• 시스템엔지니어링학술지
• /
• 제16권2호
• /
• pp.1-15
• /
• 2020

Nuclear power plants in South Korea are operated to cover the baseload demand. Hence they are operated at 100% rated power and do not deploy power tracking control except for startup, shutdown, or during transients. However, as the contribution of renewable energy in the energy mix increases, load follow operation may be needed to cover the imbalance between consumption and production due to the intermittent nature of electricity produced from the conversion of wind or solar energy. Load follow operation may be quite challenging since the operators need to control the axial power distribution and core reactivity while simultaneously conducting the power maneuvering. In this paper, a systems engineering approach for multi-physics load follow simulation of APR1400 is performed. RELAP5/SCDAPSIM/MOD3.4/3DKIN multi-physics package is selected to simulate the Korean Advanced Power Reactor, APR1400, under load follow operation to reflect the impact of feedback signals on the system safety parameters. Furthermore, the systems engineering approach is adopted to identify the requirements, functions, and physical architecture to provide a set of verification and validation activities that guide this project development by linking each requirement to a validation or verification test with predefined success criteria.

• 한국수자원학회논문집
• /
• 제54권6호
• /
• pp.443-452
• /
• 2021

혼합정수 계획의 최적화 기법으로 유도한 '용수 감량 공급 기준'은 용수를 미리 감량 공급함으로써 가뭄 기간에 상대적으로 많은 물을 확보하여 저수지를 운영하는 기준이다. 우리나라의 다목적 저수지 운영에 적용하고 있는 현행 기준은 모의 운영 기법으로 유도된 '용수공급 조정기준'이다. 2003-2018년 기간의 저수지 유입량을 입력 자료로 하여, 합천 다목적댐 저수지의 모의 운영에 두 방법을 적용한 결과, 두 방법 모두 2015년부터 2018년까지 지속된 가뭄에 장기간 물 공급 부족이 발생하였다. 특히 2017년 하반기에 물을 전혀 공급하지 못하거나 간헐적으로 공급하는 기간이 지속해서 나타났다. 용수공급 조정기준은 '정상 용수공급 환원 기준 저수량'을 둠으로써, 2017년 7월에 용수공급 불가 상태에 이른 다음, 저수량이 정상 용수공급 환원 기준 저수량 보다 커지는 2018년 1월까지 용수공급을 중단하는 결과를 낳았다. 저수지에 물이 유입되어 저수량이 증가하는 상태에도 불구하고 물 공급을 중단하는 결과는 실행 상 개선이 필요하다. 현행 용수공급 조정기준과 용수 감량 공급 기준 모두 가뭄 단계별 용수의 감축 공급 개념을 과학적 수치로 나타낸 저수지 운영 기준으로서 유용하고 현실적이다. 그렇지만 위와 같이 몇 개월간 물을 전혀 공급하지 못하거나 간헐적으로 공급하는 저수지 모의 운영 결과를 개선하기 위하여, 현재 적용 중인 가뭄 단계별 물의 공급 축소량을 증가시킬 필요가 있다.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
• /
• pp.303-306
• /
• 2008

The wind power generation systems have a fluctuating or intermittent power output due to the variability of the wind speed. The amount of wind generation which can be connected to the grid without causing voltage stability problems is limited. In this study, the simulation of the wind power generation including energy storage system were performed to reduce the fluctuation of wind power output and to obtain the optimal operation planning of energy storage system.

• 상하수도학회지
• /
• 제25권6호
• /
• pp.959-970
• /
• 2011

The frequent occurrence of sewer flooding and the intermittent discharge of non-point pollutions into the receiving water body are emerging issues recently due to the climate change and urbanization. These problems might be solved by introducing a multifunctional storage facility. Unlike a single-purpose storage facility, a multi-purpose storage facility should be operated at an instant to meet for flood prevention, reduction of non-point pollution and/or rainwater reuse. Considering various operational combinations it is suggested that prevention of sewer flooding coupled with reduction of non-point pollution is the most effective operational strategy for a multi-functional storage facility.

• Journal of Chest Surgery
• /
• 제32권10호
• /
• pp.943-946
• /
• 1999

There was no significant difference in morbidity and mortality between those that received simultaneous operation for coronary artery disease and peripheral vascular disease versus those that received coronary artery bypass graft alone. Simultaneous operation is also cost effective. A 46 year-old patient with resting chest pain and intermittent claudication was diagnosed as unstable angina and Leriche's syndrome. We performed simultaneous revascularization for coronary artery stenosis with internal mammary artery and right gastroepiploic artery and a bifurcated vascular graft interposition between in the aorta, left common iliac and right femoral arteries for Leriche's syndrome. The postoperative coronary angiogram and aortogram revealed a good patency of the arterial conduits and vascular graft. He has been followed for 12 months without any problem.

• 전기학회논문지
• /
• 제63권6호
• /
• pp.834-840
• /
• 2014

When the high speed train (KTX) departs from station in the high-speed line, intermittent on-board signal disappearance causes a hindrance of the operation punctuality. Therefore, we have a research objective to verify the causes of hindrance and to find an improvement plan. process of research, when train leaves the station, we applied sand on the rail to improve adhesive power, that sand has an effect on the ATC(Automatic Train Control) signal wave. We detected & analyzed signal waves which is came from detecting device by changing operation condition in accordance with sand material overage detection to be achieved.

• Journal of Chest Surgery
• /
• 제22권4호
• /
• pp.609-619
• /
• 1989

During aortic valve surgery, cardioplegic solution is delivered through direct cannulation of both coronary ostia. Since this approach may cause an intimal injury leading to acute dissection or late ostial stenosis, this study was undertaken to evaluate myocardial protective effect of retrograde perfusion of cardioplegia [RCSP <% RRAP] in 18 clinical cases, which were compared with antegrade perfusion of cardioplegia in 27 clinical cases. This study were investigated 1] cease and return of electromechanical activity after cardioplegia infusion 2] the myocardial temperature during operation 3] the aortic cross clamping time and total bypass time 4] frequency of DC shock for defibrillation 5] need for inotropic drugs after operation 6] electrocardiographic evidence of myocardial infarction or ventricular arrhythmia after operation 7] the enzymes activity during preoperative and postoperative period as an evaluation of myocardial ischemic injury and 8] operative mortality rate The combination of retrograde cardioplegia and topical cooling with ice slush yielded promptly hypothermia of myocardium and shorter aortic cross-clamping time compared with antegrade cardioplegia [P < 0.05]. The temperature of the interventricular septum was maintained below 20oC by continuous perfusion or intermittent perfusion of cold blood cardioplegia and other results were no statistically significant difference between the two methods [P >0.05]. This technique provides clear operative field and avoids some serious complications which are caused by coronary ostial cannulation. These results suggested that the retrograde perfusion of cardioplegia is a simple, safe, and effective means of myocardial protection during open heart surgery.

• 대한기계학회논문집B
• /
• 제21권4호
• /
• pp.518-524
• /
• 1997

Experimental studies on combustion phenomena within a porous ceramic burner are reported. Main interest of the present work is to investigate fundamental flame behaviors and their effects on the burner operation. Due to high thermal capacity of the porous ceramic materials, the response of flame to burning condition changes is slow and thus to have a stabilized flame is quite difficult and takes much time. It is found that the temperature profile obtained at downstream of the flame zone is not much sensitive to the movement of flame and the speed of flame movement is less than 0.1 mm/sec for the conditions tested. With the premixed LPG/air flame imbedded within the porous ceramic burner, stable combustion regions and unstable combustion regions leading to blowoff or flashback phenomena are observed and mapped on flow velocity versus equivalence ratio diagram. For the development of burner operation technique which is more practical and safe, intermittent burning technique, where the fuel or/and air is supplied to the burner intermittently, is proposed as one of the flame control methods for the porous ceramic burner and tested in this study. Through the experiment, it is realized that the proposed method is acceptable in respect to burner performance and give much flexibility in the operation of porous ceramic burner.

• 대한두경부종양학회지
• /
• 제33권1호
• /
• pp.85-89
• /
• 2017

A 62-year-old female patient had goiter for twenty years. She visited out-patient clinic with a hoarse voice and intermittent breathing difficulties. About protruding 15cm sized mass located the anterior neck and right vocal cord paralysis was observed. Preoperative CT scan was strongly suspected of thyroid gland cancer and cervical lymph node metastasis. Therefore, fine needle aspiration test was performed and surgical treatment was planned with the histopathologic results (papillary thyroid carcinoma). Surgery was performed with total thyroidectomy, bilateral cervical lymph node dissection, and right selective nodal lymph node dissection (level II-V). During operation right thyroid seemed to be adherent to surrounding tissue and the blood vessels were extremely engorged. There was hypotensive crisis because of intraoperative excessive bleeding. However it was managed by repetitive transfusion. The operation was completed without abnormalities. She underwent 4 times of bleeding control operation due to postoperative bleeding. After complications were improved, we are currently undergoing out-patient follow up without morbidity.

• Advances in pediatric surgery
• /
• 제14권1호
• /
• pp.88-93
• /
• 2008

Esophageal atresia with double tracheoesophageal fistula is a very rare anomaly and is difficulty to diagnose preoperatively. We treated a full term baby with esophageal atresia with double tracheoesophageal fistula. At the first operation, only the distal tracheoesophageal fistula was identified and ligated. When the upper esophageal pouch was opened, intermittent air leakages in sequence with positive bagging were noticed. However, intraoperative bronchoscopy did not identify a fistula in the proximal pouch, and the operation was completed with end to end anastomosis of the esophagus. On the $7^{th}$ postoperative day, esophagography showed another tracheoesophageal fistula proximal to the esophageal anastomosis. A wire was placed in the fistula preoperatively under bronchoscopy. At the 2nd operation through the same thoracotomy incision the proximal fistula was identified and ligated. On the $12^{th}$ postoperative day, esophagography showed neither stricture nor leakage.