• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.335-335
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• 2010

한국표준과학연구원 진공센터에서는 국제규격에 바탕을 둔 저진공펌프 종합특성평가시스템을 구축하여 $1100mbar\;{\sim}\;10^{-3}mbar$ 압력 영역에서의 저진공펌프(roots, dry 등)류의 종합특성평가를 시행하고 있다. 저진공펌프 종합특성평가시스템은 국제적 절차에 따른 신뢰성을 바탕으로 구축하고 있으나, 한국표준과학연구원 진공센터 뿐만 아니라, 국내에서도 고진공 종합특성평가 시스템을 구축 하고 있지 않다. 이에 반도체/디스플레이 등 첨단 공정에서 진공 환경을 조성하는 핵심장비인 고진공펌프의 종합특성평가시스템을 개발하고자 터보펌프(TMP) 1000L/s 급의 database를 구축 하였다. 터보펌프(TMP)는 throughput method와 orifice method 두 가지 방법을 병행하여 pumping speed 측정한다. orifice method는 일종의 미세유량 측정 장치이며, 실험값과 계산값 유량의 오차 범위가 작고 신뢰성을 확보하면 throughput method 만으로 측정할 수 있다. Througput method는 $10^{-6}mbar$ 압력 이상의 영역을 측정하며, ultimate pressure 및 $150^{\circ}C$의 bake-out 을 진행하여 base pressure을 측정 할 수 있으며, $10^{-6}mbar$ 압력 이상의 pumping speed를 측정 할 수 있다. 이에 따른 정압형 유량시스템을 개발 중에 있으며, inlet pressure와 outlet pressure를 이용한 compression ratio를 측정 한다. Orifice method는 ultimate pressure와 base pressure을 측정하며, leak valve를 이용한 컨덕턴스(C)로 pressure ratio을 이용하여 유량값을 계산하며, $10^{-6}mbar$ 압력 이하의 pumping speed를 측정할 수 있다. 또한 throughput method와 orifice method의 pumping speed 뿐만 아니라 소비전력 및 소음, 진동, 온도 등 특성평가 관련 사항들의 전반적인 사항을 평가하여 터보펌프(TMP) 1000L/s 급의 database를 구축한다. 향후 예비 실험을 통한 고진공펌프의 종합특성평가시스템을 완비해 나가며, 고진공펌프 종합 특성평가시스템을 통하여 국제적으로 공인받을 수 있는 평가기준을 확립하고 그 기준에 의한 진공/기계적 성능의 전방위적인 종합특성진단과 공정대응성 평가 등 국제적 기술 신뢰성을 확보하고자 한다.

• Journal of Chest Surgery
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• v.37 no.9
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• pp.727-734
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• 2004

The Lecompte procedure for transposition of the great arteries has an advantage because it obviates the need for an extracardiac conduit for the reconstruction of the pulmonary outflow tract. We evaluated the effectiveness and the application of the Lecompte procedure. Material and Method: A retrospective review was conducted of the records of 46 patients who underwent the Lecompte procedure during the past 15 years. Mean age at operation was 29.2$\pm$20.3 (range: 3∼83) months. The diagnoses involved anomalies of the ventriculoarterial connection with ventricular septal defect and pulmonary outflow tract obstruction, such as transposition of the great arteries, double-outlet right ventricle, and double-outlet left ventricle. Result: Early mortality was 4.4% (2 of 46 patients) and late mortality was 6.8% (3 of 44). The mean follow-up was 11.2$\pm$6.9 years. Eighteen patients (43.9% of survivors, n=41) had pulmonary stenosis (pressure gradient above 30 mmHg), the main reason for which was a calcified monocusp valve (n=15, 83.3%). Seventeen of 46 patients (37.0%) underwent reoperation: 15 for pulmonary stenosis, 5 for residual ventricular septal defect, 4 for left ventricular outflow tract obstruction, 3 for pulmonary insufficiency, and 4 for other causes. The cumulative survival rates were 91.3$\pm$4.2%, and 87.0$\pm$5.8% at 10 and 15 years, respectively. The actuarial probabilities of freedom from reoperation for pulmonary stenosis were 90.6$\pm$4.5%, 73.9$\pm$7.3%, and 54.0$\pm$10.4% at 5, 10, and 15 years, respectively. Conclusion: The Lecompte procedure is an effective treatment modality. Repair in early age is possible with acceptable morbidity and mortality, but recurrent right ventricular outflow tract obstruction caused by degeneration of the monocusp valve is a problem that needs resolution.

• Journal of Chest Surgery
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• v.41 no.1
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• pp.1-11
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• 2008

Background: The Damus-Kaye-Stansel (DKS) procedure is a proximal MPA-ascending aorta anastomosis used to relieve systemic ventricular outflow tract obstructions (SVOTO) and pulmonary hypertension. The purpose of this study was to review the indications and outcomes of the DKS procedure, including the DKS pathway and semilunar valve function. Material and Method: A retrospective review of 28 patients who underwent a DKS procedure between May 1994 and April 2006 was performed. The median age at operation was 5.3 months ($13\;days{\sim}38.1\;months$) and body weight was 5.0 kg ($2.9{\sim}13.5\;kg$). Preoperative pressure gradients were $25.3{\pm}15.7\;mmHg$ ($10{\sim}60\;mmHg$). Eighteen patients underwent a preliminary pulmonary artery banding as an initial palliation. Preoperative main diagnoses were double outlet right ventricle in 9 patients, double inlet left ventricle with ventriculoarterial discordance in 6,. another functional univentricular heart in 5, Criss-cross heart in 4, complete atrioventricular septal defect in 3, and hypoplastic left heart variant in 1. DKS techniques included end-to-side anastomosis with patch augmentation in 14 patients, classical end-to-side anastomosis in 6, Lamberti method (double-barrel) in 3, and others in 5. The bidirectional cavopulmonary shunt and Fontan procedure were concomitantly performed in 6 and 2 patients, respectively. Result: There were 4 hospital deaths (14.3%), and 3 late deaths (12.5%) with a follow-up duration of $62.7{\pm}38.9$ months ($3.3{\sim}128.1$ months). Kaplan-Meier estimated actuarial survival was $71.9%{\pm}9.3%$ at 10 years. Multivariate analysis showed right ventricle type single ventricle (hazard ratio=13.960, p=0.004) and the DKS procedure as initial operation (hazard ratio=6.767, p=0.042) as significant mortality risk factors. Four patients underwent staged biventricular repair and 13 received Fontan completion. No SVOTO was detected after the procedure by either cardiac catheterization or echocardiography except in one patient. There was no semiulnar valve regurgitation (>Gr II) or semilunar valve-related reoperation, but one patient (3.6%) who underwent classical end-to-side anastomosis needed reoperation for pulmonary artery stenosis caused by compression of the enlarged DKS pathway. The freedom from reoperation for the DKS pathway and semilunar valve was 87.5% at 10 years after operation. Conclusion: The DKS procedure can improve the management of SVOTO, and facilitate the selected patients who are high risk for biventricular repair just after birth to undergo successful staged biventricular repair. Preliminary pulmonary artery banding is a safe and effective procedure that improves the likelihood of successful DKS by decreasing pulmonary vascular resistance. The long-term outcome of the DKS procedure for semilunar valve function, DKS pathway, and relief of SVOTO is satisfactory.

• Journal of the Korean Institute of Gas
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• v.19 no.3
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• pp.9-17
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• 2015

Almost all of the natural gas consumed in South Korea is compressed into very high pressure for the transportation through the underground pipelines, then reduced in pressure regulation stations before delivery to the consumer. For pressure reduction, expansion valves have been used due to the simple and effective installation, but recover none of the energy in the gas during compression. Hence, turbo-expanders are proposed instead of the valves to accomplish the same pressure letdown function and recover some of the compression energy in the form of shaft work converting into electric powers. Here we have theoretically calculated the electric powers at the pressure reduction from 68.7 bar to 23 bar (which are the average values taken at the inlet and outlet points of the expansion valve in medium-pressure regulation stations) according to the inlet conditions of temperature and flow rate. The natural gas is considered as two cases of a pure methane and the mixture of hydrocarbons with a very small amount of nitrogen, and the Peng-Robinson equation of state is employed for the calculation of required thermodynamic properties. The electric energy is recovered as much as 1596 MW(methane) and 1567 MW(mixture) based on the total supply of natural gas in 2013.

• Journal of Energy Engineering
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• v.23 no.2
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• pp.62-73
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• 2014

This research was focused to apply response surface methodology for optimization of bio-methane production by biogas upgrading process. Methane concentration(Y1) and methane efficiency(Y2) on biogas upgrading process were mathematically described as being modeled by the use of the Box-Behnken design on response surface methodology. The results of ANOVA(analysis of variance) about models, the probability value of the methane concentration and methane recovery response surface model are 0.0001 and 0.0001, respectively and coefficient of determination($R^2$) are 0.9788 and 0.9710, respectively. The response surface model is proved of high reliability and suitability. The operation pressure had the greatest influence to methane concentration than other operation parameters and the PSA rotary valve velocity had the greatest influence to methane recovery than other operation parameters. Optimal condition of biogas upgrading process for production of $100Nm^3/hr$ bio-methane were operation pressure 8.0bar and outlet flow rate 31.55RPM, respectively. At that operation condition the methane concentration of bio-methane was 97.13% and methane recovery in biogas upgrading process was 75.89%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.160-166
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• 2018

The worldwide semi-conductor market has been growing for a long time. Manufacturing lines of semi-conductors need to handle several types of toxic gases. In particular, they need to be controlled accurately in real time. This type of toxic gas control system consists of many different kinds of parts, e.g., fittings, valves, tubes, filters, and regulators. These parts obviously need to be manufactured precisely and be corrosion resistant because they have to control high pressure gases for long periods without any leakage. For this, surface machining and hardening technologies of the metal block and metal gasket need to be studied. This type of study depends on various factors, such as geometric shapes, part materials, surface hardening method, and gas pressures. This paper presents strong concerns on a series of simulation processes regarding the differences between the inlet and outlet pressures considering several different fluid velocity, tube diameters, and V-angles. Indeed, this study will very helpful to determine the important design factors as well as precisely manufacture these parts. The EP (Electrolytic Polishing) process was used to obtain cleaner surfaces, and hardness tests were carried out after the EP process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.924-930
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• 2018

The objective of this study was to investigate heating performance characteristics of electric heat pump system in a fuel cell electric vehicle (FCEV). In order to analyze heating performance characteristics of electric heat pump system with plate-type heat exchanger using stack coolant to evaporate the refrigerant, R-134a, each component was installed and tested under various operating conditions, such as air inlet temperature of inner condenser and compressor speed. When the air inlet temperature of inner condenser was varied from $0.0^{\circ}C$ to $-20.0^{\circ}C$, heating capacity was not quite different due to similar temperature gap between inlet and outlet of inner condenser with electric-driven expansion valve (EEV). However, COP increased until certain EEV opening, especially under 45.0%, because of decreasing power consumption. According to the compressor speed variation from 2,000 to 4,000 RPM, heating capacity and COP were found to have opposite trend. In the future works, stack coolant conditions as the heat source for tested heat pump system were analyzed with respect to heating performance, such as heating capacity and COP.

• Journal of Chest Surgery
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• v.37 no.6
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• pp.504-510
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• 2004

Background: Vasodilatory shock after cardiac surgery may result from the vasopressin deficiency following cardio-pulmonary bypass and sepsis, which did not respond to usual intravenous inotropes. In contrast to the adult patients, the effectiveness of vasopressin for vasodilatory shock in children has not been known well and so we reviewed our experience of vasopressin therapy in the small babies with a cardiac disease. Material and Method: Between February and August 2003, intravenous vasopressin was administrated in 6 patients for vasodilatory shock despite being supported on intravenous inotropes after cardiac surgery. Median age at operation was 25 days old (ranges; 2∼41 days) and median body weight was 2,870 grams (ranges; 900∼3,530 grams). Preoperative diag-noses were complete transposition of the great arteries in 2 patients, hypoplastic left heart syndrome in 1, Fallot type double-outlet right ventricle in 1, aortic coarctation with severe atrioventricular valve regurgitation in 1, and total anomalous pulmonary venous return in 1. Total repair and palliative repair were undertaken in each 3 patient. Result: Most patients showed vasodilatory shock not responding to the inotropes and required the vasopressin therapy within 24 hours after cardiac surgery and its readministration for septic shock. The dosing range for vasopressin was 0.0002∼0.008 unit/kg/minute with a median total time of its administration of 59 hours (ranges; 26∼140 hours). Systolic blood pressure before, 1 hour, and 6 hours after its administration were 42.7$\pm$7.4 mmHg, 53.7$\pm$11.4 mmHg, and 56.3$\pm$13.4 mmHg, respectively, which shows a significant increase in systolic blood pressure (systolic pressure 1hour and 6 hours after the administration compared to before the administration; p=0.042 in all). Inotropic indexes before, 6 hour, and 12 hours after its administration were 32.3$\pm$7.2, 21.0$\pm$8.4, and 21.2$\pm$8.9, respectively, which reveals a significant decrease in inotropic index (inotropic indexes 6 hour and 12 hours after the administration compared to before the administration; p=0.027 in all). Significant metabolic acidosis and decreased urine output related to systemic hypoperfusion were not found after vasopressin admin- istration. Conclusion: In young children suffering from vasodilatory shock not responding to common inotropes despite normal ventricular contractility, intravenous vasopressin reveals to be an effective vasoconstrictor to increase systolic blood pressure and to mitigate the complications related to higher doses of inotropes.

• Journal of Chest Surgery
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• v.32 no.9
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• pp.781-789
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• 1999

Background: Pulmonary artery banding(PAB) accompanies some risks in the aspect of band complications and mortality in the second-stage operation. To assess these risks of the second-stage operation after PAB, we reviewed the surgical results of the second-stage operation in the pediatric patients who had undergone PAB in infancy. Material and Method: From May 1988 to June 1997, a total of 29 patients with preliminary PAB underwent open heart surgery. Ages ranged from 2 to 45 months(mean 20.6$\pm$9.0 months). Preoperative congestive heart failure conditions were improved after PAB(elective operation group) in 27 patients, but early second-stage procedures were required in the remaining 2 patients due to sustaining congestive heart failure(early operation group). Preoperative surgical indications included 2 double outlet right ventricles(DORV group) and 27 ventricular septal defects as the main cardiac anomaly(VSD group). Result: The mean time interval from PAB to the second-stage operation was 15.5$\pm$8.7 months(range 5 days to 45 months). One patient in the DORV group underwent intraventricular tunnel repair and modified Glenn procedure in the other. In the VSD group, the VSD was closed with a Dacron patch in all patients. Concomitant procedures included a right ventricular infundibulectomy in 4 patients and a valvectomy of the dysplastic pulmonary valve in 1 patient. At the second-stage operations, pulmonary angioplasty was required due to the stenotic banding sites in 18 patients. One patient underwent complete ligation of the main pulmonary artery with the modified Glenn procedure. The mortality at the second-stage operation was 17.2%(5 patients). Causes of death were 4 low cardiac output, and 1 autoimmune hemolytic anemia. Diagnosis with DORV and the early operative group were the risk factors for operative death in this series. There was 1 late death. Conclusion: This study revealed the second-stage operation for pulmonary artery debanding and closure of VSD in children was complicated by the correction of the acquired lesions with a significantly high incidence of morbidity and early postoperative deaths. Primary repair is recommended for isolated VSD, if possible.