• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.6
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• pp.507-515
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• 2015

This paper proposes a filtering method for effective state vector estimation of highly maneuvering target. It is needed to hit the point called 'sweet spot' to increase the kill probability in missile interception. In paper, a filtering method estimates the length of a moving target tracked by a frequency modulated continuous wave (FMCW) radar. High resolution range profiles (HRRPs) is generated from the radar echo signal and then it's integrated into proposed filtering method. To simulate the radar measurement which is close to real, the study on the properties of scattering point of the missile-like target has been conducted with ISAR image for different angle. Also, it is hard to track the target efficiently with existing Kalman filters which has fixed measurement noise covariance matrix R. Therefore the proposed method continuously updates the covariance matrix R with sensor measurements and tracks the target. Numerical simulations on the proposed method shows reliable results under reasonable assumptions on the missile interception scenario.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.03a
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• pp.51-68
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• 2008

When the train enters into a tunnel a high speed, pressure waves are generated inside the tunnel. The pressure waves at propagate in a form of compression wave toward the tunnel exit and a fraction of the compression waves that arrives at the exit of the tunnel are discharged to outside of the tunnel and the remainder is reflected into the tunnel as expansion waves. The compression waves emitted from the tunnel does not radiate in a specific direction but in all directions. If the amplitude of the compression wave is great, it causes noise and vibration, and it is called "Micro-Pressure Wave." "Micro-Pressure Wave" must be considered as a decision for the optimum tunnel cross-section as the amplitude of the compression wave depends on train speed, tunnel length, area of tunnel and train. Therefore, this paper introduces the case study of Micro-Pressure Wave characteristics for determination of tunnel cross section in Honam high speed railway, the pressure inside the tunnel and the micro-pressure waves at tunnel exit were measured at Hwashin 5 tunnel in Kyungbu HSR line. At the same time. a test of train operation model was performed and then the measurement results and test results were compared to verify that the various parameters used as input conditions for the numerical simulations, which were appropriate. Also a model test was performed, in order to analysis of the Micro-Pressure Wave Mitigation Performance by Type of Hood at Entrance Portal.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.163-173
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• 2014

When evaluating the spatial resolution images and evaluation of low contrast resolution using CT standard phantom, and might present a automated quantitative evaluation method for minimizing errors by subjective judgment of the evaluator be, and try to evaluate the usefulness. 120kVp and 250mAs, 10mm collimation, SFOV(scan field of view) of 25cm or more than, exposure conditions DFOV(display field of view) of 25cm, and were evaluated the 24 passing images and 20 failing images taken using a standard reconstruction algorithm by using the Nuclear Associates, Inc. AAPM CT Performance Phantom(Model 76-410). Quantitative evaluation of low contrast resolution and spatial resolution was using an evaluation program that was self-developed using the company Mathwork Matlab(Ver. 7.6. (R2008a)) software. In this study, the results were evaluated using the evaluation program that was self-developed in the evaluation of images using CT standard phantom, it was possible to evaluate an objective numerical qualitative evaluation item. First, if the contrast resolution, if EI is 0.50, 0.51, 0.52, 0.53, as a result of evaluating quantitatively the results were evaluated qualitatively match. Second, if CNR is -0.0018~-0.0010, as a result of evaluating quantitatively the results were evaluated qualitatively match. Third, if the spatial resolution, as a result of using a image segmentation technique, and automatically extract the contour boundary of the hole, as a result of evaluating quantitatively the results were evaluated qualitatively match.

• Journal of IKEEE
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• v.18 no.2
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• pp.272-281
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• 2014

In electrical impedance tomography (EIT), modified Newton Raphson (mNR) method is widely used inverse algorithm for static image reconstruction due to its convergence speed and estimation accuracy. The unknown conductivity distribution is estimated iteratively by minimizing a cost functional such that the residual error namely the difference in measured and calculated voltages is reduced. Although, mNR method has good estimation performance, EIT inverse problem still suffers from ill-conditioned and ill-posedness nature. To mitigate the ill-posedness, generally, regularization methods are adopted. The inverse solution is highly dependent on the choice of regularization parameter. In most cases, the regularization parameter has a constant value and is chosen based on experience or trail and error approach. In situations, when the internal distribution changes or with high measurement noise, the solution does not get converged with the use of constant regularization parameter. Therefore, in this paper, in order to improve the image reconstruction performance, we propose a new scheme to determine the regularization parameter. The regularization parameter is computed based on residual error and updated every iteration. The proposed scheme is tested with numerical simulations and laboratory phantom experiments. The results show an improved reconstruction performance when using the proposed regularization scheme as compared to constant regularization scheme.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.181-188
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• 2015

The non-contact permanent magnet gear has advantages of high efficiency and improved reliability. It has other advantages of no mechanical friction loss, very little noise and vibration, and no need for lubricant. With these advantages, the non-contact permanent magnet gear that solves the physical contact problem of the mechanical gear has drawn attention. Due to this unique non-contact characteristic, the non-contact permanent magnet gear which is capable of non-contact torque transmission has replaced mechanical gear. The mechanical gears which is in many fields of the modern industry, is used mostly for power transmitting mechanical devices. However, it also has the problem of a low torque density, which requires improvement. In this paper, a novel pole piece shape is proposed in order to improve the problem of low torque density of the non-contact permanent magnet gear. The experiment data required for predicting the relationships among them are obtained using finiteelement Operating method based on two-dimensional (2-D) numerical analysis. Therefore, this paper derived an optimal model for thenon-contact permanent magnet gear with the novel pole piece using the Box-Behnken design, and the validity of the optimal design of the proposed pole piece shape through variance analysis and regression analysis demonstrated. In this paper, we performed the thransfer torque analysis in order to improve the torque density and power density, we have performed on optimal design of proposed pole piece shape using box-behnken.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.413-418
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• 2011

The thermodynamic properties of steam table are obtained by measurement or approximate calculation under appropriate assumptions. Therefore they are supposed to have basic measurement errors. And thermodynamic properties should be modeled through function approximation for using in numerical analysis. In order to make noised thermodynamic properties corresponding to measurement errors, random numbers are generated, adjusted to appropriate magnitudes and added to original thermodynamic properties. Both neural networks and quadratic spline interpolation method are introduced for function approximation of these modified thermodynamic properties in the saturated water based on pressure and temperature. In analysis spline interpolation method gives much less relative errors than neural networks at both ends of data. Excluding the both ends of data, the relative errors of neural networks is generally within ${\pm}0.2%$ and those of spline interpolation method within ${\pm}0.5$~1.5%. This means that the neural networks give smaller relative errors compared with quadratic spline interpolation method within range of use. From this fact it was confirmed that the neural networks trace the original values better than the quadratic interpolation method and neural networks are more appropriate method in modelling the saturated steam table.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.59-66
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• 2005

The main purpose of this paper is to describe a highly efficient common mid-point (CMP) data acquisition method for ground-penetrating radar (GPR) surveying, which is intended to widen the application of GPR. The most important innovation to increase the efficiency of CMP data acquisition is continuous monitoring of the GPR antenna positions, using a real-time kinematic Global Positioning System (RTK-GPS). Survey time efficiency is improved because the automatic antenna locating system that we propose frees us from the most time-consuming process-deployment of the antenna at specified positions. Numerical experiments predicted that the data density and the CMP fold would be increased by the increased efficiency of data acquisition, which results in improved signal-to-noise ratios in the resulting data. A field experiment confirmed this hypothesis. The proposed method makes GPR surveys using CMP method more practical and popular. Furthermore, the method has the potential to supply detailed groundwater information. This is because we can convert the spatially dense dielectric constant distribution, obtained by using the CMP method we describe, into a dense physical value distribution that is closely related to such groundwater properties as water saturation.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.327-333
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• 2008

In general, a lens with large NA makes image quality better. There are many kinds of cheap concave mirrors with large aperture and NA. This paper presents a method that uses a large aperture projection imaging system to enhance the image used for 3D shape measurement. This method makes it possible to enhance reflection uniformity on the object surface and increases SNR (Signal to Noise Ratio). Using a large aperture lens, it is possible to obtain a brighter image, reducing the shading nature in the image boundary, and enhancing the reflection uniformity even on woven surfaces. Because of the exorbitant cost of a large aperture projection lens larger than 150 mm in diameter, a refractive lens was exchanged with a concave mirror resulting in the same optical effect. In experiment, changing NA $0.15{\sim}0.8$, image contrast was enhanced from 46 to 1.33. Incidentally, the effect of the concave mirror was tested successfully through the experiment.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.591-598
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• 2021

The digital phase-locked loops(DPLL) is a circuit used for phase synchronization and has been generally used in various fields such as communication and circuit fields. State estimators are used to design digital phase-locked loops, and infinite impulse response state estimators such as the well-known Kalman filter have been used. In general, the performance of the infinite impulse response state estimator-based digital phase-locked loop is excellent, but a sudden performance degradation may occur in unexpected situations such as inaccuracy of initial value, model error, and disturbance. In this paper, we propose a minimum variance finite impulse response filter with optimal horizon for designing a new digital phase-locked loop. A numerical method is introduced to obtain the measured value interval length, which is an important parameter of the proposed finite impulse response filter, and to obtain a gain, the covariance matrix of the error is set as a cost function, and a linear matrix inequality is used to minimize it. In order to verify the superiority and robustness of the proposed digital phase-locked loop, a simulation was performed for comparison and analysis with the existing method in a situation where noise information was inaccurate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.319-325
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• 2021

A fine dust measurement using drones is becoming an increasingly common technology, and air pollutants can be identified through dust monitoring in partial industrial areas. A station for measuring fine dust provides information at large construction site offices. On the other hand, it was difficult to check the fine dust in the pollutant source accurately. Therefore, the drone took measurements directly after been placed at the site. While measuring fine dust, monitoring noise occurred due to the influence of the drone's down-wind during landing, but the measurements were similar to the numerical value of the grounded pollution source on the height of 30 m. The field applicability to the study area has limitations in periodic updates using satellite images because the terrain was constantly changing due to considerable flattening fieldwork. Therefore, this study implemented a system that can reflect real-time field information through GIS mapping using drones.