• Bulletin of the Korean Chemical Society
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• 제24권2호
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• pp.178-182
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• 2003

The stress and the heat-flux auto-correlation functions in the Green-Kubo formulas for shear viscosity and thermal conductivity have non-decaying long-time tails. This problem can be overcome by improving the statistical accuracy by N (number of particles) times, considering the stress and the heat-flux of the system as properties of each particle. The mean square stress and the heat-flux displacements in the Einstein formulas for shear viscosity and thermal conductivity are non linear functions of time since the quantities in the mean square stress and the heat-flux displacements are not continuous under periodic boundary conditions. An alternative to these quantities is to integrate the stress and the heat-flux with respect to time, but the resulting mean square stress and heat-flux displacements are still not linear versus time. This problem can be also overcome by improving the statistical accuracy. The results for transport coefficients of liquid argon obtained are discussed.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.244-250
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• 1997

The mean time to failure (MTTF) expressing the mean value of the system life is a measure of system effectiveness. To estimate the remaining life of component and/or system, the dynamic mean time to failure concept is suggested. It is the time-dependent Property depending on the status of components. The Kalman filter is used to estimate the reliability of components using the on-line information (directly measured sensor output or device-specific diagnostics in the intelligent sensor) in form of the numerical value (state factor). This factor considers the persistency of the fault condition and confidence level in measurement. If there is a complex system with many components, each calculated reliability's or components are combined, which results in the dynamic MTTF or system. The illustrative examples are discussed. The results show that the dynamic MTTF can well express the component and system failure behaviour whether any kinds of failure are occurred or not.

• 전자공학회논문지B
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• 제33B권7호
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• pp.11-20
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• 1996

In this paper, the performance of the IeEE 802.4 token-passing is analyzed under the assumption that all nodes have finite buffers and finite THT (token tolding time). The loads generated at nodes are assumed to be asymmetric. The priority mechanism is not considered. This paper derives an approximate matrix equation of the queue length distributin in terms of the number of nodes, frame arrival rate and mean service time of a frame in steady state. Based on the matrix equation, the mean token rotation time, the mean waiting time and the blocking probability are derived analytically. the analytic results are compared with simulation results in order to show that the deviations are small.

• International Journal of Reliability and Applications
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• 제2권4호
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• pp.241-251
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• 2001

In this paper, optimal bum-in time to minimize the total mean cost, which is the sum of manufacturing cost with burn-in and cumulative warranty-related cost, is obtained. When the products with cumulative pro-rata warranty have high failure rate in the early period (infant mortality period), a burn-in procedure is adopted to eliminate early product failures. After burn-in, the posterior product life distribution and the warranty-related cost are dependent on burn-in time; long burn-in period may reduce the warranty-related cost, but it increases the manufacturing cost. The paper provides a methodology to obtain total mean cost under burn-in and cumulative pro-rata warranty. Property of the optimal burn-in time is analyzed, and numerical examples and sensitivity analysis are studied.

• 한국국방경영분석학회지
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• 제12권2호
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• pp.68-81
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• 1986

This thesis studies the estimation from interarrival and service time data of the mean number of customers in service at time t for an $M/G/{\infty}$ queue. The assumption is that the parametric form of the service time distribution is unknown and the empirical distribution of twe service time is used in the estimate the mean number of customers in service. In the case in which the customer arrival rate is known the distribution of the estimate is derived and an approximate normal confidence interval procedure is suggested. The use of the nonparametric methods, which are the jackknife and the bootstrap, to estimate variability and construct confidence intervals for the estimate is also studied both analytically and by simulation.

• 대한종양외과학회지
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• 제14권2호
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• pp.95-101
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• 2018

Purpose: The standard treatment of esophageal cancer is the Ivor-Lewis operation, which consists of an abdominal phase involving gastric tube formation, and a chest phase involving esophagectomy and anastomosis. We aimed to report our experience of performing thoracic esophagectomy with the laparoscopic gastric pull up (LGPU) technique and its surgical outcomes. Methods: Clinicopathologic data and short-term surgical outcomes of 14 patients who underwent LGPU for thoracic esophageal cancer from August 2008 to May 2016 were retrospectively reviewed. Results: Mean age of the patients was 62.3 years and mean body mass index was $21.7kg/m^2$. Eleven patients had medical comorbidities. Patients' mean American Society of Anesthesiologists score was 2. Mean operation time was 428.5 minutes, with the mean abdominal operation time being 138.9 minutes. There was no open conversion case. Three patients had pneumonia, three patients had surgical site infection, and one patient had subcutaneous emphysema within 30 days after surgery. One patient had minor anastomosis site leakage. There was one 30-day mortality case. One patient with postoperative aspiration pneumonia developed acute respiratory distress disease, and died due to sepsis. Mean postoperative intensive care unit stay was 3.5 days, and mean postoperative hospital stay was 20.6 days. Nasogastric tubes were removed on average at 3.4 days, and mean oral intake time was 3.4 days. Conclusion: If the gastrointestinal surgeon has extensive experience in laparoscopic procedures, LGPU will be a safe and feasible technique for thoracic esophagectomy in patients with intrathoracic esophageal cancer.

• Journal of Gastric Cancer
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• 제11권4호
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• pp.206-211
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• 2011

Purpose: Laparoscopic total gastrectomy (LTG) for gastric cancer is still uncommon because of technical difficulties, especially in esophagojejunostomy (EJ). There are many reports for various laparoscopic procedures of EJ using linear or circular staplers. On the other hands, there has been no report for hand-sewn anastomosis. We report successfully performed intracorporeally hand-sewn EJ after LTG. Materials and Methods: The clinicopathologic data and short-term surgical outcomes of 6 patients who underwent totally laparoscopic total gastrectomy for upper gastric cancer from December 2010 and July 2011 were retrospectively reviewed. Results: The mean age was 66.5 years and mean body mass index (kg/$m^2$) was 24.6. All patients had medical comorbidities. The mean patient ASA score was 2.17. Among the 6 patients, previous abdominal operation was performed for 2 patients and combined operation was performed for 3 patients. The mean blood loss, operation time, and EJ anastomosis time was 130 ml, 379.7 minutes, and 81.5 minutes, respectively. The mean time to first flatus, first oral intake, and postoperative hospital stay was 3.0, 3.0, and 12.5 days, respectively. There was no 30-day mortality case. Postoperative aspiration pneumonia and multiple periventricular lacunar infarctions developed in 1 patient. There were no anastomosis-related complications and other major surgical complications. Conclusions: When the intracorporeal anastomotic technique becomes popular in LTG the intracorporeally hand-sewn EJ may be accepted as one method among the various laparoscopic procedures of EJ.

• 대한족부족관절학회지
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• 제10권1호
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• pp.66-70
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• 2006

Purpose: To analyze the clinical and radiological outcome of subtalar arthrodesis using cannulated screws and morselized bone graft. Materials and Methods: Twenty one patients with follow-up of more than 1 year after subtalar arthrodesis were included in this study. Mean age was 40.8 years, and mean follow-up duration was 38 months. Underlying diseases were 19 cases of posttraumatic arthritis (18 calcaneal fractures and 1 talar fracture) and 2 cases of tarsal coalition. Clinically AOFAS ankle-hindfoot score, operation time, complication and satisfaction of patients were analyzed. Radiologically time to union, arthritis of surrounding joints, preoperative and postoperative talar declination angle were analyzed. Results: AOFAS ankle-hindfoot score was improved from preoperative 33 points to postooperative 79 points. Eighteen patients (86%) were satisfied with the results. Mean operation time was 91 minutes. All cases were fixed with 1-2 cannulated screws and morselized bone graft. Mean time to radiologic union was 12.1 weeks. There was 1 case of delayed union. There was no significant perioperative changes in talar declination angles. Conclusion: Subtalar arthrodesis using cannulated screws and morselized bone graft seems to be relatively simple and effective treatment method for subtalar arthritis.

• 한국음향학회지
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• 제21권1호
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• pp.37-41
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• 2002

본 논문에서는 실내 잔향곡선의 초기감쇠시간을 복수 채널을 사용하여 단축시켰다. 실내에서 수음된 음성신호는 MINT(Multiple - input / output INverse Theorem)에 기초하여 풀밴드와 서브밴드로 역필터링하였으며, 복수 채널의 적응필터는 LMS(least Mean Square)와 NLMS(Normalized Least Mean Square) 알고리즘을 사용하였다. 실험결과 잔향곡선에서 -20 dB까지 감소하는데 걸리는 시간이 2개의 마이크로폰을 사용하였을 때 풀밴드 NLMS에서 약 1/3로 단축됨을 확인하였다. 실제 음장의 전달함수를 사용한 주관평가에서는 80%의 청취자가 MINT에 의해 초기감쇠시간이 단축된 음성의 명료도가 향상되었다고 평가하였다.

• Wind and Structures
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• 제30권5호
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• pp.475-483
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• 2020

This work investigates Reynolds number Re (= 50 - 200) effects on the flows around a single cylinder and the two tandem (center-to-center spacing L^⁎= L/D = 4) cylinders, each of a diameter D. Vorticity structures, Strouhal numbers, and time-mean and fluctuating forces are presented and discussed. For the single cylinder, with increasing Re in the range examined, the vorticity magnitude, Strouhal number and fluctuating lift all monotonically rise but time-mean drag, vortex formation length, and lateral distance between the two rows of vortices all shrink. For the two tandem cylinders, the increase in Re leads to the formation of three distinct flows, namely reattachment flow (50 ≤ Re ≤ 75), transition flow (75 < Re < 100), and coshedding flow (100 ≤ Re ≤ 200). The reattachment flow at Re = 50 is steady. When Re is increased from 75 to 200, the Strouhal number of the two cylinders, jumping from 0.113 to 0.15 in the transition flow regime, swells to 0.188. The two-cylinder flow is more sensitive to Re than the single cylinder flow. Fluctuating lift is greater for the downstream cylinder than the upstream cylinder while time-mean drag is higher for the upstream cylinder than for the other. The time-mean drags of the upstream cylinder and single cylinder behaves similar to each other, both declining with increasing Re.