• Nuclear Engineering and Technology
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• v.17 no.4
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• pp.247-255
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• 1985

This paper describes a new method for the design of variable structure model-following control systems(VSMFC). This design concept is developed using the theory of variable structure systems (VSS) and slide mode. The new results are presented on the sliding control methodology to achieve accurate tracking for a class of nonlinear, multi-input multi-output(MIMO), time varying systems in the presence of parameter variations. The design requires little computational effort. The dynamic response is insensitive to parameter variations. The feasibility and the advantages of the method are illustrated by applying it to a 1000 MWe boiling water reactor(BWR). The control is studied in the range of 85%∼90% of rated power for load-following control. A set of 12 nonlinear differential equations is used to simulate the total plant. A 6-th order linear model has been developed from these equations at 85% of rated power. The obtained controller is shown by simulations to be able to compensate for a plant parameter variation over a wide power range.

• Journal of Korea Society of Industrial Information Systems
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• v.5 no.2
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• pp.22-31
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• 2000

The VB5.2 interface of B-lSDN, that is located between an access network and a service node, allows dynamic allocation and release of ATM resources. In this paper, we propose the B-ANCC protocol of the VB5.2 interface to minimize the overall connection setup delay by introducing the access network. The B-ANCC protocol enhances the B-BCC protocol and adopts a parallel interworking function with signaling protocols in the service node. To confirm the correctness of the proposed B-ANCC protocol, we validate it using the automated validation tool, SPIN. We analyze and simulate the sequential interworking model based on the B-BCC protocol and the parallel interworking model based on the B-ANCC protocol, in terms of a connection setup delay and a completion ratio. It is shown that our proposed parallel interworking model with B-ANCC reduces a setup delay and improves a completion ratio compared to the sequential interworking model with B-BCC.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.4
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• pp.405-418
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• 2014

Fuel cells are suitable for a power plant of a unmanned aerial vehicle (UAV) as it is not only environmentally friendly and quiet but also more efficient than an internal combustion engine. A fuel cell hybrid UAV has better performance in endurance than a fuel cell only or battery only UAV. One of the key purposes of making fuel cell hybrid UAVs is having long endurance and now maximum 26 hours of flight is possible. Because optimal design and control methods for fuel cell hybrid UAVs are absolutely needed for their long endurance we have to check the methods. The aircraft made by using application-integrated design method has less BOP mass and better performances. The optimal design and control methods are generally based on computer simulations or Hardware-In-The-Loop simulations by using dynamic models for their design and control. The Hardware-In-The-Loop simulation (HILS) is to use a hardware device like a fuel cell stack as well as a simulation program and it allows for making optimally designed applications. This paper introduce efficient methods of design, control and evaluation for the fuel cell hybrid UAVs.

• Journal of the Korea Convergence Society
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• v.8 no.4
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• pp.9-18
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• 2017

UAVs began to be actively applied to so-called 3D jobs, including the autonomous exploration, investigation, mapping, search and rescue, etc. since the mid-2000s. With this global trend, having a precise controllability of the UAV will certainly revolutionize the life of the modern human in the aspect of tremendous applications of the UAV. In the first part, a simplified dynamic model of the UAV identified using system identification techniques is compared with the previously built time-discrete linear model. In the second part, the three parameters of the dynamic model are estimated using the batch and RLS methods. Angular acceleration data of the quadrotor UAV at the hovering maneuver are analyzed and shown to be converging at all time. Also, according to the quadrotor flight data from both experiments and MATLAB simulations, the batch estimation method turns out to be more accurate than the RLS estimation method based on the comparison of final parameter values.

• Magazine of the Korea Concrete Institute
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• v.20 no.6
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• pp.28-35
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• 2008

The Burj Dubai Project will be the tallest structure ever built by man; when completed the tower will be more than 700 meter tall and more than 160 floors. While the early integration of aerodynamic shaping and wind engineering considerations played a major role in the architectural massing and design of this multi-use/residential tower, where mitigating and taming the dynamic wind effects was one of the most important design criteria, the material selection for the structural systems of the tower was also a major consideration and required detailed evaluation of the material technologies and skilled labor available in the market at the time Concrete was selected for its strength, stiffness, damping, redundancy, moldability, free fireproofing, speed of construction, and cost effectiveness. In addition, the design challenges of using concrete for the design of the structural system components will be addressed. The focus on this paper will also be on the early planning of the concrete works of the Burj Dubai Project.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.2
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• pp.131-137
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• 2006

In swarm robot systems, each robot must behaves by itself according to the its states and environments, and if necessary, must cooperates with other robots in order to carry out a given task. Therefore it is essential that each robot has both learning and evolution ability to adapt the dynamic environments. In this paper, the new learning and evolution method based on reinforcement learning having delayed reward ability and distributed genetic algorithms is proposed for behavior learning and evolution of collective autonomous mobile robots. Reinforcement learning having delayed reward is still useful even though when there is no immediate reward. And by distributed genetic algorithm exchanging the chromosome acquired under different environments by communication each robot can improve its behavior ability. Specially, in order to improve the performance of evolution, selective crossover using the characteristic of reinforcement learning is adopted in this paper. we verify the effectiveness of the proposed method by applying it to cooperative search problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8A
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• pp.613-619
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• 2003

Bluetooth is a communication technology enabling short-range devices to be wirelessly connected. A master and one or more slave devices are connected to form a piconet, and piconets are joined to form a scatternet. The units participating in two or more piconets in a scatternet, is called bridge or gateway nodes. In order to operate the scatternet efficiently, both piconet scheduling for the master and slaves of a piconet, and scatternet scheduling for the bridge nodes are playing important roles. In this paper, we propose a traffic-adaptive dynamic scatternet scheduling algorithm based on rendezvous points and rendezvous windows. The performance of the proposed algorithm is compared and analyzed with that of a static scheduling algorithm via simulations. Simulation results show that our algorithm can distribute wireless resources efficiently to bridge nodes depending on the traffic characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.8B
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• pp.904-909
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• 2011

Cell zooming adjusts the cell range of base stations depending on traffic condition. The cell zooming can be implemented by the adjustment of antenna angles, the clustering of the base stations, and the cell relay. The base stations can adjust the cell range in term of energy efficiency, which can then reduce the overall energy consumption of cellular networks. There is, however, a trade-off between the energy savings and the blocking probability of user calls. A periodic scheme that manages the cell zooming of the base stations was proposed but it was inadequate for dealing with the dynamic nature of traffic patterns. This paper proposes a semi-periodic cell zooming scheme along with the algorithms that select such base stations and define the operation procedure. Simulation results show that the proposed method outperforms the existing scheme in terms of the energy savings without the degradation of the blocking probability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.558-564
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• 2007

3G Long Term Evolution, which aims for various mobile multimedia service provision by enhanced wireless interface, proposes VoIP-based voice service through a Packet Switching (PS) domain. As delay and loss-sensitive VoIP traffic flows through the PS domain, more challenging technical difficulties are expected than in Circuit Switching (CS) domain based VoIP services. Moreover, since 3G LTE, which adopts the OFDM as its physical layer, introduces Physical Resource Block (PRB) as a unit for transmission resources, new types of resource management schemes are needed. This paper proposes a PRB scheduling algorithm of MAC layer for VoIP service in 3G LTE and shows the simulation results. The proposed algorithm has two key parts; dynamic activation of VoIP priority mode to satisfy VoIP QoS requirements and adaptive adjustment of the priority mode duration in order to minimize the degradation of resource utilization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9A
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• pp.905-915
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• 2007

This paper proposes a filter-based algorithm to adaptively adjust the contention window in IEEE 802.11 DCF. The proposed mechanism is focused on the general and realistic environments that have various conditions regarding to noise, media types and network load. For this flexible adaptation, Filter-based DCF(FDCF) takes a more realistic policy such as median filter concept in the image processing technologies. We can handle these various environments by adjusting the contention window size according to the result of filtering based on history-buffer. We can ignore temporarily and randomly occurred transmission failures due to noise errors and collisions in noisy environments. In addition, by changing the reference number and history-buffer size, FDCF can be extended as a general solution including previous proposed mechanism. We have confirmed that the proposed mechanism can achieve the better performance than those of previous researches in aspects of the throughput and the delay in the realistic environments.