• 대한화학회지
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• 제43권2호
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• pp.156-160
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• 1999

메탄-산소를 아르곤으로 희석한 혼합기체의 점화 과정을 1516-1937K 온도 범위에서 반사 충격파를 이용하여 고찰하였다. 메탄 기체의 점화 지연 시간은 충격관 끝에서 5.0 cm 떨어진 곳에서의 압력 변화 및 광 방출을 측정하여 구하였으며, 각 혼합기체의 농도 의존도 및 온도 의존도에 관한 실험식을 구할 수 있었다. 메탄 산화 과정에 관한 실험 결과를 설명하기 위해 GRI 1.2 메카니즘을 이용한 컴퓨터 모의 실험을 수행하였다.

• 소음진동
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• 제4권3호
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• pp.295-305
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• 1994

The reflection coefficient of a material at oblique incidence is measured in a free field. The sound pressure distributions are measured at discrete points on two measurement lines and then decomposed into plane wave components by using spatial Fourier transform. The inciedent and reflected plane wave components are obtained from a set of "decomposition equations" of which uses the plane wave propagation theory. Numerical simulations and experiments have been performed to see the effect of finite size of measurement area. To reduce this effect, a window fuction has been performed to see the effects of finite size of mesurement area. To reduce this effect, a window function has been proposed and its effect on the measurement of sound absorbing material property has been studied as well. The reflection coefficient obtained by this method is compared with those obtained from other methods; 2-microphone method in a duct and an expirical equation of which determines the characteristic impedance .rho.c and propagation constant k of a material from flow resistance information.formation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.969-974
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• 2007

In this paper, a beamforming technique is introduced to measure the acoustic impedance at both normal and oblique incidence in a free field. The acoustic impedance is obtained by separating incident and reflected signals using the adaptive nulling method which is one of the various beamforming algorithms. To obtain better results, pressure vector commonly used in array signal processing is replaced with the transfer function vector between each microphone and the white Gaussian noise is suppressed by a wavelet shrinkage technique. The experiments conducted in a semi-anechoic room show that the proposed method is efficient and accurate in measuring the acoustic impedance of sound absorbing materials under a free field condition.

• 한국연소학회지
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• 제4권1호
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• pp.59-65
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• 1999

Ignition of $NH_3-O_2-Ar$ mixtures have been studied behind reflected shock waves over the temperature range of 1600-2300 K and the pressures in the range of 1.1-1.6 atm. The pressure profile and the radiation emitted behind the shock waves have been monitored to give empirical correlations between ignition delay times and the mixture concentrations with the experimental conditions. On the basis of this data, several kinetic mechanisms proposed for ammonia oxidation at high temperatures have been tested. The ignition delay times obtained from the mechanism proposed by Miller and Smook were in good agreement with our experimental results.

• 한국해양공학회지
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• 제1권1호
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• pp.138-143
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• 1987

Friction welding has emerged as a reliable process for high-production commercial applications with significant economic and technical advantages. But nondestructive test in friction weld was not clearly developed. Therefore the experimental verification is necessary in order to understand the characteristcs of the pulse echo effects according to various change in welding conditions. This paper presents an attempt to determine the relationship between the varios welding conditions and the coefficients of reflection using the ultrasonic pulse echo method in dissibilar metals friction weld. The new approach of calculating the coefficients of reflection based on measured amplitudes of the echoes is applied in this paper. These coefficients provides a single quantitative measurement which involves both acoustic energy reflected at the welded interface as well as transmitted across the interface. As a result, it was known that the quantitave relationship between welding conditions and the coefficients of reflection using the ultrasonic pulse echo exists in dissimilar metals friction weld.

• 한국농촌건축학회논문집
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• 제15권4호
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• pp.79-86
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• 2013

Demand of new suburban residential development and a variety of new types for housing have intensified by urban Citizens overused of poor urban residential environment. Income growth and improvement of living standards for the quality of the living environment are increasing demands of creating a more comfortable living environment. Thus, according to changes in social conditions, the development of urban area while accommodating additional development pressure adequately, particularly residential development in order to promote the efficient development of suburban areas are planned for the rational development direction. This study suggests the following improvement measures by analyzing the characteristics of the Suburban Housing Complexes built recently. In order to create a more pleasant Suburban Housing Complexes First, the accessibility of the traffic conditions, education and public facilities is good Second, the construction plans reflected needs of the consumers should be made Third, necessary facilities for activation of the urban-rural exchanges must be equipped.

• Structural Engineering and Mechanics
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• 제26권2호
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• pp.179-190
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• 2007

Damage detection based on measured vibration data has received intensive studies recently. Frequently, the damage to a structure may be reflected by a change of some system parameters, such as a degradation of the stiffness. In this paper, we apply a method to nondestructively locate and estimate the severity of damage in corrosion pipeline for which a few natural frequencies or mode shapes are available. The method is based on the strain modal sensitivity ratio (SMSR) and the orthogonality conditions sensitivities (OCS) applied to vibration features identified during the monitoring of the pipeline. The advantage of these methods is that it only requires measuring few modal parameters. The SMSR-based and OCS-based damage detection methods are illustrated using computer-simulated and laboratory testing data. The results show that the current method provides a precise indication of both the location and the extent of corrosion pipeline.

• 한국군사과학기술학회지
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• 제13권2호
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• pp.211-217
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• 2010

This paper introduces the Hull Mounted Sonar Vertical Scanning(HMS Verscan) technique to overcome the limitation of target detection in short range shadow zone. Numerical experiments were done with the HMS Verscan taking advantage of the vertical beamforming technique for two-dimension hydrospace(range-depth). For numerical experiments, ray model and high-frequency monostatic reverberation model were used. HMS Verscan increased a sound pressure level at the short range shadow zone through reflections at the sea surface and seafloor. Inclusion of the boundary scattering improved target detection due to the sound reflected into the shadow zone.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.131-134
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• 2004

In this paper, a representative unit volume (RUV) model was employed to simulate thermoforming process of carbon fabric-polymeric foam sandwich structures. Thermoforming simulations, which capture crimp angles and amplitude changes of carbon fabric with respect to different types of foams under the operating pressure were conducted with the help of RUV model. Changed shapes of tow structure after thermoforming were reflected in the two dimensional to determine mechanical properties of skin parts, i.e_ carbon fabric composites after thermoforming. Bending simulations with respect to different foam systems as well as different moduli of carbon fabric composites were successfully carried out by using properties obtained from two-dimensional analyses.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.31-36
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• 2003

In this study a relationship between SP curves and tensile properties was investigated by FE analysis on SP test with various assumed tensile properties. For the accuracy of FE analysis, SP test and tensile test were performed and those results were compared with FE analysis results. The yield load(Py) defined from the intersection point of two lines tangent to the elastic bending region and plastic bending region. And it was related specifically with yield stress(${\sigma}_0$) in FE analysis result curves. The slopes of FE analysis result curves normalized by yield stress(${\sigma}_0$) reflected the change of tensile properties regardless of yield stress(${\sigma}_0$) variation. Empirical relations were derived from these results. Tensile properties from these relations showed good agreement in FE analysis curve and tested curve.