• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.159-165
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• 2005

The proposed optical transmitter is composed of FF(flip flop) , PLL (phase locked loop), reference clock generator, serializer and LD driver 10x250 Mb/s data arrays are translated to the 2.5 Gb/s data signal by serializer. In this case, 1 data bus is allocated usually as a reference clock for synchronization. In this proposed optical transmitter, 125 MHz reference clock is generated from 10x250 Mb/s data arrays by reference clock generator. From this method. absent of reference clock bus is available and more data transmission become possible. To achieve high speed operation, the serializer circuit is designed as two stacks. For 10:1 serialization, 10 clocks that have 1/10 lambda differences is essential, so the VCO (voltage controlled oscillator) composed of 10 delay buffers is designed. PLL is for runing at 250 MHz, and dual PFD(phase frequency detector) is adopted for fast locking time. The optical transmitter is designed by using 0.35 um CMOS technology.

• Archives of design research
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• v.17 no.1
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• pp.179-190
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• 2004

The human effort to make personal privacy and safety from outer environment has brought the improvement of security system through the technological development. Especially as a apartment dwelling and lifestyle is general, the role and function of door lock system is more important than ever. The research for user-centered approach and design on the door lock system should be implemented under the circumstances. This study has focused on the development of making safety as well as easy interface to design door lock system. The price also is competitive as compared with other door lock products. The goal of this study is to propose the alternatives not only to develop door lock design but also to search the innovative way of locking system design.

• Nuclear Engineering and Technology
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• v.50 no.6
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• pp.971-980
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• 2018

Using the concept of quasi-static decomposition and using three-noded isoparametric locking-free element, this article presents a formulation of the finite element method for Timoshenko beam subjected to spatially different time-dependent motions at supports. To verify the validity of the formulation, three fixed-hinged beams excited by the real seismic motions are examined; one is a slender beam, another is a stocky one, and the other is an intermediate one. The numerical results of time histories of motions of the three beams are compared with corresponding analytical solutions. The internal loads such as bending moment and shearing force at a specific time are also compared with analytic solutions. These comparisons show good agreements. The comparisons between static components of the internal loads and the corresponding total internal loads show that the static components predominate in the stocky beam, whereas the dynamic components predominate in the slender one. Thus, the total internal loads of the stocky beam, which is governed by static components, can be predicted simply by static analysis. Careful numerical experiments indicate that the fundamental frequency of a beam can be used as a parameter identifying such a stocky beam.

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.103-108
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• 2013

The operation of a Doppler wind LIDAR in a mobile environment is very sensitive to shocks and vibrations, which can cause critical failures such as misalignment of the optical path and damage to optical components. To be able to stabilize the LIDAR and to perform wind field measurements in motion, a shock absorption and vibration isolation system was designed and implemented. The performance of the vehicle-mounted Doppler wind LIDAR was tested in motion, first in a circular test route with a diameter of about 30 m and later in regular expressway traffic. The vibration isolation efficiency of the system was found to be higher than 82% in the main vibration area and shock dynamic deflection was smaller than maximal deflection of the isolator. The stability of the laser locking frequency in the same mobile environment before and after the vibration isolation system installation was also found to be greatly improved. The reliability of the vibration isolation system was confirmed by good results of the analysis of the LIDAR data, in particular the plane position indicator of the line of sight velocity and the wind profile.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.2
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• pp.329-337
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• 1999

In this dissertation, the characteristics of W-CDMA(Wideband CDMA) are studied and required specifications of IMT-2000 transceiver using W-CDMA method are proposed. Also, in order to design the RF circuits satisfied the proposed specifications, theoretical models are expanded and real circuits are made. Then the RF circuits of the mobile stations are implemented in the three parts, transmitter, receiver and frequency synthesizer and are evaluated. The frequency synthesizer is designed using techniques of swallow counter and passive 3rd loop filter. For improving characteristics of the loop, a LPF was added to the 2nd loop filter. So although the locking times are loosed, the spurious are reduced. The output power of transmitter is over 50mW, the spurious output is -40dB/30kHz at 5MHz offset and power control range is -20dB at 2.5V. The proposed specifications are considered in highly practical environment and the theoretical designs and the experiments are expressed as simply as possible in order to facilitate understanding. It stands to reason that the results of this study can be used to design the wider CDMA(25MHz Bandwidth) mobile communication systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.811-818
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• 2016

A continuous fine-tuning phase locked loop with an additional negative feedback loop has been proposed. When the phase locked loop is out-of-lock, the phase locked loop has a fast locking characteristic using the continuous band-selection loop. When the phase locked loop is near in-lock, the bandwidth is narrowed with the fine loop. The additional negative feedback loop consists of a voltage controlled oscillator, a frequency voltage converter and its internal loop filter. It serves a negative feedback function to the main phase locked loop, and improves the phase noise characteristics and the stability of the proposed phase locked loop. The additional negative feedback loop makes the continuous fine-tuning loop work stably without any voltage fluctuation in the loop filter. Measurement results of the fabricated phase locked loop in $0.18{\mu}m$ CMOS process show that the phase noise is -109.6dBc/Hz at 2MHz offset from 742.8MHz carrier frequency.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.1
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• pp.43-57
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• 2005

Temporomandibular disorders have been defined as a collective term embracing a number of clinical problems that involve the temporomandibular joint, the masticatory nuscles, and associated structures. There have been many different contributing factors of TMDs which were traumatic, occlusal, pathophysiological and psychosocial. Among there factors, the effect of occlusion on TMDs have been a controversy for a long time. The purpose of this study was to investigate the effect of occlusal factors and oral habits on TMDs. In this study, 140 subjects with signs and symptoms of TMDs and diagnosed of TMD in the Orofacial Pain clinic of Yonsei University Dental Hospital though March to July 2004 were selected for the TMDs group and 50 subjects without any signs and symptoms of TMDs as the control group. The subjects were evaluated clinically in TMDs' Occlusal and Prosthodontic Restoration examinations. TMDs' examination was composed of the TMJ pain, sound, locking, temporal or masseter muscle palpation, mandibular movement, oral habits and headache. Occlusal examination was made of overjet, overbite, lost teeth number, nonfunctional interference, midline shift, then pattern of lateral movement and attrition. prosthodontic restoration examination had the existence of restoration, placement, then number of crown or bridge and Satisfiable index which estimated the quality of occlusal state of prosthodontic restorations. Following results were obtained : 1. The prevalence of TMDs was higher in their 20s & 30s, female of the TMD patients group. 2. The clenching frequency in the TMDs group(40.71%) was higher than those in the control group(18.00%), and there was a significant statistical difference(p<0.05). 3. The frequency of Nonfunctional interference in the TMDs group(10.00%) was higher than those in then Control group(2.00%), and there was a significant statistical difference(p<0.05). The result of this study indicated TMDs prevalence was higher in their 20s, 30s, female group of TMDs patients similar to the previous studies. Clenching and nonfunctional interference were estimated as the contributing factors of TMDs.

• Korean Journal of Cognitive Science
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• v.20 no.2
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• pp.155-181
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• 2009

Psychophysiologists are often interested in the EEG signals that accompany certain psychological events. When one is interested in a time series of event-related changes in EEG, one focuses on examining how the waveforms recorded at individual electrode sites vary over time across one or more experimental conditions. This is an analysis of event-related potentials (ERPs). In addition to such a classical EEG analysis in the time domain, the EEG measures can be investigated in the frequency domain. Moreover, it has been demonstrated that spectral analyses can often yield significant insight into the functional cognitive correlations of the signals. Therefore, this review paper tries to summarize essential concepts (e.g. phase-locking) and conventional methods (e.g. wavelet transformation) for understanding spectral analyses of brain oscillatory activity. Phase-coherence is also introduced in relation to functional connectivity of the brain.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.695-699
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• 2015

A high spectral resolution lidar (HSRL) system based on injection-seeded Nd:YAG laser and iodine absorption filter has been developed for the quantitative measurement of aerosol and cloud. The laser frequency is stabilized at 80 MHz by a frequency locking system and the absorption line of iodine cell is selected at the 1111 line with 2 GHz width. The observations show that the HSRL can provide vertical profiles of particle extinction coefficient, backscattering coefficient and lidar ratio for cloud and aerosol up to 12 km altitude, simultaneously. For the measured cases, the lidar ratios are 10~20 sr for cloud, 28~37 sr for dust, and 58~70 sr for urban pollution aerosol. It reveals the potential of HSRL to distinguish the type of aerosol and cloud. Time series measurements are given and demonstrate that the HSRL has ability to continuously observe the aerosol and cloud for day and night.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.12
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• pp.65-72
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• 2008

This paper proposes a new dual-loop digital PLL(DPLL) using seamless frequency tracking methods. The dual-loop construction, which is composed of the coarse and fine loop for fast locking time and a switching noise suppression, is used successive approximation register technique and TDC. The proposed DPLL in order to compensate the quality of jitter which follows long-term of input frequency is newly added cord conversion frequency tracking method. Also, this DPLL has VCO circuitry consisting of digitally controlled V-I converter and current-control oscillator (CCO) for robust jitter characteristics and wide lock range. The chip is fabricated with Dongbu HiTek $0.18-{\mu}m$ CMOS technology. Its operation range has the wide operation range of 0.4-2GHz and the area of $0.18mm^2$. It shows the peak-to-peak period jitter of 2 psec under no power noise and the power dissipation of 18mW at 2GHz through HSPICE simulation.