• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.291-302
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• 2005

Due to the importance of the parameter in structural response, the uncertain elastic modulus was located at the center of stochastic analysis, where the response variability caused by the uncertain system parameters is pursued. However when we analyze the so-called stochastic systems, as many parameters as possible must be included in the analysis if we want to obtain the response variability that can reach a true one, even in an approximate sense. In this paper, a formulation to determine the statistical behavior of in-plane structures due to multiple uncertain material parameters, i.e., elastic modulus and Poisson's ratio, is suggested. To this end, the polynomial expansion on the coefficients of constitutive matrix is employed. In constructing the modified auto-and cross-correlation functions, use is made of the general equation for n-th moment. For the computational purpose, the infinite series of stochastic sub-stiffness matrices is truncated preserving required accuracy. To demons4rate the validity of the proposed formulation, an exemplary example is analyzed and the results are compared with those obtained by means of classical Monte Carlo simulation, which is based on the local averaging scheme.

• Journal of the Korean Geographical Society
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• v.28 no.4
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• pp.356-378
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• 1993

This study examines the competitiveness of urban industrial structure and its changing characteristics. Cluster analysis of Arizona towns based on economic functions revealed the changing characteristics of urban functions over time. The relationship between the changes of urban functions and industrial competitiveness was confirmed through shift-share analysis. The level of industrial specialization has become more closely related to urban size in terms of both population and employment, but the relationship between metropolitan location and specialization level is not clear. Also, it is validated that the economies of Arizona towns have become more diversified and, consequently, have tended to converge toward the state average in industrial structure over time.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.205-215
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• 2007

In this study, the soil characteristics are analyzed using the result of various soil tests as an object of the soil layer of natural slopes in landslides areas. Also, the relationship with landslides and interrelation with each soil properties are analyzed. The landslides in three areas with different geological condition are occurred due to heavy rainfall in same time. The geology of Jangheung area, Sangju area and Pohang area is gneiss, granite, and the tertiary sedimentary rock, respectively. However soil characteristics have a little differentiation to geological condition, the soils sampled from landslide area have higher proportion of fine particle and porosity, and lower density than those from non landslide area. In case of same geological condition, landslides are occurred in the terrain slope with high permeability. The permeability is mainly influenced by the soil characteristics such as particle size distribution, porosity, particle structure, and the geological origins such as weathering, sedimentary environment. The soil layer with high internal friction angle is more stable than that with low internal friction angle in all geological condition. The permeability is mainly influenced by effective particle size, coefficient of uniformity, coefficient of gradation, porosity, density and so on. Also, those have interrelation with each factor. These interrelations are similar in all study area. Meanwhile, in proportion as the void ratio and the porosity rises the permeability increases.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.1-8
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• 2016

Non-destructive ultrasonic testing was applied to evaluate the performance of wood deck material with hole as artificial defect. Ultrasonic velocities and modulus of elasticity were measured according to different diameters and numbers of holes, and comparative analysis to each data were done. From the results, ultrasonic velocities and modulus of elasticity decreased with an increase in the hole size and showed a negative linear correlation with the size of hole, respectively. As the hole size increased, ultrasonic velocities decreased, but their difference was small in the case of the hole size under 15 mm. Also, ultrasonic velocities and modulus of elasticity decreased with increasing the number of holes and showed a strong negative linear correlation to the number of holes. As the number of holes increased, ultrasonic velocities decreased to 3.5%, but modulus of elasticity decreased to 27%. Therefore, the number of holes showed greater influence to modulus of elasticity than ultrasonic velocity. Overall, the size and number of holes influenced to ultrasonic velocity and modulus of elasticity, and their influence will be greater as the size and number of holes increases. These results suggested that several ultrasonic parameters rather than a single ultrasonic velocity should be applied to detect small defects in wood decking materials.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.141-143
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• 2006

It is well known that there are three mechanisms in the nozzle surface regression, namely ablation, mechanical erosion and chemical corrosion. There are Analogies among these three mechanisms. In order to compare the order of the magnitude of these mechanism, the analogy was adapted and the Mach number of the gas flow was expressed by the nozzle shape(location).

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.425-430
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• 2013

본 연구에서 전산유체해석 프로그램인 EDISON_CFD를 이용하여 차세대 항공기 날개 형상으로 각광받고 있는 초음속 비행조건을 갖는 Busemann 형식의 복엽기 형상에 대한 공력특성을 연구하였다. 날개는 압축성 조건에서 2차원 에어포일로 간략화 하여 모델링하였으며, 마하수에 따라 발생하는 충격파와 팽창파의 상호작용을 통한 소닉붐의 감소 형태를 분석해 보고, 마하수에 따른 항력계수를 얻어내었으며, 익형과 항력계수, 소닉붐의 상관관계를 분석하여 초음속항공기에서 복엽기 형상이 가지는 장단점에 대하여 연구하였다.

• Journal of Korean Society of Transportation
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• v.33 no.4
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• pp.405-416
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• 2015

This paper developed a method analyze drivers' response characteristics using spectral analysis with car following data. Cross-correlation function and cross spectrum are produced by Fourier transform from speed fluctuations of leading vehicle and following vehicle during the designated time ${\tau}$. Based on the analysis data, a process to calculate the reaction time and stimulus-adaption index of following vehicle was developed and 170 cases of field data was applied. It was reported average of 0.654 and 2.091 seconds of stimulus-adaption index and reaction time respectively. In conclusion, the developed indexes might contribute to enhance vehicle control of autonomous vehicle more efficient and safer.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.5
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• pp.557-563
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• 1997

The unsteady flow in three-dimensional cubic cavity with narrow channel at upper region is investigated experimentally for three kinds of Reynolds number, 1*10/sup 4/, 3*10/sup 4/ and 5*10/sup 4/ based on the cavity width and cavity inlet mean flow velocity. Instant velocity vectors are obtained simultaneously at whole field by PIV(Particle Image Velocimetry). Wall pressure distributions are estimated using Poisson equation from the velocity data. Results of PIV reveal that severe unsteady flow fluctuation within the cavity are remarkable at all Reynolds numbers and sheared mixing layer phenomena are also found at the region where inlet driving flow is collided with the clock-wise rotating main primary vortex. Instant velocity profiles reveal that deformed forced vortex formation is observed throughout the entire region and spanwise kinetic energy migration is conspicuous.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.7
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• pp.72-78
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• 2008

The line-of-sight(LOS) stabilization system is a precision electro-mechanical gimbals assembly for suppressing vibration due to its environment and tracking the target in a desired direction. This paper describes the design of gimbals system to reject the disturbance and to improve stabilization. The controller consists of a DSP with transducer and actuator interfaces. Unknown parameters of the gimbals are estimated by the signal compression method. The cross-correlation coefficient between the impulse response from the assumed model and the one from model of the gimbals is used to obtain the better estimation. The quasi-impulse response through linear element included in the gimbals could be obtained by the signal compression method. The unknown parameter of the linear element could be estimated as comparing the bode plots for impulse response from gimbals with them from model's response.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.16-17
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• 2015

본 논문에서는 실내 환경 중 TV 시청환경에서 마이크로폰 어레이를 이용하여 다양한 다중 음원 방향을 추정하는 기법을 제안한다. 제안된 기법은 기존의 하나의 음원에 특화되어 있는 GCC-PHAT 기반의 방법을 GCC-PHAT 버퍼와 NMF를 도입하여 다중음원의 방향 추정을 가능하게 만들었다. 제안된 기법의 성능을 평가하기 위해서 실 거주 환경에서 발생하는 소음원과 TV 소리 방향 추정 결과에 대한 실측치와 추정치 간의 오차인 절대 평균오차를 측정하였으며, 실험 결과 제안한 기법이 기존의 방법인 GCC-PHAT보다 우수한 추정 성능을 보임을 확인하였다.