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1

An approximation algorithm for multi-unit auctions: numerical and subject experiments

Takahashi S., Izunaga Y., Watanabe N.

Operations Research and Decisions

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2018

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Vol. 28, No. 1

95--115

EN

In multi-unit auctions for a single item, the Vickrey–Clarke–Groves mechanism (VCG) attains allocative efficiency but suffers from its computational complexity. Takahashi and Shigeno thus proposed a greedy based approximation algorithm (GBA). In a subject experiment there was truly a difference in efficiency rate but no significant difference in seller’s revenue between GBA and VCG. It is not clear in theory whether each bidder will submit his or her true unit valuations in GBA. We show, however, that in a subject experiment there was no significant difference in the number of bids that obey “almost” truth-telling between GBA and VCG. As for individual bidding behavior, GBA and VCG show a sharp contrast when a human bidder competes against machine bidders; underbidding was observed in GBA, while overbidding was observed in VCG. Some results in a numerical experiment are also provided prior to reporting those observations.

2

Experimental and numerical investigation on the fundamental natural frequency of a sandwich panel including the effect of ambient air layers

Chanthanumataporn S., Watanabe N.

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 3

658--668

EN

Due to the advanced lightweight characteristic of sandwich structures, ambient air can significantly affect their natural frequency. In order to clarify the importance and magnitude of this effect, the natural frequency of a sandwich panel surrounded by air layers using experiment and numerical simulation was investigated in this study. The experiment setup based on modal testing was proposed with the feature of simulating air layers around the sandwich panel. The numerical simulation was formulated on the basis of fluid–structure interaction analysis. The experimental and numerical simulation results correspondingly demonstrated that the fundamental natural frequency of sandwich panel tends to decrease to be less than 25% of the frequency neglecting the air effect when the air layer thickness becomes thinner than 3 mm.

3

Mechanical circulatory support systems at Tokyo Medical and Dental University

Ohuchi K., Hoshi H., Watanabe N., Kido K., Yokoyama Y., Asama J., Shinshi T., Shimokohbe A., Yoshikawa M., Takatani M.

Biocybernetics and Biomedical Engineering

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2007

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Vol. 27, no. 1-2

161-167

EN

This paper describes mechanical circulatory support devices (MCSD) which are under development at Tokyo Medical and Dental University in collaboration with Tokyo Institute of Technology. They include para-corporeal magnetic levitated (Mag-lev) centrifugal blood pump, implantable Mag-lev centrifugal blood pump, extra-corporeal pediatric centrifugal blood pump, and implantable pulsatile ventricular assist device (VAD) and totally replacement artificial heart system.

4

Development of implantable assist pump and its peripheral devices

Okamoto E., Makino T., Yamamoto Y., Asao H., Watanabe N., Nakamura M., Tanaka S., Inoue Y., Yasuda T., Mitamura Y.

Biocybernetics and Biomedical Engineering

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2006

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Vol. 26, no. 1

45-51

EN

Two national project for development of an artificial heart system are being undertaken in Japan, and Hokkaido Tokai University has taken part in both national projects in order to develop peripheral devices of an implantable VAD (ventricular assist device) system. Each of the peripheral devices incIudes a transcutaneous energy transmission system, an internal battery system, and a transcutaneous information transmission system. Maximum energy transmission efficiency of the transcutaneous energy transmission system is over 85% (DC to DC) at an energy transmission ratio of 25 W. The internal battery system mainly consists of three lithium ion batteries, a charge circuit, and a power interface (case size of 11Ox80x30 mm). The internal battery system can drive a VAD for over 2 hours with maximum battery case surface temperature of 43°C. The information transmission system (diameter of 52 mm and thickness of 12 mm) mainly consists of an ASK modulator and an ASK demodulator employing carrier frequencies of 4 MHz and 10 MHz. It can transmit data electromagnetically between inside and outside of the body bi-directionally at a data transmission ratio of 56 kbps. Long-term animal experiments showed that each peripheral device has adequate performance to support the operation of implantable VAD.

5

Measurement of ball motion in a ball-type limited slip differential gear

Takenouchi K., Fuji T., Takeyari T., Watanabe N., Iwama A., Kawakita K.

Applied Mechanics and Engineering

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1999

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Vol. 4, no spec.

321-328

EN

Measurement of ball motion in a new-type limited slip differential gear for automobiles is carried out, differential gear which is under development by Hitachi Metals, Ltd. based on a new principle with steel balls and races having an ad-hoc configured race pattern. One ball in the differential gear is magnetized and the direction of magnetic axis rotating with the ball is traced by Hall sensors assembled in orthogonal three axes around the ball. Output signals from the sensors are plotted in orthogonal projections to the three axes, offering a clear understanding of the ball motion. Expressions for calculating the angular velocity components of ball motion are deduced and the ball motion is numerically analyzed from the data obtained in the measurement. The results demonstrate complicated ball behaviors, which include important information on slip between the ball and the groove surfaces affecting the durability and life of the system.