• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.759-764
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• 2004

This paper proposes a method that estimates MIMO channel characteristics analytically using a 3D ray tracing propagation model. We calculate the discrete spatial correlation between sub-channels by considering phase differences of paths, and using this, estimate the mean capacity upper bound of MIMO channel by Jensen's inequality. This analysis model is a deterministic model that do not approach stochastically through measurement nor approach statistically through Monte-Carlo simulations, so this model has high efficiency for time and cost. And based on the electromagnetic theory, this model may analyze quantitatively the parameters which can affect the channel capacity - antenna pattern, polarization mutual coupling, antenna structure and etc. This model may be used for the development of an optimal antenna structure for MIMO systems.

• Communications for Statistical Applications and Methods
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• v.13 no.3
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• pp.669-683
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• 2006

Model-based methods are generally used for small area estimation. Recently Shin and Lee (2003) suggested a method which used spatial correlations between areas for data set including some auxiliary variables. However in case of absence of auxiliary variables, Direct estimator is used. Even though direct estimator is unbiased, the large variance of the estimator restricts the use for small area estimation. In this paper, we suggest new estimators which take into account spatial correlation when auxiliary variables are not available. We compared Direct estimator and the newly suggested estimators using MSE, MAE and MB.

• Wind and Structures
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• v.28 no.2
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• pp.129-140
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• 2019

Accurately simulating the wind field of large-scale region, for instant urban areas, the locations of large span bridges, wind farms and so on, is very difficult, due to the complicated terrains or land surfaces. Currently, the regional wind field can be simulated through the combination of observation data and numerical model using observation-nudging in the Weather Research and Forecasting model (WRF). However, the main drawback of original observation-nudging method in WRF is the effects of observation on the surrounding field is fully mathematical express in terms of temporal and spatial, and it ignores the effects of terrain, wind direction and atmospheric circulation, while these are physically unreasonable for the turbulence. For these reasons, a spatial correlation-based observation-nudging method, which can take account the influence of complicated terrain, is proposed in the paper. The validation and comparation results show that proposed method can obtain more reasonable and accurate result than original observation-nudging method. Finally, the discussion of wind field along bridge span obtained from the simulation with spatial correlation-based observation-nudging method was carried out.

• Journal of the Korean Association of Geographic Information Studies
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• v.4 no.1
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• pp.57-66
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• 2001

This study used four theoretical models, such as two-point linear model, linear regression model, quadratic regression model and cubic regression model which are presented from The Ministry of Science and Technology, for extraction of urban surface temperature from Landsat TM band 6 image. Through correlation and regression analysis between result of four models and AWS(automatic weather station) observation data, this study could verify spatial distribution characteristic of urban surface temperature using GIS spatial analysis method. The result of analysis for surface temperature by landcover showed that the urban and the barren land belonged to the highest surface temperature class. And there was also -0.85 correlation in the result of correlation analysis between surface temperature and NDVI. In this result, the meteorological environmental characteristics wuld be regarded as one of the important factor in urban planning.

• Journal of Korea Water Resources Association
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• v.40 no.12
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• pp.943-956
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• 2007

Among various statistics, the spatial correlation function, that is "correlogram", is frequently used to evaluate or design the rain gauge network and to model the rainfall field. The spatial correlation structure of rainfall has the significant variation due to many factors. Thus, the variation of spatial correlation structure of rainfall causes serious problems when deciding the spatial correlation function of rainfall within the basin. In this study, the spatial rainfall structure was modeled using bivariate mixed distributions to derive monthly spatial correlograms, based on Gaussian and lognormal distributions. This study derived the correlograms using hourly data of 28 rain gauge stations in the Keum river basin. From the results, we concluded as following; (1) Among three cases (Case A, Case B, Case C) considered, the Case A(+,+) seems to be the most relevant as it is not distorted much by zero measurements. (2) The spatial correlograms based on the lognormal distribution, which is theoretically as well as practically adequate, is better than that based on the Gaussian distribution. (3) The spatial correlation in July exponentially decrease more obviously than those in other months. (4) The spatial correlograms should be derived considering the temporal resolution(hourly, daily, etc) of interest.

• Wind and Structures
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• v.8 no.2
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• pp.135-146
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• 2005

Divergent galloping-like motion of a dry inclined cable has been observed in a limited number of experimental studies, which, due to the uncertainties in its onset conditions, has induced serious concerns in the bridge stay cable design. A series of dynamic and static model wind tunnel tests have been carried out to confirm the existence of the phenomenon and clarify its excitation mechanism. The present paper focuses on exploring the spatial flow structure around an inclined cable. The pattern of resultant aerodynamic forces acting at different longitudinal locations of the model and the spatial correlation of the forces are examined. The results lead one step closer in revealing the physical nature of the phenomenon.

• Journal of information and communication convergence engineering
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• v.16 no.1
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• pp.38-42
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• 2018

In this paper, we consider measurement allocation problem in a spatially correlated sensor field. Our goal is to determine the probability of each sensor's being measured based on its contribution to the estimation reliability; it is desirable that a sensor improving the estimation reliability is measured more frequently. We consider a spatial correlation model of a sensor field reflecting transmission power limit, noise in measurement and transmission channel, and channel attenuation. Then the estimation reliability is defined distortion error between event source and its estimation at sink. Motivated by the correlation nature, we model the measurement allocation problem into a cooperative game, and then quantify each sensor's contribution using Shapley value. Against the intractability in the computation of exact Shapley value, we deploy a randomized method that enables to compute the approximate Shapley value within a reasonable time. Besides, we envisage a measurement scheduling achieving the balance between network lifetime and estimation reliability.

• Journal of the Regional Association of Architectural Institute of Korea
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• v.21 no.3
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• pp.11-21
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• 2019

The purpose of this study was to present an analysis model for finding the correlation between visibility and evacuation time as users move in the outpatient department of the general hospital. The spatial scope of the study was limited to the first floor and second floor which are used for the outpatient department. Traffic density in outpatient departments was surveyed on site. Based on the surveyed traffic density, the evacuation simulation model was established for calculating the escape route and evacuation time for an individual user. The traffic density of the outpatient department as per the evacuation time was also calculated. With using evacuation simulations, the flow of evacuees was calculated through the density of traffic over the time of evacuation. Visibility data were set in the simulation model for users' escape routes. A correlation analysis between the product of evacuation flow measure and visibility measure of the evacuation population and evacuation time was performed. The analysis result showed negative correlation within a specific distance range. This study presented an analysis model showing that the evacuation condition considering spatial visibility in the outpatient department of general hospital visibility was negatively related to the analyzed evacuation time at the design stage.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.16-19
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• 2000

We propose a deterministic vector channel simulation model satisfying not only rigorous temporal correlation but also arbitrary spatial correlation using the method of Doppler phase difference sampling. The model is more efficient than the conventional PN filtered Gaussian model with coloring process in evaluating the laboratory performance of mobile communication systems employing adaptive way antennas or space diversity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.788-794
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• 2005

In this paper, we focus on the potential of dual polarized antennas in mobile system. thus, this paper designs exact dual polarized channel with Spatial Channel Model (SCM) and investigates the performance for certain environment. Using proposed the channel model; we know estimates of the channel capacity as a function of cross polarization discrimination (XPD) and spatial fading correlation. It is important that the MIMO channel matrix consists of Kronecker product dividable spatial and polarized channel. Through the channel characteristics, we propose an algorithm for the adaptation of transmit antenna configuration to time varying propagation environments. The optimal active transmit antenna subset is determined with equal power allocated to the active transmit antennas, assuming no feedback information on types of the selected antennas. We first consider a heuristic decision strategy in which the optimal active transmit antenna subset and its system capacity are determined such that the transmission data rate is maximized among all possible types. This paper then proposes singular values decision procedure consisting of Kronecker product with spatial and polarize channel. This method of singular value decision, which the first channel environments is determined using singular values of spatial channel part which is made of environment parameters and distance between antennas. level of correlation. Then we will select antenna which have various polarization type. After spatial channel structure is decided, we contact polarization types which have considerable cases It is note that the proposed algorithms and analysis of dual polarized channel using SCM (Spatial Channel Model) optimize channel capacity and reduce the number of transmit antenna selection compare to heuristic method which has considerable 100 cases.