• Proceedings of the KSR Conference
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• 2000.05a
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• pp.172-179
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• 2000

The automatic/driverless operation which are great important techniques in metro railway are required to increase higher safety, greater reliability, and transport capacity. To satisfy such demands, we must have the system design iかd testing technique for the railway system operation. These techniques are related to the onboard train control and communication systems which include TCMS(Train Control md Monitoring System), ATO(Automatic train Operation), ATC(Automatic train Control), and TWC(Train to wayside communication). These sub-systems must be interfacing with not only each others but also the signal system on the ground. We tested the train control system on Test line that has been developed on the basis of the standardized type EMU for korea railway systems. This test line which is located in Sangju, have been constructed for testing 7 ＆ 8 line of Seoul Metro railway.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.243-253
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• 2008

This paper deals with the analysis, design, and implementation of a single phase AC-DC Zeta converter with high frequency transformer isolation and power factor correction(PFC) in two modes of operation, discontinuous current mode of operation(DCM), and continuous current mode of operation(CCM). A Digital Signal Processor(DSP) based implementation is carried out for validation of the Zeta converter developed design in discontinuous mode of operation. A comparison of both modes of operation is presented for a 1kW power rating from the point of view of steady state and dynamic behavior, power quality, simplicity, control technique, device rating, and converter size. The experimental results of a developed prototype of Zeta converter are presented for validation of the developed design. It is observed that CCM is most suitable for higher power applications where it requires some complex control and sensing of the additional variables.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.6
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• pp.615-624
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• 1992

For the operation of the resonant DC link inverters, only limited number of modulation techniques such as the delta modulation and instantaneous current control techniques have been suggested. However, these modulation techniques have some limitations in practical operation. In this paper, the application of conventional inverter modulation techniques is suggested for the control of the resonant DC link inverter. The harmonic analysis results are presented. The results show that these modulation techniques offer good output characteristics similar to conventional inverter PWM techniques for the operation of the resonant DC link inverter. This implies that not only the delta modulation technique and instantaneous current control techniques but also various other modulation techniques can be applied to the operation of the resonant DC link inverter. This also indicates that open loop control as well as closed loop control can be used for the operation of the resonant inverter. The resonant DC link inverter with various modulation strategies is implemented using V-40 microprocessors.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.158-162
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• 2002

The parallel operation system of multiple UPS(Uninterruptible Power Supply) is used to increase power capacity of the system or to secure higher reliability at critical loads. In the parallel operation of the two UPSs, the load sharing control to maintain the current balance between them is a matter of consequence. In this paper, a highly precise load sharing controller is proposed and implemented for the parallel operation system of two UPSs. After that, a good performance of the proposed method is verified by simulation in the parallel operation system with two UPSs.

• Journal of Periodontal and Implant Science
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• v.38 no.3
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• pp.483-492
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• 2008

Purpose: The purpose of this study was to compare clinical effect of the Langer & Langer technique, the modified Langer & Langer technique and Bruno technique. Material and Methods: 30 patients who have gingiva recession(Miller class I or class II) were carried root coverage. Langer & Langer technique(14 patients/32 tooth), modified Langer & Langer technique(5 patients/10 tooth) and Bruno technique(11 patients/18 tooth) was carried. At baseline and average 3 months after operation, it was estimated clinical index(Pocket depth, gingiva recession, clinical attachment level, keratinized gingiva, scar tissue, root coverage rate) by Williams style probe. Result: Root coverage rate is indicated Langer & Langer technique(8S%), Modified Langer & Langer technique(86%) and Bruno technique(90%). Conclusion: All three of the procedures were effective in gingival recession and improved clinical parameters.

• The Journal of the Korean dental association
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• v.49 no.11
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• pp.670-678
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• 2011

Various sorts of dental devices for the dental treatment have been introduced and adopted during past several years. Dental Laser, among all devices, seems to be possible for applying to over the whole treatments and widely employed. Furthermore, this article is to introduce that Dental Laser is intended to care patients secured with the effectual treatment against Conventional procedures based upon its studies. The advantages of Dental Laser treatment-along with LLLT (Low Level Laser Therapy) effect, biostimulation effect, and minimal invasive technique - make the patients reduce their fear of the operation, lighten the inconvenience of post operation, and shorten the treatment period. In particular, it is worth considering that the use of laser-assisted therapies is associated with a marked reduction in the use of analgesics and anti-inflammatory medications compared with conventional procedures. This article is to state advantages and differences of Dental Laser treatment compared with Conventional procedures, and to emphasize to become well-acquainted with the precautions for safety and effective Dental Laser treatment. In case of operating Dental Laser with lack of the instructions, it will cause the unpredicted fatal results; therefore this treatment requires special care in its operation. Henceforward, it is anticipated that infinite treatment protocols will be introduced by applying Dental Laser, and this is to address the utilization of Dental Laser.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.4
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• pp.518-524
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• 1997

Experimental studies on combustion phenomena within a porous ceramic burner are reported. Main interest of the present work is to investigate fundamental flame behaviors and their effects on the burner operation. Due to high thermal capacity of the porous ceramic materials, the response of flame to burning condition changes is slow and thus to have a stabilized flame is quite difficult and takes much time. It is found that the temperature profile obtained at downstream of the flame zone is not much sensitive to the movement of flame and the speed of flame movement is less than 0.1 mm/sec for the conditions tested. With the premixed LPG/air flame imbedded within the porous ceramic burner, stable combustion regions and unstable combustion regions leading to blowoff or flashback phenomena are observed and mapped on flow velocity versus equivalence ratio diagram. For the development of burner operation technique which is more practical and safe, intermittent burning technique, where the fuel or/and air is supplied to the burner intermittently, is proposed as one of the flame control methods for the porous ceramic burner and tested in this study. Through the experiment, it is realized that the proposed method is acceptable in respect to burner performance and give much flexibility in the operation of porous ceramic burner.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1993.05a
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• pp.77-77
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• 1993

Laryngeal web is formed from various causes, and it is a scar tissue covered with epithelium on both sides. The purpose of the laryngeal web surgery is to cover the vocal cords with healthy epithelium and to achieve the normal or near normal function of respiration and phonation. Until now, a lot of surgical procedures were introduced, but have some merits and disadvantages. Recently authors tried this new surgical technique on 6 patients using the suspension laryngomicroscope under the intubation general anesthesia, which was to suture the upper and lower edges of the severed web. This new approach has several advantages; 1) familiar instruments and visual field 2) no unnecessary surgical trauma beyond the operation field 3) one stage operation 4) shorter operation time 5) no serious complications 6) short hospitalization, etc.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.662-674
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• 1997

In order to post process the vector-quantized images employing the theory of projections onto convex sets or the constrained minimization technique, the the projector onto QCS(quantization constraint set) as well as the filter that smoothes the lock boundaries should be investigated theoretically. The basic idea behind the projection onto QCS is to prevent the processed data from diverging from the original quantization region in order to reduce the blurring artifacts caused by a filtering operation. However, since the Voronoi regions in order to reduce the blurring artifacts caused by a filtering operation. However, since the Voronoi regions in the vector quantization are arbitrarilly shaped unless the vector quantization has a structural code book, the implementation of the projection onto QCS is very complicate. This paper mathematically analyzes the projection onto QCS from the viewpoit of minimizing the mean square error. Through the analysis, it has been revealed that the projection onto a subset of the QCS yields lower distortion than the projection onto QCS does. Searching for an optimal constraint set is not easy and the operation of the projector is complicate, since the shape of optimal constraint set is dependent on the statistical characteristics between the filtered and original images. Therefore, we proposed a hyper-cube as a constraint set that enables a simple projection. It sill be also shown that a proper filtering technique followed by the projection onto the hyper-cube can reduce the quantization distortion by theory and experiment.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.65-69
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• 2018

Due to large in-field current carrying capacity and strong mechanical strength, a REBCO wire has been regarded as a viable high temperature superconductor (HTS) option for high field MRI and > 1 GHz (>23.5 T) NMR magnets. However, a REBCO magnet is well known to have an inherent problem of field inhomogeneity, so-called 'Screening Current induced magnetic Field (SCF)'. Recently, 'field shaking' and 'current overshoot operation' techniques have been successfully demonstrated to mitigate the SCF and enhance the field homogeneity by experiments. To investigate the effectiveness of current overshooting operation technique, a numerical simulation is conducted for a test REBCO magnet composed of a stack of double pancake coils using '2D edge-element magnetic field formulation' combined with 'domain homogenization' scheme. The simulation result demonstrates that an appropriate amount of current overshoot can negate the SCF. To verify the simulation results, current overshoot experiments are conducted for the REBCO magnet in liquid nitrogen. Experimental results also demonstrate the possible application of current overshoot technique to mitigate the SCF and enhance the field homogeneity.