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

In this paper, experimental tests and theoretical studies were carried out to evaluate the tensile behavior of the sprayed FRP composite with chopped glass fiber. For this, a series of tensile strength tests with various strain rates were conducted on the specimens of the matrix and sprayed FRP composite. Sprayed FRP composite contained chopped glass fibers with fiber length of 15mm and a specific volume fraction of fibers of 25 %. An inverse simulation was conducted to simulate the strain rate sensitivity based on the present experimental data of the epoxy resin. The simulated viscosity value is adapted to the micromechanics-based viscoelastic damage model(Yang et al., 2012), and the overall tensile behavior of sprayed FRP composites is predicted. It was seen from the comparative study between present experimental data and predication results that the proposed methodology can be used to predict the viscoelastic behavior of the sprayed FRP composite.

Micromechanics-based Analysis on Tensile Behavior of the Sprayed FRP Composites with Chopped Glass Fibers

The present invention relates to: a cement composite comprising a carbon nanotube (CNT)to implement the high dispersion of a carbon nanotube in a cement matrix when preparing a cement composite by mixing a carbon nanotube with low dispersion in cement; a preparation method thereof; and a method for manufacturing a carbon nanotube-cement structure using the cement composite. According to the present invention, the preparation method of the cement composite comprises: (a) a step of mixing a carbon nanotube, silica fume, cement, and fine aggregate and dry mixing the same for a set amount of time; and (b) a step of adding water and a polycarboxylic acid-based superplasticizer to the dry-mixed mixture and mixing the same for a set amount of time.

Cement composite comprising carbon nanotube, preparation method thereof, and method for manufacturing carbon nanotube-cement structure using cement composite thereof

A Computational Approach for Prediction of the Performance of Concrete Beams Retrofitted with Sprayed Fiber Reinforced Polymers

A method for curing cementitious articles includes flowing dry steam and carbon dioxide (CO2) simultaneously into a curing chamber containing a cementitious article. A relative humidity within the curing chamber may be between about 50% and about 70% and a temperature within the curing chamber may be between about 50° C. and about 70° C. A dry steam and CO2 mixture with a CO2 concentration between 2.5 vol % and 40 vol % is provided in the curing chamber and the cementitious article is cured for a duration between about 4 hours and 16 hours. Cementitious products cured with the method may have a CO2 uptake of greater than 15 wt % and a mechanical strength at least 10% greater than a cementitious product cured only in dry steam or CO2.

Method for enhancement of mechanical strength and CO2 storage in cementitious products

An experimental study was conducted to investigate the structural behavior and performance of deep beams reinforced in shear with a honeycomb steel mesh (HSM). A series of four-point loading tests on five simply supported deep beams were carried out. The control beam was substantially deficient in shear strength, another beam was fully reinforced in shear by stirrups, and four other beams were reinforced with various configurations of HSM. The primary variables were the diagonal cell width and welding condition of the HSM. The shear behavior and performance of deep beams reinforced with various configurations of HSM were compared with those of the control beam and the beam reinforced in shear by stirrups. In this study, all of the tested deep beams failed in shear. Crack patterns and failure modes of the specimens were explained on the basis of the arch action. It was found from the test results that HSM was effective in reinforcing deep beams in shear. Further, the butt- welded HSM with a diagonal cell w...

Haeng-Ki Lee

Papers

Micromechanics-based Analysis on Tensile Behavior of the Sprayed FRP Composites with Chopped Glass Fibers

Cement composite comprising carbon nanotube, preparation method thereof, and method for manufacturing carbon nanotube-cement structure using cement composite thereof

A Computational Approach for Prediction of the Performance of Concrete Beams Retrofitted with Sprayed Fiber Reinforced Polymers

Method for enhancement of mechanical strength and CO2 storage in cementitious products

Shear Behavior and Performance of Deep Beams Reinforced with a Honeycomb Steel Mesh