• Wind and Structures
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• 제30권2호
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• pp.199-210
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• 2020

Building wind pressure coefficient transiting test is a new method to test the building wind pressure coefficient by using the wind generated by a moving vehicle, which is susceptible to natural wind and other factors. In this paper, the Commonwealth Advisory Aeronautical Research Council standard model with a scale ratio of 1:300 is used as the test object, and the wind pressure coefficient transiting test is repeated under different natural wind conditions to study the influence of natural wind. Natural wind is measured by an ultrasonic anemometer at a fixed location. All building wind pressure coefficient transiting tests meet the test conditions, and the vehicle's driving speed is 72 km/h. The mean wind pressure coefficient, the fluctuating wind pressure coefficient, and the correlation coefficient of wind pressure are used to describe the influence of natural wind on the building wind pressure coefficient transiting test qualitatively and quantitatively. Some rules, which can also help subsequent transiting tests, are also summarized.

• Journal of Astronomy and Space Sciences
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• 제29권4호
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• pp.363-374
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• 2012

This paper studies the problem of tracking a re-entry vehicle (RV) in order to predict its impact point on the ground. Re-entry target dynamics combined with super-high speed has a complex non-linearity due to ballistic coefficient variations. However, it is difficult to construct a database for the ballistic coefficient of a unknown vehicle for a wide range of variations, thus the reliability of target tracking performance cannot be guaranteed if accurate ballistic coefficient estimation is not achieved. Various techniques for ballistic coefficient estimation have been previously proposed, but limitations exist for the estimation of non-linear parts accurately without obtaining prior information. In this paper we propose the ballistic coefficient ${\beta}$ model-based interacting multiple model-extended Kalman filter (${\beta}$-IMM-EKF) for precise tracking of an RV. To evaluate the performance, other ballistic coefficient model based filters, which are gamma augmented filter, gamma bootstrapped filter were compared and assessed with the proposed ${\beta}$-IMM-EKF for precise tracking of an RV.

• 소성∙가공
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• 제18권5호
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• pp.410-415
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• 2009

Experimental and numerical studies were performed to examine the effect of material temperature and reduction ratio on friction coefficient during hot flat rolling. We carried out a single pass pilot hot flat rolling test at the temperatures range of $900{\sim}1200^{\circ}C$ and measured the spread of deformed material while reduction ratio varied from 20% to 40%. Materials used in this study were a high carbon steel and two alloy steels. The dimension of specimen used in hot rolling experiment was $50mm{\times}50mm{\times}300mm$. We performed a series of finite element simulation of the hot rolling process to compute the friction coefficient change in terms of steel grade and reduction ratio. Results showed that temperature dependency of friction coefficient is not noteworthy but the effect of reduction ratio on friction coefficient is quite large. For high carbon steel, friction coefficient at reduction ratio of 30% is lower than that at that of 20%. Meanwhile friction coefficient at reduction ratio of 40% was one and half times large compared with that at that of 20%. The effect of steel grade on friction coefficient was significant when reduction ration was large, e.g., 40%.

• 한국의류학회지
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• 제20권3호
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• pp.519-526
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• 1996

To investigate the relationship between plane and side drape coefficient, the drape tester designed in which coordinate of projected outline of draped specimen could be recorded. By using this drape tester, the three dimensional shape, plane and side drape coefficient were obtained from coordinate of plane projected shape, and furthermore examined the tendency in changes of drape coefficient in terms of diameter of specimen, deflection angle, and bending rigidity. The side drape coefficients were constant regardless of changes in diameter of specimen. The plane drape coefficients, however, made a little difference according to changes in diameter of specimen. The experimental drape coefficient agreed well with the theoretical drape coefficient according to deflection angle. In the meanwhile, when the plane drape coefficients were regressed with the side drape coefficents, regression equation was $y=0.375x-0.002x^2+6.9\times10^{-5}x^3$. When the $\overline{\theta_s}$ is mean of deflection angle of selected points which have the longest and shortest distance from center point in the node, the theoretical drape coefficient calculated from $\overline{\theta_s}$ has high correlation with experimental drape coefficient. The plane and side drape coefficient changed linearly with increasing the bending length, $\sqrt[3]{EI/w}$.

• 아태비즈니스연구
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• 제8권2호
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• pp.15-30
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• 2017

This study analyzes the relationship between income inequality and economic growth. Gini coefficient (market income), the deciles income inequality index and per capita real GDP were analyzed. Furthermore, various cointegration tests were tried to improve the reliability of the test results. From the weak exogeniety test of between per capita real GDP and the Gini coefficient (market income), per capita real GDP has a weak exogeneity while the Gini coefficient is endogenous. From the various cointegration tests, we found out that there is a cointegration between Gini coefficient and per capita real GDP. Moreover, it is estimated that per capita real GDP has a positive effect on the Gini coefficient (market income). In the VAR Granger causal analysis, per capita real GDP affects the Gini coefficient (market income), but it is difficult to say that the Gini coefficient (market income) always has an effect on per capita real GDP. Also, the impulse-response function of the VAR model shows that per capita real GDP temporarily reduces the Gini coefficient (market income), and then increases it over time. Accordingly, it is necessary for the policies to improve not only the distribution structure but also income distribution through economic growth.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.63-63
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• 2021

Bed shear stress is important variable in river flow analysis. The bed shear stress has an effects on bed erosion, sediment transport, and mean flow characteristics. Quadratic formula to estimate bed shear stress is widely used, 𝜏=𝜌c_fu|u| in which friction coefficient, c_f, needs to be assigned to numerical models. The aim of this study is to estimate Chezy coefficient using bathymetry data measured by ADCP. Bed form geometry variables will be estimated form bed profile, then Chezy coefficient will be determined using estimated bed form geometry variables in order to set friction coefficient to numerical model. From the probability density function obtained from the bathymetry data, Chezy coefficient will be randomly generated since Chezy coefficient is not uniform over the space and it does not depend on spatial variables such as water depth and distance from river bank. Numerical test will be performed to find to demonstrate randomly extracted Chezy coefficient is appropriate. The result of this study is valuable in that the friction coefficient is estimated in consideration of the bed profile, and as a result, uncertainty of the friction coefficient can be reduced.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4096-4101
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• 2023

Radon is a radioactive gas produced from the uranium-238 series. Radon gas affects public health and is the second cause of lung cancer. The study samples were collected from one area of the city of Jazan, southwest of the Kingdom of Saudi Arabia. The influence of engineering and physical parameters on the emanation coefficient of gas and other gas parameters was studied. Parameters for radon were measured using a CR-39 Solid-State Nuclear Track Detector (SSNTD) through a sealed emission container. The results showed that the emanation coefficient was affected directly by the change in the grain size of the soil. All parameters of measured radon gas have the same behavior as the emanation coefficient. The relationship between particle size and emanation coefficient showed a good correlation. The values of the emanation coefficient were inversely affected by the mass of the sample, and the rest of the parameters showed an inverse behavior. The results showed that increasing the volume of the container increases the accumulation of radon sons on the wall of the container, which increases the emission factor. The rest of the parameters of radon gas showed an inverse behavior with increasing container size. The results concluded that changing the engineering and physical parameters has a significant impact on both the emanation coefficient and all radon parameters. The emanation coefficient affects the values of the radiation dose of an alpha particle.

• 한국콘텐츠학회논문지
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• 제21권9호
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• pp.299-311
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• 2021

본 연구는 중국 통계청이 2017년의 산업연관표를 활용하여 중국 교육산업의 국민경제에 대한 파급효과를 분석함으로써 향후 중국 교육산업의 활성화를 위한 정책적 자료로 활용하는데 목적이 있다. 이러한 목적을 달성하기 위하여 산업연관표 기초분류 149개 산업을 32개 산업으로 분류하였다. 이러한 분류를 바탕으로 중국 교육산업의 생산유발계수, 감응도계수, 영향력계수, 소득유발계수, 생산세유발계수, 노동유발계수 등에 대하여 분석함으로써 중국 교육산업을 중심에 놓고 교육산업이 전체산업 속의 위치와 다른 산업 간의 관계를 파악하며 중국 교육산업의 경제적 파급효과를 알아보고자 한다. 분석 결과는 중국 2017년 교육산업의 생산유발계수 열합계는 1.719, 행 합계는 1.063, 감응도계수는 0.012, 영향력 계수는 0.020, 소득유발계수는 0.667, 생산세 유발계수는 0.035, 최종수요 10억 위안이 발생할 경우 노동유발계수는 총 31,254명(간접15,541명, 직접15,713명) 등을 보여주고 있다. 분석결과에 따라 본 연구는 중국 교육산업의 진일보 발전을 위하여 정부의 지지, 기술도입과 새로운 운영 모델의 응용, 정책적인 규정, 제도의 개선과 시장에 대한 효율적인 감독이 요구된다는 시사점을 제시하였다.

• 산업기술연구
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• 제28권B호
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• pp.71-79
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• 2008

Reports about coefficients of consolidation in horizontal direction of marine clays located at seven different sites on western and southern coast area in Korea were reviewed and characteristics of them were investigated. As results of analyses, for relation between the depth of ground and coefficients, any trend and correlation between them can not be found since they are more influenced by the nature of geological formation rather than the depth of ground. Dissipation time t50, one of important factors in estimating value of coefficient of consolidation in horizontal direction, was found to be quite related to them. For the correlation between the maximum pore pressure developed and coefficients, coefficient of consolidation in the horizontal direction tend to decrease with increase of the maximum pore pressure whereas the ground water level or static pore pressure do not have any specific correlation with those coefficients. Values of coefficient tends to increase with values of liquid limit, plastic limit and plastic index and thus they are found to be directly influenced by the contents of fines. Values of coefficient of consolidation in horizontal direction are also increased with increases of permeability in horizontal direction and coefficient of consolidation in vertical direction. They were highly correlated between coefficient of consolidation and permeability in horizontal direction while values of coefficient of consolidation in horizontal direction have a relatively low correlation with values of coefficient of consolidation in horizontal direction. Sometimes, coefficient of consolidation in horizontal direction obtained from field tests were estimated 2-3 times greater than those from laboratory tests.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.194-201
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• 2000

In this study the modified seismic coefficient method for seismic analysis of buried box structures is developed for practical purpose. The loading coefficient in the modified seismic coefficient method is determined from the results of the response displacement analysis. In the developed method adequate velocity response spectrum in accordance with soil condition is also needed to seismic design of buried box structures, In order to investigate applicability of the modified seismic coefficient method various analyses are performed with different parameters such as depth of base rock height and width of box buried depth and value of standard penetration test. Results from the modified seismic coefficient method are compared with those of the response displacement method in terms of the maximum bending moment and the location of it. From the comparison it is shown that the feasibility of the modified seismic coefficient method for seismic analysis of buried box structures.