• 한국학교수학회논문집
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• 제19권4호
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• pp.357-371
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• 2016

본 연구는 수학적 모델링의 과제공간을 설정하고 이를 기반으로 모델링 과제의 복잡성을 나타내는 평가척도(rating scheme)를 설계하여 예비 수학교사를 대상으로 두 가지의 실험연구 결과를 얻었다. 첫째는 종전의 문제구조를 표현한 문제공간을 발전시켜 모델링 과제에 맞는 과제공간을 설정하고, 모델링 과제의 복잡성을 수치로 나타내는 계량적인 평가척도를 설계하여 의미 있는 타당도를 확인하였다. 둘째는 모델링의 과제 복잡성에 대한 평가척도, 학생 성취수준, 과제 특수 발견 전략의 개수 사이의 일관된 패턴이 있음을 발견하였다.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
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• pp.409-418
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• 2008

본 연구에서는 우리나라 중소기업들의 e-무역상사가 제공하고 있는 무역단계별 서비스 이용정도가 이용만족도와 온라인 수출성과에 미치는 영향을 실증적으로 규명하였다. 130개의 표본기업을 대상으로 한 실증분석 결과 e-무역상사 서비스의 이용빈도가 높을 수록 이용자들의 이용만족도가 높아지고, 이는 해당기업의 온라인 수출성과 제고로 이어졌다. 또한 중소기업의 조직특성은 중소기업의 e-무역상사 서비스 이용만족도와 온라인 수출성과간에 정(+)의 영향관계를 가지는 조절변수로 유의하였다. 이러한 결과는 우리나라 중소기업들이 e-무역상사의 무역단계별 서비스의 적극적인 이용을 통해 온라인 수출성과를 제고할 수 있으며, 이를 위해서는 무엇보다 e-무역상사의 무역단계별 서비스의 고도화와 함께 e-무역상사를 이용하는 중소기업과 e-무역상사에 대한 정책적 지원이 필요하다는 것을 시사하고 있다.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.291-301
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• 2020

This paper aims to investigate the impact of chief executive officer's (CEO) attributes on firms' performance. Specifically, it examines the influence of CEOs' education, professional experience, and tenure on Saudi firms' performance. We look at a sample of 120 listed firms on Tadawul stock exchange from 2014 to 2017. Data on financial and accounting variables are obtained from the annual reports of the selected companies. We follow the existing empirical literature and use a panel model and formulate three different equations using the GMM estimator. Findings prove that CEO educational background does matter. In particular, companies employing CEOs with business administration, economics, finance, or accounting degree will perform outstandingly better. Similarly, stock performance gets improved when the CEO has a postgraduate qualification, i.e., when the CEO holds an MBA, a master, or a PhD degree. Besides, results reveal that executives who have an experience in a related field will positively affect the firm's performance. Finally, evidence shows that high CEOs tenure improves corporate performance. Overall, these findings demonstrate that executives' attributes are key factors that would explain differences in Saudi firms' performance. These results would help shareholders to make the right decision in selecting CEOs to manage the company.

• International Journal of Control, Automation, and Systems
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• 제4권2호
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• pp.227-235
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• 2006

For a sophisticated humanoid that explores and learns its environment and interacts with humans, anthropomorphic physical behavior is much desired. The human vision system orients each eye with three-degree-of-freedom (3-DOF) in the directions of horizontal, vertical and torsional axes. Thus, in order to accurately replicate human vision system, it is imperative to have a simulator with 3-DOF end-effector. We present a 3-DOF anthropomorphic oculomotor system that reproduces realistic human eye movements for human-sized humanoid applications. The parallel link architecture of the oculomotor system is sized and designed to match the performance capabilities of the human vision. In this paper, a biologically-inspired mechanical design and the structural kinematics of the prototype are described in detail. The motility of the prototype in each axis of rotation was replicated through computer simulation, while performance tests comparable to human eye movements were recorded.

• 품질경영학회지
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• 제31권4호
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• pp.1-18
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• 2003

Quality is a critical competitive factor in today's environment because of the impact of quality on costs and delivery. Many companies regard quality as a key concept of company strategy in order to achieve the competitive edge. Measuring and reporting quality cost is the first step in quality management program. The supposition of quality cost model is that investment in prevention activities will bring rewards from reduced failure costs, and that further investment in prevention activities will show profits from reduced appraisal costs. In this study, the degree of quality cost deviation is conceptualized. This means a deviation between the ideal and present ranking in the amounts of quality cost categories. This study analysed that the effect of its deviation on quality management activity and performance variables. However, there are no difference in these variables. The major reason is that most of companies are endeavoring for quality management but operating quality cost system unsystematically. The review against a prevention and appraisal activity is necessary.

• 소음진동
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• 제11권1호
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• pp.49-56
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• 2001

In this paper, two plant models, of which one is newly developed and the other one is the conventional one, of the focus servo system of DVD drive are presented and a two-degree-of freedom controller consisted of Inverse dynamics feedforward and LQG/LTR feedback controller is designed. The newly developed plant model is used to design the feedforward controller and the conventional model is used for the design of feedback controller. The output of newly developed model is the displacement of objective lens and the output of conventional model is the focus error of the DVD focus servo system. The displacement of the objective lens is estimated by the dynamics model of the DVD focus servo system. The disturbance rejection performance of the two-degree-of freedom controller is compared with that of an LQG/LTR one.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 추계학술대회논문집
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• pp.159-167
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• 2000

During the operation of crane system in the container yard, it is necessary to control the crane trolley position so that the swing of the hanging container is minimized. Recently an automatic control system with high speed and rapid transportation is required. Therefore, we designed a controller to control the crane system with disturbances and weight change. In this paper, we present the neural network two degree of freedom PID controller to control the swing motion and trolley position. Then we executed the computer simulation to verify the performance of the proposed controller and compared the performance of the neural network PID controller with our proposed controller in terms of the rope swing and the precision of position control. Computer simulation results show that the proposed controller has better performances than neural network PID with disturbances.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.421-421
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• 2000

In this paper, robust two-degree-of-freedom controller for satellite antenna system which tracks reference signal is designed. Two-degree-of-freedom controller consists of a prefilter and a feedback controller to solve trade-off between robust stability and command response. The feedback controller is designed from specifications like stability, disturbance rejection and robustness via H$_{\infty}$ design technique. In the sequel, H$_2$ optimal prefilter is introduced to improve the command response. This suggests a two-step design, with different types of performance specifications at each stage. In practical problems, this may easily lead to a prefilter of unacceptably high order. In order to avoid high order prefilter we use a particular structure in which both the prefilter and the feedback controller share the same dynamics. H$_2$-prefilter technique proposed in this paper is verified by simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.670-672
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• 1995

This paper deals with the robust two-degree-of-freedom multivariable control system using $H_{2}/H{\infty}$optimization method which can achieve the robust stability and the robust performance, simultaneously. The feedback controller can obtain the robust stability property. The feedforward controller can obtain the robust performance property under modelling error. The robust two-degree-of-freedom multivariable control system is applied to the nonlinear multivariable boiler-turbine system. The validity of the proposed method is verified though being compared with LQG/LTR design method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2210-2213
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• 2008

In the present study, effects of degree of confinement on heat transfer characteristics of a micro-scale slot jet impinging on a heated flat plate are experimentally investigated. The effects of Reynolds numbers (Re = $1000{\sim}5000$), lateral distances (x/B = $1{\sim}10$), nozzle-to-plate spacings (Z/B = $1{\sim}20$), and degree of confinement ($B_c$/B = 3, 48) on the Nusselt number are considered. The results show that the effects of the degree of confinement on the cooling performance of the micro-scale impinging slot jet are significant at lower nozzle-to-plate spacings and higher Reynolds numbers. In addition, it is shown that the cooling performance of the micro-scale unconfined slot impinging jet is 200% higher than that of the micro-scale confined slot impinging jet.