• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1673-1680
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• 2003

It is essential to operate chemical lasers with supersonic ejector system as the laser output power goes up. In this research, ejector design parameter study was carried out for optimal ejector design through understanding the ejector characteristics and design requirements for chemical lasers operating. Designed ejector was 3D annular type with 2$^{nd}$ -throat geometry and pressurized air was used for primary flow. Ejector design was carried out with two steps, quasi-1D gas dynamics was used for first design and commercial code was used to verify the first design. In this study, to get the effect of ejector geometry on its performance, three cases of primary nozzle area ratio and 2$^{nd}$ -throat cross sectional area and two cases of 2$^{nd}$ -throat L/D ratio experiments were carried out. Primary and secondary pressures were measured to get the mass flow rate ratio, minimum secondary pressure, ejector starting pressure and unstarting pressure at every case. In the result, better performance than design level was shown and optimal ejector design method for chemical lasers was obtained.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.9-15
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• 2005

From the geometric parameter study, an optimal ejector design procedure of pressure recovery system for chemical lasers was acquired. For given primary flow reservoir conditions, an up-scaled ejector was designed and manufactured. In the performance test, secondary mass flow rate of 100g/s air was entrained satisfying the design secondary pressure, $40{\sim}50torr$. Performance validation of a supersonic ejector system along with an investigation of effects of supersonic diffuser was conducted. Placement of the diffuser at the secondary inlet further reduced diffuser upstream pressure to 7torr. Lastly, the duplicate of apparatus (air 500g/s secondary mass flow rate each) was built and connected in parallel to assess proportionality behavior on a system to handle larger mass flow rate. Test and comparison of the parallel unit demonstrated the secondary mass flow rate was proportional to the number of individual units that were brought together maintaining the lasing pressure.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.11
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• pp.141-145
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• 1992

심부전 환자의 심근회복을 도울 수 있는 장비인 전기유압방식 좌심실보조기를 개발하였다. 좌심실보조기는 혈액펌프, 압력펌프, 제어기로 구성되어 있으며, 혈액펌프에 내장된 혈액주머니는 동물실험을 위하여 50 ml의 크기로 제작하였다. 좌심실보조기의 성능평가를 위하여 최대 박출량을 측정하고 있으나 실험실에서 측정된 간은 동물 실험에서 관찰되는 것보다 일반적으로 증가된 박출량을 보이게 된다. 이는 생체에서는 좌심방의 체적이 박동 주기에 따라 변하여 좌심실보조기가 받아들일 수 있는 유효 혈액량이 변하는 반면, 모의순환장치에서는 좌심방을 단순 저장고로 사용하기 때문에 좌심방의 박동주기에 따른 체적변화를 감안하지 못하여 생기는 것이다. 본 실험에서는 모의순환 장치에 체적변화 가능한 100ml 크기의 좌심방을 연결하여 좌심방으로 들어오는 혈류량이 제한된 동물실험 상황을 모방하였다. 좌심실보조기의 제어방식중 수측기 이완기 비율(SD 비율)변화에 따른 좌심방 음압발생효과를 관찰한 결과 SD 비율을 40 %로 유지하면 행정거리가 클때도 좌심실의 음압발생을 줄일 수 있는 것을 관찰하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.181-185
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• 2005

The treated ballast water from previous treatment contains microorganisms and pathogenic organisms in an filtration treatment system. The advantage of this process can be filtrated to minimize the demage to screen clogging of drum filter with sweeping the solids off rotating the surface of the filter. Another advantage is to drop off the solids with controlling revolution of drum screen in pretreatment filtration process. Also the fact that it is easy to attach and detach a several type of screen for getting the expected water quality is another advantage, too. Filter rotation speed at 20rpmis 40.5cmHg and 40rpm is 36.6cmHg. Filter out impurities from ballast water over 60rpm is 35cmHg. Filtration system removal aquatic organism over $80{\mu}m$ in ballast water. This study shows that the filtration treatment system has a potential for the removal of ballast water.

• The korean journal of orthodontics
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• v.33 no.4 s.99
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• pp.235-245
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• 2003

The goal of the present study was to evaluate the effects of PNAM appliance and cheiloplasty on alveolar molding. Samples consisted of 16 unilateral cleft lip and palate infants (10 males and 6 female, mean age=37.0 days after birth, average alveolar cleft gap=10.46m), who were treated with PNAM appliances by one orthodontist and rotation- advancement cheiloplasty by one surgeon in Seoul National University Hospital. Average duration of alveolar molding treatment was 13.10 weeks and these patients were recalled at average 8.31 weeks after cheiloplasty. These patients' models were obtained at initial visit (T0, mean age : $37.0\pm27.89$ days after birth), after successful alveolar molding (T1, mean age : $119.25\pm40.18$ days after birth), and after cheilopasty (T2, mean age : $190.81\pm42.78$ days after birth). Seven linear and five angular variables were measured using 1 : 1 photometry and soft ware program(V-ceph. Cybermed. Seoul, Korea). Paired t-test was performed to investigate statistical significance at p<0.05 level. 1 The posterior parts of alveolar segments were the stable structures during alveolar molding treatment period and after cheiloplasty in infants. 2. The closure of cleft gap during alveolar molding was usually due to backward bending of the whole part of the greater segment. 3. Although forward growth of the greater segment was hindered by alveolar molding, it resumed after cheiloplasty. 4. Increase of anterior inter-segment angle after cheiloplasty was due to the molding effect of the lip scar pressure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.109-117
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• 2015

Aircraft needs an inlet duct to supply the airflow to engine face. A fighter aircraft that requires low radar observability has to hide the engine face in the fuselage to reduce the Radar Cross Section(RCS). Therefore, the flow path of the inlet duct is changed into S-shape. The performance of the aircraft engine is known to be influenced by the shape and the centerline curvature of the S-Duct. In this study, CFD analysis of the RAE M 2129 S-Duct has been performed to investigate the influence of aspect ratio of inlet geometry. The performance of the S-Duct is evaluated in terms of the distortion coefficient. To simulate the flow under adverse pressure gradient better, $k-{\omega}SST$ turbulence model is employed. The computational results are validated with the ARA experimental data. The secondary flow and the flow separation are observed for all computational cases, while the semi-circular geometry has been found to produce the best results.

• Proceedings of KOSOMES biannual meeting
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• 2006.05a
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• pp.79-83
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• 2006

Displayed result that handle particle contaminant and hydrospace organism included in number of ballast that is happened in ship using automatic bade washing filter. Reason that remove first contaminant that is included in number of ballast is that heighten processing effect of after processing process. of the filter. Another advantage is to drop off the solids with controlling revolution of drum screen in pretreatment filtration process. The fact that it is easy to attach and detach a several type of screen for getting the expected water quality is another advantage. Filter rotation speed at 1.0rpm is filter resistance 3.0bar and 3.0rpm is filter resistance 2.8bar. Filter out impurities from ballast water over 6.0rpm is filter resistance 26bar and 10rpm is filter resistance 2.5bar. Filtration system removal aquatic organism over $80{\mu}m$ in ballast water. This study shows that the filtration treatment system has a potential for the treatment of ballast water.

• Membrane Journal
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• v.8 no.2
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• pp.77-85
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• 1998

To treat effectively EDIR (electrodeposition ion removal) wastewater in terms of CO$_{Mn}$ 1,500~2,000 ppm generated from aluminum painting process, a RO (reverse osmosis) process was designed and installed to recover and reuse the concentrated solvent sent back to the electrocodeposition tank while the permeate reused as rinse water. A RO system in which three polyamide-spiral wound modules ($102\Phi \times 1,016L$ mm) connnected in series had been running to treat 20 m$^3$ in waste volume in 3 days batch operation at the condition of system recovery of 30 %, applied pressure 11.5 $kg_f/cm^2$ and room temperature. During 42 hours continuous operation leading to 5-fold decrease in waste volume, nearly constant permeation flux of 390 l/m$^2$-hr was maintained and the permeate with average CO$_{Mn}$, 300 ppm was obtained which could be used for washing the remaining paint solution in ion-exchange tower instead of demineralized water. Also COD$_{Mn}$ rejection as a function of running time was observed to be in the range of 78~87 % and the observed solvent rejections for ethyl cellusolve, buthyl cellusolve and n-butanol were 79 %, 87 % and 70 %, respectively.

• Journal of Chest Surgery
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• v.37 no.8
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• pp.632-643
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• 2004

Background: The Histidine-Tryptophan-Ketoglutarate (HTK) solution has been shown to provide the excellent myocardial protection as a cardioplegia. The HTK solution has relatively low potassium as an arresting agent of myocardium, and low sodium content, and high. concentration of histidine biological buffer which confer a buffering capacity superior to that of blood.. Since HTK solution has an excellent myocardial protective ability, it is reported to protect myocardium from ischemia for a considerable time (120 minutes) with the single infusion of HTK solution as a cardioplegia. The purpose of this study is to evaluate the cardioprotective effect of HTK solution on myocardium when the ischemia is. exceeding 120 minutes at two different temperature (10 to 12$^{\circ}C$, 22 to 24$^{\circ}C$) using the Langendorff apparatus, Material and Method: Hearts from Sprague-Dawley rat, weighing 300 to 340 g, were perfused with Krebs-Henseleit solution at a perfusion pressure of 100 cm $H_2O$. After the stabilization, the heart rate, left ventricular developed pressure (LVDP), and coronary flow were measured. Single dose of HTK solution was infused into the ascending aorta of isolated rat heart and hearts were preserved at four different conditions. In group 1 (n=10), hearts were preserved at deep hypothermia (10∼12$^{\circ}C$) for 2 hours, in group 2 (n=10), hearts were preserved at moderate hypothermia (22∼24$^{\circ}C$) for 2 hours, in group 3 (n=10), hearts were preserved at deep hypothermia for 3 hours, and in group 4 (n=10), hearts were preserved at moderate hypothermia for 3 hours. After the completion of the preservation, the heart rate, left ventricular developed pressure, and coronary flow were measured at 15 minutes, 30 minutes, and 45 minutes after the initiation of reperfusion to assess the cardiac function. Biopsies were also done and mitochondrial scores were counted in two cases of each group for ultrastructural assessment. Result: The present study showed that the change of heart rate was not different between group 1 and group 2, and group 1 and group 3. The heart rate was significantly decreased at 15 minutes in group 4 compared to that of group 1 (p<0.05 by ANCOVA). The heart rate was recovered at 30 minutes and 45 minutes in group 4 with no significant difference compared to that of group 1. The decrease of LVDP was significant at 15 minutes, 30 minutes and 45 minutes in group 4 compared to that of group 1 (p < 0.001 by ANCOVA). Coronary flow was significantly decreased at 15 minutes, 30 minutes, and 45 minutes in group 4 compared to that of group 1 (p < 0.001 by ANCOVA). In ultrastructural assessment, the mean myocardial mitochondrial scores in group 1, group 2, group 3, and group 4 were 1.02$\pm$0.29, 1.52$\pm$0.26, 1.56$\pm$0.45, 2.22$\pm$0.44 respectively. Conclusion: The HTK solution provided excellent myocardial protection regardless of myocardial temperature for 2 hours. But, when ischemic time exceeded 2 hours, the myocardial hemodynamic function and ultrastructural changes were significantly deteriorated at moderate hypotherma (22∼ 24$^{\circ}C$). This indicates that it is recommended to decrease myocardial temperature when myocardial ischemic time exceeds 2 hours with single infusion of HTK solution as a cardioplegia.