• Nuclear Engineering and Technology
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• 제39권6호
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• pp.683-690
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• 2007

Because of increasing concerns regarding global warming and the longevity of oil and gas reserves, the importance of nuclear energy as a major source of sustainable energy is gaining recognition worldwide. To make nuclear energy truly sustainable, it is necessary to ensure not only the sustainability of the fuel supply but also the sustained availability of waste repositories, especially those for high-level radioactive waste (HLW). From this perspective, the effort to maximize the waste loading density in a given repository is important for easing repository capacity problems. In most cases, the loading of a repository is controlled by the decay heat of the emplaced waste. In this paper, a comparison of the decay heat characteristics of HLW is made among the various fuel cycle options. It is suggested that, for a future fast breeder reactor (FBR) cycle, the removal and burning of minor actinides (MA) would significantly reduce the heat load in waste and would allow for a reduction of repository size by half.

• Journal of Advanced Marine Engineering and Technology
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• 제39권7호
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• pp.735-743
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• 2015

유기랭킨사이클의 열역학적 효율에 큰 영향을 미치는 구성요소는 터빈이다. 일반적으로 유기랭킨사이클에서 팽창과정은 작동유체의 급격한 물성치 변화를 수반하므로 터빈의 설계에 많은 어려움이 따른다. 그러므로 효율이 우수한 터빈의 개발을 위해서는 정밀한 터빈의 예비설계가 요구된다. 반경류터빈의 효율은 loading과 flow 계수에 큰 영향을 받으므로 터빈의 예비설계에서 이러한 변수의 선정이 매우 중요하다. 그러나 기존의 성능곡선으로부터 loading과 flow 계수를 선정하는 고전적인 방법을 이용할 경우 정밀한 예비설계를 기대하기 힘들다. 그러므로 본 연구에서는 로터 깃의 개수와 열역학적 설계조건으로부터 loading과 flow 계수를 산출하는 방법을 제시하였다. 본 연구에서 제시한 예비설계모델을 이용하여 예비설계를 수행한 결과는 공신력 있는 상용예비설계프로그램을 이용한 결과와 비교하여 만족스러운 것을 확인하였다. 또한 예비설계모델의 정확성을 검증하기 위해 예비설계한 반경류터빈에 대한 수치해석을 수행하였으며 효율을 제외한 대부분의 변수들이 예비설계조건을 비교적 충족하는 것을 확인하였다.

• 복식문화연구
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• 제21권6호
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• pp.967-973
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• 2013

During high speed sewing, the needle thread is exposed to dynamic loading, short strike loading, inertia forces, friction, rubbing, force of check spring, bending, pressure, friction, impact, shock and thermal influence. The dynamic thread loading/tension alters throughout the stitch formation cycle and along its passage through the machine. The greatest tensile force occurs at the moment of stitch stretching, when the take up lever pulls for required thread length through the tension regulator. These stresses act on the thread repeatedly and the thread passes 50-80 times through the fabric, the needle eye and the bobbin case mechanism, before getting incorporated into the seam, which result in upto 40% loss in tensile strength of the sewing thread. This damage in the sewing thread adversely affects its processing and functional performance. In this paper, the contribution of dynamic loading, passage through needle and fabric, and bobbin thread interaction in the loss in tensile properties has been studied. It is observed that the loss in tensile properties occurs mainly due to the bobbin thread interaction. Dynamic loading due to the action of take up lever also causes substantial loss in tenacity and breaking elongation of cotton threads.

• Composites Research
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• 제29권2호
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• pp.60-65
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• 2016

본 연구에서는 Type IV 수소 압력용기 시제품의 충격하중 조건에 따른 구조 건전성을 분석하고자 유한요소해석과 FBG 센서 삽입을 통한 실시간 모니터링 실험을 수행하여 결과를 분석하였다. 플라이 모델링 기법을 활용한 유한요소해석을 통해 FBG 센서를 삽입할 수소 압력용기의 취약부 선정 및 가압 조건을 제시하였으며, 실험을 진행할 기초 정보를 확보하였다. 실제 용기제작에 앞서 시편 실험을 통해 FBG 센서의 삽입방식 신뢰성을 확보하였으며, 이후 해당 결과를 활용하여 필라멘트 와인딩 공정에 적용하였다. 비충격 가압 피로실험과 총 4회의 충격 피로실험을 수행하였다. 실험결과 비충격 가압 피로실험에서는 해석과 동일한 거동을 보였으며, 4회의 충격 피로실험에서는 용기의 충전 시간이 점진적으로 증가하고 충전률은 감소하는 것을 확인하였다.

• Structural Engineering and Mechanics
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• 제88권5호
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• pp.501-519
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• 2023

This paper introduces a new hybrid structural connection joint that combines shear walls with section steel beams, fundamentally resolving the construction complexity issue of requiring pre-embedded connectors in the connection between shear walls and steel beams. Initially, a quasi-static loading scheme with load-deformation dual control was employed to conduct low-cycle repeated loading experiments on five new connection joints. Data was acquired using displacement and strain gauges to compare the energy dissipation coefficients of each specimen. The destruction process of the new connection joints was meticulously observed and recorded, delineating it into three stages. Hysteresis curves and skeleton curves of the joint specimens were plotted based on experimental results, summarizing the energy dissipation performance of the joints. It's noteworthy that the addition of shear walls led to an approximate 17% increase in the energy dissipation coefficient. The energy dissipation coefficients of dog-bone-shaped connection joints with shear walls and cover plates reached 2.043 and 2.059, respectively, exhibiting the most comprehensive hysteresis curves. Additionally, the impact of laminated steel plates covering composite concrete floors on the stiffness of semi-rigid joint ends under excessive stretching should not be disregarded. A comparison with finite element analysis results yielded an error of merely 2.2%, offering substantial evidence for the wide-ranging application prospects of this innovative joint in seismic performance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.9-10
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• 2002

Human circulatory system between heart and tissue is not directly connected in normal condition but mandatory to go through the capillary system in order to fulfill its physiologic aim to deliver oxygen and nutrients, etc. to the tissue and retrieve used blood together with waste products from the tissue properly. When abnormal connection between arterial and venous system (AV fistula), these two circulatory systems respond differently to the hemodynamic impact of this abnormal connection between high pressure (artery) and low pressure (vein) system. Depending upon the location and/or degree (e.g. size and flow) of fistulous condition, each circulatory system exerts different compensatory hemodynamic response to this newly developed abnormal inter-relationship between two systems in order to minimize its hemodynamic impact to own system of different hemodynamic characteristics. Pump action of the heart can assist the failing arterial system directly to maintain arterial circulation against newly established low peripheral resistance by the AV fistula during the compensation period, while it affects venous system in negative way with increased venous loading. However, the negative impact of increased heart action to the venous system is partly compensated by the lymphatic system which is the third circulatory system to assist venous system independently with different hemodynamics. The lymphatic system with own unique Iymphodynamics based on peristaltic circulation from low resistance to high resistance condition, also increases its circulation to assist the compensation of overloaded venous system. Once these compensation mechanisms should fail to fight to newly established hemodynamic condition due to this abnormal AV connection, each system start to show different physiologic ${\underline{de}compensation}$ including heart and lymphatic system. The vicious cycle of decompensation between arterial and vein, two circulatory system affecting each other by mutually negative way steadily progresses to show series of hemodynamic change throughout entire circulation system altogether including heart. Clinical outcome of AV fistula from the compensated status to decompensated status is closely affected by various biological and mechanical factors to make the hemodynmic status more complicated. Proper understanding of these crucial biomechanical factors iii particular on hemodyanmic point of view is mandatory for the advanced assessment of biomechanical impact of AV fistula, since this new advanced concept of AY fistula based on blomechanical information will be able to improve clinical control of the complicated AV fistula, either congenital or acquired.

• 한국환경농학회지
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• 제30권1호
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• pp.24-30
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• 2011

유채 재배 전과정이 환경에 미치는 영향을 전과정평가 기법으로 분석하였다. 유채재배 과정을 평가하기 위해 비료, 농약, 농기계 사용에 따른 에너지 소비량, 작업시간 등을 조사하여 평가의 기능 단위인 유채 1톤을 기준으로 분석하였다. Eco-Indicator 95방법으로 8개 영향범주에 대해 전과정영향을 평가한 결과 유채 1톤을 생산하는데 온실가스 216 kg $CO_2$-eq., 오존층 고갈 3.98E-05 kg CFC-11-eq., 산성화 1.78 kg $SO_2$-eq., 부영양화 0.28 kg $PO_4$-eq., 중금속 5.23E-03 kg Pb-eq., 발암 물질 2.51E-05 kg B(a)p-eq., 스모그 1.24 kg SPM-eq., 에너지자원 6,460 MJ LHV의 영향을 미치는 것으로 나타났다. 이 중 90%가 화학비료에서 기인하는 것으로 분석되었다. 유채 생산량이 1 톤 증가하였을 경우에 대한 민감도 분석에서는 배출량은 동일하였으나 단위 면적당 생산량이 증가하여 유채 1톤에 대한 환경 부하는 22% 감소하는 것으로 평가되었다. 따라서 친환경농업 또는 자원순환농업을 통하여 화학비료의 사용량을 줄이면 유채 재배에 있어 농업부문 온실가스 배출량이 상당부분 감소될 것으로 판단되었다.

• 한국운동역학회지
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• 제18권3호
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• pp.71-82
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• 2008

본 연구의 목적은 $20^{\circ}$ 경사로에 서 앞 뒤 보행 동작 시 지면반력 형태를 비교 분석하고자 한다. 본 연구를 위해서 두 대의 지면 반력기를 통해 전 후, 좌 우, 수직 지면반력값, 최대값, 최소값, 평균값 압력 중심 변위, 부하율과 감소율을 측정하였다. BD보행 시 RTO 시점에서 수직 지면반력값이 FU 보행에 비해 유의하게 높은 수치를 보인 반면, $RHC_2$ 시점에서는 더 낮은 수치를 보였다. 이는 보행 동작의 차이와 보행 시 발목과 무릎의 위치 변화, 무게 중심의 변화가 지면 반력의 형태에 직접적인 영향을 미치는 것으로 판단되어진다. 전 후 압력중심변위는 하향 보행 시 상향 보행에 비해 낮은 변화를 보였는데 이는 하향 시 생기는 불안정성을 상쇄하기 위해 더 강한 제동력이 발생되어 진 것으로 사료되어 진다. BD보행 시 부하율이 다른 보행에 비해 낮은 것을 알 수 있는데 이러한 결과를 통해 등산로에서 후방 보행 동작이 하지 근골격계에 지속적인 스트레스를 감소시켜 상해를 예방할 수 있는 방법으로 제시될 수 있을 것이다.

• 방사성폐기물학회지
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• 제18권4호
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• pp.537-548
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• 2020

Currently, radioactive waste for disposal has been restricted to low and intermediate level radioactive waste generated during operation of nuclear power plants, and these radioactive wastes were managed and disposed of the 200 L and 320 L of steel drums. However, it is expected that it will be difficult to manage a large amount of decommissioning waste of the Kori unit 1 with the existing drums and transportation containers. Accordingly, the KORAD is currently developing various and large-sized containers for packaging, transportation, and disposal of decommissioning waste. In this study, the radiation exposure doses of workers and the public were evaluated using RADTRAN computational analysis code in case of the domestic on-road transportation of new package and transportation containers under development. The results were compared with the domestic annual dose limit. In addition, the sensitivity of the expected exposure dose according to the change in the leakage rate of radionuclides in the waste packaging was evaluated. As a result of the evaluation, it was confirmed that the exposure dose under normal and accident condition was less than the domestic annual exposure dose limit. However, in the case of a number of loading and unloading operations, working systems should be prepared to reduce the exposure of workers.

• 방사성폐기물학회지
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• 제21권4호
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• pp.503-516
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• 2023

A transfer cask serves as the container for transporting and handling canisters loaded with spent nuclear fuels from light water reactors. This study focuses on a cylindrical transfer cask, standing at 5,300 mm with an external diameter of 2,170 mm, featuring impact limiters on the top and bottom sides. The base of the cask body has an openable/closable lid for loading canisters with storage modules. The transfer cask houses a canister containing spent nuclear fuels from lightweight reactors, serving as the confinement boundary while the cask itself lacks the confinement structure. The objective of this study was to conduct a structural analysis evaluation of the transfer cask, currently under development in Korea, ensuring its safety. This evaluation encompasses analyses of loads under normal, off-normal, and accident conditions, adhering to NUREG-2215. Structural integrity was assessed by comparing combined results for each load against stress limits. The results confirm that the transfer cask meets stress limits across normal, off-normal, and accident conditions, establishing its structural safety.