• Nuclear Engineering and Technology
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• 제28권1호
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• pp.72-78
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• 1996

단면적 평가를 위한 회귀분석 프로그램 COVAFIT를 개발하고 이를 실험 결과로서 보고되는 단면적을 평가하는데 적용하였다. 가중 최소제곱 선형 회귀 방법을 적용하였는데 이 때 새로 유도한 고차 다항식을 사용하였다. 점증하는 핵자료의 공분산에 대한 요구에 부응하여, 이 프로그램은 단면적 실험치와 함께 제공되는 분산-공분산 자료를 평가에 반영할 수 있다는 특징을 가지고 있다. MeV 에너지 영역에서 천연 산소 및 $O^{16}$의 중성자 전단면적과 세 가지 $C^{11}$ 생산 반응의 양성자 반응 단면적 평가를 통하여 사용방법론의 적절성과 COVAFIT의 유용성을 확인하였다.

• 대한안전경영과학회지
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• 제14권1호
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• pp.225-233
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• 2012

The research discusses interrelationship of structural and reliability importance measures which used in the probabilistic safety assessment. The most frequently used component importance measures, such as Birnbaum's Importance (BI), Risk Reduction (RR), Risk Reduction Worth (RRW), RA (Risk Achievement), Risk Achievement Worth (RAW), Fussel Vesely (FV) and Critically Importance (CI) can be derived from two structure importance measures that are developed based on the size and the number of Minimal Path Set (MPS) and Minimal Cut Set (MCS). In order to show an effectiveness of importance measures which is developed in this paper, the three representative functional structures, such as series-parallel, k out of n and bridge are used to compare with Birnbaum's Importance measure. In addition, the study presents the implementation examples of Total Productive Maintenance (TPM) metrics and alternating renewal process models with exponential distribution to calculate the availability and unavailability of component facility for improving system performances. System state structure functions in terms of component states can be converted into the system availability (unavailability) functions by substituting the component reliabilities (unavailabilities) for the component states. The applicable examples are presented in order to help the understanding of practitioners.

• 대한공간정보학회지
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• 제14권4호통권38호
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• pp.27-36
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• 2006

현재 위성영상에서 정확한 위치정보를 얻고자 할 때 일반적으로 위성영상에 대응되는 지상에서의 위치 정보, 즉 지상기준점이 필요하다. 이 논문에서는 지상기준점 없이 영상의 위치 정보를 얻기 위하여 동일궤도에서 연속적으로 촬영한 위성영상들 중에서 한 위성영상의 획득한 기준점으로 모델을 수립한 뒤, 수립된 센서모델을 동일궤도상의 다른 영상에 적용할 때의 센서모델의 정확도를 분석하고자 한다. 분석에 사용한 센서모델은 궤도기반센서모델을 사용하며, 여러 위성의 위치 자세 내삽법 및 미지수조합을 시험하여 궤도모델링에 적합한 내삽법(interpolation)과 최적의 미지수 조합을 알아보고자 했다. 실험은 총 420Km의 길이에 해당하는 SPOT-3의 영상 7장과 GPS수신기에서 취득한 기준점을 사용하였다. 실험결과 단일영상에서는 내삽법과 미지수 조합에 따른 결과의 차이는 크게 나타나지 않았으나 궤도모델링 시에는 미지수 조합과 자세와 위치의 내삽법에 따라 다양한 결과가 나타남을 알 수 있다. 또한 적절한 미지수조합과 내삽법을 사용하면 한 영상에서 추출한 기준점만으로 총 420Km의 궤도를 정확하게 모델 할 수 있음을 알 수 있었다.

• 한국측량학회지
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• 제20권1호
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• pp.21-31
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• 2002

이 연구는 원격탐사 영상의 분류정확도를 향상시키기 위한 방법으로써 신경망 이론과 퍼지집합이론을 각각 적용하였다. 원격탐사 영상은 토지피복도, 식생도, 지질도 등 주제도를 만드는데 많이 이용되고 있다. 원격탐사 영상의 감독분류에 대한 정확도는 트레이닝 지역의 선정, 분류항목의 할당 문제로 인해 많은 차이를 보인다. 일반적인 영상 분류법은 영상 내의 모든 영상소가 균질하다고 가정한다. 그러나, 이러한 가정은 영상내의 수많은 혼합 영상소를 분류해내는 데에는 적합하지 않다. 이러한 문제를 극복하기 위해 퍼지 집합이론을 적용하였으며, 퍼지 집합이론의 멤버쉽을 이용하였다. 퍼지 집합이론은 하나의 영상소를 멤버쉽의 정도에 따라 여러 가지 항목으로 분류할 수 있는 장점이 있다. 그러나, 퍼지분류법과 통계학적인 분류법은 화소값의 분포가 비정규적일 때 좋지 않은 분류 결과를 나타내며 처리 시간이 늦고 많은 컴퓨팅 비용이 드는 단점이 있다. 그 대안적인 방법으로서 신경망분류법을 들 수 있는데, 신경망 분류법은 비모수적 분류법으로서 일반적인 분류기법보다 좀 더 좋은 결과를 나타내고 있고, 한번 트레이닝 되면 빠르게 데이터를 분류할 수 있다.

• Geomechanics and Engineering
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• 제13권4호
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• pp.585-600
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• 2017

This study deals with simple solutions for a spherical or circular opening excavated in elastic-brittle plastic rock mass compatible with a linear Mohr-Coulomb (M-C) or a nonlinear Hoek-Brown (H-B) yield criterion. Based on total strain approach, the closed-form solutions of stresses and displacement are derived simultaneously for circular and spherical openings using original H-B and M-C yield criteria. Two simple numerical procedures are proposed for the solution of generalized H-B and M-C yield criteria. Based on incremental approach, the similarity solution is derived for circular and spherical openings using generalized H-B and M-C yield criteria. The classical Runge-Kutta method is used to integrate the first-order ordinary differential equations. Using three data sets for M-C and H-B models, the results of the radial displacements, the spreading of the plastic radius with decreasing pressure, and the radial and circumferential stresses in the plastic region are compared. Excellent agreement among the solutions is obtained for all cases of spherical and circular openings. The importance of the use of proper initial values in the similarity solution is discussed.

• 대한기계학회논문집A
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• 제29권12권
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• pp.1586-1596
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• 2005

In this paper, a structural damage identification method (SDIM) is developed to identify the line crack-like directional damages generated within a cylindrical shell. First, the equations of motion for a damaged cylindrical shell are derived. Based on a theory of continuum damage mechanics, a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness, which is dependent of the size and the orientation of the damage with respect to the global coordinates. The present SDIM is then derived from the frequency response function (FRF) directly solved from the equations of motion of a damaged shell. In contrast with most existing SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM may require only the FRF-data measured at damaged state. By virtue of utilizing FRF-data, one may choose as many sets of excitation frequency and FRF measurement point as needed to acquire a sufficient number of equations for damage identification analysis. The numerically simulated damage identification tests are conducted to study the feasibility of the present SDIM.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.386-389
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• 1999

In this study, visible and near infrared channels of NOAA/AVHRR data were used to classify land use and vegetation types over Korean peninsula. Analyzing forest stand structures and prediction of forest productivity using satellite data were also reviewed. Land use and land cover classification was made by unsupervised clustering methods. After monthly Normalized Difference Vegetation Index (NDVI) composite images were derived from April to November 1998, the derived composite images were used as temporal feature vector's in this clustering analysis. Visually interpreted, the classification result was satisfactory in overall for it matched well with the general land cover patterns. But subclassification of forests into coniferous, deciduous, and mixed forests were much confused due to the effects of low ground resolution of AVHRR data and without defined classification scheme. To investigate into the forest stand structures, digital forest type maps were used as an ancillary data. Forest type maps, which were compiled and digitalized by Forestry Research Institute, were registered to AVHRR image coordinates. Two data sets were compared and percent forest cover over whole region was estimated by multiple regression analysis. Using this method, other forest stand structure characteristics within the primary data pixels are expected to be extracted and estimated.

• Journal of Astronomy and Space Sciences
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• 제25권3호
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• pp.239-244
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• 2008

Two kinds of important issues on Titius-Bode's relation have been discussed up to now: one is if there is a simple mathematical relation between distances of natural bodies orbiting a central body, and the other is if there is any physical basis for such a relation. These may be tackled by answering a question whether Titius-Bode's relation is valid universally in exo-planetary systems. We have examined whether Titius Bode's relation is also applicable to exo-planetary systems by statistically studying the distribution of the ratio of rotational periods of two planets in an exo-planetary system, 55 Cnc, by comparing it with that derived from Titius-Bode's relation. We find that the distribution of the ratio of rotational periods of randomly chosen two planets in the 55 Cnc system is apparently inconsistent with that derived from Titius-Bode's relation. The probability that two data sets are drawn from the same distribution function is 50%. We also find that the Fourier power spectra show that the distribution of the semi-major axis of planets in the 55 Cnc system seems to be stretched. We conclude by pointing out that large numbers of planets should be examined to more convincingly explain the distribution of the distance of planetary formation regions.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.973-976
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• 2006

The oscillations of the Caspian Sea level represent a result of mutually related hydrometeorological processes. The change in the tendency of the mean sea level variations that occurred in the middle 1970s, when the long-term level fall was replaced by its rapid and significant rise, represents an important indicator of the changes in the natural regime of the Caspian Sea. Therefore, sea level monitoring and long-term forecast of the sea level changes represent an extremely important task. The aim of this presentation is to show the experience of application of satellite altimetry methods to the investigation of seasonal and interannual variability of the sea level, wind speed and wave height, water dynamics, as well as of uplift of the Earth’s crust in different parts of the Caspian Sea and Kara-Bogaz-Gol Bay. Special attention is given to estimates of the Volga River runoff derived from satellite altimetry data. The work is based on the 1992-2005 TOPEX/Poseidon (T/P) and Jason-1 (J-1) data sets.

• 공학논문집
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• 제6권1호
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• pp.161-168
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• 2004

In the present study, a simple method was successfully used for hydroxyapatite coatings on Ti-6AL-4V substrates deposited by using a sol-gel derived precursor. Prior to hydroxyapatite coating the samples were micropolished (0.1 micron) and divided into three sets. The first set, were the micropolished samples kept as such. The second set were coated with titania sol and the third set was treated with 5M NaOH. After three repetitions of hydroxyapatite coating procedures on each set and heat treatment at $600^{\circ}C$, the formation of hydroxyapatite has been confirmed by XRD analyses and the substrate material was found to be oxidized with negligible amount of CaO in the coating. The SEM studies revealed surface morphology. Hydroxyapatite, calcined at $600^{\circ}C$, displaying a porous structure arisen from heating of the bulk