• Journal of the Korean Society of Visualization
• /
• v.21 no.2
• /
• pp.14-23
• /
• 2023

The pressure difference across stenotic blood vessels is a commonly used clinical metric for diagnosing many cardiovascular diseases. At present, most clinical pressure measurements rely solely on invasive catheterization. In this study, we propose a novel method for non-invasive pressure estimation using the incompressible Navier-Stokes equations and a 3D multi-path integration approach. We verify spatio-temporal convergence on an in-silico dataset of a cylindrical straight pipe phantom with steady and pulsatile flow fields. We then evaluate the proposed method on an in vitro dataset of reconstructed control, pre-operative, and post-operative carotid artery cases acquired from 4D flow MRI. The performance of our method is compared to existing approaches based on the pressure Poisson equation and work-energy relative pressure. The results demonstrate the proposed method's high accuracy, robustness to spatio-temporal subsampling, and reduced sensitivity to noise, highlighting its great potential for non-invasive pressure estimation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.12C
• /
• pp.1138-1146
• /
• 2009

Digital cameras adopting a single CCD detector collect image color by subsampling in three color planes and successively interpolating the information to reconstruct full-resolution color images. Therefore, to recovery of a full-resolution color image from a color filter array (CFA) like the Bayer pattern is generally considered as an interpolation issue for the unknown color components. In this paper, we first calculate luminance component value by combining R, G, B channel component information which is quite different from the conventional demosaicing algorithm. Because conventional system calculates G channel component followed by computing R and B channel components. Integrating the obtained gradient edge information and the improved weighting function in luminance component, a new edge sensitive demosaicing technique is presented. Based on 24 well known testing images, simulation results proved that our presented high-quality demosaicing technique shows the best image quality performance when compared with several recently presented techniques.

• Journal of the Korea Society of Computer and Information
• /
• v.6 no.2
• /
• pp.65-69
• /
• 2001

Edge detection is the most important process that belongs to the first step in image recognition or vision system and can determine the efficiency valuation. The edge detection with color images is very difficult. because color images have lots of information that contain not only general information representing shape, brightness and so on but also that representing colors. In this paper, we propose architecture of universalized Color Morphological Pyramids(CMP) which is able to give effective edge detection. Image pyramid architecture is a successive image sequence whose area ratio 2$\^$-1/(ι= 1, 2, . . . ,N) after filtering and subsampling of input image. In this technique, noise removed by sequential filtering and resolution is degraded by downsampling using CMP in various color spaces. After that, new level images are constructed that apply formula using distance of neighbor vectors in close level images and detection its image.

• Journal of Korea Game Society
• /
• v.9 no.4
• /
• pp.89-96
• /
• 2009

In general, the size of volume data is large since it has logical 3D structure so it takes long time to manipulate. Much work has been done to improve processing speed of volume data. In this paper, we propose a interlaced scanning volume rendering that reduce computation time by using temporal coherence with minimum loss of image quality. It renders a current frame by reusing information of previous frame. Conventional volume raycasting renders each frame by casting rays on every pixels. On the other hand, our methods divided an image into n-pixel blocks, then it casts a ray on a pixel of a block per each frames. Consequently, it generates an image by accumulating pixel values of previous n frames. The quality of rendered image of our method is better than that of simple screen space subsampling method since it uses afterimage effect of human cognitive system, and it is n-times faster that the previous one.

• Proceedings of the Korea Contents Association Conference
• /
• 2003.05a
• /
• pp.416-420
• /
• 2003

In this paper, we implemented a dual-resolution image database system for the fast naked-eye retrieval using interpolation. This system can solve two conventional problems : a blocking noise at zoom-out image in single high resolution method and a big storage to store in simple dual-resolution image database system. The proposed method makes a subsampled image by subsampling a original image, and then a interpolated image of it using interpolation. After that, a hybrid dual-resolution image database is composed based on the differential image between the interpolated image and the original image. Experimental results of simulating through 60 sample images shows that the proposed method is 0.011 second faster than simple high-resolution method in the retrieval time - one is 0.003 second, the other is 0.014 second, respectively. Also, that improves 14.7% more than simple dual-resolution method in the stored size - one is 19,821 byte, the other is 16,910 byte, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.9A
• /
• pp.1401-1410
• /
• 1999

In this paper, we propose a fast block matching algorithm using the lower and upper bound of mean absolute difference (MAD) which is calculated at the search region overlapped with neighbor blocks. At first, we calculate the lower bound of MAD and reduce the search point by using this lower bound. In this method, we can get good prediction error performance close to full search block matching algorithm (FSBMA), but there exists some computational complexity that has to be reduced. Therefore, we further reduce the computational complexity by using pixel subsampling besides the lower and upper bound of MAD. Experimental results show that we can remarkably reduce the computational complexity with good prediction error performance close to FSBMA.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.9A
• /
• pp.1392-1400
• /
• 1999

In this paper, we propose a two-stage fast full search algorithm for block motion estimation that produces the same performance to that of full search algorithm (FSA) but with remarkable computation reduction. The proposed algorithm uses the search region subsampling and the difference of adjacent pixels in the current block. In the first stage, we subsample the search region by a factor of 9, and then calculate mean absolute error (MAE) at the subsampled search points. And in the second stage, we reduce the search points that need block matching process by using the lower bound of MAE value at each search Point. We Set the lower bound of MAE value for each search point from the MAE values which are calculated at the first stage and the difference of adjacent pixels in the current block. The experimental results show that we can reduce the computational complexity considerably without any degradation of picture quality.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.7
• /
• pp.225-230
• /
• 2013

In a bandpass sampling (BPS), the frequency of the sampler is lower than that of the signal being sampled. In this method, the baseband spectrum directly appears by the sampling operation, so that it is not necessary to use any frequency down-converter, which makes the receiver's hardware simpler. The second-order BPS uses two identical BPS samplers, of which sampling times are offset by each other. By exploiting the relationship between two sampled signals, it can be possible to cancel the aliased signal component or the interference due to the bandpass sampling. In order to cancel the interference, an interpolant filter is used to manipulate the phase characteristics of the BPS sampled signal. In this paper, it is introduced a multiband interpolant filter which can simultaneously cancel multiple interference signals that have been aliased from multiple frequency bands. In case of no need of interference cancellation, another method is suggested to enhance the signal quality by 3dB. A computer simulation has been performed, and the feasibility of the suggested methods has been verified.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.3
• /
• pp.162-170
• /
• 2015

In the bandpass sampling (BPS), the sampling frequency is lower than the frequency of the signal to be sampled. In this method, the baseband spectrum can be directly obtained by the sampling operation. This makes the frequency down converter unnecessary as well as the receiver's circuit simpler. In the second-order BPS system, two sampling devices are used. When aliasing occurs due to the sampling operation, the aliased component can be cancelled by combining the two sampled signals. In this paper, it is presented a design method of the second-order BPS system when multiple interferences are simultaneously aliased to the signal component. The optimum phase of the interpolant filter is searched for maximizing the signal-to-interference ratio, and a practical formula for the suboptimal phase is derived in terms of the power spectrum profile of the BPS input. A computer simulation has been performed for the proposed second-order BPS system, and it has been shown that the signal-to-interference ratio can be increased by considering multiple aliasing.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2012.10a
• /
• pp.69-72
• /
• 2012

In the bandpass sampling(BPS), the sampling frequency is lower than the frequency of the RF(radio frequency) signal being sampled. In this method, the baseband spectrum directly appears by the sampling itself, so that it is not necessary to use any down converter, making the receiver's hardware simpler. The second-order BPS uses two identical BPS samplers operating with an offset timing to each other. By a processing with their two sampled signals, it can be possible to cancel the aliasing or interference component if any due to the bandpass sampling. The interpolant filter, which is to manipulate the phase characteristics of the sampled signal, affects the performance of the cancellation. In this paper, a multiband interpolant filter is introduced, with which multiple interference signals from multiple RF bands can be cancelled simultaneously. We suggest several phase characteristics for the interpolant filter and have evaluated their performances through computer simulations. It has been shown that the filter with a continuous phase function gives the better performance.