• 소음진동
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• 제2권3호
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• pp.173-180
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• 1992

A boundary control method that controls interior state by actively controlling the boundary conditions in boundary value problems is proposed for the vibration control of flexible beam by using piezoelectric actuators. The governing equations are derived based on the Euler beam theory and the reduced order model is obtained by modal truncation. The spillover effects caused by the uncontrolled high frequency modes are analyzed and the method selecting a suitable sensor location is also proposed. The lag compensator in digital form is realized by using a microcomputer and its peripheral devices. The efficiency of the proposed control scheme is demonstrated experimentally and compared with the simulation results.

• Nuclear Engineering and Technology
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• 제26권1호
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• pp.32-40
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• 1994

중기발생기의 수위조절과 관련하여 최적제어이론을 이용한 디지탈 제어시스템을 설계하였다. 우선 급수변을 일차 지연함수로 취급하여 전체 시스템에 포함시킴으로써 보다 실제에 가까운 시스템이 되게 하였다. LQ 방법을 이용하여 급수변의 작동 및 요구신호량과 급수출력과의 차이를 최소화시킬 수 있는 최적 이득상수를 결정하였으며, 아울러 저출력에서의 급수유량 측정이 불확실함을 고려하여 급수신호에 대한 칼만 관측기를 설계하였다. 그리고 전출력 구간에서 일정한 안정여유도를 유지시킬 수 있는 가변상수 디지탈 제어기를 설계하였다. 이러한 제어시스템은 보다 현실적인 상황을 반영하고 있으며 저출력에서 급수와 반대현상을 보이는 중기발생기의 동특성에도 불구하고 만족할만한 제어특성을 보이고 있다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2004년도 춘계공동학술대회 논문집
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• pp.331-334
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• 2004

There are many researches investigating a causal relationship among service performance level, customer satisfaction, and customer loyalty. It is believed that a high service performance level increases customer satisfaction, which again has a significant effect on customer loyalty and profitability. The premise in this work is that the effect of customer satisfaction on customer loyalty may be time-lagged. This paper aims to model a causal relationship among service performance level, customer satisfaction, and customer loyalty with such a time-lag consideration. This study is conducted on the very high-speed digital subscriber lines service, which is a highly advanced high-speed internet service, and the results also be discussed.

• 디지털융복합연구
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• 제16권11호
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• pp.45-55
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• 2018

본 연구에서는 소비자단체의 공간적 분포와 그 특성을 살펴보고, 소비자단체의 발전 방안을 모색하는 데 필요한 근거 자료를 마련하고자 하였다. 이를 통해 지역을 기반으로 한 소비자단체가 소비자문제를 보다 효과적으로 해결할 수 있는 구체적인 방안을 제안할 수 있기 때문이다. 본 연구에서는 11개 소비자단체, 815개소 지부 및 지회 자료를 수집하여 국지적 자기상관과 공간시차모델을 활용하여 분석하였다. 첫째, 소비자단체의 공간적 분포는 지리적인 특성에 따른 패턴을 찾기 어려웠다. 둘째, 소비자단체는 인구와 사업체 수가 많고 면적이 큰 지역일수록 더 많이 분포하고 있는 것으로 나타났다. 셋째, 소비자단체의 공간적 분포는 소비자상담 건수와 비교할 때, 소비자단체의 수요와 공급 간 불일치가 발생한다는 것을 나타낸다. 후속 연구에서는 소비자단체의 활동에 관한 질적 자료를 보충하여 분석함으로써, 소비자단체의 구체적인 발전방안을 지속적으로 모색할 필요가 있다.

• 디지털산업정보학회논문지
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• 제9권2호
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• pp.121-137
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• 2013

Now days, firm's technology capability is recognized as important factor to forecast and to evaluate firm's business performance. There are many efforts to develop useful indicators by applying patent information that includes concrete description about technology. Many previous studies analyzed relationship between patent indicators and firm's performance. But they didn't consider time gap between a point of firm's invention activity and a point of firm's performance improvement. They didn't considered a character of industrial fields either. To overcome these limitations, we selected IT industry for target analysis industry. Time-series patent data and financial data from 41 American IT firms between 2000 and 2011 were used to analyze. In this study, We empirically analyzed subsequent effect of patent indicators on firm's business performance by using correlation analysis and regression analysis.

• 정보화정책
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• 제28권4호
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• pp.3-18
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• 2021

'정보격차'는 공유성, 이전성 및 복제성과 같이 평등화에 기여함직한 정보의 내재적 속성에 반하는 정보화 시대의 예기치 않은 역기능으로 간주되어 학술적으로나 사회적으로 주목받아 왔다. 더구나 그것이 정보의 불균등한 분포로 그치는 것이 아니라 경제적, 사회적, 문화적 불평등과 맞물려 사회체계의 안정성을 해치는 요소가 될 수 있다는 문제의식은 정보격차에 관한 연구를 촉진시켜 왔다. 따라서 본 논문에서는 (1) 1970년 이후 국내외에서 수행된 정보격차 연구들을 총괄적으로 일람하고, (2) 상론할 가치가 높다고 판단되는 연구물들을 섭렵해 정보격차 담론의 성과와 한계를 검토한 후, (3) 정보격차 연구의 새로운 과제와 방향을 탐지하였다. 그 결과, 학계 안팎에서 의미 있는 성과가 축적되어 왔음이 확인되었으나, 순수연구와 정책연구 간의 괴리 및 시대 변화에 뒤진 '지적 지체' 현상이 한계점으로 드러났다. 아울러 지능정보화 시대에는 운용격차, 선정격차 및 증강격차가 정보격차 연구의 새로운 의제로 대두할 것임을 밝힐 수 있었다.

• 제어로봇시스템학회논문지
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• 제19권4호
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• pp.285-289
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• 2013

In switching from the track-seeking or track-jumping control mode to track-following control mode in hard disk drives or optical disk drives, initial values of the feedback controller are tuned to improve the transient response. In general, all the initial values of the controller have been compensated for this purpose. In this paper, by partially compensating initial values of digital controllers, we achieve a good performance of the transient response. In the proposed method for IVC (Intial Value Compensation), LMIs (Linear Matrix Inequalities) are used, which includes conditions for improving the performance of the transient response such as reducing a tracking error and control efforts. We obtain optimal initial values of the controller by solving an optimization problem with constraints represented by only one LMI. Although initial values of the controller are partially compensated, we can show that not only a sufficient performance of the transient response is obtained but also control efforts are diminished. The feasibility of the method is verified by simulation studies.

• International Journal of Internet, Broadcasting and Communication
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• 제14권1호
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• pp.105-115
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• 2022

The platform for displaying cars has been changing with the times. From the popularity of paper media to the rise of computer graphics, the improvement of technology has brought more space and possibilities to the automotive industry. Yiming Zhong proposed the workflow of car configurator through Unreal Engine 4 to implement the basic functions of configuration in 2021, according to Yiming Zhong's final presentation, there is still room to improve the realism of graphics and functionality of the car configurator. Therefore, in this paper we propose to upgrade the car shaders and lighting environments according to the real-world physics and add multi-scenes switching function to car configurator. However the multi-scenes switching function also brings a large amount of data, which leads to the problem of display lag. At the end of the paper, we use the level of details(LOD) process to reduce the amount of data for real-time computing in Unreal Engine 4 and the increase of frames per second(FPS) values verifies the feasibility of our optimization solution.

• 한국정밀공학회지
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• 제19권2호
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• pp.203-212
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• 2002

Active magnetic hearings allow much high surface speed than conventional ball bearings and therefore greatly suitable for high speed cutting. This paper describes a design and test of an active magnetic bearing system with 16-pole radial magnets. The spindle is originally designed for a CNC lathe and driven by outer motor with 5.5 kW power and maximum speed 10,000 rpm. Considering static load condition and geometric restrictions, radial magnet is designed 16-pole type for smaller outer diameter of the spindle system. Dynamic system characteristics such as natural frequency, critical speed, stiffness, damping and system stabilities are simulated with a rigid rotor model including direct feedback controller. The designed spindle system is realized with digital PIDD controller to compensate phase lag of PWM amplifier and magnet coils. With levitation and step response experiment the control system characteristics are tested, and the spindle is rotated up to 10,000 rpm stab1y.

• Tribology and Lubricants
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• 제11권5호
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• pp.99-107
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• 1995

This paper reported research results to develop an algorithm of on-lin evaluation of surface profiles and roughness generated by turning. The developed module consisted of computer simulation of surface profiles using mechanism of cutting mark formation and cutting vibrations, and online measurement of cutting vibrations. The relative cutting vibrations between tool and worpkiece were measured through an inductance pickup at the rate of one sample per rotation of the workpiece. The sampling process was monitored using an encoder to avoid conceling out the phase lag between waves. The digital cutting signals from the Analog-to-Digital converter were transferred to the simulation module of surface profile where the surface profiles were generated. The developed algorithm or surface generation in a hard turning was analyzed through computer simulations to consider the stochastic and dynamic nature of cutting process. Cutting tests were performed using AISI 304 Stainless Steel and carbide inserts in practical range of cutting conditions. Experimental results showed good correlation between the surface profiles and roughness obtained using the developed algorithm and the surface texture measured using a surface profilemeter. The research provided the feasibility to monitor surface characteristics during tribelogical tests considering wear effect on surface texture in machining.