• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.720-725
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• 2002

The fringe-field switching (FFS) mode was known to exhibit both a wide viewing angle and high transmittance, especially when using the liquid crystal (LC) with negative dielectric anisotropy. In the device, the LC director rotates almost in-plane. However, in the bright state the device shows bluish and yellowish color along parallel and perpendicular to the LC director at off-normal directions since the LC director rotates only in one direction. Such a problem was greatly improved using a wedge shape of only pixel electrodes. In this way two different field directions exist in a pixel, enabling the LC director to rotate in two opposite directions. Consequently, owing to dual domain effect when using the LC with negative dielectric anisotropy, the viewing angle characteristics are greatly improved.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2526-2528
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• 1999

Parameters of equivalent circuit of IPMSM are varied according to current magnitude and current phase angle. Especially, Parameter variation of IPMSM for an electric vehicle(EV) is critical. Because current magnitude is very large. and current phase angle range also is wide. So, variation characteristics of $L_d$ and $L_q$ of the IPMSM are analyzed and verified through experiments. And then new parameter estimator of $L_d$ and $L_q$ that is constructed by neural network technique is suggested Using numerical method, the advanced characteristics of current controller of vector control algorithm is verified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1437-1448
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• 1997

Pressures of a five-hole probe were measured for a full range of yaw and pitch angles and complete pressure coefficient maps were obtained. Based on these maps, various features of five-hole probe pressures were revealed and new five-hole probe calibration coefficients were devised. The new calibration coefficients show non-diverging characteristics for any flow direction and one-to-one correspondence for a wide range of flow angles. These calibration coefficients expand the valid flow angle range of five-hole probe calibration by .+-.10 degrees and complement a critical defect of five-hole probe zone-division calibration method which has not been known yet. Moreover new non-diverging calibration coefficients have advantages in nulling methods, too.

• Wind and Structures
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• v.12 no.6
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• pp.519-540
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• 2009

This paper presents the results of a study into experimental and numerical methods for the identification of bridge deck flutter derivatives. Nine bridge deck sections were investigated in a water tunnel in order to create an empirical reference set for numerical investigations. The same sections, plus a wide range of further sections, were studied numerically using a commercially available CFD code. The experimental and numerical results were compared with respect to accuracy, sensitivity, and practical suitability. Furthermore, the relevance of the effective angle of attack, the possible assessment of non-critical vibrations, and the formulation of lateral vibrations were studied. Selected results are presented in this paper. The full set of raw data is available online to provide researchers and engineers with a comprehensive benchmarking tool.

• Current Optics and Photonics
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• v.1 no.3
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• pp.214-220
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• 2017

A wavelength filter based on a polymer Bragg reflector has received much attention due to its simple structure and wide tuning range. Tilted Bragg gratings and asymmetric Y-branches are integrated to extract the reflected optical signals in different directions. To optimize device performance, design procedures are thoroughly considered and various design parameters are applied to fabricated devices. An asymmetric Y-branch with an angle of $0.3^{\circ}$ produced crosstalk less than -25 dB, and the even-odd mode coupling was optimized for a grating tilt angle of $2.5^{\circ}$, which closely followed the design results. Through this experiment, it was confirmed that this device has a large manufacturing tolerance, which is important for mass production of this optical device.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.30-32
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• 1995

The SRM has high efficiency, a wide speed range, high speed capability and DC-series Motor characteristics. So the SRM has been studied as adjustable speed machine. The speed of SRM can be adjusted to switching angle and exciting voltage. This paper suggests an constant speed drive method of SRM. In this method, the speed is controlled by voltage regulation using PI control and the torque is controlled by advance angle in accordance with, load torque variation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.270-274
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• 2008

The microwave sensor in which the sensitivity was excellent and a structure is simple was developed and it manufactured. And the sensing range that uses the developed product was confirmed. When the developed microwave sensor was set up in the ceiling of a building, we confirmed that the amplitude of the sensitive area increased as the tilting angle was enlarged. The sensitive area became a greatest in case the tilting angle was 65 degree. According to the height of a ceiling, because the sensing range is determined, in case of using in the building in which the height of a ceiling is enough secured it is determined to secure the more wide sensitive area. Moreover, the configuration of the circuit having the simple structure makes the miniaturization of a product, and the light weight possible. It is considered to have the price competitive power which it reduces the manufacturing cost, is sufficient.

• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.4
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• pp.131-136
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• 1999

Aerial videography techniques have been used to inventory conditions associated with grassland, forests, and agricultural crop production. Most recently, aerial videography has been used to verity satellite image classifications as part of the natural ecosystem survey. The objectives of this study were: (1) to use aerial video images of the study area, one part of Taean Seashore National Park, for the accuracy assessment, and (2) to determine the suitability of aerial videography as an accuracy assessment, of the land cover classification with Landsat-TM data. Video images were collected twice, summer and winter seasons, and divided into two kinds of images, wide angle and narrow angle images. Accuracy assessment methods include the calculation of the error matrix, the overall accuracy and kappa coefficient of agreement. This study indicates that aerial videography is an effective tool for accuracy assessment of the satellite image classifications of which features are relatively large and continuous. And it would be possible to overcome the limits of the present natural ecosystem survey method.

• Journal of Welding and Joining
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• v.3 no.2
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• pp.1-9
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• 1985

In this study, the influence of carbon equivalents on friction welds of similar steels was investigated. Four types of steels with 15mm diameter tested in the wide range of carbon equivalents from 0.3 to 1.1 Main experimental results are summarized as follows : (1) Under the constant burn-off length, the friction time becomes longer with the increasing carbon equivalent, but the upset length shows no consistent tendencies. (2) Due to the recrystallization in the contact area, the maximum hardness occurs some away from the contact surface. And it increases almost linearly with the increasing carbon equivalent. (3) Even a steel with 1.1 C.E. can be friction welded to make defect-free welds. (4) With the increasing carbon equivalent, the bend angle and charpy impact value decrease very rapidly in the range from 0.3 C. E., but remain nearly unchanged for C. E. higher than 0.6. (5) Heat treatment of the base metals before welding has very little influence on the mechanical properties of welds. On the other hand, normalizing of the welds improves the bend angle and charpy impact value, but its effect becomes almost negligible, when the carbon equivalents are higher than 0.6.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.9-11
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• 1994

This paper describes an adjustable switching angle control method of Switched Reluctance Motor to improve the drive efficiency when variable loads applied. The control method to build-up optimal current shape is intended to improve the efficiency of SRM over the wide range of output power without requiring additional power devices, which gives more economic benefits compared with any other control methods.