• Journal of the Economic Geographical Society of Korea
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• v.1 no.1
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• pp.137-149
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• 1998

It is likely that the spatial structure of the intraurban accessibility as well as the accessibility value of each of the nodes in the subway network is affected by the addition of new linkages. The changes in the accessibility at individual nodes also affect the accessibility in the surrounding areas at some distances away from the nodes. Graph-theoretic algorithms have been developed as a proper measurement scheme for the nodal accessibility in tracked transport networks such as subway networks. However, the graph-theoretic measurements have limitations to estimate the spatial diffusion effect on the surrounding areas. This study proposes a new model for the spatial diffusion effect estimation of nodal accessibility increment in the subway network toward the surrounding areas. Since the distance decay trend of subway station use reflect the spatial diffusion effect of the accessibility of subway station toward the surrounding area. The model is deduced from the subway station use density function which is formulated by the questionnaire survey data.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.165-166
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• 2015

본 논문에서는 제주풍력단지에 대한 측정 데이터(measured wind power outputs)를 기반으로 제주 실측 풍력데이터를 이용하여 공간적인 상관관계 분석을 수행하고, 상관관계 감쇠거리(CDD; Correlation Decay Distance)를 적용하여 새로운 풍력발전단지에 대한 공간모델 적용 시 기존 풍력발전단지의 포함여부(set 또는 subset)를 결정하는 기준(Threshold)으로 활용하고자 한다. 이를 통해 풍력발전출력 예측에 공간모델을 적용하고, 정확도를 향상시키는 방안을 연구하고자한다.

• Journal of the Korean Association of Geographic Information Studies
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• v.12 no.2
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• pp.44-51
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• 2009

The main purpose of this study is to identify urban spatial structure by applying geographic information system and remote sensing data. This study identifies the urban spatial structure of non-megalopolis by analyzing the spatial distribution of population and employment in the case of Daegu metropolitan area. For this purpose, multi-temporal satellite image data (Landsat TM; 1995, 2000 and 2005) were utilized through the geographic information system. The distance-decay estimations in terms of population and employment density show that Daegu region as a whole shows monocentric urban characteristics. However, some evidences of polycentricism such as low explanation power of monocentric urban model, rises in multiple employment centers, decentralization of employment are emerging.

• Computational Structural Engineering : An International Journal
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• v.1 no.2
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• pp.139-150
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• 2001

An initial approach for the identification of physical causes underlying the spatial coherency of seismic ground motions it presented. The approach relies on the observation that amplitude and phase variability of seismic data recorded over extended areas around the amplitude and phase of a common, coherent component are correlated. It suffices then to examine the physical causes for the amplitude variability in the seismic motions, in order to recognize the causes for the phase variability and, consequently, the spatial coherency. In this study, the effect of randomness in the shear wave velocity at a site on the amplitude variability of the surface motions mi investigated by means of simulations. The amplitude variability of the simulated motions around the amplitude of the common component is contained within envelope functions, the shape of which suggests, on a preliminary basis, the trend of the decay of coherency with frequency.

• Journal of Korea Planning Association
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• v.54 no.2
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• pp.76-83
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• 2019

This study aims to empirically identify the effect of spatial accessibility, based on travel, on housing prices in the Korean capital region. More specifically, it has two research purposes: First, investigating the effect of comprehensive spatial accessibility, based on road network and actual trips from origin to destination, on average apartment price (Korean Won per square meter) at the level of Eup, Myeon and Dong; Second, identifying better accessibility index between Hansen's and Kalogirou and Foley's ones. The former represents a road-based travel time decay function with destination trips, while the latter is a function with origin trips as well as destination ones. The study employs spatial economic models considering spatial auto-correlative relationship as an appropriate methodology with such control independent indicators as population density, road density, educational environment and distances from CBDs. Analysis results demonstrate that spatial accessibility, based on road network and actual trips from origin to destination, has a statistically significant impacts on housing price in the region. Our empirical evidence proves that the Hansen index is more appropriate than the other in estimating housing price impacts.

• Environmental Engineering Research
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• v.23 no.1
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• pp.76-83
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• 2018

Spatial moment analysis has been performed on the concentration of the first species in a multispecies solute transport in porous media. Finite difference numerical technique was used in obtaining the solute concentration. A constant continuous source of contaminant was injected at the inlet of the domain. Results suggest that the decaying of solute mass increases as the magnitude of mean fluid velocity increases. The dispersion coefficient is highly time dependent under decaying of solutes with a complex behavior of mixing of solutes. The solute mobility and mixing varies non-linearly with time during its initial period, while the same ceases with higher decay rates of the first species much faster.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 1998.11a
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• pp.20-25
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• 1998

In order to support effective decision-making related to inter-sewage planning, this study proposes the spatial distribution method of inter-sewage treatement area using spatial analysis of GIS, Communication system of database, spatial interaction of Gravity model. Evalution Indexs are consist of economic, social/political and environmental condition value which are explained by the analysis of AHP algorithm ,based on opinion of related experts. Network module in Arc/Info is applied in order to find out minimum pipeline root in Miho river watershed, one of the sub-basin of Geum river basin. This value also is utilized for the construction of cost decay function in gravity model.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.12-12
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• 2010

By using scanning tunneling microscopy/spectroscopy (STM/S), we can make images of various physical properties in nanometer-scale spatial resolutions. Here, I demonstrate imaging of two electron-correlated subjects; screening and superconductivity by STM/S. The electrostatic potential around a charge is described with the Coulomb potential. When the charge is located in a metal, the potential is modified because of the free electrons in the host. The potential modification, called screening, is one of the fundamental phenomena in the condensed matter physics. Using low-temperature STM we have developed a method to measure electrostatic potential in high spatial and energy resolutions, and observed the potential around external charges screened by two-dimensional surface electronic states. Characteristic potential decay and the Friedel oscillation were clearly observed around the charges [1]. Superconductivity of nano-size materials, whose dimensions are comparable with the coherence length, is quite different from their bulk. We investigated superconductivity of ultra-thin Pb islands by directly measuring the superconducting gaps using STM. The obtained tunneling spectra exhibit a variation of zero bias conductance (ZBC) with a magnetic field, and spatial mappings of ZBC revealed the vortex formation [2]. Size dependence of the vortex formation will be discussed at the presentation.

• Korean Journal of Optics and Photonics
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• v.12 no.2
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• pp.77-82
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• 2001

Error characteristics of a mirror loss measurement system using an exponential decay method were studied, with the two samples having about 200-ppm-loss and 30-ppm-loss, respectively. In order to minimize the decay signal deviation from an exponential curve due to cavity length fluctuation, a data average method was tried. The data average method significantly improved the exponential curve fitting error of the decay signal, so that for a 6 decay signal data average the loss measurement error was reduced by about 2.4 times for the 200-ppm-loss mirror and 1.3 times for the 30-ppm-loss mirror compared with a single shot measurement. Day-to-day mirror loss repeatability error for the two samples was investigated. The repeatability error was measured to be about 5% for the 200-ppm-loss mirror and about 26.4% for the 30-ppm-loss mirror. Low decay signal average effect and high repeatability error in the low loss mirror measurement were explained with non-uniform spatial loss distribution of the sample and contamination from the environment, in addition to the error sources of the mirror loss measurement system itself. The influence of cavity length fluctuation and cavity length measurement error on the mirror loss measurement system performance was theoretically calculated. It confirmed that the requirement for the cavity length parameters was not so strict in the mirror loss measurement system of several ppm resolution. ution.

• Journal of the Korean Mathematical Society
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• v.53 no.1
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• pp.127-146
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• 2016

We consider a coupled system of Keller-Segel type equations and the incompressible Navier-Stokes equations in spatial dimension two. We show temporal decay estimates of solutions with small initial data and obtain their asymptotic profiles as time tends to infinity.