• Journal of Power Electronics
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• 제7권3호
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• pp.203-212
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• 2007

In this paper, a proposed approach to improve the power factor of three-phase rectifiers and to stabilize the output voltage against load change is presented. The elements of the given control strategy are small size, low cost, high performance, and simplicity. The proposed control strategy of switches is based on a prototype of three bi-directional switched consisting of four diodes and one IGBT. A control technique and operational procedure are also developed, both theoretically and experimentally. The experimental results clearly verify the theoretical analysis from the prototype connected to grid unity.

• KDI Journal of Economic Policy
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• 제34권2호
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• pp.95-137
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• 2012

외국인력 및 이민 유입은 경제 전반에 걸쳐 저숙련 노동공급을 증가시키는 효과를 가진다. 그 영향으로부터 완전히 독립적인 통제집단은 경제 내에 존재하지 않기 때문에 효과평가방법(impact evaluation method)에 의한 영향평가는 한계를 지닌다. 본 연구에서는 총요소비율 접근방법(aggregate factor proportions approach)을 채택하여 경제 내 저숙련 노동공급 증가의 효과를 추정함으로써 외국인 유입의 영향을 평가한다. 평가 결과는 외국인력 및 이민 유입은 숙련 노동력과 저숙련 노동력 간의 임금격차를 상당히 확대시키는 반면, 성장에 대한 기여는 크지는 않음을 제시한다. 그 이유는 국내에 유입되는 외국인력의 절대다수가 생산성이 낮은 단순인력이라는 데에 있다.

• 대한불안의학회지
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• 제7권1호
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• pp.16-21
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• 2011

Objective : Depressive symptoms often coexist with other anxiety disorder symptoms. Furthermore, an anxiety disorder that is comorbid with a depressive disorder results in more severe symptoms and a poorer outcome prognosis. To understand the construct of depressive symptoms in anxiety disorder, this study investigated the factor structure of the Beck Depression Inventory among outpatients with anxiety disorders. Methods : All data were from psychiatric department outpatients at a university-affiliated hospital. We conducted a principal component analysis using data from 194 outpatients with DSM-IV anxiety disorders and calculated goodness-of-fit-indices. Results : Exploratory factor analysis revealed a four factor structure--Cognitive-affective symptoms (Factor 1), Somatic symptoms (Factor 2), Self-reproach (Factor 3), and Hypochondriasis/indecisiveness (Factor 4)--and a 57% total variance. This four-factor model demonstrated an acceptable level of model fit, and it fit better than did a three-factor solution from the literature on depressive disorder. Conclusion : This study's results suggest a difference in the construct of self-reported depressive symptoms in anxiety disorders. These findings also support a dimensional approach to studying anxiety and depression. Further studies may benefit from including comorbid depressive disorder and its influence on anxiety disorders.

• 대한간호학회지
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• 제43권5호
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• pp.587-594
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• 2013

Purpose: The purpose of this study is to provide researchers with a simplified approach to undertaking exploratory factor analysis for the assessment of construct validity. Methods: All articles published in 2010, 2011, and 2012 in Journal of Korean Academy of Nursing were reviewed and other relevant books and articles were chosen for the review. Results: In this paper, the following were discussed: preliminary analysis process of exploratory factor analysis to examine the sample size, distribution of measured variables, correlation coefficient, and results of KMO measure and Bartlett's test of sphericity. In addition, other areas to be considered in using factor analysis are discussed, including determination of the number of factors, the choice of rotation method or extraction method of the factor structure, and the interpretation of the factor loadings and explained variance. Conclusion: Content validity is the degree to which elements of an assessment instrument are relevant to and representative of the targeted construct for a particular assessment purpose. This measurement is difficult and challenging and takes a lot of time. Factor analysis is considered one of the strongest approaches to establishing construct validity and is the most commonly used method for establishing construct validity measured by an instrument.

• 한국산학기술학회논문지
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• 제13권1호
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• pp.107-116
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• 2012

본 연구는 문화관광목적지의 개발접근요인이 각각의 수준 내에서 관광만족에 어떤 영향을 미치는지를 분석하고자 하였다. 연구 자료는 가야역사문화유적지와 경주국립공원을 방문한 관광객들을 대상으로 설문조사를 통하여 수집하였다. 먼저 대상자의 특성에 따른 관광만족도 차이를 분석한 결과 연령, 이용교통 수단, 동반자 형태에 따라 유의한 차이가 있었다. 다음으로 개발접근요인과 관광만족과의 관계를 분석한 결과 관광만족과 관광시장 접근영역(관광 편익, 관광활동 요인), 관광대상 접근영역(관광잠재력, 관광자원가치 요인) 모두 유의한 정적 상관관계를 보였다. 결과적으로 관광만족에 가장 높은 영향을 미치는 개발접근요인은 관광편익 요인으로 나타났으며, 다음은 관광활동, 관광자원가치 요인 순서로 나타났다. 이러한 개발접근요인들이 관광만족을 51.4% 설명하였다. 향후 관광편익, 관광활동, 그리고 관광자원가치 요인의 구성요소를 우선적으로 고려한 문화관광개발접근이 요구되고, 궁극적으로는 관광객의 관광만족을 지속적으로 충족시킬 때 문화관광개발의 효율성을 높일 수 있을 것으로 기대된다.

• Steel and Composite Structures
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• 제50권3호
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• pp.299-318
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• 2024

The main objective of this paper is to compute the far-field acoustic radiation (sound radiation) of functionally graded plates (FGM) loaded by sinusoidally varying point load subjected to the arbitrary boundary condition is carried out. The governing differential equations for thin functionally graded plates (FGM) are derived using classical plate theory (CPT) and Rayleigh integral using the elemental radiator approach. Four cases, segregated on power-law index k=0,1,5,10, are studied. A novel approach is illustrated to compute sound fields of vibrating FGM plates using the physical neutral surface with an elemental radiator approach. The material properties of the FGM plate for all cases are calculated considering the power law indexes. An in-house MATLAB code is written to compute the natural frequencies, normal surface velocities, and sound radiation fields are analytically calculated using semi-analytical formulation. Ansys is used to validate the computed sound power level. The parametric effects of the power law index, modulus ratios, different constituent of FGM plates, boundary conditions, damping loss factor on the sound power level, and radiation efficiency is illustrated. This work is the benchmark approach that clearly explains how to calculate acoustic fields using a solid layered FGM model in ANSYS ACT. It shows that it is possible to asymptotically stabilize the structure by controlling the intermittent layers' stiffness. It is found that sound fields radiated by the elemental radiators approach in MATLAB, ANSYS and literatures are in good agreement. The main novelty of this research is that the FGM plate is analyzed in the low-frequency range, where the stiffness-controlled region governs the whole analysis. It is concluded that a clamped mono-ceramic FGM plate radiates a lesser sound power level and higher radiation efficiency than a mono-metallic or metal-rich FGM plate due to higher stiffness. It is found that change in damping loss factor does not affect the same constituents of FGM plates but has significant effects on the different constituents of FGM plates.

• 대한안전경영과학회지
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• 제13권1호
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• pp.51-58
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• 2011

The uniformity of lighting distribution on the roadway is essential factor for drivers and pedestrians's safety during nighttime in urban streets. Also, the importance of roadside trees is one of the growing concern for better citizens' health and mitigating environmental impact on the urban street. But roadway lightings and roadside trees have different design or planting standards and they are not integrated in the systemic viewpoint for better safety of users during nighttime. The purpose of this study is to propose a simulation approach which assesses lighting quality in the view of illumination uniformity distribution of roadway lighting from design step and consider the layout of roadside trees. For improving lighting quality of roadway, simulation approach is needed for assessing the impact of diverse planting situation of trees and encouraged from beginning of design step for roadway construction.

• Nuclear Engineering and Technology
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• 제42권2호
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• pp.163-174
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• 2010

As pointed out in the OECD BEMUSE Program, when a high computation time is taken to obtain the relevant output values of a complex physical model (or code), the number of statistical samples that must be evaluated through it is a critical factor for the sampling-based uncertainty analysis. Two alternative methods have been utilized to avoid the problem associated with the size of these statistical samples: one is based on Wilks' formula, which is based on simple random sampling, and the other is based on the conventional nonlinear regression approach. While both approaches provide a useful means for drawing conclusions on the resultant uncertainty with a limited number of code runs, there are also some unique corresponding limitations. For example, a conclusion based on the Wilks' formula can be highly affected by the sampled values themselves, while the conventional regression approach requires an a priori estimate on the functional forms of a regression model. The main objective of this paper is to assess the feasibility of the ACE-RSM approach as a complementary method to the Wilks' formula and the conventional regression-based uncertainty analysis. This feasibility was assessed through a practical application of the ACE-RSM approach to the LOFT L2-5 LBLOCA PCT uncertainty analysis, which was implemented as a part of the OECD BEMUSE Phase III program.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.1331-1334
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• 2002

Micropayment is an electronic payment system for small value transaction. It needs to use a little amount of resources, such as communication and computation due to its small value. In other words, the processing cost for the micropayment must be less than the value of the payment. Several kinds of transactions are suitable for micropayment, eg. the purchasing of train tickets or digital newspapers. Since micropayment systems are designed for small-amount payment the key factor for any micropayment system design is believed to be the minimization of resource consumption without compromising the standard security. In this paper, we propose an adaptive agent approach to credit-based micropayment system, which employs the concept of dynamic balancing between the resource consumption and the risk in the system. As a result of the dynamic balancing, our system not only solves the problem of global overspending but also uses fewer amount of resources than existing approaches. Our approach limits the amount of money spent by untrusted customers to all merchants. Thus, our approach provides a boundary of the global overspending. In addition, for trusted customers, our approach requires less scale of communication for verifying authorizations than all existing approaches.

• Structural Engineering and Mechanics
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• 제55권3호
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• pp.605-638
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• 2015

It is intended to perform buckling analysis of steel gabled frames with tapered members and flexible connections. The method is based on the exact solutions of the governing differential equations for stability of a gabled frame with I-section elements. Corresponding buckling load and subsequently effective length factor are obtained for practical use. For several popular frames, the influences of the shape factor, taper ratio, span ratio, flexibility of connections and elastic rotational and translational restraints on the critical load, and corresponding equivalent effective length coefficient are studied. Some of the outcomes are compared against available solutions, demonstrating the accuracy, efficiency and capabilities of the presented approach.