• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.153-160
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• 2010

We optimized the Si(substrate)/$SiO_2$(cladding)/$Si_3N_4$(antiresonant cladding)/$SiO_2$(core)/air multi-layers rib-optical waveguides of antiresonant reflecting optical waveguide (ARROW) for integrated optical biosensor structure utilizing beam propagation method (BPM). Thickness of anti-resonant cladding was derived to minimize the propagation loss and leaky field mode deeply related with evanescent mode was theoretically derived. Depth, width, refractive index and cladding thickness of anti-resonant cladding were numerically calculated into 2.3${\mu}m$, 5${\mu}m$, 1.488, and 0.11${\mu}m$ respectively to minimize propagation loss using the BPM simulation tool. Finally one- and two-dimensional propagation characteristics of ARROW was confirmed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.193-197
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• 2015

Recently, the new issues for the safety and the information delivery system in the ship are raised. The deployment and the efficient algorithms of deploying the wireless sensor networks instead of using the built-in wired networks or the setup of the new wired networks is more desirable than the deployment of the wired networks in a ship after its final production since it can reduce the cost and the time of the brand new wired networks by reshaping some of the internal structure of the ship. In this paper, the shipboard signal propagation measurement system based on the signature sequence-three way slave mode are designed and its measureed data are analysed after measuring the signal propagation characteristics. Consequently, it is expected that the reliable and cost-effective signal measurement system with the three way algorithm for the deployment of the shipboard wireless networks can be achieved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.183-186
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• 2015

Recently, the demand for the safety and the information delivery system in the ship increases. The deployment of the wireless sensor networks instead of using the built-in wired networks or the setup of the new wired networks is more desirable than the deployment of the wired networks in a ship after its final production since it can reduce the cost and the time of the brand new wired networks by deforming some of the internal structure of the ship. In this paper, the shipboard signal propagation measurement system based on the signature sequence-two way slave mode are designed and its measurement data are analysed after measuring the signal propagation characteristics. Consequently, it is expected that the reliable and cost-effective signal measurement system for the deployment of the shipboard wireless networks can be built.

• Korean Journal of Optics and Photonics
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• v.30 no.1
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• pp.15-22
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• 2019

$Si_3N_4$ rib-optical waveguides for evanescent-wave integrated-optical biosensors were analytically interpreted, to derive the single-mode propagation conditions. The integrated-optical biosensor structure based on two-mode interference was proposed, and the rib width and thickness and core thickness for a single-mode and two-mode waveguide (sensing region) were proposed to be $3{\mu}m$, 2 nm, and 150 nm and $3{\mu}m$, 20 nm, and 340 nm respectively. The optical characteristics of each guided-wave mode were investigated utilizing the film mode-matching (FMM) analysis.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.189-197
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• 1999

To investigate internal waves (IW) effect on acoustic wave propagation, m analysis is conducted on mode travel time and model simulation. Based on the thermistor string data, it can be shown that the thermocline depth variation may cause travel time difference as much as 4-10 ms between mode 1 and 2 over range 10 km. This travel time difference causes interference among modes and thus fluctuation from range-independent stratified ocean structure. In real situations, however, there exist additionally spatial variation of IW. Model simulation with all modes and simple IW shows clear responses of acoustic signals to IW, amplitude and phase fluctuation.

• Journal of Power System Engineering
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• v.13 no.1
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• pp.39-45
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• 2009

The attenuation of the fundamental non-torsional modes that propagate down buried steel water pipes has been studied. The mode shapes, mode attenuation due to leakage into the surrounding medium and the scattering of the modes as they interact with pipe joints and fittings have been investigated. In the low frequency region the mode predicted to dominate over significant propagation distances approximates a plane wave in the water within pipe. The established acoustic technique used to locate leaks in buried steel water pipes assumes that leak noise propagates as a single non-dispersive mode at a velocity related to the low frequency asymptote of this water borne mode.

• Korean Journal of Optics and Photonics
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• v.6 no.2
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• pp.148-155
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• 1995

The low loss single-mode $Al_{0.042}Ga_{0.958}As/GaAs/Al_{0.042}Ga_{0.958}As$ strip-loaded waveguides had been designed using an effective index method and fabricated using a MOCVD technique and chemical wet etching method. The propagation loss and facet reflectivity were measured by the Fabry-Perot resonance method and sequential cleaving experiment at $1.31{\mu}m$ wavelength. As a result, the propagation loss is as low as 0.62 dB/cm and the facet refiectivity(R) equals to 0.299 for straight waveguides with width $ w=4.1{\mu}m$..

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.1
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• pp.133-140
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• 2001

Recently, to assure the integrity of a structural components such as piping pressure vessels and thinning structure, Lamb wave inspection technique has been used in material evaluation. It is very important to select the optimal Lamb wave mode and to analyze the signal accurately because of its unique dispersion properties grnerating several modes within the speci-men. It this study, the feasibility of material evaluation applications using wavelet analysis of Lamb wave has been veir-fied experimentally. These results show as follows; 1)dispersion characteristic of each mode in dispersion curve is demon-strated that A0 mode propagating material surface is useful mode having the lest energy loss and not sensitive to surface condition. 2) it can be detected even the micro defect ($1\times2mm$) fabricated in ultrasonic probe flaw distance (290mm) to axis direction. 3) the wavelet transform which is called "time-frequency analysis" shows the Lamb wave propagation due to the change of materials characterization can be evaluated at each frequency and experimental group velocity of Lamb wave agrees quite well with that of simulated dispersion curve.ion curve.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1455-1458
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• 2007

Vibration characteristics of concrete slabs were investigated using a 1:10 scale model and finite element method. A 1:10 scale model of a test building with 150 and 200mm slab thicknesses was made of acrylic materials. Modal test was conducted to investigate mode shape and modal frequencies. Results show that the mode shapes of two slabs with different thickness are similar each other, whereas natural frequency is different. Through modal analysis using FEM, it was revealed that both mode shapes and natural frequencies calculated from the FEM model are similar to those of the scale model measurement. It was also found that natural frequencies increased with increment of the slab thickness.

• The Journal of the Acoustical Society of Korea
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• v.13 no.1E
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• pp.45-54
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• 1994

Characteristics of a piezoelectric material are evaluated to pick up the optimal crystal cut and propagation direction for a SAW device. For the piezoelectric single crystal $LiTaO_4$, such items are investigated as the Rayleigh wave velocity, the electromechanical coupling factor, the surface permittivity, the frequency-temperature coefficient, the air loading attenuation, the pure mode propagation, the beam steering and the misalignment sensitivity. Theoretical calculations reveal that Y-cut and Z-propagation is the optimal SAW propagation path. The results are confirmed through experiments. The method empolyed in this paper is applicable to other crystals, too, either single or poly crystals.