• Steel and Composite Structures
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• 제37권5호
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• pp.621-632
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• 2020

This research deals with the study of vibrational behavior of armchair and zigzag single-walled carbon nanotubes invoking extended Love shell theory. The effects of different physical and material parameters on the fundamental frequencies are investigated. By using volume fraction for power law index, the fundamental natural frequency spectra for two forms of single-walled carbon nanotubes are calculated. The influence of frequencies against length-to-diameter ratios with varying power law index are investigated in detail for these tubes. To discretize the governing equation in eigen-value form, wave propagation approach is developed. Complex exponential functions have been used and the axial model depends on boundary condition that has been described at the edges of carbon nanotubes to calculate the axial modal dependence. Computer software MATLAB is utilized for the frequencies of single-walled carbon nanotubes and current results shows a good stability with comparison of other studies.

• 대한원격탐사학회지
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• 제31권1호
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• pp.11-20
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• 2015

This study aimed to investigate the canopy growth conditions and the accuracy of phenological stages of paddy rice using ground-based remote sensing data. Plant growth variables including Leaf Area Index (LAI) and canopy reflectance of paddy rice were measured at the experimental fields of Chonnam National University, Gwangju, Republic of Korea during the crop seasons of 2011, 2012, and 2013. LAI values were also determined based on correlations with Vegetation Indices (VIs) obtained from the canopy reflectance. Three phenological stages (tillering, booting, and grain filling) of paddy rice could be identified using VIs and a spatial index (NIR versus red). We found that exponential relationships could be applied between LAI and the VIs of interest. This information, as well as the relationships between LAI and VIs obtained in the present study, could be used to estimate and monitor the relative growth and development of rice canopies during the growing season.

• 산업경영시스템학회지
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• 제25권6호
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• pp.48-53
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• 2002

품질보증 부분에서 대부분 통계적 수법들은 기지분포를 가정하여 데이터를 분석하고 있다. 예를 들면 공정능력에서는 정규분포를 가정하고 있고, 신뢰성 분석에서는 지수분포, 대수정규분포 또는 와이블분포 등을 가정하고 있다. 만약 이러한 것들이 가정하는 확률분포와 크게 편의될 때 도출된 결론은 그 유효성을 상실하게 된다. 따라서 공정이 정규분포를 하지 않는다면 정규분포에 기초한 공정능력지수의 사용은 부정확한 공정의 정보를 제시하게 된다. 이러한 문제를 해결하기 위하여 그 사례로 소표본일 경우 정규성의 유무를 Lilliefors 검정통계량으로 검정하였다. 그리고 최우추정량(MLE), 수정적률추정량(MME), 및 적률추정량(ME)을 사용하여 모수추정을 하여 그 각각의 경우에 공정능력지수로 평가하였다. 공정능력지수의 평가는 공정이 지수분포를 하는 경우에 적합한 공정능력지수($C_{pe}$)를 제안하고, 이것의 대안으로써 Pearson 시스템, Johnson 시스템 및 Burr 시스템과도 비교평가 하였다.

• 산업경영시스템학회지
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• 제20권43호
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• pp.47-57
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• 1997

As a general index in surface quality of machined products, surface roughness is to measure worker's skill level, a ground product quality and machining accuracy, etc. The surface roughness is defined by a function of rotational speed and radius of a grinding wheel, distances of active grains composed of the wheel, and feed of a grinder's worktable. To predict surface roughness in horizontal surface grinding operations, probability distributions were used. Probability distribution functions(p.d.f.) of surface roughness were found as results when the size of active grains(=the radius of a grinding wheel) is given as uniform, exponential distribution, and the distance between active grains follows the distributions of uniform, exponential. For each pdf case, probabilistic features of surface roughness were also analyzed and presented. This study is a substantial step for determining mathematically the surface roughness instead of using empirical approaches. More works should be presented to develop a general model by which an accurate roughness value can be obtained in horizontal surface grinding operations.

• 대한산업공학회지
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• 제24권4호
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• pp.485-492
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• 1998

Most forecasting models often fail to produce appropriate forecasts because we build a model based on the assumption of the data being generated from the only one stochastic process. However, in many real problems, the time series data are generated from one stochastic process for a while and then abruptly undergo certain structural changes. In this paper, we assume the basic underlying process is the simple state-space model with random level and deterministic drift but interrupted by three types of exogenous shocks: level shift, drift change, outlier. A Bayesian procedure to detect, estimate and adapt to the structural changes is developed and compared with simple, double and adaptive exponential smoothing using simulated data and the U.S. leading composite index.

• 대한원격탐사학회지
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• 제33권4호
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• pp.401-410
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• 2017

Estimation of snow depth using optical image is conducted by using correlation with Snow Cover Fraction (SCF). Various algorithms have been proposed for the estimation of snow cover fraction based on Normalized Difference Snow Index (NDSI). In this study we tested linear, quadratic, and exponential equations for the generation of snow cover fraction maps using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua satellite in order to evaluate their applicability to the complex terrain of South Korea and to search for improvements to the estimation of snow depth on this landscape. The results were validated by comparison with in-situ snowfall data from weather stations, with Root Mean Square Error (RMSE) calculated as 3.43, 2.37, and 3.99 cm for the linear, quadratic, and exponential approaches, respectively. Although quadratic results showed the best RMSE, this was due to the limitations of the data used in the study; there are few number of in-situ data recorded on the station at the time of image acquisition and even the data is mostly recorded on low snowfall. So, we conclude that linear-based algorithms are better suited for use in South Korea. However, in the case of using the linear equation, the SCF with a negative value can be calculated, so it should be corrected. Since the coefficients of the equation are not optimized for this area, further regression analysis is needed. In addition, if more variables such as Normalized Difference Vegetation Index (NDVI), land cover, etc. are considered, it could be possible that estimation of national-scale snow depth with higher accuracy.

• Journal of Biosystems Engineering
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• 제13권2호
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• pp.46-50
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• 1988

The estimation of beam radiation intensity on a tilted surface is very important to the design of a solar energy system. In order to get the beam radiation intensity, it is required to calculate the ratio of the diffuse solar radiation to the global radiation ($k_d$). The data measured at Chung-Buk National University. Cheong-ju, (from May 16, 1985 to Nov, 10, 1987) were analysed to define the relationship between hourly clearness index ($k_t$) and diffuse ratio ($t_d$). The results are is follow: 1. The percent of clearness index($k_t$) of less than 0.3 and of more than 0.8 were 2.7% and 3.1% respectively, and between 0.5 and 0.8 was 76.5%. 2. The regression equation between $k_t$ and $k_d$ was an exponential function as: $$k_d=\[{1\hspace{120}:\hspace{10}(k_t<0.1)\\1.28{\times}0.074^{k_t}\hspace{30}:\hspace{10}(0.1{\leq}=k_t<0.9)\\0.12\hspace{98}:\hspace{10}(0.9{\leq}=k_t)$$ There was a little difference between the result. of this study based on the data of 30 months and the results of previous study (ITRA 2(1):42-47, 1986.) based on the data of 8 months. 3. The hourly exponential regression equation between $k_t$ and $k_d$ was $k_d=A{\times}8^{k_t}$ and the values of constant A and coefficient B of the: equations are as the following table; 4. The percent of $k_d$ of less than 0.4 was 72.9% and of more than 0.7 was 6.6%. 5. Total mean value of $k_t$ and $k_d$ wert 0.56 and 0.32, respectively. From 10:00 to 15:00 o'clock the total mean value of $k_t$ was smaller that the hourly man value of $k_t$ and the one or $k_d$ larger.

• E2M - 전기 전자와 첨단 소재
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• 제8권2호
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• pp.129-135
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• 1995

SiO thin films are deposited by evaporator the refractive index of wave length, photon energy and the absorptive rate of these films are measured by spectroscopic ellipsometer. It is derived the absorptive rate and permitivity of SiO thin films from the equations that calculating the refractive index. And the result show good agreement with the calculated values and experimental values. As a result, the wave length of light is increased in the condition that the angle of incidence is fixed on SiO thin film, the basic absorption and the absorption impurities are found in the low wave length (below 450 nm in this study) and the reflective absorption and conductive absorption is increased by the form of exponential function over the low wavelength. The absorptive rate is increased by increased the angle of incidence and thickness of SiO film for the insulating layer. As the thickness of SiO film is increased, the value of complex permitivity is decreasing and as wave length of incidence is increased., the value of dielectric is linearly increasing.

• 한국지능시스템학회논문지
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• 제21권1호
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• pp.25-28
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• 2011

본 연구는 퍼지가설 검정을 위하여 퍼지수로 주어진 데이터에 대한 데이터의 조건을 제시하였고 면적비에 의한 동의지수법을 정의한 후 균일최강력 퍼지검정법을 제안하였다. 또한 균일최강력 퍼지 검정을 위하여 유의수준에 의한 신뢰한계를 제시하였다. 예증으로서 지수분포에서 얻은 랜덤셈플을 우도비에 의한 최강력 기각역을 구하여 동의지수법을 이용한 카이제곱분포의 퍼지검정법을 제시하였다.

• 한국안광학회지
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• 제5권2호
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• pp.145-150
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• 2000

망막의 광원에 대한 순응은 간상체-추상체에 의해 시간에 따라 명순응-암순응의 2개 곡선으로 이루어진다. 시간에 따른 순응도는 역치를 측정하여 얻어지며 분절점을 중심으로 2개의 감소 곡선이 된다. 암순응은 $T_{min}$, $a_r$, $a_c$, $T_{0(r)}$, $T_{0(c)}$, $t_b$, $t_c$의 파라미터로 이루어진 exponential decay 함수로 표현 할 수 있다. $t_b$ 이하의 곡선은 추상체의 순응 민감도 곡선이고 $t_b$ 이상 곡선은 간상체의 순응 민감도를 나타낸다. Exponential decay 함수는 망막 위치에 따른 순암순응 시표의 각도에 따른 암순응, 조명 크기에 따른 암순응, 나이에 따른 암순응 등의 암순응 함수에 잘 적용되었다. Decay parameter가 암순응 함수의 성질을 표현할 수 있어 지표로써 사용할 수 있다.