• Environmental Engineering Research
• /
• v.21 no.2
• /
• pp.171-179
• /
• 2016

This study analyzes guidelines to select optimum number of grids to represent behavior of a given water system appropriately. The EFDC model was chosen as a 3-D hydrodynamic and water quality model and salt was chosen as a surrogate variable of pollutant. The model is applied to an artificial canal that receives salt water from coastal area and fresh water from a river from respective gate according to previously developed gate operation rule. Grids are subdivided in vertical and horizontal (longitudinal) directions, respectively until no significant changes are found in salinity concentrations. The optimum grid size was determined by comparing errors in average salt concentrations between a test grid systems against the most complicated grid system. MSE (mean squared error) and MAE (mean absolute error) are used to compare errors. The CFL (Courant-Friedrichs-Lewy) number was used to determine the optimum number of grid systems for the study site though it can be used when explicit numerical method is applied only. This study suggests errors seem acceptable when both MSE and MAE are less than unity approximately.

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.3
• /
• pp.308-316
• /
• 2013

This paper proposes an observation model for a particle filter-based localization using a sonar grid map. The proposed model estimates a predicted observation by considering the properties of a sonar sensor which has a large angular uncertainty. The proposed model searches a grid which has the highest probability to reflect a sonar beam using the following procedures; (1) the reliable area of a single sonar data is determined using the footprint association model; (2) the detection probability of each grid cell in a sonar beam coverage in estimated. The proposed model was applied to the particle filter based localization, and was verified by experiments in indoor environments.

• Journal of Power Electronics
• /
• v.11 no.3
• /
• pp.350-359
• /
• 2011

This paper describes the operational analysis results of a DC micro-grid using a detailed model of distributed generation. A detailed model of wind power generation, photo-voltaic generation and fuel cell generation was implemented with an userdefined model created with PSCAD/EMTDC software and coded in C-language. The operational analysis was carried out using PSCAD/EMTDC software, in which the power circuit is implemented by a built-in model and the controller is modeled by an user-defined model that is also coded in C-language. Various simulation results confirm that a DC micro-grid can operate without any problems in both the grid-tied mode and in the islanded mode. The operational analysis results confirm that the DC micro-grid makes it feasible to provide power to the load stably. It can also be utilized to develop an actual system design.

• Computers and Concrete
• /
• v.27 no.5
• /
• pp.407-416
• /
• 2021

The checking stresses in the Chinese codes for reinforced concrete (RC) or prestressed concrete (PC) bridges are aimed for the thin-web beam, which cannot reflect the actual behavior of the modern structures. The incompleteness of the checking stresses could give rise to the deficiency in the design and calculation, and unable to reveal the reason of some common cracks in the structure. In this paper, the complete stress checklist for RC or PC girder bridges are listed, as well as the corresponding crack shapes. The expression of the complete checking stresses is proposed in details. Spatial Grid Model can reflect all the concerned stresses in the structure. Through the comparison of the calculation results from the spatial grid model and the solid model, it is seen that the spatial grid model can reflect load effects such as shear lag effect, thin-wall effect and local effect. The stresses obtained from the spatial grid model could help engineers to have a good understanding of the structural behavior. Meanwhile, the stress checklist provides the information for analyzing and solving the deficiency in the structure.

• Journal of computational fluids engineering
• /
• v.6 no.4
• /
• pp.15-25
• /
• 2001

Numerical prediction of the diffusion controlled transition in a turbine gas pass is important because it can change the local heat transfer rate over a turbine blade as much as three times. In this study, the gas flow over turbine blade is simplified to the flat plate boundary layer, and an adaptive grid scheme redistributing grid points within the computation domain is proposed with a great emphasis on the construction of the grid control function. The function is sensitized to the second invariant of the mean strain tensor, its spatial gradient, and the interaction of pressure gradient and flow deformation. The transition process is assumed to be described with a κ-ε turbulence model. An elliptic solver is employed to integrate governing equations. Numerical results show that the proposed adaptive grid scheme is very effective in obtaining grid independent numerical solution with a very low grid number. It is expected that present scheme is helpful in predicting actual flow within a turbine to improve computation efficiency.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.9
• /
• pp.1209-1216
• /
• 2013

Recently, there is a rising interest in smart grid operating system which manages various types of distributed generation, smart meters, and electric vehicles with power grid. Considering the features of smart grid environment, the interoperability should be one of the important factors to build smart grid environment successfully. To secure interoperability, smart grid operating system should conform to some standards in terms of the data representation and communication. CIM and OPC-UA are the international standards widely used in smart grid domain for enabling interoperability. They provide common information model and the unified architecture for communicating between each systems or applications. In this paper, we illustrate a smart grid operating system that we have developed to secure interoperability between not only applications but also numerous legacy systems(applications) by implementing CIM based information model and OPC-UA based communication interface services.

• Journal of the Korea Society for Simulation
• /
• v.15 no.3
• /
• pp.1-9
• /
• 2006

As an effective solution to resolve complex computing problems and to handle geographically dispersed data sets, grid computing has been noticed. Grid computing separates an application to several parts and executes on heterogeneous computing platforms simultaneously. The most important problem in grid computing environments is to manage grid resources and to schedule grid resources. This paper proposes a grid transaction network model that is applicable for resource management and scheduling in grid computing environment and presents a grid resource bidding algorithm for grid users and grid resource providers. Using DEVSJAVA modeling and simulation, this paper evaluates usefulness and efficiency of the proposed model.

• ETRI Journal
• /
• v.37 no.1
• /
• pp.197-202
• /
• 2015

A smart grid is a modernized electrical grid that uses information about the behaviors of suppliers and consumers in an automated fashion to improve the efficiency, reliability, economics, and sustainability of the production and distribution of electricity. In the operation of a smart grid, demand side management (DSM) plays an important role in allowing customers to make informed decisions regarding their energy consumption. In addition, it helps energy providers reduce peak load demand and reshapes the load profile. In this paper, we propose a new DSM scheduling scheme that makes use of the day-ahead pricing strategy. Based on the Rubinstein-Stahl bargaining model, our pricing strategy allows consumers to make informed decisions regarding their power consumption, while reducing the peak-to-average ratio. With a simulation study, it is demonstrated that the proposed scheme can increase the sustainability of a smart grid and reduce overall operational costs.

• Journal of the Korean Home Economics Association
• /
• v.44 no.1 s.215
• /
• pp.159-168
• /
• 2006

The purpose of this study was to analyse the types of expression of fashion magazine advertising using the Foote, Cone and Belding(FCB) GRID model. Consequently, this study examined the presentation of fashion magazine advertising. The fashion magazine advertising(771 cases in women's magazines, 120 cases in men's magazines) was classified according to the FCB GRID model. The fashion magazine advertising was categorized into high involvement-feeling goods(jewelry, accessories, bags, shoes, perfumes, men and women dresses, jeans, bathing suits etc.), low involvement-feeling goods(casual wears, imitation accessories etc.), high involvement-thinking goods(cosmetics, underwears, sports shoes etc.) and low involvement-thinking goods(hair goods, sports wears, undergarments etc.). A great of the fashion advertising consisted of photography and the emotional approach. Thinking goods placed emphasis on the functional value, whereas high involvement-feeling goods placed emphasis on the emotional value and low involvement-feeling goods on the fashionable value.

• The Journal of Korea Robotics Society
• /
• v.6 no.2
• /
• pp.189-196
• /
• 2011

This paper presents a method of topological modeling using only low-cost sonar sensors. The proposed method constructs a topological model by extracting sub-regions from the local grid map. The extracted sub-regions are considered as nodes in the topological model, and the corresponding edges are generated according to the connectivity between two sub-regions. A grid confidence for each occupied grid is evaluated to obtain reliable regions in the local grid map by filtering out noisy data. Moreover, a convexity measure is used to extract sub-regions automatically. Through these processes, the topological model is constructed without predefining the number of sub-regions in advance and the proposed method guarantees the convexity of extracted sub-regions. Unlike previous topological modeling methods which are appropriate to the corridor-like environment, the proposed method can give a reliable topological modeling in a home environment even under the noisy sonar data. The performance of the proposed method is verified by experimental results in a real home environment.