• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.12
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• pp.4476-4491
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• 2021

Video service providers tend to face user network problems in the process of transmitting video streams. They strive to provide user with superior video quality in a limited bitrate environment. It is necessary to accurately determine the target bitrate range of the video under different quality requirements. Recently, several schemes have been proposed to meet this requirement. However, they do not take the impact of visual influence into account. In this paper, we propose a new multi-category model to accurately predict the target bitrate range with target visual quality by machine learning. Firstly, a dataset is constructed to generate multi-category models by machine learning. The quality score ladders and the corresponding bitrate-interval categories are defined in the dataset. Secondly, several types of spatial-temporal features related to VMAF evaluation metrics and visual factors are extracted and processed statistically for classification. Finally, bitrate prediction models trained on the dataset by RandomForest classifier can be used to accurately predict the target bitrate of the input videos with target video quality. The classification prediction accuracy of the model reaches 0.705 and the encoded video which is compressed by the bitrate predicted by the model can achieve the target perceptual quality.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.87-90
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• 2002

Daylight responsive dimming system, which is always able to automatically maintain the target illuminance, is a energy strategic system. It is importance note that the photosensor depends how to be precisely indicated workplane illuminance at any location of indoor. Therefore, the purpose of this paper is to find out the optimum location and spatial characteristics of photosensor by considering the correlation for the correct calibration of workplane illuminance and photosensor signal.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.3-10
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• 2004

The earthquake-resistant structural systems have to ensure the sufficient stiffness and ductility for the stability. For those purposes, recently, the performance design concept to increase the degree of absorbed energy level of structures has been proposed. One practical way of the performance design in the spatial structures is to apply the isolation system to boundary parts of roof system and sub-structure to obtain the target performance. So, it is necessary to examine the characteristics of dynamic behavior of spatial structures governed by higher modes rather than lower modes different from the cases of high rise buildings. The objectives of this paper are to develop the equivalent lumped mass model to simplify the analytical processes and to investigate the dynamic behavior of roof system according to the mass and the stiffness of sub-structures as a fundamental study of performance design for the spatial structures.

• Journal of Environmental Impact Assessment
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• v.20 no.5
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• pp.697-703
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• 2011

The purpose of this study aims to preserve biodiversity in increasingly fragmented green patches for spatial analysis of planting on the eco-corridors and to optimize the target species, the location, width, cross section of the eco-corridors. It was suggested that eco-corridors should have to planned at early stages of road planning so that the number and locations of eco-corridors in advance. Ecological corridor is the facility to connect two habitats fragmented by road, dam, housing and industrial area. And, everyone agree that ecological corridor is important useful structural component that help animal movement in fragmented landscapes. However, ecological corridors have many problems of the recorded the size of corridor, planting species to nearby exiting vegetation species and structure. The most important facts that there are no consideration for location of animal migration and behavior using eco-corridors. This study was carried out to spatial analysis of eco-corridors location, satellite data and GIS were used to analyze for searching optimum location of the eco-corridors.

• Journal of Information Technology Services
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• v.18 no.1
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• pp.131-140
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• 2019

This study compares and analyzes the spatial distribution of people in two cities using location information in twitter data. The target cities were selected as Paris, a traditional tourist city, and Dubai, a tourist city that has recently attracted attention. The data was collected over 123 days in 2016 and 125 days in 2018. We compared the spatial distribution of two cities according to the two periods and residence status. In this study, we have found a hot place using a spatial statistical model called dart-shaped space division and estimated the urban area by reflecting the distribution of tweet population. And we visualized it as a CDF (cumulative distribution function) curve so that the distance between all the tweets' occurrence points and the city center point can be compared for different cities.

• Journal of agriculture & life science
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• v.44 no.5
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• pp.117-127
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• 2010

The purpose of this study is to analyze the temporal and spatial characteristics of water quality data of Nakdonggang watershed which is second largest watershed in South Korea. The correlation between the water quality items for rainy and non-rainy seasons were also analyzed for two TMDL sites which are Gumi and Namji. BOD data of two Total Maximum Daily Loads (TMDL) target sites were compared with TMDL criteria, 3-year arithmetic mean BOD concentration of the target sites should not exceed the target concentration for 2 consecutive years, to figure out current water quality status. Spatial analysis results showed that the correlation coefficient between Goryeong and Hyunpung was highest with the value of 0.978 followed by Hapcheon and Namji with the value of 0.874. The observed BOD data of Gumi station fluctuated around the TMDL criterion, 1.8mg/L while Namji station mostly exceed the criterion, 2.6mg/L. The criteria values for each target sites are defined by Ministry of Environment. The major factor of correlation coefficient was the distance between the stations. The correlation between the water quality items for non-rainy season showed no relation while the correlation between COD and SS was high followed by COD and TP for Gumi and Namji.

• Journal of Korea Multimedia Society
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• v.19 no.10
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• pp.1775-1781
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• 2016

Generally, in the underwater target recognition, feature vectors are extracted from the target signal utilizing spatial information according to target shape/material characteristics. In addition, various signal processing techniques have been studied to extract feature vectors which are less sensitive to the location of the receiver. In this paper, we synthesized active echo signals using 3-dimensional highlight distribution. Then, Fractional Fourier transform was applied to echo signals to extract signal features. For the performance verification, classification experiments were performed using backpropagation and probabilistic neural network classifiers based on single aspect and multi-aspect method. As a result, we obtained a better recognition result using proposed feature extraction and multi-aspect based method.

• Journal of Surface Science and Engineering
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• v.47 no.1
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• pp.53-56
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• 2014

I-V characteristics of a cylindrical target in an ECR plasma were studied for sheath spatial evolutions when the target was pulsed biased to a high negative potential. The magnetic field effects on sheath thickness and sheath boundary speed were investigated by comparison between the experimental results and the theoretical results using the Child-Langmuir sheath model. The results showed that the magnetic field suppressed electron motion away from the target so that sheath thickness and sheath boundary speed decreased.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.37-44
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• 2002

An echo signal in the active sonar using a high frequency is mainly formed of a specular reflection from the surface of an object along with several equivalent scatter inside, which are characterized by the spatial distribution of the highlights on the object. This thesis proposed a model in which the synthesized echo signal can be expressed as a distributed simulated target. The proposed model is obtained after composing a signal based on the movement of highlights relative to the aspect angle from the discontinuous point of an external hull with a strong reflection from a spheroid underwater target. Because the proposed algorithm includes a synthesis of the signals related to the highlight spacial distribution, it can be applied to all kinds of systems used at a short range, and similar results were obtained to the actual measured results of all reflected signals in previous literature referring to the irregular factor application of an envelope.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.666-673
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• 2022

The optimization of a transmission type bremsstrahlung conversion target was carried out with Monte Carlo code FLUKA for intense pulsed electron beams with electron energy of several hundred keV for maximum photon fluence. The photon emission intensity from electrons with energy ranging from 300 keV to 1 MeV on tungsten, tantalum and molybdenum targets was calculated with varied target thicknesses. The research revealed that higher target material element number and electron energy leads to increased photon fluence. For a certain target material, the target thickness with maximum photon emission fluence exhibits a linear relationship with the electron energy. With certain electron energy and target material, the thickness of the target plays a dominant role in increasing the transmission photon intensity, with small target thickness the photon flux is largely restricted by low energy loss of electrons for photon generation while thick targets may impose extra absorption for the generated photons. The spatial distribution of bremsstrahlung photon density was analyzed and the optimal target thicknesses for maximum bremsstrahlung photon fluence were derived versus electron energy on three target materials for a quick determination of optimal target design.