A 17-in. video rate full color Ferroelectric Liquid Crystal Display (FLCD) with 720•~916 dots, using r-Vmin mode was developed. The full color moving images with 256 gray levels for each color was displayed by the digital gray scale method combining 2 bits spatial dither and 4 bits temporal dither. The response speed of FLC material is very fast (12 ps/line) and the 4 bits temporal dither with video rate scanning was realized. The FLCD shows a contrast ratio of 60 : 1, a wide viewing angle due to the in-plane switching, and strong shock stability (20 kg/cm2) due to the spacer walls structure. This paper presents a high potential of FLCD for the large-size direct-view video-rate full-color simple-passive-matrix flat panel display.
A lot of brushless DC motors are adopted in the compressor of the air conditioner and the refrigerator because of the maintenance-free and highly effective. And, sensorless drive using back electromotive force (EMF) is widely used for these motor controls.However, it is very difficult to apply the sensorless drive at the start sequence because the EMF is too low to detect. Therefore, an open loop drive that controlled by fixed switching pattern is used at the start sequence. After acceleration up to the appropriate speed, the drive method switches to the sensorless drive from the open loop drive.This start sequence has some problems. The motor output torque and the rotational speed change greatly when the motor is driven by an open loop control, and it causes the vibration. Furthermore, it is important to adjust the switching patterns of the open loop appropriately. If it is not adjusted appropriately, the switch to the sensorless drive may fail.In this paper, we propose new start method suitable for sensorless brushless DC motor drive systems. The proposed method introduces new switching patterns at the start point. The switching patterns are determined by motor parameters. Using this method, the open loop drive sequence can be eliminated. Fig. 1 shows the simulation result of the motor output torque and the rotational speed of conventional open loop start method.The motor output torque and rotational speed change greatly and the vibration occurs after the start. Fig. 2 shows the simulation result of the motor torque output and the rotational speed of new start method.The motor output torque and the rotational speed are smooth from the start. Fig. 3 shows the experimental result that shows applied voltage and the motor current waveform at the start. The smooth acceleration is obtained using the proposed method. As mentioned above, we has proposed new start method for brushless DC motors. Rapid acceleration and high performance can be achieved. The simulation and experimental results demonstrated the validity of the proposed method.
It is a well known fact that the height of the mean sea level changes with the season of the year, and that the range of annual variation reaches even as large as 40 cm. at some parts along the Japanese coast. It reaches to the maximum height generally in late summer or in early autumn, and to the minimum in middle or late spring. These partial tides are called as " Solar annual tide " and " Solar semi-annual tide ", and are usually abbreviated as Sa and Ssa respectively. The causes of this annual variation have been considered to be attributed to the meteorological and oceanographical origins, and many authorities have tried to explain this phenomenon qualitatively and quantitatively, but this problem has not yet been definitely solved.Engaging in the routine work of tidal prediction in the past few years, however, the author has found that the amplitude of annual variations varies year by year, and he was interested in finding the sources of deviation of these annual variations compared to the mean amplitude for a long period at respective places.In this short report, however, I shall not go into the details of these discussions, but only show the results of the harmonic analysis based upon the observations as long a period as I could obtain. § 2 The method of obtaiping the data.The -data were all taken from the reports " Tidal Observations " published by the Marine Observatory, Kobe, Japan.In some tidal stations, the standard datum from which the height of the sea surface was reckoned, had been changed in the way of the observation period. In such cases, the whole data throughout the period can never be considered to refer to some definite levels.Thus, to reduce them to one definite level, the following corrections were aiplied to the respective period. The detail of the reason of these corrections will be seen in " Memoirs of the Fukuoka Meteordtogical Observatory," which will he published in the near future.Plotting the data obtained in this way on the graph paper in the chronological order, the author found that the yearly mean sea level undergoes some secular changes (see Fig.
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