• 한국구조물진단유지관리공학회 논문집
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• 제22권6호
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• pp.89-96
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• 2018

교량 시설물은 사회적으로 중요한 기반 시설물로서 공용기간 동안 안전한 관리가 중요하다. 도로교량의 많은 비율을 차지하고 있는 강박스거더교량의 경우 허용응력설계법으로 설계되고 내하력이 평가되어 왔으나, 최근 한계상태설계법으로 설계기준이 변경되었음에도 불구하고 내하력 평가에서는 아직까지 허용응력법을 대부분 사용하고 있는 실정이다. 이에 이 연구에서는 2 가지 설계 방법을 이용하여 다수의 교량에 대한 내하율 평가 결과를 비교하고, 기존의 허용응력법에 의한 내하력을 한계상태법에 의한 내하력으로 환산하는 방법을 모색하고자 하였다. 이 결과는 추후 교량을 관리함에 있어 보강 필요성 판단 및 한계상태법에 의한 내하력 평가에 기초자료로 활용될 수 있을 것으로 기대된다.

• 천문학회보
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• 제41권1호
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• pp.44.2-44.2
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• 2016

The solar wind electrons are made of three or four distinct components, which are core Maxwellian background, isotropic halo, and super-halo (and sometimes, highly field-aligned strahl component which can be considered as a fourth element). We put forth a steady-state model for the solar wind electrons by considering both the steady-state particle and wave kinetic equations. Since the steady-state solar wind electron VDFs and the steady-state wave fluctuation spectrum are related to each other, we also investigate the complete fluctuation spectra in the whistler and Langmuir frequency ranges by considering halo- and superhalo-like model electron VDFs. It is found that the energetic electrons make important contributions to the total emission spectrum. Based on this, we complete the steady-state model by considering both the whistler and Langmuir fluctuations. In particular, the Langmuir fluctuation plays an important role in the formation and maintenance of nonthermal electrons.

• 한국공간구조학회논문집
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• 제16권2호
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• pp.39-45
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• 2016

Membrane structure is a system that is stabilized by maintaining a tensile state of the membrane material that originally cannot resist the bending or pressure. Also, it is a system that allows the whole membrane structure to bear external loads caused by wind or precipitation such as snow, rain and etc. Tension relaxation phenomenon can transpire to the tension that is introduced to the fabric over time, due to the innate characteristics of the membrane material. Thus, it is important to accurately understand the size of the membrane tension after the completion of the structures, for maintenance and management purposes. The authors have proposed the principle of theoretically and indirectly measuring the tension by vibrating the membrane surface with sound waves exposures against the surface, which is compartmentalized by a rectangular boundary, and by measuring the natural frequency of the membrane surface that selectively resonates. The authors of this paper measured the tension of preexisting membrane structure for its maintenance by using the developed portable measurement equipment. Through analyzing the measurement data, the authors review the points that should be improved and the technical method for the new maintenance system of membrane tension.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1631-1637
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• 2018

Electric utilities has been considered the necessity to introduce asset management of electric power facilities in order to reduce maintenance cost of existing facilities and to maximize profit. This paper aims to provide data that can helpful to make profitable decision in terms of power transformers which have a significant part in the power system. Therefore, this study is modeling input cost for power transformer during its entire life and also the life cycle cost (LCC) technique is applied. In particular, the variation of transformer state related with maintenance and the variation of the EUAC curve based on cost and effect of maintenance is examined. In this study, the trend of the equivalent uniform annual cost (EUAC) according to maintenance cycle and cost of equipment is analyzed. In line with that, sensitivity analysis influenced by the changes of other cost factors was performed.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 춘계학술대회 및 창립 30주년 심포지엄(논문집)
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• pp.339-344
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• 2006

컨테이너 터미널의 생산성의 주요 지표로서 선박작업 생산성이 강조되고 있으며, 이는 갠트리 크레인의 작업에 크게 의존되고 있다. 갠트리 크레인의 작업시간에 발생되는 고장시간 및 고장수리시간에 의해 크레인의 본선작업 가동율이 결정되며, 이로서 체선시간이 좌우되고 있다. 본 연구에서는 갠트리 크레인의 예방보전 주기를 새롭게 설정함에 의하여 크레인의 고장을 감소시키며, 이로서 선박작업 생산성에 미치는 영향을 지표로서 제시하고자 한다.

• Structural Monitoring and Maintenance
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• 제5권4호
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• pp.489-506
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• 2018

This paper reported test of full-scale cables attached with four types of dampers: viscous damper, passive Magneto-Rheological (MR) damper, friction damper and High Damping Rubber (HDR) damper. The logarithmic decrements of the cable with attached dampers were calculated from free vibration time history. The efficiency ratios of the mean damping ratios of the tested four dampers to theoretical maximum damping ratio were derived, which was very important for practical damper design and parameter optimization. Non-ideal factors affecting damper performance were discussed based on the test results. The effects of concentrated mass and negative stiffness were discussed in detail and compared theoretically. Approximate formulations were derived and verified using numerical solutions. The critical values for non-dimensional concentrated mass coefficient and negative stiffness were identified. Efficiency ratios were approximately 0.6, 0.6, and 0.3 for the viscous damper, passive MR damper and HDR damper, respectively. The efficiency ratio for the friction damper was between 0-1.0. The effects of concentrated mass and negative stiffness on cable damping were positive as both could increase damping ratio; the concentrated mass was more effective than negative stiffness for higher vibration modes.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1132-1140
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• 2007

As it recently appears that Life Cycle Cost Analysis may be considered as new methodology for economic valuation of infrastructure many researches have been made to assess LCC(Life Cycle Cost) of each facility based on a reasonable methods. In general, LCC is composed of construction cost and expected maintenance repair cost. And especially, maintenance repair cost must be estimated to enhance the reliability through systematic and reasonable methods. However in Korea, because high speed railway steel bridges are recently constructed no direct statistical data are available for the account of the maintenance cost and then their maintenance characteristics are not linear yet. Therefore, the approach proposed in the paper utilizes a theoretical determination and degradation of the corrosion and fatigue of the bridges based on Rahgozar et al.(2006)'s model on fatigue notch factor considering into the corrosion to incorporate the corrosion effect into the fatigue strength reduction model. And then, the corresponding probability of failure is calculated in terms of the reliability index using S-N curve to formulate the fatigue limit state. Therefore, this paper proposes the minimum Life Cycle Cost through optimum maintenance plan analysis of high-speed railway steel bridges under construction. Finally, this paper reviews the proposed model in oder to confirm the applicability and feasibility by appling it to high speed railway steel bridges under construction

• Asian-Australasian Journal of Animal Sciences
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• 제26권4호
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• pp.558-563
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• 2013

The present study was conducted to estimate energy requirements for maintenance in laying hens by using indirect calorimetry and energy balance. A total of 576 28-wk-old Nongda-3 laying hens with dwarf gene were randomly allocated into four ME intake levels (86.57, 124.45, 166.63 and 197.20 kcal/kg body weight $(BW)^{0.75}$ per d) with four replicates each. After a 4 d adaptation period, 36 hens from one replicate were maintained in one of the two respiration chambers to measure the heat production (HP) for 3 d during the feeding period and subsequent 3 d fast. Metabolizable energy (ME) intake was partitioned between heat increment (HI), HP associated with activity, fasting HP (FHP) and retained energy (RE). The equilibrium FHP may provide an estimate of NE requirements for maintenance (NEm). Results showed that HP, HI and RE in the fed state increased with ME intake level (p<0.05). Based on the regression of HP on ME intake, the estimated ME requirements for maintenance (MEm) was 113.09 kcal/kg $BW^{0.75}$ per d when ME intake equals HP. The FHP was decreased day by day with the lowest value on the third day of starvation. Except for lowest ME intake level, the FHP increased with ME intake level on the first day of starvation (p<0.05). The FHP at the two higher ME intake levels were greater than that at the two lower ME intake levels (p<0.05) but no difference was found between the two lower ME intake levels. Linear regression of HP from the fed state to zero ME intake yielded a value of 71.02 kcal/kg $BW^{0.75}$ per d, which is higher than the extrapolated FHP at zero ME intake (60.78, 65.23 and 62.14 kcal/kg $BW^{0.75}$ per d for the first, second and third day of fasting, respectively). Fasting time, lighting schedules, calculation methods and duration of adaptation of hens to changes in ME intake level should be properly established when using indirect calorimetry technique to estimate dietary NE content, MEm and NEm for laying hens.

• 가족자원경영과 정책
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• 제10권3호
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• pp.45-62
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• 2006

This research is carried out to inspect the Apartment Management System of Japan, to examine the similarities and differences between the Korean Apartment Management System and the Japanese Apartment Management System. First, as the basis law of apartment management, there exists the Building Unit Ownership Act, the Promotion Law fur Adequate Mansion Management of Japan, the Housing Law, Housing Execution Law and Rule of Korea. Second, the Association of Apartment Owners, an organization of owners of apartments in Japan and the Commission of the Representatives of the Occupants in Korea become the subject of maintenance. The Japan structure is made of the Assembly, the Director and the President. The Korean structure is made of Regular and Temporary Conferences and elected Officers(1 president, at least 2 directors and at least 1 inspector). The Commission of the Representatives of the Occupants and the Organization of Owners of Apartments make bylaws and diverse maintenance rules. Third, the foremost reason why the Korean structure of maintenance of apartments is less efficient than Japan is because of the small number of people dispatched to the living-environment maintenance team and their short terms. It is necessary to grow professionals related to this sector and to have enough public servants that specialize in this. Fourth, although it is compulsory to make long term plans for maintenance based on the Housing Law, because the reserve fund is decided by the maintenance rule(with no compulsory standards of reservation) of each apartment, it is difficult to reserve an adequate amount of reserve fund. So as in the example of the state of Hawaii in America, based on long term plans for maintenance, an execution rule of the Housing Law should be made which enforces to reserve at least 50 percent of future maintenance expenses.

• Journal of Korean Neurosurgical Society
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• 제30권sup1호
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• pp.115-119
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• 2001

Objective : The cause and clinical outcome of cerebral hemorrhage in patients on maintenance hemodialysis have been poorly studied in korea. The purpose of this paper is to clarify the clincal features and the outcome of cerebral hemorrhage in patients on maintenance hemodialysis. Method : We analyzed clincal features and the outcome of cerebral hemorrhage in 14 patients on maintenance hemodialysis. Hematomas were reviewed and evaluated for location, size, and intraventricular extension by the one of the authors without any prior informations. The axial slice of CT film that the hematoma was appeared in maximal dimension was chosen for evaluations. Result : Hypertension was found in 71.4%(10 cases) and motality rate was 78.5%(11 cases). Basal ganglia hemorrhage was found in 50%(7 cases), subcortex in 28.5%(4 cases), pons in 14.2%(2 cases). Size of hematoma in patients on maintenance hemodialysis was significantly larger than that of hypertensive cerebral hemorrhage patients(p=0.0061). The 4 cases of basal ganglia hemorrhage without intraventricular hemorrhage and subarachnoid hemorrhage were good mental state at the onset of stroke because of small mass effect relative to the size of hematoma. The duration of hemodialysis treatment prior to strokes ranged from 1 to 107 months. Strokes developed within 6 hours of the previous hemodialysis are 5 cases. Average serum albumin concentration was 3.4g/dl. The use of heparin is less responsible for the development of cerebral hemorrhage in patients on maintenance hemodialysis Conclusion : Cerebral hemorrhage in patients on maintenance hemodialysis is more severe in terms of hematoma size and clinical outcome. Therefore, the prevention and treatment of cerebral hemorrhage in patients on maintenance hemodialysis should be more aggressive.