Search

Electron transmission through semiconductor superlattices is studied with transfer matrix method and resonance theory. The formation of electron band-pass transmission is ascribed to the coupling of different modes in those semiconductor superlattices with the symmetric unit cell. Upon Fabry-P\'erot resonance condition, Bloch modes and two other resonant modes are identified to be related to the nature of the superlattice and its unit cell, respectively. The bands related to the unit cell and the superlattice overlap spontaneously in the tunneling region due to the shared wells, and the coupling of perfectly resonances results in the band-pass tunneling. Our findings provide a promising way to study electronic systems with more complicated superlattices or even optical systems with photonic crystals., Comment: 15 pages, 4 figures

Summary This paper introduces the methods of integration of solar energy and low-temperature solid oxide fuel cells. On the one hand, we design the system that integrates the solar photovoltaic cells and fuel cells. On the other hand, solar energy is concentrated to heat up the fuel cell and supply the working temperature at hundreds Celsius degrees by Fresnel lens. Then the fuel conversion efficiency is increased because of gain from the solar energy. Moreover, integration of solar thermal energy power system with the fuel is a good method for resolving the instability of solar energy. CHP (combined heat and power) is another aspect to enhance the design hybrid system overall efficiency. Finally, we present a novel device but built on different scientific principle. It can convert solar energy and chemical energy of fuel to electric energy simultaneously within the same device to integrated solar cell and fuel cell from the device level. Copyright © 2016 John Wiley & Sons, Ltd.

Solid oxide fuel cell (SOFC) represents a clean electrochemical energy conversion technology with characteristics of high conversion efficiency and low emissions. It is one of the most important new energy technologies in the future. However, the manufacture of SOFCs based on the structure of anode/electrolyte/cathode is complicated and time-consuming. Thus, the cost for the entire fabrication and technology is too high to be affordable, and challenges still hinder commercialization. Recently, a novel type of electrolyte-free fuel cell (EFFC) with single component was invented, which could be the potential candidate for the next generation of advanced fuel cells. This paper briefly introduces the EFFC, working principle, performance, and advantages with updated research progress. A number of key R&D issues about EFFCs have been addressed, and future opportunities and challenges are discussed.

軟質木材の有効利用を目的として，中国山東省産の毛白楊（Populus tomentosa Carr.）の板目材を用いて層状圧縮の方法，圧縮材の密度分布，硬さの変化及び表面密度と硬さの関係について検討した。木材の水分と予熱時間をコントロールすることによって，木材の表層から中央部までの任意の位置において一つあるいは二つの圧縮層を得ることができた。同じ圧縮材の中の非圧縮層の平均密度は0.61～0.65g/cm3で，圧縮層の平均密度は0.79～0.89g/cm3であった。圧縮層の位置によってその密度も異なった。圧縮層が表面にある場合，その密度と硬さは最も高く，対照に比べてそれぞれ78.1％と127.6％向上し，最大密度は1.00g/cm3に達した。圧縮層が中央部にある場合，その平均密度は対照に比べて57.1％向上した。層状に圧縮された木材の表面硬さは表面密度に対して指数関数的に増大した。

Mn-Zn spinel ferrites were synthesized by sol-gel method. Effects of calcined temperature on structure and particle size of MnZnFe 2 C 4 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicate that the ultra fine Mn-Zn ferrite exhibits a spinel crystal structure. SEM images show that the powder fired at 900 °C for 2 h has an average diameter of 60 ∼ 90 nm. The particle size becomes larger with the increasing of calcined temperature and the distribution of particle becomes even more homogeneous. Sintering behaviors of synthesized ferrite powders depend on the powder characteristics and high temperatures have induced the good crystallization of particles.

The parabolic-trough solar concentrator is the key component in parabolic-trough solar thermal power plants. The parabolic-trough solar concentrator is designed in this paper. It was analyzed under operational condition and under snow load. The model of the coefficient of accumulated snow with the different rotational angle is established. The coefficient was calculated with the model for a parabolic-trough solar system in Nanjing China. And the optimal position is gotten by the analysis of the coefficient. Finally, the equivalent stress and the deformation of the concentrator were simulated under the operational position and under snow load. The concentrator meets the design requirements of the stress and the deformation. As a result, the optimal position for avoiding snow is right by the contrast to the waiting position. The proposed concentrator model of accumulated snow will lay a solid foundation for designing the parabolic-trough solar concentrator.

Vacuum solar receiver is the key component in parabolic trough solar system. Due to different expansion increment between metal absorber and glass, corrugated expansion joint (metal bellows) is necessary to compensate the extra expansion increment. The mechanical and thermal properties of metal bellows have significant influence on the reliability and heat loss of solar receiver. Recently, China's first high temperature vacuum receiver has been developed and produced by Southeast University and Sanle Electronic Group. This paper analyzes the fatigue properties from displacement compensation, stress assessment and axial elasticity. First, varies stresses of metal bellow when compensating for axial displacement is calculated, and the reliability of bellow is analyzed from the point of stress condition and fatigue life. Because metal bellows will reduce the effective absorbing length, metal bellow should be shortened under the precondition of enough axial compensation. Second, the axial compensation of bellow is a primary factor in design. This paper deduces a simple equation to calculate the maximum axial compensation of single wave for the toroidal bellows, and the calculation proves the compensation of the bellow designed meets the receiver requirement. Finally, the experimental measurements verify it has a good fatigue property.

In 2005, Hohai university and Nanjing Chunhui science & technology Ltd. of China, cooperating with Weizmann Instituted of Science and EDIG Ltd. of Israel, built up a 70kWe solar power tower test plant in Nanjing, Jiangsu province, China, which was regarded as the first demonstration project to demonstrate the feasibility of solar power tower system in China. The system consists of heliostats field providing concentrated sunlight, a solar tower with a height of 33 meter, a pressured cavity-air-receiver transforming solar energy to thermal energy, a modified gas turbine adapting to solar power system, natural gas subsystem for solar-hybrid generation, cooling water subsystem for receiver and CPC, controlling subsystem for whole plant, et al.. In this system, air acts as actuating medium and the system works in Brayton cycle. Testing results show that solar power tower system is feasible in China. To promote the development of solar powered gas turbine system and the pressured cavity-air-receiver technology in China, it is necessary to study the mechanical design for pressured Cavity-air-receiver. Mechanical design of pressured cavity-air-receiver is underway and some tentative principles for pressured cavity-air-receiver design, involving in power matching, thermal efficiency, material choosing, and equipment security and machining ability, are presented. At the same time, simplified method and process adapted to engineering application for the mechanical design of pressured cavity-air-receiver are discussed too. Furthermore, some design parameters and appearance of a test sample of pressured cavity-air-receiver designed in this way is shown. It is appealed that, in China, the research in this field should be intensified and independent knowledge patents for pivotal technological equipments such as receiver in solar power tower system should be formed.

The photovoltaic (PV) cells suffer efficiency drop as their operating temperature increases especially under high solar intensity levels, so cooling of cells is one of the main concerns when designing concentrating photovoltaic systems. Air-cooling, either by forced or natural flow, presents non-expensive and simple method of PV cooling. This paper presents the use of an active air-cooling system as heat transfer augmentation in a low concentrating photovoltaic solar collector to improve its overall performance. A detailed description of this cooling system is given. Based on the experimental platform, the forced air-cooling concentrating photovoltaic solar cell system was investigated experimentally. The daily temperature profile of the solar cells rear surface and the output electric power are presented confirming the contribution of this cooling method in increasing system P-V transfer efficiency and data of the solar cells with no concentration system tested simultaneously.

The first solar power tower system in China was constructed by the joint cooperation of Hohai University and Nanjing Chunhui Science & Technology Industrial Co., Ltd.. This system has been completed and succeeded in generating electricity in Oct. 2005. The power capability is 70kW. The system adopts the international advanced technical, among which the heliostat owns absolutely independent intellectual property right with excellent performance and economical price; the receiver adopted is cavity-styled receiver; the used power-generating system is gas turbine generating set, in accordance with the trend of ‘combined cycle’ development in the future.

This article introduces heat-pipe technologies, heat-pipe type vacuum absorber tubes; the design of several heat-pipe type vacuum absorber tubes; and the application of the heat-pipe type vacuum absorber tubes in parabolic trough solar thermal power generation system. a new dish system (sphere dish) has been developed. This system does not use the revolving parabolic mirror but the two-axis tracking sphere-shaped mirror which can form a conical focus belt in the central axis where a heat-pipe type vacuum absorber tubes is placed. the heat-pipe vacuum absorber tubes instead of cavity receiver which is used in parabolic trough system, has avoided the technical crux and brought down the cost. water can be directly used in the system as the absorbing medium(DSG) to generate electricity.

A new type solar vacuum absorber tube has been developed, and the tensile tests have shown the high reliability of the joint between the metal and glass of the vacuum absorber tube; the fatigue tests have indicated that the bellows of the vacuum absorber tube as well as the interface between the metal and glass can last for as long as 20 years; the weathering tests of the sample, have lasted for an entire year, which proves that the tube design is scientifically and reasonably devised.

This paper introduces the principle and characteristics of a sunlight tracking sensor. Application of the sunlight tracking sensor in optical fiber sunlight illuminating device is introduced too.

This paper describes some of optimizitions in high speed photography, such as optimizing the aperture width for each image speed of a studed object in a rotating mirror framing camera, optimizing the rotating mirror speed for each slit width in a smear camera, optimizing designs of a rotating mirror camera and intermittentmechanism in a intermittent camera through the differentiation and calculation by means of computer, and selecting the optimiz-ed photographic frequence in the application of high speed camera. Finally, we deduce it is possible that smear cameras can be partially replaced with the framing camera through the data processing in some cases.