• International Journal of CAD/CAM
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• v.9 no.1
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• pp.37-46
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• 2010

Existing methods for the registration of blurred images are efficient for the artificially blurred images or a planar registration, but not suitable for the naturally blurred images existing in the real image mosaic process. In this paper, we attempt to resolve this problem and propose a method for a distortion-free stitching of naturally blurred images for image mosaic. It adopts a multi-resolution and robust feature based inter-layer mosaic together. In each layer, Harris corner detector is chosen to effectively detect features and RANSAC is used to find reliable matches for further calibration as well as an initial homography as the initial motion of next layer. Simplex and subspace trust region methods are used consequently to estimate the stable focal length and rotation matrix through the transformation property of feature matches. In order to stitch multiple images together, an iterative registration strategy is also adopted to estimate the focal length of each image. Experimental results demonstrate the performance of the proposed method.

• KIEAE Journal
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• v.14 no.5
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• pp.75-80
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• 2014

An attempt has been made to prove the so-called 'feature accumulation theory'. It is the theory describing that people tend to feel the same space with more identifiable objects much larger than that with fewer objects. Applying this theory to our cognition of spatial size, this paper made an experiment. Students were asked that if the lecture room they are sitting becomes a module (module 1), then how large are the questioned spaces in the campus. The result was striking. Through the mental image processing, they answered that the library and the architecture building looks much smaller than they actually are, and more surprisingly the basketball field much more smaller than it really is. This experiment shows that there is a strong tendency by which people regard the space much larger when there are more occupiable or behavior-causing elements in the space. In the case of basketball field, since there is nothing that can be occupied, this open space is seen as a small space for the subjects. This line of cognitive perception can be applied to the practice of urban planning and architectural planning. With the same size of given space, we can make it feel more rich and larger.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.2
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• pp.277-286
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• 2010

In this paper amplitude and phase distortion of the received signal through a fading channel results in a severe performance degradation of the communication system, Therefore we consider the variance of the maximum a posteriori phase estimate of sinusoidal signal by the Cramer-Rao bound in wireless fading channel. To find the Cramer-Rao lower bound for the variance of the phase, We use the derived probability density function(pdf) of the phase in Nakagami fading channel. We analyze the error performance of modulation signals using order statistics on generalized combining reception and find adequate diversity branch number.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4201-4207
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• 2015

In this study, the performance of underground water pipeline system affected by earthquakes is examined by using data acquired after MW 6.2 February 22, 2011 earthquake in Christchurch, NZ. Water pipeline repair rates, expressed as repairs/km, for different types of pipe are evaluated inside the areas of which liquefaction induced by permanent ground deformation was observed and assessed relative to differential settlement and lateral ground strain, calculated from high resolution LiDAR data acquired before and after each seismic event. The earthquake performance of underground water pipeline systems associated with permanent ground deformation is summarized in this paper. The results show that highly ductile polyethylene water pipelines has a high earthquake performance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.229-235
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• 2018

Research on indoor location tracking technology using smart phone is actively being carried out. Especially, in order to display the movement path of the smartphone on the map, the azimuth angle should be estimated by using the geomagnetic sensor built in most smart phones. Due to the distortion of the magnetic field due to the surrounding steel structure and the inclination of the smartphone, the estimation error of azimuthal angle may be occurred. In this paper, we propose a correction method of the geomagnetic sensor at the stationary state and a correction method for the inclination of the smartphone. We also propose a method to correct the azimuth error due to the difference between the magnetic north and the grid north.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.2
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• pp.71-83
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• 2022

In this study, an indicator and assessment system for evaluating the monthly hydrological cycle was prepared using simple factors such as the landuse status of the watershed and topographic characteristics to the dynamic water balance model (DWBM) based on the Budyko framework. The parameters a1 of DWBM are introduced as hydrologic cycle indicators. An indicator estimation regression model was developed using watershed characteristics data for the introduced indicator, and an assessment system was prepared through K-means cluster analysis. The hydrological cycle assessment system developed in this study can assess the hydrological cycle with simple data such as land use, CN, and watershed slope, so it can quickly assess changes in hydrological cycle factors in the past and present. Because of this advantage is expected that the developed assessment system can predict changes in the hydrological cycle and use an auxiliary tool for policymaking.

• International Journal of Advanced Culture Technology
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• v.10 no.3
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• pp.339-345
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• 2022

In this paper, the effect of porosity on the acoustic phase velocity of the 3D printed Kelvin closed-cell structure was investigated using the spectral phase analysis. Since Kelvin cells bring about the large amount of scattering, acoustic pulses in ultrasonic measurements undergoes a distortion of waveforms due to the dispersion effect. In order to take account on the dispersion, mathematical expressions for calculating the phase velocity of longitudinal waves propagating normal to the plane of the Kelvin structure are suggested by introducing a complex wave number based on Fourier transform. 3D Kelvin structure composed of identical unit-cells, a polyhedron of 14 faces with 6 quadrilateral and 8 hexagonal faces, was developed and fabricated by 3D CAD and 3D printer to represent the micro-structure of porous materials such as aluminum foam and cancellous bone. Total nine samples of 3D Kelvin structure with different porosity were made by changing the thickness of polyhedron. Ultrasonic pulse of 1MHz center frequency was applied to the Kelvin structures for the measurement of the phase velocity of ultrasound using the TOF(time-of-flight) and the phase spectral method. From the experimental results, it was found that the acoustic phase velocity decreased linearly with the porosity.

• Progress in Superconductivity and Cryogenics
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• v.25 no.1
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• pp.16-20
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• 2023

The International Electrotechnical Commission (IEC) 61788-26:2020 provides guidelines for measuring the critical current of Rare-earth barium copper oxide (REBCO) tapes using two methods: linear ramp and step-hold methods. The critical current measurement criterion, 1 or 0.1 μV/cm of electric field from IEC 61788-26 has been normally applied to REBCO coils or magnets. No-insulation (NI) winding technique has many advantages in aspects of electrical and thermal stability and mechanical integrity. However, the leak current from the NI REBCO coil can cause distortion in critical current measurement due to the characteristic resistance which causes the radial current flow paths. In this paper, we simulated the NI REBCO coil by applying both linear ramp and step-hold methods based on a simplified equivalent circuit model. Using the circuit analysis, we analyzed and evaluated both methods. By using the equivalent circuit model, we can evaluate the critical current of the NI REBCO coil, resulting in an estimation error within 0.1%. We also evaluate the accuracy of critical current measurement using both the linear ramp and step-hold methods. The accuracy of the linear ramp method is influenced by the inductive voltage, whereas the accuracy of the step-hold method depends on the duration of the hold-time. An adequate hold time, typically 5 to 10 times the time constant (τ), makes the step-hold method more accurate than the linear ramp method.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.157-158
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• 2009

본 논문에서는 움직임 추정을 위한 탐색 영역내의 스캔 방법을 움직임 벡터가 나올 확률에 근거하여 가변적으로 적용하여 불필요한 후보 블록을 제거하는 PDE(patial distortion elimination) 기반의 고속 블록 매칭 알고리즘을 제안한다. 제안한 방법은 기존의 방법보다 불필요한 계수를 효율적으로 제거하기 위하여 탐색 영역 안에서 움직임 벡터가 존재 할 확률이 가장 높은 영역은 전영역 탐색을 적용하고, 움직임 벡터가 존재할 확률이 낮은 영역은 한 픽셀 건너 뛰어서 블록 정합하여 계산 비용을 효율적으로 감소시켯다. 제안한 알고리즘은 극히 낮은 화질 저하를 가지며, 기존의 H.264에서 사용되고 있는 전역 탐색 알고리즘에 비해 P프레임의 경우 85% 이상의 계산 비용 감소가 있어 H.264를 이용하는 비디오 압축 응용 분야에 유용하게 사용될 수 있을 것이다.

• The Journal of the Acoustical Society of Korea
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• v.25 no.4
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• pp.172-177
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• 2006

Various research and development on Synthetic Aperture Sonar technique is under way to enhance bearing resolution of a SONAR system. In this paper, we estimated perturbed array shapes, and compensated distortion by using estimated away shapes and synthesized arrays in aperture domain such as an ETAM technique. As experimental data, we used the one obtained from towed array in neighboring waters of the Korean peninsula. Through simulation on data where tow-ship speed is maintained at a constant level, we confirmed that synthesis effect of increasing SNR and narrowed beam width of main lobe was consistently demonstrated for about 1 minute when coherence of target signal was maintained. Also, we showed that the synthesis effect with respect to time was constantly maintained.