• Korean Journal of Optics and Photonics
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• v.19 no.3
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• pp.169-174
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• 2008

In this paper, we have presented techniques to reduce the splicing loss between standard single mode fiber and high ${\Delta}$ single mode fiber based on the mode expanding and mode evolution induced by thermal treatment of the fibers. The experimental results show that mechanical splicing loss can be reduced from 2.3 dB to 0.1 dB through proper thermal treatment of the high ${\Delta}$ fiber. Meanwhile, we achieved $0.2{\sim}0.4dB$ of low splicing loss between two fibers by heating the splicing region using electric arcing or an oxygen flame.

• Geomechanics and Engineering
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• v.28 no.1
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• pp.77-87
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• 2022

Many geotechnical analyses require the investigation of water flow within partially saturated soil zone to incorporate the effect of climatic conditions. It is widely understood that the hydraulic properties of the partially saturated soil should be included in the transient seepage analyses. However, the characteristics of dual porosity soils with dual-mode water retention curve are normally modelled using single-mode mathematical equation for simplification of the analysis. In reality, the rainwater flow can be affected significantly by the dual-mode hydraulic properties of the soil. This paper presents the variations of safety factor for dual porosity soil slope with dual-mode water retention curve and dual-mode unsaturated permeability. This paper includes the development of the new dual-mode unsaturated permeability to represent the characteristics of soil with the dual-mode water retention curve. The finite element analyses were conducted to examine the role of dual-mode water retention curve and dual-mode unsaturated permeability on the variations of safety factor under rainfall loading. The results indicate that the safety factor variations of dual porosity soil slope modelled using the dual-mode water retention curve and the unsaturated permeability equation are lower than those of dual porosity slope modelled using single-mode water retention curve and unsaturated permeability equations.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.620-622
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• 2009

We demonstrated a liquid crystal display (LCD) mode with a single polarizer based on the array of a switchable microlens consisting of a circular stop mask and its complementary open mask. The focused beam passed through the open mask and thus the bright state was obtained, while the defocused beam was blocked by the stop mask and the complementary open mask. It is expected that our single-polarizer LCD mode is applicable to low cost displays.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.343-349
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• 2020

This study proposes a new single inductor converter for DC grid systems. A conventional system is composed of two independent converters for controlling battery and load. This system is simple but it has two inductors that affect power density and efficiency. The proposed converter can reduce the number of inductors by integrating the two converters and relieve voltage stress on switches by using a battery switching cell. Accordingly, power density and efficiency can be improved using a single inductor and lower voltage-rated switches. A prototype of a 500 W converter is built, and each mode is experimented on to confirm the validity of the proposed converter.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.6
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• pp.260-264
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• 2002

We developed LD Pumped Nd:$VVO_4$ microchip laser with the cavity length of 1mm. The microchip laser output was 87.5㎽ at the wavelength of 1063.9nm with the input power of 241㎽ at the wavelength of 809nm. The slope efficiency was 40.7% and the threshold input power was 31.1㎽. We have also defined input power limit for the single longitudinal mode operation theoretically. It was 2.5 times larger than that of threshold input intensity. According to the results of simulation, the Nd:YVO$_4$ microchip laser can be operated with the maximum output of 15㎽ for the single longitudinal mode up to the input power of 77.75㎽.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.105-113
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• 2014

The mode II fracture behavior of a single-layer graphene sheet (SLGS) containing a center crack was characterized with the results of an atomistic simulation and an analytical model. The fracture of zigzag graphene models was analyzed with molecular dynamics and the mode II fracture toughness was found to be $2.04MPa{\sqrt{m}}$. The in-plane shear fracture of a cellular material was analyzed theoretically for deriving the $K_{IIc}$ of SLGS, and FEM results were obtained. Mixed-mode fracture of SLGS was studied for various mode I and mode II ratios. The mixed-mode fracture criterion was determined, and the obtained fracture envelope was in good agreement with that of another study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.310-313
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• 2005

This paper is concerned with the active vibration control of beam equipped with piezoceramic sensors and actuators. The single-input and single-output positive position feedback controller is considered as an active vibration controller for the beam. The proposed single-input and single-output positive position feedback controller can cope with many modes of interest by summing each positive position feedback controller designed for each mode. In this paper, theoretical formulation is first explained in detail. We discuss how to design the single-input and single-output positive position feedback controller for a target structure by considering Euler-Bemoulli beam. It is found that the theories developed in this study are capable of predicting the control system characteristics and its performance.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.48-53
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• 1997

Volume hologram was recorded using reference beam form optical fiber taper. A singel mode fiber was chemically etced to make a taper structure, and we showed experimentally that the referencing by the irregular beam pattern from this taper structure could increase the storage density of photorefractive volume hologram. The spatial selectivity of the volume hologram with this method was increased by two times compared to the normal single mode fiber referencing case. A theoretical analysis with randomly phased plane model also confirmed the results.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.35-36
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• 2007

We report a probe using a single double clad fiber (DCF) for fluorescence spectroscopy. Bidirectional separate transmission for excitation and fluorescence light in a single fiber was implemented. A DCF coupler made by side-polished method could extract none but the collected fluorescence signals propagating in inner cladding mode, thereby diminishing the interference of silica background generated by the excitation in core mode. The experimental results show that the fluorescence spectra of biological tissues obtained using the DCF probes have much less silica background than using a standard multiple-mode fiber.

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.139-140
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• 2008

We demonstrate a novel acousto-optic filter using a two-mode photonic crystal fiber. Thanks to endless two-mode operation of the fiber, single notch over a whole spectrum is obtained with tuning range of> 1000 nm.