• 한국지진공학회논문집
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• 제20권1호
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• pp.33-43
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• 2016

This study investigates the performance of hollow precast segmental bridge columns with reinforcement details for material quantity reduction. The proposed triangular reinforcement details are economically feasible and rational, and facilitate shorter construction periods. The precast segmental bridge columns provides an alternative to current cast-in-place systems. We tested a model of hollow precast segmental bridge columns under a constant axial load and a quasi-static, cyclically reversed horizontal load. We used a computer program, Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST), for analysis of reinforced concrete structures. The used numerical method gives a realistic prediction of performance throughout the loading cycles for hollow precast segmental bridge column specimens investigated. As a result, proposed reinforcement details for material quantity reduction was equal to existing reinforcement details in terms of required performance.

• Journal of Biosystems Engineering
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• 제17권3호
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• pp.260-271
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• 1992

Fruits are generally subjected to mechanical forces during harvesting, handling, and transportation that may cause damage in the form of bruises, punctures, and cracks. In order to prevent damage, and insure better quality fruits for consumers, it is very essential to study physical properties of these materials. The studies were conducted to examine the effect of storage period, storage condition, and other factors, such as loading rate and initial strain, on the stress relaxation behavior of the fruit flesh, and develop nonlinear viscoelastic models to represent its stress relaxation behavior. The following results were obtained from the study : 1. Since the viscoelastic behavior of the fruits flesh was nonlinear, the behavior was satisfactorily modelled as follows ; $${\delta}({\varepsilon},\;t)={\varepsilon}^A[B\;{\exp}(-Ct)+D\;{\exp}(-Ft)+G(-Ht)]$$ But, for the every strain applied, the stress relaxation behavior of the fruit flesh, such as apple and pear, could be well described by the Generalized Maxwell model, respectively. 2. The effect of loading rate on the stress relaxation behavior was remarkable. The higher loading rate resulted in the higher initial stress, and the faster stress relaxation. 3. The higher initial strain resulted in the higher initial stress, and stress relaxed at the large initial strain was also much higher than at the small initial strain. 4. Stress relaxation rate and quantity stored in the fruits at the low temperature storage were much higher than those at the normal temperature storage in the same storage period. Also, in all fruits tested, the longer storage period was the more relaxation rate and quantity were shown. These trends in the normal temperature condition was the more significant than in the low temperature condition.

• 생태와환경
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• 제34권1호통권93호
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• pp.62-69
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• 2001

본 연구는 삽교호 유입지천(곡교천, 무한천, 삽교천, 남원천)에서 강우시 유량 및 수질 관측을 1999년 6월부터 11월까지 실시하여 분석한 것이다. 연구의 최종 목적은 삽교호 수질을 개선시키는 것이며, 그 일환으로 삽교호 유입지천의 오염부하를 저감시키기 위해 강우시 유입되는 비점오염물질의 유출 특성 및 오염부하량을 산정하는데 본 연구의 목적이 있다. 조사 결과, 평상시 삽교호 수량에 가장 많은 영향을 미치는 유입지천은 삽교천이며, 강우시에는 유역면적이 가장 넓은 곡교천이 삽교호 수량에 가장 큰 영향을 미쳤다. 유역의 토지이용형태에 따른 유출 특성에 현격한 차이를 보여 수질 관리를 위한 대책 수립시 고려되어야 할 인자로 도출되었다. 삽교호로 유입되는 연간 총오염부하량 중 강우시 발생되는 비점오염부하량의 기여율은 SS, BOD, T-N 및 T-P 각각 62%, 43%, 41% 및 27%으로 추정되어 삽교호 수질을 개선하는데 유입부하를 감소시키기 위한 관리기법을 도입할 때 점오염원과 비점오염원에 대한 부하량 저감대책을 함께 수립해야 할 것으로 판단된다.

• 환경영향평가
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• 제9권4호
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• pp.291-300
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• 2000

Juam lake is a major water reservoir for the industrial and agricultural activities as well as the residental life of Kwangju and Chonnam regions. However, the water quality of the lake is getting worse due to a large quantity inflowing to the lake. The excessive growth of algae by the overfertilization may result in water treatment problems and also the interference with desirable water uses of navigation, aesthetics, recreation, and aquatic ecosystem. Thus the purpose of this study is to investigate the species and their amount of planktons in the lake and the relationship between the P loading amount and the chlorophyll-a used as a primary productivity index. The results of the investigation show that (1) the predominant species of algae are Microcystis aeruginosa, Anabaena affinis, Melosira granulata, Synedra acus, and Coelastrum cambricum, (2) the trophic state of the lake can be classified as eutrophic, and (3) there is close relation between the P loading amount and the chlorophyll-a.

• 대한안전경영과학회지
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• 제12권4호
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• pp.273-278
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• 2010

As basic study on effects of the decasualization of port labor, this paper watched labor supply framework reorganization, focused on port worker in Incheon port at before decasualization(2005~2007.9) and after decasualization(2007.10~2010.5) and analyzed disposal quantity, workers, workdays, productivity, accident and disaster data that was apt to influence by the decasualization of port labor. Though commercial traffic of Incheon port was decreased in global economic depression, individual workday per month after decasualization compared with before decasualization is decreased by 3.3days from 22.7day to 19.4days, on the other hand, indivisual annual loading and unloading throughput is increased averagely 71.6%, and labour productivity, when 2005 labour productivity are 100, are increased by 67%. After decasualization, overall loading and unloading productivity is improved. But, according to loading and unloading, the number of accident and disaster are increase by 11.7% after decasualization for loading and unloading operation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.25-30
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• 2002

To reduce the vibration of a gear driving system, the modification of gear tooth from the orignal involute gear profile is usually done in gear manufacturers. The quantity of tooth modification has been decided on the basis of the interference between two gear teeth during gear meshing and the elastic deformation due to loading. However, the dynamic characteristics with tooth modification has to be investigated to avoid the instability to the variation of gear meshing stiffness and the nonlinearity due to gear backlash which results in sub- or super-harmonics in its responses. This research shows the dynamic characteristics with various tooth modifications in its type and quantity.

• Tribology and Lubricants
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• 제25권6호
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• pp.427-431
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• 2009

When a bearing roller is in contact with race ways. excessive pressure peaks occur at the ends of the contact region. They are called edge loading. In this study, a method to determinate crowning quantity of the tapered roller bearing which considers tilting. This method is based on contact analysis.

• Management Science and Financial Engineering
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• 제15권1호
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• pp.33-49
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• 2009

We examine the effectiveness of the conventional (Q, r) model in managing production-inventory systems with finite capacity, stochastic demand, and stochastic order processing times. We show that, for systems with finite production capacity, order replenishment lead times are highly sensitive to loading and order quantity. Consequently, the choice of optimal order quantity and optimal reorder point can vary significantly from those obtained under the usual assumption of a load-independent lead time. More importantly, we show that for a given (Q, r) policy the conventional model can grossly under or over-estimate the actual cost of the policy. In cases where a setup time is associated with placing a production order, we show that the optimal (Q, r) policy derived from the conventional model can, in fact, be infeasible.

• 한국소음진동공학회논문집
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• 제13권9호
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• pp.688-693
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• 2003

To reduce the vibration of a gear driving system. the modification of gear tooth from the orignal involute gear profile is usually done in gear manufacturers. The quantity of tooth modification has been decided on the basis of the interference between two gear teeth during gear meshing and the elastic deformation due to loading. However. the dynamic characteristics with tooth modification has to be investigated to avoid the instability to the variation of gear meshing stiffness and the nonlinearity due to gear backlash which results in sub- or super-harmonics in its responses. This research shows the dynamic characteristics with various tooth modifications in its type and quantity.

• 한국환경과학회지
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• 제10권4호
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• pp.281-286
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• 2001

Wastewater from the pigment industry has high levels of organics and is known as hardly biodegradable. The objective of this study is to evaluate the applicability of aerobic fixed-bed boifilm reactor packed with ceramic support carrier for the pigment wastewater treatment. Orange 2(widely used azo pigment) adsorption experiment onto biofilm and activated sludge, and continuous treatment experiments were performed. In batch adsorption experiment, maximum adsorption quantity of biofilm was at least two times higher than that of activated sludge. In continuous experiment using aerobic fixed-bed biodilm reactor, the influent concentration of COD and Orange 2 were 75~500mg/${\ell}$(0.45~3.00kg COD/$m^3.day), 5~50mg/$\ell$(0.03~0.30kg Orange 2/$m^3$.day), respectively. At a COD loading rate 2.5kg COD/$m^3$.day and Orange 2 loading rate of 0.18kg Orange 2/$m^3$.day, removal efficiency of COD and Orange 2 were over 95%, 97%, respectively.