• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.666-674
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• 2021

A selective catalyst reduction system (SCR) with an integrated bypass unit is proposed. Through simulations of the SCR, variations in flow to the catalyst due to the particular shape of the bypass shutting device in the SCR are also studied. The commercial software Ansys Fluent is used to develop the simulations. For the simulations, the catalyst of the SCR is modeled using the porous media method to reduce the calculation time and number of meshes, which is necessary because of the detailed modeling of the catalyst. Simulations are performed based on changes to the entrance angle to the catalyst and the size of the bypass shutting device. Finally, simulation results are used to compare and analyze the average velocity and uniformity of the flow to the catalyst.

• Korean Journal of Optics and Photonics
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• v.24 no.6
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• pp.342-346
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• 2013

We present the thermal analysis result of die bonding for a high power LED package using a metal hybrid silicone adhesive structure. The simulation structure consists of an LED chip, silicone die adhesive, package substrate, silicone-phosphor encapsulation, Al PCB and a heat-sink. As a result, we demonstrate that the heat generated from the chip is easily dissipated through the metal structure. The thermal resistance of the metal hybrid structure was 1.662 K/W. And the thermal resistance of the total package was 5.91 K/W. This result is comparable to the thermal resistance of a eutectic bonded LED package.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.187-196
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• 2013

A numerical model was developed to predict the density wave oscillation (DWO) in the furnace wall tubes of a fossil-fired once-through boiler. The transient flow fields in the tubes were obtained using a 1D finite volume method in the time domain. A header model was also implemented to simulate the parallel tube connection of the wall tubes. The inlet and outlet mass flow variation in one of the parallel tubes was examined after a heat perturbation to find the DWO. After successful verification with experimental results reported in literature, the developed model was applied to the wall tubes of a 700-MW boiler furnace. In contrast to the simulation of Takitani's experiment, in which the unstable power thresholds tended to rise in the reduced bypass channel flow, no remarkable changes were observed in the power thresholds in the parallel channel modeling of the wall tubes of the boiler furnace.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1035-1039
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• 2009

최근 들어 한국철도기술연구원 (KRRI) 에서는 자동운행이 가능한 바이모달 트램 시스템을 개발하고 있다. 이 바이모달 트램 시스템은 노선에 설치된 센서를 자동으로 인식하여 자동 운행을 하며, 재해 발생시 수동으로 운행될 수도 있다. 바이모달 트램 시스템이 노선에 설치된 센서를 인식하여 자동운행을 하기 때문에, 기후패턴 변화에 따른 집중강우로 인해 예기치 않은 홍수 발생시 바이모달 트램 시스템 승객 및 차량의 안전이 확보되어야 한다. 따라서 본 연구에서는 Web GIS 기반의 트램 재해관리 시스템 (Bi-modal Tram Disaster Management System: BTDMS) 프로토타입 버전을 개발하였다. 이 BTDMS 시스템은 US EPA에서 개발한 SWMM 모험을 핵심 엔진으로 활용하여 지표면 유출 및 관거 해석을 수행한다. 본 연구에서는 기상청 예측 강우량 자료를 이용하여 실시간 내수침수 예측을 수행할 수 있는 모듈, 지표면 유출수의 흐름을 고려할 수 있는 모듈, 그리고 지역별로 유출심을 산정하여 바이모달 트램 시스템 운행 판단의 기준자료로 활용할 수 있는 모듈을 개발하여 BTDMS에 추가하였다. 이러한 모듈을 이용하여 예측된 자료는 바이모달 트램 시스템의 운행 속도를 늦추거나 우회노선을 선택하는데 활용될 수 있을 것이다. 본 연구에서 개발한 Web GIS 기반의 BTDMS는 2009년 상반기 밀양 지역에 설치될 바이모달 트램 시범지역에 적용되어 그 적용성이 평가될 것이다.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.17-23
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• 2007

In the present work, flow analysis has been performed in the steam turbine bypass control valve (single-path type) for two different cases i.e., case with steam only and case with both steam and water. The numerical analysis is performed by solving three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations. The shear stress transport (SST) model and $k-{\varepsilon}$ model are used to each different case as turbulence closure. Symmetry condition is applied at the mid plane of the valve while adiabatic condition is used at the outer wall of the cage. Grid independency test is performed to find the optimal number of grid points. The pressure and temperature distributions on the outer wall of the cage are analyzed. The mass flow rate at maximum plug opening condition is compared with the designed mass flow rate. The numerical analysis of multiphase mixing flow(liquid and vapor) is also performed to inspect liquid-vapor volume fraction of bypass valve. The result of volume fraction is useful to estimate both the safety and confidence of valve design.

• Journal of Chest Surgery
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• v.37 no.6
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• pp.511-516
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• 2004

Background: One of the theoretical advantages of skeletonized internal mammary artery harvesting in coronary artery bypass surgery is to minimize the interruption of the sternal blood flow inevitably accompanied by internal mammary harvesting. A study using bone scan is designed to determine the effects of internal mammary artery harvesting technique on the sternal blood flow. Material and Method: From April 2002 to March 2003, 27 patients out of 48 patients who underwent the isolated coronary bypass surgery were enrolled into the study. The enrolled patients underwent bone scan in the preoperative period and postoperative period respectively. Bilateral internal mammary artery was used in 8 patients (BIMA group) and single left internal mammary artery in 19 patients (LIMA group). The patients in LIMA group were divided into two groups: LlMA_skel group, in whom left internal mammary artery was harvested in skeletonized fashion (n=12), and LlMA_ped group, in whom left internal mammary artery was harvested in pedicled fashion (n=7). After the bone scan, the region of interest (ROI) was created on the left of the sternum and the mirror image with the same pixel numbers was placed on the right half of the sternum. The mean counts per pixel on the left side of the sternum was compared with those on the right side and expressed as left to right ratio (L/R ratio). Result: In LIMA group, the L/R ratio decreased from 94.6$\pm$4.1% to 87.9$\pm$6.9% (p=0.003) after the operation as compared to BIMA group, in which no change of the L/R ratio was observed. The changed of the L/R ratio in LlMA_skel group and LlMA_ped group were from 95.3$\pm$4.2% to 88.3$\pm$7.7% and from 93.4$\pm$3.9% to 87.4$\pm$5.8% respectively. The % changes in L/R ratio were -7.44 $\pm$7.08 in LIMA_skel group and -6.17$\pm$9.08 in LiMA_ped group, which did not reach the statistical difference. Conclusion: Ipsilateral sternal blood flow is interrupted by internal mammary artery harvesting as evidenced by the decrease in L/R ratio after left internal mammary artery harvesting irrespective of the harvesting techniques. Skeletonized harvesting did not show superiority in respect to sternal blood flow as compared to pedicled harvesting.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.678-686
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• 2016

The effect of internal and shroud nozzle distributor to bubbling fluidized beds which has the size of $0.3m-ID{\times}2.4m-high$ column was modeled by CPFD (Computational Particle-Fluid Dynamics). Metal-grade silicon particles (MG-Si) were used as bed materials which have $d_p=149{\mu}m$, ${\rho}_p=2,325kg/m^3$ and $U_{mf}=0.02m/s$. Total bed inventory and static bed height were 75 kg and 0.8 m, respectively. Effect of vertical internal on the bubble rising velocity was investigated. Bubbles were split by internal when the axial position of the internal from the distributor, z = 0.45 m. Bed pressure drop and axial solid holdup were not affected by internal. However, in the case that axial distance of internal from distributor was too close to jet penetration length, bubbles were not separated and bypassed internal, and faster than without internal or z = 0.45 m.

• Fire Science and Engineering
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• v.28 no.1
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• pp.31-36
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• 2014

Recently, the safety assessments with using the various evacuation programs are performed for improving the performance of fire and evacuation safety in the building. Generally, the evacuation programs can simulate the human behavior in fire situation by applying the variation of the movement speed and Fractional Effective Dose (FED) index in the smoke. However, if the simulation is performed without optional setting around the fire, the agents do not avoid the fire and they move through the fire. Therefore in this study, we define the radiative repulsion force which exists between the fire and the agents. Moreover, we modify the Helbing's movement model by adding the radiative repulsion force. As a result of the modified movement model, all agents move around the fire and they do not enter the upper bound area of radiative heat flux, $2.4kW/m^2$. From these results, we verified the reliability of the modified movement model.

• Journal of Gastric Cancer
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• v.8 no.3
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• pp.148-153
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• 2008

Purpose: Malignant bowel obstruction caused by recurrent gastric cancer must be treated appropriately to improve the effects of treatment and to prolong survival. We reviewed the surgical treatments for malignant bowel obstruction caused by recurrent gastric cancer. Materials and Methods: The subjects were patients with malignant bowel obstruction caused by recurrent gastric cancer and these patients were treated by surgical procedures at our hospital from 1998 to 2008. The patients were treated by resection, ostomy or bypass. The success of treatment was decided when the patients were able to tolerate more than a liquid diet. Results: 42 patients were treated 46 times by surgical procedures. Resection was done12 times, ostomy was done 24 times and bypass was done 10 times. The hospital stay and the period to liquid diet after the operation were shorter in the ostomy group. The post operative morbidity rate was 21.7% and the post operative death rate was 8.7%. There was no significant difference in survival according to the type of surgery. Conclusion: Ostomy is good choice for selected patients because it has a shorter hospital stay and period to liquid diet. There was no significant difference in survival according to the type of surgery because curative resection is difficult to perform in patients with malignant bowel obstruction.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.10 no.1
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• pp.1-18
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• 1974

Some coastal oceanographic investigations in Kwang Yang Bay were carried out bimonthly from April to September (The first half period of the research project) in 1974. The behaviour of the waters, distributions of water temperature and salinity and diffusion characteristic by dye release experiments in the bay are studied for the problems of practical importance in connection with water pollution. Velocities and directions of tidal currents at five fixed stations were observed. And dye diffusion experiment was also carried out on the sea. According to the results from this study, the salinity of the water is lower, ranging from about $28\;\textperthousand\;to\;32\textperthousand$, on all over the surface in the bay with the cause that the fresh water flows in from the Sumjin river. Diffusivities in this sea by means of Rhodamine B diffusion elliperiment were $785.6\;{\times}\;10^2\;\textrm{m}^2/sec$ in major axis, $15.6\;{\times}\;10^2 \;\textrm{m}^2/sec$/sec in minor axis in the direction on patch after 30 minutes from the dye release.