[en] Highlights: • We designed a PV/T system running in the mode of natural circulation. • We established a simulation model of the system with MATLAB simulation software. • The experimental data was compared with simulation results. • The performance of the system was researched. - Abstract: Because of the high resistance caused by photovoltaic-thermal (PV/T) systems, the improved electrical energy due to fluid’s cooling is much less than energy consumption of pump. To avoid this problem, in this paper, a natural circulation tube plate PV/T system is designed and built in photovoltaic solar simulation laboratory of Tianjin Chengjian University. The circulation velocities, electrical efficiencies, thermal efficiencies, overall efficiencies, and primary energy economic ratios are tested and analyzed under different radiation intensities. The result shows that the operation of the natural circulation PV/T system has hysteresis, and it requires longer time to keep the system operating with higher and stable performance when radiation intensity is at low levels. A mathematical model of heat transfer for this PV/T system has been established and solved using the MATLAB, and the numerical results have been validated by experimental data. The overall efficiency of the system under the pattern of natural circulation is also calculated when used in hot summer and warm winter areas. The generated electricity is about 1281.5 MJ/year; the heat collection is about 4639.6 MJ; and the annual integrative efficiency is 60%.

[en] The complex coupling relationship between liquid sodium and concrete materials affects both the sodium fire characteristics and concrete properties through heat and chemical erosion. In this study, experiments on direct and indirect (separated by a steel plate) contact of the columnar sodium fire with the concrete surface were performed. It was found that the combustion efficiency of liquid sodium in direct contact with concrete was significantly enhanced and accompanied by intermittent explosions and splashing of small concrete fragments. The sodium fire on the surface of the concrete considerably increased the internal temperature, pore size, and distribution density of the concrete. In addition, the depth of influence on the loosening of the concrete structure was also greatly extended. The contact of liquid sodium with the concrete substantially affected its permeability resistance. The water absorption of the concrete surface was increased by more than 70% when liquid sodium directly impacted the bare concrete surface. However, the change in water absorption in the centre of the concrete was primarily affected by the duration of the external heat

[en] Atomic structure is the basis for deep understanding of various physical and chemical properties of condensed matter. In recent years, with the rapid development of global optimization algorithms and first-principles methods, it has become possible to determine or predict the atomic structure through theoretical calculations with only information about the chemical composition and external conditions. This article will briefly introduce the basic principles of current theoretical structure prediction methods, with particular emphasis on the swarm-intelligence based CALYPSO method and its applications. (authors)

[en] In under-dense plasma, the equation of the scattered laser with the multi-photon nonlinear Compton effect is given with higher-order-relativistic (HOR) effect. The effects of the propagation on the scattered laser in the plasma channel are studied with HOR effect. A shallower potential well also exists for photon spot size in the paraxial approximation. HOR effect decreases the amplitude of photon spot size oscillation whereas accelerates its rate. Furthermore, it prevents the singularity of infinite intensity of photon beam when photon beam power is greater than or equal to the relativistic critical power. The condition of balance-solution of the beam spot size is also given. (authors)

[en] Due to the width limitation of 8-bit data used in traditional display device, the local details and contrast of the infrared image are compressed. To cope with these limitations, a novel infrared image enhancement method based on CLAHE and multi-scale approach of DoG is proposed. First, the guided image filter is utilized to separate the base layer and detail layer of the image. Then, the improved CLAHE is used to adjust the base layer global contrast and the multi-scale detail boosting is used to enhance the detail features; for the detail layer, multi-scale fast median filter is used for noise reduction. Finally, the two layers are fused according to the weight of the detail layers’ noise level. Comparing with the real-time enhancement methods both in qualitative and quantitative aspects, our proposed method shows the better performance in experiment results. (paper)

[en] Highlights: • Two dimensional model of IEC with condensation is established. • The model is validated by visualized experiment. • The IEC performance under various conditions is investigated. • The water consumption of IEC is evaluated. -- Abstract: The indirect evaporative cooling (IEC) is regarded as a low-carbon and energy efficient technology to reduce the cooling load of an air conditioning system. However, in hot and humid areas, condensation might take place in fresh air channels of IEC unit. Although the heat and mass transfer model of one-dimensional counter flow IEC has been established with consideration of condensation from fresh air. However, the two-dimensional cross flow IEC model considering condensation has seldom been investigated and experimentally validated. Therefore, this paper presents a two-dimensional analytical model of cross-flow IEC considering condensation from fresh air. FEM (Finite Element Method) is used to solve the model. Besides, a test rig with visualized air channel has been designed to verify the accuracy of the developed model. The performance of IEC unit and its visualized condensation behavior under various conditions were intensively studied. The results show that the condensation is more likely to take place near the outlet of fresh air and inlet of exhaust air in cross-flow IEC unit. The latent heat transfer could reach up to 3.9 kW and around 30% moisture content of fresh air would be removed under full condensation states. The water consumption in IEC unit depends on the total heat transfer rate and ranges from 1.2 L/h to 6.6 L/h under various operating conditions.

[en] We report a condensation behavior of silver aggregates on silicone oil surfaces. The deposited Ag atoms diffuse and aggregate on the oil surface, and then form granular clusters and ramified islands. The apparent Ag coverage of the total area increases linearly with the nominal film thickness h for h < 0.9 nm. However, the coverage exhibits a fluctuation behavior for 1.0 nm < h < 2.5 nm. it is found that the anomalous behavior of the coverage is resulted from a characteristic material condensation process in the aggregates

[en] The s-polarized surface plasmon polaritons (SPPs) at the interface between dielectric and metamaterial are studied, and the dispersion relations of SPPs are also presented. Using the prism coupling mechanism, we obtain the attenuated total reflection (ATR) spectra in the frequency regime based on the Otto configuration. It is found that the thickness of the dielectric in the configuration and the small damping of the metamaterial affect the coupling strength significantly without changing the coupling frequency. Furthermore, the optimized thickness of the dielectric decreases with a larger damping, and the coefficient F of the metamaterial also determines the coupling frequency and strength. (physics of gases, plasmas, and electric discharges)

[en] Structure prediction methods have been widely used as a state-of-the-art tool for structure searches and materials discovery, leading to many theory-driven breakthroughs on discoveries of new materials. These methods generally involve the exploration of the potential energy surfaces of materials through various structure sampling techniques and optimization algorithms in conjunction with quantum mechanical calculations. By taking advantage of the general feature of materials potential energy surface and swarm-intelligence-based global optimization algorithms, we have developed the CALYPSO method for structure prediction, which has been widely used in fields as diverse as computational physics, chemistry, and materials science. In this review, we provide the basic theory of the CALYPSO method, placing particular emphasis on the principles of its various structure dealing methods. We also survey the current challenges faced by structure prediction methods and include an outlook on the future developments of CALYPSO in the conclusions. (topical review)

[en] Nonlinear magnetohydrodynamic (MHD) simulations of an equilibrium on the J-TEXT tokamak with applied resonant magnetic perturbations (RMPs) are performed with NIMROD (non-ideal MHD with rotation, open discussion). Numerical simulation of plasma response to RMPs has been developed to investigate magnetic topology, plasma density and rotation profile. The results indicate that the pure applied RMPs can stimulate 2/1 mode as well as 3/1 mode by the toroidal mode coupling, and finally change density profile by particle transport. At the same time, plasma rotation plays an important role during the entire evolution process. (paper)