• Korean Journal of Agricultural and Forest Meteorology
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• 제19권4호
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• pp.270-279
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• 2017

Regional assessment of crop productivity using a gridded simulation approach could aid policy making and crop management. Still, little effort has been made to develop the systems that allows gridded simulations of crop growth using ORYZA 2000 model, which has been used for predicting rice yield in Korea. The objectives of this study were to develop a series of data processing modules for creating input data files, running the crop model, and aggregating output files in a region of interest using gridded data files. These modules were implemented using C++ and R to make the best use of the features provided by these programming languages. In a case study, 13000 input files in a plain text format were prepared using daily gridded weather data that had spatial resolution of 1km and 12.5 km for the period of 2001-2010. Using the text files as inputs to ORYZA2000 model, crop yield simulations were performed for each grid cell using a scenario of crop management practices. After output files were created for grid cells that represent a paddy rice field in South Korea, each output file was aggregated into an output file in the netCDF format. It was found that the spatial pattern of crop yield was relatively similar to actual distribution of yields in Korea, although there were biases of crop yield depending on regions. It seemed that those differences resulted from uncertainties incurred in input data, e.g., transplanting date, cultivar in an area, as well as weather data. Our results indicated that a set of tools developed in this study would be useful for gridded simulation of different crop models. In the further study, it would be worthwhile to take into account compatibility to a modeling interface library for integrated simulation of an agricultural ecosystem.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• 제26권3호
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• pp.263-273
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• 2008

The precision of sensors' position is particularly important in the application of road extraction or digital map generation. In general, the various ranging solution systems such as GPS, Total Station, and Laser Ranger have been employed for the position of the sensor. Basically, the ranging solution system has problems that the signal may be blocked or degraded by various environmental circumstances and has low temporal resolution. To overcome those limitations a IMU/range integrated system could be introduced. In this paper, after pointing out the limitation of extended Kalman filter which has been used for workhorse in navigation and geodetic community, the two sampling based nonlinear filters which are sigma point Kalman filter using nonlinear transformation and carefully chosen sigma points and particle filter using the non-gaussian assumption are implemented and compared with extended Kalman filter in a simulation test. For the ranging solution system, the GPS and Total station was selected and the three levels of IMUs(IMU400C, HG1700, LN100) are chosen for the simulation. For all ranging solution system and IMUs the sampling based nonlinear filter yield improved position result and it is more noticeable that the superiority of nonlinear filter in low temporal resolution such as 5 sec. Therefore, it is recommended to apply non-linear filter to determine the sensor's position with low degree position sensors.

• Journal of Satellite, Information and Communications
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• 제1권2호
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• pp.1-7
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• 2006

GOCi (Geostationary Ocean Color Imager) is one of the COMS payloads that KARI is currently developing and scheduled to be in operation from around 2008. Its primary objective is to monitor the Korean coastal water environmental condition. We report the current progress in development of the integrated optical model as one of the key analysis tools for the GOCI in-orbit performance verification. The model includes the Sun as the emitting light source. The curved Earth surface section of 2500 km x 2500 km includingthe Korean peninsular os defined as a Lambertian scattering surface consisted of land and sea surface. From its geostationary orbit, the GOCI optical system observes the reflected light from the surfaces with varying reflectance representing the changes in its environmental conditions. The optical ray tracing technique was used to demonstrate the GOCI in-orbit performances such as red tide detection. The computational concept, simulation results and its implications to the on-going development of GOCI are presented.

• The Journal of Korean Institute of Next Generation Computing
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• 제13권4호
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• pp.29-39
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• 2017

Various electronic warfare situations drive the need to develop an integrated electronic warfare simulator that can perform electronic warfare modeling and simulation on radar threats. In this paper, we analyze the components of a simulation system to reversely model the radar threats that emit electromagnetic signals based on the parameters of the electronic information, and propose a method to gradually maintain the reverse extrapolation model of RF threats. In the experiment, we will evaluate the effectiveness of the incremental model update and also assess the integration method of reverse extrapolation models. The individual model of RF threats are constructed by using decision tree, naive Bayesian classifier, artificial neural network, and clustering algorithms through Euclidean distance and cosine similarity measurement, respectively. Experimental results show that the accuracy of reverse extrapolation models improves, while the size of the threat sample increases. In addition, we use voting, weighted voting, and the Dempster-Shafer algorithm to integrate the results of the five different models of RF threats. As a result, the final decision of reverse extrapolation through the Dempster-Shafer algorithm shows the best performance in its accuracy.

• Journal of Institute of Control, Robotics and Systems
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• 제19권3호
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• pp.209-218
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• 2013

Military surveillance systems with electro-optical sensors can be used to track a number of targets efficiently and reliably. In MTT (Multi-Target Tracking), joint events in which different tracks share the same measurements may occur. Measurement-to-track assignment are computationally challenging because of the number of operations increases exponentially with number of tracks and number of measurements. IHPDA (Integrated Highest Probability Data Association) based on a 2D-Assignment technique can find an optimal solution for measurement to track one-to-one assignments for complex environments. In this paper, LM-IHPDA (Linear Multi-Target IHPDA) which does not need to form all feasible joint events of association and thus the computational load is linear in the number of tracks and the number of measurements. Simulation studies illustrate the effectiveness of this approach in an infrared image environment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.253-258
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• 2008

PLM(Product Lifecycle Management) is one of innovative manufacturing paradigms which leverages e-business technologies to allow a company's product content to be developed and integrated with all company business process through the extended enterprise. In these days, most construction companies also make an effort to enhance their systems for creating, sharing and managing information to improve business efficiency through entire lifecycle of project execution. Because of different needs, business process and diverse engineering activities such as design, structural analysis, installing simulation, documents and data managements, a new paradigm for construction companies is needed to manage and share the entire workflow, and information in total project lifecycle. In this paper, we conducted user requirement and business process analysis of the construction to design architecture of C-PLM(Construction Project Lifecycle management) and implement a prototype of C-PLM systems based on commercial PDM system.

• Journal of the Earthquake Engineering Society of Korea
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• 제11권4호
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• pp.25-31
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• 2007

For areas such as the Korean Peninsula, which have moderate seismic activity but no available records of strong ground motion, synthetic seismograms can be used to evaluate ground motion without waiting for a strong earthquake. Such seismograms represent the estimated ground motions expected from a set of possible earthquake scenarios. Local site effects are especially important in assessing the seismic hazard and possible ground motion scenarios for a specific fault. The earthquake source and rupture dynamics can be described as a two-step process of rupture initiation and front propagation controlled by a frictional sliding mechanism. The seismic wavefield propagates through heterogeneous geological media and finally undergoes near-surface modulations such as amplification or deamplification. This is a complex system in which various scales of physical phenomena are integrated. A unified approach incorporates multi-scale problems of dynamic rupture, radiated wave propagation, and site effects into an all-in-one model using a three-dimensional, fourth-order, staggered-grid, finite-difference method. The method explains strong ground motions as products of complex systems that can be modified according to a variety of fine-scale rupture scenarios and friction models. A series of such deterministic earthquake scenarios can shed light on the kind of damage that would result and where it would be located.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제12권5호
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• pp.2279-2284
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• 2011

In most of radial distribution systems, the overcurrent protection coordination is adopted for the protection of apparatus and the improvement of electrical power system reliability. The protection coordination structure in distribution substation is composed of several circuit breakers(CB) with distribution lines originating from one substation bus under one transformer, which trip for their fault current. But sufficient analysis is necessary for the capacity of CB's in distribution systems with several distribution generations(DG). In this paper, a protection coordination method not to exceed the traditional capacity of CB's was proposed and certified through simulation by the PSCAD-EMTDC S/W.

• Bulletin of the Korean Space Science Society
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.30.2-30.2
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• 2011

In this report, we present in-orbit radiometric performance prediction for the Amon-Ra (Albedo Monitor and Radiometer) energy channel instrument. The Integrated Ray Tracing (IRT) computational technique uses the ray sets arriving at the Amon-Ra instrument aperture orbiting around the L1 halo orbit. Using this, the variation of flux arriving at the energy channel detector was obtained when the Amon-Ra instrument including the energy channel design observes the Sun and Earth alternately. The flux detectability was verified at the energy channel detector (LME-500-A, InfraTecTM). The detector time response and RMS signal voltage were then derived from the simulated flux variation results. The computation results demonstrate that the designed energy channel optical system satisfies the in-orbit detectability requirement. The technical details of energy channel instrument design, IRT model construction, radiative transfer simulation and output signal computation results are presented together with future development plan.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제59권3호
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• pp.609-613
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• 2010

In this paper, we optimized and simulated the heatsink of 75W LED module for street lighting and evaluated the optical properties with the manufactured heatsink. the structure of LED package make simple as chip and heatslug and thermal flow is analyzed by using the FEM(Finite Element Method) with CFdesign V10. Also, we measured the temperature of heatsink and evaluated the optical properties with infrared thermal image camera and integrated sphere system for luminous flux in $1\;[m^3]$ box. As results, Heatsink optimized in 3 mm pin thickness, 6 mm base thickness and 16 number of pin count by using Heatsink-designer and got the results which is the temperature of $47.37\;[^{\circ}C]$ and thermal resistance of $0.48407\;[W/^{\circ}C]$. In thermal flow simulation, the temperature of heatsink decreased from $51.54\;[^{\circ}C]$ to $51.51\;[^{\circ}C]$ and the temperature of heatsink by the time in real measurement decreased from $47.03\;[^{\circ}C]$ to $46.87\;[^{\circ}C]$. Moreover, we improve 0.68 % in the decreased ratio of the luminous flux.