Applied Mechanics and Materials Vols. 130-134

Abstract: Light intensity enhancement of GaN-based blue light-emitting diodes (LEDs) is performed using different surface roughening technologies. Three roughening technologies are applied that contain surface roughening of p-GaN, textured indium tin oxide (ITO) on roughened p-GaN, and growing ZnO nanorods on textured ITO/p-GaN. A roughened p-GaN surface was grown on the c-plane sapphire substrate at temperature 800 °C. The morphologies of the textured LEDs with roughness in the range from 9.67 nm to 51.13 nm were observed. The light output efficiency of LED with roughened ITO layer is increased up to 73.8 %. Different dimensions of LEDs can be driven by constant injection current 20 mA without increasing threshold voltage, and larger size of ZnO/ITO/p-GaN LED shows higher luminance intensity. The LEDs with ZnO nanorods on roughened ITO/GaN have shown great performance to enhance the power conversion efficiency.

Abstract: In this paper, a single-crystal silicon capacitive accelerometer is put forward. The accelerometer is composed of a single-crystal silicon vibration head and two backplates, forming a sandwich structure. With damping holes fabricated on backplates, the squeeze-film damping effect is reduced and a Q factor around 0.7 is obtained. This accelerometer has a simple fabricating process including wet and dry etching and ambient pressure packaging. Its tested sensitivity is 22.6pF/g and calculated noise level is lower than 100ng/√Hz, thus meets the demand of seismic applications.

Abstract: Job shop scheduling in the production management module is one of the core of ERP system. To solve the problem, that is, to discretely manufacture the multi-process routes and the multi-objective job shop scheduling, this paper propose an optimized algorithm of the improved particle swarm that is used to establish the mathematical model which turns in the direction of the production scheduling system of ERP-based. And with the example of an engineering machinery manufacturing enterprise, it deduces a model’s realization process in the multi-objective shop scheduling in the discrete manufacturing of more complex product structures. It finally gives integration framework of production scheduling system based on the real-time capacity balance, which are based on the particle swarm optimization (PSO) algorithm, and together with the other modules of ERP system. It provides an important practical value for discrete manufacturing enterprises using ERP system to realize scientific and effective production operation management.

Abstract: Structure static testing is an important means to study the static characteristic of complex engineering structure. Electrohydraulic stactic loading system is the singnificant equipment of the testing. With its function of transfering low-power electrical singal to large-power hydraulic output quickly and precisely, the servo valve plays a key role in an electrohydraulic servo control system and dominates to a large extent the performance of the whole control system. Conventional electrohydraulic servo or proportional control is subject to the nonlinearites of their electro-mechanical interface, such as hysteresis, saturation and finite resolution. In this paper, a direct actuated digital servo valve was applied in electrohydraulic static loading system. It can be driven directly by computer needn’t D/A and has the advantages of simple structure, high tolerance to contamination and high reliability. Practical load-experiment results show that the static loading system with a direct actuated digital servo valve can work steadily and reliably and possess high accuracy and fast response.

Abstract: The present work investigates reflectivity and optimal reflective distance of optical fiber hydrogen sensor in over 0～4000um range. The approximate equality of reflective distance in two optical paths increases signal to noise ratio for optical hydrogen sensor, the fabrication of optical path could eliminate the internal noise and external interferences, and provides higher stability for hydrogen sensor. Through a series of simulation experiments it was found that different reflective distances determine the sensitivity and amplitude response of hydrogen sensor. When the reflective distance was about 1mm in optical path, the sensitivity of optical hydrogen sensor could reach the peak value.

Abstract: A novel optical sheet with double-layer microstructures is proposed to improve the brightness uniformity and optical efficiency in the LED direct-lit backlight module. By means of 2D ray-tracing program design and commercial optical software simulation, we enhance the brightness uniformity from 45.3% with traditional planar diffuser to 82.7% with new optical sheet, and the average brightness is promoted about 10.9% in the same frame of backlight module which internal thickness is only 13mm. Thus, this novel optical sheet with microstructures design is useful for a slim LED direct-lit backlight module.

Abstract: Removed due to double publication.

Abstract: Characterization of measurement uncertainty as a measure of quality of results, and obtained in the metrology of a wide range of applications. At all levels of certified calibration laboratory measurement, measurement standards of the establishment of technical reports, or identification certificate issued by the calibration and so on, require a higher level in the measuring results are given to provide the corresponding uncertainty. Measuring the quality of the results of the measurement results is a measure of the credibility of an important basis. In this paper, through concrete examples and laboratory measurement of electrical parameters of the light source of the data obtained, the Evaluation of Uncertainty.

Abstract: For the characteristics of high frequency of switching devices in the photovoltaic inverter and complexity of circuit topology, the insulated gate bipolar transistor driving protection circuit is designed which is suitable for photovoltaic inverter. The circuit which is based on thick film structure of M57962L has isolated power supply and threshold voltage regulator circuits. The control and regulation can be achieved precisely for the threshold voltage of over current protection. The internal structure of M57962L has been analyzed here. The process of slow turn off action is observed practically. For the circuit periphery parameters of M57962L, the general calculation methods are given according to various models and the level of protection for IGBT. The practical application shows that the method is correct and effective.

Abstract: The optical absorptions are calculated in an InAs/GaSb-based type II and broken-gap quantum well under applied electric field. Two absorption peaks were observed through intraband transitions within the same material layer. The absorption induced by the interlayer transition is rather weak due to the small overlap of electron and hole wavefunctions. The optical absorption can be significantly affected by the applied electric field. Our results suggest that InAs/GaSb-based type II and broken-gap QWs can be employed as two-colour photodetectors, which can be controlled by the applied electric field.