• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2008년도 공동학술대회
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• pp.167-172
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• 2008

경북 문경군 가은읍 가은역 일대 석회암 분포 지역에서 지하 공동의 위치 및 발달 양상을 파악하기 위하여 고정밀 중력탐사를 하였다. 측점 간격은 4m로 하여 모두 약 1,100 측점에서 중력을 측정하였다. 잔여 부게 이상도에서 가장 낮은 중력 이상대를 지나는 3개의 측선에 대하여 MS(minimum support) 역산으로 밀도 분포 단면을 작성하였다. 또한, growing body 역산을 이용하여 3차원 밀도 분포 영상을 구하였다. 2차원과 3차원 밀도 분포도는 공동이 발달한 지역을 잘 가리키고 있으며, 석회암이 지하수에 부분적으로 용해되어 복잡한 형태의 공동 시스템을 구성하고 있고 부분적으로는 상당히 얕은 곳까지 발달해 있을 것으로 해석된다.

• Journal of Astronomy and Space Sciences
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• 제14권1호
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• pp.24-32
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• 1997

Alfven파에 의한 항상풍을 가정하고 운동방정식을 수치적분하여 속도분포를 구하였다. 질량이 보존된다면 밀도분포 속도분포와 밀접한 관계를 가지므로 가정되는 초기 밀도 개수의 값에 따라 선윤곽이 변화하는 효과를 계산하였다. 실제적인 항성풍 모형을 계산하기 위해 Schroder(1986)의 관측과 잘 맞는 초기 밀도 개수 $N_0=5.5{\times}10^{12}/cm^3$의 경우와 $N_0=10^9,10^{10},10^{11}/cm^3$의 경우를 계산하였으며 초기 밀도 개수가 작을수록 속도분포가 급격하고 더 큰 종속도를 보였다. 또한 공전궤도위상 0.06과 0.78에서의 선윤곽을 계산하였고, $N_0$가 작을수록 더욱 강하고 좁은 흡수요소를 가졌으며 이로 인해 방출선의 극대가 청색편이되어 나타났다.

• 한국재료학회지
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• 제24권7호
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• pp.388-392
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• 2014

$Cu_2O$ nanowires were synthesized at large scale on copper plate by thermal oxidation in air. The effect of oxidation time and temperature on the morphology of the nanowires was examined. The oxidation time had no effect on the diameter of the nanowires, while it had a great effect on the density and the length of the nanowires. The density and the length of the nanowires increased, and then decreased, with increasing oxidation time. The oxidation temperature had a tremendous effect on the size-distribution as well as the density of the nanowires. When the oxidation temperature was $700^{\circ}C$, uniform size-distribution and high density of the nanowires was achieved. At lower and higher temperatures, the density of the nanowires was lower, and they displayed a broader size-distribution. It is suggested that the $Cu_2O$ nanowires were grown via a vapor-solid mechanism because no catalyst particles were observed at the tips of the nanowires.

• 한국광학회지
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• 제21권3호
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• pp.97-102
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• 2010

전산모사를 통하여 LGP 출력 분포를 조절할 수 있는 패턴 밀도 함수를 찾고 그 효과를 조사하였다. 패턴 밀도 함수, 즉 패턴 간격은 [Pexp(-y/70)+Qexp(+y/25)]R로 조사되었다. 이 함수를 이용하여 패턴의 간격을 조절하는 방식으로 반구형 패턴이 장착된 도광판을 설계하여 도광판 출력 분포를 분석한 결과 출력 분포가 등간격 패턴에 의한 출력 분포에 비하여 확연히 개선되는 것을 확인하였다. 또한 이 함수를 피라미드 패턴에 적용하여 도광판의 출력을 조사하였는데, 반구형 패턴의 경우와 마찬가지로 출력 분포가 개선되는 것을 확인하였다.

• Structural Engineering and Mechanics
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• 제86권3호
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• pp.349-359
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• 2023

This paper presents a technique for determining the optimal number of elements in stochastic finite element analysis based on reliability analysis. Using the change-of-variable perturbation stochastic finite element approach, the probability density function of the dynamic responses of stochastic structures is explicitly determined. This method combines the perturbation stochastic finite element method with the change-of-variable technique into a united model. To further examine the relationships between the random fields, discretization of the random field parameters, such as the variance function and the scale of fluctuation, is also performed. Accordingly, the reliability index is calculated based on the explicit probability density function of responses with Gaussian or non-Gaussian random fields in any number of elements corresponding to the random field discretization. The numerical examples illustrate the effectiveness of the proposed method for a one-dimensional cantilever reinforced concrete column and a two-dimensional steel plate shear wall. The benefit of this method is that the probability density function of responses can be obtained explicitly without the use simulation techniques. Any type of random variable with any statistical distribution can be incorporated into the calculations, regardless of the restrictions imposed by the type of statistical distribution of random variables. Consequently, this method can be utilized as a suitable guideline for the efficient implementation of stochastic finite element analysis of structures, regardless of the statistical distribution of random variables.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1996년도 추계학술발표회논문집
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• pp.63-66
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• 1996

Electron temperature and electron density were measured in a radio-frequency(rf) inductively coupled plasma using probe measurements. Measurements were made in an argon discharge for pressures from 10 to 100mTorr and input rf power from 100 to 800W. Spatial distribution Electron temperature and electron density were measured for discharge with same aspect ratio. Electron temperature and Electron density were found to depend on both pressure and power. Electron density was creased with increasing pressure, but peaked in a 70mTorr discharge. Radial distribution of the electron density was peaked in the plasma fringes. These results were compared to a simple model of inductively coupled plasmas.

• Communications for Statistical Applications and Methods
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• 제14권3호
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• pp.583-592
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• 2007

Given the moments of a symmetric random variable, its density and distribution functions can be accurately approximated by making use of the algorithm proposed in this paper. This algorithm is specially designed for approximating symmetric distributions and comprises of four phases. This approach is essentially based on the transformation of variable technique and moment-based density approximants expressed in terms of the product of an appropriate initial approximant and a polynomial adjustment. Probabilistic quantities such as percentage points and percentiles can also be accurately determined from approximation of the corresponding distribution functions. This algorithm is not only conceptually simple but also easy to implement. As illustrated by the first two numerical examples, the density functions so obtained are in good agreement with the exact values. Moreover, the proposed approximation algorithm can provide the more accurate quantities than direct approximation as shown in the last example.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2415-2421
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• 2020

The axial heterogeneous void distribution in a fuel channel is a relevant and important issue during nuclear reactor analysis for LWR, especially for boiling water channel-type reactors. Variation of the coolant density in fuel channel has an effect on the neutron spectrum that will in turn have an impact on the values of absolute reactivity, the void reactivity coefficient, and the fuel isotopic compositions during irradiation. This effect is referring to as the history effect in light water reactor calculations. As the void reactivity effect is positive in RBMK type reactors, the underestimation of water density heterogeneity in 3D reactor core numerical calculations could cause an uncertainty during assessment of safe operation of nuclear reactor. Thus, this issue is analysed with different cross-section libraries which were generated with WIMS8 code at different reference water densities. The libraries were applied in single fuel model of the nodal code of QUABOX-CUBBOX/HYCA. The thermohydraulic part of HYCA allowed to simulate axial water distribution along fuel assembly model and to estimate water density history effect for RBMK type fuel.

• 한국국방경영분석학회지
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• 제28권2호
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• pp.56-69
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• 2002

A technique of finding both probability density and distribution function for interkilling times is considered and demonstrated. An important result is that any arbitrary interfiring time random variables fit to this study, The interfiring renewal density function given a certain interfiring probability density function can be applied to obtain the corresponding interkilling renewal density function which helps us to estimate the expected number of killing events in a time period. The numerical inversion of Laplace transformation makes these possible and the results appear to be excellent. In case of ammunition supply is limited, an alternative way of getting the probability density function of time to the killing is investigated. The convolution technique may give us a means of settling for this new problem.

• 한국정밀공학회지
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• 제13권7호
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• pp.66-77
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• 1996

Optimal topology design is to search the optimal configuration of a structure which can be used as a shape at the conceptual design stage. Our objective is to maximize the stiffness of the structures and ribs under a material usage constraintl. The density of each finite element is the design variable and its relationship with Young's modulus is expressed by quadratic form. The configuration is represented by the entire density distribution, the structural analysis is performed by finite element method and the optimiza- tion is performed by Feasible Direction Method. Feasible Direction Method can handle various problems simultaneously, that is, mult-objectives and multi-constraints. Total computation time can be reduced by the quadratic relationship between the density and the material property and fewer design variables than Homogenization Method. Toplogy optimization technique developed in this research is applied to design the shapes of the ribs.