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

This paper reflects on how to practically achieve the necessary organizational and curricular preconditions that allow for conducting Multi􀀀Inter􀀀and Trans – disciplinary engineering capstone design industry􀀀sponsored projects and thereby serve engineering graduates better. The differences between offering multidisciplinary and the common singledisciplinary capstone design courses are also highlighted. Simultaneously, this paper focuses on the key challenges that aggravate the smooth implementation of such a complex undertaking the fundamental goal of which is to offer a multidisciplinary team-based design project work experience to the Students that would be mimicking as close as possible an analogue typical industrial setting. Possible remedial measures for overcoming these challenges are also discussed. A new multidisciplinary capstone design project course offered at the Faculty of Applied Science and Engineering (FASE) at the University of Toronto in the 2013/14 academic year (“APS 490Y Multidisciplinary Capstone Design”) coordinated by Prof. Kamran Behdinan served as the basis for this work.

https://ojs.library.queensu.ca/index.php/PCEEA/article/download/5940/5662

What constitutes a multidisciplinary capstone design course? best practices, successes and challenges.

For the application of squeeze film damper (SFD) in aero-engine, a cavitation model is evaluated by means of linear complementarity problem (LCP) method. Different from the conventional SFD study that employs circular-center orbits (CCOs), a realistic condition is explored where the shaft whirling center and bearing center are misaligned. Taking into account the fluid as incompressible and compressible, the governing equations, including film cavitation, are respectively solved by developing an algorithm using the LCP method. The numerical results are compared with experimental data and the effectiveness of the model is verified. The proposed model can provide some references to investigate the competency of this cavitation method in SFDs.

https://www.mdpi.com/2075-4442/5/4/46/pdf

The Evaluation of Linear Complementarity Problem Method in Modeling the Fluid Cavitation for Squeeze Film Damper with Off-Centered Whirling Motion

Large companies such as Amazon and Google are currently testing deliveries using unmanned drones, intending to use these drones on the market. Topics tackled in this field of research include object collision routing optimization, delivery routing optimization, battery management optimization, and the addition of solar panels on the drones. Little publicly available research has been found to have been conducted on developing the methods to optimize the powertrain of the drones to maximize their delivery radii through modifying their electric motor and propeller parameters. In working towards that goal, this paper puts forth a delivery drone driving cycle simulation written in MATLAB with which to monitor their performance and fine-tune their properties. The driving cycle has been written to accommodate unmanned drones that use any number of propellers and perform vertical take-off and landing maneuvers. This driving cycle algorithm iteratively runs through multiple driving profiles to find the one which produces the maximal delivery radius for the drone. A data processing tool for polynomial interpolation, which is also written in MATLAB, is developed to manipulate the electric motor and propeller data into usable states for the simulation. For the tested drone configurations, no discernible pattern was noticed in the ideal power throttle needed to reach cruise altitude most efficiently. During cruise, an ideal pitch between 27 to 47 degrees which allowed them to displace horizontally while spending the least amount of energy per meter was found for all configurations.

Delivery Drone Driving Cycle

Reaming is a finishing process used to remove a small amount of material from a predrilled hole. In low speed cutting processes, it is the formation of lobed or multi-cornered holes that is of concern, rather than tool chatter, which occurs at high speed near the natural frequency of the tool. Using a quasi-static model in the characteristic form for the reaming process, a finite element modeling for the low speed reaming process, based on the Euler–Bernoulli beam model, was developed. Cutting and rubbing forces were applied as concentrated and distributed forces on a variable engagement length of the reamer. The variable engagement length is considered to simulate the actual applied forces length as the reamer advances to the workpiece. The time dependant changes in the bending stiffness of the reamer were included in the governing equation of the equilibrium of the reamer, and its stability analysis was performed at different time steps. Using this model, the vibration damping effect of uneven spacing of reamer teeth was investigated. The results demonstrate that uneven spacing of reamer teeth reduces the tool vibration, and therefore leads to a more stable condition. Finally, the optimum configuration of uneven tooth pitch angles for a six-flute reamer, in order to have the highest vibration decay rate during the reaming, was presented.

Kamran Behdinan

Papers

What constitutes a multidisciplinary capstone design course? best practices, successes and challenges.

The Evaluation of Linear Complementarity Problem Method in Modeling the Fluid Cavitation for Squeeze Film Damper with Off-Centered Whirling Motion

Delivery Drone Driving Cycle

Finite element modeling of low speed reaming vibrations with reamer geometry modifications

Damped harmonic vibrations of axisymmetric graphene-enhanced cylinders in thermal environment