• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.456-458
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• 1997

The phase-lock technique is applied to a three-phase semi-bridge type battery charger system. Using an inner fast dynamic loop, the phase-locked voltage control (PLVC) technique of three-phase semi-bridge converter is proposed to give a frequency synchronism and to reduce the subharmonics due to the unbalance of transformer or power line. To protect the power devices, the two stage soft-start, function with softly locking the phase and softly increasing the current is presented. As limiting the reference voltage of the inner voltage control loop, muti-lock phenomena are removed on the PLVC loop. A current limit function is also proposed to limit the current of battery and converter. The proposed controller is confirmed through experiment results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.223-228
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• 2006

The main purpose of this paper is to describe the code tracking performance of a non-coherent digital delay lock loop (DLL) or coherent DLL while tracking GNSS signal in the presence of signal masking. The masking effect is usually caused by buildings that obscure the signal in either a periodic or random manner. In some cases, ideal masking is used to remove random or periodic interference. Three types of the masked signal are considered - no masking, periodic masking, and random masking of the signal input to the receiver. The mean time to lose lock (MTLL) of the code tracking loop are evaluated, and some numerical result and simulation results are reported. Finally, the steadystate tracking errors on the performance of the tracking loop in interference environment are also presented.

• Journal of Korea Multimedia Society
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• v.18 no.1
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• pp.71-80
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• 2015

Many researches have been studied to overcome the weak points in authentication schemes of mobile devices such as pattern-authentication that is vulnerable for smudge-attack. Since random-pattern-lock authenticates users by drawing figure of predefined-shape, it can be a method for robust security. However, the authentication performance of random-pattern-lock is influenced by input noise and individual characteristics sign pattern. We introduce an optimization method of user input direction to increase the authentication accuracy of random-pattern-lock. The method uses the likelihood of each direction given an data which is angles of line drawing by user. We adjusted recognition range for each direction and achieved the authentication rate of 95.60%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.305-310
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• 2007

This paper presents a damper system design in torque converter to minimize the vibration in powertrain of automatic transmission vehicle. The lock-up clutch in torque converter makes engine and transmission connected directly. When the lock-up clutch is engaged the torque fluctuation of engine is attenuated by the damper system. This function decides the vehicle power-train dynamic characteristics. At first, the dynamic hysteresis effect with any self and surface to surface contact problems of the damper springs in the damper system for torque converter is analyzed by using FEM. It is shown that these simulation results have a good design reference to energy dissipation operating by damper system in torque converter. And, to calculate dynamic characteristics, the vehicle model is structured by using $AMESim^{(R)}$?? that is a common use program. The vehicle model shows the frequency response of vehicle by changing the stiffness of damper spring, and these results lead the most suitable stiffness of spring. Also, new damper system is analyzed resonance frequency variation and is compared with prior damper.

• Journal of Korean Port Research
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• v.12 no.2
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• pp.233-242
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• 1998

The Inchon port has been heavily congested due to the tidal restriction in passing the lock and the shortage of berths or warehouses. The current congestion is predicted to become worse by the induced traffics near the lock entrance after completion of North harbour expansion and of Kyung-In canal construction. It is also expected that the newly developed configuration of the Inchon port will result in increasing the rate of marine accidents around the lock entrance because of the over-utilization of the limited capacity of the junction from the North harbour and the Kyung-In canal. This study adopts a systematic approach in analysing the physical distribution system of the inner-lock area in order to figure out alternative routes which are designed to improve the port efficiency. Ship maneuvering simulation is also attempted to propose a new approaching route to the canal as an alternative path in order to avoid the traffic accidents caused by the extreme congestion. The result of the ship maneuvering simulation demonstrates that the alternative routes by way of Buk-Sudo, Janbong-Sudo, north of Si-Do and Sin-Do is recommended routes which can satisfy the safety requirements of approaching to the canal entrance.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2641-2647
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• 2003

Conventional DLLs estimate the delay times of satellite signals individually and feed back these measurements to the VCO independently. But VDLL estimates delay times and user position directly and then estimate the feedback term for VCO using the estimated position changes. In this process, input measurements are treated as vectors and these vectors are used for navigation. First advantage of VDLL is that noise is reduced in all of the tracking channels making them less likely to enter the nonlinear region and fall below threshold. Second is that VDLL can operate successfully when the conventional independent parallel DLL approach fails completely. It means that VDLL receiver can get enough total signal power to track successfully to obtain accurate position estimates under the same conditions where the signal strength from each individual satellite is so low or week that none of the individual scalar DLL can remain in lock when operating independently. To operate VDLL successfully, it needs to know the initial user dynamics and position and prevents total system from the divergence. The suggested integration method is to use the inertial navigation system to provide initial dynamics for VDLL and to maintain total system stable. We designed the GPS/INS integrated navigation system. This new type of integrated system contained the vector pseudorange format generation block, VDLL signal processing block, position estimation block and the conversion block from position change to delay time feedback term aided by INS.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.5
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• pp.321-331
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• 2015

A study on the application of cooling defect detection was performed on the basis of a preceding study on the heated defect detection in nuclear piping loop system, using lock-in infrared thermography. A loop system with piping defects was made by varying the wall-thinning length, the circumference orientation angle, and the wall-thinning depth. The test was performed using an IR camera and a cooling device. Distance between the cooling device and the target loop system was fixed at 2 m. For analyzing experimental results, the temperature distribution data for cooling, and phase data were obtained. Through the analysis of this data, the defect length was measured. The reliability of the measurements for cooling defect conditions was shown to be higher in the lock-in infrared thermography data than the infrared thermography data.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.131-136
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• 2008

System을 통해 출력되는 신호를 측정할 때 정확한 측정을 방해하는 요소로 잡음이 있다. 이런 신호 측정의 방해 요소인 잡음을 제거 하는 방법 중의 하나로 Lock-in Amp(LIA)가 사용되고 있다. 본 논문에서는 잡음 신호의 제거를 위해 사용 하는 LIA를 제작 하고 특성을 파악 하였으며 RF통신을 이용하여 무선 형태로 제작 하였다. 현재 상용화된 LIA는 프로브를 통한 유선으로 측정신호의 입력을 받게 되지만 본 논문에서 제작된 LIA는 무선신호 형태로 입력 하게 된다. RF통신의 케리어 주파수는 447.9[MHz]로 Digital GMSK 변복조방식을 이용하였다. LIA의 제작은 Dual Phase Sensitive Detecter을 사용하였으며, 주요 구성 요소인 Phase Locked Loop, Phase Shifter, Phase Sensitive Detector, Low Pass Filter등의 구조와 특성을 조사하였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.1
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• pp.120-125
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• 1986

Data analysis methods in lock-in amplifier based DLTS systems were discussed with regards to the signal-to-noise ratio and improvement of resolution of DLTS spectrum. The DLTS system based on wideband two-phase lock-in amplifier is shown to be the most preferabe for the studies in deep levels of low concentration. A single-temperature scanning DLTS methods in lock-in amplifier based system with the improved sensitivity is proposed. The method is tested on the characterization of deep levels in n-GaAs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.188-189
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• 2006

The flux-lock type superconducting fault current limiter (SFCL) has the attractive characteristics that can adjust the current limiting level by the turns ratio and the winding direction of two coils. To apply this type SFCL into power system, the analysis for the recovery characteristics of it together with the current limiting characteristic is needed. In this paper, the experiments of the current limiting and the recovery characteristics of the flux-lock type SFCL with YBCO thin film were performed. The recovery characteristics of the flux-lock type SFCL dependent on the winding direction of two coils were analyzed through the comparison with the resistive type SFCL.