• Particle and aerosol research
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• 제10권1호
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• pp.9-17
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• 2014

Several studies have been carried out on the source contribution of the particulate Polycyclic Aromatic Hydrocarbons (PAHs) over Seoul by using the Chemical Mass Balance Model (CMB)(Lee and Kim, 2007; Kim et al., 2013). To confirm the validity of the modeling results, the modified model employing a photochemical loss rate along with varying residence times and the standard model that considers no loss were compared. It was found that by considering the photochemical loss rate, a better performance was obtained as compared to those obtained from the standard model in the CMB calculation. The modified model estimated higher contributions from coke oven, transportation, and biomass burning by 4 to 8%. However, the order of the relative importance of major sources was not changed, coke oven followed by transportation and biomass burning. Thus, it was concluded that the standard CMB model results are reliable for identifying the relative importance of major sources.

• The Journal of the Korea institute of electronic communication sciences
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• 제8권11호
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• pp.1633-1640
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• 2013

In this paper, noise parameters for high frequency modeling of dual-gate FET are extracted and analyzed. To extract thermal noise parameter of dual gate, noise characteristics are measured by changing input impedance of noise source using Tuner, and the influence of pad parasitic elements are subtracted using open and short dummy structure. Measured results indicated that the dual-gate FET is improved the noise figure by 0.2dB compared with conventional cascode structure FET at 5GHz, and it confirmed that the noise figure has dropped due to reduction of capacitances between the drain and source, gate and drain by simulation and analysis of small-signal parameters.

• Journal of the Korean Society of Environmental Restoration Technology
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• 제25권6호
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• pp.65-75
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• 2022

Urban flood management(UFM) strategy ought to consider the connections and interactions between existing and new infrastructures to manage stormwater and improve the capacity to treat water. It is also important to demonstrate strategies that can be implemented to reduce the flow at flooding sources and minimize flood risk at critical locations. Although the general theory of spatial impact is popular, modeling guidelines that can provide information for implementation in real-world plans are still lacking. Under such background, this study conducted a modeling research based on an actual target site to confirm the hypothesis that it is appropriate to install green infrastructure(GI) in the source area and to take structural protection measures in the impact area, as summarized in previous studies. The results of the study proved the hypothesis, but the results were different from the hypothesis depending on which hydrological performance indicators were targeted. This study will contribute to demonstrating the effectiveness of strategies that can be implemented to reduce the flow at flooding sources and minimize the risk of flooding in critical locations in terms of spatial planning and regeneration.

• Progress in Superconductivity
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• 제4권1호
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• pp.19-26
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• 2002

We have earlier developed a 40-channel SQUID system. An important figure of merit of a MEG system is the localization error, within which the underlying current source can be localized. With this system, we investigated the localization error in terms of the standard deviation of the coordinates of the ECDs and the systematic error due to inadequate modeling. To do this, we made localization of single current dipoles from tangential components of auditory evoked fields. Equivalent current dipoles (ECD) at N1m peak were estimated based on a locally fitted spherical conductor model. In addition, we made skull phantom and simulation measurements to investigate the contribution of various errors to the localization error. It was found that the background noise was the main source of the errors that could explain the observed standard deviation. Further, the amount of systematic error, when modeling the head with a spherical conductor, was much less than the standard deviation due to the background noise. We also demonstrated the performance of the system by measuring the evoked fields to grammatical violation in sentence comprehension.

• Geophysics and Geophysical Exploration
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• 제17권1호
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• pp.21-27
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• 2014

We analyzed response patterns of test field data acquired with new small loop electromagnetic (EM) system using three-dimensional (3D) electromagnetic modeling code. The size and shape of a conductor was adopted as experimental parameters for EM modeling to understand influencing factors of the response patterns due to a metallic object on the seafloor. Obtaining the responses for four models of difference sizes and shapes through 3D EM modeling, we confirmed that the shape of the object have a more critical factor on the response pattern than size. We also calculated "ppm" values with respect to different altitudes of the sensor and source frequencies. The modeling results show that the consistency of sensor altitude is important and imaginary part of ppm response is more sensitive than real part. We also visualized the contour map of the real and imaginary part of ppm value as a function of frequency and altitude so that we can estimate proper altitude for source frequency band of our survey system. The results of this paper are anticipated to give proper parameters in survey construction for seafloor massive sulfide deposit.

• The Journal of the Acoustical Society of Korea
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• 제20권3호
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• pp.76-82
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• 2001

Most fluid machines can be considered as periodic noise sources when operated under constant conditions, which allows for a frequency domain representation of the source and the associated acoustic field In the duct. In such a representation, the source is characterized by frequency-dependent values of both strength and impedance. Although knowledge of these values can be gained by either experimentation or by modeling, one-port acoustic characteristics of an in-duct source with high flow velocity, high temperature, and high sound level can be measured only by the multiload method using an overdetermined set of open pipes with different lengths as applied loads. However, the problem is that negative source resistances have been often measured. This paper reviews the possible causes of the problem, with reference to experimental and theoretical results, in an attempt to clarify the issue. A new interpretation is given for the violation of basic assumptions and the defect in the algorithm of multiload method. The major cause and mechanism of the problem is due to the violation of time invariance assumption of the source and the load impedance can seriously affect the final measured result of source impedance.

• Nuclear Engineering and Technology
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• 제20권2호
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• pp.120-131
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• 1988

A souce term model describes mathematically the source of radionuclides as they begin slow migration and decay in deep groundwater. Various source term models based on mass-transfer analysis and measurement-based source term models are reviewed. Ganerally, two processes are involved in leaching or dissolution: (1) chemical reactions and (2) mass transfer by diffusion. The chemical reaction controls the dissolution rates only during the early stage of exposure to groundwater. The exterior-field mass transfer may control the long term dissolution rates from the waste solid in a geologic repository. Mass-transfer analyses re3y on detailed and careful application of the governing equations that describe the mechanistic processes of transport of material between and within phases. If used correctly, source term models based on mass-transfer theory are valuable and necessary tools for developing reliable predictions.

• Water Engineering Research
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• 제7권1호
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• pp.1-8
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• 2006

Recently, the population growth and agricultural development are rapidly undergoing in the South-West Texas. The junction of three river basins such as Lavaca river basin, Colorado-Lavaca Coastal basin and Lavaca-Guadalupe Coastal basin, are interesting for non-point and point source pollutant modeling: Especially, the 2 basins are an intensively agricultural region (Colorado-Lavaca Coastal/Lavaca-Guadalupe Coastal basins) and several cities are rapidly extended. In case of the Lavaca river basin, there are many range land. Several habitat types wide-spread over three relatively larger basins and five wastewater discharge regions are located in there. There are different hazardous substances which have been released. Total nutrient loads are composed of land surface load and river load as Non-point source and discharge from wastewater facilities as point source. In 3 basins region, where point and non-point sources of poll Jtion may be a big concern, because increasing fertilizers and pesticides use and population cause. This project objective seeks to how to assess and control the accumulation of non-point and point source and discuss the main impacts of agriculture and environmental concern as non-point source with water quality related to pesticides, fertilizer, and nutrients and as point source with wasterwater discharge from cities. The GIS technique has been developed to aid in the point and non-point source analysis of impacts to natural resource within watershed. This project shows the losses in $kg/km^2/year$ of BOD (Biological Oxygen Demand), TN (Total Nitrogen) and TP (Total Phosphorus) in the runoff from the surface of 3 basins. In the next paper, sediment contamination will show how to evaluate in Estuarine habitats of these downstream.

• The Transactions of the Korean Institute of Electrical Engineers A
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• 제54권3호
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• pp.107-116
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• 2005

The paper addresses modeling and analysis of a grid-connected photovoltaic generation system (PV system). PSCAD/EMTDC, an industry standard simulation tool for studying the transient behavior of electric power system and apparatus, is used to conduct all aspects of model implementation and to carry out extensive simulation study. This paper is aimed at sharing with the PSCAD/EMTDC user community our user-defined model for PV system applications, which is not yet available as a standard model within PSCAD/EMTDC. An equivalent circuit model of a solar cell has been used for modeling solar array. A series of parameters required for array modeling have been estimated from general specification data of a solar module. A PWM voltage source inverter (VSI) and its current control scheme have been implemented. A maximum power point tracking (MPPT) technique is employed for drawing the maximum available energy from the PV array. Comprehensive simulation results are presented to examine PV array behaviors and PV system control performance in response to irradiation changes. In addition, dynamic responses of PV array and system to network fault conditions are simulated and analysed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.18-18
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• 1996

This paper reviews some of the most prominent and promising areas of chemical process control both in relations to batch and continuous processes. These areas include the modeling, optimization, control and monitoring of chemical processes and entire plants. Most of these areas explicitly utilize a model of the process. For this purpose the types of models used are examined in some detail. These types of models are categorized in knowledge-driven and datadriven classes. In the areas of modeling and optimization, attention is paid to batch reactors using the Tendency Modeling approach. These Tendency models consist of data- and knowledge-driven components and are often called Gray or Hybrid models. In the case of continuous processes, emphasis is placed in the closed-loop identification of a state space model and their use in Model Predictive Control nonlinear processes, such as the Fluidized Catalytic Cracking process. The effective monitoring of multivariate process is examined through the use of statistical charts obtained by the use of Principal Component Analysis (PMC). Static and dynamic charts account for the cross and auto-correlation of the substantial number of variables measured on-line. Centralized and de-centralized chart also aim in isolating the source of process disturbances so that they can be eliminated. Even though significant progress has been made during the last decade, the challenges for the next ten years are substantial. Present progress is strongly influenced by the economical benefits industry is deriving from the use of these advanced techniques. Future progress will be further catalyzed from the harmonious collaboration of University and Industrial researchers.