• 대한토목학회논문집
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• 제6권1호
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• pp.25-33
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• 1986

일반적(一般的)으로 대규모(大規模) 하천(河川)은 저수로(低水路)와 고수부지(高水敷地)를 갖는 복단면수로(複斷面水路)로 되어있다. 복단면(複斷面) 수로(修路)에 대한 일반적인 해석방법은 저수로(低水路)에서 고수부지(高水敷地)로의 운동량(運動量) 전달(傳達)을 무시하였기 때문에 소통능력을 과대하게 평가(評價)하는 경향을 보여왔다. 따라서 본(本) 연구(硏究)에서는 운동량(運動量) 전달(傳達)을 고려하여 비대칭 고수부지(高水敷地)를 갖는 구형단면(矩形斷面)의 실험수로(實驗水路)에서 실험(實驗)하였으며, 단면의 여러 점에서 유속(流速)을 측정(測定)하고 유속분포(流速分布)로부터 경계층의 전단응력을 계산하여 윤변을 따라 이를 적분(積分)하여 겉보기 전단력을 구한다. 그리고 복단면(複斷面) 수로(水路)에서의 수리학적(水理學的) 특성(特性)을 실험단면(實驗斷面)의 유속분포(流速分布), 경계층의 전단응력(剪斷應力), 그리고 겉보기 전단력 등의 여러 가지 관계로부터 규명하였다.

• 대한토목학회논문집
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• 제32권6A호
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• pp.379-387
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• 2012

본 연구에서는 새로운 에너지 수확용 Multi-layer 블록 구조를 제시하고 고체 및 Shell 유한 요소를 사용하여 다양한 기하학적 형상 변화에 대한 자유진동 특성을 분석하고 압전 성능을 실험적으로 평가한다. 본 연구에서 제시하는 블록 구조에 대한 2차원 및 3차원 유한요소 모델은 해석의 정확성 뿐 만 아니라 전체 진동 모드를 정확히 보여준다는 점에서 장점을 갖는다. ABAQUS가 적용된 유한요소 모델은 다양한 Tip mass 및 PZT 변화에 따른 Multi-layer 블록 구조의 자유진동을 분석하기 위하여 사용되었다. 특히, 본 연구에서 제시한 결과는 블록구조 전체의 기하학적 형상, Tip mass 및 Hole의 유무, Tip mass 및 PZT의 위치변화 등에 대하여 국부 및 전체 진동 모드에 미치는 중요한 영향들에 대하여 초점을 둔다. 또한, 실험실 규모의 실제 모형 실험을 수행하여 개발한 에너지 블록구조의 발전성능을 평가하였다.

• Journal of Preventive Medicine and Public Health
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• 제7권2호
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• pp.377-381
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• 1974

Determination of lead in urine is important in industrial hygiene and toxicology. Dithizone method has been principally used for the determination of lead in urine, which gives accurate results in skilful hands but is usually complex and time-consuming. Atomic absorption spectrophotometry is a new simple method and several procedures have been described. However, the influences of pH and the presence of chelating agents during treatment of lead poisoning are not clear. The purpose of this study was to find out the effect of pH and chelating agents on the determination of lead using Shimadzu atomic absorption/flame spectrophotometer, model AA-610. The results obtained were as follows: 1. The atomic absorption spectrophotometry(AAS) could be applied without prior acid digestion to specimens in the absence of chelating agents. The absorbance at $2,170\;{\AA}$, though more sensitive, was more noisy electronically. Therefore, we selected the wavelength of $2,833\;{\AA}$ plus scale expansion. 2. The optimal pH was in the range from 2 to 3. 3. The sensitivity was $0.075{\mu}g/ml/%$ and detection limit was about $0.2{\mu}g/ml$. 4. In the presence of EDTA, lead could not be completely determined without prior acid digestion. 5. On specimens from patients receiving penicillamine therapy, a comparison was made between the values obtained with dithizone method and AAS method with prior acid digestion. The results of comparison showed a very good agreement.

• 신재생에너지
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• 제8권1호
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• pp.44-51
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• 2012

Due to a high tidal range of up to 10 m on the west coast of Korea, numerous tidal current projects are being planned and constructed. The turbine, which initially converts the tidal energy, is an important component because it affects the efficiency of the entire system. Its performance is determined by design variables such as the number of blades, the shape of foils, and the size of a hub. To design a turbine that can extract the maximum power on the site, the depth and duration of current velocity with respect to direction should be considered. Verifying the performance of a designed turbine is important, and requires a circulating water channel (CWC) facility. A physical model for the performance test of the turbine should be carefully designed and compared to results from computational fluid dynamics (CFD) analysis. In this study, a horizontal axis tidal current turbine is designed based on the blade element theory. The proposed turbine's performance is evaluated using both CFD and a CWC experiment. The sealing system, power train, measuring devices, and generator are arranged in a nacelle, and the complete TCP system is demonstrated in a laboratory scale.

• 한국공간정보시스템학회 논문지
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• 제1권1호
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• pp.29-37
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• 1999

공간정보의 구축이 활발해지면서 정보유통에 관심이 높아지고 있다. 정보유통은 각 시스템 마다 개별적 체계를 갖을 수 있으며 GIS의 경우도 마찬가지이다. 본 논문에서는 GIS의 공간정보 유통체계를 설정하고, 그 체계에 대한 정보망 성능평가 방식을 연구하기로 한다. 이를 위하여 인터넷 전산망의 유형별로 지리공간정보의 보관 내용 및 규모, 유통되는 정보의 량 등을 가정하고 현재의 인터넷 망을 기준으로 한 분석을 수행한다. 유통망의 성능 측정을 위한 도구로는 대기행렬모형을 적응하도록 하고, 다양한 형태의 유통서버가 운영될 경우 이들의 성능을 측정할 수 있는 방안을 제시한다. 이와같은 방법은 향후 GIS의 정보량과 정보 유통량이 예측되었을 경우 유통망의 구성 형태에 따른 다방면의 성능측정을 가능하게 하여 보다 우수한 성능의 유통체계의 수립을 도울 수 있다.

• 한국화재소방학회논문지
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• 제25권5호
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• pp.93-99
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• 2011

본 연구에서는 환기부족 구획화재에서의 일산화탄소 발생에 대한 FDS의 예측성능을 평가하기 위해 수치해석 연구를 수행하였다. ISO-9705 표준 화재실의 2/5 크기의 모형 내부에 위치한 메탄과 헵탄 화염의 거동을 FDS Ver. 5.5를 이용하여 해석하였다. 해석 결과를 기존의 실험 결과와 비교함으로써 고온 상층부에서 연소가스 농도의 예측에 대한 FDS의 성능을 평가하고 CO 생성율이 국부 위치에서의 CO 농도 예측에 미치는 영향을 분석하였다. 해석 결과로부터 이단반응 혼합분율 모델이 적용된 FDS Ver. 5.5가 CO 농도의 예측에 있어 이전 버전의 FDS에 비해 효과적임을 알 수 있었다. 또한 환기부족 화재조건에서 CO 생성율을 조절함으로써 실험값에 보다 근접한 CO 농도를 얻을 수 있었다.

• 아시안잔디학회지
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• 제20권1호
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• pp.93-105
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• 2006

최근 많은 수의 골프장 건설로 인하여 국토의 상당면적이 원지형의 변화 또는 파괴되고 있으며 주변 생태계가 급속한 변이를 겪고 있다. 골프코스 건설을 위해서는 정밀하고 효율적인 설계를 요하지만 기존의 통상적 설계방식으로는 사업의 방대성으로 인한 설계자료의 처리에 한계를 가지고 있었다. 특히 공사 후의 경관 변화에 대한 예측이나 환경영향 저감대책에 대하여 적절한 대안을 제시할 적절한 수단이 없었다. 따라서 이러한 문제점을 해결하기 위하여 지형정보시스템(GIS)을 골프코스 설계에 적용하여 건설에 따른 물리적 영향을 최소화시킬 수 있는 친환경적인 골프코스 설계 기법개발에 대하여 연구하였다. 연구된 내용은 지형정보시스템을 기초자료입력 단계에서부터 최종 성과물 단계까지 적용시켜 전 설계과정을 전산화하며, 부수적으로 골프 경기의 기능적 효과 증대 토지이용의 적정성, 코스유지 관리의 용이성 등을 사전 검토할 수 있는 친환경적 전산설계기법을 개발 연구하였다.

• Smart Structures and Systems
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• 제20권2호
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• pp.175-180
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• 2017

The load-carrying capacity and structural behavior of concrete-filled steel tube (CFST) structures is highly influenced by the grouting compactness in the steel tube. Due to the invisibility of the grout in the steel tube, monitoring of the grouting progress in such a structure is still a challenge. This paper develops an active sensing approach with combined piezoceramic-based smart aggregates (SA) and piezoceramic patches to monitor the grouting compactness of CFST bridge structure. A small-scale steel specimen was designed and fabricated to simulate CFST bridge structure in this research. Before casting, four SAs and two piezoceramic patches were installed in the pre-determined locations of the specimen. In the active sensing approach, selected SAs were utilized as actuators to generate designed stress waves, which were detected by other SAs or piezoceramic patch sensors. Since concrete functions as a wave conduit, the stress wave response can be only detected when the wave path between the actuator and the sensor is filled with concrete. For the sake of monitoring the grouting progress, the steel tube specimen was grouted in four stages, and each stage held three days for cement drying. Experimental results show that the received sensor signals in time domain clearly indicate the change of the signal amplitude before and after the wave path is filled with concrete. Further, a wavelet packet-based energy index matrix (WPEIM) was developed to compute signal energy of the received signals. The computed signal energies of the sensors shown in the WPEIM demonstrate the feasibility of the proposed method in the monitoring of the grouting progress.

• Computers and Concrete
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• 제22권1호
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• pp.123-132
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• 2018

Reinforced concrete (RC) columns which are the main vertical structural members are exposed to several static and dynamic effects such as earthquake and wind. However, impact loading that is sudden impulsive dynamic one is the most effective loading type acting on the RC columns. Impact load is a kind of impulsive dynamic load which is ignored in the design process of RC columns like other structural members. The behavior of reinforced concrete columns under impact loading is an area of research that is still not well understood; however, work in this area continues to be motivated by a broad range of applications. Examples include reinforced concrete structures designed to resist accidental loading scenarios such as falling rock impact; vehicle or ship collisions with buildings, bridges, or offshore facilities; and structures that are used in high-threat or high-hazard applications, such as military fortification structures or nuclear facilities. In this study, free weight falling test setup is developed to investigate the behavior effects on RC columns under impact loading. For this purpose, eight RC column test specimens with 1/3 scale are manufactured. While drop height and mass of the striker are constant, application point of impact loading, stirrup spacing and concrete compression strength are the experimental variables. The time-history of the impact force, the accelerations of two points and the displacement of columns were measured. The crack patterns of RC columns are also observed. In the light of experimental results, low-velocity impact behavior of RC columns were determined and interpreted. Besides, the finite element models of RC columns are generated using ABAQUS software. It is found out that proposed finite element model could be used for evaluation of dynamic responses of RC columns subjected to low-velocity impact load.

• Earthquakes and Structures
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• 제17권6호
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• pp.635-647
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• 2019

Tests and theoretical studies for seismic responses of a transmission tower-line system under coupled horizontal and tilt (CHT) ground motion were conducted. The method of obtaining the tilt component from seismic motion was based on comparisons from the Fourier spectrum of uncorrected seismic waves. The collected data were then applied in testing and theoretical analysis. Taking an actual transmission tower-line system as the prototype, shaking table tests of the scale model of a single transmission tower and towers-line systems under horizontal, tilt, and CHT ground motions were carried out. Dynamic equations under CHT ground motion were also derived. The additional P-∆ effect caused by tilt motion was considered as an equivalent horizontal lateral force, and it was added into the equations as the excitation. Test results were compared with the theoretical analysis and indicated some useful conclusions. First, the shaking table test results are consistent with the theoretical analysis from improved dynamic equations and proved its correctness. Second, the tilt component of ground motion has great influence on the seismic response of the transmission tower-line system, and the additional P-∆effect caused by the foundation tilt, not only increases the seismic response of the transmission tower-line system, but also leads to a remarkable asymmetric displacement effect. Third, for the tower-line system, transmission lines under ground motion weaken the horizontal displacement and acceleration responses of transmission towers. This weakening effect of transmission lines to the main structure, however, will be decreased with consideration of tilt component.