• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.10
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• pp.765-772
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• 2020

A lot of studies to overcome the limitation of flight time have been studied, since the requirement of complicated mission achievement of aircraft including Unmanned Aerial Vehicles(UAVs) has been increased. The fuel limitation could bring about not enough flight time to accomplish missions. For this reason, the rendezvous maneuver is required to accomplish aerial refueling missions. The rendezvous guidance law based on variable pursuit guidance is designed using Lyapunov stability theory in this study. Numerical simulation is performed to demonstrate the performance of the proposed rendezvous guidance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.153-158
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• 2017

Rendezvous point is used to gather the data from sensor nodes and send to sink node efficiently in selected area. It incurs a unbalanced energy consumption nearby the rendezvous point which can shorten the network life time shortly. Thus, it is very important to select the rendezvous point effectively among all sensors in order to not drain the battery of a sensor node in construction sites. In this paper, we propose a rendezvous point replacement mechanism which considers remaining energy of nodes to prolong the network lifetime. Also, for shortening the distance of drone at the same time, it increases the probability of the near-by drone node becoming rendezvous point. The simulation results show that the proposed scheme can significantly improve the network lifetime and the flight distance compared with the existing LEACH, L-LEACH algorithm.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.392-393
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• 2008

서버와 클라이언트 기능을 모두 수행하면서 피어들끼리 직접 데이터를 주고받는 P2P 환경에서는 정보의 다양성으로 인하여 원하는 정보를 한 흡 이내에서 찾을 확률이 매우 낮다. 따라서 정보 검색을 위한 플러딩을 수행하게 되는데 플러딩 방법은 모든 피어가 네트워크에 참여하기 때문에 많은 부하가 생기고 네트워크 성능을 저하시킨다. 이러한 문제점은 차량 네트워크에서도 그대로 나타나게 된다. 이를 해결하기 위해 본 논문에서는 JXTA의 랑데부 피어 컨셉을 이용하여 정보 검색을 수행하도록 하였다. 랑데부 피어를 사용한 세 가지의 시나리오와 플러딩 방식을 사용하는 한 가지 시나리오를 시뮬레이션 한 결과 랑데부 피어를 사용하는 방식이 네트워크에 부하를 덜 주면서 효율적인 정보검색을 한다는 것을 확인하였다. 또한 차량 네트워크에서 이동성을 지원하기 위하여 기존의 클러스터링에 VMBC알고리즘을 이용한 그룹 리더(랑데부 피어)선정 방법을 제안하였다. 제안한 그룹 리더 선정 방법을 토대로 시뮬레이션 한 결과 이동성이 존재 할 경우에도 플러딩 방식보다 효율적으로 정보 검색이 이루어지는 것을 확인할 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.4
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• pp.453-461
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• 2019

In this paper, we focus on the study of multi-node rendezvous on one common channel among multiple channels before transmitting in CRAHNs (Cognitive Radio Ad-hoc Networks) for the efficient use of inefficient frequency resources. Most existing researches have dealt with the channel rendezvous between two nodes. But, it can be time-consuming to apply them to three or more nodes. In addition, it cab be impossible to communicate with each other. Therefore, in this paper, we propose a Multi-Node Sequence (MNSEQ), which allows three or more nodes to rendezvous on a single common channel in a short period of time. And, CSMA/CA was applied for data exchange after rendezvous. By performance evaluation through very extensive simulations, we have demonstrated that the proposed MNSEQ outperforms the existing scheme in terms of communication completion time and transmission efficiency.

• Journal of Space Technology and Applications
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• v.2 no.1
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• pp.30-40
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• 2022

This paper illustrates the trajectory design of drift distance recovery after initial launch and proximity operation when verifying rendezvous/docking technology using nanosatellites. The rendezvous/docking is a technology that is the basis of on-orbit servicing technology and is a preemptive process essential for approaching a target object. In particular, since it is difficult to verify in space, nanosatellites have recently been used to reduce the risk and cost of the development stage. Therefore, this paper not only introduces the configuration and specifications of thrusters for nanosatellites but also designs relative trajectories that can take into account the thrust limitations which come from the small size and low power of nanosatellites. In addition, we intend to be helpful in later designing scenarios according to the improvement of available thruster performance through comparison of trajectories and thrust usage with cases without thrust limitations.

• The Science & Technology
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• no.7 s.422
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• pp.98-99
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• 2004

• Korean Architects
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• s.651
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• pp.121-125
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• 2023

• KIISE Transactions on Computing Practices
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• v.24 no.2
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• pp.77-81
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• 2018

Many studies that improve the efficiency of data collection and a network's lifetime by using a mobile sink have been conducted using wireless sensor networks. If a drone is used as a mobile sink, the drone can collect data more efficiently than can existing mobile sinks operating on the ground because the drone can minimize the effects of obstacles and the terrain. In this paper, we propose a rendezvous node selection scheme which considers estimated drone's trajectory and data collection latency of sensor networks for reliable data collection, when a drone whose trajectory is not predetermined works with terrestrial wireless sensor networks. A selected rendezvous node on the ground collects data from the entire network and it sends then collected data to the drone via direct communication. We also verify that the proposed scheme is more reliable than previous schemes without considering the drone's trajectory and data collection latency.

• Journal of Space Technology and Applications
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• v.1 no.1
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• pp.7-22
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• 2021

In this paper, we describe the results of the docking phase test in the ground environment of the rendezvous/docking technology verification satellite under development for the first time in Korea. rendezvous/docking technology is a high-level technology in space technology, which is also very important for accessing and performing tasks on relative objects in space orbit. In this paper, we describe the ground test results that the chaser finally docks the fixed target using an air bearing device. Based on the thrust control algorithm in the docking phase and the relative object recognition and relative distance estimation algorithm using visual-based sensors validated in this paper, we intend to use them for later expansion to rendezvous/docking algorithms in three-dimensional space for testing in space.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.11
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• pp.1072-1078
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• 2008

An adaptive control algorithm for spacecraft rendezvous and docking in a Keplerian orbit is presented. The equations of relative motion of two spacecrafts expressed in a local-vertical-local-horizontal rectangular frame are converted to a general Hamiltonian form, then an adaptive control method developed for the uncertain Hamiltonian system is applied to the rendezvous and docking problem. A smooth projection algorithm is applied to keep the parameter estimates inside a singularity-free region, and a numerical example shows that the developed controller successfully deals with the unknown mass of the chaser spacecraft.