Marc A. Meyers

Bio: Marc A. Meyers is an academic researcher from University of California, San Diego. The author has contributed to research in topics: Deformation (engineering) & Dislocation. The author has an hindex of 85, co-authored 487 publications receiving 36646 citations. Previous affiliations of Marc A. Meyers include University of California & Instituto Militar de Engenharia.

Shock synthesis of silicides

Abstract: Niobium, molybdenum, and titanium silicides were synthesized by shock waves travelling through mixtures of elemental powders; the explosively generated impact experiments were carried out on powders at ambient temperature and pre-heated to 500°C. The unreacted, partially reacted, and fully reacted regions were mapped and correlated with pressure and energy levels predicted from computations. Characterization of the partially reacted regions (for Nb-Si) showed that melting of silicon is a critical requirement for the initiation of the reaction; niobium dissilicide spherules nucleate and grow at the Nb-Si interface and eventually detach themselves. Concurrently, solid state diffusion of Si into Nb creates Nb5Si3, which acts as a barrier for further reaction. In parallel experiments on Nb-Si diffusion couples heated to 1200°C, it is found that the same reaction sequence occurs (NbSi2 → Nb5Si3). A preliminary analysis is conducted based on the requirement for silicon melting for reaction to occur. This analysis predicts critical melt pool sizes for reactions, which can be correlated to shock energy. Two important parameters in this analysis are: the heat of reaction and the thermal diffusivity of the components.

Combustion synthesis/quasi-isostatic pressing of TiC0.7–NiTi cermets: microstructure and transformation characteristics

Abstract: TiC0.7–NiTi cermets were produced by combustion synthesis followed by quasi-isostatic consolidation while the reaction products were still hot and ductile. The TiC0.7–NiTi cermets were characterized by differential scanning calorimetry, room temperature transmission electron microscopy (TEM), and in-situ TEM (temperature varied during observation). The matrix of the as-synthesized 20NiTi, 40NiTi, and 60NiTi composites contains both R and B19′ martensites at room temperature. No distinct R-phase morphology could be imaged. In the B19′ martensite, [011] Type II twinning, \( (11\bar 1) \) Type I twinning and (001) compound twinning modes were observed as the lattice invariant shear (LIS) of the R-B19′ transformation. The [011] Type II twinning is often reported as the LIS of the B2-B19′ transformation, but this is the first experimental confirmation of its predicted presence as a qualified LIS of the R-B19′ transformation. The (001) compound twinning mode is responsible for the fine structure of the martensite with a wavy morphology. Nanoscale structures with a thickness of 5 nm were obtained inside the twins. Twinning was also observed at the interface with carbide particles, which confirms that some stress relaxation of the elastic mismatch occurs. At room temperature, the matrix of the 80NiTi composite had the R-phase structure, which appeared with a needle-like morphology. Thermal cycling resulted in the suppression of the R-phase transformation. This is the opposite of the behavior observed in un-reinforced NiTi alloys.

Shear-Induced Exothermic Chemical Reactions

Abstract: La structure de bandes de cisaillement crees dans des poudres reactives Ti-Si a etee etudiee avec le collapse symmetrique d'un cylindre de parois epaisse. Les bandes de cisaillement se forment a des deformations globales de 0.2-0.4 a une vitesse de deformation de 10 4 s -1 Dans les bandes de cisaillement les deformations de cisaillement atteignent des valeurs jusqu'a 100 et la vitesse de deformation est 10 7 s -1 . Les reactions chimiques sont initiees dans ces bandes de cisaillement. Leur propagation dans l'echantillion demande une deformation globale critique. La modelisation des bandes de cisaillement avec la reaction des poudres reactives est proposee. Il est possible d'estimer le taux de reaction a partir de regions triangulaires formees par les bandes de cisaillement dans lesquelles il n'y a pas eu de reaction.

Fast parallel algorithms for short-range molecular dynamics

Abstract: 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.

Using Multivariate Statistics

Abstract: Thank you for downloading using multivariate statistics. As you may know, people have look hundreds times for their favorite novels like this using multivariate statistics, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they juggled with some harmful bugs inside their laptop. using multivariate statistics is available in our digital library an online access to it is set as public so you can download it instantly. Our books collection saves in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Merely said, the using multivariate statistics is universally compatible with any devices to read.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load

Abstract: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a “nanostressing stage” located within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope and was recorded on video. The MWCNTs broke in the outermost layer (“sword-in-sheath” failure), and the tensile strength of this layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were loaded. Analysis of the stress-strain curves for individual MWCNTs indicated that the Young's modulus E of the outermost layer varied from 270 to 950 gigapascals. Transmission electron microscopic examination of the broken nanotube fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse.