• Korean Journal of Optics and Photonics
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• v.22 no.3
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• pp.117-121
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• 2011

We propose a saturable absorber reflector based on guided-mode resonance. A carbon nanotube is used as a saturable absorber. By tuning the fill factor, modulation depth can be increased without a change of height of the CNT. We investigate the reflector properties such as modulation depth, bandwidth and peak reflectance as a function of the height of the CNT and the fill factor. The advantage of the proposed reflector is that it can reduce saturation energy by 50 times compared with CNT thin film of 100~200nm.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.481-494
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• 2001

An enhanced degenerated shell finite element (FE), which has been developed for inelastic analysis of reinforced concrete structures is described in this paper. Generally, Reissner-Mindlin (RM) assumptions are adopted to develop the degenerated shell FE so that transverse shear deformation effects is considered. However, it is found that there are serious defects such as locking phenomena in RM degenerated shell FE since the stiffness matrix has been overestimated in some situations. As remedies of locking phenomena, reduced integration, incompatible mode and assumed strain method have been used. Especially, the assumed strain method has been successfully used in many FEs. But contrarily, there is a few investigation on the performance of the assumed strains in the inelastic analysis of concrete structures. Therefore, shell formulation is provided in this paper with emphasis on the terms related to the stiffness matrix based on assumed strain method and microscopic concrete material model. Finally, the performance of the present shell element is tested and demonstrated with several numerical examples. From the numerical tests, the present result shows a good agreement with experimental data or other numerical results.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.2
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• pp.162-167
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• 1993

We have investigated analytically and numerically on both the generalized dimension D sub(n) and the fractal dimensionality f sub($\alpha$) in the dissipative Willbrink map. and discussed both the mode-locking phenomenon and the dissipative trajectory when z=0.03, b=0.9 and K sub(d) =0.272313668. In the mode-locking phenomenon. we find that the generalized dimension D sub(-n) and superconverged $\delta$ sub(n) are very close to D sub(-$\infty$) =0.92403 and $\delta$ sub($\infty$) =2.16442 even for n～20 as listed in Table 1. In dissipative trajectory, the values of D sub(+n) and D sub(-n) for n～20 are estimated to be very close to D sub(+$\infty$) =0.63267 and D sub(-$\infty$) =1.89802 on the circle map. Thus, the values of the generalized dimension as nlongrightarrow$\infty$ on dissipative Willbrink map are expected to be the same results as those for the circle map and to have the universal scaling exponents for a special scaling structure when the values of overbar(w), z, b, and k sub(d) have the different values.

• ETRI Journal
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• v.25 no.3
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• pp.149-155
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• 2003

A self-pulsating multisection distributed-feedback laser diode (DFB LD) can potentially realize all-optical clock extraction. This device generally consists of three sections, two DFB sections and one waveguide section. The most important variable in this device is detuning, which is the relative spectral position between the stop bands of two DFB sections. We fabricated a novel structure in which two gratings were located one over and one under the active layers. Each grating structure was independently defined in processing so that detuning, which is the prerequisite for self-pulsation, could be easily controlled. Observing various self-pulsating phenomena in these devices under several detuning conditions, we characterized the phenomena as dispersive Q-switching, mode beating, and self-mode-locking.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.63-68
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• 2000

A passively mode-locked ring type fiber laser had been installed in order to get the short pulses The single and the double mode-locking were appeared, and the shortest pulse length of 65 fs was obtained with a 110 m long dispersion shifted fiber(DSF) in a local cavity of 139.8 m. Also high order harmonic modelocking of 17th and Q-switched high order harmonic modelocking were obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.239-244
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• 1997

A hair-pin shaped microstrip-line resonator and a dielectric resonator for injection-locked oscillators have been designed and fabricated for the comparative studying of their characteristics. In general, a commonly used dielectric resonator shows lower phase noise value than hair-pin resonator in the free-running mode. In the injection-locked mode, however, a hair-pin resonator is superior to the dielectric resonator; the wider tuning range, the 22% improved locking bandwidth, the lower noise effect, the short term stability, and the higher power level. The planar structure of a hair-pin shaped microstrip-line resonator will be easily applied to monolithic microwave integrated circuits.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.4
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• pp.156-163
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• 1996

The brakes are the most important safety-critical accident avoidance components of a motor vehicle. They must perform safely under a variety of operating conditions and must have enough strength not to fail during the life of a vehicle. Recently, anti-lock brake systems are used on more and more passenger cars. The ABS brakes modulate brake line pressure to prevent brakes from locking during braking. In this study, finite element analysis, material test for FCD45, measurement of stress and cumulative fatigue damage analysis were performed to evaluate fatigue damage of the caliper housing under ABS mode.

• Journal of the Optical Society of Korea
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• v.2 no.1
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• pp.9-12
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• 1998

Rational harmonic mode-locking of an Er-doped fiber ring laser has been successfully demonstrated up to the 16-th harmonic, of the RF frequency applied to the electro-optic modulator. This is the highest harmonic reported so far to our knowledge.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.171-176
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• 1997

A hair-pin shaped microstrip-line resonator and dielectric resonator for injection-locked oscillators have been designed and fabricated for the comparative studying of their performances. In general, a commonly used dielectric resonator shows lower phase noise value than hair-pin resonator in the free-running mode. In the injection-locked mode, however, a hair-pin resonator is superior to the dielectric resonator, the wider tuning range, the 22% improved locking bandwidth, the lower noise effect, the short term stability, and the higher power level. The planar structure of a hair-pin shaped microstrip-line resonator will be easily applied to monolithic microwave integrated circuits.

• Current Optics and Photonics
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• v.5 no.3
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• pp.289-297
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• 2021

We describe a comb-mode resolving spectroscopic technique by direct time-domain phase correction of unstable interferograms obtained from loosely locked two femtosecond lasers. A low-cost continuous wave laser and conventional repetition rate stabilization method were exploited for locking carrier and envelope phase of interferograms, respectively. We intentionally set the servo control at low bandwidth, resulting in severe interferograms' fluctuation to demonstrate the capability of the proposed correction method. The envelope phase of each interferogram was estimated by a quadratic fit of carrier peaks to correct timing fluctuation of interferograms in the time domain. After envelope phase correction on individual interferograms, we successfully demonstrated 1 Hz linewidth of RF comb-mode over 200 GHz optical spectral-bandwidth with 10-times signal-to-noise ratio (SNR) enhancement compared to the spectrum without correction. Besides, the group delay difference between two femtosecond pulses is successfully estimated through a linear slope of phase information.