• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.9
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• pp.821-826
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• 2016

The leak before break (LBB) concept is used in pipe line design for nuclear power plants. For application of the LBB concept, leak rates through cracks should be evaluated accurately. Usually leak late analyses are performed for through-thickness cracks with constant cross-sectional area. However, the cross-sectional area at the inner pipe surface of a crack can be different from that at the outer surface. In this paper, leak rate analyses are performed for the cracks with linearly-varying cross-sectional areas. The effect of varying the cross-sectional area on leak rates was examined. Leak rates were also evaluated for cracks in bi-material pipes. Finally, the effects of crack surface morphology parameters on leak rates were examined.

• Journal of Korean Neurosurgical Society
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• v.64 no.5
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• pp.799-807
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• 2021

Objective : Cerebrospinal fluid leakage related complications (CLC) occasionally occur after intradural spinal surgery. We sought to investigate the effectiveness of early ambulation after intradural spinal surgery and analyze the risk factors for CLC. Methods : For this retrospective cohort study, we enrolled 314 patients who underwent intradural spinal surgery at a single institution. The early group contained 79 patients who started ambulation after 1 day of bedrest without position restrictions, while the late group consisted of 235 patients who started ambulation after at least 3 days of bed rest and were limited to the prone position after surgery. In the early group, Prolene 6-0 was used as the dura suture material, while black silk 5-0 was used as the dura suture material in the late group. Results : The overall incidence rate of CLC was 10.8%. Significant differences between the early and late groups were identified in the rate of CLC (2.5% vs. 13.6%), surgical repair required (1.3% vs. 7.7%), and length of hospital stay (2.99 vs. 9.29 days) (p<0.05). Logistic regression analysis revealed that CLC was associated with practices specific to the late group (p=0.011) and the revision surgery (p=0.022). Conclusion : Using Prolene 6-0 as a dura suture material for intradural spinal surgery resulted in lower CLC rates compared to black silk 5-0 sutures despite a shorter bed rest period. Our findings revealed that suture - needle ratio related to dura defect was the most critical factor for CLC. One-day ambulation after primary dura closure using Prolene 6-0 sutures appears to be a costeffective and safe strategy for intradural spinal surgery.

• Journal of the Semiconductor & Display Technology
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• v.5 no.2 s.15
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• pp.33-36
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• 2006

Many issues arose to use the Pb-free solder as adhesive materials in MEMS ICs and packaging. Then this study for easy and simple sealing method using adhesive materials was carried out to maintain hermetic characteristic in MEMS Package. In this study, Hermetic characteristic using negative PR (XP SU-8 3050 NO-2) as adhesive at the interface of Si test coupon/glass substrate and Si test coupon/LTCC substrate was examined. For experiment, the dispenser pressure was 4 MPa and the $200\;{\mu}m{\Phi}$ syringe nozzle was used. 3.0 mm/sec as speed of dispensing and 0.13 mm as the gap between Si test coupon and nozzle was selected to machine condition. 1 min at $65^{\circ}C$ and 15 min at $95^{\circ}C$ as Soft bake, $200\;mj/cm^2$ expose in 365 nm wavelength as UV expose, 1 min at $65^{\circ}C$ and 6 min at $95^{\circ}C$ as Post expose bake, 60 min at $150^{\circ}C$ as hard bake were selected to activation condition of negative PR. Hermetic sealing was achieved at the Si test coupon/ glass substrate and Si test coupon/LTCC substrate. The leak rate of Si test coupon/glass substrate was $5.9{\times}10^{-8}mbar-l/sec$, and there was no effect by adhesive method. The leak rate of Si test coupon/LTCC substrate was $4.9{\times}10^{-8}mbar-l/sec$, and there was no effect by dispensing cycle. Better leak rate value could be achieved to use modified substrate which prevent PR flow, to increase UV expose energy and to use system that controls gap automatically with vision.

• Journal of Chest Surgery
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• v.28 no.1
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• pp.23-30
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• 1995

From January 1985 to December 1992, of 1257 patients who underwent a heart valve replacement 210 [16.8% underwent reoperation on prosthetic heart valves, and 6 of them had a second valve reoperation. The indications for reoperation were structural deterioration [176 cases, 81.5% , prosthetic valve endocarditis [25 cases, 11.6% , paravalvular leak [12 cases, 5.6% , valve thrombosis [2 cases, 0.9% and ascending aortic aneurysm [1 case, 0.4% . Prosthetic valve failure developed most frequently in mitral position [57.9% and prosthetic valve endocarditis and paravalvular leak developed significantly in the aortic valve [40%, 75% [P<0.02 . Mean intervals between the primary valve operation and reoperation were 105.3$\pm$28.4 months in the case of prosthetic valve failure, 61.5$\pm$38.5 months in prosthetic valve endocarditis, 26.8$\pm$31.2 months in paravalvualr leak, and 25.0$\pm$7.0 months in valve thrombosis. In bioprostheses, the intervals were in 102.0$\pm$23.9 months in the aortic valve, and 103.6$\pm$30.8 months in the mitral valve. The overall hospital mortality rate was 7.9% [17/26 : 15% in aortic valve reoperation [6/40 , 6.5% in reoperation on the mitral prostheses [9/135 and 5.7% in multiple valve replacement [2.35 . Low cardiac output syndrome was the most common cause of death [70.6% . Advanced New York Heart Association class [P=0.00298 , explant period [P=0.0031 , aortic cross-clamp time [P=0.0070 , prosthetic valve endocarditis [P=0.0101 , paravalvularr leak [P=0.0096 , and second reoperation [P=0.00036 were the independent risk factors, but age, sex, valve position and multiple valve replacement did not have any influence on operative mortality. Mean follow up period was 38.6$\pm$24.5 months and total patient follow up period was 633.3 patient year. Actuarial survival at 8 year was 97.3$\pm$3.0% and 5 year event-free survival was 80.0$\pm$13.7%. The surgical risk of reoperation on heart valve prostheses in the advanced NYHA class patients is higher, so reoperation before severe hemodynamic impairment occurs is recommended.

• Journal of Chest Surgery
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• v.55 no.4
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• pp.332-337
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• 2022

Since the first lung transplantation in humans was performed in 1963, patient selection, standardized procurement, and surgical techniques have been developed and established for this procedure. However, despite these developments, surgical complications continue to be important factors influencing patient morbidity and mortality, and efforts should be made to decrease morbidity and improve survival rates by understanding, rapidly detecting, and appropriately treating surgical complications.

• Journal of Chest Surgery
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• v.24 no.11
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• pp.1090-1097
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• 1991

Between January 1981 and January 1991, 554 patients underwent prosthetic valve replacement. A bioprosthetic valve was replaced in 238 cases and mechanical valve 316 cases. Thirty-eight patients underwent 40 reoperations for repair or replacement, an average of 53.6 months after initial implantation. There were 21 women and 19 men, aged 12 to 60 years[mean 35.3]. A bioprosthetic valve was implanted in 31 cases and a mechanical valve in 9 cases for initial operation. Indications for reoperation were primary tissue failure in 23 cases[57.5%], endocarditis in 9[22.5%], periprosthetic leak in 4[10%]. and valve thrombosis in 4[10%]. Operations performed included 5 aortic valve replacements, 26 mitral valve replacement, 8 double valve replacements, and 1 thrombectomy. A mechanical valve was replaced in 33 cases[84.6%] and a bioprosthesis in 6[15.4Zo] for reoperation. A second reoperation was required in 2 patients. Surgical mortality was 10% . Among the 34 early survivors followed-up for an average of 19.8 months. there was 1 late death and 3 were lost to follow-up. Among the 30 late survivors being followed up, 28[93.3%] remained in New York Heart Association Class I or II and two in Class III [6.7%].

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.309-312
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• 2004

임베디드 시스템은 특별한 목적을 수행하기 위해 컴퓨터 하드웨어와 소프트웨어를 결합시킨 것이다. 임베디드 시스템은 일반 데스크탑보다 작은 규모의 하드웨어에서 운영된다. 임베디드 시스템은 파워, 공간, 메모리 등의 여러 가지 환경적 요소에 제약을 받는다. 그리고 임베디드 시스템은 실시간으로 동작하기 때문에 임베디드 시스템에서 소프트웨어의 실패는 일반 데스크탑에서보다 훨씬 심각한 문제를 발생시킨다. 따라서 임베디드 시스템은 주어진 자원을 효율적으로 사용하여야 하고 임베디드 시스템의 실패율을 낮춰야만 한다. 치명적인 문제를 발생시킬 수 있는 임베디드 시스템의 실패의 원인 중 하나가 메모리에 관련한 문제이다. 임베디드 시스템 특정상 메모리 문제는 크게 하드웨어 기반의 메모리 문제와 소프트웨어 기반의 메모리 문제로 분류된다. 소프트웨어 기반의 메모리에 관련한 문제는 Memory Leak, Freeing Free Memory, Freeing Unallocated Memory, Memory Allocation Failed, Late Detect Array Bounds Write, Late Detect Freed Memory Write 등과 같은 것들이 있다. 본 논문에서는 임베디드 시스템의 메모리 관련에 대한 문제점을 파악하고 관련 툴을 연구하여 그 문제점들을 효율적으로 해결할 수 있는 기법을 점증적으로 연구하고자 한다.

• Journal of Chest Surgery
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• v.25 no.3
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• pp.296-306
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• 1992

A 6 year experience with the bileaflet St. Jude Medical valve is reported. Between Feb. 1986 and Dec. 1992, 68 patients received 87 such valves[36 mitral, 13 aortic, and 19 double mitral-aortic valve replacements]. The results are summarized as follows 1. There were 35 male and 33 female patients ranging in age from 17 to 55 years the mean age of 35.3 $\pm$ 9.7 years. 2. The mean aortic clamp time[ACT] of the MVR, AVR and DVR groups were 91.5$\pm$16.4, 117.2$\pm$28.7 and 165.5$\pm$24.1 minutes. The mean total bypass time [TBT] of the MVR, AVR and DVR groups were 112.8$\pm$19.5, 134.7$\pm$31.4 and 192.2$\pm$28.5 minutes. 3. Eighty seven valves were used [55 mitral site, 32 aortic site]. 31mm[20], 33mm[15], 29mm[15], 27mm[2], 25mm[2] and 35mm[1] were used in mitral site and 23mm[13], 21mm[8], 19mm[7] and 25mm[4] were used in the aortic site. In the DVR, there were valve combinations such as 4 cases of M[29mm]-A[19mm], 4 of M[31mm]-A[23mm], 3 of M[33mm]-A[23mm] and others. 4. Preoperative NYHA functional classes were II [3 cases], III [46 cases], IV[19 cases] and improved to I [52 cases] and Il [13 cases] postoperatively. 5 Early postoperative complications were occurred in 15 cases[2Z.l%] and there were LOS in 5 cases[7.4%], arrythmia [3 cases], wound infection [2 cases], hepatitis [2 cases], sudden cardiac arrest [2 cases] and postoperative bleeding [1 case]. The early hospital death was occurred in 3 cases[4.4%] with LOS [1 case] and sudden cardiac arrest [2 cases]. 6. Mean follow-up time of survival cases[65 cases] was 31.3$\pm$21.9 months and the total follow-up time was 169.8 patient-years. Late postoperative complications were occurred in 4 cases[2 thromboembolism, 1 paravalvular leak, 1 thromboembolism br paravalvular leak, 1 valve endocarditis] with the occurrence rate as 2.35% per patient-years. Reoperation was performed in 2 cases [1 paravalvular leak, 1 left atrial thrombus] and there was one [1.5%] late valve related death. Therefore the 6 year complication free rate was 90.6% and 6 year actuarial survival rate was 98.3$\pm$1.7%. On the basis of this experience and the results, SJMvalve appears to be one of the best performing mechanical prosthesis currently available, in terms of both hemodynamics and lower complications with warfarin antioagulation.

• Journal of Chest Surgery
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• v.28 no.7
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• pp.666-670
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• 1995

A total of and consecutive 87 patients underwent concomitant double mitral and aortic valve replacement with the St. Jude Medical prosthesis between January 1985 and December 1993. They were 44 males and 43 females with the ages ranging from 18 to 59 years[mean$\pm$SD: 40.9$\pm$9.5 years . Fifteen patients[17.2% had a history of previous cardiac valve replacement. There were 2 early deaths[2.3% , and 85 early survivors were followed up for a total of 352.6 patient-years[mean$\pm$SD: 4.1 $\pm$2.6 years . All were anticoagulated with coumadin keeping the target international normalized ratio within the range of 1.5 and 2.5. There was a single late death[late mortality of 0.284%/patient-year . Thromboembolism was the most frequent complication[1.985%/patient-year , and bleeding related to anticoagulation was experienced in one patient [0.284%/patient-year . The incidences of prosthetic valve endocarditis and of paravalvular leak were also low[0.284%/patient-year, respectively . The survival including operative mortality was 96.1%$\pm$2.2% at 10 years. The actuarial probabilities of freedom from thromboembolism and from all events were 77.9%$\pm$11.1% and 72.4%$\pm$10.7%, respectively, at 10 years. There was no structural failure of the prosthesis. Results from a series of clinical studies suggest strongly that the use of lower intensity of anticoagulation therapy lowers the thromboembolic as well as bleeding rates in patients with the ST. Jude Medical prosthesis.

• Journal of Chest Surgery
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• v.25 no.10
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• pp.1041-1047
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• 1992

The consecutive 35 patients underwent isolated aortic valve replacement with the low-profile model of the Ionescu-Shiley pericardial xenograft valve from 1984 to 1991. Operative mortality was 2.9%, and early survivors were followed up for a total 136.1 patient-years[Mean$\pm$SD, 4.00$\pm$2.14 years]. The linearized late mortality was 2.204% /pt-yr. Three patients required rereplacement of the valve with overall valve failure rate of 2.204% /pt-yr: two for endocarditis and one for paravalvular leak. There was no case of primary tissue failure. The linearized annual rates of complication were: thromboembolism 0.735% /pt-yr, bleeding 0.735%pt-yr, and endocarditis 2.204% /pt-yr. The actuarial survival at 8 years of follow-up was 90.4$\pm$5.3%, and the probabilities of freedom from thromboembolism and from rereplacement were 95.6$\pm$4.4% and 88.2$\pm$6.7% at 8 years respectively. Although the low profile Ionescu-Shiley pericardial valve provided favorable clinical performance comparable with the standard model up to 8 years, it needs prolonged follow-up to assess the pattern of its durability.