• 한국CDE학회논문집
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• 제14권6호
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• pp.424-433
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• 2009

In order to improve productivity and efficiency of ship production process, production technology converged with Information Technology can be considered. Mid-term scheduling based on long-term schedule of ship building and execution planning based on short-term production schedule have an important role in ship production processes and techniques. However, data used in the scheduling are from the experiences of the past, cognitive, and often inaccurate, moreover the updates of the data by formatted documents are not being performed efficiently. This paper designs the tracking and monitoring system for the curved plates forming process with shop level. At first step to it, we redefine and analyze the curved plates forming process by using SysML. From the definition and analysis of the curved plates forming process, we design the system with respect to operational view considering operational environment and interactions between systems included and scenario about operation, and with respect to system view considering functionalities and interfaces of the system. In order to study the feasibility of the system designed, a prototype of the system has been implemented with 13.56 MHz RHD hardware and application software.

• 산업경영시스템학회지
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• 제44권3호
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• pp.22-32
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• 2021

To meet rapidly changing market demands, manufacturers strive to increase both of productivity and diversity at the same time. As a part of those effort, they are applying flexible manufacturing systems that produce multiple types and/or options of products at a single production line. This paper studies such flexible manufacturing system with multiple types of products, multiple Bernoulli reliability machines and dedicated buffers between them for each of product types. As one of the prevalent control policies, priority based policy is applied at each machines to select the product to be processed. To analyze such system and its performance measures exactly, Markov chain models are applied. Because it is too complex to define all relative transient and its probabilities for each state, an algorithm to update transient state probability are introduced. Based on the steady state probability, some performance measures such as production rate, WIP-based measures, blocking probability and starvation probability are derived. Some system properties are also addressed. There is a property of non-conservation of flow, which means the product ratio at the input flow is not conserved at the succeeding flows. In addition, it is also found that increased buffer capacity does not guarantee improved production rate in this system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2038-2043
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• 2007

Analysis of the internal state of the blast furnace is needed to predict and control the operating condition. Especially, it is important to develop modeling of blast furnace for predicting cohesive zone because shape of cohesive zone influences on overall operating condition of blast furnace such as gas flow, temperature distribution and chemical reactions. Because many previous blast furnace models assumed cohesive zone to be fixed, they can't evaluate change of cohesive zone shape by operation condition such as PCR, blast condition and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace process using the general purpose-simulation code. And Porous media is assumed for the gas flow and the potential flow for the solid flow. Velocity, pressure and temperature distribution for gas and solid are displayed as the simulation results. The cohesive zones are figured in 3 different operating conditions.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.103-104
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• 2002

The influence of the slip flow on the MEMS/MST based gas-lubricated proceeding bearing is investigated. Based on the modified Reynolds equation, the numerical analysis of the finite difference method was developed by applying the first order slip flow approximation. The numerical prediction of bearing performance provides the significant results concerning the slip flow effect in micro scale gas-lubricated proceeding bearing. The result indicates that the load-carrying capacity as well as the rotordynamic coefficients were significantly reduced due to the slip flow. Through this work, it is concluded that the slip flow effect could not be ignored in the micro gas-lubricated proceeding bearing.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.110-112
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• 2003

A numerical simulation of an incompressible cavity flow is conducted using turbulence models. Cavity geometry and flow conditions are based on Cattafesta's experiment. Baldwin-Lomax model and ${\kappa}-{\varpi}$ model are employed. While simulation with Baldwin-Lomax model predicts the oscillatory features of the flow, the use of ${\kappa}-{\varpi}$ model in its original form makes the simulation converge to steady flow. To acquire oscillatory flow solution, Kato-Launder form and Time scale bound are adopted in production term of ${\kappa}-{\varpi}$ model. The strouhal number of the flow oscillations from the simulation results corresponds to 1 st mode in simulation but 2 nd mode in experiments. However mean velocity profile is in good agreement with the experimental data and the fluctuation profile follows the tendency of Cattafesta's results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2162-2167
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• 2003

It is well-known that high anisotropic characteristic of turbulent flow field is dominant inside tip leakage vortex. This anisotropic nature of turbulence invalidates the use of the conventional isotropic eddy viscosity turbulence model based on the Boussinesq assumption. In this study, to check whether an anisotropic turbulence model is superior to the isotropic ones or not, the results obtained from steady-state Reynolds averaged Navier-Stokes simulations based on the RNG ${\kappa}-{\varepsilon}$ and the Reynolds stress model in two test cases, such as a linear compressor cascade and a forward-swept axial-flow fan, are compared with experimental data. Through the comparative study of turbulence models, it is clearly shown that the Reynolds stress model, which can express the production term and body-force term induced by system rotation without any modeling, should be used to predict the complex tip leakage flow, including the locus of tip leakage vortex center, quantitatively.

• 한국농공학회지
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• 제35권2호
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• pp.57-64
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• 1993

A modified kinematic wave model of the overland flow in vegetated filter strips was developed. The model can predict both flow depth and hydraulic radius of the flow. Existing models can predict only mean flow depth. By using the hydraulic radius, erosion, deposition and flow's transport capacity can be more rationally computed. Spacing hydraulic radius was used to compute flow's hydraulic radius. Numerical solution of the model was accomplished by using both a second-order nonlinear scheme and a linear solution scheme. The nonlinear portion of the model ensures convergence and the linear portion of the model provides rapid computations. This second-order nonlinear scheme minimizes numerical computation errors that may be caused by linearization of a nonlinear model. This model can also be applied to golf courses, parks, no-till fields to route runoff and production and attenuation of many nonpoint source pollutants.

• 한국항공운항학회지
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• 제30권3호
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• pp.38-53
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• 2022

Recently, the acquisition and production of information using digital tools and the creation of new knowledge are emphasized as important educational elements. Therefore, in this study, the effect of learning achievement according to the digital literacy level of college students was analyzed. For the analysis, a questionnaire is conducted with college students majoring in aviation services attending universities in Seoul Capital Area and Chungcheong area. To verify the hypothesis of the study, demographic characteristics are identified based on the questionnaire, reliability and validity of measurement items are verified, and structural equation model analysis is performed to verify the hypothesis. The analysis results are as follows. First, among the sub-factors of digital literacy competency of college students majoring in aviation service, 'technology use' is found to have a positive effect on 'cognitive flow' and 'emotional flow' of learning flow except 'behavioral flow'. Second, among the sub-factors of digital literacy competency, 'self-learning' is found to have a positive effect on 'cognitive flow', 'emotional flow', and 'behavioral flow' in learning flow. Third, the sub-factors of learning flow, 'cognitive flow', 'emotional flow', and 'behavioral flow' have a positive effect on 'learning satisfaction'. Fourth, 'learning satisfaction' is found to have a positive effect on 'learning outcomes'. Based on the research results, practical support measures and strategies for educational success are presented.

• 한국지반공학회논문집
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• 제35권4호
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• pp.37-42
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• 2019

메탄을 생산하기 위한 하이드레이트 해리시 물과 메탄이 동시에 발생한다. 따라서, 지반 내 이온수의 담수화 및 다상유체의 흐름이 예상되고, 흙입자의 이동 및 막힘에 영향을 주게 된다. 본 연구는 담수화 및 다상유체 흐름이 대표적 세립토인 고령토 입자의 이동 및 막힘에 어떻게 영향을 주는지 규명하고자 한다. 연구 결과는 다음과 같다. (1) 공극의 크기가 커질수록 최소 막힘 발생 농도가 증가한다. (2) 고령토 입자는 소금물보다 담수에서 쉽게 뭉침 및 공극 막힘이 발생한다. (3) 다상유체 흐름 내에서 고령토의 최소 막힘 발생 농도는 단상유체 흐름에 비해 감소한다. 따라서, 하이드레이트로부터 메탄 생산 시, 담수화 및 다상유체의 흐름 발생으로 인해 고령토의 공극 막힘이 쉽게 발생할 수 있고, 이로 인해 투수계수의 저하로 메탄 생산효율의 저하가 예상됨을 설명하였다.

• 수산해양기술연구
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• 제59권2호
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• pp.164-171
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• 2023

This study analyzed the flow inside floating seedling equipment for Scapharca subcrenata. Due to the aging society of fishing villages, it is impossible to continuously input the labor force. Therefore, it is necessary to improve efficiency. Scapharca subcrenata has high per capita consumption. It serves as an important aquatic food resource. Scapharca subcrenata culture tends to be highly dependent on the natural environment. Production of Scapharca subcrenata is difficult to predict with low stability. In the past, manpower directly installed bamboo nets in mudflats. The seedling equipment devised in this study is a floating type and can be freely moved on the sea according to the prediction of Scapharca subcrenata generation. The flow around the floating seedling equipment was analyzed by numerical analysis. The physical phenomena of the flow around the net inside the floating seedling equipment were visualized. As a result, the space between the floating seedling equipment and the bottom net and the space between the net groups showed a lower flow rate than the inlet flow rate. It is expected that the low flow rate of the floating seedling equipment will have a positive effect on the attachment of Scapharca subcrenata.