• ETRI Journal
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• 제43권4호
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• pp.758-768
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• 2021

In this work, the secrecy of a typical wireless cooperative dual-hop non-orthogonal multiple access (NOMA)-enabled decode-and-forward (DF) relay network is investigated with the impact of collaborative and non-collaborative eavesdropping. The system model consists of a source that broadcasts the multiplexed signal to two NOMA users via a DF relay, and information security against the eavesdropper nodes is provided by a helpful jammer. The performance metric is secrecy rate and ergodic secrecy capacity is approximated analytically. In addition, a differential evolution algorithm-based power allocation scheme is proposed to find the optimal power allocation factors for relay, jammer, and NOMA users by employing different jamming schemes. Furthermore, the secrecy rate analysis is validated at the NOMA users by adopting different jamming schemes such as without jamming (WJ) or conventional relaying, jamming (J), and with control jamming (CJ). Simulation results demonstrate the superiority of CJ over the J and WJ schemes. Finally, the proposed power allocation outperforms the fixed power allocation under all conditions considered in this work.

• 농촌지도와개발
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• 제2권2호
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• pp.205-227
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• 1995

The objectives of this study were to 1) classify the cooperative farmers' organizations in Korea according to the development level and institutional aspects through the exploration of its' conceptual and institutional basis, 2) analyze the farmers' needs for organization, 3) identify the problems and situation of organizations, and 4) formulate an effective management model for each cooperative farmers' organization. The study was carried out through a review of literature and using available statistical data collected from various sources and empirical survey. Major findings of the study were: 1) the cooperative farmers' organizations could be classified into four types : crop units, farming cooperative corporation, trust farming companies and joint-stock agri-business. 2) a lot of members of the organization feel that the information is insufficient, the opportunity to suggest their own ideas is hardly given, and the members are not satisfied with the cooperation among the members, 3) the members who have higher level of schooling education showed a higher participation level in the organization, 4) most of members did not recognize the organization they participated in, 5) participation of the organization's members and concerned institutions is an important factor to promote problem solving and better communication within the organization, 6) any type of continuing education for the members is needed to facilitate the transfer of a new agricultural and organizational technology, 7) research and development(R & D) is one of the most important factors of the development of organizations, 8) most organizations are deficient in professional management skills(financial, personal, accounts, etc.), 9) the trust farming companies have difficulties in managing the firm on account of the characteristics of agriculture(especially seasonal), the dispersed trust lands, and the need for more alternative work in the winter season, and 10) in the case of agri-businesses, their organizations are more specialized in marketing and have more structured systems of management. Based on the results of the study the following recommendations were made for further improvement and development of agricultural cooperative organizations : (1) More governmental support should be given to education for improvement of the organizational structure. And more deliberate and differentiated governmental support should be provided for the organizations to be viably managed. (2) For more efficient communication between the members and the organization, more opportunities for discussion are needed. (3) The more research should be committed to this kind of work in order to get more analytic data and strategic plans of cooperative organizations.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1553-1558
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• 2003

The authors investigate influences of manipulator dynamics on and roles of kinesthetic sensation and visual sensation in a Human-Machine Cooperative System (HMCS). At first, the general structure and essential transfer functions of HMCSs are described based on the previous work. Then, after showing theoretical treatment of manipulator dynamics, this paper analyzes the influences on HMCSs in two cases: one is the control design focusing on tool dynamics and reaction force transfer function, and the other is that specifies maneuver transfer function and transfer function for object dynamics variation. In addition to conventional experiments only employing kinesthetic sensation, other experiments with both kinesthetic and visual sensations are performed to examine difference in the roles of these sensations and the validity of the design without the visual sensation.

• 제어로봇시스템학회논문지
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• 제5권8호
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• pp.948-954
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• 1999

In this paper, we propose a cooperative motion planning algorithm for two tightly-coupled mobile robots. Specifically, the considered cooperative work is that two mobile robots should transfer a long rigid object along a predefined path. To resolve the problem, we introduce a master-slave concept for two obile robots having the same structure. According to the velocity of the master robot and the positions of two robots on the path, the velocity of the slave robot is determined. The slave normally tracks the master's motion, but in case that the velocity of the slave exceeds the velocity limit, the roles of the robots should be interchanged. The effectiveness of the proposed algorithm is proved by computer simulations.

• 대한가정학회지
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• 제39권10호
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• pp.1-17
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• 2001

This study is to develop cooperative learning aids for Clothing and Textiles classes, and to develop methods and tools for performance assessment. We have surveyed 127 students with‘class evaluation’questionnaire after teaching 9 classes through developed materials. As a result, we found that students preferred to cooperative learning and they tended to do their best in their assigned role in the cooperative learning. Meanwhile, we also found that they understood the assignment of performance assessment well and they felt lack of time to handle given tasks. It shows that we need to be flexible when applying a teaching method in a way that teachers give student more options to choose their duty and time span. Although a few students create a problem and delay their duty as disturbing cooperation in a group we anticipate that the developed teaching aids and performance assessment will be a great help to improve Home Economics classes. In closing, we believe that we can be open-minded Home Economics educators that continue to work on improving classes through developing diverse teaching aids and performance assessment.

• Journal of Communications and Networks
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• 제18권3호
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• pp.397-410
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• 2016

This paper proposes a novel cooperative localization method for distributed wireless networks in 3-dimensional (3D) global positioning system (GPS) denied environments. The proposed method, which is referred to as hybrid ellipsoidal variational algorithm (HEVA), combines the use of non-parametric belief propagation (NBP) and variational Bayes (VB) to benefit from both the use of the rich information in NBP and compact communication size of a parametric form. InHEVA, two novel filters are also employed. The first one mitigates non-line-of-sight (NLoS) time-of-arrival (ToA) messages, permitting it to work well in high noise environments with NLoS bias while the second one decreases the number of calculations. Simulation results illustrate that HEVA significantly outperforms traditional NBP methods in localization while requires only 50% of their complexity. The superiority of VB over other clustering techniques is also shown.

• 한국항공운항학회지
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• 제27권3호
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• pp.1-14
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• 2019

Cooperative systems among various unmanned vehicles are widely used in various field and emerging. Unmanned vehicles are able to operate various missions without operator onboard and they are highly stable. Collaborative work of multiple unmanned vehicles is emphasized due to the difficulty of recent missions such as SEAD (Suppression of the Enemy Air Defenses), MUSIC (Manned Unmanned Systems Integration Capability), goldentime in the rescue mission. In this study, ROS and Pixhawk were proposed as a method of construction of a collaboration system and framework for an integrated simulation environment for heterogeneous unmanned vehicles is proposed. Totally 5 unmanned vehicles were set for the simulation for the observation of illegal fishing boats. This paper shows the feasibility of the cooperative system using ROS and Pixhawk through the simulation and the experiment.

• ETRI Journal
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• 제42권6호
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• pp.846-858
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• 2020

The non-orthogonal multiple access (NOMA) technique offers throughput improvement to meet the demands of the future generation of wireless communication networks. The objective of this work is to further improve the throughput by including an underlay cognitive radio network with an existing multi-carrier NOMA network, using cooperative communication. The throughput is maximized by optimal resource allocation, namely, power allocation, subcarrier assignment, relay selection, user pairing, and subcarrier pairing. Optimal power allocation to the primary and secondary users is accomplished in a way that target rate constraints of the primary users are not affected. The throughput maximization is a combinatorial optimization problem, and the computational complexity increases as the number of users and/or subcarriers in the network increases. To this end, to reduce the computational complexity, a dynamic network resource allocation algorithm is proposed for combinatorial optimization. The simulation results show that the proposed network improves the throughput.

• 한국ITS학회 논문지
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• 제17권4호
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• pp.112-123
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• 2018

자율협력주행 도로시스템은 자율주행차와 V2X 통신으로 연결되어 상호정보를 주고받으며 자율주행차의 안전주행을 지원하는 도로인프라 시스템을 말합니다. 본 연구는 자율협력주행 도로시스템 서비스의 성능평가 방안 제시를 목적으로 하며, 도로인프라에서 자율주행차에 정보를 제공하는 I2V 서비스 중 '작업구간 정보제공 서비스'를 예를 들어, 먼저 서비스에 대한 Use Case 분석과 서비스 성능을 확인하기 위해 필요한 요구사항 및 서비스 범위를 정의하고, 이러한 서비스의 성능평가 수행을 위한 평가시스템을 제안하였다. 또한, 본 연구에서 제안한 평가시스템을 활용하여 '작업구간 정보제공 서비스'의 현장시험을 통해 평가 가능여부를 검증하였다.

• 한국작물학회지
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• 제7권1호
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• pp.85-92
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• 1969

우리나라 수도작개량의 방향은 단위당 수량을 향상시키되 어디까지나 지역전체에 고도기술의 적용으로 고단수를 평준화시키면서 능률면에서도 공동작업관리로 이끌어 노동생산성을 높혀야 한다는데 있으므로 이를 구현하는 생산체제인 수도집단재배의 수행을 위한 이론을 연구하고 그 발전을 위한 기대효과와 전망을 구명하여야 하는바 현재까지의 결과를 요약하면 다음과 같다. 1. 수도작지대에서 고단수의 평준화를 위한 생산기술을 보급하고 고능율의 경영을 위해서는 집단재배가 가장 효과적인 방법의 하나이다. 2. 효과적인 집단재배를 실천하기 위하여는 단지의 수리, 토양, 품종 기타 영농상황을 보다 체계화하여야 한다. 3. 이와같은 기간재배기술은 경작농가의 협의에 의하여 재배력을 작성하고 단지내에서의 모든 재배법은 재배력에 의하여 통일되며 기간기술의 작업은 공동으로 하고 기타 세부작업은 개발로 한다. 4. 개별경영에서는 충실하게 도입되기 어려웠던 기술이 집단재배에서는 용이하게 도입될 수 있었으며 1968년도의 전국 집단재배 성적을 보면 일반재배에 비하여 평균 23.3%의 증수를 보이고 있다. 5. 현재 우리나라 집단재배의 형태는 초보적인 협정 영농형을 중심으로 추진되고 있는데 일부작업에는 공동작업형 및 청부작업형도 드물게 결합되고 있는 것이 보이고 있으나 앞으로 보다 안정다수확을 위한 성력화 또는 대규모의 기계화를 위해서는 공동작업형을 촉진시키면서 입지조건에 따라 기술신탁형이나 청부작업형을 결합시켜 나가는 방향으로 발전되어야 할것이다.