• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.20-26
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• 2000

• Journal of Chest Surgery
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• 제52권1호
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• pp.16-24
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• 2019

Background: Optimal graft selection for coronary artery bypass grafting (CABG) in patients with severe left ventricular (LV) dysfunction remains debatable. We report an analysis of our experiences of isolated CABG in patients with severe LV dysfunction and the impact of graft strategy on long-term outcomes. Methods: We analyzed 209 patients with severe LV dysfunction (ejection fraction [EF] <30%) who underwent primary isolated CABG. Of these, 169 were revascularized with a bilateral internal thoracic arterial (ITA) graft (BITA group) and 40 were revascularized with a single ITA graft (SITA group). The mean follow-up duration was $22{\pm}32$ months. Results: There were 18 early deaths (8.6%). Overall survival at 5 years was 66.7%. The rate of freedom from cardiac-related death at 5 years was 74.1%, and was significantly higher in patients who underwent off-pump CABG (p=0.005) and in the BITA group (p=0.023). Multivariate analysis demonstrated that old age (hazard ratio [HR], 2.548; 95% confidence interval [CI], 1.134-5.762; p=0.024), off-pump CABG (HR, 0.245; 95% CI, 0.090-0.661; p=0.006), and BITA grafts (HR, 0.333; 95% CI, 0.146-0.757; p=0.009) were correlated with cardiac mortality. Conclusion: CABG in patients with severe LV dysfunction (EF <30%) showed reasonable long-term outcomes. The rate of freedom from cardiac-related death was significantly higher in patients who underwent off-pump CABG and in the BITA group. Off-pump BITA grafting strategies can be accepted as a viable primary option in patients with severe LV dysfunction if performed by an experienced surgeon.

• 한국기계기술학회지
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• 제13권1호
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• pp.113-118
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• 2011

To analyze and verify the effect of replacing thermal storage heater by a cascade cycle heat pump using midnight electricity was installed and tested at a customer's house in Wonju, Korea. The electric night storage heater is consist of 30kW electric heater and 2,700 liters of thermal storage water tank to supply hot water for warming house floor. The power for electric heater was cut off and hot water was only generated by cascade cycle heat pump. Current thermal storage water tank was not eliminated and electric heater wiring was modified. Some operation logic of the heat pump was also modified for proper operation. The required capacity of the heat pump and hot water temperature for given warming condition were estimated. The estimated capacity of heat pump was about 19kW and estimated hot water temperature for proper heating was at least $75^{\circ}C$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.863_864
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• 2009

Design and drive characteristics of SR drive for hydraulic pump system using passive converter is presented in this paper. In oder to get the high performance, a simple passive circuit is added in the front-end of a conventional asymmetric converter, which consists of three diodes and one capacitor. This passive converter has the high demagnetization voltage, to reduce the demagnetization time. Futhermore optimal turn-off angle for the proposed passive converter is proposed. According to motor speed and current, an optimal turn-off angle can be achieved by look-up table to reduce torque ripple. The characteristic of proposed hydraulic pump system using passive converter is verified by simulation and experimental results.

• Journal of Chest Surgery
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• 제37권7호
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• pp.601-605
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• 2004

부신성 위기라 불리는 Addisonian crisis는 스트레스 호르몬의 일종인 cortisol이 분비되어야 하는 상황에서 정상적으로 분비되지 못함으로써 발생한다. 뇌하수체 선중은 기존에 있던 뇌하수체 선종이 어떤 원인에 의해 출혈성 또는 허혈성 변성에 의해 발생하는 것으로 알려져 있으며 심혈관계 수술에 있어 매우 드문 합병증이다. 더구나 심혈관제 수술에서 발생하는 대부분의 뇌하수체 졸중은 체외순환과 연관이 있는 것으로 알려져 있다. 본 증례는 체외순환 없이 시행한 관상동맥 우회로 조성술 후에 뇌하수체 졸중이 발생한 경우로 처음 보였던 여러 증상이 마치 폐혈성 쇼크와 유사하여 진단이 늦어지게 되었다. 그러나 일단 진단이 된 후에는 스트레스 용량의 부신 호르몬을 투여함으로써 급격한 증상 호전을 보였다.

• Journal of Chest Surgery
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• 제39권7호
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• pp.553-555
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• 2006

고혈압과 고지혈증 그리고 허혈성심질환을 가진 62세 여자 환자가 심폐기를 이용하지 않는 관동맥우회술을 시행한 뒤 척추신경경색이 발생하였다. 심폐기를 이용하지 않는 관동맥우회술을 시행하는 경우 신경계 합병증의 발생 빈도는 통상의 관동맥우회술보다 낮다고 알려져 있다. 특히 관동맥우회술후 척추신경경색의 발생은 매우 드물다. 심폐기를 이용하지 않는 관동맥우회술을 시행한 후 척추신경경색이 발생한 1예를 문헌 고찰과 함께 보고하는 바이다.

• Journal of Chest Surgery
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• 제39권9호
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• pp.710-713
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• 2006

관상동맥우회술을 시행 받은 환자가 많아지면서 관상동맥 재수술의 빈도도 증가하고 있다. 또한 기술적인 발전으로 인하여 심폐바이패스 없이 시행하는 관상동맥우회술도 늘고 있다. 저자들은 관상동맥 우회술 후 재발된 76세 불안정성 협심증 환자에게 좌측 개흉술 및 상복부 절개술을 통한 관상동맥재수술을 시행하여 만족스러운 결과를 얻었기에 이를 보고하고자 한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.731-734
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• 2002

There have been no obvious design criteria of high efficient displacement pump using a dimensionless parameter which can represent many physical aspect of displacement pump could be very useful to estimate displacement pump performance. Many dimensionless analysis methods have been developed in fluid dynamics, machine design and so on. In this study a new dimensionless parameter is developed for estimate displacement pump performance and efficiency, until now to evaluate the performance of displacement pumps which are widely used in industry field, primarily experimental methods have been used. The dimensionless parameter contains many physical information about pump design. For example, they are the relation between flow rate and power, displacement operation displacement and size, inlet and outlet valve size. And the developed dimensionless functions are induced from numerical method.

• 한국기계기술학회지
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• 제13권3호
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• pp.93-98
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• 2011

To analyze and evaluate the performance of developing air to water multi heat pump, the heat pump was installed and tested at low energy house in Daejeon, korea. Heating capacity of heat pump is 16.5KW and cooling capacity is 14.0KW. Space heating/cooling, floor heating and hot water is available. The results performance evaluation of heat pump in lab test showed that the coefficient of performance (cop) was 3.75, and heating capacity was 16.0KW in ambient temperature $7^{\circ}C$. Also at ambient temperature $-15^{\circ}C$, the COP was 1.69. At a low energy house, floor heating is controled by a floor heating water temperature and a room temperature. The COP of heat pump is decreased with frequent on/off operation for controlling of floor heating water temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.422-424
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• 2000

Whenever the large-capacitor and high-voltage pump motor is opened and closed, the power factor improvement condenser and the low-voltage equipment are often damaged by the sparking and the on-off power serge. In order to find the reason and resolve the problem, we have installed a transition wave recorder for obtaining the transient on-off power serge wave and a power disturbance analyzer for long-time monitoring. In this way we measured and analysed the condition of the high-voltage pump motor whenever it is opened and closed.