• Journal of Chest Surgery
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• 제46권2호
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• pp.93-97
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• 2013

Background: Minimally invasive cardiac surgery has emerged as an alternative to conventional open surgery. This report reviews our experience with atrial septal defect using the da VinciTM surgical robot system. Materials and Methods: This retrospective study included 50 consecutive patients who underwent atrial septal defect repair using the da VinciTM surgical robot system between October 2007 and May 2011. Among these, 13 patients (26%) were approached through a totally endoscopic approach and the others by mini-thoracotomy. Nineteen patients had concomitant procedures including tricuspid annuloplasty (n=10), mitral valvuloplasty (n=9), and maze procedure (n=4). The mean follow-up duration was $16.9{\pm}10.4$ months. Results: No remnant interatrial shunt was detected by intraoperative or postoperative echocardiography. The atrial septal defects were mainly repaired by Gore-Tex patch closure (80%). There was no operative mortality or serious surgical complications. The aortic cross clamping time and cardiopulmonary bypass time were $74.1{\pm}32.2$ and $157.6{\pm}49.7$ minutes, respectively. The postoperative hospital stay was $5.5{\pm}3.3$ days. Conclusion: The atrial septal defect repair with concomitant procedures like mitral valve repair or tricuspid valve repair using the da VinciTM system is a feasible method. In addition, in selected patients, complete port access can be helpful for better cosmetic results and less musculoskeletal injury.

• Journal of Chest Surgery
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• 제46권3호
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• pp.185-191
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• 2013

Background: Cardiopulmonary bypass (CPB) induces variable systemic inflammatory reactions associated with major organ dysfunction via polymorphonuclear neutrophils (PMNs). Ulinastatin, a urinary trypsin inhibitor, inhibits PMN activity and reduces systemic inflammatory responses. The aim of this study is to evaluate the effect of ulinastatin on postoperative blood loss and laboratory changes in patients undergoing open heart surgery. Materials and Methods: Between January 2008 and February 2009, 110 patients who underwent atrioventricular valve surgery through right thoracotomy were divided into two groups. Patients received either 5,000 U/kg ulinastatin (ulinastatin group, n=41) or the equivalent volume of normal saline (control group, n=69) before aortic cross clamping. The primary end points were early coagulation profile changes, postoperative blood loss, transfusion requirements, and duration of intubation and intensive care unit stay. Results: There were no statistically significant differences between the two groups in early coagulation profile, other perioperative laboratory data, and postoperative blood loss with transfusion requirements. Conclusion: Administration of ulinastatin during operation did not improve the early coagulation profile, postoperative blood loss, or transfusion requirements of patients undergoing open heart surgery. In addition, no significant effect of ulinastatin was observed in major organs dysfunction, systemic inflammatory reactions, or other postoperative profiles.

• Safety and Health at Work
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• 제13권3호
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• pp.364-371
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• 2022

Background: Respiratory masks can provide healthcare workers with protection from biological hazards when they have good performance. There is a direct relationship between the visual specifications of a mask and its efficacy; thus, the aim of this study was to develop tools for qualitative assessment of the performance of masks used by healthcare workers. Methods: A mixed-methods design was used to develop a qualitative assessment tool for medical face masks (MFM) and particle filtering half masks (PFHM). The development of domains and items was undertaken using observation and interviews, the opinions of an expert panel, and a review of texts and international standards. The second phase evaluated the psychometric properties of tools. Finally, the validated Mask Qualitative Assessment Tools (MQAT) were used to assess six samples from 10 brands of the two types of masks. Results: MQAT-MFM and MQAT-PHFM shared 42 items across seven domains: "cleanliness," "design," "marking, labeling and packaging," "mask layers," "mask strap," "materials and construction," and "nose clip." MQAT-MFM included one additional item. MQAT-PHFM included another nine items associated with an eighth "Practical Performance" domain, and the valve version had another additional "Exhalation Valve" domain and six items. The evaluation indicated 80% compliance for MFM and 71% compliance for PFHM. "Marking, labeling and packaging" and "Layers" were associated with the least compliance in both types of masks and should be checked carefully for defining mask quality. Conclusion: MQAT can be used for immediate screening and initial assessment of MFM and PHFM through appearance, simple tools, and visual inspection.

• 열처리공학회지
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• 제13권4호
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• pp.246-252
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• 2000

Stellite 12 alloy-powder was overlaid on 410 stainless steel valve seat using plasma transferred arc(PTA) process. Variation of characteristic of microstructure and hardness of deposit with current(90~150 A) and preheat temperature(R.T.~$400^{\circ}C$) was investigated. Important conclusion obtained are as follows; All welding conditions used produced a sound deposit layer with no defect in single pass welding. The maximum deposit had 4.0~4.8 mm in thickness and its bead width was increased with increase of current and preheat temperature. The deposit showed hypoeutectic microstruture, which was consisting of primary cobalt dendrite and networked $M_7C_3$ type eutectic carbides. The amount of eutectic carbides was decreased and its dendritic secondary arm spacing was increased with increase of current. Hardness of the deposit was decreased with increase of current. Preheat temperature up to $400^{\circ}C$, however, showed little influence on the hardness and microstructure. The hardness was also influenced by diluted Fe content near the interface in addition to microstructure and dendritic secondary arm spacing. Hot hardness at $500^{\circ}C$ showed higher than 300 HV.

• 한국가스학회지
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• 제20권4호
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• pp.1-6
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• 2016

버스와 같은 대형 차량에서 사용되는 대형 CNG 엔진에는 가스 연료 분사를 위한 인젝터가 6개 가량의 단위로 모듈 형태를 구성하고 있다. 이러한 인젝터 모듈은 연료 공급을 위한 입출구가 각각 한 곳으로 구성되어 있으며 쓰로틀 후단을 통하여 흡기관으로 연료를 공급하는 방식이므로 과도 운전에 대한 응답성이 매우 낮은 구조를 형성하고 있다. 본 연구에서는 이러한 인젝터 모듈의 내부 유로에 대한 유동 해석을 통하여 응답성을 개선할 수 있는 방안을 제시하고자 한다. 결론에 따르면 내부 유로의 체적을 감소시킴으로써 가스 연료의 공급 응답성을 개선할 수 있었고, 각각의 인젝터에서 모듈의 출구까지의 거리를 동일하게 하는 방안도 응답성과 연료 공급량의 선형성을 확보할 수 있는 것을 확인하였다. 다만 각 인젝터의 분사 순서 시기에는 큰 영향을 받지 않는 결과를 보였다.

• 한국자기학회지
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• 제18권6호
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• pp.227-231
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• 2008

Zr 함량에 따르는 CoFeZr의 합금박막의 구조 및 자기적 특성, 그리고 비정질 CoFeZr을 사용한 스핀밸브의 자기저항 및 열적 안정성에 관하여 연구하였다. Zr 조성이 증가함에 따라 CoFeZr 합금 박막의 포화자기장 및 보자력은 감소하며 완전히 비정질이 형성되었을때 보자력은 최소 값을 보였다. Zr의 함량이 약 18 at% 이상일 때 완전한 비정질이 형성되었다. 비정질 CoFeZr을 스핀밸브에 적용하였을 때 기존의 CoFe을 사용한 스핀밸브보다 자기저항비와 교환결합력은 약간 감소하는 경향을 확인 하였다. 이는 비정질 자성체의 상대적으로 높은 저항값에 기인하였다. 그러나 ${\Delta}{\rho}$, 즉 스핀의존산란은 향상되었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1087-1090
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• 2005

In precision machinery systems for medical and chemical applications, micropumps with a low pulsation have been demanded and investigated for accurate delivery of a small amount of liquid. This study proposes sheet type check valves instead of ball type check valves for PZT pumps and performs some tests on dynamics characteristics of check valves having different design parameter with variable frequency. The selected materials of check valves is NBR, PP film, Polyimide and Stainless steel(SUS304). In the experiment, dynamic characteristics of stainless steel thin plate have better performance than others.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.765-768
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• 2002

This study focuses on designing a new gluing system for the FM-I (Freeform Master I), which is a new rapid prototyping machine using a sheet lamination technique. To design the system, we firstly verify the required parameters of the proposed gluing system. Then we analyze the electro-magnetic system by using ANSYS and the mechanical system by using numerical methods. The gluing system can contribute to reduce the cost of the machine since it can be applied to low cost materials such as a plain paper.

• 소성∙가공
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• 제11권3호
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• pp.246-254
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• 2002

A simple method to derive an optimal pressure curve, characterized by initial pressure, final pressure and pressure path, has been proposed. The initial pressure has been determined from the condition to prevent recoiling phenomenon in the early stage, while the final pressure is from the FE analysis and pressure path is from the punch penetration volume. In order to realize the pressure curve, an open loop control system based on a proportional relief valve has been developed for the renovated CNC hydroforming press. Through the comparison of experiment and analysis, the predicted pressure curve has been verified optimal curve since no defect has been observed.

• 기계와재료
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• 제21권3호
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• pp.42-51
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• 2009

원자력/화력 발전소에서 사용중인 터빈출력제어장치(turbine power control device)는 유압 서보액추에이터(hydraulic servo actuator)로 구동하는 특수 스팀 밸브(steam valve)로서 터빈의 속도를 제어하고 스팀을 차단하는 기능이 있다. 대형 발전기(500~1000Mw)를 구동하여 양질의 전기를 생산하기 위해서는 발전기에 연결된 고압 및 저압터빈에 최적량의 스팀을 공급하여야 하고, 고속(화력 3600 rpm, 원자력 1800 rpm)으로 회전하는 터빈이나 스팀계통에 이상이 발생할 경우 터빈의 과속(over speed) 방지를 위하여, 즉시 터빈으로 공급되는 스팀을 차단하여 터빈을 보호해야 한다. 따라서 터빈의 속도제어와 계통의 스팀 량을 감시하여 차단하는 발전소의 특수 밸브의 신뢰성확보기술이 요구된다. 특히 원자력발전소의 경우 핵연료교환주기(약 24개월)에 밸브들을 정비 또는 교체하고 있어 이때마다 시스템과 매칭(튜닝)기술이 요구되었다. 본 연구에서는 전량 수입에 의존했던 원자력/화력 발전소의 특수 밸브인 터빈출력제어장치의 국산화 개발과 신뢰성확보기술 효과에 대하여 논하였다.