• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.451-459
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• 2018

This work presents an approach for modeling of electric vehicle considering the vehicle dynamics, drive train, rotational wheel and load dynamics. The system is composed of IPMSM (Interior Permanent Magnet Synchronous Motor) coupled with the wheels through a drive train. Generally, IPMSM is controlled by ordinary PID controllers. Performance of the ordinary PID controller is not satisfactory owing to the difficulties of optimal gain selections. To overcome this problem, a new type of fuzzy logic gain tuner for PID controllers of IPMSM is required. Therefore, in this paper fuzzy logic based gain tuning method for PID controller is proposed and compared with some previous control techniques for the better performance of electric vehicle with an optimal balance of acceleration, speed, travelling range, improved controller quality and response. The model was developed in MATLAB/Simulink, simulations were carried out and results were observed. The simulation results have proved that the proposed control system works well to remove the transient oscillations and assure better system response in all conditions.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.1
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• pp.61-69
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• 2005

The topology of NPC inverter coupled with the large number of devices used increases the probability of device failure. It's necessary to develop an optimal remedial strategy which can be used to continue the application when fault occurs. The fault tolerance is obtained by the use of the proposed method. The proposed method utilizes that the one phase load with the failed power device could be connected to the center-tap of the DC-link capacitor in order to dc-link voltage with balance and the sinusoidal phase current with constant amplitude under the single power device fault condition. The strategy described in this paper is expected to provide an economic alternative to more expensive redundancy techniques.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.591-600
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• 2015

The efficiency of a powertrain system of hybrid vehicle is highly dependent on the design and control of the hybrid powertrain system. In other words, the optimal design of the powertrain systems is coupled with optimal control of the powertrain system. Therefore, the solution of an optimal design problem for hybrid vehicles is computationally and timely very expensive. For example, dynamic programming, which is a recursive optimization method, is usually used to evaluate the best fuel economy of certain hybrid vehicle design, and, thus, the evaluation takes tens of minutes to several hours. This research aims to accelerate the speed of efficiency evaluation of hybrid vehicles. We suggest a mathematical treat and a methodological treat to reduce the computational load. The mathematical treat is that the dynamics of system is discretized with sparse sampling time without loss of energy balance. The methodological treat is that the efficiency of the hybrid vehicle is inferred by characteristic loss evaluation that is computationally inexpensive. With the suggested methodology, evaluating a design candidate of hybrid powertrain system is taken few minutes, which was taken several hours when dynamic programming is used.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.165-173
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• 2007

This paper introduces a new current sharing technique to Interleaved Boost Converter (IBC) using carrier slope control. The IBC is able to boost the input voltage and operates at higher current levels and has various advantages over a single power module. However, how to balance the current each module is still important problem. To solve this problem, the proposed technique can distribute the power and load current equally based on master-slave current sharing method. Unlike a conventional approach, this technique can be extended even though the current stress of switching components at slave modules is significantly smaller than that of the master module. The simulation and the experimental results are presented to show the validity.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.261-265
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• 2004

This paper proposes a fuzzy dual method for analyzing long-term transmission system expansion planning problem considering ambiguities of the power system using fuzzy lineal programming. Transmission expansion planning problem can be formulated integer programming or linear programming with minimization total cost subject to reliability (load balance). A long-term expansion planning problem of a grid is very complex, which have uncertainties fur budget, reliability criteria and construction time. Too much computation time is asked for actual system. Fuzzy set theory can be used efficiently in order to consider ambiguity of the investment budget (economics) for constructing the new transmission lines and the delivery marginal rate (reliability criteria) of the system in this paper. This paper presents formulation of fuzzy dual method as first step for developing a fuzzy Ford-Fulkerson algorithm in future and demonstrates sample study. In application study, firstly, a case study using fuzzy integer programming with branch and bound method is presented for practical system. Secondly, the other case study with crisp Ford Fulkerson is presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3789-3809
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• 2015

In this paper, we deal with the problem of M2M gateways' network selection for different types of M2M traffic in heterogeneous wireless networks. Based on the difference in traffic's quality of service (QoS) requirements, the M2M traffic produced by various applications is mainly classified as two categories: flexible traffic and rigid traffic. Then, game theory is adopted to solve the problem of network-channel selection with the coexistence of flexible and rigid traffic, named as flexible network access (FNA). We prove the formulated discrete game is a potential game. The existence and feasibility of the Nash equilibrium (NE) of the proposed game are also analyzed. Then, an iterative algorithm based on optimal reaction criterion and a distributed algorithm with limited feedback based on learning automata are presented to obtain the NE of the proposed game. In simulations, the proposed iterative algorithm can achieve a near optimal sum utility of whole network with low complexity compared to the exhaustive search. In addition, the simulation results show that our proposed algorithms outperform existing methods in terms of sum utility and load balance.

• Proceedings of the KIEE Conference
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• summer
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• pp.421-423
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• 2004

As power system grows more complex and power demands increase, the fault current tends to gradually increase. In the near future, the fault current will exceed a circuit breaker rating for some substations, which is an especially important issue in the Seoul metropolitan area because of its highly meshed configuration. Currently, the Korean power system is regulated by changing the 154kV system configuration from a loop connection to a radial system, by splitting the bus where load balance can be achieved, and by upgrading the circuit breaker rating. A development project applying 154kV Superconducting Fault Current Limiter(SFCL) to 154kV transmission systems is proceeding with implementation slated for after 2010. In this paper, the expected price of SFCL in order to assure the economic feasibility is evaluated comparing with upgrading cost of ciui.1 breakers. The results show that the SFCL should be developed under seven times of price of circuit breaker to be competitive against upgrading circuit breakers.

• Journal of TMJ Balancing Medicine
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• v.8 no.1
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• pp.6-10
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• 2018

In order to propose a fundamental and appliable theories for balancing therapy of temporomandibular joint (TMBT), evolutionary proofs and up-down theories in evolutionary biology and Korean medicine were investigated. Balancing therapy of temporomandibular joint treats disorder and diseases of the whole body through straightening of the abnormal linking between temporomandibular joint and axis. Although the mechanism of this therapy contains many merits like multicellular integrity and coadjustment, ease of balance and alert forward mobility by the bipedal stepping and evolution to Homo sapiens, increasing disadvantages of balancing pressure of right and left in the lengthened perpendicular axis and the balancing load of temporomandibular joint and axis following the reactional change of dental occlusion are deeply related and considered in this therapy. As for up-down theory, crossing of heavenly qi and earth qi centering on cervical joint is presented as the first mechanism for TMBT, and the other ones like in-out and up-down qi activity of tripple energizer, up-down of essence-qi-spirit in the three backbone barrier and three cinnabar field, up-down of yin-yang-water-fire of viscera and bowels can be related too.

• Journal of Trauma and Injury
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• v.32 no.3
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• pp.187-193
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• 2019

Many techniques have been developed for reconstruction of the hand; however, less attention has been paid to foot reconstruction techniques. In particular, reconstruction of the forefoot and big toe has been considered a minor procedure despite the importance of these body parts for standing and walking. Most of the weight load on the foot is concentrated on the forefoot and big toe, whereas the other toes have a minor role in weight bearing. Moreover, the forefoot and big toe are important for maintaining balance and supporting the body when changing directions. Recently, attention has been focused on the aesthetic appearance and functional aspects of the body, which are important considerations in the field of reconstructive surgery. In patients for whom flap reconstruction in the forefoot and big toe is planned, clinicians should pay close attention to flap survival as well as functional and cosmetic outcomes of surgery. In particular, it is important to assess the ability of the flap to withstand functional weight bearing and maintain sufficient durability under shearing force. Recovery of protective sensation in the forefoot area can reduce the risk of flap loss and promote rapid rehabilitation and functional recovery. Here, we report our experience with two cases of successful reconstruction of the forefoot and big toe with a sensate anterolateral thigh flap, with a review of the relevant literature.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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• pp.23-28
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• 2019

In recent years, medium- to large-scale transportation machinery and machine tool manufacturing process lines have shown a trend toward centralization, softening, lightening, and slimming to reduce costs and increase productivity. This has increased the demand for vertical articulated robots. When developing and introducing a heavy weight-handling robot that can be easily applied to existing production lines, it is expected to have a great effect in securing industrial competitiveness by solving industrial issues such as the decreased productivity and increased risk of accidents due to work involving heavy lifting. In this study, we design a 6-axis robot mechanism with a heavy load-handling capacity of 700kg or more for large-sized materials of various types supplied in small quantities.