• Journal of Chest Surgery
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• v.43 no.1
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• pp.86-88
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• 2010

Implanting a pacemaker is the most often used intervention for treating bradycardia. The most commonly used pacemaker is the intracardiac pacemaker, yet it can have many complications. An infected pacemaker can spread to systemic infection and the condition of the patient can quickly get worse, so if an infected pacemaker is suspected, then the pacemaker must be removed. Apart from the use of interventional methods such as a loop or a weight, we can take a more aggressive approach by using extracorporeal circulation for removal of the pacemaker. We report here on two cases in which extracorporeal circulation was used to remove the infected pacemakers.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.385-395
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• 2009

In this study, a series of numerical analysis has been accomplished on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) in a geothermal heat pump system (GHP) considering the circulating fluid, pipe, grout and soil formation. A finite element analysis program, ABAQUS, was employed to evaluate the temperature distribution on the cross section of the U-loop system involving HDPE pipe/grout/formation and to compare sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system. Especially, the latticed pipe is equipped with a thermal insulation zone in order to reduce thermal interference between the inflow pipe and the outflow pipe. Also, a thermal stress analysis was performed with the aid of ABAQUS. 3-D finite volume analysis program, FLUENT, was adapted to analyze a coupled system between fluid circulation in the pipe and heat transfer and simulate an operating process of the closed-loop vertical ground heat exchanger. In this analysis, the effect of the thermal properties of grout, rate of circulation pump, distance between the inflow pipe and the outflow pipe, and the effectiveness of the latticed HDPE pipe system are taken into account.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.5-15
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• 2012

In this study, a series of CFD (Computational Fluid Dynamics) numerical analyses were performed in order to evaluate the thermal performance of six full-scale closed-loop vertical ground heat exchangers constructed in a test bed located in Wonju. The circulation HDPE pipe, borehole and surrounding ground formation were modeled using FLUENT, a finite-volume method (FVM) program, for analyzing the heat transfer process of the system. Two user-defined functions (UDFs) accounting for the difference in the temperatures of the circulating inflow and outflow fluid and the variation of the surrounding ground temperature with depth were adopted in the FLUENT model. The relevant thermal properties of materials measured in laboratory were used in the numerical analyses to compare the thermal efficiency of various types of the heat exchangers installed in the test bed. The simulation results provide a verification for the in-situ thermal response test (TRT) data. The CFD numerical back-analysis with the ground thermal conductivity of 4 W/mK yielded better agreement with the in-situ thermal response tests than with the ground thermal conductivity of 3 W/mK.

• Korean System Dynamics Review
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• v.15 no.1
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• pp.75-96
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• 2014

This research primarily aims at analyzing major crises originating from marginalizing population, especially in counties. In addition, based on the system dynamics approaches, it pays attention to divulging causal loop structure which has been rather strengthened by diverse interactions among key variables. Judging from simulation works, even though Korea is exposed to unprecedented aging trends over decades, its counter response seems inadequate and insufficient, mostly dismissing a series of impact embedded in the aging dynamics. This research statistically confirms that demographic marginalization trends have already begun in the villages within Eup and Myon counties. Furthermore, this research pinpoints out the fact that it would be almost impossible for majority of villages within Eup and Myon counties to escape from going out of existence in the course of time, as they tend to be entrapped vicious cycle of marginalization or extinction.

• Korean System Dynamics Review
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• v.17 no.1
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• pp.107-134
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• 2016

Accelerated ageing with low fertility is one of the most critical problems in Korea. Because of ageing via low fertility, Korea will face a serious demographic cliff. This research primarily focus on the analyzing the dynamics of the marginal ageing state and decreasing population especially in Eup and Myeon region. This study based on the system dynamics approaches for finding causal loop structure of marginal ageing and critical mass of population disappearing. The results of this study are summarized as follows. First, demographic marginalization trends have already begun in the Eups and Myons of Gun. Second, marginal aging speed in Eup/Myeon areas is causing an population disappearing in the near future. Third, critical mass of population disappearing will begin when the rate of marginal aging is exceed 82% after 2023.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.6
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• pp.489-497
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• 2001

The proposed dobule phase locked loop and active multiple interphase reactor are used to eliminate the circular current and the voltage ripples caused by the system parameter unbalance of parallel connected UPSs. In this paper, digital controller for the dobule PLL and active interphase reactor is implemented with ADSP21061 as an aspect of functional convenience.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.113-116
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• 2002

We demonstrate 16 ch.$\times$2.5 Gb/s WDM transmission over 10,880 km using a re-circulating loop and forward error correction (FEC) code. The performances of all 16 channels were measured to be lower than 10$^{-10}$ .

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.1-4
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• 2004

The PIV measurements are performed to get the quantitative flow visualization around a road vehicle. The model scaled with 1/48 is located in the middle test section of the closed-loop water tunnel and the measuring system consists of CCD camera, diode laser, synchronizer, and computer. The experimental data are obtained at two Reynolds numbers of 50,000 and 100,000 based on the model length. The quasi-three-dimensional isovorticity surfaces, based on two-dimensional velocity field data, are generated. There is little difference between the results in part of the recirculation region and the vorticity contour according to the Reynolds number. Also a little bit complicated three dimensional flows are predicted behind the road vehicle.

• Journal of Power System Engineering
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• v.11 no.4
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• pp.12-17
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• 2007

Recently, many small and medium size diesel vehicles have been equipped with turbocharger and EGR system to get high performance and reduce $NO_x$ emissions but its application to heavy-duty diesel engine is not common yet. In this work, the simulation model for EURO-3 engine was developed using WAVE and then its performance and emission level were verified by comparing with experimental results. The possibility of current EURO-3 engine equipped with LPL EGR system which would be satisfied the EURO-5 regulation are examined. ESC 13 mode was chosen as the primary engine test mode, and the injection timing and fuel quantity were changed to compensate the lost engine performance caused by EGR. The system developed in this study shows that the current EURO-3 engine could satisfy EURO-5 $NO_x$ regulation by applying LPL EGR.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1475-1483
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• 2004

Loop thermosyphon(LTS) has many good characteristics such as low thermal resistance, no power consumption, noiseless operation and small size. To investigate the overall performance of LTS, we have performed various experiments varying three parameters: input power of the heater, working fluid(water, ethanol, FC3283) and filling ratio of the working fluid. At a combination of these parameters, temperature measurements are made at many locations of the LTS. The temperature difference between the evaporator and the condenser is used to obtain the thermal resistance. In addition, flow visualization using a high speed camera is carried out. The thermal resistance is not constant. It is lower at higher input power, which is one of the distinct merits of LTS. Flow instabilities are frequently observed when changing the working fluid, the input power and the filling ratio. The results show that the LTS can be readily put into practical use. Future practical application in electronic cooling is recommended.