• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.593-598
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• 2000

In this paper the critical speed analysis and design sensitivity investigation are carried out with an APU(auxiliary power unit) gas turbine having a spline shaft connection. The DDM(direct differential method) is directly applied to formulate the critical speed design sensitivity problem of a general nonsymmetric-matrix rotor-bearing system. The design sensitivity analysis have shown that the critical speed change rate to the support modeling of the spline shaft connection point is extremely negligible, and thereby its design uncertainty is lifted. It has also been confirmed that the critical speeds up to the 4th are not sensitive to the design stiffness coefficients of 4-main bearings or supports, including two air foil bearings. Further, the critical speed change rate to the shaft-element length have shown quantitatively that the spline shaft has some limited influence on the 4th critical speed.

• 대한기계학회논문집A
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• 제28권6호
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• pp.755-762
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• 2004

Dynamic analysis of the KTX can predict the dynamic motions in test drive. In this study an analytical model of the KTX is developed to find the critical speed. The numerical analysis for the nonlinear equation motions of 17 degrees of freedom shows the running stability and the critical speed due to the hunting motion of the KTX. Also, the vibration modes of the KTX are calculated using the ADAM/RAIL software, which show that the critical speed occurs for the yawing modes of the car body and the bogie. Finally, this paper shows that the critical speed of the KTX could be changed with the modifications of the design parameters of wheel conicity or wheel contact length.

• Journal of Advanced Marine Engineering and Technology
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• 제16권5호
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• pp.50-59
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• 1992

A critical speed analysis of a pump shaft has been investigated. Among various methods in the shaft critical speed calculation, a transfer matrix method has been examined in this research. After a brief review on the transfer matrix method, a modeling procedure for a continuous structure has been discussed. Then, a critical speed of a multistage pump shaft has been estimated up to several low modes. Throughout an analysis, parametric effects on the bearing stiffness, a degree of the modeling order, and attachmant of the impeller have been investigated. As an application example, a critical speed analysis of a verical pump which has been implemented in domestic electric power plants for cooling water circulation has been conducted in order to provide a safe operation as far as a pump vibration is concerned.

• Food Science and Biotechnology
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• 제18권2호
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• pp.279-293
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• 2009

Quantitative risk assessments are related to implementing hazard analysis and critical control points (HACCP) by its potential involvement in identifying critical control points (CCPs), validating critical limits at a CCP, enabling rational designs of new processes, and products to meet required level of safety, and evaluating processing operations for verification procedures. The quantitative risk assessment is becoming a standard research tool which provides useful predictions and analyses on microbial risks and, thus, a valuable aid in implementing a HACCP system. This paper provides a review of microbial modeling in quantitative risk assessments, which can be applied to HACCP systems.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.711-714
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• 2008

The objective of this study is to analyze the relationship between the watershed characteristics and the critical duration of design rainfall. For estimation of critical duration, adjustment Huff's method and ILLUDAS urban runoff model were applied to urban 21 areas. Watershed characteristics such as area, channel length, channel slope, shape factor, and pipe density were used to simulate correlation analysis. The conclusions of this study are as follows; it is revealed that critical duration is influenced by the watershed characteristics such as pipe density, area and channel length. Also, multiple regression analysis using watershed characteristics is carried out and the determination coefficient of multiple regression equation shows 0.972.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4647-4658
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• 2023

In this paper, elastic-plastic fracture mechanics analysis is performed to determine the critical crack sizes of the multipurpose canister (MPC) manufactured using austenitic stainless steel under dynamic loading conditions that simulate drop accidents. Firstly, dynamic finite element (FE) analysis is performed using Abaqus v.2018 with the KORAD (Korea Radioactive Waste Agency)-21 model under two drop accident conditions. Through the FE analysis, critical locations and through-thickness stress distributions in the MPC are identified, where the maximum plastic strain occurs during impact loadings. Then, the evaluation using the failure assessment diagram (FAD) is performed by postulating an external surface crack at the critical location to determine the critical crack depth. It is found that, for the drop cases considered in this paper, the principal failure mechanism for the circumferential surface crack is found to be the plastic collapse due to dominant high bending axial stress in the thickness. For axial cracks, the plastic collapse is also the dominant failure mechanism due to high membrane hoop stress, followed by the ductile tearing analysis. When incorporating the strain rate effect on yield strength and fracture toughness, the critical crack depth increases from 10 to 20%.

• 대한수학교육학회지:수학교육학연구
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• 제27권1호
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• pp.113-135
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• 2017

본 연구는 비판적 수학교육의 관점에서 수학교과서를 분석하기 위한 분석준거 개발을 목표로 하여 이루어졌다. 이를 위한 첫 단계로서 비판적 수학교육의 이론적 근간이 되는 비판 이론과 비판적 교육이론에 대한 문헌분석을 통해 비판적 수학교육의 철학적, 인식론적 기저를 고찰하였다. 또한 비판적 수학교육에 대한 국내외 문헌을 분석하여 비판적 수학교육의 개념화 논의, 실제 수업사례 등을 종합하여 '비판적 수학교육 관점에 따른 수학교과서 분석준거 안'을 구성하였다. 이후 제시한 준거 안에 대한 타당도를 검증하기 위해 전문가 델파이 조사를 실시하였다. 델파이 조사 분석 결과에 따라 제시한 준거 안을 수정, 보완하여 '고전적 지식', '공동체적 지식', '대화적 지식', '정치적 지식' 네 범주로 이루어진 '비판적 수학교육의 관점에 따른 수학교과서 분석준거'를 최종적으로 개발하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.291-295
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• 2003

The occurrence of ductile fracture is the working limit of many metal forming processes. It is necessary to predict the criteria and to apply the condition in a process design. Over the years. the way for clarifying conditions have been studied and presented. However such a way needs lots of experiments and analysis. In this study, in order to determine the critical damage value of a used material Cu 4N, it was performed a tensile test and FEM analysis by using DEFORM 2D. For applying the obtained critical damage value it was also performed a upsetting test by using DEFORM 2D. The way of determining a critical damage value which is presented in this study will make possible to find easily it which is one of the working limit factor. And the way of determining a critical damage value will make possible to find in multi-pass drawing process.

• 한국소음진동공학회논문집
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• 제16권3호
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• pp.247-254
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• 2006

This paper (Part II) provides the application results of the method presented in a companion paper (Part I) where the dynamic equation for rotating polar orthotropic disk is formulated and its solution method is considered. The natural frequencies and critical speed of polycarbonate CD are calculated to validate the present method and are shown to by very accurate. The critical speeds of typical GFRP and CFRP CD's are computed by aligning the fibers in radial and circumferential directions. The radially reinforced CFRP CD is shown to have the five times higher critical speed than that of the polycarbonate CD. The natural frequencies and critical speeds of disks with various elastic modulus ratios are obtained. The results show that the radially reinforced disk is more effective in increasing critical speed than the circumferentially reinforced disk.

• 중환자간호학회지
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• 제10권1호
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• pp.41-50
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• 2017

Purpose: The purpose of this study was to describe what critical care nurses perceived about life-sustaining treatment at end of life. Methods: A qualitative content analysis method was utilized. The unit of analysis was interview text obtained from fifty critical care nurses of a general hospital. Results: Seven categories in two content areas were abstracted. In the negative perception area, the following five categories were abstracted: patients' suffering, dying with damaged dignity, patients' isolation from family members, regret about choosing life-sustaining treatment, and family members' burden. In the positive perception area, the following two categories were abstracted: willingness to sustain life and duty as family members. Conclusions: Nurses have better competencies pertaining to understanding patients' responses and suffering than any other health care professions do. Nurses should play an important role in advocating for patients and their family in the process of end-of-life care decision making.