• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.17 no.6
• /
• pp.105-112
• /
• 2003

Diode rectifier which can't be controlled output voltage and phase control converter as AC/DC converter have low power factor and harmonics of lower order in the line current. In this paper, three phase PWM(Pulse Width Modulation) AC/DC boost converter is studied to solve these problems. The characteristics of a proposed converter are to control the phase of current without current sensor as a very simple control algorithm using circuit parameters only and to apply sinusoidal PWM method with fixed switching frequency due to a difficult design of input filter and switching device. We simulate for the proposed algorithm that high power factor is achieved and DC link voltage has fast dynamic response without ripple in rectifying and regenerating operation. As a result of experiment with circuit parameter(inductor, capacitor) decided in simulation, the proposed converter had high power factor and reduction of low order harmonics as against diode rectifier.

• Journal of Korean Society of Transportation
• /
• v.22 no.3 s.74
• /
• pp.159-166
• /
• 2004

The capacity concept presented in the Highway Capacity Manual is for steady-state traffic flow assuming that there is no restriction in downstream flowing, which is traditionally used for planning, design, and operational analyses. In the congested traffic condition, the control objective should be to keep the congested regime from growing and to recover the normal traffic condition as soon as possible. In this control case, it is important to predict the spatial-temporal pattern of congestion evolution or dissipation and to estimate the throughput reduction according to the spatial-temporal pattern. In this context, the new concept of dynamic capacity for managing congested traffic is developed in terms of spatial-temporal evolution of downstream traffic congestion and in view of the 'input' concept assuming that flow is restricted by downstream condition rather than the 'output' concept assuming that there is no restriction in downstream flowing (e.g. the mean queue discharge flow rate). This new capacity is defined as the Maximum Sustainable Throughput that is determined based on the spatial-temporal evolution pattern of downstream congestion. And the spatial-temporal evolution pattern is estimated using the Newell's simplified q-k model.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.32 no.6
• /
• pp.516-523
• /
• 2020

Since the aging of coastal structures have been increased, the researches about the reinforcements of the existing aged structures are needed. Especially, the existing armor units placed on rubble mound structures should satisfy the stability against the increased design wave conditions. However the researches about these design problems have not been performed. In this study, the hydraulic model tests to investigate the stability number about the additionally placed armor unit were conducted. The main armor unit is a Tetrapod. The test results showed that the stability number (Kd) for additionally placed armor units(Tetrapod) increased up to maximum 10% comparing with that for 2 layers tetrapod (Kd = 8) within these test conditions with the pattern placing for existing armor layers and the stable armor layer slope for the non overtopping condition.

• 한국방재학회:학술대회논문집
• /
• 2011.02a
• /
• pp.55-55
• /
• 2011

연안 및 해안공학의 발달과 더불어 부유식방파제의 기능적 효율성이 중요시 되고 있다. 흔히 사용되어오던 착저식방파제는 설치에 많은 시간과 경비가 소요되고 환경 및 생태계에 많은 변화를 줄 수 있으며, 설치 예정지의 수리학적 특성 등의 여건에 많은 제약을 받는 단점이 있다. 부유식방파제는 일본 등의 선진국을 중심으로 활용이 잦아지고 있는 방파제로서 수면 위에 설치되기 때문에 수중 생태계에 미치는 영향이 적은 친환경방파제이다. 또한 기존에 시공된 중력식방파제와는 달리 수심에 제한을 덜 받고, 공사기간이 짧기 때문에 경제적이다. 실제 시공사례로는 2007년 마산 원전항에 완공된 부유식방파제가 대표적이며, 지금까지도 부유식방파제에 대한 여러 연구자들의 관심이 증가하고 있는 추세이다. 방파제뿐만 아니라 우리나라처럼 국토의 면적이 작은 지역에서 증가하는 해상물동량을 소화하기 위해서 부유식방파제 등을 이용한 항만의 시공이 필요한 실정이다. 이러한 부유식방파제의 분석적인 측면에 있어서 수치해석은 파랑과 구조물의 상호작용을 해석하는 데 한계가 있으며, 부유식방파제 단면형상을 정확하게 재현할 수 없으므로, 수리모형실험을 통한 부유식방파제의 연구가 필요할 것으로 판단된다. 최근 기술의 발달로 인한 유동장 해명이 가능해 졌으며, PIV(Particle image velocimetry) 및 LDV시스템은 다양한 분야에서 응용되고 있다. 특히, LDV시스템은 측정하려는 한 지점에 대하여 레이저 빔을 단면(Cross-section)으로 만들고 입자의 산란광을 후방산란(Back scatter)으로 받아서 도플러 효과를 이용, 속도에 대한 주파수를 획득하며, 유속을 측정하는 장비로 매우 높은 정확도와 비접촉식 이라는 장점을 가지고 있다. 또한, PIV 시스템에 비하여 측정시간이 오래 걸리는 반면 데이터를 가공하지 않고 활용할 만큼 높은 정확성을 가지고 있다. 본 연구에서는 수리모형실험을 통하여 단독형, 2열형 및 3열형 부유식방파제의 형상, 흘수 및 거리를 변화시키며 유동장을 수집하였으며, 방파성능에 따른 와의 생성 및 소멸시점에서의 파랑변형과의 관계를 분석하였다. 방파제의 형상과 흘수를 달리하여 수리모형실험을 수행하였으며, 와류의 상관관계를 분석하였다. 또한, 연직 2차원 Navier-Stokes 방정식 모형을 이용하여 수치모형실험을 수행하였으며, 수치모형실험 결과와 수리모형실험 결과를 비교 분석하였다. 후방방파제에서 발생되는 파랑은 입사파의 주기가 길어질수록 상대적으로 커지는 현상을 보였으며, 흘수심이 깊어질수록 전방방파제 입사 면에서 자유 수면이 높게 관측되는 결과를 보였다. 또한, 비교적 장주기파랑에 해당하는 입사파랑의 경우 전달파고비 산정에 있어서 설계기준인 0.5를 대다수 초과하는 반면, 3열형 구조에서는 대부분이 0.5이하로 상당히 높은 방파성능 결과를 나타내었다.

• The Journal of Engineering Geology
• /
• v.31 no.3
• /
• pp.381-393
• /
• 2021

Physical, mechanical, hydraulic, and geophysical tests were applied to validate methods of inspecting the effectiveness of grouting on an agricultural reservoir dam. Data obtained from series of in situ and laboratory tests considered four stages: before grouting; during grouting; immediately after grouting; and after aging the grouting for 28 days. The results of SPT and triaxial tests, including the unit weight, compressive strength, friction angle, cohesion, and N-value, indicated the extent of ground improvement with respect to grout injection. However, they sometimes contained errors caused by ground heterogeneity. Hydraulic conductivity obtained from in situ variable head permeability testing is most suitable for identifying the effectiveness of grouting because the impermeability of the ground increased immediately after grouting. Electric resistivity surveying is useful for finding a saturated zone and a seepage pathway, and multichannel analysis of surface waves (MASW) is suitable for analyzing the effectiveness of grouting, as elastic velocity increases distinctly after grouting injection. MASW also allows calculation from the P- and S- wave velocities of dynamic properties (e.g., dynamic elastic modulus and dynamic Poisson's ratio), which can be used in the seismic design of dam structures.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.2
• /
• pp.159-167
• /
• 2017

The purpose of this study is to accurately estimate the wind-induced responses of a tall building structure for using the estimated responses in the process of calculating the optimal force of an active control device. Kalman filter was used for the estimation process and a 3-storied model structure on a shaking table was tested for the verification of the estimation accuracy. The system matrices of the model were constructed based on the mode parameters obtained by the system identification. The estimated displacement matched up well with the measured one. Finally, the wind-induced responses of a real 39-storied building structure excited by the typhoon MUIFA were estimated.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2006.04a
• /
• pp.76-81
• /
• 2006

창녕군 증산리 지역은 신규 취수원 확보 일환으로 강변여과 방식 취수 가능성이 한국수자원공사에 의해서 평가되고 있는 지역이다. 강변여과 방식 취수의 타당성 평가를 위해 현장 지질조사, 시추조사, 전기 비저항 탐사 및 고해상도 탄성파 탐사를 수행하였다. 또한 대상 연구지역에서의 개략적 취수 가능량 산정을 위해 모델링 평가가 수행되었으며, 개별 정호에 대한 양수량 산정을 위해 시험 정호를 설치하였다. 현장 시추 조사와 시료에 대한 입도 분석 결과, 연구 지역의 충적층 두께는 35m 전후이며, 주 대수층 구간은 지표하 $25{\sim}35m$인 것으로 추정되었다. 또한 주 대수층 구간의 수리전도도는 $10^{-2}cm/sec$ 이상으로 주로 모래섞인 자갈층으로 구성되어있는 것으로 평가되었다. 또한 전기비저항 조사 결과는 부분적으로 매우 낮은 비저항 분포 지층을 보여주고 있으며, 이는 주로 실트 및 점토로 된 지층이 부분적으로 퇴적되어 있음을 지시하며, 고해상도 탄성파 탐사 결과는 전반적으로 지하수위는 지표하부 5m 전후에 분포하고, 충적층의 하부 경계는 35 내지 45m인 것으로 해석되었다. 지하수 모델링을 통해, 취수 목표량인 180,000톤/일은 주대수층까지의 지하수위 강하 없이 확보 가능할 것으로 평가되었다. 또한 개별 정호의 산출 특성을 평가하기 위해 시험 정호를 설치하여, 실제 2,700톤/일 예비 양수 시험을 수행하였다. 예비 양수 시험 결과, 양수정에서의 수위 강하는 개략 10m, 양수정관측정에서는 약 0.3m의 수위강하만이 관찰되었으며, 양수 영향권이 수 십 m를 넘지 않을 것으로 판단되었다.서의 S97과 JBR의 세포감염 억제율은 3.85%와 3.63%로 나타났다. $textsc{k}$-casein, CU는 로타바이러스 S97과 JBR에 대해 농도 2000UM에서 97%이상의 억제효과를 나타냈으며, sialic acid는 억제효과가 거의 없었다. K-casein, GMP는 송아지뿐만 아니라 유아의 로타바이러스에 의한 설사를 억제할 수 있을 것으로 기대된다.을 향상하기 위해서는 이러한 부위에 대한 미생물 오염을 낮출 수 있는 세심한 현장 품질관리가 필요하다.en and adolescents, analysed by country, age group and gender. The paper discusses the places young consumers can turn to in trying to fulfil their growing consumer needs. It also examines how much money is at their disposal. It then concludes by considering the influence of "financial socialization" on how young people deal with money.nsumption visions based on the various perspectives, consumers are influenced in the apparel buying decision-making. Many subjects reported experiencing positive affect when imagining positive outcomes of produc

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.26 no.1
• /
• pp.25-32
• /
• 2014

Offshore wind power structures are subject to coastal hydrodynamic loading such as wind and wave loads. A considerable number of turbines have been installed in Europe, but so far none in Korea. Interest in offshore wind energy is growing in Korea, and it is expected that projects will reach the design stage in the near future. This paper discusses the level of structural reliability implied by the design rules of ABS(2010, 2013) and IEC(2009). Metocean conditions in 4 Korean seas(Gunsan, HeMOSU 1, Mokpo, Jeju) were used in the calibrations to calculate the aerodynamic and hydrodynamic loads as well as the structural responses of the typical designs of offshore wind turbines. Due to the higher variability of the wind and wave climate in hurricane-prone areas, applying IEC strength design criteria in combination with Korea west sea conditions could result in a design with much lower reliability index than what is anticipated from a design in European waters. To achieve the same level of safety as those in European waters, application of ABS 100 year design standards are recommended. Level-1 reliability-based design suitable for the Korean sea state conditions should be introduced because the IEC standards does not consider the typhoon effects in depth and the ABS standards is a WSD design method. In addition, the design equation should be established based on the statistical characteristics of the wind and wave loads of the Korean sea areas.

• Geotechnical Engineering
• /
• v.9 no.1
• /
• pp.7-20
• /
• 1993

The first Korean earthquake resistant design code was enacted in 1988. In the code, the soil factor which takes into account both the soil amplification factor and the soil -structare interaction effect is divided into three groups : soil factor, 5 : 1.0, 1.2 and 1.5. In order to assist in choosing the soil factors appropriately in the earthquake resistant design, the local site effects on the based shear force induced by earthquakes are considered in depth for typical soil conditions in Korea. The depth of the alluvial and/or weathered zone is usually not deep and the fresh rock is found at depth shallower than 20 meters, and even at about 10 meters around Seoul. One dimensional wave propagation theory and the elastic half space method are used to obtain the soil -structure interaction effect as well as the soil amplification effect. The kinematic interaction effect due to scattering of waves by pile foundation is also considered. Finally, the soil factor is recommended for each soil condition from loose state to dense, and also from shallow soil depth to deep, so that the designer can choose the factor with-out difficulty.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.9 no.3
• /
• pp.119-129
• /
• 2004

The surges caused by the typhoon “Maemi” which struck the southern coast of Korea are analysed in Kwangyang Bay on September 12, 2003. The deviations of the high water level were 93∼108 cm and the maximum deviations of the water level (maximum surges) were 176∼196 cm in Kwangyang Bay during the typhoon “Maemi”. The major parameters of the maximum deviations of the water level are as follows: Analysis shows that the pressure drop increased the sea level by 59 cm, the flood of the Sumjin River by 4-5 cm and the external surge propagation and wind setup by 113∼132 cm. During the typhoon “Maemi”, the highest high water recorded in Kwangyang Port (PT3) is 460 cm, which is higher by 5 cm than the highest high water (455 cm) with return period of 100 years estimated in planning the Kwangyang steelworks (POSCO) grounds and higher by 15 cm than the observed highest high water (445 cm) recorded during the typhoon “Thelma” on 1987. Thus, the highest high water caused by the typhoon “Maemi” is higher than the extreme highest high water for the last 20 years in Kwangyang Bay.