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

THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Macroporous ceramics with pore sizes from 400 nm to 4 mm and porosity within the range 20%–97% have been produced for a number of well-established and emerging applications, such as molten metal filtration, catalysis, refractory insulation, and hot gas filtration. These applications take advantage of the unique properties achieved through the incorporation of macropores into solid ceramics. In this article, we review the main processing routes that can be used for the fabrication of macroporous ceramics with tailored microstructure and chemical composition. Emphasis is given to versatile and simple approaches that allow one to control the microstructural features that ultimately determine the properties of the macroporous material. Replica, sacrificial template, and direct foaming techniques are described and compared in terms of microstructures and mechanical properties that can be achieved. Finally, directions to future investigations on the processing of macroporous ceramics are proposed.

/pdf/processing-routes-to-macroporous-ceramics-a-review-1urld578zq.pdf

Processing Routes to Macroporous Ceramics: A Review

Increase mechanical strength in porcelain stoneware tile by ion exchange

In this work, an experimental design was used to analyze the influence of process parameters on the production of extracellular enzymes such as β-glucosidase and peroxidase, and their possible effect on the obtention of soluble and nanostructured silica from rice husk ash by the action of the fungus Fusarium oxysporum. Specifically, pH, fermentation time and glucose concentration in the culture medium were varied. Statistical analysis indicated that the silica synthesis in the aqueous medium was strongly dependent on pH and time. Although the glucose concentration does not exert a direct influence on the biosynthesis of silica, it is an important parameter in the production of extracellular enzymes. To prevent enzyme inhibition and provide higher dissolution of silica, it is recommended to work at a pH close to neutral with a glucose concentration of 3 g L-1 for at least 144 h.

/pdf/influencia-de-parametros-de-processo-na-obtencao-de-silica-a-4xror7f430.pdf

Influência de parâmetros de processo na obtenção de sílica a partir de cinza da casca de arroz pela ação de Fusarium oxysporum

For advanced ceramic composites, affordable manufacturing is still the most essential shortcoming with respect to successful commercial use. This holds particularly for components made out of composites with complex hierarchical structures and high demands of mechanical performance and reliability at the same time, e.g. fiber-reinforced ceramic matrix composites (FRCMCs). Therefore, a new processing route is presented here, which is based on the lamination of thermoplastic prepregs. This route allows not only affordable manufacturing, but also advanced mechanical reliability. Powder metallurgy techniques are combined here with concepts from the prepreg technology in a route consisting of the following steps (a) manufacturing of 2 D prepregs using commercial fiber fabrics which are infiltrated with compounds of ceramic particles embedded in an organic matrix, (b) followed by respective stacking and joining, (c) burn out of the organic matrix and (d) sintering to consolidate the matrix. Composites consisting of a porous Al2O3/ZrO2 matrix, reinforced by 8 layers of NextelTM 610 fiber fabric exhibit a bending strength of ~440 MPa, with graceful failure behavior, e.g. a stepwise stress reduction after peak nominal stress. The fracture of these composites is controlled by a series of interfacial delamination events, which enhance energy dissipation during failure.

Multilayered Fiber-Reinforced Oxide Composites Produced by Lamination of Thermoplastic Prepregs

Otimizacao de formulas de massas ceramicas de faianca

In this work aqueous ceramic suspensions were prepared from a parent glass-ceramic powder (3.8 μm) belonging to the LZSA (Li2O-ZrO2-SiO2-Al2O3) system without or with additions of different volume fractions (1.0-7.5%) of TiO2 nanoparticles (25 nm). The obtained suspensions were rheologically characterized so that stable suspensions were defined e formed by slip casting. The obtained compacts were sintered (850-950°C/60 min) and their green and sintered densities were determined and related to linear shrinkage measurements. The results showed that samples sintered at 950oC for 60 min with 1.0% TiO2 addicted presented linear shrinkage of 12% and relative densities of 97%.

Dachamir Hotza

Papers

Increase mechanical strength in porcelain stoneware tile by ion exchange

Influência de parâmetros de processo na obtenção de sílica a partir de cinza da casca de arroz pela ação de Fusarium oxysporum

Multilayered Fiber-Reinforced Oxide Composites Produced by Lamination of Thermoplastic Prepregs

Otimizacao de formulas de massas ceramicas de faianca

Effect of the Addition of TiO2 Nanoparticles on the Sinterability of a Glass Belonging to the LZSA Glass-Ceramic System