• International Journal of Reliability and Applications
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• 제11권2호
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• pp.123-138
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• 2010

This paper investigates a mathematical model of a system composed of two non-identical unit parallel system with common-cause failure, critical human error, non-critical human error, preventive maintenance and two type of repair, i.e. cheaper and costlier. This system goes for preventive maintenance at random epochs. We assume that the failure, repair and maintenance times are independent random variables. The failure rates, repair rates and preventive maintenance rate are constant for each unit. The system is analyzed by using the graphical evaluation and review technique (GERT) to obtain various related measures and we study the effect of the preventive maintenance preventive maintenance on the system performance. Certain important results have been derived as special cases. The plots for the mean time to system failure and the steady-state availability A(${\infty}$) of the system are drawn for different parametric values.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.197-205
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• 2013

Real time transient stability assessment mainly depends on real-time prediction. Unfortunately, conventional techniques based on offline analysis are too slow and unreliable in complex power systems. Hence, fast and reliable stability prediction methods and simple stability criterions must be developed for real time purposes. In this paper, two new methods for real time determining critical clearing time based on clustering identification are proposed. This article is covering three main sections: (i) clustering generators and recognizing critical group; (ii) replacing the multi-machine system by a two-machine dynamic equivalent and eventually, to a one-machine-infinite-bus system; (iii) presenting a new method to predict post-fault trajectory and two simple algorithms for calculating critical clearing time, respectively established upon two different transient stability criterions. The performance is expected to figure out critical clearing time within 100ms-150ms and with an acceptable accuracy.

• 융합보안논문지
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• 제13권2호
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• pp.175-183
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• 2013

본 연구는 전문대학 신입생의 비판적 사고성향과 문제해결과정의 정도를 파악한 후 이들 간의 상관성과 문제해결과정에 미치는 영향을 파악하고자 수행하였다. 연구대상은 전문대학에 재학 중인 1학년 215명이었고 자료수집은 구조화된 설문지를 이용하여 2012년 11월 20일에서 12월 5일까지 수집하였고 SPSS 18.0으로 분석하였다. 연구결과, 전문대학 신입생의 비판적 사고성향은 연령, 대인관계에서 유의한 차이가 있었고, 문제해결과정은 연령, 대인관계, 전공만족도에서 유의한 차이가 있었다. 전문대학 신입생의 비판적 사고성향과 문제해결과정간의 관계는 통계적으로 유의한 양의 상관관계(r=.605, P<.001)를 나타냈다. 전문대학 신입생의 문제해결과정에 영향을 미치는 요인은 비판적 사고성향과 전공 만족도로 문제해결과정을 38% 설명하였다. 본 연구는 전문대학생의 비판적 사고성향이 문제해결에 미치는 영향에 대한 실증연구를 표준적인 방법론에 의거 체계적으로 수행하여 비판적 사고성향과 전공만족도를 높일 수 있는 합리적인 교수학습 전략 및 교육과정 개발 방향을 제시하였다는 점에서 그 의의를 찾을 수 있다.

• 콘크리트학회논문집
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• 제14권1호
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• pp.58-66
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• 2002

본 연구의 목적은 유효탄성균열모델과 점성균열모델의 개념에 기초한 임계응력확대계수, 임계균열단개구변위와 파괴에너지, 이선형 연화 곡선같은 콘크리트의 파괴특성들을 초기재령 콘크리트에 관해 구명하는 것이다. 이를 위해 모드 I의 파괴를 일으킬 수 있는 쐐기쪼갬시험이 노치가 있는 육각형의 쐐기 시험체에 대하여 수행되었다. 강도와 재령의 변화에 따라 하중-균열입구변위 곡선이 얻어졌으며, 이것은 선형탄성 파괴역학과 유한요소법에 의해 분석되었다. 실험 결과를 분석한 결과, 재령 1일부터 재령 28일까지의 임계응력확대계수와 파괴에너지는 증가하였으며, 임계균열단개구변위는 감소하였다. 또한 수치해석을 통하여 재령 1일부터 재령 28일까지의 이선형 연화 곡선의 네 파라미터를 구할 수 있었다. 이렇게 얻어진 초개재령 콘크리트의 파괴특성치와 이선형 연화 곡선은 초기재령 콘크리트의 파괴 기준과 유한요소해석시의 입력 상수로서 사용될 수 있을 것이다.

• 한국공간구조학회논문집
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• 제22권3호
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• pp.25-32
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• 2022

In this paper, the instability of the domed spatial truss structure using wood and the characteristics of the buckling critical load were studied. Hexagonal space truss was adopted as the model to be analyzed, and two boundary conditions were considered. In the first case, the deformation of the inclined member is only considered, and in the second case, the deformation of the horizontal member is also considered. The materials of the model adopted in this paper are steel and timbers, and the considered timbers are spruce, pine, and larch. Here, the inelastic properties of the material are not considered. The instability of the target structure was observed through non-linear incremental analysis, and the buckling critical load was calculated through the singularities and eigenvalues of the tangential stiffness matrix at each incremental step. From the analysis results, in the example of the boundary condition considering only the inclined member, the critical buckling load was lower when using timber than when using steel, and the critical buckling load was determined according to the modulus of elasticity of timber. In the case of boundary conditions considering the effect of the horizontal member, using a mixture of steel and timber case had a lower buckling critical load than the steel case. But, the result showed that it was more effective in structural stability than only timber was used.

• 한국콘텐츠학회논문지
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• 제21권11호
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• pp.638-645
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• 2021

본 연구는 간호대학생의 생명의료윤리의식과 비판적 사고성향이 간호전문직관에 미치는 영향을 알아보고자 시도되었다. 본 연구는 2021년 5월부터 6월까지 충청남도 S대학의 간호대학생 144명을 대상으로 구조화된 설문을 통해 데이터를 수집하였다. 자료의 분석은 기술통계, t-test, ANOVA, Scheffe test, Pearson's 상관관계 분석, 다중회귀분석을 이용하였다. 본 연구의 결과 간호대학생의 간호전문직관은 생명의료윤리의식과 비판적 사고성향에 유의한 양의 상관관계(r=.400, p<.001, r=.431, p<.001)가 있었다. 간호대학생의 간호전문직관에 영향을 미치는 요인은 학년(𝛽=0.303, p<.001), 생명의료윤리의식(𝛽=0.287, p<.001)과 비판적 사고성향(𝛽=0.294, p<.001)이었고, 설명력은 31.2%였다. 본 연구의 결과로 간호대학생의 간호전문직관을 높여주기 위해 생명의료윤리의식과 비판적 사고성향을 높여주는 것이 필요하며, 그 방안으로는 학생의 학년을 고려한 생명의료윤리의식과 비판적 사고성향 프로그램의 개발과 적용이 있다.

• Nuclear Engineering and Technology
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• 제41권1호
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• pp.91-98
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• 2009

The "3+3 Process" for safety critical software for nuclear power plants' I&C (Instrumentation and Control system) has been developed in this work. The main idea of the "3+3 Process" is both to simplify the software development and safety analysis in three steps to fulfill the requirements of a software safety plan [1]. The "3-Step" software development process consists of formal modeling and simulation, automated code generation and coverage analysis between the model and the generated source codes. The "3-Step" safety analysis consists of HAZOP (hazard and operability analysis), FTA (fault tree analysis), and DV (design validation). Put together, these steps are called the "3+3 Process". This scheme of development and safety analysis minimizes the V&V work while increasing the safety and reliability of the software product. For assessment of this process, validation has been done through prototyping of the SDS (safety shut-down system) #1 for PHWR (Pressurized Heavy Water Reactor).

• Structural Engineering and Mechanics
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• 제41권4호
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• pp.559-573
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• 2012

An adaptive modeling and simulation technique is introduced for the effective and reliable fluid-structure interaction analysis using MSC/Dytran for large-scale complex pressurized liquid containment. The proposed method is composed of a series of the global rigid sloshing analysis and the locally detailed fluid-structure analysis. The critical time at which the system exhibits the severe liquid sloshing response is sought through the former analysis, while the fluid-structure interaction in the local region of interest at the critical time is analyzed by the latter analysis. Differing from the global coarse model, the local fine model considers not only the complex geometry and flexibility of structure but the effect of internal pressure. The locally detailed FSI problem is solved in terms of multi-material volume fractions and the flow and pressure fields obtained by the global analysis at the critical time are specified as the initial conditions. An in-house program for mapping the global analysis results onto the fine-scale local FSI model is developed. The validity and effectiveness of the proposed method are verified through an illustrative numerical experiment.

• International Journal of Automotive Technology
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• 제8권2호
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• pp.243-248
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• 2007

The durability of a cylinder head is influenced by the thermal and mechanical history during the manufacturing process, as well as engine operation. In order to improve the durability of cylinder head, both load from engine operation and the preload conditions from the manufacturing process must be considered. The aluminum cylinder head used for a HSDI diesel engine is investigated to reduce the possibility of high cycle fatigue crack in this study. FE analysis is performed to elucidate the mechanism of high cycle fatigue crack in the HSDI diesel cylinder head. Two separate approaches to increase the durability of the cylinder head are discussed: reducing load from engine operation and re-arranging preload conditions from the manufacturing process at the critical location of the cylinder head. Local design changes of the cylinder head and modification of pretension load in the cylinder head bolt were investigated using FE analysis to relieve load at the critical location during engine operation. Residual stress formed at the critical location during the manufacturing process is measured and heat treatment parameters are changed to re-arrange the distribution of residual stress. Results of FE analysis and experiments showed that thorough consideration of the manufacturing process is necessary to enhance the durability of the cylinder head.

• 성인간호학회지
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• 제12권4호
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• pp.517-532
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• 2000

The purpose of this study was to develop a critical pathway for case management of patients who have received Lumbar Laminectomy because of low back pain, arm and leg numbness, and radiating pain in the leg. For this study, a preliminary critical pathway was developed through a review of the literature including five critical pathways which are currently being used in the USA. In order to identify the overall service contents required by these patients, 30 cases were analyzed. These cases were taken from medical records of those with Lumbar Laminectomy between January, 1998 and December, 1998 in the department of neurosurgery at the Pusan National University Hospital in Pusan. An expert validity test was done for the preliminary critical pathway, a clinical validity test was also done using 12 patients with Lumbar Laminectomy between October 1, 1999 and January 31, 2000. After these processes, the final critical pathway was developed. The results are summarized as follows. 1. The vertical axis of the critical pathway includes the following eight items: assessment, consultation, diet, test, medication, treatment, activity, education/ discharge planning. The horizontal axis includes the time from the start of hospitalization to discharge. Analysis of the 30 medical records was done. analysis of the service contents showed the horizontal axis of the preliminary critical pathway was set from hospitalization to the 12th post operation day and the vertical axis was set to include eight items, the contents which should have occurred, according to the time frames of the horizontal axis. 2. As a result of the expert validity test, it was found that among the 233 items, 203 showed over 88% agreement and 30 of them showed less than 88% agreement, which were then revised or deleted from the critical pathway. At the preliminary meeting for the clinical validity test, the time of hospitalization on the horizontal axis was shortened to the 10th post operation day. A clinical validity test was done with 12 patients with Lumbar Laminectomy. All the cases progressed according to the critical pathway although some variances were noted in assessment, consultation, test, medication, and treatment. 3. Based on these results, a final critical pathway was determined. In conclusion, this critical pathway is partially applicable to the care of patients with Lumbar Laminectomy and needs further investigation.