There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Additive manufacturing of metallic components – Process, structure and properties

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

Unlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM proc...

Laser additive manufacturing of metallic components: materials, processes and mechanisms

Contents: Introduction to Transport Phenomena Thermodynamics of Multiphase Systems Generalized Governing Equations: Local Instance Formulations Generalized Governing Equations Averaging Formulations Solid-Liquid-Vapor Phenomena and Interfacial Heat and Mass Transfer Melting and Solidification Sublimation and Vapor Deposition Condensation Evaporation Boiling Two-Phase Flow and Heat Transfer 1064 pages, 403 figures, 292 problems and 62 examples.

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Transport Phenomena in Multiphase Systems

Pulsating (or oscillating) heat pipes (PHP or OHP) are new two-phase heat transfer devices that rely on the oscillatory flow of liquid slug and vapor plug in a long miniature tube bent into many turns. The unique feature of PHPs, compared with conventional heat pipes, is that there is no wick structure to return the condensate to the heating section; thus, there is no countercurrent flow between the liquid and vapor. Significant experimental and theoretical efforts have been made related to PHPs in the last decade. While experimental studies have focused on either visualizing the flow pattern in PHPs or characterizing the heat transfer capability of PHPs, theoretical examinations attempt to analytically and numerically model the fluid dynamics and/or heat transfer associated with the oscillating two-phase flow. The existing experimental and theoretical research, including important features and parameters, is summarized in tabular form. Progresses in flow visualization, heat transfer characteristics, and ...

Advances and Unsolved Issues in Pulsating Heat Pipes

by experimental results. The visualization test showed that the oscillatory flow formed waves that traveled among the turns of PHPs. Their theoretical model could be used to estimate the pressure and displacement of oscillatory flow. Kiseev and Zolkin @7# experimentally investigated the effects of acceleration and vibration on the performance of the unlooped PHP. Acetone was used as the working fluid and the filling charge ratio was 60 percent. Their results indicated that the PHP operates successfully by various acceleration effects. There was an increase in evaporator temperature, about 30 percent by increase of the acceleration from 26g to 112g. Dobson and Harms @8# presented simple mathematical models in which the behavior of PHPs was simulated. The mathematical model was applied to the open-ended PHP. They showed that the oscillating behavior would be different for different initial values. Wong et al. @9# proposed a theoretical model of PHPs based on a Lagrangian approach in which the flow was modeled under adiabatic conditions for the entire PHP. A sudden pressure pulse was applied to simulate local heat input into a vapor plug. They were able to show the pressure and velocity variations with time for the vapor plugs. In the present study, a very detailed theoretical model will be developed to accurately simulate the behavior of liquid slugs and vapor plugs in both unlooped and looped PHPs. Heat transfer due to the phase change is also considered.

Yuwen Zhang

Papers

Transport Phenomena in Multiphase Systems

Advances and Unsolved Issues in Pulsating Heat Pipes

Thermal Modeling of Unlooped and Looped Pulsating Heat Pipes

Heat transfer in a pulsating heat pipe with open end

Advanced Heat and Mass Transfer