• 전기학회논문지
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• 제59권2호
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• pp.242-247
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• 2010

This paper introduces a real-time load flow program for Korean energy management system(EMS). This study is concentrated on the following aspects. First, we propose the model of the real-time database and power system equipment for the real-time load flow. These models are extracted from the needs of load flow functions and are designed to the application common information. Second, several techniques are applied for the efficient convergence and computational speed. The generation/load mismatch is redistributed using generator participation factors which are separated to the reference bus. For the voltage control, the jacobian matrix is composed with the basic Y matrix elements and the voltage control elements. Through the optimally ordering, jacobian row and column for a column is changed. However all jacobian matrix entries have same order with the Y matrix. The proposed program is tested using the Korea Electric Power Corporation(KEPCO) system. Through the test, we verified that the proposed program can be effectively used to accomplish the Korean EMS system.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.406-414
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• 2014

Significant penetration of induction motor loads into residential neighborhood and commercial regions of local transmission systems at least partially determine a vulnerability to a fault induced delayed voltage recovery (FIDVR) event. Highly concentrated induction motor loads with constant torque could stall in response to low voltages associated with system faults. FIDVR is caused by wide spread stalling of small HVAC units (residential air conditioner) during transmission level faults. An under voltage load shedding scheme (UVLS) can be an effective component in a strategy to manage FIDVR risk and limit the any potential disturbance. Under Voltage Load Shedding take advantage of the plan to recovery the voltage of the system by shedding the load ways to alleviation FIDVR.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1702-1704
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• 2005

In solar power system, the height and azimuth of the sun are important parameters which control generated power magnitude. The way that controls the daily generation magnitude according to latitude and longitude and uses two axles is often used in the existing sunlight racing system now. In this two-axle sunlight track control system the self-load is concentrated on one FRAME. It is influenced of the regular load, snow load and the wind load, etc. It is difficult to set up the system in the building already built up. This research is a development about the small-scale economy track device of independent load-dispersing type solar generation system. The position track algorithm is through calculating the trail of height and azimuthal of the sun calculation to follow the sun.

• 해양환경안전학회지
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• 제16권1호
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• pp.125-133
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• 2010

기존의 해상교량 기둥의 외부보강에 따른 연구들은 현재까지 주로 중앙점 재하에 따른 성능을 평가하였다. 하지만, 장대교량의 기둥은 정확한 중심축을 기준으로 축하중을 받는 경우와 편심으로 인한 큰 모멘트가 동시에 작용하는 경우가 많이 발생한다. 이 연구에서는 해상장대교량의 고강도 철근콘크리트 기둥의 하중재하 위치와 2가지의 보강 재료인 탄소섬유 및 고성능 유리섬유를 각각 보강하여 그 효과를 분석하였다. 실험에 사용된 12개의 기둥 실험체는 모두 같은 크기로 제작 및 실험을 하였다. 그 중 6개 실험체의 횡보강 철끈은 띠철근으로 배근하였으며, 그 외 6개의 실험체는 나선철근으로 매끈하였다. 그리고 각각 3겹의 탄소섬유 및 고성능 유리섬유를 적용하여 감싸기 방법으로 보강하였다. 실험변수는 하중재하 위치에 따른 철근의 보강행태 및 보강재료가 고려되었다. 실험결과, 편심축에 따른 하중재하 기둥부재는 중심축 하중재하에 비해 최대 파괴하중이 감소하였지만 고성능 유리섬유를 보강한 기둥부재는 축하중 및 편심하중에서 탄소섬유를 보강한 경우보다 내력과 연성이 우수하였다.

• 한국소음진동공학회논문집
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• 제21권8호
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• pp.698-707
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• 2011

이 연구는 유한요소법을 이용하여 집중질량을 갖고 비균질한 지반에 놓은 변단변 후판 구조물에 대한 동적 안정해석이다. 해석을 위하여 유한요소법을 이용하여 해당구조물의 고유진동수와 좌굴하중을 구하여 기존해와 비교하여 프로그램을 검증하였다. 비균질 Pasternak 지반에 놓인 변단면으로 집중질량을 갖는후판의 동적안정 해석을 통하여 판의 불안정 영역이 결정된다. 무차원 Winkler 지반강성은 100, 1000을 적용하였고, 무차원 전단지반강성은 5로 하였다. 그리고 변단면율은 0.25, 1.0, 집중질량비는 0.25, 1.0 그리고 면내응력은 $0.4{\sigma}_{cr}$을 적용하여 해석하였다.

• 한국물환경학회지
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• 제29권5호
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• pp.656-665
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• 2013

This research was conducted to investigate pollutant load unit factor from aquacultural farms. Pollutant load unit factors were investigated on the 13 kinds of fish type, i.e., Trout, Leather Carp, Eel, Carp, Cartfish, Freshwater Eel, Crucian Carp, Colored Carp, Sturgeon, Marsh Snail, Sweetfish, Pond Snail, Eriocheir Sinensis. Water qualities in aquacultural farms were investigated wide range of values by fish type and pollutant items. High BOD and COD values were observed at the Leather Carp (Ponded water system), Cartfish (Ponded water system) and Freshwater Eel (Recirculating System). TOC and DOC values were relatively high at the Freshwater Eel (Recirculating System) and Eriocheir Sinensis (Extensive). Eel (Ponded water system) and Freshwater Eel (Recirculating System) produced high concentrated nutrient pollutants, i.e., T-N, T-P. Pollutant load unit factors are dependent on fish type, aquacultural type, water quality items, etc. If some fishes have similar basic unit values, those could be applied for TMDLs as a group of fish having same pollutant load unit. The water quality concentrations of post treatment facilities' (mainly reservoir tank) effluent were higher than those of fish raising bath because of extracting pollutant from sediment in the reservoir tank. Therefore, it needs to the management and regulations about post treatment facilities.

• 농업과학연구
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• 제47권2호
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• pp.327-335
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• 2020

The purpose of this study was to analyze the load distribution and contact safety factor for the power take off (PTO) gear of a 71 kW class agricultural tractor. In this study, a simulation model of the PTO gear-train was developed using Romax DESGINER. The face load factor and contact safety factor were calculated using ISO 6336:2006. The simulation time was set at 2,736 hours considering the lifetime of the tractor, and the simulation was performed for each PTO gear stage at the engine rated power conditions. As a result of the simulation, the face load factors for the driving gear at the PTO 1^st, 2^nd and 3^rd stages were 1.644, 1.632, and 1.341, respectively. The contact safety factors for the driving gear at the PTO 1^st, 2^nd and 3^rd stages were 1.185, 1.216, and 1.458, respectively. As the PTO gear stage was increased, the face load factor decreased, and the contact safety factor increased. The load distributions for all the PTO gears were concentrated to the right of the tooth width. This causes stress concentrations and shortens the lifespan of the gears. Therefore, it is necessary to improve the face load factor and the contact safety factor with macro-geometry and micro-geometry.

• 한국철도학회논문집
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• 제8권4호
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• pp.367-371
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• 2005

Pile foundations are utilized when soil is so weak that shallow foundations are not suitable or point load is concentrated in small area. Such soil can be formed by the land reclamation works which have extensively been executed along the coastal line of southern and western parts of the Korean Peninsula. The working load at pile is sometimes subjected to not only compression load but also lateral load sad uplift forces. But in most of the practice design, uplift capacity of pile foundation is not considered and estimation of uplift capacity is presumed on the compression skin friction. This study was carried out to determine that the effect of embedment ratio and loading rate on uplift adhesion factor of concrete pile driven in clay. Based on the test results, the critical embedment ratio is about 9. Adhesion factor is constant under the critical embedment ratio, and decreasing over the critical embedment ratio. Also, adhesion factor is increased with the loading rate is increased.

• Steel and Composite Structures
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• 제34권5호
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• pp.769-782
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• 2020

A Prestressed stayed steel column is an efficient and lightweight way with regard to enhancing the stability behaviour of a compression column. In the past, researchers primarily concentrated on investigating the behaviour of stayed steel columns with horizontal crossarms. However, this article focuses on prestressed stayed steel columns with split-up crossarm system, in which the crossarms are aslant and rotational symmetrically arranged. A mathematical formula calculating the optimal pretension that corresponds to the maximum critical buckling load was established according to geometric analysis based on the small deformation assumption. It was demonstrated that critical buckling mode of this stayed column is different from the one with horizontal crossarms. The governing imperfection direction that should be adopted in the nonlinear buckling analysis was determined in this work. In addition, the effects of crossarm inclination, stay diameter, and crossarm length on the stability behaviour were investigated. An influencing factor denotes the ratio of the load carrying capacity of the prestressed stayed steel column to the Euler load of the main column was also obtained.

• Advances in Computational Design
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• 제5권4호
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• pp.397-416
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• 2020

Functionally graded material (FGM) illustrates a novel class of composites that consists of a graded pattern of material composition. FGM is engineered to have a continuously varying spatial composition profile. Current work focused on buckling analysis of beam made of stepwise linear and quadratic graded material in axial direction subjected to axial span-load with piecewise function and rested on shear layer based on classical beam theory. The various boundary and natural conditions including simply supported (S-S), pinned - clamped (P-C), axial hinge - pinned (AH-P), axial hinge - clamped (AH-C), pinned - shear hinge (P-SHH), pinned - shear force released (P-SHR), axial hinge - shear force released (AH-SHR) and axial hinge - shear hinge (AH-SHH) are considered. To the best of the author's knowledge, buckling behavior of this kind of Euler-Bernoulli beams has not been studied yet. The equilibrium differential equation is derived by minimizing total potential energy via variational calculus and solved analytically. The boundary conditions, natural conditions and deformation continuity at concentrated load insertion point are expressed in matrix form and nontrivial solution is employed to calculate first buckling loads and corresponding mode shapes. By increasing truncation order, the relative error reduction and convergence of solution are observed. Fast convergence and good compatibility with various conditions are advantages of the proposed method. A MATLAB code is provided in appendix to employ the numerical procedure based on proposed method.