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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

A survey of current continuous nonlinear multi-objective optimization (MOO) concepts and methods is presented. It consolidates and relates seemingly different terminology and methods. The methods are divided into three major categories: methods with a priori articulation of preferences, methods with a posteriori articulation of preferences, and methods with no articulation of preferences. Genetic algorithms are surveyed as well. Commentary is provided on three fronts, concerning the advantages and pitfalls of individual methods, the different classes of methods, and the field of MOO as a whole. The Characteristics of the most significant methods are summarized. Conclusions are drawn that reflect often-neglected ideas and applicability to engineering problems. It is found that no single approach is superior. Rather, the selection of a specific method depends on the type of information that is provided in the problem, the user’s preferences, the solution requirements, and the availability of software.

Survey of multi-objective optimization methods for engineering

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

The 2008 crash has left all the established economic doctrines - equilibrium models, real business cycles, disequilibria models - in disarray. Part of the problem is due to Smith’s "veil of ignorance": individuals unknowingly pursue society’s interest and, as a result, have no clue as to the macroeconomic effects of their actions: witness the Keynes and Leontief multipliers, the concept of value added, fiat money, Engel’s law and technical progress, to name but a few of the macrofoundations of microeconomics. A good viewpoint to take bearings anew lies in comparing the post-Great Depression institutions with those emerging from Thatcher and Reagan’s economic policies: deregulation, exogenous vs. endoge- nous money, shadow banking vs. Volcker’s Rule. Very simply, the banks, whose lending determined deposits after Roosevelt, and were a public service became private enterprises whose deposits determine lending. These underlay the great moderation preceding 2006, and the subsequent crash.

The Economic Institutions of Capitalism

This paper presents a modified and improved bi-directional evolutionary structural optimization (BESO) method for topology optimization. A sensitivity filter which has been used in other optimization methods is introduced into BESO so that the design solutions become mesh-independent. To improve the convergence of the optimization process, the sensitivity number considers its historical information. Numerical examples show the effectiveness of the modified BESO method in obtaining convergent and mesh-independent solutions. A study of the effects of various BESO parameters on the solution is then conducted to determine the appropriate values for these parameters.

Numerical stability and parameters study of an improved bi-directional evolutionary structural optimization method

This paper proposes a new topology optimization algorithm based on the bi-directional evolutionary structural optimization (BESO) method for the design of photonic band gap crystals. The photonic crystals are assumed to be periodically composed of two given dielectric materials. Based on the finite element analysis, the proposed BESO algorithm gradually re-distributes dielectric materials within the unit cell until the resulting photonic crystals possess a maximal band gap at the desirable frequency level. Numerical examples for both transverse magnetic (TM) and transverse electric (TE) polarizations are presented, and the optimized photonic crystals exhibit novel patterns markedly different from traditional designs of photonic crystals.

Topology Optimization of Photonic Band Gap Crystals

The research presented in this paper investigates new modes of architect-engineer interaction through the common application of evolutionary structural optimisation (ESO) and parametric design to allow for a more integrated work methodology across the two disciplines. The authors focus on the question if this approach is suitable for sponsoring a transdisciplinary work-environement through an additional digital interface. In summary, the hybrid software is used to explore a common architect/engineer design-space and a shared creative environment for the early stages of building design. A project case study is used to apply the tools and test the results.

Evolutionary structural optimisation and parametric design in transdisciplinary collaboration

A wound filler for use in treating a wound with negative pressure comprising: a porous wound fill material having an inner side designed to face a wound and an opposite outer side; and a plurality of stiffener elements located within the wound fill material, the stiffener elements extending between the inner side and the outer side of the wound fill material and arranged in a two dimensional pattern across the width and length of the wound fill material, the stiffener elements comprising a more rigid material than the porous wound fill material, wherein the stiffener elements are arranged between 5 to 25 degree angle to the vertical within the wound fill material when the wound filler is positioned within a wound bed.

Wound filler for negative pressure wound therapy

This paper develops the concept of the Integrated Computerized Multi-disciplinary Design Environment (ICMDE) proposed by the authors. By combining techniques of Finite Element Analysis, Computational Fluid Dynamics and Evolutionary Structural Optimization, the authors seek to create a streamlined digital structural platform.

Yi Min Xie

Papers

Numerical stability and parameters study of an improved bi-directional evolutionary structural optimization method

Topology Optimization of Photonic Band Gap Crystals

Evolutionary structural optimisation and parametric design in transdisciplinary collaboration

Wound filler for negative pressure wound therapy

Integrated computerized multi-disciplinary design environment for building structures