• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.55-57
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• 2007

A Power control and Distribution Unit (PCDU) plays roles of protection of battery against overcharge by active control of solar array generated power, distribution of unregulated electrical power via controlled outlets to bus and instrument units, distribution of regulated electrical power to selected bus and instrument units, and provision of status monitoring and telecommand interface allowing the system and ground operate the power system, evaluate its performance and initiate appropriate countermeasures in case of abnormal conditions. In this work, we perform the preliminary design of a PCDU for the small Low Earth Orbit (LEO) Satellite applications. The main constitutes of the PCDU are the battery interface module, solar array regulators with maximum power point tracking (MPPT) technology, heater power distribution modules, internal converter modules for regulated bus voltage generation, power distribution modules of unregulated and regulated primary bus, and instrument power distribution modules.

• 전기학회논문지
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• 제59권11호
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• pp.2073-2082
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• 2010

The 4-th generation of mobile communication aims to realize global, fast and mobile communication service. The satellite communication charges a key role in this field. In this study, an OTM(On-The-Move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite was addressed. Since vehicles move during communication, active antenna line-of-sight stabilization is a core technology to guarantee high satellite communication quality. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. Various disturbance torques such as static and dynamic mass imbalance torques, variation of moment of inertia according to elevation angle, friction torque related to vehicle motion, equivalent disturbance torque due to antenna roll motion, etc. were analyzed. As a robust stabilization control, rate feedback with sliding mode control and position feedback with proportional+integral control was suggested. To compensate antenna roll motion, a supplementary roll rate feed forward control was included beside of the feedback control loop. The feasibility of the analysis and the proposed control design were verified along with some simulation results.

• 대한의용생체공학회:의공학회지
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• 제32권2호
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• pp.93-104
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• 2011

The purpose of this study was to investigate lower-limb joint torque of the two groups as it changed by somatosensory stimulation during the descent down three stairs of different heights and to describe the difference between the two groups, which are young people group and elderly people group. Subjects of each groups climbed down a stair at four stimulation conditions, which are non-stimulation, tibialis anterior tendon stimulation, achilles tendon stimulation, tibialis anterior - achilles tendon stimulation. Motion capture data were collected using 3D optoelectric motion tracking system that utilizes active infrared LEDs, near infrared sensor and force plate. The obtained motion capture data was used to build 3D computer simulation model. The results show that lower-limb joint torque of the two groups changed with somatosensory stimulation as they descended the stairs and the joint torque of the two groups differed from each other.

• 정보저장시스템학회논문집
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• 제3권4호
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• pp.191-195
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• 2007

The optical disc drive has used a high NA objective lens and a shorter wavelength laser diode for high recording density. But high NA and shorter wavelength cause several margins to become short. Focusing and tracking servo has to be more accurate and active tilt compensation mechanism is also needed for coma aberration compensation. In this paper, we proposed 3-axis moving magnet type actuator. For 3-DOF motion, moving coil actuator has to be equipped with 6 wires for supplying 3 independent signals. However, moving magnet type actuator doesn't need to change the configuration of wires because coils are in stator. So, we added a tilt mechanism to the 2-axis moving magnet actuator which is designed in previous research. Addition of the tilt mechanism cuts down the focus sensitivity. So, maximization the tilting sensitivity and securing the focusing sensitivity are objectivities of this research. DOE (design of experiments) procedures of electromagnetic circuit are performed for parameter study and the optimization is also performed to maximize the tilt sensitivity. And then the final design is suggested and its performance is verified by FE simulation.

• 한국실내디자인학회논문집
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• 제17권4호
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• pp.84-91
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• 2008

The objective of this study is to investigate how visitors' behavior change in relation to the pattern of exhibition in art museum. For the purpose Busan Museum of Modern Art was selected as the sample in this study. And two patterns of exhibition, namely the planar exhibition and the three dimensional exhibition, were surveyed using the tracking movement method. The data gathered from random-sampling 60 visitors in a art museum was analyzed by the correlation analysis and T-test. The results are as follows; 1) There is no meaningful difference in visitors' behavior by the exhibition pattern in terms of their viewing area, viewing time, viewing distance, viewing velocity, viewing rate. 2) In contrast, there is meaningful difference in terms of the number of stops by visitors and the time spent without movement to see the objects; visitors stopped more often and stayed longer within the three dimensional exhibition space than the planar exhibition in a art museum. In sum, visitors extrinsically show no big behavioral difference between the planar exhibition and the three dimensional exhibition, but much difference in the way they communicate with objects; they show more active behavior within the three dimensional exhibition space.

• Journal of Power Electronics
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• 제15권4호
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• pp.1093-1104
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• 2015

A standard repetitive controller (RC) is theoretically able to replace a bank of resonant controllers in harmonic signals tracking applications. However, the traditional RC has some drawbacks such as a poor dynamic response and a complex structure to compensate grid frequency deviations for an effective unified power quality conditioner (UPQC) control scheme. In order to solve these problems, an improved RC with an outstanding dynamic response and a simplified grid frequency adaptive scheme is proposed for UPQC control systems in this paper. The control strategy developed for the UPQC has delay time, i.e., one-sixth of a fundamental period (T_p/6), repetitive controllers. As a result, the UPQC system can provide a fast dynamic response along with good compensation performance under both nonlinear and unbalanced loads. Furthermore, to guarantee the excellent performance of the UPQC under grid frequency deviations, a grid frequency adaptive scheme was developed for the RC using a simple first order Padé's approximation. When compared with other approaches, the proposed control method is simpler in structure and requires little computing time. Moreover, the entire control strategy can be easily implemented with a low-cost DSP. The effectiveness of the proposed control method is verified through various experimental tests.

• 대한교통학회지
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• 제19권6호
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• pp.161-170
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• 2001

차량검출은 교통량 관측(모니터링)을 위해서 필요한 가장 기본적인 요소이다. 영상을 기반으로 한 교통정보추출 시스템은 다른 방식을 이용하는 시스템들과 비교했을 때 몇 가지 두드러진 장점을 가지고 있다. 그러나 영상기반 시스템에서는 영상에 포함된 그림자가 차량검출의 정확도를 저해하는 요소로 작용하는 데, 특히 이동 중인 차량에 의해서 발생하는 환성 그림자는 심각한 성능저하를 야기할 수 있다. 본 논문에서는 차량검출과 그림자 영향 제거를 위해서 배경 빼기와 에지 검출을 결합한 새로운 접근방법을 제안하였다. 제안한 방법은 노변의 지형지물에 의해서 발생하는 비활성 그림자가 크게 증가하는 상황에서도, 98(%)이상의 차량검출 정확도를 나타내었다. 본 논문에서 제안한 차량검출 방법을 기반으로 하여, 차량 추적, 차량 계수, 차종 분류, 그리고 속도 측정을 수행하여 각 차로의 부하를 나타내는 데 사용되는 차량 흐름과 관련된 여러 가지 교통정보를 추출하였다.

• 인터넷정보학회논문지
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• 제5권6호
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• pp.1-10
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• 2004

A web robot is a software that has abilities of tracking and collecting web documents on the Internet(l), The performance scalability of recent web robots reached the limit CIS the number of web documents on the internet has increased sharply as the rapid growth of the Internet continues, Accordingly, it is strongly demanded to study on the performance scalability in searching and collecting documents on the web. 'Design of web robot based on Multi-Agent to speed up documents collection ' rather than 'Sequentially executing Web Robot based on the existing Fork-Join method' and the results of analysis on its performance scalability is presented in the thesis, For collection speedup, a Multi-Agent based web robot performs the independent process for inactive URL ('Dead-links' URL), which is caused by overloaded web documents, temporary network or web-server disturbance, after dividing them into each agent. The agents consist of four component; Loader, Extractor, Active URL Scanner and inactive URL Scanner. The thesis models a Multi-Agent based web robot based on 'Amdahl's Law' to speed up documents collection, introduces a numerical formula for collection speedup, and verifies its performance improvement by comparing data from the formula with data from experiments based on the formula. Moreover, 'Dynamic URL Partition algorithm' is introduced and realized to minimize the workload of the web server by maximizing a interval of the web server which can be a collection target.

• 천문학회보
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• 제44권1호
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• pp.73.4-73.4
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• 2019

The TXS0506+056 is a blazar and counterpart of the neutrino event IceCube-170922A. It is the first time that the neutrino event and flaring event in electromagnetic wave (EM) coincided. We observed TXS0506+056 with medium-bands in optical using 0.25m and 2.1m telescope at McDonald observatory about a month after the neutrino event. We tracked the variability of SED of the target for three weeks, and our observation showed no abrupt variability in optical range during this period. We concluded that a month after the neutrino event, the TXS0506+056 became less active and shows no feature of the energetic event. We also concluded that the medium-bands are well suited for tracking SEDs of objects. Our result demonstrates the potential of the wide-field 0.25m telescope (5.5 deg^2) for finding transient objects and track the variability of sources like AGNs.

• International Journal of Internet, Broadcasting and Communication
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• 제15권4호
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• pp.215-222
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• 2023

Augmented reality (AR), which integrates virtual media into reality, is increasingly utilized across various industrial sectors, thanks to advancements in 3D graphics and mobile device technologies. The IT industry is thus carrying out active R&D activities about AR platforms. Google plays a significant role in the AR landscape, with a focus on ARCore services. An essential aspect of ARCore is the use of anchors, which serve as reference points that help maintain the position and orientation of virtual objects within the physical environment. However, if the accuracy of anchor positioning is suboptimal when running AR content, it can significantly diminish the user's immersive experience. We are to assess the performance of these anchors in this study. To conduct the performance evaluation, virtual 3D objects, matching the shape and size of real-world objects, we strategically positioned ourselves to overlap with their physical counterparts. Images of both real and virtual objects were captured from five distinct camera trajectories, and ARCore's performance was analyzed by examining the difference between these captured images.