• 대한토목학회논문집
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• 제34권5호
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• pp.1435-1442
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• 2014

본 연구에서는 OpenFOAM에서 제공하는 소스코드를 이용하여 매끄러운 하상의 직사각형 개수로 흐름에 대해 수치모의를 수행하였다. 난류 해석을 위해 LES를 수행하였는데, 비등방성 잔여 응력항을 모델링하기 위해서 Germano et al. (1991)이 제시한 Dynamic Subgrid-scale 모형을 이용하였다. 조직구조를 분석하기 위하여 Lu and Willmarth (1973)가 제시한 uw 사분면기법을 이용하여 순간레이놀즈 응력이 레이놀즈 응력에 미치는 영향을 기여율과 시간비로 나누어 분석하였다. LES 모의 결과를 토대로 기존 실험 및 DNS 모의 결과와 비교하고 분석하였다. 매끈한 하상을 가진 개수로 흐름에서 완충층 이후의 구간에서 분출현상이 쓸기현상에 비해 레이놀즈 응력의 양의 생성에 기여하는 바가 크지만, 분출현상에 비해 쓸기현상의 발생빈도가 큰 것으로 확인되었다.

• Safety and Health at Work
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• 제7권3호
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• pp.218-224
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• 2016

Background: Butchering is often associated with high rates of work-related musculoskeletal disorders (WRMSDs). However, published work on the prevalence of WRMSDs among butchers in Nigeria is scarce. This is important because meat processing practices differ across geographical and cultural locations. This study was therefore aimed at analyzing WRMSDs among butchers in Kano metropolis. Methods: Sociodemographic and work-settings information was obtained from 102 male cattle butchers (age, $37.49{\pm}11.68years$) through survey. Information on the prevalence and pattern of musculoskeletal disorders was obtained from the respondents using the Standardized Nordic Questionnaire. Additional information on health seeking practices was also obtained using a pro forma. Associations between the prevalence of WRMSDs and each of the sociodemographic data and work settings were explored using Chi-square analysis. The level of significance was set at p < 0.05. Results: The 12-month and point prevalence rates of WRMSDs among butchers in this study were 88.2% and 74.5%, respectively. Whereas lower back complaints (66.7%) were the overall and lower body quadrant's most commonly reported WRMSDs among the butchers surveyed, wrist/hand complaints were the leading upper quadrant's (45.1%) most commonly reported WRMSDs among the respondents. There were significant associations between age and majority of WRMSDs in the body regions. Only 23.3% of the 90 individuals who had WRMSD visited the hospital to seek redress for their WRMSD. Conclusion: The prevalence of WRMSDs is high among butchers in Kano Metropolis. Few individuals with WRMSD utilize healthcare facilities. Age is a major risk factor in this setting.

• International Journal of Aeronautical and Space Sciences
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• 제10권2호
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• pp.117-124
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• 2009

In the environment where various and complicated threat signals exist, RWR (Radar Warning Receiver), which can warn pilot of the existence of threats, has long been a necessary electronic warfare (EW) system to improve survivability of aircraft. The angle of arrival (AOA) information, the most reliable sorting parameter in the RWR, is measured by means of four-quadrant amplitude comparison direction finding (DF) technique. Each of four antennas (usually spiral antenna) of DF unit covers one of four quadrant zones, with 90 degrees apart with nearby antenna. According to the location of antenna installed in helicopter, RWR is subject to signal loss and interference by helicopter body and structures including tail bumper, rotor blade, and so on, causing a difficulty of detecting hostile emitters. In this paper, the performance degradation caused by signal interference by tail rotor blades has been estimated by measuring amplitude video signals into which RWR converts RF signals in case a part of antenna is screened by real tail rotor blade in anechoic chamber. The results show that corruption of pulse amplitude (PA) is main cause of DF error. We have proposed two algorithms for resolving the interference by tail rotor blades as below: First, expand the AOA group range for pulse grouping at the first signal analysis phase. Second, merge each of pulse trains with the other, that signal parameter except PRI and AOA is similar, after the first signal analysis phase. The presented method makes it possible to use RWR by reducing interference caused by blade screening in case antenna is screened by tail rotor blades.

• 농촌계획
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• 제6권2호
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• pp.82-93
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• 2000

The concept of sustainable development in rural area, which is focused on both preservation of nature and human's amenity, has been common paradigm. The purpose of this study is to suggest the development directions for the environmentally friendly rural house. The planning items for developing sustainable rural house were selected through literature survey, case study, and their adaptation evaluation. The establishment of principles and the evaluation of planning items were analyzed by a survey to experts. The results are as follows : 1) It is showed that sustainability evaluation of rural village is rated as above the moderate degree, but rural house is rated as 3.4(average score). Especially, there were lowly evaluated the utility, material, structure and inner environment in rural house. 2) It is revealed that 76.7% of planning items are located in both the upper left and upper right hand quadrant of the action grid, which is drawn by the importance-performance analysis(IPA). And any item is not found in the lower right hand quadrant(Possible Overkill). 3) Two basic principles and eight optional principles we identified by analysis of factor and regression. The rural zone is identified as major effective element for applying planning items into the rural house development. So it is desirable to apply the items differently by the rural zone type. 4) In view of sustainable development, it is desirable for rural village to have about 50 houses, and for rural house to have $155{\sim}180$ pyung(坪) as lot size, 30% as ratio of building, and 60% as building volume.

• 대한토목학회논문집
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• 제26권2B호
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• pp.139-144
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• 2006

측벽이 존재하는 개수로 난류흐름에 대한 DNS 자료를 사용하여 레이놀즈 전단응력 및 이차흐름의 생성메커니즘을 규명하였다. 측벽 부근에서 이차흐름의 양상을 보면, 상부 및 하부 모서리 부근에서는 측벽을 향해 침투되는 이차흐름이 형성된 반면, 그 외의 영역에서는 수로 중앙을 향해 분출하는 이차흐름이 형성된 것으로 나타났다. 측벽 부근에서 레이놀즈 전단응력의 분포를 산정하였으며, 고유구조와 연계하여 분석하였다. 사분면 해석에서 측벽을 향해 침투되는 이차흐름이 생성된 영역에서는 쓸기현상이 지배적인 반면, 측벽으로부터 분출되는 이차흐름이 형성된 영역에서는 분출현상이 지배적인 것으로 나타났다. 또한 조건부 사분면 해석을 통해 레이놀즈 전단응력의 생성 및 이차흐름의 양상이 지배적인 고유구조의 방향성에 의해 결정된다는 것을 확인하였다.

• 한국조경학회지
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• 제47권4호
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• pp.68-80
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• 2019

본 연구는 중학교 명상숲의 물리적 환경특성과 이용자들의 이용행태 및 중요도-만족도 등을 분석하여 향후 중학교 명상숲 조성에서 이용자 중심의 설계를 수행하기 위한 기초자료를 제공하는 것에 목적이 있다. 이를 위해 명상숲 대상지의 부지특성, 자연성 기능성, 효과성을 바탕으로 중요도-만족도 분석을 위한 평가지표 24항목을 선정하였다. 광주광역시의 중정형 A, B 중학교 두 곳에서 대상지 현황조사분석과 학생, 교사를 대상으로 설문조사 및 분석을 실시하였다. 연구결과, 첫째 명상숲에 대한 인식과 이용정도는, 두 학교 모두에서 학생의 명상숲 인식정도와 이용률이 교사에 비해 매우 낮게 나타났다. 학교 간 집단비교 결과는 A학교가 B학교에 비해 이용 및 인식정도가 매우 양호하였다. 둘째, 명상숲 이용행태는 휴식(49.6%), 주중 점심시간(63.6%), 친구(65.0%) 또는 동료(60%)와 함께 10분 이하(68.6%)로 이용하는 것으로 나타났다. 꽃이 피는 식물(30.0%)과 녹음수(28.9%)를 좋아하며, 주로 쉼터(57.9%)와 산책로(37.1%)를 이용하였다. 셋째, 중요도, 만족도 분석결과, 전체 24개 항목에 대한 평균은 중요도(3.81)가 만족도(3.62)보다 높았다. I사분면(지속적 유지)의 항목들은 9개, II사분면(우선적 시정)의 항목들은 3개, III사분면(관리운영 시 저우선순위)의 항목들은 7개, IV사분면(과잉노력의 지양)의 항목들은 5개이다. 두 학교 간 만족도에서 통계적으로 유의미한 차이를 보인 16개 항목에 대해서 A학교 만족도가 B학교보다 모두 높게 나타났다. 이는 A학교 명상숲에 규모가 더 큰 숲과 산책로가 확보되어 있고, 접근성이 더 용이하며, 다양한 식재유형 및 식재면적이 제공되고 있어 B학교에 비해 만족도가 더 높은 것으로 판단된다. 넷째, 전반적 만족도 분석결과에서 A학교(68.0%)와 B학교(47.2%) 간 유의한 차이를 보였으며, 이는 A학교의 주요 만족공간인 산책로와 쉼터가 B학교보다 더 잘 조성되어 있어 만족도의 차이가 큰 것으로 판단된다. 전체를 대상으로 한 가장 만족하는 공간의 순위로 산책로(1위), 쉼터(2위)가 선정되었고, 만족하는 이유는 A와 B학교 모두 휴식(스트레스 해소 및 정서함양)이 가장 높게 나타났다.

• 한국철도학회논문집
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• 제2권1호
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• pp.38-46
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• 1999

This study proposes the analysis and evaluation method of time series ultrasonic signal using the attractor analysis. Features extracted from time series signal analyze quantitatively characteristics of weld defects. For this purpose, analysis objective in this study is fractal dimension and attractor quadrant feature. Trajectory changes in the attractor indicated a substantial difference in fractal characteristics resulting from distance shifts such as parts of head and flange even though the types of defects are identified. These differences in characteristics of weld defects enables the evaluation of unique characteristics of defects in the weld zone. In quantitative fractal feature extraction, feature values of 3.848 in the case of part of head(crack) and 4.102 in the case of part of web(side hole) and 3.711 in the case of part of flange(crack) were proposed on the basis of fractal dimensions. Proposed attractor feature extraction in this study can enhance the precision rate of ultrasonic evaluation for defect signals of rail weld zone such as side hole and crack.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.664-667
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• 1997

In this study, it is attempted to obtain the optimized size of holes in 15 square plate models where a hole exists on every quadrant of a plate, and to get eigenvalues and mode shapes by performing free vibration analysis for each model. For free vibration analysis and optimization of' hole sizes, the uniaxial tension is applied for the loading condition. From the results of this study, it is known that more stable structures can be designed by changing the natural frequency depending on the location and the optuiiunl size of holes. and further studies are considered to be necessary for the basic design information.

• Journal of Welding and Joining
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• 제18권5호
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• pp.77-83
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• 2000

This study proposes the analysis and evaluation method of time series ultrasonic signal using the attractor analysis. Features extracted from time series signal analyze quantitatively characteristics of weld defects. For this purpose, analysis objective in this study is fractal dimension and attractor quadrant feature. Trajectory changes in the attractor indicated a substantial difference in fractal characteristics resulting from distance shifts such as parts of head and flange even though the types of defects are identified. These difference in characteristics of weld defects enables the evaluation of unique characteristics of defects in the weld zone. In quantitative fractal feature extraction, feature values of 3.848 in the case of part of head(crack) and 4.102 in the case of part of web(side hole) and 3.711 in the case of part of flange(crack) were proposed on the basis of fractal dimensions. Proposed attractor analysis and DAC in this study can enhance the precision rate of ultrasonic evaluation for defect signals of rail weld zone such as side hole and crack.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.87-95
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• 1998

This study proposes the analysis and evaluation method of time series ultrasonic signal using the attractor analysis. Features extracted from time series signal analyze quantitatively characteristics of welding defects. For this purpose, analysis objective in this study is fractal dimension and attractor Quadrant feature. Trajectory changes in the attractor indicated that even the same type of defects carried substantial difference in fractal characteristics resulting from distance shifts such as parts of head and flange. Such differences in characteristics of weld defects enables the evaluation of unique features of defects in the weld zone. In quantitative fractal feature extraction, feature values of 3.848 in the case of part of head(crack) and 4.102 in the case of part of web(side hale) and 3.711 in the case of part of flange(crack) were proposed on the basis of fractal dimensions. Proposed attractor feature extraction in this study can enhance the precision rate of ultrasonic evalaution for defect signals of rail weld zone such as side hole and crack.