• Journal of Electrical Engineering and Technology
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• 제8권1호
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• pp.124-129
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• 2013

Electro-Mechanical Batteries have important advantages compared with chemical batteries, especially in Low Earth Orbit satellites applications. High speed, slotless, external rotor, brushless DC machines are proposed and used in these systems as Motor/Generator. A simplified analytic design method is given for this type of machines and, the optimization of machine in order to have maximum efficiency and minimum volume and weight are given in this paper. Particle swarm optimization (PSO) is used as the optimization algorithm and the finite element-based simulations are used to confirm the design and optimization process and show less than 6% error in parametric design.

• 조명전기설비학회논문지
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• 제23권11호
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• pp.84-93
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• 2009

In this paper, we propose to study the possibility of using a photovoltaic system combined with a high speed micro-turbine. This hybrid system can work as stand-alone system or grid connected system as it will be a part of a micro-grid. Initially, we propose Matlab/Simulink dynamic models of photovoltaic, micro turbine systems and supercapacitor. Then, we carry out a simulation comparison of the two systems, this is, with supercapacitor and without supercapacitor bank. We show that supercapacitor bank as short-term storage device was necessary to reduce the fast fluctuation of power in the case of sensitive loads. It is verified the simulation results of Matlab/Simulink based hybrid power system represent the effectiveness of the suggested hybrid power system.

• 대한기계학회논문집B
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• 제29권7호
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• pp.795-804
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• 2005

As the flying height of a slider in a hard disk drive decreases, the slider and disk are more likely to come in contact and generate contamination particles. Since particle contamination can cause serious problems including thermal asperity, it must be prevented to increase storage capacity. When particles are generated in a HDD, particles can be charged and have a few number of elementary charges. In this paper, the size distribution of particles and electrical current due to particle according to the disk rotational speed were measured. Also, the average number of elementary charges was calculated from experimental data. SEM images of particles were obtained by using a particle sampler designed in our laboratory.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.677-683
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• 2002

The analytical and experimental studies on aerodynamic flutter instability of rotating disks in information storage devices are investigated. The theoretical analysis uses a fluid-structure model where the aerodynamic force on the rotating disk is represented in terms of lift and damping forces. Based on the analytical approach, it is shown that the backward natural frequency of the disk is equal to that of the case without aerodynamic effect at the flutter onset speed. In post-flutter regions, the natural frequencies are larger than those in vacuum conditions without aerodynamic effect. The analytical predictions on the natural frequencies of rotating disks with/without aerodynamic effect are experimentally verified using a vacuum chamber and ASMO optical disks.

• 한국가시화정보학회지
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• 제9권2호
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• pp.27-33
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• 2011

Supersonic liquid jet discharged from a nozzle has been investigated by using a ballistic range which is composed of high-pressure tube, pump tube, launch tube and liquid storage nozzle. High-speed Schlieren optical method was used to visualize the supersonic liquid jet flow field containing shock wave system, and spray droplet diameter was measured by the laser diffraction method. Experiment was performed with various types of nozzle to investigate the major characteristics of the supersonic liquid jet operating at the range of total pressure of 0.8 from 2.14 GPa. The results obtained shows that shock wave considerably affects the detailed atomization process of the liquid jet and as the nozzle diameter decreases, the shock wave angle and the averaged SMD of spray droplet tends to decrease.

• 한국소음진동공학회논문집
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• 제12권9호
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• pp.661-667
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• 2002

With the increase of storage density, high rotational speed and high access technologies in optical disk drive, mechanical issues, mainly noise and vibration, become critical. Up to now the researches of rubber mount for anti-vibration focused on how to calculate the static and the dynamic stiffness of rubber mount and loaned out consideration of the dimensional tolerance of rubber mount for anti-vibration. This paper presents the effects of dimensional tolerance of rubber mount for anti-nitration on the dynamic characteristics of optical disk drive by finite element analysis and dynamic test. The relation between dimensional tolerance and dynamic characteristics of optical disk drive is observed and discussed.

• 비파괴검사학회지
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• 제31권6호
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• pp.616-625
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• 2011

Ensuring the designed prestress force is very important for the safety of prestressed concrete bridge. The loss of prestress force in tendon could significantly reduce load carrying capacity of the structure. In this study, an automated prestress-loss monitoring system for prestressed concrete girder using PZT-interface and wireless impedance sensor node is presented. The following approaches are carried out to achieve the objective. Firstly, wireless impedance sensor nodes are designed for automated impedance-based monitoring technique. The sensor node is mounted on the high-performance Imote2 sensor platform to fulfill high operating speed, low power requirement and large storage memory. Secondly, a smart PZT-interface designed for monitoring prestress force is described. A linear regression model is established to predict prestress-loss. Finally, a system of the PZT-interface interacted with the wireless sensor node is evaluated from a lab-scale tendon-anchorage connection of a prestressed concrete girder.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2009년도 춘계학술발표논문집
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• pp.435-438
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• 2009

최근 산업체나 연구소에서 사용되는 중대형 데이터 서버에서 발생하는 가장 큰 오버헤드(bottleneck)중의 하나가 바로 저장 시스템이라 할 수 있다. 대표적인 저장 시스템으로서 전통적인 하드디스크 드라이브(HDD)와 더불어 최근 상용화된 Solid State Drive(SSD)가 주목 받기 시작하였다. 본 연구의 목표는 이러한 대용량 HDD 및 고속 SSD에 대하여, 저장 장치로서의 약점을 상호 보완하면서, 장점을 강화하여, 최종적으로 입출력 성능을 극대화할 수 있는 새로운 융합형 데이터 저장 시스템(Hybrid-RAID) 개발이다. Hybrid 저장 시스템 개발을 위한 최근의 기술 연구 및 기반 기술의 설계 및 구현에 대하여 논하며, hybrid-clustering 기술을 제안한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.1998-2014
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• 2016

In recent years, cloud computing services based on smart phones and other mobile terminals have been a rapid development. Cloud computing has the advantages of mass storage capacity and high-speed computing power, and it can meet the needs of different types of users, and under the background, mobile cloud computing (MCC) is now booming. In this paper, we have put forward a new classification-based virtual machine placement (CBVMP) algorithm for MCC, and it aims at improving the efficiency of virtual machine (VM) allocation and the disequilibrium utilization of underlying physical resources in large cloud data center. By simulation experiments based on CloudSim cloud platform, the experimental results show that the new algorithm can improve the efficiency of the VM placement and the utilization rate of underlying physical resources.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.103-110
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• 2005

We present a powerful error control decoder which can be used in all of the commercial DVD systems. The decoder exploits the error information from the modulation decoder in order to increase the error correcting capability. We can identify that the modulation decoder in DVD system can detect errors more than $60\%$ of total errors when burst errors are occurred. In results, fur a decoded block, error correcting capability of the proposed scheme is improved up to $25\%$ more than that of the original error control decoder. In addition, the more the burst error length is increased, the better the decoder performance. Also, a pipeline-balanced RSPC decoder with a low hardware complexity is designed to maximize the throughput. The maximum throughput of the RSPC decoder is 740Mbps@100MHz and the number of gate counts is 20.3K for RS (182, 172, 11) decoder and 30.7K for RS (208, 192, 17) decoder, respectively