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The development of a method to simulate desired approach turbulence characteristics and improve the typhoon resistance ability for complex building and transmission tower-line system in a multiple controlled fan wind tunnel is described. A case study is investigated using a closed-circuit single controlled fan wind tunnel model of the Full-Scale Test Facility at the State Grid Fujian Electric Power Research Institute for State Grid Wind Tunnel Laboratory. A small-scale model of the closed-circuit single controlled fan wind tunnel is designed and established to simulate the turbulence characteristics and develop the target turbulent flow generating methods efficiently. The results reveal that the value of the maximum average wind speed can reach 18.2 m/s and the maximum circular frequency is 7 Hz. Here, the mean wind speed of the sinusoidal wave flow is 15.1 m/s at the peak of amplitude of 3.8 m/s. The generated sinusoidal wave flow has a high correlation coefficient at 94.3% with the target. [ABSTRACT FROM AUTHOR]

Based on measurement of the volume increment of polar liquid that is a result of heating by absorbed microwave energy, two types of calorimeters with coaxial capacitive probes for measurement of high-power microwave energy are designed in this paper. The first is an "inline" calorimeter, which is placed as an absorbing load at the end of the output waveguide, and the second is an "offline" calorimeter that is placed 20 cm away from the radiation horn of the high-power microwave generator. Ethanol and high density polyethylene are used as the absorbing and housing materials, respectively. Results from both simulations and a "cold test" on a 9.3 GHz klystron show that the "inline" calorimeter has a measurement range of more than 100 J and an energy absorption coefficient of 93%, while the experimental results on a 9.3 GHz relativistic backward-wave oscillator show that the device's power capacity is approximately 0.9 GW. The same experiments were also carried out for the "offline" calorimeter, and the results indicate that it can be used to eliminate the effects of the shock of the solenoid on the measurement curves and that the device has a higher power capacity of 2.5 GW. The results of the numerical simulations, the "cold tests," and the experiments show good agreement. [ABSTRACT FROM AUTHOR]

Concentrator photovoltaic is an emergent technology that may be a good economical and efficient alternative for the generation of electricity at a competitive cost. However, the reliability of these new solar cells and systems is still an open issue due to the high-irradiation level they are subjected to as well as the electrical and thermal stresses that they are expected to endure. To evaluate the reliability in a short period of time, accelerated aging tests are essential. Thermal aging tests for concentrator photovoltaic solar cells and systems under illumination are not available because no technical solution to the problem of reaching the working concentration inside a climatic chamber has been available. This work presents an automatic instrumentation system that overcomes the aforementioned limitation. Working conditions have been simulated by forward biasing the solar cells to the current they would handle at the working concentration (in this case, 700 and 1050 times the irradiance at one standard sun). The instrumentation system has been deployed for more than 10 000 h in a thermal aging test for III-V concentrator solar cells, in which the generated power evolution at different temperatures has been monitored. As a result of this test, the acceleration factor has been calculated, thus allowing for the degradation evolution at any temperature in addition to normal working conditions to be obtained. [ABSTRACT FROM AUTHOR]

A transmission line transformer (TLT)-based multiple-switch circuit topology was recently proposed for pulsed-power generation. By means of a TLT, multiple spark-gap switches can be synchronized in a short time (ns). It is attractive to be used to design a long-lifetime repetitive large pulsed-power source (100 kW, 1 kHz) for various kinds of applications, such as corona plasma-induced gas cleaning. To gain insight into the synchronization principle and switching behavior of the individual switch, an equivalent circuit model was developed and an experimental setup with two spark-gap switches and a two-stage TLT has been constructed. We observed that in terms of switching currents, the two switches can be synchronized within 2–3 ns. The equivalent circuit model approximately fits the experimental results. [ABSTRACT FROM AUTHOR]

In this study, an improvement in energy conversion efficiency has been reported, which is realized by using a double-clamped piezoelectric beam, based on uniaxial stretching strain. The buckling mechanism is applied to maximize axial stress in the double-clamped beam. The voltage generated by using the double-clamped piezoelectric beam is higher than that generated by using other conventional structures, such as bending cantilevers coated/sandwiched with piezoelectric film, which is proven both theoretically and experimentally. The power generation efficiency is enhanced by further optimizing the double-clamped structure. The optimized high-efficiency energy harvester utilizing double-clamped piezoelectric beams generates a peak output power of 80 μW, under an acceleration of 0.1g. [ABSTRACT FROM AUTHOR]

In this study, a dielectric elastomer (DE) generator is developed for micropower generation, and its efficiency is derived. It is shown explicitly that power generation efficiency depends on the thickness of the DE generator, the charging voltage, the effective stiffness of the DE generator, the dielectric constant, and the relative deformation. Through experiments with VHB™ 4905 film, the proposed analysis is verified. In particular, the effective stiffness of a DE generator inversely improves the power generation efficiency. [ABSTRACT FROM AUTHOR]

Experimental works on thermal management of electronic systems, such as thermal resistance or thermal conductivity measurement, often require a controlled heat power source. This article proposes a circuit based on an integral automatic controller that sets a heat power dissipation level of a power metal-oxide-semiconductor field effect transistor used as a heating device. It can operate in dc mode, setting a steady power generation, and in pulsed mode, controlling a transient power wave form. The controller operation principle is established together with all details for its implementation and use. [ABSTRACT FROM AUTHOR]