• 한국응급구조학회지
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• 제7권1호
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• pp.135-146
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• 2003

The purpose of this study was to improve EMS-System in Korea through the research in EMS-System of advanced country. The response time is defined as the interval from the time of call receipt to the time of scene arrival. The important factor was to shorten moving distance of ambulance. It should be considered to accomplish this factor that the vehicle must be increased and the convenient location chosen for optimizing of service area. The transport of emergency patients carried out almost by 119 Emergency Medical Service but out of all the employees at 119 EMS only 11.3% have own qualified EMT degree. They should be employed more and more specially at 119 EMS for a superior level of emergency medical care for civilian. In America, EMT can take care of emergency patients following the order from medical Director at the scene of accident. But in Germany, prehospital care was emphasized from the beginning and, in those days, a medical doctor was sent for treatment of emergency patients at the scene, the so-called a Rendezvous system. Hierby this study makes the suggestion to improve the EMS-System, it is effective to use the medical Director system in America and furthermore a Rendezvous system in Germany. The functional integratin and unification of the report system as well as enough personal and equipmental elements saved together invaluable lives.

• International Journal of Aeronautical and Space Sciences
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• 제12권1호
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• pp.43-56
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• 2011

An integrated system composed of guidance, navigation and control (GNC) system for autonomous proximity operations and the docking of two spacecraft was developed. The position maneuvers were determined through the integration of the state-dependent Riccati equation formulated from nonlinear relative motion dynamics and relative navigation using rendezvous laser vision (Lidar) and a vision sensor system. In the vision sensor system, a switch between sensors was made along the approach phase in order to provide continuously effective navigation. As an extension of the rendezvous laser vision system, an automated terminal guidance scheme based on the Clohessy-Wiltshire state transition matrix was used to formulate a "V-bar hopping approach" reference trajectory. A proximity operations strategy was then adapted from the approach strategy used with the automated transfer vehicle. The attitude maneuvers, determined from a linear quadratic Gaussian-type control including quaternion based attitude estimation using star trackers or a vision sensor system, provided precise attitude control and robustness under uncertainties in the moments of inertia and external disturbances. These functions were then integrated into an autonomous GNC system that can perform proximity operations and meet all conditions for successful docking. A six-degree of freedom simulation was used to demonstrate the effectiveness of the integrated system.

• 정보처리학회논문지C
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• 제12C권6호
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• pp.793-798
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• 2005

본 논문에서는 방송, 통신, 인터넷이 통합되는 BcN 환경에서 멀티캐스트(Multicast) 서비스를 지원하기 위한 네트워크의 분기점(Rendezvous Point)에서 시스템 모델을 살펴본다 서비스에 따른 다중의 큐와 단일 서버로 이루어진 버퍼를 기하 분포의 배치 확률을 가지는 입력이 들어올 때, 단일 큐와 단일 서버로 모델링하여 입력률 $\lambda$에 따른 버퍼의 크기를 보이고, 서비스 제공자와 네트워크 운영자 사이의 관계를 알아본다. 이때 두 관점의 이익이 같아지는 최적의 입력률 ${\lambda}_{opt}$를 기준으로 새로운 서비스 요청에 대하여 이익을 기반으로 하는 호 수락 제어를 할 수 있는 범위를 제시한다.

• International Journal of Contents
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• 제5권1호
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• pp.21-26
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• 2009

Peer to Peer (P2P) utilizes the resources of an offered service without the need for a central server or preexistent server-client, making it a desirable network environment for data exchange based on direct connection between peers. Proposed by Sun Microsystems. JXTA(Juxtapose) is a typical P2P system and distributed computing model that does not require central service resources and is flexible to deal with various network configuration changes. Meanwhile. Mobile Ad-hoc NETwork(MANET) is a typical wireless network configured with mobile nodes and without an infrastructure. where a network is established by direct connection or through other peers in the propagation area. Thus, MANET maintains the latest path information by establishing paths and changing path information for communication between peers in a highly mobile wireless network. Accordingly. this article proposes the JXTAMANET method for wireless networks to enable JXTA to be applied to MANET. NS2 is used to evaluate the performance and the proposed architecture is shown to produce better results than a conventional flooding method.

• 한국통신학회논문지
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• 제32권10B호
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• pp.621-629
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• 2007

CR 네트워크에서의 무선 채널은 일반적으로 우선 사용자에 의해 점유되어 사용하지 못하는 채널과 점유되지 않은 사용 가능한 채널로 분류된다. 하지만 이러한 채널 분류는 CR 노드와 우선 사용자의 시간적 특성만 고려하고, 공간적 특성을 고려하지 않아 유휴 주파수 자원 확보에 비효율적이다. 이에 본 논문에서는 중앙 집중형 CR 네트워크 환경에서 기존방식의 단점을 극복하여 유휴 주파수 자원을 보다 효율적으로 확보할 수 있는 새로운 채널 분류 방법을 제안하며, 제안하는 채널 분류 방법의 효율성을 수학적으로 분석한다. 이와 더불어 정의한 채널분류를 이용하여 주파수 자원이 매우 동적으로 변화하는 환경에서도 상하향 제어 채널 확보를 용이하게 확보할 수 있는 랑데부 알고리즘을 제안한다.

• 한국정보통신학회논문지
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• 제11권8호
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• pp.1486-1492
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• 2007

P2P와 같은 분산 컴퓨팅 환경에서는 분산된 자원의 효율적인 검색이 매우 중요하다. 그러나 분산된 자원의 검색은 수많은 피어를 순회하며 정보를 검색해야 하므로 검색 횟수의 증가에 따른 시스템 부하와 많은 검색 시간을 소요하게 된다. 본 논문에서는 JXTA 네트워크 환경에서 분산된 자원의 효율적인 검색을 위해 DHT(Distributed Hash Table)를 기반으로 한 프락시 피어 알고리즘을 설계하였다. 랑데부 피어들의 정보를 프락시 피어에 유지하고 검색 성공 확률이 높은 랑데부 피어들을 우선 검색함으로써 검색 횟수를 줄여 발생될 수 있는 오버 헤드를 최소화 할 수 있었다.

• Journal of Astronomy and Space Sciences
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• 제38권2호
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• pp.105-117
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• 2021

In this study, a preliminary trajectory design is conducted for a conceptual spacecraft mission to a near-Earth asteroid (NEA) (99942) Apophis, which is expected to pass by Earth merely 32,000 km from the Earth's surface in 2029. This close approach event will provide us with a unique opportunity to study changes induced in asteroids during close approaches to massive bodies, as well as the general properties of NEAs. The conceptual mission is set to arrive at and rendezvous with Apophis in 2028 for an advanced study of the asteroid, and some near-optimal (in terms of fuel consumption) trajectories under this mission architecture are to be investigated using a global optimization algorithm called monotonic basin hopping. It is shown that trajectories with a single swing-by from Venus or Earth, or even simpler ones without gravity assist, are the most feasible. In addition, launch opportunities in 2029 yield another possible strategy of leaving Earth around the 2029 close approach event and simply following the asteroid thereafter, which may be an alternative fuel-efficient option that can be adopted if advanced studies of Apophis are not required.

• Journal of Positioning, Navigation, and Timing
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• 제9권4호
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• pp.357-366
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• 2020

This paper addressed a relative navigation method for autonomous rendezvous and docking of cube-satellites using single frequency Differential GPS (DGPS) under the intermittent communication between satellites. Since the ionospheric error of GPS measurement is variable depending on the visible satellites, a few meters error of relative navigation is occurred in the Low-Earth Orbit (LEO) environment. Therefore, it is essential to remove the ionospheric error to perform relative navigation. Besides, an intermittent communication period for receiving GPS measurements of the target satellite is limited for getting information every sampling time. To solve this problem, a method combining range domain DGPS and orbit propagation is proposed in this paper. The proposed method improves the performance of DGPS by using Hatch filter and solves an intermittent communication problem by estimating the relative position and velocity using Hill-Clohessy-Wiltshire Equation. Through the simulation, it is verified that the suggested algorithm provides the relative position error within RMS 0.5 m and the relative velocity error within RMS 3 cm/s. Furthermore, it has the advantage that it is suitable for real-time implementation using single-frequency GPS measurements and is computationally efficient.

• 천문학회보
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• 제46권1호
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• pp.43.4-44
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• 2021

99942 Apophis is an Sq-type Aten group Near-Earth Asteroid (NEA) with an estimated size of 370 m. It will approach the Earth to come within the geostationary orbit during the upcoming encounter on April 13, 2029 to offer a unique chance to study its 1) global properties, 2) surface arrangements, and 3) their detectable changes expected to happen, in sub-meter scale. What measurable scientific goals for the asteroid in this "once a millennium" event could transform our knowledge of planetary science and defense? The Apophis rendezvous mission aims to understand the characteristics of the small solar system body's nature. It also prepares for potential threats from natural objects by measuring in-situ surface, shape, rotation, and orbit changes expected to occur when the target asteroid passes close to the Earth in 2029. We will present an overview of the mission scheduled to be launched from late 2026 to early 2027 and introduce scientific objectives.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1867-1870
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• 1997

Waypoint guidance is a technique used to steer an autonomous vehicle along a desired trajectory. In this paper, a waypoint guidance algorithm for horizontal plane is derived by combining a line following guidance law and a turning guidance law. The line following guidance is derived based on LQR while the turning guidance is designed using rendzvous problem. Through simulation, the proposed method shows a good performance.