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

As a ubiquitous solar-thermal energy conversion process, solar-driven evaporation has attracted tremendous research attention owing to its high conversion efficiency of solar energy and transformative industrial potential. In recent years, solar-driven interfacial evaporation by localization of solar-thermal energy conversion to the air/liquid interface has been proposed as a promising alternative to conventional bulk heating-based evaporation, potentially reducing thermal losses and improving energy conversion efficiency. In this Review, we discuss the development of the key components for achieving high-performance evaporation, including solar absorbers, evaporation structures, thermal insulators and thermal concentrators, and discuss how they improve the performance of the solar-driven interfacial evaporation system. We describe the possibilities for applying this efficient solar-driven interfacial evaporation process for energy conversion applications. The exciting opportunities and challenges in both fundamental research and practical implementation of the solar-driven interfacial evaporation process are also discussed. The thermal properties of solar energy can be exploited for many applications, including evaporation. Tao et al. review recent developments in the field of solar-driven interfacial evaporation, which have enabled higher-performance structures by localizing energy conversion to the air/liquid interface.

Solar-driven interfacial evaporation

Photothermal materials with broad solar absorption and high conversion efficiency have recently attracted significant interest. They are becoming a fast-growing research focus in the area of solar-driven vaporization for clean water production. The parallel development of thermal management strategies through both material and system designs has further improved the overall efficiency of solar vaporization. Collectively, this green solar-driven water vaporization technology has regained attention as a sustainable solution for water scarcity. In this review, we will report the recent progress in solar absorber material design based on various photothermal conversion mechanisms, evaluate the prerequisites in terms of optical, thermal and wetting properties for efficient solar-driven water vaporization, classify the systems based on different photothermal evaporation configurations and discuss other correlated applications in the areas of desalination, water purification and energy generation. This article aims to provide a comprehensive review on the current development in efficient photothermal evaporation, and suggest directions to further enhance its overall efficiency through the judicious choice of materials and system designs, while synchronously capitalizing waste energy to realize concurrent clean water and energy production.

Solar absorber material and system designs for photothermal water vaporization towards clean water and energy production

Reducing human reliance on energy-inefficient cooling methods such as air conditioning would have a large impact on the global energy landscape. By a process of complete delignification and densification of wood, we developed a structural material with a mechanical strength of 404.3 megapascals, more than eight times that of natural wood. The cellulose nanofibers in our engineered material backscatter solar radiation and emit strongly in mid-infrared wavelengths, resulting in continuous subambient cooling during both day and night. We model the potential impact of our cooling wood and find energy savings between 20 and 60%, which is most pronounced in hot and dry climates.

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A radiative cooling structural material.

Challenges and Opportunities for Solar Evaporation

The invention discloses a processing method of yam flour. The method comprises the steps of soaking, namely putting yam which is peeled and sliced into a protection liquid and soaking for 3-4h, wherein the protection liquid comprises the formulation in parts by weight: 0.2-0.4 part of sodium sulfite and/or sodium pyrosulfite, 0.1-0.3 part of ascorbic acid and 100 parts of water; drying, namely placing soaked yam pieces in a dispersing way, and drying the yam pieces for 9-12h at the temperature of 70-80 DEG C; grinding, namely preparing the yam flour from the dried yam pieces. The method is simple in technological process, convenient to operate and low in production cost; the prepared yam flour not only reserves the original nutritive value of the yam, but also maintains the original white of the yam, so that the yam flour is attractive in appearance, can be used for preparing products separately, can be taken as a raw material and can be mixed with other substances so as to be prepare more nutrient products.

Processing method of yam flour

Rheological Properties of Film-Forming Solutions and Mechanical Properties of Edible Composite Films Based on Sodium Alginate, Sodium Carboxymethyl Cellulose and Gelatin

Cf–Al2O3/Cu composites were fabricated by introducing carbon fibers (Cfs) into Al2O3/Cu composite for further improvement of arc erosion resistance. The effect of Cf on the arc erosion behavior of the composites was discussed. It was revealed that a proper amount of Cf improved the arc erosion resistance of Cf–Al2O3/Cu composites. Compared with Al2O3/Cu composites, the arc energy of 5vol.% Cf–Al2O3/Cu composites decreased by up to 47.1%. The erosion morphology and elemental composition of the electrical contact surface under the action of arc were characterized. It was found that Cfs were easy to float on the molten pool surface during arc erosion due to the low density, which increased the viscosity of the molten pool and stabilized it. The Cfs were transferred preferentially compared with the Cu matrix, which reduced the loss of the matrix. Cfs retard the formation of anode surface bumps and avoided concentrated deterioration of arc erosion. 

Arc erosion resistance mechanism of Cf-Al2O3/Cu composites modified by carbon fibers

The Effects of Calcium Propionate and Cinnamaldehyde on the Mechanical, Physical and Antimicrobial Properties of Composite Films Based on Potato Starch

Carbon nanotubes were prepared in large quantities by fluidized bed method and nitrogen-doped carbon nanotubes were prepared by chemical vapor deposition method. Carbon nanotubes/5-amino-1H-tetrazole composites were prepared by ultrasonic resonance method. The appearance characteristics and thermal properties of composites were analyzed by scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetry (TG) and differential scanning calorimeter (DSC).

https://iopscience.iop.org/article/10.1088/1757-899X/213/1/012046/pdf

Chao Jia

Papers

Processing method of yam flour

Rheological Properties of Film-Forming Solutions and Mechanical Properties of Edible Composite Films Based on Sodium Alginate, Sodium Carboxymethyl Cellulose and Gelatin

Arc erosion resistance mechanism of Cf-Al2O3/Cu composites modified by carbon fibers

The Effects of Calcium Propionate and Cinnamaldehyde on the Mechanical, Physical and Antimicrobial Properties of Composite Films Based on Potato Starch

Preparation and thermal properties of carbon Nanotubes/5-Amino-1H-Tetrazole energetic composites