• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.1
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• pp.59-65
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• 2020

This paper presents comparative results of configuration modeling and aerodynamic analysis to single-engine airplanes such as C-172, SR-20, and DA40NG. The software OpenVSP was used as an airplane configuration modeling tool. OpenVSP can provide the fastest method to get three-dimensional aircraft configuration from given basic data and drawings of aircraft. Parametric design input in OpenVSP, from given aircraft geometric parameters, was applied to small airplanes mentioned. New aircraft models in this study were reversely designed to coincide with the publicly obtained dimensions of the original aircraft. The basic aerodynamic analysis of newly designed modeling aircraft was performed by the vortex lattice method. Results are shown that the similarity of aerodynamic data obtained except for the lack of DA40NG. In conclusion, the modeling process applied to this work is valuable to obtain conceptual design insight in the reverse design from the small airplanes currently in use for flight training.

• Spatial Information Research
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• v.10 no.4
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• pp.551-565
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• 2002

To carry out systematic groundwater assessment, exploration and management and to use these for protection of optimal groundwater yield, a data analysis and management system is required. Thus, the object of this research was to develop and apply software that integrates GIS and groundwater modeling: GISGAM (GIS for groundwater analysis and management system). The GIS program ArcView and the groundwater-modeling program MODFLOW were used for the GISGAM. The program components consist of a pre-processor, a processor, and a post-processor for groundwater modeling. In addition, GIS functions such as input, manipulation, analysis and output of data were embedded into the program. In applying the program to pilot area, topography, geology, soil, land use and well databases, and a groundwater flow model were constructed for the study area. This case study revealed the advantage and convenience of groundwater modeling using GIS capabilities. By integrating GIS and the groundwater model, the impact of changing values of hydrogeological constants on model results could be more easily evaluated.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.1
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• pp.116-123
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• 2003

In this paper, interleaved boost converter is applied as a pre-regulator in switched mode power supply. The pre-regulator plays a role to improve power factor. Interleaved Boost Power Factor Corrector(IBPFC) can reduce input current ripple as a single voltage control loop only without inner current loop, because input current is divided each 50% by two switching devices. Each converter cell is also operated in discontinuous current mode and inductor current of each converter is discontinuous. Total input current which is composed by each converter cell is continuous current. Thus, IBPFC is able to improve input current ripple. IBPFC operating in discontinuous current mode can be classified as six modes from switching state and be carried out state space averaging small signal modeling. A control transfer function is obtained according to the modeling. Single voltage control loop is also constructed by the control transfer function. From experimental result, improvement of power factor and input current ripple are verified.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1220-1228
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• 2010

In this paper, we suggest a scheme to develop an efficient discrete nonlinear model based on polynomial structure for a RF power amplifier(PA). We describe a procedure to extract a discrete nonlinear model such as Taylor series or memory polynomial by sampling the input and output signal of RF PA. The performance of the model is analyzed varying the model parameters such as sample rate, nonlinear order, and memory depth. The results show that the relative error of the model is converged if the parameters are larger than specific values. We suggest an efficient modeling scheme considering complexity of the discrete model depending on the values of the model parameters. Modeling efficiency index(MEI) is defined, and it is used to extract optimum values for the model parameters. The suggested scheme is applied to discrete modeling of various RF PAs with various input signals such as WCDMA, WiBro, etc. The suggested scheme can be applied to the efficient design of digital predistorter for the wideband transmitter.

• Korean Journal of Remote Sensing
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• v.37 no.1
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• pp.161-167
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• 2021

This paper presents the method to quantitatively evaluate the uncertainty of the semi-empirical Bidirectional Reflectance Distribution Function (BRDF) model for Himawari-8/AHI. The uncertainty of BRDF modeling was affected by various issues such as assumption of model and number of observations, thus, it is difficult that evaluating the performance of BRDF modeling using simple uncertainty equations. Therefore, in this paper, Monte-Carlo method, which is most dependable method to analyze dynamic complex systems through iterative simulation, was used. The 1,000 input datasets for analyzing the uncertainty of BRDF modeling were generated using the Second Simulation of a Satellite Signal in the Solar Spectrum (6S) Radiative Transfer Model (RTM) simulation with MODerate Resolution Imaging Spectroradiometer (MODIS) BRDF product. Then, we randomly selected data according to the number of observations from 4 to 35 in the input dataset and performed BRDF modeling using them. Finally, the uncertainty was calculated by comparing reproduced surface reflectance through the BRDF model and simulated surface reflectance using 6S RTM and expressed as bias and root-mean-square-error (RMSE). The bias was negative for all observations and channels, but was very small within 0.01. RMSE showed a tendency to decrease as the number of observations increased, and showed a stable value within 0.05 in all channels. In addition, our results show that when the viewing zenith angle is 40° or more, the RMSE tends to increase slightly. This information can be utilized in the uncertainty analysis of subsequently retrieved geophysical variables.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.340-347
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• 2016

Since the 1970s, manufacturing has been one of the key driving forces that has led to Korea's economic growth. However, this growth rate has been reduced significantly since the 2000s, and shows that revenues and employment are steadily decreasing. In addition, while manufacturing investment in Korea has dropped sharply, the United States, Germany, Japan, and other major countries have increased investment in manufacturing. These countries have promoted manufacturing innovation strategies that include the convergence of information and communications technologies (ICT) and manufacturing. For manufacturing innovation, it is important for time and cost savings required for product development to be achieved by changes in the production process, especially product design. Modeling and simulation (M&S) is a process that replaces physical product design, mockup making, and testing, with virtual product creation (modeling) and engineering analysis (simulation). In this paper, we analyze the economic ripple effect of supercomputing M&S using an input-output model technique based on the input-output tables published by the Bank of Korea. When we set the M&S budget (about US$16 million for the last 10 years) of the Korea Institute of Science and Technology Information (KISTI) as input coefficients, the effect on production inducement, value-added inducement, and employment inducement was analyzed to be US$24 million, US$13.4 million, and 267, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.10
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• pp.1043-1049
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• 2012

The FEM analysis of machine tools is the general analysis process to evaluate machine performance in the industry for a long time. Despite advances in FEM software, because of difficult simplicity of CAD drawing, little experience of joints stiffness modeling and troublesome manual contact area divide for bindings, the industry designers think the FEM analysis is still an area of FEM analysis expert. In this paper, the automation of modeling process with simplicity of drawing, modeling of joints and contact area divide is aimed at easy FEM analysis to enlarge utilization of a virtual machine tools. In order to verify the effects of modeling automation, a slant bed type model with tilting table is analyzed. The results show FEM modeling automation method only needed 45 minutes to complete the whole modeling process, while manual modeling method requires almost one month with 8200 calculations for coordinate transformations and stiffness data input.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.393-399
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• 1997

Single-phase and three-phase AC to DC power converters are becoming frequently used for high voltage/high power applications such as telecommunications. They often require input/output transformer isolation for safety, a unity input power factor for minimum reactive power, free input harmonic currents fed back to the AC Power distribution system and, finally, high efficiency and high power density for minimum weight and volume. The proposed boost converter for power factor correction (PFC) provides an unity input power factor, low harmonic distortion and high efficiency along with reduced volume and weight. Single-phase 220VAC input/380VDC 1KW output prototype is constructed and experimental results will be verified with those of PSpice simulation.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1955-1959
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• 2005

This paper presents a systematic analysis and a simple design of a robust adaptive control law for a class of non linear systems with modeling errors and a time-delay input. The theory for designing a robust adaptive control law based on input- output feedback linearization of non linear systems with uncertainties and a time-delay in the manipulated input by the approach of parameterized state feedback control is presented. The main advantage of this method is that the parameterized state feedback control law can effectively suppress the effect of the most parts of nonlinearities, including system uncertainties and time-delay input in the pp-coupling perturbation form and the relative order of non linear systems is not limited.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2712-2714
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• 1999

The small signal model for input series-output parallel connected converter system employing charge control together with input capacitor voltage feedback loop is developed. From the model developed, the effect of input capacitor voltage feedback loop to the system stability and outer loop compensator design is analyzed. Theoretical results and simulation show that input capacitor voltage feedback loop has no critical effects on the system stability, so the system can be reduced to a equivalent single module for the stability analysis and outer loop compensator design.