• Composites Research
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• v.25 no.6
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• pp.217-223
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• 2012

This study investigates a geometrical nonlinear dynamic behaviors of laminated skew plates made of advanced composite materials (ACM). Based on the first-order shear deformation plate theory (FSDT), the Newmark method and Newton-Raphson iteration are used for the nonlinear dynamic solution. The effects of cutout sizes, skew angles and lay up sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite plates with or without central cutouts, and the new results reported in this paper show the significant interactions between the cutout, skew angles and layup sequence in the laminate. Key observation points are discussed and a brief design guideline of skew laminates is given.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.35-41
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• 1997

A series-fed microstrip array antenna of beamwidth $10^{\circ}$, squint angle $80^{\circ}$ and SLL -15 dB below is designed. Series-fed arrays are formed by interconnecting all the elements by high-impedance transmission lines and feeding the power at the first element and it is a traveling-wave antenna which is terminated with a matched load. Radiation patterns and impedance matching of the antenna are analyzed by Ensemble 4.0, which is a popular software package for designing printed antennas and arrays. The squint angle of beam can be controlled by the spacing between the elements. The major advantages of series-fed array antennas are that feed arangement is compact and the losses associated with the feeding network are less than those of a corporate feed type. The antennas are fabricated on the RT/Duroid Laminates of 62 mil thickness. The experimental results are very close to the specifications to be designed.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.2
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• pp.83-93
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• 2017

A numerical analysis is made of the fluid flow and heat transfer characteristics in the corrugated structure that traps the spent air in the corrugations between impinging jets to reduce crossflow effects on downstream jets in the array. All computations are performed by considering three-dimensional, steady state, and incompressible flow by using the ANSYS-CFX 15.0 code. Averaged jet Reynolds number is 10,000. The oblique angles of impingement jets on the spanwise section are $70^{\circ}$, $80^{\circ}$, $90^{\circ}$, and the oblique angles of impingement jets on the streamwise section are $70^{\circ}$, $90^{\circ}$, $110^{\circ}$. The investigation focuses on the oblique angle influence of impinging jet array on the fluid flow and heat transfer characteristics of a corrugated structure.

• 발명특허
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• v.27 no.5 s.311
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• pp.68-74
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• 2002

본 발명은 키토산으로 이루어진 무수히 많은 갯수의 박막필름이 시트 평면에 수직, 수평 또는 경사 방향으로 일정간격의 공간을 유지하면서 적충되어서 라멜라구조를 형성하고 이 박막필름들이 일정한 간격으로 가지런히 나열되어 형성된 키토산 마이크로 플레이크로 이루어진 층상 격막시트에 관한 것이다. 두께 $1\mu{m}$내지 $50\mu{m}$로 라멜라구조를 이루는 키토산 박막필름이 $1\mu{m}$내지 $10000\mu{m}$의 공기간격을 두고 누적층을 형성하고 시트평면과$0^{\circ}C$내지$180^{\circ}C$사이의 일정 각도로 균일하게 배열되어 있어 수직, 수평 또는 경사방향으로 키토산 박막필름이 가지런히 배열되어 있는 키토산으로 조성된 수용성 층상 격막시트에 관한 것이다. 본 발명은 키토산을 약산성 액상에서 용해, 숙성 시켜 추출 고화 시키는 과정에서 수직, 수평 및 경사방향으로 키토산 마이크로 플레이크가 층상 라멜라구조를 이루는 키토산 격막시트를 형성시켜 줌으로 임상의학적 적용시 각각의 키토산 박막필름 사이의 균일한 공간으로 다양한 약물의 적용이 가능하며 특히 액상의 약재를 적용시 모세관의 원리에 따라서 약물이 원활하게 공급되는 약전성이 매우 우수하고 약물의 포집성이 획기적으로 부과된 재료로 사용될 수 있으며 키토산을 용해시켜 이용하는 산업에서 물에 신속하고 완전한 용해특성을 나타내는 키토산 원료물질로 사용될 수 있는 것이다.

• Journal of Institute of Convergence Technology
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• v.1 no.2
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• pp.16-24
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• 2011

The angular electrostatic microactuator using skewed electrode array (SEA) scheme was proposed. The moving and fixed electrodes are arranged to make the driving force perpendicular to the rotating moment of arm. By changing the electrode overlap length, the magnitude of electrostatic force and stable displacement will be changed. In order to optimize the design, electrostatic FE analysis were carried out and the empirical force model was established for SEA. Simulation was performed to make the comparison between conventional actuators and SEA. The proposed SEA generates actuating torque 2 times greater than a comb-drive and stable actuator displacement 40% greater than a parallel plate type actuator. The angular electrostatic microactuator using skewed SEA scheme was designed and fabricated using SoG process.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.433-433
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• 2021

본 연구는 개수로 흐름에서 조류발전단지의 터빈 최적 배열의 거시적 특성에 관한 연구를 수행하였다. 천수방정식을 통해 직사각형 개수로의 흐름장을 해석하였고, 상류와 하류단에 대해 각각 유입경계조건(inlet boundary condition)과 Flather 형식의 개방경계조건(open boundary condition)을 부여하여 일정 유량으로 흐르는 개수로 흐름을 구현하였다. 더불어, Strickler의 법칙을 확장한 반력공식을 연계하여, 개수로 흐름에 대한 조류 터빈의 영향을 반영하였다. 주어진 상류의 흐름 조건에 대해 조류발전량을 최대로 하는 최적 배열을 구하기 위해 터빈 반력모형을 연계한 천수방정식, 터빈간 최소간격, 그리고 발전단지영역을 제한조건으로 하는 발전량 최대화 문제를 구성하였다. 여기서 조류 터빈의 위치를 나타내는 벡터를 설계변수로 두었는데, 설계되는 터빈의 수가 증가함에 따라 최적화 문제의 계산량이 증가하지 않도록 수반법(adjoint method)을 경사도기반법(gradient-based method)에 연계한 방법이 이용되었다. 다수의 터빈초기배치로 상당한 수치실험이 수행되었고, 발전량 최대화를 이루도록 최적화된 터빈의 배치들이 큰 규모에서 고유한 형상으로 수렴함을 확인하였다. 이러한 특성은 발전단지의 너비와 터빈의 최소간격의 함수로 정의된 무차원수 E를 바탕으로 설명되었다. 구체적으로, E가 1보다 작을 때에는 선형배열이 최적배열로 나타났고, E가 1을 넘어 점차 커짐에 따라 하류에 오목한 형상을 보이다가 V-형태로 발전하는 양상을 보였다. 또한, 어느 임계 수 이상의 터빈이 배치되는 경우 일열 배열을 유지하지 못하고 이열 배열로 분리됨이 관찰되었다.

• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.255-263
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• 2006

In an electrical tomographic survey using an inclined borehole with a pole-dipole array, we must consider several factors: a singular point associated with zero potential difference, a spatial discrepancy between electrode and nodal point in a model due to a inclined borehole, and a variation of geometric factors in connection with a irregular topography. Singular points which are represented by the normal distance from current source to the ground surface can be represented by serveral regions due to a irregular topography of ground surface. The method of element division can be applied to the region in which the borehole is curved, inclined or the distance between the electrodes is shorter than that of nodal points, because the coordinate of each electrode cannot be assigned directly to the nodal point if several electrodes are in an element. Test on a three-dimensional (3-D) synthetic model produces good images of conductive target and shoves stable convergence.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06d
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• pp.84-87
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• 1998

소음원 탐지는 환경 소음제어, 음향 표적 탐지 및 음성 통신 등의 광범한 분야에 적용되는 연구분야로 Beamforming 기술, 상관함수법, 음향인테시티법등 다양한 기술이 적용되는 분야이다. 본 연구에서는 최근 그 응용 범위가 증대고고 있는 Matched Filterig 기술을 이용한 소음원 탐지기술의 수치 해석 결과로 종래 연구가 현상적인 특성의 1차적 응용이라면 본 연구는Matched filtering 의 공간 분해능 특성을 해석한 것으로 배열 중심선과 소음원이 이루는 경사각에 따른 분해능 특성을 중심으로 논의되었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.161-169
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• 2017

The present study investigated the effect of the rib arrangement and a guide vane for enhancing internal cooling of the blade. Two types of rib arrangements were used in the first and second passage in parallel. Aspect ratio of the channel was 5 and a fixed Reynolds number based on hydraulic diameter was 10,000. The attack angle of rib was $60^{\circ}$, rib pitch-to-height ratio (p/e) was 10, and the rib height-to-hydraulic-diameter ratio ($e/D_h$) was 0.075. The effect of an interaction between Dean vortices and the secondary vortices from the first passage was observed. Overall, the attack angle of rib in the first passage was dominant factor to heat transfer and flow patterns in turning region. Also, the channel with a guide vane showed enhanced heat transfer at the tip surface with reducing flow separation and recirculation.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.49-55
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• 2007

Various away methods are required in the electrical resistivity survey in order to find anomalous zone reliably. Array methods are classified as several groups. Among these group, a curved survey along the fixed elevation is designed to increase the mobility of men and survey equipments at the rough terrain. Another method is performed at the survey using inclined, curved, and horizontal boreholes. A survey can also be conducted in an arbitrary location by measurements of potentials for a multi sources. The complex data acquired using various away methods are represented by a correct images reconstructed from the 3D inversion. The element division is applied to the region in which the boreholes are curved and inclined because of a spatial discrepancies between the coordinate of each electrode and the nodal point in a model. The resistivity images are obtained from a good agreement for the anomalous zones in open slope and in survey using an inclined borehole.