• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.422-427
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• 2001

There are many problems such as uncertainty of sequencing and irrational interdependence of processes in work breakdown structure of construction project. This study suggests work structuring for improving work reliability and transparency of processes to solve problems of work breakdown structure. Also, It proposes a process design diagram The goal of improving process design by work structuring is to make work flow more reliable and quick while delivering value to the customer. The process design diagram aims at achieving lean project objectives, such as, reduction in the share of non-value adding activities, increased transparency, process simplification and increased product flexibility.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2210-2214
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• 2009

This paper summarizes progress on work under the Asian Pacific FRIEND(Flow Regimes from International Experimental and Network Data - APFRIEND) initiative of the International Hydrological Programme (IHP) of the United Nations Educational, Scientific and Cultural Organisation (UNESCO) from 2005 to 2009. The results of initial work on Rainfall Intensity Duration Frequency (IFD) have just been published as a volume by UNESCO. The results of work to date is concisely presented and observations made about lessons learnt on how to successfully integrate work from nine diverse countries with differing approaches to both hydrology and water resource management structures and on some possible directions for future work.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.215-222
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• 2010

Long and slender body, like a fuel rod, oscillating in axial flow can be unstabilized even by the small cross flow which can be activated by the flow mixer or turbulent generator. It is important to include these effects of flow disturbance in dynamic stability analysis of nuclear fuel rod. This work shows how eigen frequency of a multi-span fuel rod can be changed by the swirl flow, which is discretely generated by a flow mixer. By solving a state-space form of the eigenvalue equation for a multi-span fuel rod system, the critical velocity at which a fuel rod becomes unstable was calculated. Based on the simulation results, we evaluated how stability of a multi-spanned nuclear fuel rod with mixing vanes can be affected by the coolant flow in an operating reactor core.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2769-2774
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• 2007

In vacuum ejector-diffuser systems where a finite volume secondary chamber is used, the secondary jet exhibits transient characteristics during start-up. A steady state is achieved after some time in which mass entrainment prevails indefinitely inside the ejector, though there is no flow from the secondary chamber. An attempt is made in this work to study the infinite entrainment of secondary jet into the primary jet from a finite secondary chamber, with the help of a computational fluid dynamics method. The present study is also intended to identify the operating range of vacuum ejector-diffuser systems where the steady flow assumption can be applied without uncertainty. The results obtained show that the only condition in which an infinite mass entrainment is possible is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium at this point. Steady flow assumption is valid only after this point.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.177-184
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• 2009

Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work has focused on the simulation of cavitating flow past cylinders with strong side flows. The governing equation is the Navier-Stokes equation based on the homogeneous mixture model. The momentum and energy equation is in the mixture phase while the continuity equation is solved liquid and vapor phase, separately. An implicit dual time and preconditioning method are employed for computational analysis. For the code validation, the results from the present solver have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained. After the code validation, the strong side flow was applied to include the wake flow effects of the submarine or ocean tide.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.2
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• pp.96-101
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• 2000

In machining with cutting tool inserts having complex chip groove shape the flow curl and breaking pattern of the chip are different than in flat-face inserts. In the present work an effort is made to understand the three basic phe-nomena occurring in a chip since its formation in machining with groove type and pattern type inserts. These are the ini-tial chip flow the subsequent development of up and side curl and the final chip breaking due to the development of tor-sional and bending stresses. in this paper chip flow angle in a groove type and pattern type inserts. The expres-sion for chip flow angle in groove type and pattern type inserts is also verified experimentally using high speed filming techniques.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1314-1321
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• 1992

In analyzing the plastic flow of axisymmetric tube extrusion a new method of formulation using the stream function approach and upper-bound theorem is proposed which permits the prediction of plastically deformed zone in analytic expression as well as metal flow. It is shown that the formulation proposed in this work covers the solid extrusion and tube extrusion in axisymmetric case. The effect of some process parameters such as area reduction, the ratio of radii(inner radius to outer radius) and friction factor on extrusion pressure, deformation zone and plastic flow through stream-lined dies has been studied. The presented theoretical analysis can be effectively used for the prediction of deformation zone and plastic flow.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.261-267
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• 2005

A comprehensive DES quality numerical analysis has been carried out for reacting flows in constant-area and divergent scramjet combustor configuration with and without a cavity. Transverse injection of hydrogen is considered over a broad range of injection pressure. The corresponding equivalence ratio of the overall fuel-air mixture ranges from 0.167 to 0.50. The work features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the pervious studies. Much of the flow unsteadiness is related not only the cavity, but also to the intrinsic unsteadiness in the flowfield. The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The roles of the cavity, injection pressure, and heat release in determining the flow dynamics are examined systematically.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.489-492
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• 2006

The present work was performed to investigate the thermal and hydraulic characteristics of flow inside the plain and turbulator flat tubes for the automobile application. The pressure drop and heat transfer coefficient at laminar, transition and turbulent regimes were studied experimentally and numerically. The flow transition was confirmed by flow visualization and quantitative data. It is proposed equations for the friction and heat transfer coefficient in the fully developed laminar flow inside rectangular tube as function of aspect ratio.

• 한국가시화정보학회:학술대회논문집
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• 2003.11a
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• pp.75-78
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• 2003

An interfacial instability has recently been observed for the DC- and AC-powered electroosmotic flows of the two miscible electrolyte layers having different concentrations in microchannels. It is rather contrary to our common belief that the flow inside a microchannel is generally stable due to the dominant role of the viscous damping. In this work, we visualized the electroosmotic flow inside a T-channel to validate the numerical predictions. It is clearly shown that the strong vortices (which characterize the interface shapes) are generated at the interface of the two fluids, as was predicted in the numerical analysis.