• Journal of Korean Society of Transportation
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• v.26 no.5
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• pp.175-184
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• 2008

Uncertainties are unavoidable in engineering applications. In this paper we propose an alpha reliable multi-variable network design problem under demand uncertainty. In order to decide the optimal capacity enhancement, three performance measures based on 3E(Efficiency, Equity, and Environmental) are considered. The objective is to minimize the total budget required to satisfy alpha reliability constraint of total travel time, equity ratio, and total emission, while considering the route choice behavior of network users. The problem is formulated as the chance-constrained model for application of alpha confidence level and solved as a lexicographic optimization problem to consider the multi-variable. A simulation-based genetic algorithm procedure is developed to solve this complex network design problem(NDP). A simple numerical example ispresented to illustrate the features of the proposed NDP model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.3
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• pp.221-227
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• 2010

Recent development in seeker technology explores a new seeker design in which, with larger field-of-view (FOV), optical parts are strapped down to a body (hence, called as a body-fixed seeker or a strapdown seeker). This design has several advantages such as comparatively easier maintenance and calibration by removing complex mechanical moving parts, increasing reliability, and cost savings. On the other hand, the strapdown seeker involves difficulties in implementing guidance laws since it does not directly provide inertial LOS rates. Instead, information for generating guidance commands should be extracted by estimating missile/target relative motion utilizing target images on the image plane of a strapdown seeker. In this research, a new framework based on an unscented Kalman filter is developed for estimating missile/target relative motion on the simplified assumption of a point source target. Performance of a terminal guidance algorithm, in which guidance command is generated based on the estimated relative motion, is demonstrated by a missile/target engagement simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.2
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• pp.194-200
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• 2006

The SoC and digital technology development recently enabled the emergence of information devices and control devices because the SoC presents many advantages such like lower power consumption, greater reliability, and lower cost. However, it is nearly impossible to use the SoC without operating systems because the SoC is included with many peripherals and complex architecture. It is required to use embedded operating systems and real-time operating systems may be used as an embedded operating system. So far, real-time operating systems are widely used to implement a Real-Time system since it meets developer's requirements. However, real-time operating systems have disadvantages including a lack of standards, expensive development, and license. Embedded Linux is able to overcome their disadvantages. In this paper, the implementation of control system platform for a mobile robot using real-time Embedded Linux is described. As a control hardware system platform, XScale board is used. As the real-time Embedded Linux, RTAI is adopted which is open source and royalty free, and supports various architectures and real-time devices, such like real-time CAN and real-time COM. This paper shows the implementation of RTAI on XScale board that means the porting procedure. We also applied the control system platform to the mobile robot and compared the Real-Time serial driver with non real-time serial driver. Experimental results show that that using RTAI is useful to build real-time control system with powerful functionalities of Linux.

• The Journal of the Acoustical Society of Korea
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• v.39 no.2
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• pp.105-112
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• 2020

An analysis model of noise map is proposed to evaluate and reduce the acoustical noise of power plant and its surroundings. The sound powers of many noise sources are estimated by measuring the sound levels of major equipments in the power plant. The analysis of noise has been made by using ENPro that is a commercial program for environmental noise prediction. The proposed model is verified by comparing the results from noise analysis and measurement at several points of the power plant units 1 through 4, and residential areas. It is shown that noise map simulation using the proposed model has a reliability, since the overall noise level approximates within the error of ±2 dB. Furthermore, through noise analysis, the increasing effect of noise due to newly established units 5 and 6 on residential areas is also analyzed. Consequently, the noise barrier is designed to meet an environmental noise standard and satisfy low cost and safety conditions.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.2
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• pp.116-124
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• 2012

Wind is an abundant source of natural energy which can be utilized to generate power. Wind velocity does not remain constant, and as a result the output power of wind turbine generators (WTGs) fluctuates. To reduce the fluctuation, different approaches are already being proposed, such as energy storage devices, electric double layer capacitors, flywheels, and so on. These methods are effective but require a significant extra cost to installation and maintenance. This paper proposes to reduce output power fluctuation by controlling kinetic energy of a WTG system. A MW-class pitch-regulated permanent magnet synchronous generator (PMSG) is introduced to apply a power fluctuation reducing method. The major advantage of this proposed method is that, an additional energy storage system is not required to control the power fluctuation. Additionally, the proposed method can mitigate shaft stress of a WTG system. Which is reflected in an enhanced reliability of the wind turbine. Moreover, the proposed method can be changed to the maximum power point tracking (MPPT) control method by adjusting an averaging time. The proposed power smoothing control is compared with the MPPT control method and verified by using the MATLAB SIMULINK environment.

• Advances in aircraft and spacecraft science
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• v.4 no.5
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• pp.515-528
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• 2017

Since composite structures are widely used in structural engineering, delamination in such structures is an important issue of research. Delamination is one of a principal cause of failure in composites. In This study the electrical potential (EP) technique is applied to detect and locate delamination in basalt fiber reinforced polymer (FRP) laminate composite pipe by using electrical capacitance sensor (ECS). The proposed EP method is able to identify and localize hidden delamination inside composite layers without overlapping with other method data accumulated to achieve an overall identification of the delamination location/size in a composite, with high accuracy, easy and low-cost. Twelve electrodes are mounted on the outer surface of the pipe. Afterwards, the delamination is introduced into between the three layers (0º/90º/0º)s laminates pipe, split into twelve scenarios. The dielectric properties change in basalt FRP pipe is measured before and after delamination occurred using arrays of electrical contacts and the variation in capacitance values, capacitance change and node potential distribution are analyzed. Using these changes in electrical potential due to delamination, a finite element simulation model for delamination location/size detection is generated by ANSYS and MATLAB, which are combined to simulate sensor characteristic. Response surfaces method (RSM) are adopted as a tool for solving inverse problems to estimate delamination location/size from the measured electrical potential changes of all segments between electrodes. The results show good convergence between the finite element model (FEM) and estimated results. Also the results indicate that the proposed method successfully assesses the delamination location/size for basalt FRP laminate composite pipes. The illustrated results are in excellent agreement with the experimental results available in the literature, thus validating the accuracy and reliability of the proposed technique.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.21-27
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• 2007

In this study, an approach that installs seismic isolation bearings was proposed for the seismic retrofit of the existing bridges. The method that replaces all existing bearings with seismic isolators was proposed already. However, in this study, we recommend to utilize the existing bearings for the benefit of safety and cost. According to our proposal, the seismic isolators do not support vertical loads but they Just function as the period shifter and the horizontal damper. To verify this approach experimentally, the real scale bearings and lead rubber bearings far the real highway bridges were designed and fabricated. And the responses of this isolated bridges to the assumed earthquakes were determined by the pseudo dynamic test scheme. The test results were also compared to the responses computed by the well known structural analysis software to check the reliability of the test. From the test results, we found that the retrofitted bridges using the proposed method showed stable performances under earthquakes.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.3
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• pp.174-182
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• 2007

There are not many studies on the maintenance and replacement for the ITS equipments. Most of ITS center has no comprehensive regulation on the equipment replacement. This study was focusing on estimation of equipment replacement period and the number of spare parts in stock using the actual failure data of Road Side Equipment (RSE) by Dedicated Short Range Communication (DSRC). The failure data showed a type of bath-tub curves. The data, however, did not fit to any probability distribution curve, which means that the preventive replacement cannot be strongly applied for the RSE. In the aspect of practical strategy, this study suggest that repairing cost and failure frequency be used for decision of replacement of RSE after the 1 or 2 year warrant period. The future study needs to include more RSE failure data as well as other equipments of the ITS.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.48-54
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• 2018

With the 4th industry era, smart factories are emerging. In the era of multi-product small scale production, unmanned transportation vehicles are rapidly increasing in utilization of unmanned transportation vehicles that carry and arrange goods in the work space. The conventional unmanned vehicle detected its position by using the guided line method and the position based method for indoor location recognition and movement. This method has disadvantages of initial high cost and maintenance / maintenance. In this paper, to solve the disadvantages, the method of predicting the direct path of the unmanned vehicle through the Kalman filter is verified using the white LED marker of the warehouse and the position data and the image data of the white LED marker recognition image. Through this, the reliability of the linear movement which occupies the most part in the lattice structure is secured. It is also expected that the reliance on additional position sensors will also be reduced.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.281-290
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• 2003

Co Evolutionary Structural Design(CESD) Framework is presented, which can deal with the load design and structural topology design simultaneously. The load design here is the exploration algorithm that finds the critical load patterns of the given structure. In general, the load pattern is a crucial factor in determining the structural topology and being selected from the experts어 intuition and experience. However, if any of the critical load patterns would be excluded during the process of problem formation, the solution structure might show inadequate performance under the load pattern. Otherwise if some reinforcement method such as safety factor method would be utilized, the solution structure could result in inefficient conservativeness. On the other hand, the CESD has the ability of automatically finding the most critical load patterns and can help the structural solution evolve into the robust design. The CESD is made up of a load design discipline and a structural topology design discipline both of which have the fully coupled relation each other. This coupling is resolved iteratively until the resultant solution can resist against all the possible load patterns and both disciplines evolve into the solution structure with the mutual help or competition. To verify the usefulness of this approach, the 10 bar truss and the jacket type offshore structure are presented. SORA(Sequential Optimization & Reliability Assessment) is adopted in CESD as a probabilistic optimization methodology, and its usefulness in decreasing the computational cost is verified also.