• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.12-19
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• 2006

Micro-source units having power ratings in thousands of watts can provide power quality with higher reliability and efficiency than the conventional large scale units. This paper develops switching level model of micro-source and studies the characteristics of the micro-grid consisting of multiple micro-sources and interfaced with electric power system. The developed model adopts the space vector PWM to fully utilize the capacity of inverter. The interaction of the grid connected micro-sources and the characteristics of the control system parameters are investigated. Micro-sources and micro-grid are implemented using PSCAD/EMTDC. Simulation results show that the proposed model is efficient for studying micro-grid system.

• Steel and Composite Structures
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• v.33 no.4
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• pp.537-550
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• 2019

Korea and Japan have done a lot of research on composite girders with corrugated steel webs and built many bridges with corrugated steel webs due to the significant advantages of this type of bridges. Considering the demanding on the calculation method of such types of bridges and lack of relevant reinforcement design method, this paper proposes the spatial grid analysis theory and tensile stress region method. First, the accuracy and applicability of spatial grid model in analyzing composite girders with corrugated steel webs was validated by the comparison with models using shell and solid elements. Then, in a real engineering practice, the reinforcement designs from tensile stress region method based on spatial grid model, design empirical method and specification method are compared. The results show that the tensile stress region reinforcement design method can realize the inplane and out-of-plane reinforcement design in the top and bottom slabs in bridges with corrugated steel webs. The economy and precision of reinforcement design using the tensile stress region method is emphasized. Therefore, the tensile stress region reinforcement design method based on the spatial grid model can provide a new direction for the refined design of composite box girder with corrugated steel webs.

• Journal of Korea Multimedia Society
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• v.22 no.8
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• pp.913-922
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• 2019

The Internet of Things (IoT) envisions smart objects collecting and sharing data at a massive scale via the Internet. One challenging issue is how to disseminate data to relevant data consuming objects efficiently. In such a massive IoT network, Mission critical data dissemination imposes constraints on the message transfer delay between objects. Due to the low power and communication range of IoT objects, data is relayed over multi-hops before arriving at the destination. In this paper, we propose a quorum-based adaptive dissemination algorithm (QADA) for the critical data in the monitoring-based applications of massive IoTs. To design QADA, we first design a new stepped-triangular grid structures (sT-grid) that support data dissemination, then construct a triangular grid overlay in the fog layer on the lower IoT layer and propose the data dissemination algorithm of the publish/subscribe model that adaptively uses triangle grid (T-grid) and sT-grid quorums depending on the mission critical in the overlay constructed to disseminate the critical data, and evaluate its performance as an analytical model.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.210-217
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• 2011

Recently, research on evaluating thermal comfort by using CFD has been vigorously active. This research evaluates not only distribution of temperature and air flow analysing but also thermal comfort in indoor space by applying human model. But research of human model's shape, Grid characteristic and turbulence model has not yet been studied. In this paper, human model's shape, physical characteristic of variable Grid, and change of turbulence model has been studies by CFD. In this study. FLUENT is used for analysis and PMV(predicted Mean Vote), PPD(Predicted Percentage Dissatisfied) and EHT(Equivalent Homogeneous Temperature} are used for evaluation and comparison of thermal comfort. As a result, it shows that shape of CSP and lattice features does not affect on global flow field or evaluation on PMV, PPD. However, it demonstrates more precise result from evaluation of thermal comfort by equivalent temperature when it used detailed human model considering prism grid.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1084-1093
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• 2010

Large eddy simulation of turbulent premixed flame stabilized by the bluff body is performed by using sub-grid scale combustion model based on the G-equation describing the flame front propagation. The basic idea of LES modeling is to evaluate the filtered-front speed, which should be enhanced in the grid scale by the scale fluctuations. The dynamic subgrid scale models newly introduced into the G-equation are validated by the premixed combustion flow behind the triangle flame holder. The calculated results can predict the velocity and temperature of the combustion flow in good agreement with the experiment data.

• Water Engineering Research
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• v.2 no.1
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• pp.49-61
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• 2001

A grid-based KIneMatic wave soil-water EROsion and deposition Model(KIMEROM) that predicts temporal variation and spatial distribution of sediment transport in a watershed was developed. This model uses ASCII-formatted map data supported from the regular gridded map of GRASS (U.S. Army CERL, 1993)-GIS(Geographic Information Systems), and generates the distributed results by ASCII-formatted map data. For hydrologic process, the kinematic wave equation and Darcy equation were used to simulated surface and subsurface flow, respectively (Kim, 1998; Kim et al., 1998). For soil erosion process, the physically-based soil erosion concept by Rose and Hairsine (1988) was used to simulate soil-water erosion and deposition. The model adopts single overland flowpath algorithm and simulates surface and subsurface water depth, and sediment concentration at each grid element for a given time increment. The model was tested to a 162.3 $\textrm{km}^2$ watershed located in the tideland reclaimed ares of South Korea. After the hydrologic calibration for two storm events in 1999, the results of sediment transport were presented for the same storm events. The results of temporal variation and spatial distribution of overland flow and sediment areas are shown using GRASS.

• Journal of Information Processing Systems
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• v.19 no.2
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• pp.258-266
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• 2023

Aiming at the problems of poor customer satisfaction and poor accuracy of customer classification, this paper proposes a customer classification model based on speech recognition. First, this paper analyzes the temporal data characteristics of customer demand data, identifies the influencing factors of customer demand behavior, and determines the process of feature extraction of customer voice signals. Then, the emotional association rules of customer demands are designed, and the classification model of customer demands is constructed through cluster analysis. Next, the Euclidean distance method is used to preprocess customer behavior data. The fuzzy clustering characteristics of customer demands are obtained by the fuzzy clustering method. Finally, on the basis of naive Bayesian algorithm, a customer demand classification model based on speech recognition is completed. Experimental results show that the proposed method improves the accuracy of the customer demand classification to more than 80%, and improves customer satisfaction to more than 90%. It solves the problems of poor customer satisfaction and low customer classification accuracy of the existing classification methods, which have practical application value.

• 기술발표회
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• s.2006
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• pp.162-171
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• 2006

Segmental Grid Retaining Wall is one of the segmental grid retaining walls using headers and stretchers to establish the framework of the wall In this method, grids formed by the intersection of headers and stretchers are generally filled with the gravel to maintain the weight of the wall Therefore, the construction can be carried out with higher speed and much economically when compared with the concrete retaining wall Furthermore, it has high drain capacity, and environmentally friendly aspects also have been pointed out because the possibility of the planting at the front of the wall However, in the segmental grid retaining wall method, the relative movement between the individual headers and stretchers was generally recognized, and stress redistribution in the gravel filling was also observed when subjected to the external loading and self-weight of filling Therefore, it has been thought that the distribution of the earth pressure in the segmental grid retaining wall system differ from that of the concrete retaining wall In this study, the surcharge tests using the scaled model segmental grid retaining wall was carried out to observe the distribution of the earth pressure in the segmental grid retaining wall The earth pressure was measured in the six specified height of wall, and the distribution of the pressure was analyzed. Furthermore, the earth pressure by computation or by the test using the concrete retaining wall was also considered to make comparison

• Journal of the Korea Society of Computer and Information
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• v.14 no.12
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• pp.1-8
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• 2009

Grid services offer SSO(single sign-on) mechanism using GSI(grid security infrastructure) based on X.509. However. portal applications in web environment use ID and password model for single sign-on. Grid portals means a system which provides grid services by integrating portlet contents on single web interface. In existing research such as GAMA and PURSE, SSO for a whole grid portal is figured out in the way that user is authenticated by ID and password in front and call grid service via GSI at back-end. Other types of web applications outside of portlet framework cannot unfortunately access grid service in SSO way in the existing researches, because the SSO mechanism is developed for portlet framework only. In this paper, we suggest a SSO mechanism based on ID and password model, which forwards authentication information and a GSI token for grid access among portlets and grid-enabled web applications. This mechanism is applied to MGrid for SSO, which consists of applications of java web start, applet, servlet, and etc. as also as portlets.

• Steel and Composite Structures
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• v.24 no.5
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• pp.549-559
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• 2017

As few multi-tower single-box multi-cell cable-stayed bridges with corrugated steel webs have been built, analysis is mostly achieved by combining single-girder model, beam grillage model and solid model in support of the design. However, such analysis methods usually suffer from major limitations in terms of the engineering applications: single-girder model fails to account for spatial effect such as shear lag effect of the box girder and the relevant effective girder width and eccentric load coefficient; owing to the approximation in the principle equivalence, the plane grillage model cannot accurately capture shear stress distribution and local stress state in both top and bottom flange of composite box girder; and solid model is difficult to be practically combined with the overall calculation. The usual effective width method fails to provide a uniform and accurate "effective length" (and the codes fail to provide a unified design approach at those circumstance) considering different shear lag effects resulting from dead load, prestress and cable tension in the construction. Therefore, a novel spatial grid model has been developed to account for shear lag effect. The theoretical principle of the proposed spatial grid model has been elaborated along with the relevant illustrations of modeling parameters of composite box girder with corrugated steel webs. Then typical transverse and longitudinal shear lag coefficient distribution pattern at the side-span and mid-span key cross sections have been analyzed and summarized to provide reference for similar bridges. The effectiveness and accuracy of spatial grid analysis methods has been finally validated through a practical cable-stayed bridge.