• Proceedings of the Korean Information Science Society Conference
• /
• 2000.10c
• /
• pp.27-29
• /
• 2000

마이크로 프로세서의 동작 속도와 디스크 액세스 속도의 성능 차이는 컴퓨터 시스템의 성능을 제한하는 중요한 요인 주의 하나로 지적되고 있다. 이러한 격차를 줄이는 기술로 디스크 캐쉬의 운영이 연구되어 왔고 디스크 캐쉬 성능 개선 방법으로 선인출이 널리 연구되어 왔다. 본 논문에서는 디스크 드라이브 상에 구현된 캐쉬에서 디스크 요청에 대한 성격적 유형을 힌트로 이용한 선인출 적용방법을 제안하고, 제안된 방법의 유효성은 시뮬레이션 방식으로 입증하였으며 적응적으로 변경된 선인출 적용 방법이 성능의 개선을 이룰 수 있음을 보였다.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.277-280
• /
• 2006

Using yaw system, Wind turbine can face the wind to make it's electricity generating maximum and to make it's fatigue load minimum. So, in wind turbine design process, selecting optimum yaw system is very important work. In this paper, the yaw moments on yaw bearing, yaw drive and yaw brake were calculated. and From the result, the duty cycle was obtained. At last, using this duty cycle, optimum yaw system is selected.

• Journal of Applied Reliability
• /
• v.14 no.4
• /
• pp.213-219
• /
• 2014

Wind turbine, which is attracting part of the renewable energy and is researching continuously, is going to be large size for high efficiency. There is a yaw system rotating the nacelle, weighted about 600 tons, to be perpendicular with the wind direction blowing in the large wind turbine. The wind turbine is focusing on the reliability improvement because working environment effect is bigger than any other points and specially, the reliability improvement of the yaw drive is required by the customer because it is the key component of the wind turbine. Because of this, the establishment of criteria for yaw drive is required because yaw drive system is the part of the wind turbine closely related with ensuring the reliability. So, this study did the failure analysis of the yaw drive system, which is consisted with 10 sets of yaw drives through researching and analyzing the site conditions. Also this study designed the life test method based on the failure analysis and working condition of the yaw drive. To design the accelerated life test of the yaw drive, this study reviewed the torque, lubrication condition, and frequency of use and etc. Finally, this selected the torque as the acceleration factor which is affected mainly to the system and also, the test equipment was developed based on the requirement of the life and performance test.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.297-299
• /
• 2008

기술 개발과 산업화에 있어 현대 사회에서는 특허의 중요성이 점점 커지고 있다. 이 점은 풍력발전기 분야에서 역시 예외가 아니다. 따라서 기술 개발 이전에 해당 기술 분야에 대해 특허를 조사하고 특허맵을 구축하는 것이 필요하다. 또한 특허맵의 구축을 통하여 풍력 발전기 분야의 기술 개발 동향 및 경쟁 업체의 기술 개발 현황 등에 대하여 파악이 가능하다. 본 논문에서는 풍력발전기의 레이아웃과 드라이브 트레인, 그리고 요 시스템에 대하여 해당 특허에 대한 조사 및 특허맵에 대하여 이야기 하고자 한다.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.221-221
• /
• 2003

본 연구에서는 스핀밸브 다층박막에서 교환 바이어스에 영향을 끼치는 요인 중 하나인 강자성층과 반강자성층사이의 접합 계면에서의 표면 거칠기 [1,2]를 줄이기 위해 현재 반도체 공정에 사용되고 있는 이온빔 에칭 장비를 사용하여 스핀 밸브 다층박막의 씨앗층 에칭에 따른 교환 바이어스를 알아보고자 하였다. 스핀밸브 구조는 강자성층/비자성층/강자성층의 기본구조를 갖는데 이중 하나의 강자성층의 스핀방향이 반강자성층에 의해 고정되는 구조[3]로써 이러한 고정 효과를 교환 바이어스(exchange bias)라 부른다. 교환 바이어스(exchange bias)현상은 강자성과 반강자성의 접합계면에서 강한 상호 교환결합력에 의해 나타나는 현상으로 이러한 교환 바이어스 특성은 하드드라이브의 고밀도 자기헤드소자 및 비휘발성 자기 메모리소자에 응용되어 기존의 자기저항 소자의 특성을 크게 향상시킬 수 있게 되었다.

• Journal of Drive and Control
• /
• v.21 no.1
• /
• pp.16-21
• /
• 2024

The yaw gearbox is a key device in a wind power generator that improves power generation efficiency by rotating hundreds of tons (400 to 600 tons) of nacelle so that the blade reaches 90 degrees in the wind direction. Recently, installation sites have been advancing from land to sea as they have become super-large at (8-12) MW to increase the economic feasibility of wind power generators and utilize excellent wind resources, and the target life of large wind power generators is 25 to 30 years. The yaw gearbox of 6 to 12 sets is installed in a very complex place inside the nacelle on the tower with parallels, and it is important to secure the reliability of the yaw gearbox because if a failure occurs after installation, it costs tens to hundreds of times the price of a new product to restore. In this study, equivalent loads were calculated by analyzing failure mode and field data, accelerated life test conditions were established, and a test device was constructed to perform the accelerated life tests and performance tests to ensure the reliability of the gearbox.

• Journal of Drive and Control
• /
• v.14 no.2
• /
• pp.16-22
• /
• 2017

This paper presents the algorithm of an adaptive model-free-control-based steering control for multi-axle all-terrain cranes for which the recursive least squares with forgetting are applied. To optimally control the actual system in the real world, the linear or nonlinear mathematical model of the system should be given for the determination of the optimal control inputs; however, it is difficult to derive the mathematical model due to the actual system's complexity and nonlinearity. To address this problem, the proposed adaptive model-free controller is used to control the steering angle of a multi-axle crane. The proposed model-free control algorithm uses only the input and output signals of the system to determine the optimal inputs. The recursive least-squares algorithm identifies first-order systems. The uncertainty between the identified system and the actual system was estimated based on the disturbance observer. The proposed control algorithm was used for the steering control of a multi-axle crane, where only the steering input and the desired yaw rate were employed, to track the reference path. The controller and performance evaluations were constructed and conducted in the Matlab/Simulink environment. The evaluation results show that the proposed adaptive model-free-control-based steering-control algorithm produces a sound path-tracking performance.

• Journal of Technology Innovation
• /
• v.23 no.1
• /
• pp.1-36
• /
• 2015

The purpose of this research is to find individual user's preference for cloud storage service such as Daum Cloud, Naver N-Drive, GoogleDrive, Dropbox, SkyDrive and iCloud. Through literature reviewed and pilot tests, 6 attributes of cloud storage service (storage capacity, perceived cost, collaboration, accessibility, social influence and perceived security) were selected and all 6 attributes had significant effects on the preference of cloud storage service by conjoint analysis. The results shows that the user's willingness to pay is estimated 10,553 won for the free storage, 4,646 won for the function for mobile accessibility, and 2,443 won for more reliable cloud computing service provider. This study has significance to apply conjoint analysis with economic, technological, and environmental factors to cloud storage service (SaaS) and shed light on policy promotion of next generation of cloud computing ecosystem by user perception with willingness to pay on the storage service.