• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.306-315
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• 2000

An experimental study was conducted to examine the internal flow patterns inside the mixing chamber of effervescent atomizers. The mixing chamber has the rectangular cross section ($8mm{\times}2mm$) and made of transparent acrylic plate for flow visualization. The parameters tested were the air/liquid ratio (ALR), injection. pressure, and the nozzle orifice diameter. Three different flow regimes were observed; bubbly, annular, and intermittent flows. In the bubbly flow regime, the discharged mixture was disintegrated into drops through the bubble expansion and the ligament breakup. On the other hand, in the annular flow regime, the liquid annulus was disintegrated into small drops by the aerodynamic interaction between the phases due to the high relative velocities between the gas and the liquid. In the intermittent flow regime, the bubble-expansion/ligament-disintegration mode and the annulus-disintegration mode appeared alternatively. The correlations representing the transition criteria between the two-phase flow patterns within the mixing chamber were proposed based on the drift-flux models.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.25 no.5
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• pp.9-14
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• 2002

A capital investment problem is essentially one of determining whether the anticipated cash inflows from a proposed project are sufficiently attractive to invest funds in the project. The net present value(NPV) criterion and internal rate of return(IRR) criterion are widely used as means of making investment decisions. A positive NPV means the equivalent worth of the inflows is greater than the equivalent worth of outflows, so, the project makes profit. Business people are familiar with rates of return because they all borrow money to finance ventures, even if the money they borrow is their own. Thus they are apt to use the IRR in preference to the NPV. The IRR can be defined as the discount rate that causes the net present value of a cash flow to equal zero. Why the project are accepted if the project's IRR is greater than the investor's minimum attractive rate of return\ulcorner Against the NPV, the definition cannot distinctly explain the concept of the IRR as decision criterion. We present a new definition of the IRR as the ratio of profit on the invested capital.

• The Korean Journal of Nuclear Medicine
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• v.15 no.2
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• pp.19-25
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• 1981

Radionuclide venographies were performed in 138 limbs of 58 patients and X-ray contrast venographies were performed in 23 paitents of them. Positive radionuclide venography findings were area of decreased sponding to the region of thrombosis, abnormal collateral flows below the lesion. The success rate of radionulide venography was 89% and the overall concordance between radionuclide venography and X-ray contrast venography was 91%. Radionuclide venography is simple and easy to perform and less invasive than X-ray contrast venography. These results indicate that radionuclide venography is the most ideal screening test for the detection of venous thrombosis in patient with signs & symptoms of deep vein thrombosis.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.49-55
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• 2004

This paper addresses a numerical simulation of the flow and heat transfer in a simplified model of helically coiled tube steam generator using a general purpose computational fluid dynamic analysis computer code. The steam generator model is comprised of a cylindrical shell and helically coiled tubes. A cold feed water entered the tubes is heated up, evaporates. and finally become a superheated steam with a large amount of heat transferred continuously from the hot compressed water at higher pressure flowing counter-currently through the shell side. For the calculation of tube side two-phase flow field formed by boiling, inhomogeneous two-fluid model is used. Both the internal and external turbulent flows are simulated using the standard k-e model. The conjugate heat transfer analysis method is employed to calculate the conduction in the tube wall with finite thickness and the convections in the internal and external fluids simultaneously so as to match the fluid-wall-fluid interface conditions properly. The numerical calculations are peformed for helically coiled tubes of steam generator at an integral type pressurized water reactor under normal operation. The effects of tube-side inlet flow velocity are discussed in details. The results of present numerical simulation are considered to be physically plausible based on the data and knowledge from previous experimental and numerical studies where available.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.108-111
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• 2003

The main objective of this paper is to module design and pressure relief test a new type of polymer gapless surge arrester for power distribution line. Metal oxide surge arrester for most electric power system applications, power distribution line and electric train are now being used extensively to protect overvoltage due to lightning. Surge arresters with porcelain housing must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of gapless elements in a surge arrester occurs due to flashover, fault short current flows through the arrester and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock, pressure rise, etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.3
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• pp.85-104
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• 2009

Managers have come to realized that a large and increasing amount of sources for a corporate competitive advantage can be found in their company's supply chain. At a fundamental level, there is a similar consensus that building a collaborative supply management is a more effective way of managing firms' supply chains. This paper is an attempt to examine the effects of collaborative supply management by probing a mechanism which shows how competences and/or performance are transferred from suppliers to markets through the supply chains. Research hypotheses regarding the relationships between collaborative supply management, supplier Performance, buyer internal performance (new product development and operational performance), and buyer market performance were empirically validated by utilizing a structural equation modeling analysis. The research result Indicates the positive impacts of a collaborative supply chain on supply performance as well as buyer internal and market performance, which also well illustrate how the improved competence and/or performance of suppliers engendered from the supplier-buyer collaboration flows throughout the entire supply chain.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.69-76
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• 2002

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial and the radial temperature distribution in internal spare of a tube. From the study, fellowing conclusive remarks 7an be made. First, As the number of nozzles increase, separation point move into the hot exit. Second, When we use guide vane type nozzle, the axial temperature distribution constant over the 0.75 of air mass flow rate radio. Third, When we use Spiral type nozzle, axial and radial temperature distribution in the inner space is higher than another nozzle. Fourth, Axial and radial temperature distribution in the inner space vortex-tube is determined by separation point. And separation point is moved by changing of air mass flow rate ratio. At last, A heating apparatus is possible far vortex-tube to use.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.111-115
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• 1997

The objective of present study is to obtain information about stenosis effects on the blood flow in the coronary artery bifurcation. The three dimensional steady of blood in the coronary artery bifurcation with stenosis and without stenosis are simulated using the finite volume method. Apparent viscosity of blood is represented as a function of shear rate by the Carreau models. Velocities vectors and wall shear stresses along the branch tubes with stenosis are compared with those of without stenosis for steady flows. Flow phenomena in the stenosed branch tubes are discussed extensively.

• The Journal of the Acoustical Society of Korea
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• v.14 no.1
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• pp.90-107
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• 1995

In this paper, we propose the time relation model among the media with the concept of time and space on hypermedia system. This model classifies time proceeding relations in the node and among media connected with the link which is extended to internal link (while a current node remains, a destination node of internal link proceeds) and external link(a current node is replaced by a destination node of external link). Using this model, hypermedia system for hypermedia presentation is designed and implemented. This hypermedia system provides editing tools and controllers to created and edit nodes with time relation information, link tool to construct associative relations among nodes and navigation tool to control context flows.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.6
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• pp.688-695
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• 2012

The present study represents the effects of boundary condition on the performance of a centrifugal blower at the interference plane between rotational and stationary domains using three dimensional compressible Navier-Stocks equations. Two boundary conditions, frozen-rotor and stage, are compared to analyze the blower performance. Installation angle between the cutoff of a volute casing and a impeller blade is also introduced to evaluate the blower performance and to understand the internal flow inside the blower. Throughout numerical simulation, it is found that the frozen rotor interface method at the interference plane represents well the variations of flow field inside the blower compared to stage interface method. However, pressure has maximum two percent error according to the installation angles while pressure is almost constant for the stage interface method. And stage interface method can relatively well predict the blower performance. Detailed internal flows of the centrifugal blower are compared and analyzed by numerical simulation.