• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.376-383
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• 2005

We designed and fabricated integrated-optic tunable polarization controllers based on $LiNbO_3$ with the Ti-indiffused waveguide along the y-axis utilizing the electro-optic effect. The device consists of $TE↔TM$ mode converters and TE/TM phase shifters. We analyzed the operation principles of each device utilizing transfer matrices based on a Jones matrix and simulated shifting of the center wavelength by inducing voltage. We confirmed experimentally that the fabricated devices control the tunability of the center wavelength and the input SOP.

• Tunnel and Underground Space
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• v.33 no.3
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• pp.150-168
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• 2023

The anisotropic behavior of rocks is primarily attributed to the directional arrangement of rock-forming minerals and the distribution characteristics of microcracks. Notably, sedimentary and metamorphic rocks often exhibit distinct transverse isotropy in terms of their strength and deformation characteristics. Consequently, it is crucial to gain accurate insights into the deformation and failure characteristics of transversely isotropic rocks during rock mechanics design processes. The deformation of such rocks is described by five independent elastic constants, which are determined through laboratory testing. In this study, the characteristics of the directional variation of apparent elastic constants in transversely isotropic rocks were investigated using experimental data reported in the literature. To achieve this, the constitutive equation proposed by Mehrabadi & Cowin was introduced to calculate the apparent elastic constants more efficiently and systematically in a rotated Cartesian coordinate system. Four transversely isotropic rock types from the literature were selected, and the influence of changes in the orientation of the weak plane on the variations of the apparent elastic modulus, apparent shear modulus, and apparent Poisson's ratio was analyzed. Based on the investigation, a new constraint on the elastic constants has been proposed. If the proposed constraint is satisfied, the directional variation of the apparent elastic constants in transversely isotropic rocks aligns with intuitive predictions of their tendencies.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.265-268
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• 2004

교류 전동기의 전류 제어 특성은 전동기의 재정 수의 특성, 전류 제어기의 구성 및 제어 주기, PWM기법 및 주파수에 의해 달라지며, 시스템의 동적 특성 및 효율에도 큰 영향을 미친다. 본 논문은 PMSM(Permanent magnet synchronous motor)의 동기좌표계에서 벡터 제어 시 전류 제어 특성을 분석할 수 있는 실제와 동일한 디지털 전류 제어기 및 SVPWM(Space Vector PW)을 포함한 시뮬레이터를 구현하였으며 고속 및 일반 PMSM을 대상으로 시뮬레이션을 수행하여 그 결과 전류 제어 특성의 예측 가능함을 보였다.

• Journal of Biomedical Engineering Research
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• v.24 no.3
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• pp.183-192
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• 2003

A transformation methode of the chromaticity coordinates was proposed to calibrate the measured data obtained by a urine analysis system which implemented in our previous study. Generally. the reacted color of a reagent strip by urine analysis system often exhibit the color distortions due to nonlinear characteristics of the various devices that is the optic module mechanism. hardware, and surround circumstance. A color correction method for minimizing the color distortion play a few role in maintaining high accuracy and reproduction of the urine analysis system. In this work, we used the compensation method such as the shading correction, the characteristic curve extraction of RGB color by means of third order spline interpolation, and linear transformation using a reference color. In addition, 1931 CIE XYZ color space was used to compensate the color of the measured data by a standard reference system as colorimeter. A compensation matrix was obtained so that the output values of the urine analysis system is nearly equal to that of a standard reference system for identical color sample. Color correction obtained by a urine analysis system which implemented in our previous study exhibited a good color accuracy when it was compared with the reference data. Observed result from an experiments on ten items or a urinalysis strip that color difference or between two urine analysis system was 1.28.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.12
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• pp.1890-1897
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• 2022

In this paper, we design a navigation filter for an underwater glider. Underwater gliders are low-cost, reusable, and can be used for a long time. Two types of filters are designed considering characteristics such as small size, low cost, and low power. The navigation filter estimates the reference velocity of the underwater glider's body frame based on the minimum sensor output. The sensor configuration of the first filter consists of an accelerometer, a magnetometer, and a depth sensor. the second filter include extra a gyroscope in the same configuration. The estimated velocity is fused with the attitude, converted into the velocity of the navigation frame and finally the position is estimated. To analyze the performance of the proposed filter, analysis was performed using Monte Carlo numerical analysis method, and the results were analyzed with standard deviation (1σ). Standard deviations of each filter's position error are 334.34m, 125.91m.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.51-59
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• 2004

This paper proposes an improved six-color separation reducing the graininess in a middle tone region based on the standard deviation of the lightness and chrominance in S-CIELAB space. Graininess is regarded as visual perception for the fluctuation of the lightness of the light cyan and cyan or light magenta and magenta. In the conventional methods, the granularity is extremely heuristic and inaccurate due to the use of the visual examination score. Accordingly, this paper proposes a method to calculate the objective granularity for six color separation. First, we use the lightness, redness-greenness, and yellowness-blueness of the S-CIELAB space reflecting the spatial-color sensitivity of the human and normalize the sum of the three standard deviations. Finally, we apply the proposed granularity to the six color separation after assigning the granularity to the lookup table and obtain the result reducing the graininess in a middle tone region.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.1
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• pp.61-69
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• 1999

To promote the usability of CFD techniques for the basic hull form design, a hull surface mesh generating program, based on given station offsets and centerline profile, is developed. The new method employs non-uniform parametric splines with predetermined waterline end-shapes of natural spline, normal spline, ellipse, parabola hyperbola, and their combinations. Generated hull surface meshes can be utilized for potential panel method immediately and can be also used as a boundary grid surface for 3-D field grid system. Mesh topology chosen to represent hull surface can be transformed into a rectangle, which he1ps the flow solvers to transform surface meshes for the nonlinear free surface condition or to define the turbulence quantities. To prove the applicability, a container ship with bow and stem bulb is chosen, and the procedures generating hull surface meshes are described.

• Proceedings of the Korea Water Resources Association Conference
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• 1992.07a
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• pp.86-97
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• 1992

측류취수로와 만곡부가 있는 원형수로를 1:20으로 축척한 모형수로에 대해 수리모형실험을 수행하여 만곡부에서의 유속, 수위와 유황과 같은 수리학적 특성을 살펴보고, 측류취수로가 만곡부에 미치는 영향을 살펴보고자 한다. 도한 모형수로에 대해 ADI방법으로 천수방정식을 수치해석하여 얻은 만곡부에서의 수리학적 특성을 실험에 의한 것과 비교하여 사용된 수치기법으로 검증하였다. 대상이 된 전영역에 대하여 수리모형실험에서 얻어진 유속, 수위와 유황은 수치해석한 결과와 잘 일치한다. 그러나 직각좌표계를 사용함으로서 상대적으로 만곡부에서 단면축소 효과가 발생하므로 수치해석으로 얻어진 유속은 만곡부에서 실험치보다 약간 크게 나타나는데, 이것은 격자간격을 줄이면 개선되리라 판단된다. 수리모형실험과 수치해석 모두 만곡부 외측의 수위가 상승하고 내측의 유속이 빨라지는 만곡부의 특성을 잘 모사하고 있다. 만곡부 직전에 측류취수로가 있을 경우 측류취수로의 영향이 만곡수로내까지 미침을 알 수 있었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.21-30
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• 2004

This study deals with free vibrations of laminated composite structures with a channel section using finite element method. In this paper, the mixed finite element method using Lagrangian and Hermite interpolation functions is adopted and a high-order plate theory is used to analyze laminated composite non-prismatic folded plates with a channel section more accurately for free vibration. The theory accounts for parabolic distribution of the transverse shear stress and requires no shear correction factors supposed in the first-order plate theory. An 32×32 matrix is assembled to transform the system element matrices from the local to global coordinates using a coordinate transformation matrix, in which an eighth drilling degree of freedom (DOF) per node is appended to the existing 7-DOF system. The results in this study are compared with those of available literatures for the conventional and first-order plate theory. Sample studies are carried out for various layup configurations and length-thickness ratio, and geometric shapes of plates. The significance of the high-order plate theory in analyzing complex composite structures with a channel section is enunciated in this paper.

• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.323-328
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• 2004

The development of group-specific tissue probability maps (TPM) provides a priori knowledge for better result of cerebral tissue classification with regard to the inter-ethnic differences of inter-subject variability. We present sequential procedures of group-specific TPM and evaluate the age effects in the structural differences of TPM. We investigated 100 healthy volunteers with high resolution MRI scalming. The subjects were classified into young (60, 25.92+4.58) and old groups (40, 58.83${\pm}$8.10) according to the age. To avoid any bias from random selected single subject and improve registration robustness, average atlas as target for TPM was constructed from skull-stripped whole data using linear and nonlinear registration of AIR. Each subject was segmented into binary images of gray matter, white matter, and cerebrospinal fluid using fuzzy clustering and normalized into the space of average atlas. The probability images were the means of these binary images, and contained values in the range of zero to one. A TPM of a given tissue is a spatial probability distribution representing a certain subject population. In the spatial distribution of tissue probability according to the threshold of probability, the old group exhibited enlarged ventricles and overall GM atrophy as age-specific changes, compared to the young group. Our results are generally consistent with the few published studies on age differences in the brain morphology. The more similar the morphology of the subject is to the average of the population represented by the TPM, the better the entire classification procedure should work. Therefore, we suggest that group-specific TPM should be used as a priori information for the cerebral tissue classification.