Low loss static induction devices (transistors and thyristors)

To decrease the power loss, a current gain of a bipolar mode Static Induction Transistor (BSIT) is examined with quasi-one-dimensional analysis. The current gain dependence on source contact area is presented with experimental, analyzed and simulated results. Concerning Static Induction Thyristor (SIThy), the switching speed improvement methods are presented to reduce the switching loss of device. A proton irradiation, or a shorting method is a useful technique to decrease the switching time and switching loss of SIThy.     

Effects of nitrogen annealing on electron scatterings in SiSiO2 interface

The effective mobility of electrons at Si (100) surfaces was measured as a function of electron density N_s = 5 × 10¹¹?1 × 10¹³ cm^?2 at 4.2K for samples with and without annealing (10 min–2 hr) in nitrogen gas at 1000°C after wet thermal oxidation. A great part of the scattering by Coulomb and short-range potentials was reduced by a short (～10 min) anneal time, although the subsequent annealing resulted in a slight increase in the number of the scatterers. On the other hand, scattering by a surface roughness potential was reduced with increase in the anneal time. These scattering effects associated with N₂ annealing are discussed.     

Two-phase flow measurements using a photochromic dye activation technique

A novel flow visualization method called photochromic dye activation (PDA) technique has been used to investigate flow structures and mechanisms in various two-phase flow regimes. This non-intrusive flow visualization technique utilizes light activation of a photochromic dye material dissolved in a clear liquid and is a molecular tagging technique, requiring no seed particles. It has been used to yield both quantitative and qualitative flow data in the liquid phase in annular flow, slug flow and stratified-wavy flows.     

Synchrotron X-Ray Study of the Crystal Structure and Hydrothermal Degradation of Yttria-Stabilized Tetragonal Zirconia Polycrystal

Structural study with synchrotron X-ray diffractometry was made on phase separation phenomena in 2, 3, and 4 mol% Y₂O₃-stabilized tetragonal ZrO₂ polycrystal (abbreviated as 2, 3, and 4Y-TZP, respectively). The sintered body of 3Y and 4Y-TZP underwent phase separation into high and low yttrium regions as sintering temperature increased, and the tetragonal phase was assigned to both regions. The sintering body is less separated, and a large monoclinic phase was detected in 2Y-TZP. Analysis of aging kinetics of tetragonal- to monoclinic-phase transition showed that the fraction of the transformable phase agreed with that of the low yttrium region.     

Application of electron holography to the determination of contact potential difference in an AlGaN/AlN/Si heterostructure

Electron holography was applied to determine the contact potential differences in an AlGaN/AlN/Si heterostructure formed by metallorganic vapor phase epitaxy. Since mean inner potentials are generally different for different materials, their values before and after forming the junction were evaluated first, then the contact potential difference was obtained by subtracting the difference of the mean inner potentials before forming the junction from the corresponding difference after forming the junction. The contact potential differences thus obtained were consistent with a reported asymmetric nonlinear behavior in the current-voltage characteristics measured for a similar heterojunction diode.     

冲击电压下残余电荷对沿面放电发展的影响

固体绝缘的表面是高压电力设备绝缘的最薄弱环节,很多绝缘事故都是由沿面放电造成的。发生放电后,电荷会在绝缘表面积聚,会很大程度上影响下一次放电的产生与发展。为此,通过观测在极性交替变化的冲击电压作用下沿同轴圆柱形聚对苯二甲酸乙二醇酯(PET)绝缘表面放电的发展以及测量放电后表面残余电荷电位的分布,来研究残余电荷对沿面放电的影响。研究表明,在改变冲击电压的极性后,由于反极性残余电荷的影响,放电会被促进,放电通道会沿着前一次放电的通道向前发展,并且会比前一次放电距离略长,放电的强度会增强,放电的发展速度也会加快。在沿着放电通道方向,表面电荷电位梯度可以明显分为两部分:在放电头部的20mm区域,电位梯度较大,为流注放电;而在后面的主干部,电位梯度平缓,为先导放电。     

Adsorption and aggregation of Fe(III)-hydroxy complexes during the photodegradation of phenol using the iron-added-TiO(2) combined system

The behavior of Fe(III) aquacomplexes in TiO(2) suspensions in the degradation of phenol has been investigated. The most active Fe(OH)(2+) species adsorbed on the surface of TiO(2) retards the conversion of Fe(OH)(2+) into oligomers and therefore increases the percentage of Fe(OH)(2+) with irradiation time, with a consequent enhancement in the catalytic cycle of Fe(III)/Fe(II) and excited charge traps by Fe(III) in the iron-TiO(2) system. The influence of iron addition on TiO(2) was obtained when the regeneration of [Fe(OH)(2+)] remained continuous with irradiation time. In an optimum TiO(2) suspension (0.5g/L) with the addition of 0.1mM Fe(III), the measured k(obs) values for phenol degradation were enhanced for the higher adsorption of Fe(OH)(2+) on the reactive surface of TiO(2) at a specified irradiation time.     

Model-based fault detection and isolation in steer-by-wire vehicle using sliding mode observer

Steer-by-Wire system (SbW), in which the conventional mechanical linkages between the steering wheel and the front wheel are removed, is suited to active steering control, improving vehicle stability, dynamics and maneuverability. And SbW is implemented to autonomous steering control to assist the driver. However, the SbW vehicle contains unsolved important problems about fault tolerant function. For example, it is the detection of sensor fault and multiplicative fault simultaneously. Fault detection and isolation (FDI) is essential in fault-tolerant problems, and conventional FDI for SbW was based on Kalman filter. But this method has weak robustness and cannot detect sensor fault and multiplicative fault simultaneously. We propose a novel model-based fault detection and isolation method using sliding mode observer in the SbW vehicle, which contains measurement of sensor fault and multiplicative fault. The effectiveness of the proposed method is verified by simulations. This paper was recommended for publication in revised form by Associate Editor Kyoungsu Yi Jae-Sung Im was born in Busan, Korea in 1978. He received his B.S. and M.S. degrees in Mechanical Engineering from Pukyong National University, Korea, in 2003 and 2005, respectively. He then received his Ph.D. degree from Kumamoto University, Japan, in 2009. His interests are in vehicle dynamics, robust control, fault detection and isolation, and man-machine interface. Fuminori Ozaki received the B.S. and M.S. degrees from the Department of Computer Science, Kumamoto University, Japan, in 1998 and 2000. In 2000, he joined OMRON Corporation, Kyoto, Japan, where he developed semiconductor manufacturing equipment. His current interests include EPS control and KANSEI engineering. Tae-Kyeong Yue received the B.S. and M.S. degrees from Pukyong National University, Korea, in 1998 and 2000, respectively. He received the Ph.D. degree from Kumamoto University, Kumamoto, Japan in 2003. He is working in the Korea Ocean Research and Development Institute (KORDI), Korea. His interests are fault detection and isolation, decentralized control and control of deep-sea mining system. Shigeyasu Kawaji received his Master of Engineering in Electrical Engineering and Doctor of Engineering in Control Engineering from Kumamoto University and Tokyo Institute of Technology, Japan, in 1969 and 1980, respectively. He joined the Department of Electronic Engineering of Kumamoto University, Japan, where he is presently as a full professor. He is the Director of System Integration Laboratory. He is presently the President of Advanced Health Laboratory Ltd. His current research interest includes robust control, intelligent control mechatronics and robotics, fusion of medicine and engineering, and automotive mechatronic systems.     

Effect of Viscosity on Vibration-Induced Motion of a Spherical Particle Suspended in a Fluid Cell

Production of protein and semi-conductor crystals with advanced quality and properties is possible under microgravity conditions due to the suppression of convection effects. However, aboard space platforms, g-jitter induced motions of solid particles can cause unsteady convection that may result in degradation of the properties of crystals produced. There are different effects of g-jitter on small particles suspended in a fluid cell which are not fully understood. To investigate these small vibration effects, ground experiments were conducted by suspending a spherical particle with a thin wire in a rectangular fluid cell and subjecting the cell and particle to horizontal vibrations with different frequencies and amplitudes. The fluid viscosity was varied to investigate the attraction or repulsion force induced in the direction normal to the direction of the vibration. The force was found to change from attraction to repulsion with an increase in the fluid viscosity and increase with the increasing vibration frequency and amplitude.