• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.145-150
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• 2006

The paper deals with integrated navigation and sense & avoid systems for small unmanned aerial vehicles (UAV). First an introduction to the current UAV activities of the institute is given. It is followed by an overview about the integrated navigation system developed for small UAVs. The system is based on a tightly-coupled GPS/INS architecture. But instead of using delta-ranges, time-differenced carrier phases are used to aid the INS. Finally, results from navigation filter validation in flight tests are presented. After that an overview about sense and avoid strategies for application in small unmanned aircraft is given. From this a guideline for developing such a system for the institute's UAVs is presented.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.25 no.4
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• pp.83-90
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• 2017

Unmanned Aerial Vehicles(UAVs) require collision avoidance capabilities equivalent to the capabilities of manned aircraft to enter the airspace of manned aircraft. In the case of Visual Flight Rules of manned aircraft, collision avoidance is performed by 'See-and-Avoid' of pilots. To obtain those capabilities of UAVs named as 'Sense-and-Avoid', sensor-system-based intruder tracking and collision avoidance methods are required. In this study, a multi-sensor-based tracking, data fusion, and collision avoidance algorithm is designed by using a model-based design tool MATLAB/SIMULINK, and validations of the designed model and code using numerical simulations and processor-in-the-loop simulations are performed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.565-568
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• 2004

Facilities Sharing is defined as the access providers who is holding the telecommunications facilities rent their facilities to the access seekers who is not holding them to promote the fair competition among carriers in a narrow sense and to avoid the duplication of investment in a broad sense. MIC, the regulator in Korea, has revised the current policy of facilities access toward mandatory system. The purpose of this paper is to review the pricing principle of facilities sharing in major countries and to discuss the implications of this case study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.12
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• pp.4617-4632
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• 2021

IEEE 802.11ax is a protocol being developed for high-density Wireless Local Area Networks (WLAN). Several algorithms have been proposed to improve the level of spatial reuse applied in IEEE 802.11ax. However, these algorithms are tentative and do not specify how to select the transmit power and carrier sense threshold in practice; It is unclear when and why the tuned parameters lead to better network performance. In this paper, we restricted the scale of transmit power tuning to prevent the case of backfire in which spatial reuse will result in transmission failure. If the restrictions cannot be satisfied, spatial reuse will be abandoned. This is why we named the proposed scheme as Arbitration based Spatial Reuse (ASR). We quantified the network performance after spatial reuse, and formulate a corresponding maximum problem whose solution is the optimal carrier sense threshold and transmit power. We verified our theoretical analysis by simulation and compared it with previous studies, and the results show that ASR improves the throughput up to 8.6% compared with 802.11ax. ASR can avoid failure of spatial reuse, while the spatial reuse failure rate of existing schemes can up to 36%. To use the ASR scheme in practice, we investigate the relation between the optimal carrier sense threshold and transmit power. Based on the relations got from ASR, the proposed Relation based Spatial Reuse (RSR) scheme can get a satisfactory performance by using only the interference perceived and the previously found relations.

• International Journal of Advanced Culture Technology
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• v.11 no.1
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• pp.221-231
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• 2023

Nowadays, more and more countries are paying attention to basic teaching, so it can be found that they are carrying out a new round of basic teaching reform. The fundamental purpose is to adapt to the economic, cultural and technological development of the 21st century, so that their nationals will not be eliminated in the competition of the world environment, the spiritual civilization and material life of the nationals can be further improved, and they can have an advantage in the competition and catch up with the advanced level of the world. The cultivation of preschoolers' mental health determines the future development of a person. Through the long-term practice of art teaching at the Longyuan Branch of the District Third Kindergarten of Guangxi, This paper summarizes some effective teaching methods to cultivate children's connection ability and sense of security through aesthetic education.Firstly, preschoolers' contact ability was studied, and the aspects such as the definition of contact ability and the reasons for the formation of contact ability were explored. Secondly, the development of preschoolers' sense of security, what to avoid in order to develop a good sense of security and the effects of security on children were investigated. Finally, several specific teaching cases were written based on these theories. Through these cases, aesthetic education was utilized to promote preschoolers' contact ability and develop a sense of security. The study mainly draws the following conclusions that if children want to have a successful career, a happy family in the future, it is crucial to have the ability of connect and security in childhood. Aesthetic education can promote the formation of children's ability of connection and security.Finally, I write specific teaching cases based on the above theories and practice, through which these cases use aesthetic education to promote the formation of children's contact ability and sense of security.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.6
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• pp.1060-1064
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• 2006

Data collected by sensors in field are transmitted to the base station gathering all of data. Because sensors have to gather data in surroundings and periodically transmit data to the base station, it makes energy consumed much. In this paper, we mose the scheme that is to avoid traffic congestion with achievement of energy efficiency, so collected data is transmitted efficiently. This is to adjust transmission rate differently in case of increasing or decreasing traffic and minimize the energy consumption with setting ideal options up basic CSMA(Carrier Sense Multiple Access) protocol in each sensor. Through the simulation, we find the ideal CSMA options and apply the proposed scheme of traffic control mechanism to them and analyze them, then show energy efficiency and effective traffic control mechanism.

• Journal of applied mathematics & informatics
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• v.6 no.3
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• pp.823-834
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• 1999

The present paper deals with the problem of nonselective harvesting in a partly infecte prey and predator system in which both the suseptible prey and the predator follow the law of logistic growth and some preys avoid predation by hiding. The dynamical behaviour of the system has been studied in both the local and global sense. The optimal policy of exploitation has been derived by using Pontraygin's maximal principle. Numerical analysis and computer simulation of the results have been performed to inverstigate the global properties of the system.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.49-52
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• 2003

IEEE 802.11 MAC uses a distributed coordination function (DCF) known as carrier sense multiple access with collision avoidance (CSMA/CA) for medium access. Random back-off algorithm helps to avoid the collision. This paper proposes virtual back-off and modified back-off algorithm for reduce a waiting time by back-off and reduce the collision. The modified DCF is consisted of these two algorithms. We expect to reduce the average waiting time of each transmission by using the modified DCF algorithm.

• Journal of Advanced Navigation Technology
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• v.19 no.4
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• pp.288-298
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• 2015

For the commercialization of unmanned aircraft, we must validate the safety of the air/ground collision alert systems (CAS). The validation procedure of CAS requires the flight test which is not only expensive but also dangerous. To alleviate this problem, we need the simulation based validation process for the CAS. We developed an integrated UAV simulation (IUS) environment which interconnect the flight simulator, the Matlab/Simulink, and a target avionics simulation model. We developed the collision warning module of the TCAS and tested using IUS and flight encounter models. Using IUS, we can evaluate the performance and reliability of a target avionic system at the preliminary design stage of a development life cycle.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.6
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• pp.1294-1305
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• 2013

The aim of this study was to identify the attitude of nursing students' toward death using Q-methodology and to obtain baseline data to improve nursing students' education program on death. Twenty-nine participants at a college classified 40 Q-statements on a one to nine scale. The resultant Q-sort was a matrix representing the participant's operant subjectivity on the issue under consideration. The results of above procedures were analyzed by PQ Method. The results revealed that there are three types of perception about nursing students' attitudes toward the death. The categories were labeled positive-perspective, pain-avoid and preparation-deficiency. Positive-perspective individuals have a positive sense of their life and death. Thus, they would not fear death, believing in an after-life world, while being positive towards donation of intestines after death. Pain-avoid individuals hope life and death without pain. Preparation-deficiency individuals are unprepared to die. In conclusion, this study discovers three types of the perception about nursing students' attitudes toward the perception of death. By identifying the nature of each of these types, this study can be useful to develop efficient strategies for education program on death.