• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.316-323
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• 2012

In order to meet the service life of planetary gearbox, a planet bearing, well known as the component with the highest failure rate, is designed. To predict the bearing fatigue life, ISO standard(ISO/TS 16281) is used, and the design parameters of the bearing are optimized using a parametric method. The whole planetary gearbox model is developed using a commercial software to calculate loads acting on planet bearings accurately. The results state that the designed bearings are satisfied with the life of 15,000hours, and the bearings that consist of 22rollers of 58mm have 1.6times longer life and better load sharing relatively than 22rollers of 28.5mm. Also, the increase in preload of taper roller bearings on the output pinion shaft prolongs the life of planet bearings regardless of roller's length.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.536-537
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• 2008

최근 홈 네트워킹 기술과 연동된 가전제어 및 서비스에 대한니즈가 증대�� 있어 다양한 디지털 가전기기가 개발되고 있다. 특히 국내외적으로 많은 홈 네트워크 관련 제품들이 생산되고 있으며 이는 궁극적으로 이기종 네트워크 환경에서 유무선 통신의 구된 없이 다양한 기기를 네트워크에 접속할 수 있는 서비스를 제공한다. 기존 중 저속 전력선 모뎀의 경우 홈 네트워크에서 전력선으로 들어오는 신호를 수신하기 위해 전력소모가 가장 많은 Main Processor에서는 항상 Wake-On 상태를 유지하고 있다. 하지만 중 저속 전력선 모뎀의 송수신을 관장하는 Main Processor를 보게 되면 크게 통신 프로토콜을 관장하는 Main CPU와 실제 전력선 신호 송수신을 관장하는 PLC Core로 나뉠 수 있다. 홈네트워크상에 전력선으로 들어오는 신호를 수신하기 위해서는 PLC Core는 항상 Wake-On 상태를 유지해야 하지만 Main CPU의 경우는 전력소모를 최소화하기 위해 Idle 상태를 유지하더라도 Host Controller와의 Stand-by & Wake On 신호와 인터럽트 발생기능을 이용하게 되면 전력선 통신에 문제가 없이 대기모드를 지원하는 저전력 전력선 통신 모뎀 개발이 가능하다. 이에 본 연구에서는 저전력 대기모드를 지원하는 전력선 통신 모뎀 개발에 관한 연구를 하고자 한다.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.77.1-77.1
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• 2016

We investigate the properties and detection conditions for the planetary caustic perturbation of close-separation planets. To find the properties of the planetary caustic perturbation, we construct deviation maps by subtracting the single-lensing magnification of the lens star from the planetary lensing magnification for various lensing parameters. We find that each deviation area of the positive and negative perturbations disappears at the same normalized source radius according to a given deviation threshold regardless of mass ratio but disappears at a different normalized source radius according to the separation. We also estimate the upper limit of the normalized source radius to detect the planetary caustic perturbation. We find simple relations between the upper limit of the normalized source radius and the lensing parameters. From the relations, we obtain an analytic condition for the detection limit of the planet, and which show that we can sufficiently discover a planet with the mass of sub-Earth for typical microlensing events. Therefore, we expect to add the number of low-mass planets in the next-generation microlensing experiments and conclude that our detection condition of the planet can be used as a important criteria for maximal planet detections considering the source type and the photometric accuracy.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.495-496
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• 2007

본 논문에서는 전력선 통신 모뎀에 필수적으로 사용하고 있는 AC 커플러의 대기모드 상태에서의 저전력 AC 커플러 개발에 관한 것으로, 전력선 통신(PLC : Power Line Communication) 모뎀은 디지털 가전기기를 위한 지능형 홈 네트워크 구축은 물론 원격검침 등의 각종 자동화 시스템에 활발하게 적용됨에 따라 저전력 대기모드 지원의 필요성이 요구되고 있다. 이러한 요구를 충족시키기 위해서 본 논문에서는 전력선 통신 모뎀에 필수적으로 사용하고 있는 AC 커플러의 대기모드 상태에서의 저전력 AC 커플러를 위해 1차측 AC 커플러를 송신측과 수신측으로 분리하여 설계하였다. 또한 수신 커플링 회로의 경우 현재 이용되고 있는 커플링 회로의 차단주파수를 10kHz에서 전력선 모뎀의 캐리어주파수에 영향을 미치지 않는 70kHz 고역 통과필터로 설계한다. 본 논문에서는 다양한 Simulation 및 실험을 통하여 제안된 AC 커플러가 기존 전력선 통신 모뎀과 동일한 성능을 유지하면서, 대기시 소모되는 소비전력을 크게 감소시켜, 기존 전력선 모뎀에 제안된 AC 커플러로 대치할 수 있음을 실험을 통해 규명하고 입증하였다.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.606-621
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• 2004

A dynamic analysis using a hybrid finite element method was performed to characterize the effects of a number of manufacturing errors on bearing forces and critical tooth stress in the elements of a planetary gear system. Some tolerance control guidelines for managing bearing forces and critical stress are deduced from the results. The carrier indexing error for the planet assembly and planet runout error are the most critical factors in reducing the planet bearing force and maximizing load sharing, as well as in reducing the critical stress.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.78.1-78.1
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• 2010

We obtained the spectra of 93 Planet host stars and 73 normal field stars in F, G, K type using BOES at BOAO. We measured the equivalent width of Fe and 13 elements lines using the automatic EW measurement program, TAME(Tools for Automatic Measurement of Equivalent-widths) and estimated the abundances by synth and abfind driver of MOOG code. Since the absence of planets in the normal field stars cannot be "completely" proved, this work focused on the chemical abundances and planet properties of planet host stars, which have the massive planets close to the parent star relatively. We carried out an investigation for the difference of abundances between stars with "Hot Jupiter" and normal field stars with no known planets. We examined the chemical composition of 12 elements, such as Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni by EW measurements, and the S abundances were estimated using synthetic spectrum.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1597-1606
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• 2003

Static analysis using hybrid finite element(FE) method has been applied to characterize the influence of position, runout and thickness errors of the sun, ring and planet on the bearing forces and critical tooth stress. Some guidelines for tolerance control to manage critical stress and bearing forces are deduced from the results. Carrier indexing error planet assembly and planet tooth thickness error are most critical to reduce planet bearing force and maximize load sharing as well as to reduce critical stresses. Sun and carrier bearing forces due to errors increase several times more than those of normal condition.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2017.11a
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• pp.190-191
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• 2017

본 연구는 산림 공간에서 산불소화시설인 수관수막타워의 방수시간에 따른 화재에 미치는 영향을 FDS(Fire Dynamics Simulator, 화재시뮬레이션)로 비교하였다. 본 연구를 진행하기 위한 기본 조건은 수관수막타워 높이 20m, 방수길이 40m, 방수량 400Lpm으로 해석공간 상에 수막타워를 3기 설치하였다. 수관수막타워 작동 초반 화재온도 $668.5^{\circ}C$에서 작동 450초 후 $145.6^{\circ}C$으로 감소되는 효과를 볼 수 있다. 이는 '산불소화시설 설치 및 운영 관리 지침'의 제3조 11절 6항의 '수관수막설비는 산불 접근 예상시간보다 10분전에 가동되도록 해야 한다.'의 타당성을 마련할 수 있다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1145-1146
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• 2011

• Korean Journal of Remote Sensing
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• v.36 no.2_1
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• pp.179-197
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• 2020

Topographic normalization reduces the terrain effects on reflectance by adjusting the brightness values of the image pixels to be equal if the pixels cover the same land-cover. Topographic effects are induced by the imaging conditions and tend to be large in high mountainousregions. Therefore, image analysis on mountainous terrain such as estimation of wildfire damage assessment requires appropriate topographic normalization techniques to yield accurate image processing results. However, most of the previous studies focused on the evaluation of topographic normalization on satellite images with moderate-low spatial resolution. Thus, the alleviation of topographic effects on multi-temporal high-resolution images was not dealt enough. In this study, the evaluation of terrain normalization was performed for each band to select the optimal technical combinations for rapid and accurate wildfire damage assessment using PlanetScope images. PlanetScope has considerable potential in the disaster management field as it satisfies the rapid image acquisition by providing the 3 m resolution daily image with global coverage. For comparison of topographic normalization techniques, seven widely used methods were employed on both pre-fire and post-fire images. The analysis on bi-temporal images suggests the optimal combination of techniques which can be applied on images with different land-cover composition. Then, the vegetation index was calculated from the images after the topographic normalization with the proposed method. The wildfire damage detection results were obtained by thresholding the index and showed improvementsin detection accuracy for both object-based and pixel-based image analysis. In addition, the burn severity map was constructed to verify the effects oftopographic correction on a continuous distribution of brightness values.