Nucleation and growth of β′magnesium sialons and their composition limits

Previous reports on the solubility of magnesium in -sialons have been conflicting. The present work shows conclusively that crystalline magnesium sialons with the silicon nitride structure do exist. They are formed by crystallization of magnesium sialon glasses at low temperatures. -magnesium sialon crystals nucleate on -sialon nuclei which are themselves formed by precipitation from Mg-Si-Al-O-N liquids at high temperatures. The current results suggest that -magnesium sialons exist only over a limited composition range within the 3M/4X plane of the Mg-Si-Al-O-N system, which is indicative of some form of ordering within the structure. Although the compositions investigated in the present study are unstable with respect to forsterite above about 1000° C, the possibility of producing -magnesium sialons which are stable at much higher temperatures cannot be fully discounted at present.     

Vessel motion thresholds for maintaining physical and cognitive performance: a study of naval personnel at sea

Methods and results are reported from a study of ships companies' exposure to low-frequency motions on three vessels of the Royal Navy. The aim of the study was to investigate relationships between deck accelerations and the incidence of problems such as difficulties with physical tasks, cognitive activities, motion sickness, and work effort. Ship motions were recorded continuously during sea patrols of 10-14 days. The data collected from the three vessels comprised 105 days of ship motions over 12 patrols, with 779 associated daily diaries from 78 participants. Problems most strongly associated with vessel motions were related to the difficulties with physical tasks. Some cognitive aspects of task performance and motion sickness were associated with vertical acceleration magnitudes, but the correlations were less strong than with physical tasks. Practitioner Summary: Little is known about the severity of ship motions that degrade physical and mental performance. The paper offers preliminary estimates of the motion threshold values below which the performance will not be degraded by motion.     

网页上做Office文档

经常出差在外，又没笔记本电脑，有时候处理一些文件就要跑到网吧去，而且要装Office软件的电脑才可以，很麻烦。后来存无意中发现了一个很不错的在线办公网站“ThinkFree”，这样随便在哪里上网部可以来处理文件了。     

The reality of divorce. Reply to Gordon (2005).

R. M. Gordon (2005; see record 2005-08806-011) insists in his commentary on J. S. Wallerstein and J. M. Lewis's (2004; see record 2004-17367-002) work that the impact of divorce on children is fleeting, and he proposes, without supporting evidence, that the long-lasting psychological problems displayed by children of divorce in adolescence and adulthood reflect more the preexisting psychopathology of the parents and their traumatic parenting than any consequence of the disrupted marriage and the unhappy sequelae that so regularly constitute the postdivorce family. The authors' data, based on intensive periodic clinical study of these youngsters and their parents over several decades, indicate the contrary. No research has established that divorcing parents exhibit as a class more mental illness than parents in intact families. The authors' findings speak to the unmet needs of children of divorce for psychological help with their intimate relationships when they enter adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mixed finite element method for coupled thermo‐hydro‐mechanical process in poro‐elasto‐plastic media at large strains

A mixed finite element for coupled thermo‐hydro‐mechanical (THM) analysis in unsaturated porous media is proposed. Displacements, strains, the net stresses for the solid phase; pressures, pressure gradients, Darcy velocities for pore water and pore air phases; temperature, temperature gradients, the total heat flux are interpolated as independent variables. The weak form of the governing equations of coupled THM problems in porous media within the element is given on the basis of the Hu–Washizu three‐filed variational principle. The proposed mixed finite element formulation is derived. The non‐linear version of the element formulation is further derived with particular consideration of the THM constitutive model for unsaturated porous media based on the CAP model. The return mapping algorithm for the integration of the rate constitutive equation, the consistent elasto‐plastic tangent modulus matrix and the element tangent stiffness matrix are developed. For geometrical non‐linearity, the co‐rotational formulation approach is utilized. Numerical results demonstrate the capability and the performance of the proposed element in modelling progressive failure characterized by strain localization and the softening behaviours caused by thermal and chemical effects. Copyright © 2005 John Wiley & Sons, Ltd.     

Development of a measure for the information technology infrastructure construct

The goal of this research was to operationalize the information technology infrastructure (ITI) concept by identifying its underlying dimensions and establishing a valid and reliable measure for the construct. In order to accomplish this task with the highest degree of certainty, two approaches were sequentially applied: exploratory factor analysis and confirmatory factor analysis. In evaluating the confirmatory factor model, a step-by-step process was employed, assessing unidimensionality, reliability, discriminant validity, and nomological validity. The dimensions of ITI were determined to be: Chief Information Officer, IT Planning, IT Security, Technology Integration, Advisory Committee, Enterprise Model, and Data Administration. Researchers may now make use of this validated ITI measure to conduct investigations of ITI and other organizational measures. Implications of the ITI measure with other organizational initiatives such as electronic commerce and knowledge management are explored.     

双机器人协调作业下碰撞算法及仿真研究

本文立足于关节水平，从双机器人碰撞研究入手，提出了机器人协同作业下碰撞检测 、干涉空间的算法，解决了机器人与周边环境任意障碍物碰撞问题．建立了连杆与连杆，连 杆与平面，连杆与任意三维实体避障理论模型，给出了相应的计算方法及计算机仿真结果．     

Mapping Conjugate Gradient Algorithms for Neutron Diffusion Applications onto SIMD, MIMD, and Mixed-Mode Machines

The performance of conjugate gradient (CG) algorithms for the solution of the system of linear equations that results from the finite-differencing of the neutron diffusion equation was analyzed on SIMD, MIMD, and mixed-mode parallel machines. A block preconditioner based on the incomplete Cholesky factorization was used to accelerate the conjugate gradient search. The issues involved in mapping both the unpreconditioned and preconditioned conjugate gradient algorithms onto the mixed-mode PASM prototype, the SIMD MasPar MP-1, and the MIMD Intel Paragon XP/S are discussed. On PASM , the mixed-mode implementation outperformed either SIMD or MIMD alone. Theoretical performance predictions were analyzed and compared with the experimental results on the MasPar MP-1 and the Paragon XP/S. Other issues addressed include the impact on execution time of the number of processors used, the effect of the interprocessor communication network on performance, and the relationship of the number of processors to the quality of the preconditioning. Applications studies such as this are necessary in the development of software tools for mapping algorithms onto either a single parallel machine or a heterogeneous suite of parallel machines.