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.

Global Science and Technology: Past, Present and Future

Abstract: In a bold partnership, ABM and Elsevier have launched the Journal of Materials Research and Technology and asked me to be the International Associate Editor. The first issues of this journal already signal its broad reach and coverage: it is already a global journal, with submissions of original research articles from the international scientific community. The invited review articles are timely and written by global leaders in their fields. The Area Editors and Advisory Board have representatives from Europe, Asia, the Middle East, as well as the Americas. The standards are the same as the leading Elsevier journals. This journal epitomizes the paradigm ‘Science without Borders.’ Indeed, science is a global undertaking. Discoveries have always traveled through land and sea. Great centers of learning and knowledge – Athens, Alexandria, Damascus, Beijing, Florence, Paris, Cambridge, and others – have since antiquity attracted scholars globally. These places acquire a special spirit through which transformative changes in our understanding of the universe takes place. It is a mysterious but powerful process. In parallel with this evolution of knowledge, technology has, since pre-history, rapidly flowed from the site of discovery to applications. In Brazil, the second half of the nineteenth and the twentieth centuries witnessed a rapid industrialization process in which technologies were imported. The magnificent example of the steel industry is a testament to the pioneering spirit of foreign engineers that joined forces with Brazilians and created CSBM, CSN, and other companies. This knowledge, generated in Europe and the USA, was assimilated and adapted to the Brazilian conditions, and has now reached a level of maturity and uniqueness that is leading to the reverse flow: Gerdau, Petrobras, Embraer, CVRD, and others are currently exporting technology and entrepreneurship. The same process has taken place in science. The first tremors of metallurgical research are perhaps traced to the Escola de Minas de Ouro Preto (Ouro Preto School of Mines), founded in 1876 by a decree from the Emperor Dom Pedro II. A dedicated and gifted man, he is recognized by many as the greatest ruler Brazil has had. Educated by Jose Bonifácio de Andrada, he had a passion for science that remained unabated, in spite of the severe criticism that he had to endure by the parliament for founding the Escola de Minas de Editorial

Applying Bio-Inspired hierarchical design to jamming technology: Improving density-efficient mechanical properties and opening application spaces

Abstract: In the soft-robotics field, bio-inspiration is often cited, pointing to the animal-like forms created—however, the concept of hierarchical architecture common to biological materials has yet to be applied effectively. Here, it is shown how that by considering the hierarchical structure of the medium (primary level), the organization of jamming media (secondary level), and the organization of jammers (tertiary level) new functionalities not possible with conventional jamming technology can be obtained. This is accomplished at the three layers enumerated above. At the primary level, optimal compositions of fibrous flakes and grains are identified to improve stiffness and strength per unit weight; fish-inspired ganoid scales are used to create flexible armors. At the secondary level, layers and grains are combined in the tensile and compressive faces of beams to maximize mechanical properties, while ganoid scales of different compositions are layered to create mechanical gradients, among other combinations of jamming media. Finally, at the tertiary level, the isotropy of triadically woven jammers is demonstrated relative to traditional biaxial jammers; a cylindrical “finger-trap” weave with adjustable radius is shown. The improved mechanical weight-efficiency, anisotropy control, mechanical property gradients, and other features enabled by considering hierarchical design in jamming promise new application spaces for an established field.

Martensitic transformation induced by tensile stress waves

Abstract: It is shown that tensile pulses generated by the reflection of compressive shock waves at a free surface can produce (γ+α′) martensitic transformation in an Fe-32.3 wt pct Ni-.035 wt pct C alloy. The tensile hydrostatic component of the stress interacts with the dilatational strains (0.04) produced by the martensitic transformation resulting in an increase of Ms, the martensitic start temperature. The shock waves were produced by normal impact of a target by a projectile accelerated in a one-stage gas gun. Experiments were conducted at temperatures between −10° and −50°C (Ms = −61°C) at a constant pressure of 1.5 GPa and pulse duration of 0.75 μs; and at variable pulse durations (0.19 – 1.5 μs) at a constant pressure of 1.5 GPa and a temperature of −30°C. Shock-induced inhomogeneities were observed in the recovered specimens. They manifested themselves as long bands with no crystallographic relationship to the structure and provided preferential nucleation regions for martensite. The observed inhomogeneous “stringers” serve as markers for the shock-induced inhomogeneities.

The Attenuation of Shock Waves in Nickel

Abstract: The attenuation of planar shock waves generated by plate impact was monitored by their decay throughout massive nickel blocks. This was accomplished, during the passage of the wave, by manganin piezoresistive gages connected to oscilloscopes and, in the post-shocked condition, by hardness measurements and TEM observations at various distances from the impact surface in the nickel blocks. The nickel systems exhibited different metallurgical microstructures before shock loading: preshocked (grain size 150 μm), annealed (grain size 150 μm)and annealed (grain size 32 μm). For each system two different initial shock pressures were used: 10 and 25 GPa. The pulse duration was held constant at 2 μs. The experimental records of oscilloscopes showed that there are no significant effects of grain size and pre-deformation on the attenuation in nickel. The observed attenuation was compared with the calculated one according to hydrodynamic theory and poor agreement was found, An “accumulation” model based on the conservation of energy is presented herein to explain the dissipative processes of shock waves in metals.

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

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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.