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

비만아 부모의 돌봄 경험: q 방법론

Challenges and Opportunities for Solar Evaporation

Emerging desalination technologies for water treatment: a critical review.

Performance evaluation of external compound parabolic concentrator integrated with thermal storage tank for domestic solar refrigeration system

Experimental investigations of the hemispherical solar still (HSS) augmentation with various numbers of evacuated tubes (EVT) were performed and evaluated. The modified hemispherical solar still (HSS-EVT) performance was illustrated with two categories of EVT distributions and compared with the traditional HSS (THSS) design. In the first category, the EVT was distributed on the water basin perimeter in all directions (Dis-ɸ), and in the second category, the EVT was distributed in the south direction (Dis-So). The impact of various water heights (Hw) from 1 to 4 cm was also studied. Results revealed that the integration of EVT had a significant influence on distillate performance. The highest daily production rate at 1 cm water height of HSS-EVT was 5860 mL with an increment of 551, 316, 156, and 91% compared to THSS at NEVT = (16, 8, 4, and 2 tubes), respectively. The productivity increment by 7.2%, when compared EVT distribution (Dis-ɸ) with (Dis-So) effect. The reduction of water level to 1 cm increases the yield by about 5.96, 11.61, and 18.74% with HW (2, 3, and 4 cm), respectively. The proposed system's peak energy and exergy efficiency value was 42.29 and 5.57%, with an increment of 47.30 and 124%, respectively, related to the traditional one. The maximum daily production related to the exposed surface area was 6.69 L/m2 at NEVT = 8 tubes. The estimated cost varied between 0.00237, and 0.0101 USD/L. 

Thermo-economic performance enhancement of the hemispherical solar still Integrated with various numbers of evacuated tubes

In this paper, a comparative study between modified solar stills (with graphite or copper oxide micro/nano particles) and classical solar still is carried out, based on the productivity and the thermal performance. Exergy destructions in various components of the solar stills have been calculated, analyzed and discussed. Evaporation is faster and the exergy of evaporation is higher at the modified solar stills than that of the classical one. Furthermore, the energy and exergy efficiencies of the modified stills are enhanced compared with the classical one. A brief discussion regarding the effect of different parameters on solar stills efficiency is also presented. The daytime energy efficiency of graphite/water and copper oxide/water mixtures are 41.18% and 38.61%, respectively, but for the classical still is only 29.17%. Moreover, the daytime exergy efficiencies of graphite, copper oxide nanofluid based stills and classical still are 4.32%, 3.78% and 2.63%, respectively.

Energy and exergy analysis of solar stills with micro/nano particles: A comprehensive study

This study investigates the thermohydraulic characteristics of immiscible two-phase downward flow and heat transfer through porous media in a vertical, cylindrical, and homogeneous porous medium numerically and experimentally. The test section is exposed to a constant wall temperature after filled with spherical beads. Numerical solution of the model is achieved by the finite volume method and applied to a single-phase flow model. The numerical results are experimentally validated according to air/water downward flow, spherical beads, a ratio of particle diameter to pipe radius is 0.412, 0.396 porosity, 0.01 ≤ Re ≤ 500, water to air volume ratio range from 0 to ∞, and saturation ratio from 0 to 1. The results show that the average Nu is nearly constant up to Re = 40. At Re > 100, it is recommended to take inertia and friction effects into account by means of Forchheimer–Brinkman’s equation. For single-phase flow (water or air) and two-phase flow mixtures, the local Nu has higher values at the entrance section and decreases as the axial distance increases until it reaches its fully developed value of 4.37 at the end of the thermal entrance length. The comparison between numerical, experimental, and other available previous results shows good agreement and validates the numerical model. 

Swellam W. Sharshir

Papers

Performance evaluation of external compound parabolic concentrator integrated with thermal storage tank for domestic solar refrigeration system

Thermo-economic performance enhancement of the hemispherical solar still Integrated with various numbers of evacuated tubes

Energy and exergy analysis of solar stills with micro/nano particles: A comprehensive study

A simplified model of low Re, immiscible, gas–liquid flow, and heat transfer in porous media numerical solution with experimental validation

Thermal performance augmentation of parabolic trough solar collector using nanomaterials, fins and thermal storage material