• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2017년도 학술발표회
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• pp.329-329
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• 2017

In this study attempted to evaluate the stability of the protection methods by examining hydraulic characteristics of the area around the point in which marine cable protector is installed such as surf zone occurrence point of shore-end submarine cables suitable for coastal marine environmental conditions, flow rate t the tope of the protector and maximum wave height, and to provide basic data for the selection of the optimal protection method. In performing hydraulic model experiments, the topography of submarine cable installation location was reproduced in 2-D sectional channel, and models appropriate for experimental scale and similitude law were produced and installed for each condition of submarine cables and protectors. Since the topography and submarine cable protectors were reproduced and installed in 2-D sectional channel, the exact reproduction of surf and transformation in shallow water zone was possible, and thus the physical properties could be clearly analyzed. For stability review, an experiment to examine the stability was conducted using a wave maker with 50-year frequency design waves as target, and wave height and cycles were applied based on the approximate lowest low water level(Approx. L.L.W), which is the most dangerous in submarine cable protection methods. As for experimental time, typhoon passing time in summer (about 3 hours) was applied, and wave patterns and deviation ratio of the submarine cable protector were investigated after making irregular waves corresponding to design waves. In addition, current meter and wave height meter were installed at the installation location of the submarine cable protector, and the flow rates and wave height at the top of the protector were measured and analyzed to review hydraulic properties.

• 한국환경보건학회지
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• 제41권5호
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• pp.277-288
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• 2015

Objectives: There are many hazardous agents at livestock farms. In particular, gases can be detrimental to both workers and animals. This study evaluated ammonia and hydrogen sulfide concentrations in broiler hen barns and beef cattle barns according to sampling location and height. Methods: Three broiler hen barns and three beef cattle barns were selected for gas monitoring in this study. Ammonia and hydrogen sulfide concentrations were measured using a direct-reading instrument which could measure the target gases simultaneously. Gas monitoring was conducted at human breathing height and animal breathing height at three points in each livestock farm. Results: Ammonia concentrations at the broiler hen barns ranged from 3.3 to 12.5 ppm by sampling location and height, but hydrogen sulfide was not detected. In the beef cattle barns, ammonia ranged from 3.1 to 16.3 ppm and low concentrations of hydrogen sulfide were detected at some animal breathing heights. The gas concentrations detected at each livestock farm were significantly higher in the animal breathing zones than in human breathing zones (p<0.0001). Conclusions: We found a difference in gas concentrations between human breathing zones and animal breathing zones. Gas monitoring should be conducted to improve the related environment considering both workers' and animals' health and safety.

• Industrial Engineering and Management Systems
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• 제3권2호
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• pp.129-133
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• 2004

Studies on the optimal location of retail store have been made in case of no obstacle(Minagawa etal. 1999). This paper deals with the location problem of retail store considering obstacles (e.g. rivers, railways, highways, etc.) and obstacle-overcoming points (e.g. bridges, railway crossings, zebra crossings, overpasses, etc.). We assume that (1) commercial goods dealt here are typically convenience goods, (2) the population is granted as potential demand, (3) the apparent demand is a function of the maximum migration length and the distance from the store to customers, (4) the scale of a store is same in every place and (5) there is no competitor. First, we construct the basic model of customers' behavior considering obstacles and obstacle-overcoming points. Analyzing the two dimensional model, the arbitrary force attracting customers is represented as a height of a cone where the retail store is located on the center. Second, we formulate the total demand of customers and determine the optimal location that maximizes the total demand. Finally, the properties of the optimal location are investigated by simulation.

• Steel and Composite Structures
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• 제50권1호
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• pp.1-13
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• 2024

The objective of this research is to study experimentally and numerically the behavior of steel beam columns with openings. Although the presence of openings in the beam columns is inevitable, finding ways to maintain strength is crucial. The studied parameters are opening shape, the ratio between opening height to specimen height, the percentage of opening location from support to beam column length, and web slenderness. Experimental tests are conducted including twelve specimens to study the effect of these parameters and record failure load, load deflection curve, and stress strain curve. Two failure modes are observed: local and flexural buckling. Interaction curves plotted from finite element model analysis are also used to expand the parametric study. Changing the location of the opening can decrease failure load by up to 7% and 60% in both normal and moment ratios respectively. Increasing the opening dimension can lead to a drop in the axial ratio by up to 29% and in the moment ratio by up to 74%. The weakest beam column behavior is noticed in specimens with rectangular openings which results from uneven and concentrated stresses around the opening. The main results of this research illustrate that the best location for opening is at 40% - 50% from beam column support. Also, it is advisable to use circular openings instead of rectangular openings in specimens having slender webs because moment ratios are raised by 85% accompanied by a rise in normal ratios by 9%.

• 대한환경공학회지
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• 제33권5호
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• pp.340-352
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• 2011

본 연구에서는 미기상 수치 모델 ENVI-MET3.0을 이용하여 고층 건물 입지에 따른 바람장과 기온 변화를 분석하였다. 대상지역은 고층 아파트 단지가 계획되어 있는 전주시 도심지이며, 실제 설계 자료를 적용하였다. 건물 입지에 따른 미기상 변화를 분석하기 위해 건물 입지전과 후에 대해 모델링을 수행한 후, 그 변화량을 분석하였다. 모델링 수행시 기상 조건은 연구대상 지역의 기후분석을 통해 두 가지를 선정하였는데, 첫 번째 조건은 풍향을 남남동(SSE)풍, 두 번째 조건은 풍향을서(W)풍 계열로 하였다. 바람길 분석은 풍속, 열섬 분석은 기온 변화량을 통해 분석을 실시하였다. 풍속 분석 결과, 건물 높이보다 낮은 고도에서는 바람이 유입되는 지역에서는 0.2~2.5 m/s 정도 증가한 반면, 건물 사이에서는 0.5~2.0 m/s 정도 감소하였다. 건물 높이 이상의 고도에서는 건물이 위치한 단지 내에서는 0.1~0.8 m/s m/s 정도 감소하는 반면, 단지 외부에서는 0.2~0.4 m/s 정도 증가하였다. 열섬 분석 결과, 건물 높이보다 낮은 고도에서는 건물이 위치한 단지 내와 풍하방향 지역에서는 기온이 $0.01{\sim}0.1^{\circ}C$ 증가한 반면, 단지 외부에서는 $0.01{\sim}0.05^{\circ}C$ 감소하였다. 건물 최고 높이 부근에서는 대부분의 지역에서 $0.05{\sim}0.2^{\circ}C$ 정도 감소하였다.

• 한국산학기술학회논문지
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• 제17권7호
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• pp.726-733
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• 2016

본 연구에서는 기존 데이터센터 서버실에서 공기분배시스템으로 파티션 시스템의 적용성을 평가하기 위해 기존 시스템 그리고 파티션의 설치 높이와 위치를 변수로 하는 파티션 시스템과 컨테인먼트 시스템에 대해 총 21가지 경우의 컴퓨터시뮬레이션을 실시하고 다음과 같은 결론을 얻었다. 공기온도 및 기류 분포 해석결과를 이용하여 평가해 본 공기분배시스템별 냉방 에너지 절감 성능은 컨테인먼트 시스템, 파티션 시스템, 기존 시스템 순서로 우수한 것을 확인할 수 있었다. 기존 시스템과 파티션 설치높이 0.1~0.7m까지의 파티션 시스템은 재순환 공기에 의해 냉복도에서 1.0~1.2m 높이를 기점으로 공기 온도가 급격히 상승하면서 중간 높이의 서버와 상부 서버의 인입구 온도차는 $11{\sim}15^{\circ}C$로 큰 차이를 보여, 재순환 공기가 상부 서버의 과열의 원인을 제공하는 것으로 나타났다. 파티션 시스템에서 냉복도 상부에 파티션을 설치할 경우에 파티션의 적정 높이는 서버 랙 상부에서 천장까지 높이의 90%(0.9m)이상, 열복도 상부에 파티션을 설치하는 경우는 파티션 높이가 80%(0.8m)이상은 되어야 재순환 공기를 충분히 차단하여 서버 인입구 공기온도가 RCI 권장온도 범위를 만족하는 냉방 에너지 절감효과를 볼 수 있는 것으로 나타났다.

• 생태와환경
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• 제49권3호
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• pp.236-243
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• 2016

본 논문은 국립공원 아고산대 침엽수림을 효과적으로 보전하고 관리하는 데 기초자료로 활용하고자 진행된 사례연구로서 지리산국립공원과 속리산국립공원의 아고산대에서 현지 조사된 구상나무 (Abies koreana Wilson) 210개체의 서식실태 자료를 바탕으로, 입지환경의 기본이 되는 지리적 위치와 지형적 특성이 구상나무의 생장에 미치는 영향을 분석하였다. 이를 위해서 구상나무의 생장과 관련된 변수는 수고 및 흉고직경으로 하고, 지형적 특성은 GIS 공간분석을 이용하여 추출된 지리적 위도, 해발고도, 산지경사, 사면향 그리고 지형습윤지수로 하였다. 두 변수군의 연관성의 유무와 정도를 평가하기 위해서 정준상관분석을 이용하고, 다중회귀분석을 이용하여 지리 지형적 특성이 구상나무의 생장구조에 미치는 영향을 평가하였다. 구상나무 생장구조를 나타내는 흉고직경 및 수고는 지형의 수직적인 분포보다 지리 위도적인 분포와 연관성이 더 크고, 지리 지형요소는 수고보다 흉고직경과 연관성이 더 큰 것으로 나타났다. 구상나무의 생장구조변수와 지리 지형변수는 유의한 상관관계가 있고, 지리 지형변수가 생장구조변수를 18.1% 정도 설명하는 것으로 나타났다. 구상나무의 흉고직경에 영향을 주는 변수는 지리적 위도, 지형습윤지수, 사면향 그리고 해발고도의 순으로 통계적 유의성이 있는 것으로 나타났다. 위도가 높아질수록 흉고직경은 작아지고 지형적 요소에 따라서는 커지는 것으로 나타났다. 수고에 영향을 주는 변수는 지형습윤지수만이 유의미한 것으로 나타났다. 전반적으로, 구상나무의 생장구조와 관련된 수고와 흉고직경은 지리적인 특성의 영향이 가장 클 것으로 나타났다. 특히 지형적 특성 중에서 수분상태의 영향이 다른 지형요소에 비해서 더 클 것으로 예측되었다. 이러한 결과로 볼 때, 지리 지형적인 특성은 구상나무의 생장에 중요한 요인이 될 것으로 추측된다. 비록 지리 지형적 특성만을 고려하고 GIS를 이용하여 제작된 공간분석 자료를 사용한 한계가 있다고 해도, 본 연구결과는 향후 국립공원 아고산대에서 서식하고 있는 침엽수림의 생장환경을 조사하고 연구하는 데 유용하고, 구상나무 등 상록침엽교목을 효과적으로 관리하고 보전하기 위해서 대책을 수립하는 데 기초자료로 활용될 것으로 기대된다.

• 한국산림과학회지
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• 제99권2호
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• pp.204-212
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• 2010

This study was performed in 22 unthinned Larix olgensis plantations in northeast China. Data were collected on 95 sample trees of different canopy positions and the diameter at breast height ($d_{1.3}$) ranged from 5.7 cm to 40.2 cm. The individual tree models for the prediction of vertical distribution of live crown, branch and needle biomass were built. Our study showed that the crown, branch and needle biomass distributions were most in the location of 60% crown length. These results were also parallel to previous crown studies. The cumulative relative biomass of live crown, branch and needle were fitted by the sigmoid shape curve and the fitting results were quite well. Meanwhile, we developed the crown ratio and width models. Tree height was the most important predictor for crown ratio model. A negative competition factor, ccf and bas which reflected the effect of suppression on a tree, reduced the crown ratio estimates. The height-diameter ratio was a significant predictor. The higher the height-diameter ratio, the higher crown ratio is. Diameter at breast height is the strongest predictor in crown width model. The models can be used for the planning of harvesting operations, for the selection of feasible harvesting methods, and for the estimation of nutrient removals of different harvesting practices.

• Tribology and Lubricants
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• 제38권6호
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• pp.281-286
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• 2022

In this study, the effects of Elasto-hydrodynamic lubrication pressure on the critical shoulder height of raceway in an angular contact ball bearing were investigated. Both 3D contact analyses using an influence function and the EHL analysis were conducted for the contact geometry between the ball and raceways. The pressure distributions by 3D contact analysis and EHL analysis for an example bearing were compared. The effect of ellipse truncation on the minimum film thickness also investigated from EHL analysis. The critical shoulder height in the dry contact and the EHL state were compared for various applied loads. It is shown that when the ellipse truncation occurs, the pressure spike for the EHL conjunction is higher than that for the dry contact, and its location moves more inward of the contact center. The steep pressure gradients would increase the flow rate, so in order to maintain flow continuity a significant reduction in film thickness and an abrupt rise in pressure occurs in the edge of shoulder. Significant reduction of the minimum film thickness occurs near the edge of shoulder. The critical shoulder heights in the EHL state are calculated as higher values compared with in the dry contact. This results shows that the determination of critical shoulder height by the EHL analysis is more proper.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2670-2680
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• 1996

Effeccs of porous wind fence on surface-pressure around 2-dimensional prism model of triangular cross-section were investigated experimentally. The pressure data were obtained at a Reynolds number based on the model height of Re=2.1*10$^{5}$ . Flow visualization also carried out to investigate the flow structure qualitatively. The mean velocity and turbulent intensity profiles measured at fence location were well fitted to the neutral atmospheric surface boundary layer over the open terrain. Various fences with different porosity and height were tested to investigate their effects on the surface pressure acting on a prism model at different locations. As the results, porous fence with porosity 40 ~ 50% is most effective for abating wind erosion. With decreasing porosity of the fence, pressure fluctuations on the model surface are increased. The mean pressure coefficients are decreased only when the fence height is greater than the model height. The effect of distance between wind fence and triangular prism was not significant, compared to that of the fence porosity and height.