• Structural Engineering and Mechanics
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• 제43권5호
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• pp.637-655
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• 2012

In this study, stochastic responses of a cable-stayed bridge subjected to the spatially varying earthquake ground motion are investigated by the finite element method taking into account soil-structure interaction (SSI) effects. The considered bridge in the analysis is Quincy Bay-view Bridge built on the Mississippi River in between 1983-1987 in Illinois, USA. The bridge is composed of two H-shaped concrete towers, double plane fan type cables and a composite concrete-steel girder deck. In order to determine the stochastic response of the bridge, a two-dimensional lumped masses model is considered. Incoherence, wave-passage and site response effects are taken into account for the spatially varying earthquake ground motion. Depending on variation in the earthquake motion, the response values of the cable-stayed bridge supported on firm, medium and soft foundation soil are obtained, separately. The effects of SSI on the stochastic response of the cable-stayed bridge are also investigated including foundation as a rigidly capped vertical pile groups. In this approach, piles closely grouped together beneath the towers are viewed as a single equivalent upright beam. The soil-pile interaction is linearly idealized as an upright beam on Winkler foundation model which is commonly used to study the response of single piles. A sufficient number of springs on the beam should be used along the length of the piles. The springs near the surface are usually the most important to characterize the response of the piles surrounded by the soil; thus a closer spacing may be used in that region. However, in generally springs are evenly spaced at about half the diameter of the pile. The results of the stochastic analysis with and without the SSI are compared each other while the bridge is under the sway of the spatially varying earthquake ground motion. Specifically, in case of rigid towers and soft soil condition, it is pointed out that the SSI should be significantly taken into account for the design of such bridges.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.883-898
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• 2019

This paper employs computational tools to predict power increase (or speed loss) and propulsion performances in waves of KVLCC2. Two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved using finite volume method; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. Sliding mesh method is applied to simulate the flow around an operating propeller. Towing and self-propulsion computations in calm water are carried out to obtain the towing force, propeller rotating speed, thrust and torque at the self-propulsion point. Towing computations in waves are performed to obtain the added resistance. The regular short head waves of λ/LPP = 0.6 with 4 wave steepness of H/λ = 0.007, 0.017, 0.023 and 0.033 are taken into account. Four methods to predict speed-power relationship in waves are discussed; Taylor expansion, direct powering, load variation, resistance and thrust identity methods. In the load variation method, the revised ITTC-78 method based on the 'thrust identity' is utilized to predict propulsive performances in full scale. The propulsion performances in waves including propeller rotating speed, thrust, torque, thrust deduction and wake fraction, propeller advance coefficient, hull, propeller open water, relative rotative and propulsive efficiencies, and delivered power are investigated.

• 한국음향학회지
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• 제21권5호
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• pp.503-509
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• 2002

입력단 및 출력단이 동심을 이루어 원형 확장관 안으로 연장되어 있는 소음기가 관내 전달 소음저감을 위해 널리 사용되고 있다. 이 소음기의 저주파수 영역에서의 소음저감 효과는 음파 진행 단면의 확장-축소와 입력단 및 출력단의 상대적 위치 등으로 발생되는 소음기의 리액티브 성분에 의해 설명이 된다. 본 논문에서는 입력단 및 출력단에 동심으로 배치된 연장관이 단순 팽창형 소음기 내부에 삽입되어 있는 경우에 대한 음향해석을 수행하였다. 해석방법으로는 음장을 분리좌표계로 표현될 수 있는 몇개의 경계 표면으로 나누고, 각 표면에서의 음압 및 입자속도를 정규화 된 음향 고유 모드로 전개하여 간단한 대수식으로 표현하였다. 이 해석적인 방법을 사용하여 소음기의 투과손실을 예측하였으며, 실험과도 잘 일치함을 관찰할 수 있었다.

• Nuclear Engineering and Technology
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• 제39권5호
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• pp.637-646
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• 2007

An UET (ultrasound excited thermography) has been used for several years for a remote non-destructive testing in the automotive and aircraft industry. It provides a thermo sonic image for a defect detection. A thermograhy is based On a propagation and a reflection of a thermal wave, which is launched from the surface into the inspected sample by an absorption of a modulated radiation. For an energy deposition to a sample, the UET uses an ultrasound excited vibration energy as an internal heat source. In this paper the applicability of the UET for a realtime defect detection is described. Measurements were performed on two kinds of pipes made from a copper and a CFRP material. In the interior of the CFRP pipe (70mm diameter), a groove (width - 6mm, depth - 2.7mm, and length - 70mm) was engraved by a milling. In the case of the copper pipe, a defect was made with a groove (width - 2mm, depth - 1mm, and length - 110 mm) by the same method. An ultrasonic vibration energy of a pulsed type is injected into the exterior side of the pipe. A hot spot, which is a small area around the defect was considerably heated up when compared to the other intact areas, was observed. A test On a damaged copper pipe produced a thermo sonic image, which was an excellent image contrast when compared to a CFRP pipe. Test on a CFRP pipe with a subsurface defect revealed a thermo sonic image at the groove position which was a relatively weak contrast.

• 대한한방부인과학회지
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• 제31권2호
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• pp.31-48
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• 2018

Objectives: This study was performed to observe the correlations between the results of ABR-2000 and DSOM / 3D-MAC to evaluate the feasibility of ABR-2000 as a oriental medical diagnostic criteria. Methods: We studied 547 women visiting ${\bigcirc}{\bigcirc}$ hospital from December 2012 to June 2015. The subjects were categorized in two groups, 'Hypotonia' and 'Non-Hypotonia' by the result of ABR-2000 and assessed the result of DSOM, 3D-MAC for each group. The differences of pulse wave factors by group also studied. Results: 1. There was no significant difference between two groups about the output frequency of pathogenic factors in DSOM while the result showed the higher correlation in Hypotonia group in terms of the companion tendency of pathogenic factors and syndromes formed by the combination of pathogenic factors. 2. The pulse waves of Hypotonia group were mostly slow, weak, tense and stiff than Non-Hypotonia group. Conclusions: 1. In Hypotonia group, yin deficiency (陰虛) factor was frequently accompanied and consumption (虛損) of various organs based on the yin deficiency (陰虛) was observed. It means chronic and severe condition of exhaustion syndrome (虛勞). 2. The result of 3D-MAC also means pathological feature of yin syndrome (陰 證) and consumption (虛損). Besides, lower scores of Body Surface Area (BSA), body weight, and Body Mass Index (BMI) were associated with body weakness (體瘦), a symptom of exhaustion syndrome (虛勞).

• Ocean and Polar Research
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• 제29권4호
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• pp.349-366
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• 2007

Seasonal variations of various physicochemical components (temperature, salinity, pH, DO, COD, DOC, nutrients-silicate, DIN, DIP) and potential limiting factor for phytoplankton primary production were studied in the surface water of semi-enclosed Masan Bay. Seasonal variations of nutrient concentrations, with lower values in summer and winter, and higher in fall, are probably controlled by freshwater loadings to the bay, benthic flux and magnitude of occurrence of phytoplankton communities. Their spatial distributional patterns are primarily dependent on physical mixing process between freshwater and coastal seawater, which result in a decreasing spatial gradient from inner to outer part of the bay. In the fall season of strong wave action, the major part of nutrient inputs (silicate, ammonium, dissolved inorganic phosphorus) comes from regeneration (benthic flux) at sediment-water interface. During the summer period, high Si:DIN and Si:DIP and low DIN:DIP relative to Redfield ratios suggest a N- and secondarily P-deficiency. During other seasons, however, silicate is the potential limiting factor for primary production, although the Si-deficiency is less pronounced in the outer region of the bay. Indeed, phytoplankton communities in Masan Bay are largely affected by the seasonal variability of limiting nutrients. On the other hand, the severe depletion of DIN (relatively higher silicate level) during summer with high freshwater discharge probably can be explained by N-uptake of temporary nanoflagellate blooms, which responds rapidly to pulsed nutrient loading events. In Masan Bay, this rapid nutrient consumption is considerably important as it can modify the phytoplankton community structures.

• 보존과학회지
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• 제32권4호
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• pp.449-457
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• 2016

2013년 인천 영흥도선에서 출수된 도기병은 해양생물과 주변 물질들이 단단하게 굳어져 표면 전체를 덮고 있던 상태였다. 표면과 구연부의 이물질을 물리적, 화학적인 방법으로 제거하니 표면에 파도무늬가 나타났으며 내부에서 황갈색 투명한 고체물질도 확인되었다. 이 논문은 도기병의 보존처리 과정과 내부 물질을 확인하는 분석과정을 설명했다. 도기병은 이물질 제거, 탈염, 복원 등의 순서로 보존처리를 진행했고, 없어진 구연부를 복원하여 원래 형태를 더 잘 이해할 수 있게 했다. 또한 내용물의 성분을 확인하기 위해 문헌을 토대로 통일신라(8~9세기)에 유통 가능했던 재료들을 푸리에변환 적외분광분석(FT-IR)과 가스크로마토그래피-질량분석기(GC-MS)로 비교분석하였다. 분석 결과 FT-IR과 GC-MS 모두 황칠과의 유사성을 확인하였다. 보존처리 후에 드러난 도기병의 파도무늬와 분석결과 확인된 황칠과의 유사성을 통해 영흥도선은 통일신라시대에 황칠을 싣고 가다가 난파된 선박임을 추측해볼 수 있다.

• 대한전자공학회논문지TC
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• 제46권2호
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• pp.114-125
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• 2009

정사각형 기판의 크기가 패치 안테나의 방사 특성에 미치는 영향에 대하여 연구하였다. 기판의 크기가 공진 주파수와 대역폭에 미치는 영향은 매우 작지만 방사 패턴에 미치는 영향은 매우 큼을 볼 수 있었다. 전방방사 이득과 이득이 최대가 되는 각도는 기판의 크기에 따라 거의 주기적으로 변화함을 볼 수 있었다. 전방방사 이득이 최대가 되는 변의 길이와 최소가 되는 변의 길이는 기판의 전기적 두께가 커질수록 작아짐을 볼 수 있었다. 기판의 전기적 두께가 클수록 기판 크기에 따른 전방방사 이득 변화 폭이 큼을 볼 수 있었다. 기판 크기에 따른 방사 패턴의 변화도 기판의 전기적 두께와 매우 밀접한 관계를 가짐을 볼 수 있었다.

• 대한전자공학회논문지TC
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• 제45권4호
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• pp.43-52
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• 2008

패치 안테나 주위에 mushroom 형태를 가지는 EBG 구조를 길이 방향, 폭 방향과 모든 방향으로 집적한 경우 구조 파라미터에 따른 패치 안테나의 방사 특성을 연구하였다. EBG 구조가 길이 방향을 따라 집적된 경우가 가장 방사 특성이 좋음을 볼 수 있었다. EBG 패치 edge에서 패치 안테나의 피드까지의 거리가 같은 경우가 패치 안테나의 중심까지의 거리가 같은 경우와 비교하여 E-평면 방사패턴이 대칭적이고 전방방사 크기가 커지고 후방방사 크기가 작아짐을 볼 수 있었다. 사용하는 EBG 구조의 주기 수가 4주기 이상이 되게 되면 방사특성 변화는 거의 발생하지 않음을 볼 수 있었다.

• 한국환경과학회지
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• 제24권4호
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• pp.371-381
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• 2015

In the mountain streams in Jeju Island, strong turbulence and roughness usually made it nearly impossible to utilize most of intrusive instrumentation for streamflow discharge measurements. Instead, a non-intrusive fixed electro-magnetic wave surface velocimetry (fixed EWSV: Kalesto) became alternatively popular in many representative streams to measure stream discharge seamlessly. Currently, Kalesto has shown noteworthy performance with little loss in flood discharge measurements and also has successfully provided discharge for every minute. However, Kalesto has been operated to regard its measured one-point velocity as the representative mean velocity for the given cross-section. Therefore, it could be highly possible to potentially encompass discharge measurements errors. In this study, we analyzed the difference between such Kalesto discharge measurements and other alternative concurrent discharge measurements such as Acoustic Doppler Current Profiler (ADCP) and mobile EWSV which were able to measure velocity in multi-points in the cross-section. Consequently, Kalesto discharge deviated from ADCP discharge in amount of 48% for relatively low flow, and more than 20% difference for high flow compared with mobile EWSV discharge measurements. These results indicated that the one-point velocity measured by Kalesto should be used as a cross-sectional mean velocity, rather it should be accounted for as an index-velocity in conjunction with directly measured cross-sectional mean velocity by using more reliable instrumentations. After inducing Kalesto Discharge Correction Coefficient (KDCC) that actually means relationship between index velocity and cross-sectional mean velocity, the corrected discharge from Kalesto was significantly improved. Therefore, we found that index velocity method should be applied to obtain better accuracy of discharge measurement in case of Kalesto operation.