Development of coal mine methane concentration technology for reduction of greenhouse gas emissions

In coal mines in such countries as China and Russia,most of the coal mine methane(CMM) generated during mining is emitted to the atmosphere without any effective usage,because the methane concentration of CMM is relatively low and not allowed to be used as fuel for safety reasons.Methane is one of the greenhouse gases.Therefore,if it becomes possible to concentrate CMM to an acceptable level for use as fuel,this will greatly contribute to reduction of greenhouse gas emissions.With the aim of gaining approva...     

Identification of crack path of inter- and transgranular fractures in sintered silicon nitride by in situ TEM

Inter- and/or transgranular crack paths in sintered silicon nitride (Si3N4) during fracture were investigated by in situ straining experiments in a transmission electron microscope at room temperature, using a high-precision micro-indenter. By this technique, cracks introduced in an in situ manner were observed to propagate in the grain interior and along grain boundaries. High-resolution electron microscopy (HREM) observation revealed that the crack propagation takes place at an interface between Si3N4 grains and an intergranular glassy film (IGF) in the case of intergranular fractures. According to the results by previous molecular dynamics simulations, a number of dangling bonds are present at the Si3N4/IGF interface, which should result in the observed fracture behavior at the interface. On the other hand, the crack path introduced during transgranular fracture of Si3N4 grains was found to be sharp and straight. The observed crack propagated towards [1120] inside the Si3N4 grain with the crack surface parallel to the (1100) plane. The HREM observations of crack walls revealed them to be atomically flat. The atomic termination of the crack walls was identified in combination with image simulations based on atomic models of the cleaved crack walls.     

Anthracene derivatives as efficient emitting hosts for blue organic light-emitting diodes utilizing triplet–triplet annihilation

The molecular design strategies for the host materials suitable for highly efficient, blue fluorescent organic light-emitting diodes (OLEDs) are demonstrated. The device characteristics of blue fluorescent OLEDs are compared with different host materials. Some devices exhibit a highly efficient blue electroluminescence with a high external quantum efficiency of more than 7%. The correlation between OLED efficiency and triplet–triplet annihilation is characterized by measuring the up-conversion of triplet excited states into singlet ones. The host materials require an anthracene unit and a bulky molecular structure to prevent the overlap of anthracene units between adjacent molecules in the film.     

Circuit level prediction of device performance degradation due to negative bias temperature stress

A circuit level methodology for predicting performance degradations due to negative bias temperature stress is developed in this paper. Degradation mechanism is discussed based on experimental observations. Then, models that consist of a threshold voltage shift and a drain current reduction are developed based on the degradation mechanism. The developed models are implemented into a compact MOSFET model so that we can directly link the local degradation of pMOSFETs’ electrical characteristics to the total circuit performances. The validity of the developed models is confirmed by the good agreement in simulated and measured results of I–V characteristics of pMOSFET in all the transistor working region before and after negative bias temperature stress. Then, circuit performance prediction is carried out for the stressed 199-stage ring oscillator on its waveform and oscillation frequency. Excellent agreements between the experimental results and predicted results are obtained.     

Relation Between Discharge Length and Laser Pulse Characteristics in Longitudinally Excited CO2 Laser

A longitudinally excited CO₂ laser pumped by a fast discharge emits a short laser pulse, similarly to TEA and Q-switched CO₂ lasers. We investigated the relation between the discharge length and the laser pulse characteristics to develop a longitudinally excited CO₂ laser producing a high spike laser pulse. We examined discharge lengths of 30, 45, and 60 cm, using the same mirrors and the same excitation circuit with the same input energy. A longer discharge length increased the discharge volume and improved the laser output energy. However, the longer discharge length caused a long discharge formation time (a slow fall time of the discharge voltage) due to the higher discharge impedance, which resulted in a long laser pulse tail. Therefore, the longitudinally excited CO₂ laser had optimum conditions for obtaining a high spike laser pulse effectively.     

电容式触摸按键扫描灵敏度及防水性研究

作为新一代按键输入方式的触摸式按键已经在众多领域得到广泛应用,由于触摸输入方式采用非接触式的按键技术,因此其寿命远远超过机械按键,其可靠性也不会随着时间的延长而降低.但目前使用最普遍的电容式触摸按键也正处于发展和完善阶段,而电容式触摸按键扫描的灵敏性及防水性能一直是该技术所面临的最大难题.本文通过分析与按键扫描灵敏度相关的硬件参数,同时运用所设计的算法来区分和调控按键在无水及带水操作下的扫描处理方式,以实现电容式触摸按键扫描的灵敏性及防水功能.研究结果表明,所设计的电容式触摸按键反应灵敏、检测精准、具有一定的防水效果,较好地解决了该技术所面临的难题,并具有良好的市场前景.     

Fast Discharge Circuit for Longitudinally Excited CO2 Laser

In a longitudinally excited CO₂ laser with a short laser pulse, similarly to TEA and Q-switched CO₂ lasers, a fast discharge is very important. We investigated the use of a fast discharge circuit to obtain a high spike laser pulse in a longitudinally excited CO₂ laser. We compared a traditional capacitor-transfer circuit having a buffer capacitance of 700 pF with our direct-drive circuit in which the buffer capacitance is removed. The direct-drive circuit produced a fast discharge and a high spike laser pulse. We also investigated the effect of a resistance connected in parallel with the discharge tube to eliminate low discharge current after the main discharge. A low resistance of 1 kΩ or less acted as a shunt resistance. The shunt resistance was effective in decreasing the energy of the laser pulse tail at high gas pressure.     

Differentiation and function of osteoclasts cultured on bone and cartilage

We examined the differentiation and resorptive function of osteoclasts (OC) cultured on the slices of calcified bone, decalcified bone and hyaline cartilage, and found that OC differentiation depends on the co-cultured substratum, as well as osteoblast-derived factors. Bone marrow-derived macrophages (BMM) were formed from marrow cells of 5 week old ddY mice and cultured for 3 days on freeze-dried slices of calcified bone, decalcified bone or cartilage, all prepared from rabbit costal bone. BMM cultured on calcified bone slices exhibited tartrate-resistant acid phosphatase (TRAP) activity and were structurally characterized by multinucleation and ruffled border development. However, on decalcified bone slices, BMM seldom became multinucleated and exhibited weak TRAP activity. BMM cultured on cartilage slices were mononuclear, devoid of TRAP activity and structurally resembled mononuclear phagocytes. In SEM observations of co-cultured slices, resorption lacunae were formed only on calcified bone slices, and not on slices of decalcified bone and cartilage. Our results, therefore, indicated that BMM could differentiate into functional OC only on calcified bone slices, suggesting a key role of calcified components in the bone matrix for the terminal OC differentiation. Then, we cultured BMM on the same slices with yeast particles. In cultures with yeast particles, BMM exhibited intense TRAP activity, developed a ruffled border-like structure and formed resorption lacunae even on decalcified bone and cartilage slices. Vacuolar-type H+-ATPase was strongly expressed along the ruffled border membranes of these OC. Only the BMM that had not incorporated yeast particles developed a ruffled border, whereas the BMM that had incorporated yeast particles did not become multinucleated and lacked a ruffled border structure. Thus, our results further suggest that, even on uncalcified substrata, the terminal differentiation of BMM into functional OC is induced by an unidentified external stimulus, which may be contained in the cell membrane of yeast particles.     

A high-power electrostatic motor using skewed electrodes

This paper describes a new type of high-power electrostatic motor equipped with skewed electrodes. The authors have developed several types of high-power electrostatic motors. Among them, the dual excitation multiphase electrostatic drive (DEMED) has the best performance in terms of power. Its power/weight ratio is almost the same as that of the most advanced conventional electromagnetic motors. However, DEMED exhibits a large force ripple leading to such disadvantages as low controllability, high noise, and vibration. To overcome these disadvantages, the authors have proposed to apply the skew technique to DEMED and have analyzed the effects of skewing the electrodes. The analysis has shown that appropriate skewing can reduce the force ripple considerably. In this paper, we further analyze the shape of the electrodes. A new type of motor incorporating the results of the analysis is fabricated and tested. Using the new DEMED with skewed electrodes (V-DEMED), the slider motion becomes much smoother, noise and vibration are reduced, and efficiency improves, without compromising the thrust force. © 1998 Scripta Technica, Electr Eng Jpn, 125(3): 50–58, 1998     

基于AU7850的触摸式多媒体播放器设计

随着电子科学技术的发展,多媒体播放设备在生活中无处不在。本文阐述了一种触摸式多媒体播放器的整体系统设计方案。此播放器选用AU7850芯片,能解码MP3及WMA格式文件,同时支持U盘、SD卡和TF卡的读卡功能,从而可以从外接存储设备中进行音频文件的播放。播放器外部面板配备LCD显示屏实现多种功能的显示,并采用触摸式按键来执行多种播放功能。系统采用5V锂电池供电,可通过迷你USB接口对电池进行充电,并带有锂电池保护电路,防止过度充放电造成电池的损坏。此播放器对多种外接存储设备的支持使得其实用性大幅提高,LCD显示屏和触摸式按键也使得系统设计更加便捷化与人性化。