Full Band Monte Carlo Study for Two-Dimensional Hole Transport in Strained Si p-MOSFETs

Transport properties of the two-dimensional hole gas in inversion layer of strained Si/SiGe p-MOSFETs are investigated using the full-band Monte Carlo simulator based on the nonlocal pseudopotential calculation. The hole mobility is significantly enhanced by the strain in the case of Ge content of ≥20%. Moreover, we also present the high-field transport characteristics of 2D holes. In contrast to the low-field mobility, the hole saturation velocity does not significantly enhanced by the strain.     

Micro Piezoelectric Ultrasonic Motors

This paper reviews recent developments of micro ultrasonic rotary motors using piezoelectric resonant vibrations. Following the historical background, four ultrasonic motors recently developed at Penn State University are introduced; windmill, PZT tube, metal tube, and shear-type motors. Driving principles and motor characteristics are described in comparison with the conventional ultrasonic motors. Motors with 1.5 mm in diameter and 0.8 mNm in torque have been actually developed.     

Optimization method of P+ ω PSS parameters for stability and robustness enhancement in a multimachine power system

Recent steady increase of electric power demand causes power sources to be large and far from cities. Wide area power interchanges lead to larger and more complex power systems. This makes the network susceptible to poor damping power swing oscillations of relatively low frequencies which influence the whole system. This paper describes a newly developed generator's double input signal PSS (P+ ω input PSS) design method. Several power system conditions (power flow and/or power patterns) are considered to satisfy a well‐stabilized power system for each system condition. Major features of this method are: (1) Weighting factor for eigenvalue sensitivity of the oscillation mode is considered when the parameters of the PSS are updated during the optimization process. (2) The new method provides good results for the generator's local and interarea oscillation modes under peak and off‐peak power flow conditions. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 19–31, 2000     

Automatic Train Operation Using Autonomic Prediction of Train Runs

In this paper, we present an automatic train control method adaptable to disturbed train traffic conditions. The proposed method presumes transmission of detected time of a home track clearance to trains approaching the station by employing equipment of Digital ATC (Automatic Train Control). Using the information, each train controls its acceleration by a method that consists of two approaches. First, by setting a designated restricted speed, the train controls its running time to arrive at the next station in accordance with predicted delay. Second, the train predicts the time at which it will reach the current braking profile generated by Digital ATC, along with the time when the braking profile transits ahead. By comparing them, the train correctly chooses the coasting drive mode in advance to avoid deceleration due to the current braking profile. We evaluated the effectiveness of the proposed method regarding driving conditions, energy consumption, and reduction of delays by simulation. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(3): 65–73, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.10020/eej.21080     

Piezoelectric Energy Harvesting under High Pre-Stressed Cyclic Vibrations

Cymbal transducers have been found as a promising structure for piezoelectric energy harvesting under high force (∼ 100 N) at cyclic conditions (∼ 100–200 Hz). The thicker steel cap enhances the endurance of the ceramic to sustain higher ac loads along with stress amplification. This study reports the performance of the cymbal transducer under ac force of 70 N with a pre-stress load of 67 N at 100 Hz frequency. At this frequency and force level, 52 mW power was generated from a cymbal measured across a 400 kΩ resistor. The ceramic diameter was fixed at 29 mm and various thicknesses were experimented to optimize the performance. The results showed that the PZT ceramic of 1 mm thickness provided the highest power output with 0.4 mm endcap. In order to accommodate such high dynamic pressure the transducer and cap materials were modified and it was found that the higher piezoelectric voltage constant ceramic provided the higher output power. Electrical output power as a function of applied ac stress magnitude was also computed using FEM analysis and the results were found to be functionally coherent with experiment. This study clearly demonstrated the feasibility of using piezoelectric transducers for harvesting energy from high magnitude vibration sources such as automobile.