• The Journal of the Acoustical Society of Korea
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• v.21 no.2
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• pp.110-119
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• 2002

Acoustic characteristics of water sediment were experimentally studied in laboratory. Water saturated sand sediment less than the grain size of 0.5 mm diameter is uniformly distributed in an acryl box (100 mm×100mm×42mm) with material thickness 1 mm. Pores in the acryl box are modeled as the structure of cylindrical pore tubes (diameter 3 mm and length 42 mm) filled with water. Cylindrical pore tubes have porosities 0%, 5%, 11%, 18% and 26 % controlled by the tube numbers. Transmitted acoustic waves through sand sediment specimen are analyzed as the functions of porosity and frequency from 0.3 MHz to 4 MHz. Transmitted acoustic waves are mixed with the first-kind wave from whole specimen and the second-kind wane from cylindrical pore tubes. For the center frequency 1 MHz, the first kind wave is dominant but for the center frequency 2.25 MHz, the second kind wave is dominant. In the case of the first-kind wave, as the porosity increases, the transmission coefficient decreases and the sound speed decreases to the sound speed of water. As the frequency increases, the transmission coefficient decreases but the sound speed is almost constant. In the case of the second-kind wave, as the porosity increases, the transmission coefficient increases but the sound speed is almost constant. The transmission coefficient and the sound speed are almost constant as a function of frequency.

• Fashion & Textile Research Journal
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• v.7 no.6
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• pp.641-649
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• 2005

This study is to make pH 9 reduction by adding NaOH to 1, 3, 5, 7, 9, 11% solution of thioglycollic acid, cysteine, cysteamin, to add it on helically winded natural hair and colored hair and leave them for 20, 40, 60 minutes, to add $NaBrO_3$ oxidant for 15 minutes and to compare and analyze the wave form. This study showed the results of permanent using thioglycollic acid, cysteine, cysteamin. In the permanent wave form according to the kind of reductant, concentration, and processing time, there were a little difference between thioglycollic acid and cysteine. But cysteamine not only showed apparent difference but also formed strong and elastic wave. The permanent wave is affected by the diagonosis of hair, the choice of permanent solution and the processing time. Therefore the scientific diagonosis of hair is to be considered first of all. By choosing the kind of solution, the concentration and the processing time according to the results of hair diagonosis and wave form, we can prevent the lengthening and damage of hair.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10c
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• pp.111-116
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• 1998

Most previous wave tests for concrete have been done to evaluate static material properties, and thus there are less works to investigate dynamic material characteristics of concrete, which should be few in Korea. The objective of this experimental work is to investigate dynamic material characteristics of concrete, such as dynamic elastic modulus, dynamic shear modulus, first resonant frequency, dynamic poisson's ratio and etc. A dynamic Signal Analyzer has been used to perform the wave analysis for various dynamic material properties of test specimen. First Fourier transform technique has been carried out on various wave data acquired by the Resonant Column method, which is a kind of nondestructive tests. Wave analysis has been performed based on KS F2437, which is similar to ASTM C607-71 and is identical to JIS A 1127-1976.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.223-226
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• 2001

Acoustic pressure transmission coefficient and phase velocity are measured as the functions of water porosity and air porosity in sand sediment slabs with water- and air-filled pores. Pores in the sand sediment slab we modeled as the structure of circular cylindrical tube shape filled with water and air. The first kind(fast) wave and second kind (slow) wave, identified by Biot, in the solid and fluid mixed medium are affected by the presence of water and air pores. Acoustic characteristics of such porous medium in water are also theoretically investigated in terms of the modified Biot-Attenborough (MBA) model, which uses the separate treatment of viscosity effect and thermal effect in non-rigid porous medium with water- and air-filed pores. The information on the fast waves introduces new concepts of the generalized tortuosity factor and dynamic shape factor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.3960-3969
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• 1996

A fluid flow inside a circular cylinder subject to horizontal and circular oscillation is analyzed theoretically. Under the assumption of small-amplitude oscillation, the governing equations take linear forms. The velocity field is obtained in terms of the first kind of Bessel function of order 1. It was found that a particle describes an orbit close to a circle in the central region and an arc near the side wall. We also obtained the Stokes' drift velocity induced by the traveling wave along the circumferential direction. The Eulerian streaming velocities at the edge of the bottom and side boundary layers were also obtained. It was shown that the vertical component of the steady streaming velocity on the side wall is almost proportional to the amplitude of the free surface motion.

• Journal of Ocean Engineering and Technology
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• v.28 no.1
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• pp.12-19
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• 2014

Tsunamis are ocean waves generated by movements of the Earth's crust. Several geophysical events can lead to this kind of catastrophe: earthquakes, landslides, volcanic eruptions, and other mechanisms such as underwater explosions. Most of the damage associated with tsunamis are related to their run-up onto the shoreline. Therefore, effectively predicting the run-up process is an important aspect of any seismic sea wave mitigation effort. In this paper, a numerical simulation of the behaviors of a floating body near a quaywall during a tsunami is conducted by using a particle method. First, a solitary wave traveling over shallow water with a slope is numerically simulated, and the results are compared with experiments and other numerical results. Then, the behaviors of floating bodies with different drafts are investigated numerically.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.693-700
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• 2008

High-Pressure gas Pipeline which is buried in underground has the Possibility that will be exposed to unexpected dangerous impact of construction equipment. To protect from this kind of danger, the real-time health monitoring system of the high-pressure gas pipeline is necessary. First of all, to make the real-time health monitoring system clearly, the acoustic wave propagation characteristics which are made from various construction equipment impacts must be identified. In link of technical development that prevents the damage of high-pressure gas pipeline, this paper gives FEM(finite element method) and BEM(boundary element method) solutions to identify the acoustic wave propagation characteristic of the various impact input signals which consist of Direc delta function and convolution signal of 45 Hz square signal and random signal.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.22-32
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• 2001

The numerical investigation of obliquely incident wave interactions with fully submerged dual buoy/porous-membrane floating breakwaters placed in parallel with spacing is studied based on linear potential theory and Darcy's law. The numerical solutions are obtained by using a discrete-membrane dynamic model and second-kind modified Bessel function distribution over the entire boundaries of fluid regions. First, numerical solutions for an idealized dual submerged system without buoys are obtained. Second, a more practical dual submerged system with membrane tension provided by buoys at its tops is investigated by the multi-domain boundary element method particularly devised for dual buoy/porous-membrane problems with gaps. The velocity potentials of wave motion are coupled with porous-membrane deformation, and solved simultaneously since the boundary condition on porous-membrane is not known in advance. The effects of varying permeability on membranes and wave characteristics are discussed for the optimum design parameters of systems previously studied. The inclusion of permeability on membrane eliminates the resonances that aggravate the breakwater performance. The system is highly efficient when waves generated by the buoys and membranes were mutually canceled and its energy at resonance frequency dissipates through fine pores on membranes.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.454-466
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• 2016

The Korean wave refers to the spread of Korean popular culture from China to all over the world. The Korean wave has been improving the national image and creating a new brand value for Korea as a symbolic soft power. Its spread has been operating as a kind of energy that is fueling national competition. The Korean wave creates a new type of tour and increases tourists' intention to visit special places revealed indirectly through mass media. People can vary highly in terms of awareness, attitude and behavioral pattern according to the degree of care for and interest in something. This is called involvement. Three hypotheses were established to study the effect of the Korean wave in terms of involvement. First of all, it confirms whether the Korean wave involvement affects national image and image as a tourist destination. Second, it confirms whether national image affects Korea's image as a tourist destination. Third, it confirms whether the Korean wave involvement affects intention to visit Korea. The certification results of these hypotheses confirm that the Korean wave affects national image, Korea's image as a tourist destination, and intention to visit Korea. The national image also partly affects its image as a tourist destination.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.4
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• pp.87-94
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• 1985

Dynamic analysis of guyed tower is presented in this paper. The scope of the study is twofold. The one is to determine an efficient analysis method to include the nonlinearity of the mooring system and the nonlinear hydrodynamic wave forces. The other is to investigate the sensitivity of two major design parameters, that is the stiffness of mooring system and the fixity condition of the tower at mud line. Time history analysis method utilizing mode superposition is mainly considered. However several other methods are also used for the purpose of comparison. Analyses are carried out using the Lena Guyed Tower, which is the first structure of this kind, as a standard structure.