linearly independent matrices in so(3), Z₁ and Z₂, every rotation matrix, X_f∈SO(3), can be written as the product of alternate elements from the one-dimensional subgroups corresponding to Z₁ and Z₂, namely X_f=e^Z₁t₁e^Z₂t₂e^Z₁t₃?e^Z₁t_s. The parameters t_i, i=1,…,s are called Generalized Euler Angles. In this paper, the minimum number of factors required for the factorization of X_f∈SO(3), as a function of X_f, is evaluated. An algorithm is given to determine the generalized Euler angles, in the optimal factorization. The results can be applied to the bang-bang control, with minimum number of switches, of some classical and quantum systems.     

Numerical analysis of different ventilation schemes during the construction process of inclined tunnel groups at the Changheba Hydropower Station,China

During the excavation process of underground caverns, the rational selection of the ventilation scheme is very important for the safety and health of construction workers. The flood discharge tunnel groups at the Changheba Hydropower Station are selected as a case to study the design of ventilation schemes in inclined tunnel groups; these groups are characterized by a gradient of approximately 10% and a complex intersecting relationship among the tunnels. The Computational Fluid Dynamics (CFD) method is used to simulate the fluid dynamics in tunnel groups when different ventilation schemes are employed. Four ventilation schemes with the same duct at different positions along the transverse section are formulated, and the scheme approaching the right side with most of the construction adits is adopted in engineering after a comparative analysis, as it offers a well-distributed velocity field and sufficient security distance. The study reveals that flow vortices appear in the tunnels with a long axis length ranging from 5 m to 20 m; the observation that the flow velocity on the transverse sections is away from the heading face indicates that a low-velocity area is always present in the vicinity of an air duct, and the security distance on the upstream side is 60% shorter than on the downstream side with the same air-blower when the tunnels have a 10% gradient. In addition, when the excavation distance rises 200 m, the ventilation condition in the tunnels, especially in the areas around tunnel intersections, is greatly improved by the completion of pilot tunnels and shafts in advance.     

A RAPID YES-NO COMPUTER-AIDED COMMUNICATOR

Abstract

When attacking the German Enigma cipher machine during the 1930s, the Polish mathematician Marian Rejewski developed a catalog of disjoint cycles of permutations generated by Enigma indicators. By comparing patterns that resulted from message indicators with his catalog, Rejewski was able to determine the ground settings. Well, not quite—the mapping from the disjoint cycles to the ground settings is not one-to-one. Rejewski's catalog no longer exists. This article reports on the output of a program that “recreates” the catalog and answers the question “How far from being one-to-one is the mapping?”