• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 추계 학술대회논문집
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• pp.9-14
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• 2000

Computational methods can be classified roughly into two parts: one is the methods based on a potential flow theory, and the other is numerical solvers(CFD) based on Navier-Stockes equation. Methods based on a potential theory are more effective than CFD when the free surface effect is considered. Especially Rankine source method seems to become widespread for simulations of wave making problems. For computations of viscous flow problems, CFD techniques have rapidly been developed and have shown many successful results in the viscous flow calculation. Present paper introduces a computational system 'WAVIS' which includes a pre-processor, potential ant viscous flow solvers and a post-processor. To validate the system, the calculated results for modem commercial hull forms are compared with measurements. It is found that the results from the system are in good agreement with the experimental data, illustrating the accuracy of the numerical methods employed for WAVIS.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.265-268
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• 2004

In this present study, mechanical properties of the Zr-Ti-Cu-Ni-Be bulk metallic glass are characterized by compression test over a wide range of temperatures and strain rates. Three different types of deformation behavior have been identified as a result, viz., Newtonian viscous flow, non-Newtonian flow and brittle fracture without plastic deformation. A transition state theory is applicable fur the flow stress - strain rate curve that contains the transition from Newtonian to non-Newtonian flow. Based on the relationship between viscosity and strain rate within undercooled liquid state, we can easily obtain the experimental deformation map and suggest the boundaries among different deformation behavior of this alloy.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.753-758
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• 1987

The purpose of ocean thermal energy conversion (OTEC) plant control is to provide stable power efficiently by appropriately regulating the seawater flow rates and the working fluid flow rate under conditions of continually changing seawater temperatures. This paper describes digital control of working fluid flow rate based on an adaptive control theory for the "Imari 2" OTEC plant at Saga University. Provisions have been made for linkage between the software of the adaptive control theory and the hardware of the OTEC plant. In implementing the working fluid flow rate control, if persistency of excitation conditions are lost, the algorithm of identification often exhibits bursting phenomena. To avoid this difficulty, the stopping-and-starting rule for identification was derived and was used for the working fluid flow rate control. Satisfactory control performance was then obtained by using this digital control system.ol system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.371-379
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• 2000

A noise prediction method of axial flow fan is developed by incorporating through-flow method and vortex shedding noise model. Fan noise is assumed to be generated due to the pressure fluctuation induced by wake vortices of fan blades and radiate as diploe distribution. The wake vortices are analyzed by combining Karman vortex street model and through-flow analysis results, and the vortex-induced fluctuating pressure on blade surface is calculated by thin airfoil theory. The predicted sound pressure levels and directivity patterns of fan noise by the present method are favorably compared with fan noise test data. Furthermore, the present method is shown to be very useful for predicting the aero-acoustic performance map of the fan operated at off-design point.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.670-677
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• 2005

In this study, we analyzed the three dimensional unsteady flow field around the motor cooling fan using the unsteady lifting surface theory. We obtained the flow rate for various geometries of fan from the calculated results of velocity field. For the data of design parameter and rotating speed(rpm) of the fan, we can predict the flow rate of the motor cooling fan with thin thickness through numerical analysis without the experimental data of the free stream velocity which is a boundary condition of flow field. the numerical results showed the flow rate within 10% of error in comparison with experimental results. The radial fans, which are often used as internal motor fan were also investigated with the same procedure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1999-2004
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• 2004

Experiments were conducted to investigate the flow characteristics of water through rectangular PDMS microchannels with a hydraulic diameter ranging from 66.67 to 200 ${\mu}m$. In the experiments, the flow rate and pressure drop across the microchannels were measured at steady states. The experimental results were compared with the predictions from the conventional laminar flow theory. A significant difference between the experimental data and the theoretical predictions was found. Experimental results indicate that the pressure gradient and flow friction in microchannels are higher than those from the conventional laminar flow theory. This may be attributed to the fact that there exists effect of surface roughness of the microchannels. In this study, a surface roughness model is implemented to interpret the experimental data. A good agreement between the experimental data and the numerical predictions with a surface roughness model were found.

• Journal of Information Technology Applications and Management
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• 제18권1호
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• pp.75-100
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• 2011

For decades, thousands of corporation introduced knowledge management systems to respond knowledge-based society. However, it seems that the systems merely focusing on knowledge accumulation and its sharing have been bounded by many restrictions in terms of new knowledge creation based on the life cycle of knowledge management systems. Moreover, recently, a variety of knowledge management activities regarding organization, systems, and process is emphasized as a strategic asset for a corporation to create core knowledge. Therefore, this study adopted the Csikszentmihalyi's flow theory to investigate the factors affecting knowledge creation and the success factors of knowledge management systems in virtual space. Prior studies argued that flow experience should be a prerequisite for creative knowledge creation. In that vein, this research revealed the causal relationships for flow experience between the determinants of clear goal, immediate feedback, congruence of challenge and skill. Additionally, it empirically examined how flow experience affected the exploratory behavior of knowledge creation.

• Bulletin of the Korean Chemical Society
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• 제27권9호
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• pp.1433-1438
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• 2006

An AsFlFFF channel was designed and built, and then tested for analysis of pullulans and proteins. Pullulans and proteins having various nominal molecular weights were injected at various conditions of the cross-flow rate ($F_c$) and the channel-out flow rate ($F_{out}$). The retention (measured by the retention ratio R) and the zone broadening (measured by the plate height H) were measured, and then compared with theory. When the incoming flow rate, $f_{in}$ (and thus $F_{out}$) was varied with $F_c$ fixed at 2.5 mL/min, the plate height measured for the pullulan with nominal molecular weight (M) of about 100,000 showed the trend expected by the longitudinal diffusion theory (H decreases with increasing flow rate). In contrast, when $F_{out}$ was varied with the flow rate ratio, $F_c/F_{out}$, fixed constant at 5, the plate height measured for the same sample showed the trend expected from the non-equilibrium theory (H increases with increasing flow rate). Calibration plots (log D vs. log M) obtained with pullulans and proteins were not coincide, probably due to the difference in molecular conformation, suggesting the analysis of pullulans and proteins using AsFlFFF requires independent calibration. It was found that the linearity of the protein-calibration plot was improved by using a buffer solution as the carrier.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 춘계 학술대회
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• pp.231-238
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• 2005

본 연구에서는 유동저항이론을 기초로 하여 연속다공체, 분리단열망 및 연속다공체-분리단열망 공존암반과 같은 3가지 암반을 대상으로 암반 특성에 따른 지하수 유동저항 개념 모델링 및 관계식을 제안하였다. 정상상태조건에서 밀도변동은 고려하지 않았으며 유한 체적법을 이용하였다. 각종 물성치는 블록 중심에서 정의되고, flux는 블록면에서 정의되는 staggered 격자 체계하에서 모든 블록에 대해 Darcy 법칙이 적용되었다. 접촉면에서의 투수계수는 인접면 중심에서 정의된 물성치의 조화평균값을 사용하였다. 유동저항개념을 이용하여 인접한 블록간의 상대압력차와 flux의 관계를 표현하였다. 개개의 단열에서의 유동은 다공암반에서 이용된 방정식과 동일한 형태의 2차원 방정식으로 모사되었다. 본 논문에서 제안된 모델은 추후 다양한 암반 특성별 유동 모사 기법을 개발하는데 많은 기여를 할 것으로 기대된다.

• 한국화재소방학회논문지
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• 제29권5호
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• pp.51-56
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• 2015

본 연구에서는 설계프로그램의 공학적 분석의 수단 또는 가치공학 측면에서 원가절감 등의 목적으로 최적설계 이론과 공학적 이론을 접목시킨 최적설계법을 가스계 소화설비 중 청정소화약제 소화설비의 약제방출량 산출에 응용하였다. 청정소화약제 소화설비의 설계이론과 최적설계 이론을 바탕으로 약제방출량을 최적화시킬 수 있는 최적설계인자를 도출하였고, 이를 설계인자로 구축된 소화설비의 소화성능시험으로 최적설계법의 적합성 여부를 검증함으로써 다른 소화설비에도 최적설계법을 접목할 수 있는 기틀을 마련하였다. 방출헤드의 약제방출량 최적화는 방출헤드 및 배관의 내경, 약제도달시간, 유량과 압력변화 등의 소화약제 유동특성에 대한 제한조건에 의해 결정됨을 확인하였고, 방출헤드의 방출압력과 약제도달시간의 편차는 배관의 압력변화만큼 발생되고 상관관계가 있음을 알 수 있었다.