• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.4
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• pp.89-99
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• 2007

In this paper, an analytic model of a sleep mode operation in the IEEE 802.16e is investigated. A mobile subscriber station(MSS) goes to sleep mode after negotiations with the base station(BS) and wakes up periodically for a short interval to check whether there is downlink traffic to it. If the arrival of traffic is notified, an MSS returns to wake mode. Otherwise, it again enters increased sleep interval which is double as the previous one. In order to consider the situation more practically, we propose the sleep mode starting threshold, during which MSS should await packets before it enters the sleep mode. By modifying the M/G/l with multiple vacations model, energy consumption ratio(ECR) and average packet response time are calculated. Our analytic model provides potential guidance in determining the optimal parameters values such as sleep mode starting threshold, minimal sleep and maximal sleep window.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.55-61
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• 2021

The lateral-mode characteristics of 850-nm GaAs/(Al,Ga)As multiple-quantum-well laser diodes and their influence on the kinks in output optical power are investigated. For the investigation, self-consistent electro-thermal-optical simulation and measurement of fabricated devices are used. From this investigation, the optimal P-cladding thickness that provides single-lateral-mode operation is determined, so that high beam quality can be achieved even at high output powers.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2366-2371
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• 2007

Spray combustion characteristics of a conducting fuel electrospray have been studied for clean combustion technology. The multiplexing system which can retain the characteristics of the cone-jet mode is inevitable for the electrospray application. Charged micro droplets can be obtained in almost uniform size during operating the electrospray in the cone-jet mode. This experiment device set up the multiplexed grooved nozzle system with the extractor. Using the grooved nozzle, the stable cone-jet mode can be achieved at the each groove in the grooved mode. This electrospray system was applied to the diffusion combustion. It is the first step to discover the diffusion combustion characteristics of the electrospray. In case of the single grooved nozzle electrospray, the diffusion flames are occurred at each jet of grooved mode and they are quite stable. The exhaust gas analysis was indicated that there is the critical point which can make very stable diffusion combustion.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1225-1228
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• 2004

We have studied the Polymer Stabilized Continuous Director Rotation (PSCDR) mode to solve the thermal shock problem which is core and main problem in CDR mode. The cell filled 95wt. % R2301 FLC and 5wt. % UCL-001 polymer is applied a low DC voltage only near the phase transition temperature from cholesteric to chiral smectic C phase transition to get defect-free alignment. In the previous work, we also confirmed layer deformation induced by an applied DC field only near the phase transition temperature from Ch to $SmC^{\ast}$. Results of layer structure, and characteristics of electro-optical properties between CDR and PSCDR mode will be discussed in this paper. We are also in progress to finalize the layer structures compared between CDR and PSCDR mode by x-ray measurements.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.50-52
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• 2003

This paper presents characteristics analysis of brushless DC motor(BLDCM) which driven by two types of PWM mode. The phase current and torque ripples are generated differently at each PWM mode. So they have a different influence on motor characteristics. In this paper, we have analyzed characteristics of BLDCM using time-stepped voltage source finite element method. The effect of two types of PWM mode had been confirmed by comparing each phase current and torque ripple waveform. The compared simulation result is useful to select a better PWM mode.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.21-26
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• 2013

Delamination of cover concrete due to re-bar corrosion is a critical damage reducing structural safety of reinforced concrete structures. Therefore, it should be detected and evaluated to provide appropriate maintenance to recover structural integrity. Impact-echo method, which utilizes thickness vibration characteristics of delaminated concrete section, is effective for detection and evaluation of small areal size delamination. However, it may not be applicable for large areal size delamination in which flexural vibration modes are dominated. In this study, applicability of vibration mode shapes of delaminated concrete section is investigated for visualization of delamination region in concrete structures. Numerical and experimental modal tests are performed to estimate mode shapes of delaminated concrete section and linear absolute summation technique is proposed for effective visualization of delamination region based on estimated mode shapes.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.270-275
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• 2013

In this study, focusing of ultrasonic Lamb wave by negative refraction with mode conversion from antisymmetric to symmetric mode was investigated. When a wave propagates backward by negative refraction, the energy flux is antiparallel to the phase velocity. Backward propagation of Lamb wave is quite well known, but the behavior of backward Lamb wave at an interface has rarely been investigated. A pin-type transducer is used to detect Lamb wave propagating on a steel plate with a step change in thickness. Conversion from forward to backward propagating mode leads to negative refraction and thus wave focusing. By comparing the amplitudes of received Lamb waves at a specific frequency measured at different distance between transmitter and interface, the focusing of Lamb wave due to negative refraction was confirmed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.4
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• pp.188-193
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• 2003

This paper describes a novel burst-mode clock and data recovery (CDR) circuit which can be used for 622Mbps burst mode applications. The CDR circuit is basically a phase locked loop (PLL) having two phase detectors (PDs), one for the reference clock and the other for the NRZ data, whose operations are controlled by an external control signal. This CDR was fabricated in a 1-poly 5-metal $0.25{\;}\mu\textrm{m}$ CMOS technology. Jitter generation, burst/continuous mode data receptions were tested. Operational frequency range is 320Mhz~720Mhz and BER is less than 1e-12 for PRBS31 at 622Mhz. For the same data sequence, the extracted clock jitter is less than 8ps rms. Power consumption of 100mW was measured without I/O circuits.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.2
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• pp.94-97
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• 2007

The desin and implementation of a CMOS analog integrated circuit that provides dual-mode modulations, PWM for active clamp reset converter and PFM for LLC resonant converter, is described. The proposed controller is capable of implementing programmable soft start and current-mode control with compensating ramp for PWM and frequency shifting soft start for PFM. Also it provides delay time for both modes. PWM mode is implemented by active clamp reset converter and PFM mode is implemented by LLC resonant convereter, respectively. The chip is fabricated using the 0.6um high voltage CMOS process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10C
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• pp.778-786
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• 2008

The H.264/AVC video coding standard shows superior coding efficiency by adopting many new techniques. However, the encoding complexity increases greatly to achieve higher coding efficiency. Especially, the rate distortion optimization technique, which is used to decide the intra-prediction mode, increases the encoding complexity. In this paper, we propose an efficient intra-prediction mode decision method. By using the variance of pixel values and the edge direction, the computational complexity of the intra-prediction mode decision is greatly reduced.