• Journal of Communications and Networks
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• v.13 no.5
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• pp.463-471
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• 2011

Cooperative communications using relays in wireless networks have similar effects of multiple-input and multiple-output without the need of multiple antennas at each node. To implement cooperation into a system, efficient protocols are desired. In IEEE 802.11 families such as a/b/g, mobile stations can automatically adjust transmission rates according to channel conditions. However throughput performance degradation is observed by low-rate stations in multi-rate circumstances resulting in so-called performance anomaly. In this paper, we propose active relay-based cooperative medium access control (AR-CMAC) protocol, in which active relays desiring to transmit their own data for cooperation participate in relaying, and it is designed to increase throughput as a solution to performance anomaly. We have analyzed the performance of the simplified AR-CMAC using an embedded Markov chain model to demonstrate the gain of AR-CMAC and to verify it with our simulations. Simulations in an infrastructure network with an IEEE 802.11b/g access point show noticeable improvement than the legacy schemes.

• Proceedings of the Microbiological Society of Korea Conference
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• 1991.04a
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• pp.173-174
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• 1991

• Journal of the Korean earth science society
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• v.25 no.5
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• pp.327-335
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• 2004

The purpose of this study was to investigate the effect of cooperative skill training on problem based learning for elementary school science class. Two experiment groups were involved, in which problem based learning model was used and control group, in which traditional instruction was employed. One of experiment groups was trained in cooperative skills before the instruction. The results demonstrated a significant main effect in the scores of achievement and a significant interaction effect between the instructional strategies and learning ability level. The performance of high-level students in the two experimental groups was higher than that of control group. However, the performance of medium and low-level students trained with cooperative skills training was higher than that of students without cooperative skills training. A significant main effect was also found in self-esteem, but there was no significant interaction between instructional strategies and learning ability. Therefore, this study suggests that cooperative skills training is of great importance for minimizing the free-rider effect and increasing collaborative interaction in cooperative learning.

• The Journal of Fisheries Business Administration
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• v.33 no.2
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• pp.99-125
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• 2002

Fisheries cooperative requires dual characteristics in performing its original function. Economic characteristic as an business enterprise and democratic characteristic as cooperative entity need to complete its objectives and survive in the complex rapidly-changing environment. After IMF crisis, fisheries cooperative received enormous government's financial support and credit-business department is perfectly under government's control. Regional fisheries cooperative also faces business failure, therefore pure cooperative movement can't save the fisheries cooperative. Economic characteristic as an business enterprise is more emphasized than democratic characteristic as cooperative entity in recent years. The theory of corporate ownership and governance can be applied to explain the ownership and governance of fisheries cooperative because fisheries cooperative is now similar to an business enterprise. During the IMF crisis the board, the auditors and the minority shareholders in business enterprise were revealed to be powerless against the mighty influence of controlling shareholders. Unconstrained discretion exercised by those controlling shareholders not only led to the firms'insolvency, but also brought down the country's financial system. During the past few years, Korea has experienced many institutional changes regarding its corporate governance structure. The introduction of outside directors, the strengthening of minority shareholders' rights, and enhanced accounting transparency are achieved to improve the efficiency of economic system. Investors, including institutional and individual, also seem to be more aware of governance issues now. Credit-business department of fisheries cooperative is recommended to introduce the institutions same as the case of the corporate governance structure. Fisheries cooperative except economic and credit-business department requires other prescriptions because it is emphasized as democratic cooperative entity. But we should be careful to interpret the ownership and governance structure because they are products of nations, eras and organizations.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.2
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• pp.301-308
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• 2017

This paper proposes a disturbance observer based controller design method for generating and yawing control of windturbine with two cooperative generators. Windturbine system with two cooperative generators is a distinct structure in which the wind energy supplied by blade axis is converted into electrical energy by two cooperative generators. In this structure, two generators can be controlled independently and therefore they can generate power, simultaneously performing yawing control of nacelle without extra yawing mechanism by cooperatively controlling generating load in appropriate manner. Using this structural trait, this paper designs a disturbance observer based controller that enables the windturbine system with cooperative generators to generate and yaw stably, and verifies the performance of the controller experimentally by applying it to a small-scale windturbine system with the same structure.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.1
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• pp.95-102
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• 2018

This paper proposes a dual lifting and its cooperative control system with two different kinds of floating cranes. The Mega-erection and Giga-erection in the ship building are used to handle heavier and wider blocks and modules as ships and off-shore platforms are enlarged. However, there is no equipment to handle such Tera-blocks. In order to overcome the limit on performance of existing floating cranes, the dual lifting is proposed in this research. In the dual lifting, two floating cranes are well-coordinated to add up the lift capabilities of both cranes without any loss such that virtually a single crane is lifting, maneuvering and unloading. Two main constraints for the dual lifting are as follows: First, two barges of floating cranes should be constrained as a rigid body not to cause a relative motion between two barges and main hooks of the two cranes should be controlled as main hooks of a single crane. In order words, it is necessary to develop the cooperative control of two floating cranes in order to sustain a center of gravity of the module and minimize the tilting angle during the lifting and unloading by the two floating cranes. Two floating cranes are handled as a master-slave system. The master crane is able to gather information about all working conditions and make a decision to control the individual hook speed, which communicates the slave crane by TCP/IP. The developed control system has been embedded in the real floating crane systems and the dual lifting has been demonstrated five times at SHI shipyard in 2015. The moving angles of the lifting module are analyzed and verified to be suitable for hoisting control. It is verified that the dual lifting can be applied for many heavier and wider blocks and modules to shorten the construction time of ships and off-shore platforms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.6
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• pp.1431-1448
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• 2024

Complexity science is a new stage in the development of systems science that is the frontier areas of contemporary scientific development. Complexity science takes complex systems as the research object, which has attracted widespread attention from researchers in the fields of economy, control, management, and society. In recent years, with the rapid development of science and technology and people's deepening understanding for the theory of complex systems, the systems are no longer an object with a single function, but the systems are composed of multiple individuals with autonomous capabilities through cooperative and cooperation, namely multi-agent system (MAS). Currently, MAS is one of the main models for studying such complex systems. The intelligent control is to break the traditional multi-agent fault-tolerant control (FTC) concept and produce a new type of compensation mechanism. In this paper, the applications of fault-tolerant control methods for MASs are presented, and a discussion is given about development and challenges in this field.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.154-154
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• 2000

The cooperative strategy for the teleoperated multi-agent system is presented. And this scheme has been applied to the teleoperated robot soccer system that is newly proposed. For the teleoperated robot soccer system, we made mapping functions to control a 2-wheeled mobile robot using a 2 DoF stickcontroller. The simulation with a real stickcontroller has been evaluated the performance of the proposed mapping function. Then, the basic cooperation strategy has been tested between teleoperated robot and autonomous robot It is shown that the multi-agent system for teleoperation can have a good performance for a job Like a scoring a goal

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.701-706
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• 1994

Holonic manufacturing system is a new approachto the organization and architecture of decentralized, autonomous and cooperative manufacturing system. The new paradigm combines the concepts of hierarchical systems and the integration of autonomous elements in distributed system. Today's scheduling and control techniques are mostly based on a centralized structure. Only little work has been done on scheduling and control of decentralized, autonomous and cooperative manufacturing system. This paper proposes a new approach IPM(Interactive Prediction Method) for scheduling and control of holonic manufacturing system.

• Journal of Korean Elementary Science Education
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• v.29 no.3
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• pp.307-315
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• 2010

In this study, we investigated the effects of cooperative learning by the levels of students' performance goal orientation in science classes on 6th graders' science achievement and science learning motivation. Two classes (47 students) from an elementary school were respectively assigned to a control group and a treatment group. A performance goal orientation test and a science learning motivation test were administered as pretests. The intervention of cooperative learning lasted for 24 class periods. A researcher-made achievement test and the science learning motivation test were administered after the instructions. ANCOVA results indicated that the score of the treatment group was significantly higher than that of the control group in the achievement test. However, no interaction was found between the cooperative learning treatment and the levels of students' performance goal orientation. There were significant aptitude-treatment interactions in science learning motivation.