• Journal of Pharmaceutical Investigation
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• 제38권3호
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• pp.177-182
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• 2008

The purposes of this study were to prepare dual-layered coated compact pellets containing three nutrients Glucose, Chromium picolinate, Vitamin C) for rumen bypass. The core compact pellets were prepared by an extrusionspheronization method and then double layered coated with pH independent EC (ethyl cellulose) and pH-dependent polymers ($Eudragit^{(R)}$ E100) using a fluid-bed spray coater. Depending on the coating levels of EC and $Eudragit^{(R)}$ E100, release profiles were variable in simulated rumen (pH 6.8) and abomasums (pH 2.0) fluid using USP apparatus I (basket method). When compact pellets were coated with EC (about 10% level in inner layer) and then $Eudragit^{(R)}$ E100 (20% level in outer layer) in a dual-layered manner, rumen-bypass delivery resisting rumen fluid followed by release in abomasums fluid could possible. The friability was also satisfactory based on chewing behavior of ruminants. The dual-layered coated compact pellets showed smooth surface and distinct inner/outer layers using scanning electron microscopy (SEM). The current rumen bypass delivery system can be also applicable to deliver other nutrients in ruminants.

• 한국항공우주학회지
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• 제39권3호
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• pp.269-278
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• 2011

엔진 제작사의 엔진 시뮬레이션 상세한 정보는 일반적으로 공개되지 않으며 운용자는 엔진제어를 위해 단지 몇몇 파라미터만을 사용할 수 있다. 따라서, 엔진 성능모델을 생성하기 위해서는 제한된 가용 자료를 기초로 할 수 밖에 없다. 본 논문에서는 초음속 항공기용 저바이패스 터보팬엔진 성능 모델링에 관해 기술하였다. 대상 엔진은 Pratt and Whitney F100-PW-229 터보팬 엔진을 적용하였다. F100-PW-229 터보팬 엔진성능 모델을 구축하기 위하여 일반적인 공개된 자료와 문헌 정보를 기초로 하여 설계변수들에 대한 민감도 해석 및 Adaptive Random Search method를 이용한 파라미터 최적화 과정을 통하여 미지의 구성품 특성값들을 예측 적용하였다. 엔진덱 데이터와 구축된 엔진성능 모델의 해석 결과 비교를 통하여 엔진성능 모델이 적합하게 구성되었음을 확인하였다.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.38-45
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• 2004

This paper studies the effects of intake port configuration on the swirl that is key parameter in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on fuel air mixing, combustion and emissions. To investigate the swirl flow generated by various intake ports, steady state flow tests were conducted to evaluate the swirl. Helical port geometry, SCV shape and bypass were selected as the design parameters to increase the swirl flow and parametric study was performed to choose the optimal port shape that would generate a high swirl ratio efficiently. The results revealed that a key factor in generating a high swirl ratio was to suitably control the direction of the intake air flow passing through the valve seat. For these purposes, we changed the distance of helical and tangential port as well as installed bypass near the valve seat and the effects of intake port geometry on in-cylinder flow field were visualized by a laser sheet visualization method. From the experimental results, we found that the swirl ratio and mass flow rate had a trade off relation. In addition, the result indicates that the bypass is a effective method to increase the swirl ratio without sacrificing mass flow rate.

• 대한의용생체공학회:의공학회지
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• 제40권5호
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• pp.197-205
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• 2019

The existing Extracorporeal membrane oxygenation(ECMO) and Cardiopulmonary bypass system(CPB) have been developed and applied to various devices according to their respective indications. However, due to the complicated configuration and difficult usage method, it causes inconvenience to users and there is a risk of an accident. Therefore, smart all-in-one cardiopulmonary circulation device is being developed recently. The smart all-in-one cardiopulmonary assist device consists of a blood pump for cardiopulmonary bypass, a blood oxidizer for cardiopulmonary bypass, a blood circuit for cardiopulmonary bypass, and an artificial cardiopulmonary device. It is an integrated cardiopulmonary bypass device that can be used for a variety of purposes such as emergency, intraoperative, post-operative intensive care, and long-term cardiopulmonary assist, combined with CPB used in open heart surgery and ECMO used when patient's cardiopulmonary function does not work normally. The smart all-in-one cardiopulmonary assist device does not exist as a standard and international standard applicable to advanced medical devices. Therefore, in this study, we will refer to the International Standard for Blood Components, the International Standard for Blood, the Guideline for Blood Products, and prepare applicable performance and safety guidelines to help quality control of medical devices, and contribute to the improvement of the health of people. The guideline, which is the result of conducted a survey of the method of safety and performance test, is based on the principle of all-in-one cardiopulmonary aiding device, related domestic foreign standards, the status of domestic and foreign patents, related literature, blood pump(ISO 18242), blood oxygenator (ISO 7199), and blood circuit (ISO 15676) for cardiopulmonary bypass.The items on blood safety are as follows: American Society for Testing and Materials ASTM F1841-97R17), and in the 2010 Food and Drug Administration's Safety Assessment Guidelines for Medical Assisted Circulatory Devices. In addition, after reviewing the guidelines drawn up through expert consultation bodies including manufacturers / importers, testing inspectors, academia, etc. the final guideline was established through revision and supplementation process. Therefore, we propose guidelines for evaluating the safety and performance of smart all-in-one cardiopulmonary assist devices in line with growing technology.

• Journal of Chest Surgery
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• 제34권8호
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• pp.591-596
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• 2001

체외순환을 이용한 관상동맥우회로술은 수술적인 관상동맥 재관류 기법에서 보편적인 방법으로 여겨지고 있으나, 체외순환후 발생되는 전신적인 염증반응이나 혈액성분의 기계적 손상, 혈액응고장애등의 여러 가지 문제점들이 보고되고 있어, 이러한 합병증들을 피하기 위하여 체외순환을 이용하지 않는 관상동맥우회로술이 점차로 보편화되고 있어 체외순환 및 비체외순환하에서의 관상동맥후회로술을 비교분석하였다. 대상 및 방법: 1999년 3월부터 2000년 9월까지 비체외순환하에서 관상동맥우회로술 14례, 체외순환하에서 관상동맥후회로술 21례를 시행하였으며, 양군에서의 평균수술시간, 술후 기관삽관기간, 평균중환자실 재원기간, 평균재원기간, 수혈량, 술후 강심제의 사용, 술후 심근효소수치를 비교분석하였다. 결과: 평균수술시간은 심박동하 수술군에서 280$\pm$93.1분, 체외순환하 수술군에서 392.4$\pm$80.4분으로 심박동하 수술군에서 짧았으나 문합혈과 개수의 차이를 고려하면 양군에서의 수술시간은 차이가 없는 것으로 생각된다. 술후 기관삽관 시간은 심박동하 수술군에서 2.4$\pm$2.0hr, 체외순환하 수술군에서는 6.9$\pm$4.9hr으로 역시 심박동수술군에서 유의하게 짧았다(p<0.05). 중환자실 평균재원기간은 심박동하 수술군에서 $1.5\pm$0.7일, 체외순환하 수술군에서 2.3$\pm$3.7day 체외순환하 수술군에서 12.0$\pm$4.0day로서 별다른 차이는 관찰되지 않았다. 수술후 양군에서의 수혈량을 관찰하면 자기수혈량이 심박동하 수술군에서 113.6$\pm$173.1ml 체외순환하 수술군에서 478.6$\pm$310.9ml로서 심박동하 수술군에서의 수혈량이 유의하게 적었으며(p<0.05). 수술후 Dopamine, Dobutamine, Epinephrine의 사용량은 통계학적인 유의성은 발견할 수 없었으나, 심박동하 수술군에서 적은 경향을 관찰할 수 있었으며, 수술후 심근효소수치는 체외순환하 수술군에서 더욱 증가하였다. 결론: 비체외순환하 수술군에서 술후 기관 삽관기간, 평균 중환자실 재원기간이 짧으며, 수혈량 및 술후 강심베의 사용이 적으며, 심근보호효과가 뛰어난 것으로 생각되나, 향후 장기적인 추적관찰이 필요할 것으로 생각된다.

• 한국산업융합학회 논문집
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• 제16권2호
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• pp.29-33
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• 2013

This study has been conducted to propose an optimal design guidance of underfloor air distribution system by examining air pattern and proper exhaust status of floor plenum using CFD (Computational Fluid Dynamics). Simulation shows deficient air pattern and exhaust status at BPG (Bypass Grille) of the current design. As a means to find an alternative design, four cases have been developed and tested. Case 1, 2 and 3 show similar results in comparison to the current design. However, case 4 shows improved air pattern and exhaust status at BPG(Bypass Grille), and has been chosen as the optimal alternative.

• 한국정밀공학회지
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• 제26권3호
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• pp.73-80
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• 2009

In accordance with the trend for high-speed multi-axes, and the increasing technical sophistication of machine tools, thermal deformation has become an important factor in the accuracy of machine tools. It was analyzed that thermal deformation error accounts for about 70% of all errors made with machine tools. For precise temperature control, both cooling and heating should be implemented. A hot gas bypass type cooling cycle method has a simplified structure and temperature control accuracy to with in ${\pm}0.1^{\circ}C$. In this study, the performances of oil cooler system, including temperature controllability according to hot gas floe and preset temperature sustainability according to temperature load, were tested. It is expected that this study will contribute to the development and performances of oil cooler system, which could minimize thermal errors and improve the quality of precision machine tools.

• Journal of Chest Surgery
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• 제33권5호
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• pp.385-390
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• 2000

Background: To review the experience that used both ventricular assist device(VAD) and extracorporeal membrane oxygenation(ECMO) for children with congential heart disease requiring postcardiotomy mechanical circulatory support. Material and Method: Between March 1993 and May 1995, we applied mechanical assist device using centrifugal pump to the 16 patients who failed to be weaned from cardiopulmonary bypass(n=15) or had been in cardiogenic shock in intensive care unit(n=1). The diagnosis were all congenital heart diseases and the ages of patients ranged from 20 days to 10 years (mean age=2.5$\pm$3.5 years). Result: The methods of mechanical circulatory support were LVAD(n=13), BVAD (n=1), and ECMO(n=2). The mean assist times were 54.0$\pm$23.7 hours. Post-assist complications were in orders: bleeding, acute renal failure, ventricular failure, respiratory failure, infection, and neurologic complication. It was possible for 9 patients(56.3%) to be weaned from assist device and 5 patients(31.3%) were discharged from hospital. There was no statistical significant between hospital discharged group and undischarged group by age, body weight, cardiopulmonary bypass time, and assist time. Conclusion: The ventricular assist device is an effective modality in salvaging the patient who failed to be weaned from cardiopulmonary bypass, but multiple factors must be considered for improving the results of mechanical circulatory support ; such as patient selection, optimal time of starting the assist device, and prevention and management of the complications.

• International Journal of Aeronautical and Space Sciences
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• 제15권1호
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• pp.97-101
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• 2014

With the increase in global air travel, aircraft noise has become a major public issue. In modern aircraft engines, only a small proportion of the air that passes through the whole engine actually goes through the core of the engine, the rest passes around it down the bypass duct. A successful method of reducing noise further, even in ultra-high bypass ratio engines, is to absorb the sound created within the engine. Acoustically absorbent material or acoustic liners have desirable acoustic attenuation properties and thus are commonly used to reduce noise in jet engines. The liners typically are placed upstream and downstream of the rotors (fans) to absorb sound before it propagates out of the inlet and exhaust ducts. Noise attenuation can be dramatically improved by increasing the area over which a noise reducing material is applied and by placing the material closer to the noise source. In this paper we will briefly discuss acoustic liner applications in modern turbofan engines.

• Journal of Chest Surgery
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• 제32권10호
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• pp.891-896
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• 1999

Increasing interest in the use of arterial conduites is based on the better patency of the internal thoracic artery(ITA) than the saphenous vein graft and the hope that other arterial conuits will perform similarly over the long term. Material and Method: Between May 1997 and July 1998, 43 patients underwent coronary artery bypass grafting with ITA and the radial artery(RA). There were 28 men and 15 women with a mean age of 61.5 years(range, 35 to 78). In 43 patents, 30 bilateral ITA(including 7 diabetes mellitus, 5 more older 70 years), 8 bilateral ITA only, 2 left ITA and both RA, 11 left ITA and left RA and 22 both ITA and left RA were used. Result: There was 1 hospital mortality. Of the 42 patients alive, 39 patients are asymptomatic. Postoperative complications were postoperative bleeding in 1 patients, and low cardiac output syndrome in 3. Follow-up angiography was performed in 5 patients after the operation(mean 3 months), and all ITA & RA grafts showed excellent results. Conclusion: We conclude that complete arterial revascularization with internal thoracic artery and radial artery is technically feasiale with low mortality and morbidity, and but long term follow-up is needed.