• 인터넷정보학회논문지
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• 제9권2호
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• pp.1-13
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• 2008

최근 이동사무환경에 대한 관심이 증대되고 있다. 이를 위한 '유비쿼터스 이동사무환경 시스템'의 메신저 시스템은 기존 메신저 프로토콜에서 지원하지 않았던 파일 요청, 사무환경 전송/ 요청 / 브로드캐스팅 등 이동 사무환경 메신저 시스템을 위한 여러 가지 새로운 개념들이 필요하다. 본 논문은 이러한 이동사무환경 메신저에 맞는 새로운 프로토콜을 설계하였으며, 기존의 프로토콜과의 차이점을 분석하였다. 또한 MOE-MP에 최적화된 서버를 구현하고 이에 대한 효율성 분석을 수행하였다. 새롭게 설계한 MOE-MP는 XMPP의 기본적인 프로토콜을 사용하였고, 이동사무환경에 맞도록 확장하였다.

• ETRI Journal
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• 제37권3호
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• pp.480-490
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• 2015

The reliability of sensor networks is generally dependent on the battery power of the sensor nodes that it employs; hence it is crucial for the sensor nodes to efficiently use their battery resources. This research paper presents a method to increase the reliability of sensor nodes by constructing a connected dominating tree (CDT), which is a subnetwork of wireless sensor networks. It detects the minimum number of dominatees, dominators, forwarder sensor nodes, and aggregates, as well as transmitting data to the sink. A new medium access control (MAC) protocol, called Homogenous Quorum-Based Medium Access Control (HQMAC), is also introduced, which is an adaptive, homogenous, asynchronous quorum-based MAC protocol. In this protocol, certain sensor nodes belonging to a network will be allowed to tune their wake-up and sleep intervals, based on their own traffic load. A new quorum system, named BiQuorum, is used by HQMAC to provide a low duty cycle, low network sensibility, and a high number of rendezvous points when compared with other quorum systems such as grid and dygrid. Both the theoretical results and the simulation results proved that the proposed HQMAC (when applied to a CDT) facilitates low transmission latency, high delivery ratio, and low energy consumption, thus extending the lifetime of the network it serves.

• 가정과삶의질연구
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• 제22권5호
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• pp.211-236
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• 2004

This study is designed to conducted group counseling programs applied to the wives of jobless families by Satir's growth model and to help them to recognize the value of themselves and families in their jobless situation and to possess desire and hope for the life of their families in the future. The researcher provided 7 wives of jobless families with group counseling at the family education room of a university from April to June, 2003. The group counseling program consisted of a total of 8 sessions, and each session lasted for three hours to four hours. The researcher came to have a in-depth understanding of the experiences of 5 subjects, who took part in more than 7 sessions in a total of 8 counseling sessions, in the group counseling to which Satir's growth model was applied and analyzed the effects of counseling changing the subjects. The researcher analyzed the following: viewing the subjects themselves and their spouses in a new way, rendezvous with the true self and its acceptance, objective insight into their families, learning how to communicate, and expecting hope through changes. All in all, the wives of jobless families were able to newly recognize the value of the existence of themselves and families and find desire and hope for the life of their families in the future through the group counseling program to which Satir's growth model was applied.

• Journal of Astronomy and Space Sciences
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• 제30권4호
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• pp.279-290
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• 2013

Due to the continuous space development by mankind, the number of space objects including space debris in orbits around the Earth has increased, and accordingly, difficulties of space development and activities are expected in the near future. In this study, among the stages for space debris removal, the implementation of a vision-based approach technique for approaching space debris from a far-range rendezvous state to a proximity state, and the ground test performance results were described. For the vision-based object tracking, the CAM-shift algorithm with high speed and strong performance, and the Kalman filter were combined and utilized. For measuring the distance to a tracking object, a stereo camera was used. For the construction of a low-cost space environment simulation test bed, a sun simulator was used, and in the case of the platform for approaching, a two-dimensional mobile robot was used. The tracking status was examined while changing the position of the sun simulator, and the results indicated that the CAM-shift showed a tracking rate of about 87% and the relative distance could be measured down to 0.9 m. In addition, considerations for future space environment simulation tests were proposed.

• Advances in aircraft and spacecraft science
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• 제7권3호
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• pp.271-290
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• 2020

The paper describes the analysis of deployment strategies and trajectories design suitable for executing the inspection of an operative spacecraft in orbit through re-usable CubeSats. Similar missions have been though indeed, and one mission recently flew from the International Space Station. However, it is important to underline that the inspection of an operative spacecraft in orbit features some peculiar characteristics which have not been demonstrated by any mission flown to date. The most critical aspects of the CubeSat inspection mission stem from safety issues and technology availability in the following areas: trajectory design and motion control of the inspector relative to the target, communications architecture, deployment and retrieval of the inspector, and observation needs. The objectives of the present study are 1) the identification of requirements applicable to the deployment of a nanosatellite from the mother-craft, which is also the subject of the inspection, and 2) the identification of solutions for the trajectories to be flown along the mission phases. The mission for the in-situ observation of Space Rider is proposed as reference case, but the conclusions are applicable to other targets such as the ISS, and they might also be useful for missions targeted at debris inspection.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제22권6호
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• pp.565-570
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• 2019

Benign biliary strictures are uncommon in children. Classically, these cases are managed surgically, however less invasive approaches with interventional radiology and or endoscopy may have similar results and improved safety profiles While benign biliary strictures have been described in literature on several occasions in young children, (most older than 1 year and once in an infant 3 months of age), all reported cases were managed surgically. We present two cases of benign biliary strictures in infants less than 6 months of age that were managed successfully with novel non-invasive procedures and a review of all current pediatric cases reported in the literature. Furthermore, we describe the use of a Rendezvous procedure, which has not been reported as a treatment approach for benign biliary strictures.

• Journal of Astronomy and Space Sciences
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• 제35권4호
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• pp.263-277
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• 2018

This paper presents a vision-based relative pose estimation algorithm and its validation through both numerical and hardware experiments. The algorithm and the hardware system were simultaneously designed considering actual experimental conditions. Two estimation techniques were utilized to estimate relative pose; one was a nonlinear least square method for initial estimation, and the other was an extended Kalman Filter for subsequent on-line estimation. A measurement model of the vision sensor and equations of motion including nonlinear perturbations were utilized in the estimation process. Numerical simulations were performed and analyzed for both the autonomous docking and formation flying scenarios. A configuration of LED-based beacons was designed to avoid measurement singularity, and its structural information was implemented in the estimation algorithm. The proposed algorithm was verified again in the experimental environment by using the Autonomous Spacecraft Test Environment for Rendezvous In proXimity (ASTERIX) facility. Additionally, a laser distance meter was added to the estimation algorithm to improve the relative position estimation accuracy. Throughout this study, the performance required for autonomous docking could be presented by confirming the change in estimation accuracy with respect to the level of measurement error. In addition, hardware experiments confirmed the effectiveness of the suggested algorithm and its applicability to actual tasks in the real world.

• 천문학논총
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• 제38권2호
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• pp.25-36
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• 2023

Since interstellar objects like 1I/'Oumuamua and 2I/Borisov originate from exoplanetary systems, even if we do not visit the exoplanetary systems, flyby, rendezvous, and sample return missions of interstellar objects can provide clues to solve the mysteries of cosmic life phenomena such as the origin of exoplanetary systems, galactic evolution, biosignatures (or even technosignatures), and panspermia. In this paper, we review space missions for interstellar object exploration in the stage of mission design or concept study such as Project Lyra, Bridge, Comet Interceptors, and Lightcraft^TM. We also review space missions, OSIRIS-REx and NEA Scout, designed for Near Earth Asteroids(NEA) explorations, to investigate the current state of basic technologies that can be extended to explore interstellar objects in a velocity of ~ 6AU/year. One of the technologies that needs to be developed for interstellar object exploration is a spacecraft propulsion method such as solar sail, which can catch up with the fast speed of interstellar objects. If this kind of propulsion becomes practical for space explorations, interstellar object explorations will mark a new era and serve as a driving force to provide evidences of cosmic life.

• 천문학회보
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• 제46권1호
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• pp.44.1-44.1
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• 2021

한기로 나누어 보면, 흑점의 관측 빈도는 두 기간에서 비슷하지만, 오로라는 냉한기에 집중적으로 관측된다. 특이하게도, 크기가 큰 흑점의 경우는 냉한기보다 온난기에서 관측 빈도가 세 배 이상 높다. 또한, 흑점과 관련된 오로라의 강도를 분석해보면 크기가 큰 흑점은 작은 흑점보다 2~3배 이상 지구영향성이 높다는 것을 알 수 있다.

• 천문학회보
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• 제46권2호
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• pp.57.3-57.3
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• 2021

99942 Apophis is an Sq-type Potentially Hazardous Asteroid (PHA) with an estimated diameter of 370 m. It will approach the Earth down to 31,000 km from the surface during the encounter on April 13, 2029 UT, which is closer than geostationary satellites. This once-in-a-20,000 year opportunity would further expand our knowledge on the physical and dynamical processes which are expected to occur due to the gravitational tidal forces when an asteroid encounter with a planet. It will also provide an opportunity to promote great knowledge of the science of planetary defense. The science goal of the Apophis mission is to global-map the asteroid before and after the Earth's approach. In this talk, we will present scientific objectives, and briefly introduce instruments and operation scenarios of the mission.