• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.118-118
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• 2022

지속적인 학문의 발전을 위해서는 선행연구에 대한 재현성이 무엇보다도 중요하다고 할 수 있다. 하지만 컴퓨터와 소프트웨어의 급속한 발달로 인한 컴퓨터 환경의 다양화, 분석 소프트웨어의 지속적 최신화로 인해서 최근 구축된 모델도 짧게는 몇 달, 길게는 1~2년후면 다양한 에러로 인하여 재현성이 불가능해지고 있다. 이러한 재현성의 극복을 위해서 온라인을 통한 데이터와 소스코드의 공유의 필요성이 제시되고 있으나, 실제로는 개인마다 컴퓨터 환경, 버전, 소프트웨어 설치에 필요한 라이브러리의 버전 또는 디렉토리 등이 달라 단순히 온라인을 통한 데이터와 소스코드의 공유만으로 재현성을 개선하기는 힘든 것이 현실이다. 따라서 이러한 컴퓨터 모델링 환경의 공유는 과거의 형태와 같이 데이터, 소스코드와 매뉴얼의 공유만으로 불가능하다고 할 수 있다. 따라서 본 연구에서는 수자원 모델링의 재현성 개선을 위해 1) 온라인 저장소, 2) 클라우드기반 JupyterHub 모델링 환경과 3) 모델 APIs 3개의 핵심 구성요소를 제시하고, 최근 미국에서 개발된SUMMA(Structure for Unifying Multiple Modeling Alternative) 수자원 모델에 적용하여 재현성 달성을 위한 3개의 핵심 구성요소의 필요성과 용이성을 검증하였다. 첫 번째, 데이터와 모델의 온라인 공유는 FAIR(Findable, Accessible, Interoperable, Reusable) 원칙으로 개발된 수자원분야의 대표적인 온라인 저장소인 HydroShare를 활용하여 모델입력자료를 메타데이터와 함께 공유하였다. 두 번째, HydroShare에서 Web App의 형태로 제공되는 클라우드기반 JupyterHub환경인 CUAHSI JupyterHub(CJH)와 일루노이대학에서 제공하는 CyberGIS-Jupyter for water JupyterHub(CJW)환경에 수자원모델링 환경을 컨테이너(Docker) 환경을 통해 구축·공유하였다. 마지막으로, 클라우드에서 수자원모델의 효율적 이용을 위해 Python기반의SUMMA모델 API인 pySUMMA를 개발·공유하였다. 이와같이 구축된 3개의 핵심 구성요소를 이용하여 2015년 Water Resources Research에 게재된 SUMMA 논문의 9개 Test Cases 중에서 5개를 누구나 쉽게 재현할 수 있음을 증명하였다. 재현성의 중요성에 대한 인식의 증가로 Open과 Transparent Hydrology에 대한 요구가 증대되고 있으며, 이를 위해서 클라우드 기반의 모델링 환경구축 및 제공이 확대되고 있다. 본 연구에서 제시한 HydroShare와 같은 온라인 저장소, CJH와 CJW와 같은 클라우드기반 모델링환경, 모델의 효율적 이용을 위한 모델 APIs는 급속도로 발달하고 있는 컴퓨터 및 소프트웨어 환경에서 핵심구성요소이며, 연구의 재현성 개선을 통해 수자원공학 발전에 기여할 것으로 기대된다.

• Journal of Korean Society of Transportation
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• v.25 no.5
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• pp.125-133
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• 2007

Through open-sky policy, USA and European selected market principle of multiuser. However, in Asian case, major airlines monopolize airports. It is purpose that analyzes fare competition of Asian Hub Airport and the position of Incheon airport in Asia. Passengers required longer time and distance to go to the destination because direct flights decreases. But passengers increased in airport every year. Because of routes that decrease, airlines provide more services of flights. So airlines prefer to Hub Airports. As a result, both passengers and airlines are profitable by various routs and the increased frequency. On the assumption that distance and fare are related, the final formula is as following that defined the air fare from hub(H) to destination(Z) by logarithm. Analysis showed that log Rdist is not 1 but 0.08. As distance increases, fare doesn't increase. If distance from hub to destination airports is longer, Log dist_HZ is negative. It is that fare decreases from origin to destination via hub or that fare increases from hub to destination. HHI_HZ and HHI_AZ are negative. It means that if the degree of monopolization of hub and origin airports is lager, fare decreases from origin to destination via hub. Or fare increases from hub to destination. And it compares the Incheon airport with the other Asian hub airports and it examines the competitive fare by market division. As compared with the Incheon airport, Singapore, Beijing and Narita airports are higher fares. They compete with the other ones by Asian hub airports. But Hong Kong and Taipei airports must have more passengers through fare competition yet.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.5
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• pp.565-574
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• 2003

• Transportation Technology and Policy
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• v.13 no.4
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• pp.57-61
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• 2016

• The Korean Journal of Physiology and Pharmacology
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• v.16 no.3
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• pp.181-186
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• 2012

Fenofibrate is a selective peroxisome proliferator-activated receptor ${\alpha}$ ($PPAR{\alpha}$) activator and is prescribed to treat hyperlipidemia. The mechanism through which $PPAR{\alpha}$ agonists reduce food intake, body weight, and adiposity remains unclear. One explanation for the reduction of food intake is that fenofibrate promotes fatty acid oxidation and increases the production of ketone bodies upon a standard experimental dose of the drug (100~300 mg/kg/day). We observed that low-dose treatment of fenofibrate (30 mg/kg/day), which does not cause significant changes in ketone body synthesis, reduced food intake in Long-Evans Tokushima (LETO) rats. LETO rats are the physiologically normal controls for Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which are obese and cholecystokinin (CCK)-A receptor deficient. We hypothesized that the reduced food intake by fenofibrate-treated LETO rats may be associated with CCK production. To investigate the anorexic effects of fenofibrate in vivo and to determine whether CCK production may be involved, we examined the amount of food intake and CCK production. Fenofibrate-treated OLETF rats did not significantly change their food intake while LETO rats decreased their food intake. Treatment of fenofibrate increased CCK synthesis in the duodenal epithelial cells of both LETO and OLETF rats. The absence of a change in the food intake of OLETF rats, despite the increase in CCK production, may be explained by the absence of CCK-A receptors. Contrary to the OLETF rats, LETO rats, which have normal CCK receptors, presented a decrease in food intake and an increase in CCK production. These results suggest that reduced food intake by fenofibrate treatment may be associated with CCK production.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6D
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• pp.917-926
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• 2006

Transportation Economies of scale are the essential properties of hub networks. One critical property of the hub network design problem is to quantify cost savings which stem from economies of scale, the costs of operating hub facilities and opportunity costs associated with delays stemming from consolidation of traffic flows. Due to the NP-complete property of the hub location problem, however, most previous researchers have focused on the development of heuristic algorithms for approximate solutions. The purpose of this paper is to develop a hub network design model considering transportation economies of scale from the consolidation of traffic flows. The model is designed to consider the uniqueness of hub networks and to determine several cost components. The heuristic algorithms for the developed model are suggested and the results of the model are compared with recently published studies using real data. Results of the analysis show that the proposed model reflects transportation economies of scale due to consolidation of flows. This study can form not only the theoretical basis of an effective and rational hub network design but contribute to the assessment of existing and planned logistics systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.2
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• pp.105-111
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• 2013

Whirl tower test is conducted basically during helicopter rotor system development process. And for whirl tower test of rotor hub system, new design blade or existing blade which is remodeled for new rotor hub system is used. Because of simple shape and efficient aerodynamic characteristic, BO-105 helicopter blade is used for helicopter rotor hub development project widely. Originally BO-105 blade is used for hingeless hub system and blade root is used to flexure. So flap stiffness and lag stiffness at blade root area is relatively low compare with airfoil area. So, in order to apply the BO-105 blade to bearingless hub, blade root area have to be reinforced. And in this process, blade root area's section property is changed. In this paper, we suggest reinforcement method of BO-105 blade root area and study dynamic characteristic of bearingless rotor system with reinforcement BO-105 blade.

• Transactions of Materials Processing
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• v.21 no.7
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• pp.397-402
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• 2012

The flange hub is a main component in an automotive steering system. In general, the flange hub are fabricated by mechanical machining, which is a process where material waste is inevitable. It is well-known that a net-shape cold forging cannot only reduce material waste but can also improve the mechanical strength of the final product. Thus, a forging process design was conducted for production of a flange hub. Significant spring-back occurs around the flange due to its small thickness in conjunction with the residual stresses after forging. In order to achieve the required dimensional accuracy, a process design with appropriate spring-back control is needed. In this study, a modification of the forging die was designed based on FE analysis with the purpose of spring-back compensation. Four kinds of different die designs were evaluated and the optimum design has two times less spring-back than the initial design. The compensation angle of the optimum design is 0.5 degrees. The results have been experimentally confirmed by cold forging of a flange hub and comparing the amount of spring-back between the actual component and the FE analysis.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.183.2-183.2
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• 2010

본 개발에서의 해상용 풍력발전기는 크게 허브와 블레이드를 합한 상부 구조물, 전기 발전기와 연결 조인트의 중간구조물, 각종 제어 장치가 들어있는 제어박스로 나누어진다. 상부 구조물은 Circular Hub 타입의 Darrieus 형상으로 양력(lift)을 이용한 회전력이 발생하며, Circular Hub 타입은 기존의 허브와 블레이드를 연결하여주는 암(arm)에 의해 유발되는 항력토크를 최소화 하기 위한 신개념 형상설계가 이루어 졌으며, 저속에서 우수한 회전특성을 가진다. 이는 바람을 받아 기계적 에너지로 전환 하는 역할을 하며, 풍력발전기의 성능에 직접적인 영향을 미친다. 중간구조물의 전기발전기는, 상부에서 발생된 기계적 에너지를 이용하여 전기적 에너지로 전환 하는 역할을 수행한다. 이렇게 전환된 전기적 에너지는 하부의 제어박스를 거쳐서 해상용 부이(buoy)의 하단에 위치한 베터리 뱅크로 전달, 저장되어 부이에서 쓰이는 전력을 충당하게 된다. 한편 본 개발은 풍력발전기의 공력하중 해석과 로터블레이드의 설계, 풍력발전기의 구조, 진동해석, MPPT 제어컨트롤러와 Breaking controller, 풍동 및 차량시험을 통한 성능평가 및 분석 등의 순으로 개발을 수행하였다.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.559-564
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• 2016

The objectives of this paper are to develop a finite element analysis model to analyze press-fitted and bending load conditions in a press-fitted assembly, and propose a hub shape optimization method to minimize contact pressure near the shaft contact edge. Numerical asymmetric-axisymmetric finite element models have been developed to predict contact stress on press-fitted shafts. The global optimization method, genetic algorithm, local optimization method, and sequential quadratic programming were applied to a press-fitted assembly to optimize the hub contact edge geometry. The results showed that the maximum contact pressure with the optimized hub shape decreased more than 60 % compared to conventional hubs and the maximum contact stress affecting fatigue life was reduced about 47 %. Hub shape optimization can be useful to increase the load capability of press fits in terms of wear and fatigue behavior.