Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

การวจยเชงคณภาพ เปนเครองมอสำคญอยางหนงสำหรบทำความเขาใจสงคมและพฤตกรรมมนษย การวจยแบบการสรางทฤษฎจากขอมล กเปนหนงในหลายระเบยบวธการวจยเชงคณภาพทกำลงไดรบความสนใจ และเปนทนยมเพมสงขนเรอยๆ จากนกวชาการ และนกวจยในสาขาสงคมศาสตร และศาสตรอนๆ เชน พฤตกรรมศาสตร สงคมวทยา สาธารณสขศาสตร พยาบาลศาสตร จตวทยาสงคม ศกษาศาสตร รฐศาสตร และสารสนเทศศกษา ดงนน หนงสอเรอง “ConstructingGrounded Theory: A Practical Guide through Qualitative Analysis” หรอ “การสรางทฤษฎจากขอมล:แนวทางการปฏบตผานการวเคราะหเชงคณภาพ” จะชวยใหผอานมความรความเขาใจถงพฒนาการของปฏบตการวจยแบบสรางทฤษฎจากขอมล ตลอดจนแนวทาง และกระบวนการปฏบตการวจยอยางเปนระบบ จงเปนหนงสอทควรคาแกการอานโดยเฉพาะนกวจยรนใหม เพอเปนแนวทางในการนำความรความเขาใจไประยกตในงานวจยของตน อกทงนกวจยผเชยวชาญสามารถอานเพอขยายมโนทศนดานวจยใหกวางขวางขน

Constructing Grounded Theory: A Practical Guide through Qualitative Analysis

This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Introduction to the Finite Element Method

Smoothed particle hydrodynamics (SPH) is a meshfree particle method based on Lagrangian formulation, and has been widely applied to different areas in engineering and science. This paper presents an overview on the SPH method and its recent developments, including (1) the need for meshfree particle methods, and advantages of SPH, (2) approximation schemes of the conventional SPH method and numerical techniques for deriving SPH formulations for partial differential equations such as the Navier-Stokes (N-S) equations, (3) the role of the smoothing kernel functions and a general approach to construct smoothing kernel functions, (4) kernel and particle consistency for the SPH method, and approaches for restoring particle consistency, (5) several important numerical aspects, and (6) some recent applications of SPH. The paper ends with some concluding remarks.

Smoothed Particle Hydrodynamics (SPH): an Overview and Recent Developments

Multidisciplinary design optimization is a field of research that studies the application of numerical optimization techniques to the design of engineering systems involving multiple disciplines or components. Since the inception of multidisciplinary design optimization, various methods (architectures) have been developed and applied to solve multidisciplinary design-optimization problems. This paper provides a survey of all the architectures that have been presented in the literature so far. All architectures are explained in detail using a unified description that includes optimization problem statements, diagrams, and detailed algorithms. The diagrams show both data and process flow through the multidisciplinary system and computational elements, which facilitate the understanding of the various architectures, and how they relate to each other. A classification of the multidisciplinary design-optimization architectures based on their problem formulations and decomposition strategies is also provided, a...

Multidisciplinary design optimization: A survey of architectures

Due to the increased use of composite materials in the aerospace industry, numerous attempts have been made to develop fatigue models in order to predict the fatigue behaviour and consequently the fatigue life of these materials. Existing fatigue models have significant deficiencies, thus are not widely acceptable in the industry. A better understanding of the exhibited fatigue behaviour of composite materials is consequently required. The complex nature of fatigue behaviour in fiber-reinforced composite materials is presently investigated. An explicit progressive damage model, that is mechanistic in nature, is currently being developed using the concept of a representative volume element. A micromechanical finite element model that is capable of explicit damage initiation and propagation modeling is utilized for simulation of damage development. The predicted numerical results illustrate the capabilities of the current model. Future work is also outlined in the paper as the development of the fatigue model is continued.

Considerations for progressive damage in fiber-reinforced composite materials subject to fatigue

The fast development and expansion of the robotics field and biomedical application in the last several decades have generated a growing interest in the flexible tactile sensing solutions. In this experimental study, the flexible sensor material is characterized by utilizing piezoresistive mechanism based on quantum tunneling composites. With attention to pressure-sensitivity of this composite, the effect of nickel powder filler ratio and sample thickness are systematically investigated. Electrical resistance and sensitivity of the QTC depend on the concentration and shape of nickel powder. There is a lower threshold of nickel powder concentration for the QTC to be sensitive under 500N force applied. With increasing nickel powder concentration, an elasticity of the QTC decreases, but stability, reproducibility, and sensitivity of the composite improved.

Characterization of the Repeatability and Sensitivity of the Quantum Tunneling Composites

In the early phase of product development, there is only limited knowledge regarding relevant objectives and requirements since knowledge carriers and a knowledge base must be first identified and established respectively. Due to continuously increasing knowledge about the system to be developed, objectives change rapidly which leads to a temporal dependency. Therefore, product developers are challenged with modeling objectives as conventional methods like specification sheets struggle to deal with these dynamics. Systems of Objectives allow to model objectives, requirements and boundary conditions along with their dependencies. From existing maturity models, correlations between Systems of Objectives and the degree of maturity of products can be derived. However, these models usually focus directly on validation objects like prototypes which are difficult and expensive to develop due to the dynamics in the early phases. Therefore, an approach for determining the concretization level of Systems of Objectives is useful to derive the product maturity level in the early phases. Through a literature review, standards governing the formulation of objectives and requirements as well as existing maturity models were analyzed. These were supplemented by a qualitative expert study and evaluated subsequently. Criteria for measuring the concretization level of Systems of Objectives were derived to develop a description model that allows relevant criteria to be categorized into three dimensions: Diversity, Level of Detail, and Validity. The assumptions for the proposed description model were validated in a study with 11 experts from research and industry. The description model allows the continuous measurement of the concretization level of the System of Objectives-providing early support for product developers.

Measuring the concretization level of Systems of Objectives in the early phase of product development to derive the product maturity

Computational fluid dynamics modeling of insertion and advancement of a reamer into the intramedullary canal of a long bone.

The r-refinement of the finite element method locates the positions of nodes to increase accuracy based on a mesh with a given number of elements and a given set of nodal variables. To compare with the conventional refinements by increasing the number of nodal variables, the r-refinement does not increases computations but increase the accuracy of approximated solutions. This paper presents the application of the r-refinement on a flexible four-bar linkage, and provides the study of the effect of the r-refinement on the constant/periodical rotating speed and the discretization of the input link. The results are compared with those by increasing the number of elements.Copyright © 2005 by ASME

Kamran Behdinan

Papers

Considerations for progressive damage in fiber-reinforced composite materials subject to fatigue

Characterization of the Repeatability and Sensitivity of the Quantum Tunneling Composites

Measuring the concretization level of Systems of Objectives in the early phase of product development to derive the product maturity

Computational fluid dynamics modeling of insertion and advancement of a reamer into the intramedullary canal of a long bone.

The R-Refinement Finite Element Analysis of Flexible Four-Bar Linkage