• 제어로봇시스템학회논문지
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• 제10권12호
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• pp.1202-1209
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• 2004

This paper presents a design methodology of a Digital Servo Signal Processor for high speed CD-RW drive systems. The proposed Digital Servo Signal Processor enables us to develop CD-related systems for the very high speed applications and is one of the key components of the CD-RW systems. The proposed center compensation servo control is newly built for an actuator shaking due to the fast response of a step motor when it jumps to a long distance. A control method compensating for eccentricity of a disc is implemented for operating robustly at a higher rotational speed. This servo mechanism is more size efficient and less power consumed because it is implemented using a ARM7 embedded processor and hardware digital filters. Furthermore, it is convenient to upgrade firmware for the future required functions. From experimental results, we can see that the performance of the control system is improved greatly. The proposed servo algorithm shows a shorter setting time including a pull-in time and a faster access time. It can be applied easily to the DVD-ROM and the DVD-RAM which have the same optical structure.

• 수산해양기술연구
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• 제26권2호
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• pp.204-212
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• 1990

The SMC composite, now being considered in certain structural applications, is anticipated to experience repeated loading during service. Thus, understanding of the fatigue behavior is essential in proper use of the composite material. In this paper, using the SMC composite composed of E-glass chopped strand and unsaturated polyester resin three point bending fatigue tests are carried out to investigate the fatigue crack propagating behavior under various cyclic stresses and fatigue damage of various microcrack forms. The following results are obtained from this study; 1) Most of the total fatigue life of the SMC composite is consumed at the initial extension or the growth of the macroscopic crack. 2) A Paris' type power-law relationship between the crack propagation rate and stress intensity factor range is obtained, and the value of material constant m is much higher (m=9~11)than that of other metals. 3) In case of high cyclic stress the fatigue damage show high microcrack density and short crack length, but in case of low cyclic stress does it vice versa. 4) Fatigue damage is characterized by microcrack density, crack length and distribution of crack orientation.

• 한국정밀공학회지
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• 제32권4호
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• pp.353-358
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• 2015

Energy consumption reduction has become an important key word in manufacturing that can be achieved through the efficient and optimal use of raw materials and natural resources, and minimization of the harmful effects on nature or human society. The successful implementation of this concept can only be possible by considering a product's entire life cycle and even its disposal from the early design stage. To accomplish this idea with milling, minimum quantity lubrication (MQL) strategies and cutting conditions are analyzed through process modeling and experiments. In this study, a model to predict the cutting energy in the milling process is used to find the cutting conditions, which minimize the cutting energy through a Kriging meta-modeling process. The MQL scheme is developed first to reduce the amount of cutting oil and costs used in the cutting process, which is then employed for the entire modeling and experiments.

• Ocean Systems Engineering
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• 제3권4호
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• pp.275-294
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• 2013

Side-by-side offloading operations are widely utilized in engineering practice. The hydrodynamic interactions between two vessels play a crucial role in safe operation. This study focuses on the coupled effects between two floating bodies positioned side-by-side as a shuttle tanker-FPSO (floating production, storage and offloading) system. Several wave directions with different side-by-side distances are studied in order to obtain the variation tendency of the horizontal hydrodynamic coefficients, motion responses and mean drift forces. It is obtained that the coupled hydrodynamics between two vessels is evidently distinguished from the single body case with shielding and exaggerating effects, especially for sway and yaw directions. The resonance frequency and the peak amplitude are closely related with side-by-side separation distance. In addition, the horizontal hydrodynamics of the shuttle tanker is more susceptible to coupled effects in beam waves. It is suggested to expand the gap distance reasonably in order to reduce the coupled drift forces effectively. Attention should also be paid to the second peaks caused by hydrodynamic coupling. Since the horizontal mean drift forces are the most mainly concerned forces to be counteracted in dynamic positioning (DP) system and mooring system, prudent prediction is beneficial in saving consumed power of DP system and reducing tension of mooring lines.

• 한국통신학회논문지
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• 제32권3C호
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• pp.249-255
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• 2007

일반적으로, H.264/AVC 압축 표준에서 CAVLC 복원은 많은 양의 메모리 액세스를 필요로 한다. 이러한 메모리 액세스는 비디오폰 및 DMB와 같은 응용 서비스에 있어서 파워 소모 면에서 중요한 문제로 인식된다. 이를 해결하기 위하여 본 논문에서는 CAVLC의 구문요소중 하나인 coeff-token에 대한 효과적인 복호화 방식을 제안한다. 먼저 중복 액세스를 제거하기 위하여 바이트 단위로 구성되는 새로운 코드워드를 정의한다. 그리고 이를 기초로 가변길이 부호어 테이블을 재구성한 후 효과적인 메모리 액세스 기법을 제시한다. 모의 실험은 화질 저하 없이 제안 방식에서 약 85% 정도의 메모리 액세스가 절약됨을 보여준다.

• 한국인터넷방송통신학회논문지
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• 제14권6호
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• pp.183-188
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• 2014

최근 모바일 컴퓨팅과 센서 기술의 급속한 발전과 더불어, 유비쿼터스 센서 네트워크(USN) 관련 응용 기술이 다양한 관련 기술과의 융합을 통해 활발하게 확산되고 있다. 이러한 응용들은 대부분 다양한 센서를 통한 주변의 상황정보를 이용하여 적절하게 제어하고 시스템을 모니터링 하는데 그 목표를 두고 있다. 하지만 센서들로부터 발생하는 데이터들은 큰 용량과 다양성으로 인해 정확하고 유연한 통제나 모니터링을 하기가 쉽지 않은 상황이다. 본 논문에서는 센서 네트워크를 통해 센싱된 데이터를 기반으로 상황정보를 적절하게 반영하여 유연하게 시스템을 제어하고 모니터링할 수 있도록 USN에서의 퍼지 로직 기반 중앙 통제시스템을 설계하고 구현하였다. 제안한 시스템은 실제 테스트 베드를 구축하여 운영 중인 USN기반 가로등 제어 시스템에 적용하여 그 성능을 모의실험을 통해 가로등의 소비 전력량에 대한 에너지 절감 영향을 비교 평가하였다.

• Coupled systems mechanics
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• 제2권1호
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• pp.23-51
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• 2013

An analytical algorithm for the estimation of the resistance forces exerted on the dipper of a cable shovel and the specific energy consumed in the cutting-loading process is presented. Forces due to payload and to cutting of geomaterials under given initial conditions, cutting trajectory of the bucket, bucket's design, and geomaterial properties are analytically computed. The excavation process has been modeled by means of a kinematical shovel model, as well as of dynamic payload and cutting resistance models. For the calculation of the cutting forces, a logsandwich passive failure mechanism of the geomaterial is considered, as has been found by considering that a slip surface propagates like a mixed mode crack. Subsequently, the Upper-Bound theorem of Limit Analysis Theory is applied for the approximate calculation of the maximum reacting forces exerted on the dipper of the cable shovel. This algorithm has been implemented into an Excel$^{TM}$ spreadsheet to facilitate user-friendly, "transparent" calculations and built-in data analysis techniques. Its use is demonstrated with a realistic application of a medium-sized shovel. It was found, among others, that the specific energy of cutting exhibits a size effect, such that it decreases as the (-1)-power of the cutting depth for the considered example application.

• 제어로봇시스템학회논문지
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• 제1권2호
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• pp.127-134
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• 1995

For use in patients with severe forms of heart disease for which no surgical repair is possible, development of artificial hearts has many importance in point of economics, medical and industrial applications. To provide a sufficient cardiac output to the physiological demands of circulatory systems is the objective of control systems for an electromechanical artificial heart, which is based on the stable controller design for the motor in the artificial heart. In this paper, an implantable microcontroller-based brushless DC motor control system with the implantability, reliability, and stability is introduced. The developed control system for the artificial heart has the following advantages: (1) It is possible to be implanted in a body by realizing the fundamental functions such as a motor speed detection, proportional-intergral control, timer, and PWM generation through a software programming. (2) Thus, the power consumed in the controller is reduced. (3) The reliability and stability are improved through the reduction of electronic parts and line connetions at the controller. The performance of the artificial hearts and control system developed was evaluated through a series of mock circulatory experiments and a reliability test for one and half years. A sheep with the artificial heart and control system was survived for three days.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.522-528
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• 2012

Currently, the energy consumption of electric lighting in an office building is accounted for more than 30% of the total energy consumption. In order to reduce the energy consumed by the indoor lighting, the daylight as a natural energy resource can play an important role in energy savings. The daylight can have positive impacts on improvement of work efficiency and productivity, and also make people feel more psychologically stable. Moreover, by using the daylight, we can definitely reduce the energy consumption in office buildings. Thus, the purpose of this study is to determine the LED dimming ratio depending on the ratio by calculating the amount of artificial illumination required according to the change of daylight by using the light simulation software that can quantify and visualize the performance of daylight. As a result, the energy savings could be obtained up to 30%.

• 한국태양에너지학회 논문집
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• 제29권6호
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• pp.14-21
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• 2009

The demand and installation for photovoltaic system(namely, PV) has grown steadily in Korea. However, the PV system has a various economic viability according to the PV system characteristic variables such as inverter efficiency, miscellaneous power conditioning losses, azimuth and slope of PV array, PV tracking mode, and so on. The other variables are the monthly consumed electric energy and economic related factor such as initial cost, government subsidy, maintenance cost, inflation rate, energy cost escalation rate, discount rate, etc. Therefore, this study is to present economic evaluation of PV system with those concerned factors by calculating internal rate of return, year-to-positive cash flow and net present value indices.