• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.46-51
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• 1999

This paper describes the control charcteristics of thermal/flow systems. In thermal/flow systems, the transport lag plays as a dead time causing a deterioration of the controllability. Besides this, such many parameters including the temperature, pressure, and flow rate affect the system response that a control scheme which can deal with multi-input is required. Particularly in a refrigerant compressor test facility, the evaporator and condenser interact each other so that the change in the evaporator pressure cause the condenser pressure to change or vice versa. Therefore, to control the evaporator pressure, not only the cooling water flow rate in the evaporator but also the coolant flow rate in the condenser is considered. Meanwhile, the conventional PID controllers, which is suitable for a single input system, shows a large overshoot for a disturbance input. In this work, the predictive control scheme is introduced and its applicability is discussed for thermal/flow systems.

• The KSFM Journal of Fluid Machinery
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• v.11 no.3
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• pp.7-13
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• 2008

The cavitating flow simulation is of practical importance for many engineering systems, such as pump, turbine, nozzle, Infector, etc. In the present work, a solver for two-phase flows has been developed and applied to simulate the cavitating flows past hydrofoils. The governing equation is the two-phase Navier-Stokes equation, comprised of the continuity equation of liquid and vapor phase. The momentum and energy equation is in the mixture phase. The solver employs an implicit, dual time, preconditioned algorithm using finite difference scheme in curvilinear coordinates. An experimental data and other numerical data were compared with the present results to validate the present solver. It is concluded that the present numerical code has successfully accounted for two-phase Navier-Stokes model of cavitation flow.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1359-1363
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• 2009

The object of this research is to develop a simulation system for earthmoving operations in consideration of the impact of congestion in-between equipment and existing traffic flow around the site. The congestion in-between equipment and traffic flow affect work productivity. The conventional discrete event simulation, however, has limitations in simulating the flow of construction equipment. To consider the impact of congestion in-between equipment and existing traffic flow, in this paper, a multi-agent based simulation model that can realize characteristics of truck behavior more accurately to consider the impact of congestion was proposed. In this simulation model, multiple agents can identify environmental changes and adapt themselves to the new environment. This modeling approach is a better choice for this problem since it describes behavioral characteristics of each agent by sensing changes in dynamic surroundings. This study suggests a detailed system design of the multi-agent based simulation system.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2001.10a
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• pp.25-28
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• 2001

Today enterprises are bringing forward the strong needs for the Global Work Space that is able to realize the collaboration of the virtual enterprise in order to achieve the rapid entrance to market, the quality improvement as well as the cost reduction of their new products. Especially, they are building the efficient Product Management Infrastructure in parallel with the real-time knowledge management for the information generated in the course of a product lifecycle and the Process Innovation making the Concurrent Engineering possible. Building a system in the web environment cannot be the entire effort to realize the Global Work Space within an enterprise that is an essential factor for the reduction of a product development period which in turn contributes to Time to Market. Various work models and processes are found in enterprises and many different application programs are developed and utilized to support these. This study proposes a scheme for the optimized Collaborative Workflow System Architecture that is able to take in and apply various application programs accompanied by the product development work process. Through this, we are to examine various limits and problems existing in the real-time collaborative system between enterprises and to reform these.

• The Journal of the Korea Contents Association
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• v.9 no.5
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• pp.197-205
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• 2009

With the introduction of the computer, convenience at work may have increased but flexibility decreased along with a tendency for humans to become secondary to computers with regards to work schedules. As it exists, from entering the department of radiology to completion of imaging requires a great deal of time and difficulties in understanding the imaging process adds to patient dissatisfaction. Since clinics use RFID bars to track patient locations at comprehensive medical testing centers, departments of radiology may apply RFID and Worklist at the core of the OCS system in order to increase work efficiency and improve work flow. As a result of developing an RFID and Worklist centered OCS program, there was a vast improvement in patient satisfaction and work flow. Theses results are the basis of an RFID system that in the future may be connected to PACS and other systems with an intergrated Worklist. There is a need to realize a plan the can offer ubiquity to hospital work.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2004.11a
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• pp.457-461
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• 2004

The insufficient management o( the risk of preconstruction phase causes the risk of construction phase so it makes bad effects such as the extension of construction time and raising of cost. Therefore, the management of the risk of preconstruction phase is being considered as an important element of success of project and the competitive power of construction companies. This study Is to suggest solution methods for each progress after examining reasons of the risk for the management of the risk of preconstruction phase 1'he progress is limited as earth work, RC work, steel work and curtain wall work. Through the introduction of Knowledge Management system, work flow is made by specialist of each part. The reasons of the risk of progress are chosen through the analysis of work flow and I suggest detailed solutions such as person in charge, the starting point of progress and the information of requirements according to the grade of importance about elements of the risk

• The Journal of the Korea Contents Association
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• v.21 no.1
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• pp.561-571
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• 2021

The 2017 Pohang earthquake left us with issues related to long-term repair and restoration from massive earthquake damage. The existing Earthquake response manual was insufficient to consider the flow of earthquake disaster work and the characteristics of long-lasting earthquake disaster. Accordingly, It is important to analyze and record how to earthquake response work was carried out during the Pohang earthquake. The functions that require the most work and manpower in the event of an earthquake disaster were emergency life stabilization support, facility emergency recovery, and energy functional restoration. As a result of analyzing the difficulties and problems of disaster response by function, it was found that the prevention and preparation for damage in advance was insufficient for each function. In conclusion, we subdivided the response step applied with the concept of time and presented the overall work flow process for thirteen collaboration functions. It is expected that this result will help disaster managers to work effectively in the event of a large scale earthquake.

• Korea-Australia Rheology Journal
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• v.21 no.1
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• pp.47-58
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• 2009

We have investigated the transient behavior of 1D fully developed Poiseuille viscoelastic flow under finite pressure gradient described by the Oldroyd-B and Leonov constitutive equations. For analysis we employ a simple $2^{nd}$ order discretization scheme such as central difference for space and the Crank-Nicolson for time approximation. For the analysis of the Oldroyd-B model, we also apply the analytical solution, which is obtained again in this work in terms of elementary solution procedure simpler than the previous one (Waters and King, 1970). Both models demonstrate qualitatively similar solutions, but their eventual steady flowrate exhibits noticeable difference due to the absence or presence of shear thinning behavior. In the inertialess flow, the flowrate instantaneously attains a large value corresponding to the Newtonian creeping flow and then decreases to its steady value when the applied pressure gradient is low. However with finite liquid density the flow field shows severe fluctuation even accompanying reversals of flow directions. As the assigned pressure gradient increases, the flowrate achieves its steady value significantly higher than its value during oscillations after quite long period of time. We have also illustrated comparison between 1D and 2D results and possible mechanism of complex 2D flow rearrangement employing a previous solution of [mite element computation. In addition, we discuss some mathematical points regarding missing boundary conditions in 2D modeling due to the change of the type of differential equations when varying from inertialess to inertial flow.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.641-646
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• 2008

Long and slender body with or without flexible supports under severe operating condition can be unstabilized even by the small cross flow. Turbulent flow mixer, which actually increases thermal-hydraulic performance of the nuclear fuel by boosting turbulence, disturbs the flow field around the fuel rod and affects dynamic behavior of the nuclear fuel rods. Few studies on this problem can be found in the literature because these effects depend on the specific natures of the support and the design of the system. This work shows how the dynamics of a multi-span fuel rod can be affected by the turbulent flow, which is discretely activated 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 established. 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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.756-765
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• 2002

Experimental work was performed on the flow characteristics of R-22 and R-l34a in small diameter tubes. The experimental apparatus was made up of liquid pump, pre-heater, sight-glass, condenser and measurement instruments. The sight-glass for flow pattern observations was located at the outlet of the pre-heater. The experiment was carried out to show the flow characteristics of R-22 and R-l34a. Data were taken with test conditions in the following ranges; the mass flux was ranged from 100 to 1,000 kg/$m^2s$, the saturation temperature was $30^{\circ}C$ and the vapor quality was ranged from 0.1 to 0.9. The main results were summarized as follows; In the flow patterns during evaporation, the annular flow in a 2 mm inner diameter tube occurred at a relatively lower quality and mass velocity, compared to the flow in a 8mm inner diameter tube. The evaporation flow in small diameter tubes has been shown major deviations with the Mandhane, Taitel-Dukler's and Wambs-ganss' flow pattern maps but it was similar to the Dobson's flow pattern map.