Influence of water and ammonia on hydrotreating catalysts and activity for tetralin hydrogenation

The effects of H₂O and NH₃ on the kinetics of the liquid phase hydrogenation of tetralin to decalin at 6.9 MPa and 330°C over commercial P---Ni---Mo/alumina catalysts in the presence of H₂S have been investigated. H₂O functioned as a mild kinetic inhibitor to an extent sensitive to the H₂S level. Quasi in situ XPS was used to investigate the catalyst structure after exposure to H₂0/H₂S.     

多面体含能材料的爆速和爆压预估

当采用R-P经验方法预估多硝基笼状化合物最大理论密度下爆速和爆压时,需要修正F因子中与分子结构有关的A/3项,使F因子包含有来自笼状分子高晶体密度和分子内部高张力能的贡献。与K-J方法相比,改进R-P方法既保持了原式的优点,又使预估结果获得明显改善。把K-J方法预估结果作为基础数据,利用改进R-P方法估算25种多硝基笼状化合物的爆速和爆压,结果表明该方法的相对误差分别为±1.9％和±5.2％。而用R-P方法时,预估爆速和爆压的相对误差分别为±14.0％和±21.4％。     

Genetic algorithms for symbolic clustering

This paper introduces a novel methodology for clustering of symbolic objects by making use of Genetic Algorithms (GAs). GAs are a family of computational models inspired by evolution. These algorithms encode potential solutions to specific problems on simple chromosome-like data structures and apply recombination operators to these structures so as to preserve critical information. A new type of representation for chromosome structure is presented here along with a new method for mutation. The efficacy of the proposed method is examined by application to numeric data of known number of classes and also to assertion type of symbolic objects drawn from the domain of fat oil, microcomputers, microprocessors and botany. The validity of the clusters obtained is examined.     

Research in object-oriented manufacturing simulations:an assessment of the state of the art

Object-oriented programming (OOP) has been revolutionizing software development and maintenance. When applied to simulation of manufacturing systems, OOP also provides an opportunity for developing new ways of thinking and modeling. In this paper, we identify existing large-scale, persistent OOP-based research efforts focusing on manufacturing system simulation, and present an integrating framework for discussing the associated modeling abstractions, implementation strategies, common themes, and distinctive features. The goal is to identify the fundamental research and application issues, assess the current state of the art, and identify key research needs.     

A hybrid technique of modeling of cracks using displacement discontinuity and direct boundary element method

A hybrid technique to model two dimensional fracture problems which makes use of displacement discontinuity and direct boundary element method is presented. Direct boundary element method is used to model the finite domain of the body, while displacement discontinuity elements are utilized to represent the cracks. Thus the advantages of the component methods are effectively combined. This method has been implemented in a computer program and numerical results which show the accuracy of the present method are presented. The cases of bodies containing edge cracks as well as multiple cracks are considered. A direct method and an iterative technique are described. The present hybrid method is most suitable for modeling problems involving crack propagation.     

On GID-Testable Two-Dimensional Iterative Arrays

A new approach is presented for easily testable two-dimensional iterative arrays.It is an improvement of GI-testability (Group Identical testability)and is referred to as GID-testability (Group Identical and Different testability).In a GID-testable two-dimensional array,the primary x and y outputs are organized into groups and every group has more than one output.This is similar to the GI-testable arrays.However,GID-testability not only ensures that identical test responses can be obtained from every output in the same group when an array is fault free,but also ensures that at least one output has different test responses (from the other outputs in a group)when a cell in the array is faulty.Therefore,all faults can be detected under the assumption of a single faulty cell model.It is proved that an arbitrary two-dimensional iterative array is GID-testable if seven x-states and seven y-states are added to the original flow table of the basic cell of the array.GID-testability simplifies the response verification of built-in-self-testing in a way similar to PI-and GI-testability^[6-9].Therefore,it is suitable for BIST design.     

Diffusion-controlled growth in ternary systems

Diffusion-controlled growth of particles, dendrites, and plates in infinite media is examined for ternary systems. The growth kinetics associated with planar, cylindrical, and spherical particles are shown to be limiting cases of a more complete analysis (also presented) for shape-preserving growth. The theory is applied to the growth of allotriomorphic ferrite from austenite in ternary Fe-C-X steels, where X represents a substitutional alloying element. Numerical results are given, the analysis relying on the ability to predict multicomponent phase equilibria. The work represents an attempt at coupling together thermodynamic and kinetic models for the diffusion-controlled3 phase transformations that occur in steels.     

Probing acid sites in MAPO-36 by solid state NMR

An ordering of magnesium is observed in the as-synthesized MAPO-36 molecular sieve. Upon calcination, part of the magnesium is removed from the sample and part occupies extraframework positions thus rendering a random distribution of magnesium in the lattice. The shoulder observed in the³¹P spectrum of the calcined sample is assigned to P(3Al, 1Mg) sites in conflict with the earlier assignment to P-OH groups. The bridging hydroxyl groups located at these sites are detected in the¹H MAS spectrum at 3.6 ppm. Further, MAPO-36 catalyzed acetone conversion to mesityloxide that cracked at elevated temperature to yield acetic acid and aliphatics.     

Technical Note: Selecting a Classification Method by Cross-Validation

If we lack relevant problem-specific knowledge, cross-validation methods may be used to select a classification method empirically. We examine this idea here to show in what senses cross-validation does and does not solve the selection problem. As illustrated empirically, cross-validation may lead to higher average performance than application of any single classification strategy, and it also cuts the risk of poor performance. On the other hand, cross-validation is no more or less a form of bias than simpler strategies, and applying it appropriately ultimately depends in the same way on prior knowledge. In fact, cross-validation may be seen as a way of applying partial information about the applicability of alternative classification strategies.     

Approximation algorithms for the bandwidth minimization problem for a large class of trees

We present approximation algorithms for the bandwidth minimization problem (BMP) for a large class of trees. The BMP is NP-hard, even for trees of maximum node degree 3. The problem finds applications in many areas, including VLSI layout, multiprocessor scheduling, and matrix processing, and has been studied for both graphs and matrices. We study the problem on trees having the following property: given any tree nodev, the depth difference of any two nonempty subtrees rooted atv is bounded by a constantk. We call such treesh(k)trees orgeneralized height-balanced (GHB)trees. The above definition extends the class of balanced trees to trees with depthd=Θ(\N\). For any tree in the above defined class, anO (logd) times optimal algorithm is presented. Furthermore, we extend the application of the algorithm to trees that simulate theh(k) property, which we callh(k)-like trees, and also provide intuitive ideas for an approximation algorithm for general trees.