• Journal of the Korea Society for Simulation
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• v.6 no.1
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• pp.15-24
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• 1997

VRML (Virtual Reality Modeling Language) is an Web-based standard for modeling 3D spaces and provides applications with 3D interactive interfaces. With its recent upgrade, it supports events, routes, scripts, and other behavior modeling constructs. This paper approaches VRML as a simulation modeling language. This approach promotes the sharing and distribution of simulation results and demonstration among distributed users as well as efficient modeling of systems through the direct mapping of 3D objects and behaviors. This paper analyzes the behavior modeling constructs of VRML, presents effective modeling alternatives through the modeling of a simple material processing system, and discusses the upgrade direction of VRML as a foundation for distributed interactive simulation system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.87-94
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• 2017

Reliability analysis(RA) and Reliability-based design optimization(RBDO) require statistical modeling of input random variables, which is parametrically or nonparametrically determined based on experimental data. For the parametric method, goodness-of-fit (GOF) test and model selection method are widely used, and a sequential statistical modeling method combining the merits of the two methods has been recently proposed. Kernel density estimation(KDE) is often used as a nonparametric method, and it well describes a distribution function when the number of data is small or a density function has multimodal distribution. Although accurate statistical models are needed to obtain accurate RA and RBDO results, accurate statistical modeling is difficult when the number of data is small. In this study, the accuracy of two statistical modeling methods, SSM and KDE, were compared according to the number of data. Through numerical examples, the RA results using the input models modeled by two methods were compared, and appropriate modeling method was proposed according to the number of data.

• Economic and Environmental Geology
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• v.48 no.4
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• pp.313-324
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• 2015

This study constructed a 3D geological model for Uggi Nuur Fe-Mn mineralization zone in Mongolia, and the 3D geological distribution is cross-analyzed with magnetic anomaly distribution to figure out relationship between ore zone and subsurface geology. As a result of 4 step 3D modeling procedures including geological cross section, surface modeling, foliation modeling and solid modeling, the geology of the both study area is bordered by faults in NW direction with Munguntessj formation being located in the west side of the fault while Yashill formation is located on the other side of the fault. Moreover, the strike direction of foliation in the both formation shows same directional pattern with the NW faults. The magnetic anomaly distribution reveals that higher anomaly values are concentrated to near the ground surface. The analyses of 3 dimensional distribution between subsurface geology and magnetic anomaly indicates that higher anomaly is mainly distributed over the Munguntessj formation as a elongated lens bodies whereas the magnetic anomaly is evenly found in the both of Munguntessj formation and Yashill formation in the study area 2. It infers that volcanic activities associated mineralization occurred during silurian period, and the mineralized zone is thought to be realigned along the geological structures caused by later stage tectonic activities.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.156-168
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• 2013

Drilling expedition #1 in 2007 and drilling expedition #2 in 2010 were performed for gas hydrate resources evaluation and optimal site selection of pilot test in Ulleung basin, East Sea, Korea. This study presents to build the 3D spatial distribution models using the estimated sedimentary facies, porosity, and gas hydrate saturation derived by well logs and core analysis data from UBGH1-4, UBGH1-9, UBGH1-10, UBGH1-14, UBGH2-2-1, UBGH2-2-2, UBGH2-6, UBGH2-9, UBGH2-10 and UBGH2-11. The objective of 3D spatial distribution modeling is to build a geological representation of the gas hydrate-bearing sediment that honors the heterogeneity in 3D grid scale. The facies modeling is populating sedimentary facies into a geological grid using sequential indicator simulation. The porosity and gas hydrate saturation modeling used sequential Gaussian simulation to populate properties stochastically into grid cells.

• Journal of Gifted/Talented Education
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• v.22 no.3
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• pp.503-525
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• 2012

This study compared levels of mathematically talented students' statistical thinking with those of non-talented students in statistical modeling and sampling distribution understanding. t tests were conducted to test for statistically significant differences between mathematically gifted students and non-gifted students. In case of statistical modeling, for both of elementary and middle school graders, the t tests show that there is a statistically significant difference between mathematically gifted students and non-gifted students. Table of frequencies of each level, however, shows that levels of mathematically gifted students' thinking were not distributed at the high levels but were overlapped with those of non-gifted students. A similar tendency is also present in sampling distribution understanding. These results are thought-provoking results in statistics instruction for mathematically talented students.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.117-120
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• 2007

This study investigated the spray modeling of the pressure-swirl atomizer installed in liquid rocket engine and the effect of drop distribution function especially. The $X^2$, originally implemented to KIVA, Rosin-Rammler and modified Rosin-Rammler distribution functions were investigated theoretically and compared to each other. Also, they were applied to pressure-swirl atomizer similar to the injector installed in liquid rocket engine to evaluate the feasibility for LRE injector. Among the distribution functions, original Rosin-Rammler distribution function was the most compatible with predicting the spray characteristics of pressure-swirl atomizer installed in liquid rocket engine.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.29-36
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• 2013

This paper deals with the analysis of the customer voltage characteristic in distribution system interconnected with large scale PV system. There would be many power quality issues which are caused by reverse power flow of PV system interconnected with distribution system. In order to analyze the effect of PV system on the customer voltage, detailed modeling method of distribution system and modified modelling method of PV system are proposed using PSCAD/EMTDC in this paper. So far, less than dozens KW of PV system can be simulated with the existing modelling method. Therefore, a new modeling method which can simulate the large scale PV system is proposed by considering the relationship equation on the phase and voltage in the current control algorithm. From the simulation result of proposed modelling method, it is confirmed that an optimal operation method in distribution system is suggested by analyzing the effect of PV system on customer voltage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1355-1363
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• 2015

In order to maintain customer voltage within allowable limit($220{\pm}13V$), tap operation of SVR(step voltage regulator) installed in primary feeder could be carried out according to the scheduled delay time(30 sec) of SVR. However, the compensation of BESS(battery energy storage system) is being required because the customer voltages during the delay time of SVR have a difficultly to maintain within allowable limit when PV system is interconnected with primary feeder. Therefore, this paper presents modeling of SVR to regulate voltage with the LDC(line drop compensation) method and modeling of BESS to control active and reactive power bi-directionally. And also, this paper proposes the coordination control modeling between BESS and SVR in order to overcome voltage problems in distribution system. From the simulation results based on the modeling with the PSCAD/EMTDC, it is confirmed that proposed modeling is practical tool for voltage regulation analysis in distribution system.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.441-447
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• 2001

Ultrasonic wave generation and propagation were modeled to simulate an ultrasonic test. A ray model was used for the modeling. Actual sound pressure distribution of the incident wave from an angle probe was analyzed using an ultrasonic visualization method to incorporate the actual sound pressure distribution in the model. In this method, the sound pressure was expressed by the density of rays and the reflection coefficient of ultrasonic beams. Reflection and mode conversion of rays were computed by the Snells law. Simulation programs for the problem of ultrasonic testing of a butt joint are built using this ray modeling. Simulation results for ultrasonic wave scattering from a defect and A-scan display in ultrasonic testing agreed with the actual experiment results.

• Water Engineering Research
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• v.2 no.3
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• pp.161-169
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• 2001

Present study deals with the development of a numerical model for the estimation of net annual recharge by coupling the Galerkin's finite element flow simulationl model with the Gauss-Newton-Marquardt optimization technique. The developed coupled numerical model is applied for estimating net annual recharge for Mahi Right Bank Canal (MRBC) project the norms of Groundwater Resources Estimation committee (1984, 1997) and Indian Agricultural research Institute(1983). It is observed that the estimated net recharge by inverse modeling is closer to the net recharge estimated using the water balance approach. Further it is observed that the computed head distribution from the estimated recharge agree closely with the observed head distribution. The study concludes that the developed model for inverse modeling can be successfully applied to large groundwater system involving regional aquifers where reliable recharge estimation always requires considerable time and financial resources.