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

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 extensive development of electronic systems and telecommunications has lead to major concerns regarding electromagnetic pollution. Motivated by environmental questions and by a wide variety of applications, the quest for materials with high efficiency to mitigate electromagnetic interferences (EMI) pollution has become a mainstream field of research. This paper reviews the state-of-the-art research in the design and characterization of polymer/carbon based composites as EMI shielding materials. After a brief introduction, in Section 1, the electromagnetic theory will be briefly discussed in Section 2 setting the foundations of the strategies to be employed to design efficient EMI shielding materials. These materials will be classified in the next section by the type of carbon fillers, involving carbon black, carbon fiber, carbon nanotubes and graphene. The importance of the dispersion method into the polymer matrix (melt-blending, solution processing, etc.) on the final material properties will be discussed. The combination of carbon fillers with other constituents such as metallic nanoparticles or conductive polymers will be the topic of Section 4. The final section will address advanced complex architectures that are currently studied to improve the performances of EMI materials and, in some cases, to impart additional properties such as thermal management and mechanical resistance. In all these studies, we will discuss the efficiency of the composites/devices to absorb and/or reflect the EMI radiation.

Polymer/carbon based composites as electromagnetic interference (EMI) shielding materials

Geopolymer concrete: A review of some recent developments

Piezoelectric characteristics of urethane composites incorporating piezoelectric nanomaterials

This article presents results of an experimental study conducted to investigate the influence of fiber volume fraction, fiber type, and presence of fly ash on mechanical properties of fiber-reinforced, lightweight aggregate, cellular concrete (FRLACC). Steel fibers are added at Vf of 0.5, 1.0, and 1.5%, and 25% of cement weight is replaced with fly ash in the control and FRLACC specimens that had shown the highest compressive strength in our preceding work. With the addition of 0.5% Vf of fibers, the increase in compressive strength of the polypropylene FRLACC specimens is slightly higher than that of the steel FRLACC specimens, whereas decreases in their peak load and modulus of rupture over those of control specimens are observed. The findings of the experimental study also show that the utilization of 25% fly ash is more efficient in improving the mechanical properties of the steel FRLACC specimens than those of the polypropylene FRLACC specimens.

https://journals.sagepub.com/doi/pdf/10.1177/0731684409103702

Influence of Fiber Volume Fraction and Fiber Type on Mechanical Properties of FRLACC

The development of a binder system with a lower carbon footprint as an alternative to Portland cement has been intensely researched. In the present study, alkali-activated fly ash exposed to carbon dioxide at an early age was characterized in compressive strength tests and by MIP, XRD and FT-IR analyses. The compressive strength of carbonated specimens experienced a dramatic increase in comparison to uncarbonated specimens. The microstructural densification of the carbonated specimens was evidenced by MIP. The XRD pattern showed peaks assigned to nahcolite, indicating that the pH was lower in the carbonated specimens. Under the carbon dioxide-rich environment, the aluminosilicate gel reached a more Si-rich state, which improved the mechanical properties of the alkali-activated fly ash.

/pdf/strength-development-of-alkali-activated-fly-ash-exposed-to-3uslb6cqzz.pdf

Strength Development of Alkali-Activated Fly Ash Exposed to a Carbon Dioxide-Rich Environment at an Early Age

Bond characteristics of SFRP composites containing FRP core/anchors coated on geopolymer mortar

This paper presents results of an experimental study conducted to investigate the effect of volume fraction of fibers on the mechanical properties of a fiber-reinforced, lightweight aggregate concrete(FRLAC) that was produced without an autoclave process. The FRLAC enhanced the strength of lightweight, cellular concrete by adding polypropylene fibers and lightweight aggregates. To investigate the effect of volume fraction of fibers on the mechanical behavior of FRLAC and to determine the optimal volume fraction of fibers, a series of compression and flexural strength tests on FRLAC specimens with various fiber volume fractions(0%, 0.10%, 0.25%, 0.50%) were conducted. It was observed from the tests that a 0.25% volume fraction of fibers maximized the increase in the strength of FRLAC and the fibers controlled cracking in FRLAC.

http://www.koreascience.or.kr:80/article/JAKO200625522713595.pdf

Haeng-Ki Lee

Papers

Piezoelectric characteristics of urethane composites incorporating piezoelectric nanomaterials

Influence of Fiber Volume Fraction and Fiber Type on Mechanical Properties of FRLACC

Strength Development of Alkali-Activated Fly Ash Exposed to a Carbon Dioxide-Rich Environment at an Early Age

Bond characteristics of SFRP composites containing FRP core/anchors coated on geopolymer mortar

Effect of Volume Fraction of Fibers on the Mechanical Properties of a Lightweight Aggregate Concrete Reinforced with Polypropylene Fibers