• The Korean Journal of Applied Statistics
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• v.37 no.1
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• pp.1-12
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• 2024

In many real-world data, multiple response variables are often dependent on the same set of explanatory variables. In particular, if several response variables are correlated with each other, simultaneous estimation considering the correlation between response variables might be more effective way than individual analysis by each response variable. In this multivariate regression analysis, least distance estimator (LDE) can estimate the regression coefficients simultaneously to minimize the distance between each training data and the estimates in a multidimensional Euclidean space. It provides a robustness for the outliers as well. In this paper, we examine the least distance estimation method in multivariate linear regression analysis, and furthermore, we present the penalized least distance estimator (PLDE) for efficient variable selection. The LDE technique applied with the adaptive group LASSO penalty term (AGLDE) is proposed in this study which can reflect the correlation between response variables in the model and can efficiently select variables according to the importance of explanatory variables. The validity of the proposed method was confirmed through simulations and real data analysis.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.636-645
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• 2012

This study introduces an information granular-based fuzzy radial basis function neural networks (FRBFNN) based on multiobjective optimization and weighted least square (WLS). An improved multiobjective space search algorithm (IMSSA) is proposed to optimize the FRBFNN. In the design of FRBFNN, the premise part of the rules is constructed with the aid of Fuzzy C-Means (FCM) clustering while the consequent part of the fuzzy rules is developed by using four types of polynomials, namely constant, linear, quadratic, and modified quadratic. Information granulation realized with C-Means clustering helps determine the initial values of the apex parameters of the membership function of the fuzzy neural network. To enhance the flexibility of neural network, we use the WLS learning to estimate the coefficients of the polynomials. In comparison with ordinary least square commonly used in the design of fuzzy radial basis function neural networks, WLS could come with a different type of the local model in each rule when dealing with the FRBFNN. Since the performance of the FRBFNN model is directly affected by some parameters such as e.g., the fuzzification coefficient used in the FCM, the number of rules and the orders of the polynomials present in the consequent parts of the rules, we carry out both structural as well as parametric optimization of the network. The proposed IMSSA that aims at the simultaneous minimization of complexity and the maximization of accuracy is exploited here to optimize the parameters of the model. Experimental results illustrate that the proposed neural network leads to better performance in comparison with some existing neurofuzzy models encountered in the literature.

• Spatial Information Research
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• v.18 no.5
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• pp.133-142
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• 2010

Many pedestrian or fire evacuation models have been studied last decades for modeling evacuation behaviors or analysing building structures under emergency situations. However, currently developed models do not consider the differences of visibility of pedestrians by obstacles such as furniture, wall, etc. The visibility of pedestrians is considered one of the important factors that affect the evacuation behavior, leading to making simulation results more realistic. In order to incorporate pedestrian's visibility into evacuation simulation, we should be able to give different walking speeds according to differences of visibility. We improved the existing floor field model based on cellular automata in order to implement the visibility. Using the space syntax theory, we showed how we split the indoor spaces depending on the different visibilities created by different levels of structural depths. Then, we improved the algorithm such that pedestrians have different speeds instead of simultaneous movement to other cells. Also, in order for developing a real time simulation system integrated w ith indoor sensors later, we present a process to build a 3D simulator using a spatial DBMS. The proposed algorithm is tested using a campus building.

• Journal of Environmental Science International
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• v.8 no.3
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• pp.299-307
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• 1999

In order to fast predict the wind-driven current in a small bay, a convolution method in which the wind-driven current can be generated only with the local wind is developed and applied in the idealized bay and the idealized Sachon Bay. The accuracy of the convlution method is assessed through a series of the numerical experiements carried out in the jidealized bay and the idealized Sachon Bay. The optimum response function for the convolution method is obtained by minimizing the root man square (rms) difference between the current given by the numerical model and the current given by the convolution method. The north-south component of the response function shows simultaneous fluctuations in the wind and wind-driven current at marginal region while it shows "sea-saw" fluctuations (in which the wind and wind-driven current have opposite direction) at the central region in the idealized Sachon Bay. The present wind is strong enough to influence on the wind-driven current especially in the idealized Sachon Bay. The spatial average of the rms ratio defined as the ratio of the rms error to the rms speed is 0.05 in the idealized bay and 0.26 in the idealized Sachon Bay. The recover rate of kinetic energy(rrke) is 99% in the idealized bay and 94% in the idealized Sachon Bay. Thus, the predicted wind-driven current by the convolution model is in a good agreement with the computed one by the numerical model in the idealized bay and the idealized Sachon Bay.achon Bay.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.2
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• pp.190-201
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• 2010

Fine particulate matter < $1.8{\mu}m$ was collected as a slurry using the Semicontinuous Elements in Aerosol Sampler with time resolution of 30-min between May 23 and 27, 2002 at the Sydney Supersite, Florida, USA. Concentrations of 11 elements, i.e., Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn, in the collected slurry samples were determined off-line by simultaneous multi-element graphite furnace atomic absorption spectrometry. Temporal profiles of $SO_2$ and elemental concentrations combined with meteorological parameters such as wind direction and wind speed indicate that some transient events in their concentrations are highly correlated with the periods when the plume from an animal feed supplement processing facility influenced the Sydney sampling site. The peaking concentrations of the elemental species during the transient events varied clearly as the plume intensity varied, but the relative concentrations for As, Cr, Pb, and Zn with respect to Cd showed almost consistent values. During the transient events, metal concentrations increased by factors of >10~100 due to the influence of consistent plumes from an individual stationary source. Also the multi-variate air dispersion receptor model, which was previously developed by Park et al. (2005), was applied to ambient $SO_2$ and 8 elements (Al, As, Cd, Cr, Cu, Fe, Pb, and Zn) measurements between 20:00 May 23 and 09:30 May 24 when winds blew from between 70 and $85^{\circ}$, in which animal feed processing plant is situated, to determine emission and ambient source contributions rates of $SO_2$ and elements from one animal feed processing plant. Agreement between observed and predicted $SO_2$ concentrations was excellent (R of 0.99; and their ratio, $1.09{\pm}0.35$) when one emission source was used in the model. Average ratios of observed and predicted concentrations for As, Cd, Cr, Pb, and Zn varied from $0.83{\pm}0.26$ for Pb to $1.12{\pm}0.53$ for Cd.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.5
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• pp.535-541
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• 2011

A debris flow is caused by torrential rain in mountainous regions and carries mixture of fragmental matter from slope failure, deposit soils from a valley floor and a large amount of water. It seriously damages facilities, houses, and human lives in its path. We tried to apply debris flow behavior estimation model developed in foreign country to domestic case. The study area is Inje-county, Gangwon-do and aerial photos and GPS surveying were used to collect information of starting and end point of the landslide and debris flow. The analysis showed that L/H for forecasting the travel distances of debris flows has the mean of 4.93 and standard deviation of 0.98. This model tended to overestimate the scale and extent of debris flows. In Inje-county's case, a debris flow is caused by multiple simultaneous small-scale landslide. This is quite different from the foreign cases in which a large-scale landslide cause a large-scale debris flow. Thus, an empirical model suitable for domestic conditions needs to be developed.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.23
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• pp.3-38
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• 2004

On-line game business has emerged as the most lucrative entertainment industry, with over 4 million players in China, with more than 45% of the market dominated by Korean on-line games. While the interactive entertainment market continues to expand, with many new Korean on-line game publishers entering the market, relatively little is known about which factors influence online game players' behavioral intentions (i.e., intention to play, brand-identity, word of mouth, flow, etc.) in this area. It appears that in this extremely attractive and growing services segment, academics, as well as practitioners, would benefit from investigating the relationships among the players' intention to play, social norms, word of mouth, flow, and the impacts of several other key game-related constructs. A conceptual framework is proposed and a simultaneous equation model is developed. This paper develops the exploratory LISREL model for identifying the factors affecting the players' intention to play for on-line games. Based on data collected from on-line questionnaire survey in China, the validity of the model has been tested and interesting conclusions have been developed concerning the relationships between the game-related constructs. It is hoped that this result might provide the useful guidelines for developing the successful on-line game contents. With better understanding of the players' behavioral intentions, Korean on-line game developers should be able to penetrate the China market with sustainable advantage over their competition.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.86-92
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• 2006

The full-waveform inversion algorithm using normalised seismic wavefields can avoid potential inversion errors due to source estimation required in conventional full-waveform inversion methods. In this paper, we have modified the inversion scheme to install a weighted smoothness constraint for better resolution, and to implement a staged approach using normalised wavefields in order of increasing frequency instead of inverting all frequency components simultaneously. The newly developed scheme is verified by using a simple two-dimensional fault model. One of the most significant improvements is based on introducing weights in model parameters, which can be derived from integrated sensitivities. The model-parameter weighting matrix is effective in selectively relaxing the smoothness constraint and in reducing artefacts in the reconstructed image. Simultaneous multiple-frequency inversion can almost be replicated by multiple single-frequency inversions. In particular, consecutively ordered single-frequency inversion, in which lower frequencies are used first, is useful for computation efficiency.

• Progress in Medical Physics
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• v.30 no.4
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• pp.94-103
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• 2019

Purpose: To evaluate the clinical feasibility of knowledge-based planning (KBP) for volumetric-modulated arc radiotherapy (VMAT) in spine stereotactic body radiotherapy (SBRT). Methods: Forty-eight VMAT plans for spine SBRT was studied. Two planning target volumes (PTVs) were defined for simultaneous integrated boost: PTV for boost (PTV-B: 27 Gy/3fractions) and PTV elective (PTV-E: 24 Gy/3fractions). The expert VMAT plans were manually generated by experienced planners. Twenty-six plans were used to train the KBP model using Varian RapidPlan. With the trained KBP model each KBP plan was automatically generated by an individual with little experience and compared with the expert plan (closed-loop validation). Twenty-two plans that had not been used for KBP model training were also compared with the KBP results (open-loop validation). Results: Although the minimal dose of PTV-B and PTV-E was lower and the maximal dose was higher than those of the expert plan, the difference was no larger than 0.7 Gy. In the closed-loop validation, D_1.2cc, D_0.35cc, and D_mean of the spinal cord was decreased by 0.9 Gy, 0.6 Gy, and 0.9 Gy, respectively, in the KBP plans (P<0.05). In the open-loop validation, only D_mean of the spinal cord was significantly decreased, by 0.5 Gy (P<0.05). Conclusions: The dose coverage and uniformity for PTV was slightly worse in the KBP for spine SBRT while the dose to the spinal cord was reduced, but the differences were small. Thus, inexperienced planners could easily generate a clinically feasible plan for spine SBRT by using KBP.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.705-712
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• 2000

The fluid generally flows through fractures in crystalline rocks where most of underground storage facilities are constructed because of their low hydraulic conductivities. The fractured rock is better to be conceptualized with a discrete fracture concept, rather continuum approach. In the aspect of fluid flow in underground, the simultaneous flow of groundwater and gas should be considered in the cases of generation and leakage of gas in nuclear waste disposal facilities, air sparging process and soil vapor extraction for eliminating contaminants in soil or rock pore, and pneumatic fracturing for the improvement of permeability of rock mass. For the purpose of appropriate analysis of groundwater-gas flow, this study presents an unsteady-state multi-phase FEM fracture network simulator. Numerical simulation has been also conducted to investigate the hydraulic head distribution and air tightness around Ulsan LPG storage cavern. The recorded hydraulic head at the observation well Y was -5 to -10 m. From the results obtained by the developed model, it shows that the discrete fracture model yielded hydraulic head of -10 m, whereas great discrepancy with the field data was observed in the case of equivalent continuum modeling. The air tightness of individual fractures around cavern was examined according to two different operating pressures and as a result, only several numbers of fractures neighboring the cavern did not satisfy the criteria of air tightness at 882 kPa of cavern pressure. In the meantime, when operating pressure is 710.5 kPa, the most areas did not satisfy air tightness criteria. Finally, in the case of gas leaking from cavern to the surrounding rocks, the resulted hydraulic head and flowing pattern was changed and, therefore, gas was leaked out from the cavern ceiling and groundwater was flowed into the cavern through the walls.