• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3275-3285
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• 2021

A Nuclear Power Plant (NPP) is a complex dynamic system-of-systems with highly nonlinear behaviors. In order to control the plant operation under both normal and abnormal conditions, the different systems in NPPs (e.g., the reactor core components, primary and secondary coolant systems) are usually monitored continuously, resulting in very large amounts of data. This situation makes it possible to integrate relevant qualitative and quantitative knowledge with artificial intelligence techniques to provide faster and more accurate behavior predictions, leading to more rapid decisions, based on actual NPP operation data. Data-driven models (DDM) rely on artificial intelligence to learn autonomously based on patterns in data, and they represent alternatives to physics-based models that typically require significant computational resources and might not fully represent the actual operation conditions of an NPP. In this study, a feed-forward backpropagation artificial neural network (ANN) model was trained to simulate the interaction between the reactor core and the primary and secondary coolant systems in a pressurized water reactor. The transients used for model training included perturbations in reactivity, steam valve coefficient, reactor core inlet temperature, and steam generator inlet temperature. Uncertainties of the plant physical parameters and operating conditions were also incorporated in these transients. Eight training functions were adopted during the training stage to develop the most efficient network. The developed ANN model predictions were subsequently tested successfully considering different new transients. Overall, through prompt prediction of NPP behavior under different transients, the study aims at demonstrating the potential of artificial intelligence to empower rapid emergency response planning and risk mitigation strategies.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.521-528
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• 2018

전투목적으로 개발된 군용차량은 타이어 압력이 손실되더라도 일정시간동안 일정거리를 달릴 수 있도록 런플랫시스템을 도입하였다. 런플랫을 적용하기 위하여 휠을 외측림과 내측림으로 구성된 2개의 부분으로 구성하고, 클램핑 볼트를 체결함으로써 외측림과 내측림을 조립한다. 이 클램핑 볼트는 휠의 내구성을 결정하는 중요 부품이다. 실제로 휠의 내측림과 외측림의 파손보다는 클램핑볼트의 파손이 발생되어 휠을 사용하지 못하는 빈도가 높다. 따라서, 클램핑 볼트의 내구성능이 휠의 내구성능과 연관이 크다고 할 수 있다. 본 연구는 휠의 내구성을 향상시키기 위하여 휠조립체를 시험하고 클램핑 볼트를 개발하는 과정을 다루었다. 기존에 정립된 내구시험 조건의 불충분성을 식별하였으며, 휠조립체의 내구성을 보다 정확히 확인할 수 있도록 통제해야 하는 시험조건을 제시하였다. 정립된 시험조건을 기반으로, 성능이 개선된 클램핑 볼트를 시험하였다. 시험조건을 확인한 결과 기존 제품보다 최소 168% 내구성이 향상됨을 확인할 수 있었다. 본 연구는 휠 조립체의 내구시험 방법과 클램핑 볼트를 개발하는 과정에서 고려해야 할 요소를 제시한 것에 의미가 있다 할 수 있다.

• Journal of Korean Neurosurgical Society
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• 제62권5호
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• pp.526-535
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• 2019

Objective : While the risk of aneurysmal rebleeding induced by catheter cerebral angiography is a serious concern and can delay angiography for a few hours after a subarachnoid hemorrhage (SAH), current angiographic technology and techniques have been much improved. Therefore, this study investigated the risk of aneurysmal rebleeding when using a recent angiographic technique immediately after SAH. Methods : Patients with acute SAH underwent immediate catheter angiography on admission. A four-vessel examination was conducted using a biplane digital subtraction angiography (DSA) system that applied a low injection rate and small volume of a diluted contrast, along with appropriate control of hypertension. Intra-angiographic aneurysmal rebleeding was diagnosed in cases of extravasation of the contrast medium during angiography or increased intracranial bleeding evident in flat-panel detector computed tomography scans. Results : In-hospital recurrent hemorrhages before definitive treatment to obliterate the ruptured aneurysm occurred in 11 of 266 patients (4.1%). Following a univariate analysis, a multivariate analysis using a logistic regression analysis revealed that modified Fisher grade 4 was a statistically significant risk factor for an in-hospital recurrent hemorrhage (p=0.032). Cerebral angiography after SAH was performed on 88 patients ${\leq}3$ hours, 74 patients between 3-6 hours, and 104 patients >6 hours. None of the time intervals showed any cases of intra-angiographic rebleeding. Moreover, even though the DSA ${\leq}3$ hours group included more patients with a poor clinical grade and modified Fisher grade 4, no case of aneurysmal rebleeding occurred during erebral angiography. Conclusion : Despite the high risk of aneurysmal rebleeding within a few hours after SAH, emergency cerebral angiography after SAH can be acceptable without increasing the risk of intra-angiographic rebleeding when using current angiographic techniques and equipment.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.709-718
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• 2019

The international nuclear industry has undergone a lot of changes since the Fukushima, Chernobyl and TMI nuclear power plant accidents. However, there are still large and small component deficiencies at nuclear power plants in the world. There are many causes of electrical equipment defects. There are also factors that cause component failures due to human errors. This paper analyzed the root causes of failure and types of human error in 300 cases of electrical component failures. We analyzed the operating experience of electrical components by methods of root causes in K-HPES (Korean-version of Human Performance Enhancement System) and by methods of human error types in HuRAM+ (Human error-Related event root cause Analysis Method Plus). As a result of analysis, the most electrical component failures appeared as circuit breakers and emergency generators. The major causes of failure showed deterioration and contact failure of electrical components by human error of operations management. The causes of direct failure were due to aged components. Types of human error affecting the causes of electrical equipment failure are as follows. The human error type group I showed that errors of commission (EOC) were 97%, the human error type group II showed that slip/lapse errors were 74%, and the human error type group III showed that latent errors were 95%. This paper is meaningful in that we have approached the causes of electrical equipment failures from a comprehensive human error perspective and found a countermeasure against the root cause. This study will help human performance enhancement in nuclear power plants. However, this paper has done a lot of research on improving human performance in the maintenance field rather than in the design and construction stages. In the future, continuous research on types of human error and prevention measures in the design and construction sector will be required.

• 한국정보통신학회논문지
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• 제23권7호
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• pp.845-851
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• 2019

본 논문에서는 애드혹 라우팅 네트워크를 다양한 사용자 모바일 기기에서 사용하기 위한 설계 방법을 소개하고, 이를 모바일 기기에 직접 구현하여 실제 환경에서 어떻게 작동하는지 성능을 관찰하고 검증하였다. 상용 사용자 모바일 기기에서의 애드혹 라우팅 네트워크의 사용성을 고려해 커널을 수정하지 않고 사용자 계층에서 구현하는 디자인을 선택하였다. 또한 이동성이 높은 환경에서 적절히 사용하기 위해 기존 애드혹 라우팅 네트워크들을 분석하였으며 그 결과 사용자 계층에서 AODV (ad-hoc on-demand distance vector) 프로토콜과 TCP를 구현하였다. 모바일 기기들이 일렬로 놓여 있는 환경과 중앙 노드가 주변 노드 여러 대와 통신하는 환경에서 실험을 진행하였고, 그 결과 일렬로 놓인 환경에서 최대 12 홉, 중앙 노드와 주변 노드가 통신하는 환경에서 최대 5 개의 노드와 통신하는 것을 확인하였다.

• 한국전자통신학회논문지
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• 제14권1호
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• pp.97-110
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• 2019

제 4차 산업혁명이 각광받고 있는 가운데 통신 장애를 대비한 다양한 기술이 개발되어 상용화되고 있다. 그러나 IDC의 백업망은 많은 개발이 진행되고 있으나 소규모 저전력의 개인 또는 센서에 대한 통신 장애 대비는 다소 부족한 것이 현실이다. 이에 시중에서 쉽게 구할 수 있는 라즈베리 파이 재단의 라즈베리 파이 제품군에 OpenWRT 펌웨어를 사용하여 저전력 개인 로드 밸런서를 구축하고, USB기반 LTE 안테나를 통해 유선통신에 장애 발생 시 LTE를 통하여 장애 알림과 중요 데이터를 송신할 수 있는 시스템을 개발하였다. 시중에서 쉽게 구할 수 있는 제품들인 점과 USB를 사용함으로 다른 초소형 개발보드에서도 응용할 수 있기 때문에 개인의 센서 네트워크 망 구축에 많은 도움이 될 것이라 기대된다.

• Neurospine
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• 제15권4호
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• pp.368-375
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• 2018

Objective: To evaluate the results of operative management of subaxial spine injuries managed with 2-level anterior cervical corpectomy and fusion with a cervical locking plate and autologous bone-filled titanium mesh cage. Methods: This study included 23 patients with a subaxial spine injury who matched the inclusion criteria, underwent 2-level anterior cervical corpectomy and fusion at our institution between 2013 and 2016, and were followed up for neurological recovery, axial pain, fusion, pseudarthrosis, and implant failure. Results: According to Allen and Ferguson classification, there were 9 cases of distractive extension; 4 of compressive extension; 3 each of compressive flexion, vertical compression, and distractive flexion; and 1 of lateral flexion. Sixteen patients had a score of 6 on the Subaxial Injury Classification system, and the rest had a score of more than 6. The mean follow-up period was 19 months (range, 12-48 months). Neurological recovery was observed in most of the patients (78.21%). All patients experienced relief of axial pain. None of the patients received a blood transfusion. Twenty-one patients (91.3%) showed solid fusion and 2 (8.69%) showed possible pseudarthrosis, with no complications related to the cage or plate. Conclusion: Two-level anterior cervical corpectomy and fusion, along with stabilization with a cervical locking plate and autologous bone graft-filled titanium mesh cage, can be considered a feasible and safe method for treating specific subaxial spine injuries, with the benefits of high primary stability, anatomical reduction, and direct decompression of the spinal cord.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.809-810
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• 2016

본 논문에서는 주행 중 운전자가 브레이크 페달을 조작할 경우, 차량 후미의 브레이크등과 연계되어 점등됨과 동시에 차량의 감속 정도에 따라 점등되는 영역이 단계적으로 점멸되며 표시되는 속도 감응형 차량용 브레이크등 시스템을 구현하여 실험적으로 확인하였다. 뒤따르는 후방 차량이 선행차량의 감속상태를 더욱 쉽고 빠르게 인지시킴으로써 선행 차량의 급정거에 따른 추돌 사고를 예방할 수 있으며, 후방 차량의 신속한 대응을 이끌어낼 수 있다. 또한 초음파 센서를 이용하여 차간 거리가 일정 거리 이상으로 가까워지는 경우, 부져와 함께 비상등이 켜지며 후방 차량의 운전자에게 상황을 전달한다.

• 한국안전학회지
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• 제33권6호
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• pp.144-156
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• 2018

Level 3 Probabilistic Safety Assessment (PSA) is performed for the risk assessment that calculates radioactive material dispersion to the environment. This risk assessment is performed with a tool of MELCOR Accident Consequence Code System (MACCS2 or WinMACCS). For the off-site consequence analysis of multi-unit nuclear power plant (NPP) accident, the single location (Center Of Mass, COM) method has been usually adopted with the assumption that all the NPPs in the nuclear site are located at the same COM point. It was well known that this COM calculation can lead to underestimated or overestimated radionuclide concentration. In order to overcome this underestimation or overestimation of radionuclide concentrations in the COM method, Multiple Location (ML) method was developed in this study. The radionuclide concentrations for the individual NPPs are separately calculated, and they are summed at every location in the nuclear site by the post-processing of radionuclide concentrations that is based on two-dimensional Gaussian Plume equations. In order to demonstrate the efficiency of the ML method, radionuclide concentrations were calculated for the six-unit NPP site, radionuclide concentrations of the ML method were compared with those by COM method. This comparison was performed for conditions of constant weather, yearly weather in Korea, and four seasons, and the results were discussed. This new ML method (1) improves accuracy of radionuclide concentrations when multi-unit NPP accident occurs, (2) calculates realistic atmospheric dispersion of radionuclides under various weather conditions, and finally (3) supports off-site emergency plan optimization. It is recommended that this new method be applied to the risk assessment of multi-unit NPP accident. This new method drastically improves the accuracy of radionuclide concentrations at the locations adjacent to or very close to NPPs. This ML method has a great strength over the COM method when people live near nuclear site, since it provides accurate radionuclide concentrations or radiation doses.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제8권10호
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• pp.231-238
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• 2019

차세대 염기 서열 분석법이 생성한 유전체 원시 데이터를 기존의 방식대로 하나의 서버에서 분석하기 위해서는 데이터 크기에 따라 수십 시간이 필요할 수 있다. 그러나 응급 환자의 진단처럼 수 시간 내에 결과를 알아야 하는 상황이 존재하기 때문에 단일 유전체 분석의 성능을 향상시킬 필요가 있다. 본 연구에서는 빅데이터 기술의 병렬화 기법과 고속의 네트워크로 연결되고 병렬파일시스템을 공유하는 고성능컴퓨팅 클러스터를 적극적으로 활용하여 분석 시간을 크게 단축시킬 수 있는 유전체 데이터 분석의 전처리 프로세스의 병렬화 방법을 제안한다. 분석 데이터의 신뢰성을 위해 기존의 검증된 분석 도구 및 알고리즘을 새로운 환경에 맞게 병렬화 하는 전략을 선택하였다. 프로세스의 병렬화, 데이터의 분배 및 병렬 병합 기법을 개발하였고 실험을 통해 성능 향상을 확인하였다.