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

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

Phd by thesis

Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

/pdf/carbon-nanotubes-present-and-future-commercial-applications-1nhq3xy4hh.pdf

Carbon Nanotubes: Present and Future Commercial Applications

비만아 부모의 돌봄 경험: q 방법론

Characterization Techniques for CNT-MMC Materials

Carbon Nanotube Reinforced Metal Matrix Composite (CNT-MMC) Systems

Abstract Technologically important Oxide Dispersion-Strengthened steels are synthesized using ZrO 2 as a dispersion strengthener instead of conventionally used Y 2 O 3 . Powder metallurgical route followed by spark plasma sintering is adopted for synthesizing the material. Detailed microstructural characterization revealed a fine-grained microstructure with finer dispersoids in as-sintered and normalized condition. The stable microstructure is found to be retained even after subjecting the samples at 973 K for as long as 1000 h for long-term thermal aging trials, indicating at a possible superiority of this material over the conventional Oxide Dispersion-Strengthened steels. The yield strength is calculated by making use of microstructural parameters and predictive models, both of which shown a good agreement. Mechanical property analysis through hardness measurements was correlated with microstructural observations and compared with the conventional Oxide Dispersion-Strengthened steels. The collective results indicate ZrO 2 as a potential alternate dispersoid for strengthening steel and future scope for vast exploration. 

https://link.springer.com/content/pdf/10.1007/s11665-023-08244-2.pdf

Microstructural Characterization of Novel ZrO_2 Dispersion-Strengthened 9Cr Steel by Spark Plasma Sintering

Summary and Future Directions

Surface modification techniques are extensively utilized to improve the performance of the engineering components in their service life when exposed to elevated temperatures. Herein, the Tribaloy 400 (T 400) particles were deposited on the 17-4 PH stainless steel through the spark plasma sintering (SPS) technique to improve the high-temperature wear resistance of exhaust valve components which are typically manufactured using 17-4 PH stainless steel. The identification of phases, microstructure and the morphology of phases in the coatings, elemental composition and distribution, interfacial behavior, and defects like porosities were investigated using advanced characterization techniques. The obtained results revealed the presence of FCC and HCP – Co along with 52 vol% of laves phases (CoMoSi). The presence of laves phases in the Co matrix, fine grained structure and superior interfacial bond strength were promoted the hardness of the coating (~885 HV) than the substrate (~363 HV). The ball-on-disc wear studies were carried out using alumina balls as counter material at room temperature and high temperature (650 °C). The T 400 coating specimen provided better wear properties than the substrate at both temperature. The specific wear rate obtained for the T 400 coated specimen and 17-4PH substrate at room temperature was found to be 1.29 × 10−5 mm3/Nm and 120 × 10−5 mm3/Nm, whereas at 650 °C, it was found to be 0.037 × 10−5 mm3/Nm and 10.26 × 10−5 mm3/Nm, respectively. In T 400 coating, the developed transparent oxide film at 650 °C decreased the possibilities for metal-to-metal contact between the specimen and the counterpart. 

Srinivasa R. Bakshi

Papers

Characterization Techniques for CNT-MMC Materials

Carbon Nanotube Reinforced Metal Matrix Composite (CNT-MMC) Systems

Microstructural Characterization of Novel ZrO_2 Dispersion-Strengthened 9Cr Steel by Spark Plasma Sintering

Summary and Future Directions

High temperature wear behavior of Tribaloy 400 deposited 17-4 PH stainless steel using spark plasma sintering