The Experts below are selected from a list of 54819 Experts worldwide ranked by ideXlab platform
Yimin Xuan - One of the best experts on this subject based on the ideXlab platform.
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Biomimetic omnidirectional broadband Structured Surface for photon management in photovoltaic–thermoelectric hybrid systems
Solar Energy Materials and Solar Cells, 2016Co-Authors: Yutao Zhang, Yimin XuanAbstract:Abstract An advanced photon management approach is developed for a photovoltaic–thermoelectric hybrid system to increase the solar energy utilization efficiency. A biomimetic parabolic-shaped structure on the Si film and a thin SiO 2 film at the bottom of the Si film as back-antireflection coating improves the absorptance of photons with wavelengths of 0.3–1.1 μm, which can generate electron–hole pairs. Photons with wavelengths of 1.1–2.5 μm transmit through the Structured Surface and are absorbed by the thermoelectric modules, which improves the conversion efficiency of the entire hybrid system. The Structured Surface with graded refractive index can effectively harvest photons with wavelengths of 0.3–2.5 μm. The effects of the structural parameters and the incident angle on the spectral features of the Structured Surface are analyzed. The results indicate that the Structured Surface provides high omnidirectional absorptance for wavelengths of 0.3–1.1 μm and high transmittance for wavelengths of 1.1–2.5 μm as well as favorable polarization-insensitive features over a good incident angle range as a good candidate for the photovoltaic–thermoelectric hybrid systems.
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Perfect solar absorber based on nanocone Structured Surface for high-efficiency solar thermoelectric generators
Science China Technological Sciences, 2015Co-Authors: Yun Da, Yimin XuanAbstract:NanoStructured Surface is a promising photon management strategy to tune spectrum in design of the selective solar absorber. In this paper, we propose a nanocone Structured Surface as a perfect solar absorber in application of the solar thermoelectric generators (STEGs). The trade-off between the solar absorption and the mid-infrared emission is obtained to maximize the STEG efficiency. The effects of the geometric parameters, thermal concentration, incident angle and polarized state as well as the lattice arrangement are systematically investigated. The results show that the STEGs equipped with our proposed selective solar absorber can achieve a peak efficiency of 6.53% under AM1.5G condition (no optical concentration). Furthermore, the selective solar absorber exhibits insensitive behavior to the incident angle and polarization angle as well. This means that the proposed selective solar absorber can utilize solar energy as much as possible and be generally suitable in equipping the STEGs without optical concentration.
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Spectral Features of an Omnidirectional Narrowband Emitter
Journal of Heat Transfer-transactions of The Asme, 2012Co-Authors: Yutao Zhang, Yimin XuanAbstract:A microscale-Structured Surface consisting of heavily doped silicon rectangle grating and slotted silver layer is studied for omnidirectional narrowband emitter. Numerical simulation is implemented to obtain spectral emittance in mid-infrared region (6–16 μm) for the transverse magnetic incidence by using the rigorous coupled-wave analysis (RCWA) method. The effects of structural parameters and incident angle on its spectral emittance are investigated. In virtue of the microcavity effect, an omnidirectional narrowband emitter is proposed. By selecting a group of structural parameters, its peak emittance reaches as high as 0.998, and the peak width Δλ/λ of the emittance peak is as narrow as 0.03 at the specified wavelength. The results reveal that our proposed Structured Surface has the nice spectral features of angular uniformity and wavelength-selective characteristic, which can be applied to design novel narrowband thermal emitters and detectors in the infrared region.
Chang-pin Chou - One of the best experts on this subject based on the ideXlab platform.
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Experimental Study of a Silver Layer on an Antireflection Subwavelength-Structured Surface
IEEE Photonics Technology Letters, 2008Co-Authors: Chia-jen Ting, Chi-feng Chen, Chang-pin ChouAbstract:The optical characteristics of a silver layer deposited on an antireflection subwavelength-Structured Surface are investigated. The experimental results of the reflectance and the transmittance of several different thicknesses of silver layer on the subwavelength-Structured Surface are carried out. A subwavelength structure with the spatial period and diameter of about 230 nm and height of about 150 nm on polyethylene terphthalate film is fabricated by microreplication process. It is shown that such an element with the suitable silver layer deposited on an antireflection subwavelength-Structured Surface has high transmittance and low glare in the visible spectral range and high reflectance in the infrared range. Obviously, the optical film with silver layer can not only obtain the high performance of heat insulation but also give an application in automobile and house windows.
S Y Misyura - One of the best experts on this subject based on the ideXlab platform.
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heat transfer of aqueous salt solutions during evaporation on a Structured heated wall
International Communications in Heat and Mass Transfer, 2018Co-Authors: S Y MisyuraAbstract:Abstract Evaporation and heat transfer of the layers of water and aqueous salt solutions (H 2 O/LiBr, H 2 O/CaCl 2 , H 2 O/LiCl) have been studied experimentally. Evaporation rate is greater for a Structured wall than for a smooth one. When simulating droplet evaporation and heat transfer, it is necessary to take into account free convection of air and vapor. There is a change of the heat transfer coefficient for salt solutions layers on the Structured Surface with the presence of an extremum. The largest value of the heat transfer coefficient α on the Structured Surface corresponds to water for the final stage of evaporation. For salt solutions, α is lower than that of water. The maximum excess of heat transfer coefficient of micro-Structured wall above the smooth wall (20–25%) corresponds to the maximum height of the liquid layer for the initial period of evaporation. With increasing time, the excess is reduced.
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contact angle and droplet heat transfer during evaporation on Structured and smooth Surfaces of heated wall
Applied Surface Science, 2017Co-Authors: S Y MisyuraAbstract:Abstract Water evaporation in a wide range of droplet diameters and wall temperatures on the Structured and smooth Surfaces were studied experimentally. Linear dependence of evaporation rate ( dV / dt ) on a droplet radius varies when the volume is greater than 40–60 μl. The static contact angles on the Structured Surface vary with a droplet diameter for high wall superheating. Dependence of the contact angle on diameter for the corrugated Surface is defined by a change in both potential energy barrier U and three-phase contact line tension τ cl . This energy barrier for the Structured wall changes with an increase in the initial droplet diameter and becomes constant for the large droplets. For high wall superheating, the power in the law of evaporation increases from 1 to 1.45 with an increase in the initial droplet diameter. Depending on the droplet radius, number of droplets and heater length, four different characters of evaporation are realized. Complete droplet evaporation time on Structured Surface is less than smooth wall. Heat transfer coefficient is greater for Structured wall than smooth one. When simulating droplet evaporation and heat transfer, it is necessary to take into account free convection of air and vapor.
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contact angle and droplet evaporation on the smooth and Structured wall Surface in a wide range of droplet diameters
Applied Thermal Engineering, 2017Co-Authors: S Y MisyuraAbstract:Abstract Droplet evaporation in a wide range of initial volumes of 1–1000 μl on the Structured and smooth Surfaces was studied experimentally. It is found that the static contact angle on the Structured Surface for the steady equilibrium depends on the droplet shape and initial diameter; it has an extreme. With the increasing wetting diameter of water samples from 2 to 30 mm, the contact angle increases first, reaches a maximum, then decreases and tends to a constant value. To determine the contact angle, the authors have performed the comparisons by different methods in a wide range of droplet sizes. A wide range of droplet sizes is usual for spray cooling. Approximation dependences for determining droplet volume were obtained in a wide range of droplet sizes. For the droplets with the initial diameter less than 1 mm, middle and large droplets, as well as for the small initial contact angles and angles of about 85–90°, different kinetics of evaporation will be observed. Kinetics of droplet evaporation on the Structured Surface differs from evaporation on a smooth wall. Dimensionless Fourier number (Fo), derived by the initial droplet diameter and total time of evaporation, decreases with an increase in the wall temperature and initial droplet diameter. For large droplet diameter and a high wall superheating the derivatives d(Fo)/d(Tw) and d(Fo)/d(d0) tend to zero.
Chia-jen Ting - One of the best experts on this subject based on the ideXlab platform.
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Heat-insulation film with gold layer deposited on antireflection subwavelength-Structured Surface
Optik, 2010Co-Authors: Chia-jen Ting, Chi-feng Chen, Chin-ju HsuAbstract:Abstract The optical properties of gold layer deposited on antireflection subwavelength-Structured Surface are first exposed. The experimental results of the reflectances and transmittances for several different thicknesses of gold-deposited layers on the subwavelength structures are carried out. The nanoStructured Surface with spatial period and a diameter of about 230 nm and height of about 150 nm on polyethylene terphthalate (PET) film is fabricated by micro-replication process of UV imprinting. Comparing these with the bare gold-deposited layer and bare nanostructure, the results show that the optical films with the suitable gold layer deposited on antireflection subwavelength-Structured Surface has high transmittance and low glare in the visible spectral range and high reflectance in the infrared range. That is to say, when the antireflection subwavelength-Structured Surface is coated with a gold layer of several tens of nm thickness, it will have some unique optical characters.
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Experimental Study of a Silver Layer on an Antireflection Subwavelength-Structured Surface
IEEE Photonics Technology Letters, 2008Co-Authors: Chia-jen Ting, Chi-feng Chen, Chang-pin ChouAbstract:The optical characteristics of a silver layer deposited on an antireflection subwavelength-Structured Surface are investigated. The experimental results of the reflectance and the transmittance of several different thicknesses of silver layer on the subwavelength-Structured Surface are carried out. A subwavelength structure with the spatial period and diameter of about 230 nm and height of about 150 nm on polyethylene terphthalate film is fabricated by microreplication process. It is shown that such an element with the suitable silver layer deposited on an antireflection subwavelength-Structured Surface has high transmittance and low glare in the visible spectral range and high reflectance in the infrared range. Obviously, the optical film with silver layer can not only obtain the high performance of heat insulation but also give an application in automobile and house windows.
K Lu - One of the best experts on this subject based on the ideXlab platform.
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fabrication of a gradient nano micro Structured Surface layer on bulk copper by means of a Surface mechanical grinding treatment
Scripta Materialia, 2008Co-Authors: Wang Li, N R Tao, K LuAbstract:[Li, W. L.; Tao, N. R.; Lu, K.] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Liaoning, Peoples R China.;Tao, NR (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Liaoning, Peoples R China;nrtao@imr.ac.cn
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low temperature plasma nitriding of aisi 304 stainless steel with nano Structured Surface layer
Zeitschrift Fur Metallkunde, 2003Co-Authors: H. W. Zhang, Jian Lu, L. Wang, K LuAbstract:A nanoStructured Surface layer was produced on an AISI 304 stainless steel plate by means of a Surface mechanical attrition treatment (SMAT). Low-temperature plasma nitriding of the SMAT stainless steel sample was investigated in comparison with the coarse-grained sample by using structural analysis (X-ray diffraction, scanning electron microscopy, and transmission electron microscopy) as well as mechanical property measurements. It shows a much thicker nitrided layer is formed on the SMAT sample relative to that in the coarse-grained counterpart nitrided under the same condition. The nitrided layer in the SMAT sample is composed of nanoStructured austenite expansion and martensite expansion with high supersaturations of nitrogen. The Surface hardness and the hardened Surface layer thickness, as well as the abrasive and the adhesive wear resistances of the nitrided SMAT sample are much enhanced relative to the nitrided coarse-grained sample.
