• Journal of Korean Society for Geospatial Information Science
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• v.4 no.2 s.8
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• pp.23-33
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• 1996

The conventional monitoring of water quality constrained by time and equipment produce neither complete nor synoptic geographic coverage of pollutant distribution, transport, and water quality. To circumvent these limitations in temporal and spatial measurements, the use of remote sensing is increasingly being involved in the lacustrine environmental research. Consequently, satellite remote sensing, with its synoptic coverage, is used to obtain the eutrophication-related water quality parameters in Daecheong reservoir in this study. The approach involved acquisition of water quality samples from boats of 15 sites on 20 June 1995 and 30 sites on 18 March 1996, simultaneous with Landsat-5 satellite overpass. Regression models have been developed between the water quality parameters and Landsat Thematic Mapper(TM) digital data. The best regression model was determined based on the correlation coefficient which was higher than 0.6. As a result, satellite remote sensing can provide meaningful information on water quality parameters. The regression models developed in this study show good relationship for transparency, turbidity, SS, and chlorophyll, but not for TN and TP because their spectral characteristics are not well defined.

• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.659-667
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• 2011

Wind tunnels tests have been evaluating wind load estimation by discussing the most important design elements in very tall buildings. Such tests have some uncertainties, however, with respect to the data of the reduced model and the calculated empirical values. In contrast, CFD analysis can simulate the actual scale and shorten the time of simulation. Nevertheless, the utilization of CFD analysis is negligible because of its low reliability. In this paper, the reliability of CFD analysis will be proven by comparing the results of a wind tunnel test and CFD analysis for the prototype models shown in previous studies. The effect of the turbulence intensity on the reliability is also presented.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.4
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• pp.437-444
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• 2009

A bi-directional, multi-step numerical integrator is developed to determine the GPS (Global Positioning System) orbit based on a dynamic approach, which shows micrometer-level accuracy at GPS altitude. The acceleration due to the planets other than the Moon and the Sun is so small that it is replaced by the empirical forces in the Solar Radiation Pressure (SRP) model. The satellite orbit parameters are estimated with the least-squares adjustment method using both the integrated orbit and the published IGS (International GNSS Service) precise orbit. For this estimation procedure, the integration should be applied to the partial derivatives of the acceleration with respect to the unknown parameters as well as the acceleration itself. The accuracy of the satellite orbit is evaluated by the RMS (Root Mean Squares error) of the residuals calculated from the estimated orbit parameters. The overall RMS of orbit error during March 2009 was 5.2 mm, and there are no specific patterns in the absolute orbit error depending on the satellite types and the directions of coordinate frame. The SRP model used in this study includes only the direct and once-per-revolution terms. Therefore there is errant behavior regarding twice-per-revolution, which needs further investigation.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.3
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• pp.36-41
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• 2010

An advanced form of Multistage Feature-based Classification Model(AMFCM), called AMFCM, is proposed in this paper. AMFCM like MFCM does not use the concatenated form of available feature vectors extracted from original data to classify each data, but uses only groups related to each feature vector to classify separately. The prpposed AMFCM improves the contribution rate used in MFCM and proposes a confusion table for each local classifier using a specific feature vector group. The confusion table for each local classifier contains accuracy information of each local classifier on each class of data. The proposed AMFCM is applied to the problem of music genre classification on a set of music data. The results demonstrate that the proposed AMFCM outperforms MFCM by 8% - 15% on average in terms of classification accuracy depending on the grouping algorithms used for local classifiers and the number of clusters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.352-359
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• 2001

We propose the row method that is able to consider the SAR compliance test from the very beginning step of developing the mobile phone. The reason this new method is plausible is that we adopt the certified FDTD for the reliability of calculation, utilizing 1 mm high resolution model that is to model the phantom and the mobile phone almost identically to the reality. In this paper we introduce the process that will apply the proposed method in order to reduce the SAR of the mobile phone that has been problematic in satisfying the SAR compliance test. It results in dropping in the SAR that we keep the mobile phone or its antenna while we use it. Therefore here we make a claim as fellows. When we develop the new mobile phone, we should use the computer simulation combining the CAD design and radiation pattern rather than make a prototype and then use the trial and error method. Moreover the former way leads us to boost up the developing efficiency and reduce the cost.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.1
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• pp.106-113
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• 1997

In this paper, we introduce the design method using CAE(Computer Aided Engineering) which is profitable in the compatibility and standardization of the developed product and in the reduction of construction time and price to develop and design a machine equipment. Particularly, we select the standard model to design ot develop from the large machinery to the super precision one, extract the peculiar characters of the model by the close analysis of the physical and technical part, can predict the previous result of experimental characteristics on objective dimensions through the analogical mathematical analysis, and can induce the design model demanded by user investigating optimal data in advance. We present the analogical algorithms and process method of design factors and restriction factors in the systematization design with computer. Then we analyze step functions for each systematization equipment and induce the process of technical data with actuator model.

• Convergence Security Journal
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• v.10 no.1
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• pp.41-48
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• 2010

Greedy protocols show good performance in Vehicular Ad-hoc Networks (VANETs) environment in general. But they make longer routes causing by surroundings or turn out routing failures in some cases when there are many traffic signals which generate empty streets temporary, or there is no merge roads after a road divide into two roads. When a node selects the next node simply using the distance to the destination node, the longer route is made by traditional greedy protocols in some cases and sometimes the route ends up routing failure. Most of traditional greedy protocols just take into account the distance to the destination to select a next node. Each node needs to consider not only the distance to the destination node but also the direction to the destination while routing a packet because of geographical environment. The proposed routing scheme considers both of the distance and the direction for forwarding packets to make a stable route. And the protocol can configure as the surrounding environment. We evaluate the performance of the protocol using two mobility models and network simulations. Most of network performances are improved rather than in compared with traditional greedy protocols.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.6-12
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• 2017

This paper deals with mathematical modeling of a 75-ton open-cycle Liquid Propellant Rocket Engine (LPRE) and the steady state simulation based on a nominal operating point. Each component of open-cycle LPRE may be classified into seven major categories using thermodynamics and dynamics characteristics. To simplify the simulation model of LPRE in this paper, we used four govern equations with assuming no heat transfer process. We confirmed the mathematical model of LPRE by using the error ratio and comparing the experiment data and simulation data in steady state, and checked the stability with the linearized model. Finally, we demonstrated the simulation model as compared to the transient response of experimental data.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.231-238
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• 2014

In the buildings, the systems of structures are influenced by the gravity load changes due to room alteration or construction stage. This paper proposes a system identification method establishing mass as well as stiffness to parameters in model updating process considering mass change in the buildings. In this proposed method, modified genetic algorithm, which is optimization technique, is applied to search those parameters while minimizing the difference of dynamic characteristics between measurement and FE model. To search more global solution, the proposed modified genetic algorithm searches in the wider search space. It is verified that the proposed method identifies the system of structure appropriately through the analytical study on a steel beam structure in the building. The comparison for performance of modified genetic algorithm and existing simple genetic algorithm is carried out. Furthermore, the existing model updating method neglecting mass change is performed to compare with the proposed method.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.37-44
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• 2002

A theoretical study of spray and combustion characteristics due to coaxial twin-fluid injection is conducted to investigate the effects of liquid jet property, droplet size, contact length and liquid jet velocity. Model is properly validated with measurements and shows good agreement. Prediction of jet contact length, droplet size, liquid jet velocity reflects genuine features of coaxial injection in physical and practical aspects. Both the jet contact length and tile droplet size are reduced in a linear manner with an increase of injector diameter. Cross sectional area of liquid intact core is reduced with augmented jet splitting rate, thus the jet is accelerated to maintain the mass continuity and with an assistant of momentum diffusion by burnt gas.