• 한국철도학회논문집
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• 제9권1호
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• pp.63-68
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• 2006

This paper proposes a fast Fourier transform(FFT)-based spectral analysis method(SAM) for the dynamic responses of the linear discrete dynamic models with non-proportional damping. The SAM was developed by using discrete Fourier transform(DFT)-theory. To verify the proposed SAM, a three-DOF system with non-proportional viscous damping is considered as an illustrative example. The present SAM is evaluated by comparing the dynamic responses obtained by SAM with those obtained by Runge-Kutta method.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2002년도 정기학술대회
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• pp.415-415
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• 2002

Proportional hazards model can be used to develop a realistic approach to determine the performance of a system. The proportional hazards model is typically applied for a group of equipments to assess the importance of factors that may influence the reliability of a system. In this paper we considered the interarrival times of a maintained system for the analysis of reliability, maintainability and availability. In order to demonstrate the proposed approach, an example is presented.

• Journal of the Korean Data and Information Science Society
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• 제15권3호
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• pp.605-616
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• 2004

In this paper we consider the proportional hazard models for survival analysis in the microarray data. For a given vector of response values and gene expressions (covariates), we address the issue of how to reduce the dimension by selecting the significant genes. In our approach, rather than fixing the number of selected genes, we will assign a prior distribution to this number. To implement our methodology, we use a Markov Chain Monte Carlo (MCMC) method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.77-84
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• 2003

In this paper, the refined plastic-hinge analysis accounting for the effect of strain reversal caused by non-proportional loading is developed. This analysis accounts for material and geometric nonlinearities of the structural system and its component members. Moreover, the problem, conventional refined plastic-hinge analyses have underestimated the strength of structures subjected to non-proportional loading, is overcome. The modified stiffness degradation model approximating the effect of strain reversal is discussed in detail. The proposed analysis is verified by the comparison of the finite element analysis. A case study shows that the effect of strain reversal is a very crucial element to be considered in second-order plastic-hinge analysis. The proposed analysis is shown to be an efficient, reliable tool ready to be implemented into design practice.

• 한국수학교육학회지시리즈A:수학교육
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• 제46권3호
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• pp.315-329
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• 2007

The concepts of ratio, rate, and proportion are used in everyday life and are also applied to many disciplines such as mathematics and science. Proportional reasoning is known as one of the pivotal ideas in school mathematics because it links elementary ideas to deeper concepts of mathematics and science. However, previous research has shown that it is difficult for students to recognize the proportionality in contextualized situations. The purpose of this study is to understand how the mathematical concept in the middle school mathematics curriculum is connected with ratio, rate, and proportion and to investigate the characteristics of proportional reasoning through analyzing the concept including ratio, rate, and proportion on the middle school mathematics curriculum. This study also examines mathematical concepts (direct proportion, slope, and similarity) presented in a middle school textbook by exploring diverse interpretations among ratio, rate, and proportion and by comparing findings from literature on proportional reasoning. Our textbook analysis indicated that mechanical formal were emphasized in problems connected with ratio, rate, and proportion. Also, there were limited contextualizations of problems and tasks in the textbook so that it might not be enough to develop students' proportional reasoning.

• 드라이브 ㆍ 컨트롤
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• 제16권4호
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• pp.56-64
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• 2019

Recently, as the environmental regulation for earth moving equipment has been tightened, advanced systems using electronic control have been introduced for energy savings. An IMV(Independent Metering Valve), which consists of four 2-way valves, is one of the electro-hydraulic control systems that provides more flexible controllability and potential for energy savings in excavators, when compared to the conventional 4-way spool valve system. To fully realize an IMV, a two-stage bi-directional flow control valve which can regulate the large amount of flow in both directions, should be developed in advance. A simple design that allows proportional flow control to apply the pilot pressure from the current-controlled solenoid to the spring loaded flow control spool and thus valve displacement, is proportional to the solenoid current. However, this open-loop type valve is vulnerable to flow force which directly affects the valve displacement. Force feedback servo of which the position loop is closed by the feedback spring which interconnects the solenoid valve and flow control spool, could compensate for the flow force. In this study, linearity for the solenoid current input and robustness against load pressure disturbance is investigated by linear analysis of the static nonlinear equations for the IMV proportional flow control valve with feedback spring. Gains of the linear system confirm the performance improvement with the feedback spring design.

• 대한수학교육학회지:수학교육학연구
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• 제22권3호
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• pp.331-352
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• 2012

이 연구는 비례문제 해결에 영향을 주는 인지적 변인이 무엇인지 확인하는 것을 궁극적인 목적으로 한다. 이를 위해 비례 문제를 구조화 정도에 따라 잘-구조화된 문제, 구조화된 문제, 비-구조화된 문제로 분류하고, 이론적 고찰을 통해 비례문제 해결에 영향을 주는 인지적 변인으로 사실 알고리즘 지식, 개념적 지식, 문제유형 지식, 양의 변화 인식, 메타인지를 추출하였다. 중다회귀분석 방법을 사용해 구조화 정도가 다른 문제를 해결하는데 유의하게 영향을 주는 인지적 변인이 무엇인지를 분석하였다. 분석 결과 구조화 정도가 다른 문제를 해결하는데 서로 다른 인지적 변인이 영향을 주었다. 즉 잘-구조화된 문제 해결에는 사실 알고리즘 지식과 문제유형 지식, 그리고 구조화된 문제 해결에는 개념적 지식, 문제유형지식, 양의 변화 인식, 마지막으로 비-구조화된 문제해결에는 메타조절, 개념적 지식, 양의 변화 인식, 문제유형지식이 영향을 주었다. 이처럼 문제 유형에 따라 다른 인지적 변인이 영향을 미치기 때문에, 수학수업에서는 문제 유형에 따라 다른 교수학습 방법과 다른 평가 틀을 적용할 필요가 있으며, 더불어 학생들의 비례 문제 해결 능력을 계발하기 위해서는 수학 수업에서 구조화된 문제와 비-구조화된 문제를 적극 활용할 필요가 있다는 결론을 도출할 수 있었다.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제25권3호
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• pp.537-556
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• 2011

본 연구에서는 최근 초등 수학에서 중요시 되고 있는 비례 추론에 초점을 두고 비례 문제를 해결하는 과정에서 학생들의 학업성취도에 따른 비례 추론 능력과 비례 추론 전략 사용의 특징을 분석하였다. 이를 위하여 초등학교 6학년 173명을 대상으로 다양한 유형의 비례 문제를 제시하고 최대 세 가지 추론 전략을 사용하여 해결하도록 하였다. 그 결과 상위권 학생들이 하위권 학생들보다 다양한 비례 추론 전략을 활용하고, 표현하고, 인식하는 능력이 뛰어남을 알 수 있었다. 또한 학생들이 선호하는 비례 추론 전략은 학업성취도에 따라서는 별 차이를 보이지 않았으나 문제 유형과 문제에 제시된 숫자들의 비에 따라 차이가 있는 것으로 나타났다. 이를 통해 학생들의 학습 수준에 따른 능력 차이를 반영하여 적절한 비례적 추론 지도가 필요함을 알 수 있었다.

• 지식경영연구
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• 제11권2호
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• pp.95-109
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• 2010

The objectives of this study are to identify the survival function (hazard function) of small and medium enterprises by using technology rating data for the companies guaranteed by Korea Technology Finance Corporation (KOTEC), and to figure out the factors that affects their survival. To serve the purposes, this study uses Kaplan-Meier Analysis as a non-parametric method and Cox proportional hazards model as a semi-parametric one. The 17,396 guaranteed companies that assessed from July 1st in 2005 to December 31st in 2009 are selected as samples (16,504 censored data and 829 accident data). The survival time is computed with random censoring (Type III) from July in 2005 as a starting point. The results of the analysis show that Kaplan-Meier Analysis and Cox proportional hazards model are able to readily estimate survival and hazard function and to perform comparative study among group variables such as industry and technology rating level. In particular, Cox proportional hazards model is recognized that it is useful to understand which technology rating items are meaningful to company's survival and how much they affect it. It is considered that these results will provide valuable knowledge for practitioners to find and manage the significant items for survival of the guaranteed companies through future technology rating.

• 조명전기설비학회논문지
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• 제26권7호
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• pp.84-91
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• 2012

In this paper, design by magnetic analysis software and proportional control of solenoid for pressure valve for electric pressure cooker is described. The validation of design was proved by 3D finite element analysis results. Also the efficiency of an air ventilation mechanism was considered when pressure was happened by fluid analysis results. The linear proportional control system by AVR was manufactured and its validation was proved by pressure control of solenoid.