• 조명전기설비학회논문지
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• 제19권1호
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• pp.169-174
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• 2005

지금까지의 고조파 필터는 중성선 리액터와 지그재그결선의 영상 고조파 전류를 제거하였으나, 부하율에 따라 고조파 저감율이 변하여 경부하에서는 고조파 저감율이 낮아지는 특성이 있고, 중성선 리액터 과열로 중성선 단선 위험의 문제가 발생하였다. 본 Zig-Zag 결선 및 Open Delta 방식을 이용한 새로운 고조파 저감장치(HANOS)는 Zig-Zag 결선의 Core Block내에 추가로 Open Delta 방식을 결선하여 중성선에 연결함으로써 중성선에 흐르는 영상 고조파 전류가 과열 없이 안전하게 제거되는 것을 시험 분석한 결과로 증명하였다.

• 문화기술의 융합
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• 제6권3호
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• pp.443-448
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• 2020

본 연구에서는 영종대교를 구성하고 있는 교량형식(트러스교, 현수교)별 열차종류(AREX, AREX Express, KTX, KTX-Sancheon) 및 열차속도가 강직결 궤도구조의 동적거동에 미치는 영향을 분석하고자 현장측정을 수행하였다. 현장측정결과를 바탕으로 궤도충격계수 및 열차주행안정성(탈선계수, 윤중감소율, 레일두부횡변위)을 국내, 외 관련기준 및 법규와의 비교하여 영종대교 교량상 강직결 궤도구조의 동적거동에 영향을 미치는 열차하중 및 속도의 효과를 분석하였다. 연구결과, 영종대교 교량형식별 궤도의 동적거동의 차이는 뚜렷하지 않으나 열차하중의 크기에 보다 직접적인 영향을 받는 것으로 분석되었다. 따라서 향후 열차속도 증가에 따른 궤도충격계수의 증가와 이에 따른 궤도부담력의 증가수준을 감안한 영종대교 강직결 궤도구조의 보강방안 수립이 필요할 것으로 판단된다.

• 한국구조물진단유지관리공학회 논문집
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• 제13권6호통권58호
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• pp.183-191
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• 2009

본 연구에서는 지진시 nailed-soil 굴착벽체의 안전율과 거동특성에 대하여 제시하였다. 시간이력해석을 이용하여 정적하중과 지진하중을 받는 nailed-soil 굴착벽체 전면부의 수평변위, 축력, 전단력, 모멘트를 해석하였다. Dawson과 Roth가 제안한 전단강도 감소기법에 바탕을 둔 안전율을 지진시 nailed-soil 굴착벽체의 안전율 계산에 사용하였다. 제안된 방법에 의한 안전율을 기존의 연구에서 산정된 안전율과 비교하여 그 타당성을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.189.2-189.2
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• 2010

The purpose of this study is fatigue damage assessment for large sized casting parts (hub and mainframe) of the 3MW offshore wind turbine by computer simulation. Hub and mainframe durability assessment is necessary because wind turbine have to guarantee for 20 years. Fatigue life evaluation must be considered all of fatigue load conditions as the components are wind load transmission path. Palmgren-Miner linear damage accumulation hypothesis is applied for fatigue life estimation with stress-life approach. S-N curve for the spheroid graphite cast iron EN-GJS-400-18-LT is derived according to durability guidelines. Reduction factors were applied for survival probability, surface roughness, material quality and partial safety factor according to Germanischer Lloyd rules. To calculate fatigue damage, stress tensors, extracted from the unity load calculation from ANSYS is multiplied with time track of fatigue loads extracted from GH bladed. Damage accumulation is performed with all of fatigue load conditions at each finite element nodes. In this study maximum nodal damage value is under 1.0. casted parts are safe. This research was financially supported by the Ministry of Knowledge Economy(MKE), Korea Institute for Advancement of Technology(KIAT) and Honam Leading Industry Office through the Leading Industry Development for Economic Region.

• Geomechanics and Engineering
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• 제14권2호
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• pp.115-129
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• 2018

This paper presents a set of results of plate load tests that imposed incremental cyclic loading to a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) at large model scale. Loading and unloading cycles were applied with amplitudes incrementally increasing from 140 to 700 kPa in five steps. A thickness of the RSM layer of approximately 0.4 times the footing diameter was found to deliver the minimum total and residual settlements, irrespective of the level of applied cyclic load. Both the total and residual settlements decrease with increase in the number of RSM layers, regardless of the level of applied cyclic load, but the rate of reduction in both settlements reduces with increase in the number of RSM layers. When the thickness of the RSM layer is smaller, or larger, settlements increase and, at large thicknesses may even exceed those of untreated soil. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. With the inclusion of RSM layers, the coefficient of elastic uniform compression decreases by a factor of around 3-4. A softer response was obtained when more RSM layers were included beneath the footing damping capacity improves appreciably when the sand bed incorporates RSM layers. Numerical modeling using "FLAC-3D" confirms that multiple RSM layers will improve the performance of a foundation under heavy loading.

• Geomechanics and Engineering
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• 제34권3호
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• pp.303-316
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• 2023

With the development and utilization of urban underground space, the artificial ground freezing technology has been widely used in the construction of underground engineering in soft soil areas. The mechanical properties of soft clay changed greatly after freezing and thawing, which affected the seismic performance of underground structures. In this paper, a series of triaxial tests were carried out to study the dynamic response of the freezing-thawing clay under the seismic load considering different dynamic stress amplitudes and different confining pressures. The reduction factor of dynamic shear stress was determined to correct the amplitude of the seismic load. The deformation development mode, the stress-strain relationship and the energy dissipation behavior of the soft clay under the seismic load were analyzed. An empirical model for predicting accumulative plastic strain was proposed and validated considering the loading times, the confining pressures and the dynamic stress amplitudes. The relevant research results can provide a theoretical reference to the seismic design of underground structures in soft clay areas.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.235-237
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• 1995

The demands of minimizing the reactive power and reducing. the current harmonics are increasing nowadays. The inverter airconditioner needs high power and it operates with wide load range. Conventionally, ah huge LC passive filter is used in airconditioner to improve the P.F and to reduce current harmonics which doesn't gives good results. In this paper, a design of active power factor correction(PFC) circuit for inverter air conditioner is described. To improve the P.F and to reduce the THD, an average current controlled active PFC is designed and tested. Experimental results show that the developed system achieves almost unity P.F and low THD for all load range.

• 항공우주시스템공학회지
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• 제9권4호
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• pp.55-61
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• 2015

In this study, we peformed optimal design of a composite skid landing gear, one of the solid spring shock absorbers, for light vertical takeoff and landing aircraft. Although a solid spring type has poor energy dissipation capability, it is commonly used for light aircraft where sink speeds are low and shock absorption is non-critical in terms of simplicity, low cost and weight reduction. In this paper, design parameters of solid spring such as sink speed, gear leg length, deflection and landing load factor were reviewed. In order to meet structural requirements such as deflection and strength, finally, we conducted optimal design of the composite skid landing gear for VTOL UAV using genetic algorithm and pattern search algorithm.

• 한국강구조학회 논문집
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• 제24권1호
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• pp.1-11
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• 2012

군중하중을 받는 현행 바닥진동 설계절차의 한계를 극복하기 위해서는 개인별 운동의 시간차와 운동성분에 내재된 위상의 불확실성이 고려되어야 한다. 개인의 운동에 관한 연구는 통계적 자료를 토대로 많은 연구가 진행되고 있는 반면, 군중 행동패턴에 관한 연구는 그 복잡성으로 인해 연구가 미흡한 실정이다. 본 연구에서는 다양하고 복잡한 군중의 행동패턴을 개인 간의 위상을 반영한 하중모형을 제안한다. 모의실험을 통해 개인의 시간지연 값들을 난수로 발생시킨 후, 기준시간에 대한 시간 지연효과를 합산하였다. 본 연구에서 제안하는 위상의 합산으로 이루어진 계수는, 완전히 동기화된 군중의 경우에 대한 동기화 정도의 비를 나타낼 수 있다. 정의된 계수를 바탕으로 실제 일어날 수 있는 군중의 행동패턴을 분석하여 각각의 경우에 대한 계수 값을 제안하였다. 본 연구의 결과를 토대로 기존의 설계방식이 다룰 수 없었던 군중의 운동시 바닥구조의 응답을 합리적으로 반영할 수 있다.

• Computers and Concrete
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• 제19권3호
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• pp.243-256
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• 2017

Epoxy-coated reinforcing bars are widely used to protect the corrosion of the reinforcing bars in the RC elements under their in-service environments and external loads. In most field surveys, it was reported that the corrosion resistance of the epoxy-coated reinforcing bars is typically better than the uncoated bars. However, from the experimental tests conducted in the labs, it was reported that, under the same loads, the RC elements with epoxy-coated reinforcing bars had wider cracks than the elements reinforced with the ordinary bars. Although this conclusion may be true considering the bond reduction of the reinforcing bar due to the epoxy coating, the maximum service loads used in the experimental research may be a main reason. To answer these two phenomena, service performance of 15 RC beam specimens with uncoated and epoxy-coated reinforcements under different fatigue loads was experimentally studied. Influences of different coating thicknesses of the reinforcing bars, the fatigue load range and load upper limit as well as fatigue load cycles on the mechanical performance of RC test specimens are discussed. It is concluded that, for the test specimens subjected to the comparatively lower load range and load upper limit, adverse effect on the service performance of test specimens with thicker epoxy-coated reinforcing bars is negligible. With the increments of the coating thickness and the in-service loading level, i.e., fatigue load range, load upper limit and fatigue cycles, the adverse factor resulting from the thicker coating becomes noticeable.