• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.451-452
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• 2014

본 논문에서는 단상 계통연계형 컨버터의 전원 위상각을 추종함에 있어 필수적인 전압 센서의 옵셋 오차에 대한 영향을 분석하고 이를 검출 및 보상하기 위한 알고리즘을 제안하였다. 전원전압 측정에 따른 옵셋 오차는 전원 주파수의 1배 맥동을 야기하여 전원 위상각이 왜곡된다. 왜곡된 전원 위상각에 의한 좌표변환시 동기 좌표계 dq축 전류에 전원 주파수 1배의 맥동을 야기하며 이는 계통측 상전류에 직류성분과 전원 주파수 2배의 고조파 성분을 발생시키게 된다. 따라서, 본 논문에서는 전원측정시 야기되는 옵셋 오차의 영향을 분석하고 이의 검출신호로 전원 위상각 제어기의 적분출력을 선정하였다. 또한 RMS(Root Mean Square) 기법을 이용하여 옵셋 성분을 검출 및 보상하는 알고리즘을 제안하였다. 제안된 알고리즘의 성능은 시뮬레이션과 실험을 통하여 검증하였다.

• Journal of Chest Surgery
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• v.31 no.3
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• pp.304-307
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• 1998

Aneurysm of the sinus of Valsalva on mostly congenital disease that develops more frequently in Orientals, is very low in incidence. In most cases, aneurysm of the sinus of Valsalva extends to intracardiac and results in ruptures into the right ventricle or atrium. The likelihood of extracardiac aneurysm of the sinus of Valsalva is very low. Cases of extracardiac aneurysm are usually accompanied by aortic regurgitation and can cause right ventricle outflow tract obstruction, myocardial ischemia, and myocardial infarction due to compression by aneurysm. Since the aneurysm can rupture in the intrapericardium and cause cardiogenic shock or sudden death, definite diagnosis and management are important. If confirmed, it is preferable operform a surgical correction. We report here, with a literature review, a case where myocardial ischemia and aortic egurgitation caused by aneurysm developed in the left coronary and noncoronary sinus, and were surgically corrected with satisfactory esults.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.1
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• pp.64-72
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• 1997

An analytical study has been performed to investigate the unsteady ignition characteristics of pulse combustion. In many combustion applications, strain rate of the flow can significantly affect the combustion features; ignition, extinction, and reignition. In the pulse combustion, two jets (hot combustion gases and fresh mixtures) coming from the opposite side of the combustor will collide in the combustor forming a stagnation region where the chemical reaction is suppressed by the strain rate until this becomes below the critical value. In this research, the method of large activation energy asymptotic is adopted with one step irreversible kinetics to examine the ignition response to the periodic variation of the strain rate of flow. The results show the variation of the maximum value of strain rate can determine whether the ignition or extinction occur.

• Journal of Chest Surgery
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• v.42 no.1
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• pp.96-99
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• 2009

We report here on a case of a ruptured sinus of a valsalva aneurysm into the left ventricle with the rupture site communicating with both the left coronary sinus and the noncoronary sinus in a 37-year-old male who presented with symptoms of congestive heart failure. Echocardiography showed a sac-like structure around the sinus of valsalva, an enlarged left ventricle (LV) and severe aortic regurgitation, which all suggested a ruptured sinus of a valsalva aneurysm or an aortic-left ventricular tunnel. The operative findings revealed that both the left coronary sinus and the noncoronary sinus had an opening into the left ventricle. The proximal opening into the LV was closed with bovine pericardium and the aortic root was replaced with a composite graft (a 21 mm St. Jude Epic Supra tissue valve and a 24 mm Hemashild graft) by the modified Bentall procedure. The patient was discharged on the 15th postoperative day, and he was regularly followed up for 2 months. We report on this case due to its rarity and to describe the surgical repair techniques.

• Journal of Chest Surgery
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• v.30 no.7
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• pp.719-723
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• 1997

We experienced a case of aneurysm of the sinus of Valsalva dissecting into the ventricular dseptum. This dissection was induced by paravalvular leakage after aortic and mitral valve replacement. This 37-year-old male was admitted via emergence room due to progressive dyspnea. He had undergone aortic valve replacement(carbomed c" 23 mm) and mitral valve replacement(carbomedic 31 mm) due to aortic regurgitation and mitral regurgitation about 6 years prior to admission and followed up regularly. The diagnosis was made by transthoracic and transesophageal echocardiography and reconfirmed by root aortography. The inlet of the ventricular septal aneurysmal sac was repaired by one layer suture with 3-0 prolene of the endocardium, epicardium and homograft muscle shoulder altogether. Postoperative course was uneventful and the patient was discharged on the 11th postoperative day. day.

• Journal of Chest Surgery
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• v.32 no.7
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• pp.665-667
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• 1999

We report a case of ruptured sinus of Valsalva aneurysm in 48-year-old male, presenting the symptom of congestive heart failure. Echocardiography showing a hairpin-like sac ex tended from the left coronary sinus to the left ventricle adjacent to the anterior mitral valve leaflet, suggested ruptured sinus of Valsalva aneurysm or aorto-left ventricular tunnel. Operative findings revealed that left sinus of Valsalva aneurysm had multiple openings faced left ventricle, 7 mm in diameter, 20 mm in length. The proximal opening was closed with bovine pericardium and distal openings were closed with spaghetti pledgeted reinforced sutures. The patient was discharged on the 14th postoperative day, and follow up for 8 months uneventfully. This case was reported for its rarity and to describe the techniques of surgical repair.

• Journal of Biomedical Engineering Research
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• v.21 no.6
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• pp.567-573
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• 2000

뇌동맥류는 뇌혈관의 일부가 풍선처럼 부풀어나는 혈관계 질환이며 뇌동맥류의 파열은 사망이나 심각한 후유 장애를 야기한다. 뇌동맥류의 다양한 발생 원인 중 혈관 내부의 혈류의 유동이 중요한 인자로 의심된다. 뇌동맥류의 형성에 미치는 혈류역학적 인자를 규명하기 위해 내경동맥에서 발생한 환자의 내경 동맥류 CT 사진을 이용하여 내경동맥류 모델을 제작하고, 모델 내부의 혈류유동장을 입자영상속도계를 이용하여 측정하였다. 동맥류가 발생한 내경동맥류 모델에서는 동맥류 원위부 목(distal neck)쪽과 반대쪽 내경동맥 벽에서 전단응력이 높게 나타났다. 동맥류 발생에 미치는 혈류역학적 인자를 규명하기 위해 동맥류를 제거한 내경모델을 제작하여 맥동유동에서 내부 유동장을 측정하였다. 심실수축기 동안 휘어진 내경동맥의 바깥쪽 벽에서 혈류의 혈관벽 부딪힘이 관찰되었으며 심실이완기 초반에도 이는 계속 유지되었다. 내경 동맥 내부의 부차적 유동특성을 연구하기 위해 동맥류 발생 위치에서 혈관 축과 수직인 평면의 유동장이 측정되었다. 혈관 단면에서는 휘어진 혈관의 바깥쪽에서 안쪽으로 시계방향의 와류가 형성되었으며, 이로 인해 혈관벽 바깥쪽과 시계방향으로 90도 정도 지역에서 전단응력이 높게 나타났다. 혈류 유동 특성과 동맥류 발생위치를 비교해 보면, 혈류의 혈관벽 부딪힘이 관찰되는 위치와 부차적 유동에 의해 전단응력이 크게 나타난 지역은 동맥류의 발생위치와 일치하였다. 따라서 혈류의 혈관벽 부딪힘과 부차적 유동에 의한 전단력이 동맥류 발생의 혈류역학적 요인으로 의심된다.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.57-62
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• 2009

Unsteady flows in a semi-induction system was investigated to verify their characteristics. A semi-induction system was designed and made to verify the Sow characteristics in an intake system. To attain an intact wave of an intake pulse, a single semi-intake system was adopted as a test rig. The system consists of an intake pipe and a rotary valve as a pulse generator, and a variable volume Helmholtz resonator. The variable volume Helmholtz resonator was mounted in the intake pipe to enhance a breathing capacity and engine performance. The phase and amplitude of the pulsating flow in an unsteady flow system were found to affect the charging capacity significantly. The behavior of pressure wave, their phase and amplitude were investigated in various regions. Some of the results obtained from experiments were described.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.751-756
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• 2000

Based on Experimental analysis, the characteristics of back pressure in automotive exhaust system is tested for 4-stroke gasoline engine. The back pressure in automotive exhaust system is generated by resistance working of exhaust system, i.e. exhaust manifold, pipe length, pipe banding, difference system pressure with atmospheric pressure. This paper contains experimental results which are tested for the change of exhaust pipe length and torque change are tested under experimental conditions.

• Journal of Biomedical Engineering Research
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• v.21 no.5
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• pp.505-512
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• 2000

기계식 인공심장판막을 통한 혈액의 유동과 이 유동에 관련된 판첨의 거동특성을 수치해석기법을 이용하여 연구하였다. 혈액은 맥동류, 층류, 비압축성 유동으로 가정하였으며 유체-고체의 상호작용을 고려하기 위하여 혈액의 유동방정식과 고체의 운동방정식이 동시에 계산되었다. 심실과 대동맥에서의 압력파형을 경계조건으로 사용하였다. 연구의 결과로서 혈액유동과 판첨의 거동이 예측되었으며, 판막을 통한 3개의 제트가 발견되었으며 vortex가 판첨의 끝단에서 발생하여 하부로 흘러가는 것이 관찰되었다. 판첨의 닫힘 거동은 열림 거동에 비하여 2배정도 빠르게 진행되었으며 sinus에서 2개의 큰 vortex가 관찰되었다. 유체-고체 상호작용을 고려하는 본 연구방법은 향후 판막의 연구와 개발에 매우 유용할 것으로 판단된다.