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

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Additive manufacturing of metallic components – Process, structure and properties

How have Japanese companies become world leaders in the automotive and electronics industries, among others? What is the secret of their success? Two leading Japanese business experts, Ikujiro Nonaka and Hirotaka Takeuchi, are the first to tie the success of Japanese companies to their ability to create new knowledge and use it to produce successful products and technologies. In The Knowledge-Creating Company, Nonaka and Takeuchi provide an inside look at how Japanese companies go about creating this new knowledge organizationally. The authors point out that there are two types of knowledge: explicit knowledge, contained in manuals and procedures, and tacit knowledge, learned only by experience, and communicated only indirectly, through metaphor and analogy. U.S. managers focus on explicit knowledge. The Japanese, on the other hand, focus on tacit knowledge. And this, the authors argue, is the key to their success--the Japanese have learned how to transform tacit into explicit knowledge. To explain how this is done--and illuminate Japanese business practices as they do so--the authors range from Greek philosophy to Zen Buddhism, from classical economists to modern management gurus, illustrating the theory of organizational knowledge creation with case studies drawn from such firms as Honda, Canon, Matsushita, NEC, Nissan, 3M, GE, and even the U.S. Marines. For instance, using Matsushita's development of the Home Bakery (the world's first fully automated bread-baking machine for home use), they show how tacit knowledge can be converted to explicit knowledge: when the designers couldn't perfect the dough kneading mechanism, a software programmer apprenticed herself withthe master baker at Osaka International Hotel, gained a tacit understanding of kneading, and then conveyed this information to the engineers. In addition, the authors show that, to create knowledge, the best management style is neither top-down nor bottom-up, but rather what they call "middle-up-down," in which the middle managers form a bridge between the ideals of top management and the chaotic realities of the frontline. As we make the turn into the 21st century, a new society is emerging. Peter Drucker calls it the "knowledge society," one that is drastically different from the "industrial society," and one in which acquiring and applying knowledge will become key competitive factors. Nonaka and Takeuchi go a step further, arguing that creating knowledge will become the key to sustaining a competitive advantage in the future. Because the competitive environment and customer preferences changes constantly, knowledge perishes quickly. With The Knowledge-Creating Company, managers have at their fingertips years of insight from Japanese firms that reveal how to create knowledge continuously, and how to exploit it to make successful new products, services, and systems.

The knowledge-creating company

Singular Integral Equations. By N.I. Muskhelishvili. Translated fromthe 2nd Russian edition by J.R.M. Radok. Pp. 447. F1. 28.50. 1953. (Noordhoff, Groningen)

A numerically efficient and fast method of solution for cracks or slip bands with a crack opening or shearing displacement-dependent cohesive stress can be developed on the basis of a Gauss-Chebyshev quadrature rule for hypersingular integrals. The resulting iterative scheme allows different 'hardening' or 'bridging' laws to be explored in a consistent manner.

Analysis of cohesive zones in cracks and slip bands using hypersingular interpolative quadratures

To investigate grain rotation caused by twinning-detwinning during plastic deformation, experiments using synchrotron high energy X-ray Diffraction (XRD) and Electron Backscatter Diffraction (EBSD) are carried out under in situ compression-tension loading. Comparison between the XRD and EBSD data confirms that the intensity change of diffraction rings in XRD experiment is caused by twining and detwinning. A good agreement of twin fraction values obtained from XRD and EBSD is achieved. This demonstrates that the grains and texture are homogeneously distributed along the normal direction of the sample. In the meantime, it is observed that detwinning can only be activated in a large quantity when the loading reverses into tension from compression in the first loading stage.

Grain Rotation during Twin-Detwin Deformation of Mg AZ31 Alloy Using In Situ XRD and EBSD

Owing to the importance of micro- and nanoscale residual stress evaluation methods in the context of current research and technology, this separate chapter is devoted to this topic. It begins with an overview of microfocus diffraction techniques with X-ray and electron beams, and spectroscopic methods, e.g., Raman. The rest of the chapter is devoted to the history of the development and illustration of use of the Focused Ion Beam—Digital Image Correlation (FIB-DIC) technique, with particular attention paid to the microscale ring-core method. FIB-DIC spatially resolved residual stress profiling is classified into sequential and parallel approaches, and case studies exemplifying the use of these approaches are described.

Microscale Methods of Residual Stress Evaluation

Equiatomic Cobalt-Iron (Co-Fe 50%at.) has great potential as a soft magnetic alloy, but its wider use has been limited by its poor workability and strength. Recent advancements in Laser Powder Bed Fusion (LPBF), an Additive Manufacturing (AM) technique, provided a new pathway for constructing fully dense, structurally sound, complex-shaped components from bulk equiatomic Co-Fe in a single process step. To obtain the desirable soft magnetic performance in the alloy, thermal post-processing with a controlled slow cooling needs to be applied. In order to identify the optimum heating conditions, several single and multiple step heat treatment profiles were performed and compared. The effects of the thermal post-processing on the microstructure, structural ordering, and functional properties of the alloy after each heat treatment were investigated using electron microscopy, neutron diffraction (ND), electron backscatter diffraction (EBSD), and quasi-static magnetic characterisation in a closed loop magnetic circuit. Results have shown that a normalisation heat treatment at 1300 K for 2-hours followed by a 4-hour primary heat treatment at 1123 K and slow cooling to room temperature produced a recrystallised microstructure characterised by predominantly equiaxed grains with an average size of up to 61 µm, and a fully ordered B2 structure. The quasi-static soft magnetic properties obtained were favourable compared to those of commercial Co-Fe grades, with maximum relative permeability higher than 8000, coercivity as low as 112 A/m and magnetic saturation polarization of 2.39 Tesla. These findings provide the basis to enable the manufacturing of three-dimensional complex-shaped electromagnetic cores by LPBF. 

Effect of heat treatment on the microstructure and magnetic properties of laser powder bed fusion processed equiatomic Co-Fe

The dentine-enamel junction (DEJ) is an important biological interface between the highly mineralized hard out layer (enamel) and the comparatively softer tooth core (dentine) of teeth. The remarkable performance of this interface provides the motivation for investigation into the detailed structure and function of the DEJ. In this study, synchrotron X-ray diffraction measurements of the DEJ subjected to the in situ uniaxial loading were carried out to capture the structure-property relationship between the DEJ architecture and its response to the applied force. The knowledge of the architecture and properties of the natural DEJ will hopefully help in biomimetic engineering of superior dental restorations and prostheses, and the development of novel materials to emulate the DEJ.

Alexander M. Korsunsky

Papers

Analysis of cohesive zones in cracks and slip bands using hypersingular interpolative quadratures

Grain Rotation during Twin-Detwin Deformation of Mg AZ31 Alloy Using In Situ XRD and EBSD

Microscale Methods of Residual Stress Evaluation

Effect of heat treatment on the microstructure and magnetic properties of laser powder bed fusion processed equiatomic Co-Fe

In Situ X-Ray Diffraction Measurements of the Apparent Modulus of Human Dental Tissue in the Vicinity of the Dentine-Enamel Junction (DEJ)