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

How to effectively utilize low and medium temperature energy is one of the solutions to alleviate the energy shortage and environmental pollution problems. In the past twenty years, because of its feasibility and reliability, organic Rankine cycle has received widespread attentions and researches. In this paper, it reviews the selections of working fluids and expanders for organic Rankine cycle, including an analysis of the influence of working fluids' category and their thermodynamic and physical properties on the organic Rankine cycle's performance, a summary of pure and mixed working fluids' screening researches for organic Rankine cycle, a comparison of pure and mixture working fluids' applications and a discussion of all types of expansion machines' operating characteristics, which would be beneficial to select the optimal working fluid and suitable expansion machine for an effective organic Rankine cycle system.

A review of working fluid and expander selections for organic Rankine cycle

Annual Energy Outlook

Developing thermoelectric materials with superior performance means tailoring interrelated thermoelectric physical parameters – electrical conductivities, Seebeck coefficients, and thermal conductivities – for a crystalline system. High electrical conductivity, low thermal conductivity, and a high Seebeck coefficient are desirable for thermoelectric materials. Therefore, knowledge of the relation between electrical conductivity and thermal conductivity is essential to improve thermoelectric properties. In general, research in recent years has focused on developing thermoelectric structures and materials of high efficiency. The importance of this parameter is universally recognized; it is an established, ubiquitous, routinely used tool for material, device, equipment and process characterization both in the thermoelectric industry and in research. In this paper, basic knowledge of thermoelectric materials and an overview of parameters that affect the figure of merit ZT are provided. The prospects for the optimization of thermoelectric materials and their applications are also discussed.

A review on thermoelectric renewable energy: Principle parameters that affect their performance

The process chain of energy conversion from primary energy carriers to final energy use is subject to several losses. Especially in end use, vast amounts of converted energy occur as waste heat, which is often released to the environment. In terms of raising energy efficiency and reducing the energy consumption, such waste heat needs to be used. To date, some studies or investigations about industrial waste heat of selected countries have been carried out, but other sectors like commerce were not considered. Therefore, this work presents a novel top-down approach for the estimation of waste heat potential of the most common sectors of end use (transportation, industrial, commercial and residential) including electricity generation on a global scale. It also deals with the temperature distribution of this unused energy. The evaluation reveals that 72% of the global primary energy consumption is lost after conversion. In further detail, 63% of the considered waste heat streams arise at a temperature below 100 °C in which electricity generation has the largest share followed by transportation and industry.

Estimating the global waste heat potential

Measurements of Critical Properties for Carbon Dioxide (CO_2) + Propylene (R-1270) Binary Mixture

This paper proposes a new analytical approach to study the bending vibration of N step shafting system Changes of the shaft step properties under rotary condition are governed by two-dimensional wave equations The source of the bending vibration is first analysed Then strain and stress equations of the spinning shaft are established After Hamilton principle is applied, a two-dimensional wave equation is established After that, the calculation formula of one dimensional bending vibration response is obtained where a sinusoidal excitation force is applied on an arbitrary concentrated mass By using this formula, the total dynamic response can be obtained based on the principle of the linear superposition The calculated results were compared with measured results It was found they agree with each other in the vertical direction but not in the horizontal direction At the end of paper, the reason of difference is analysed

Analytical and Experimental Study on Bending Vibration of Internal Combustion Engines Shafting System Based on Wave Equations

Thermal and chemical effects of low-temperature chemistry on flame initiation and propagation

Selection maps of dual-pressure organic Rankine cycle configurations for engine waste heat recovery applications

A double-working-medium expansion machine suitable for a two-level organic Rankine cycle comprises an air cylinder body (2), a rotor (1) disposed in the air cylinder body (2) and provided with multiple slip sheets (4) in the radial direction, and a rotating shaft (5) fixedly connected to the center of the rotor (1). The air cylinder body (2) is of an integral annular structure formed in a manner that two semi-oval structures are in butt joint, wherein the lengths of the semi-major axes of the semi-oval structures are unequal while the lengths of the semi-minor axes of the semi-oval structures are equal. The outer circumference surface of the rotor (1) can be rotationally tangent to the inner circumference surface of the air cylinder body (2) at the butt joint position of the two semi-oval structures of the air cylinder body (2). A low-temperature-level cycle element volume (6) for expansion of a low-temperature-level, large-flow and small-expansion-ratio working medium and a high-temperature-level cycle element volume (7) for expansion of a high-temperature-level, small-flow and large-expansion-ratio working medium are formed between two sides of the rotor (1) and the air cylinder body (2) respectively. A first air inlet (8) and a second air outlet (9) communicated with the low-temperature-level cycle element volume (6) and a second air inlet (10) and a second air outlet (11) that are communicated with the high-temperature-level cycle element volume (7) are formed in the cylinder body wall of the air cylinder body (2). In the expansion machine, the two-level organic Rankine cycle is achieved and the two working mediums work in an expansion machine device.

Gequn Shu

Papers

Measurements of Critical Properties for Carbon Dioxide (CO_2) + Propylene (R-1270) Binary Mixture

Analytical and Experimental Study on Bending Vibration of Internal Combustion Engines Shafting System Based on Wave Equations

Thermal and chemical effects of low-temperature chemistry on flame initiation and propagation

Selection maps of dual-pressure organic Rankine cycle configurations for engine waste heat recovery applications

Double-working-medium expansion machine suitable for two-level organic Rankine cycle