• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.4
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• pp.30-39
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• 2010

Since Diffusion tensor from Diffusion Tensor Magnetic Resonance Imaging(DT-MRI) is so sensitive to noise, the principle eigenvector(PEV) calculated from Diffusion tensor could be erroneous. Tractography obtained from PEV could be deviated from the real fiber tract. Therefore regularization process is needed to eliminate noise. In this paper, to reduce noise in DT-MRI measurements, the Dyadic Sorting(DS) method as regularization of the eigenvalue and the eigenvector is applied in the tractography. To resort the eigenvalues and the eignevectors, the DS method uses the intervoxel overlap function which can measure the overlap between eigenvalue-eigenvector pairs in the $3\times3$ pixel. In this paper, we applied the DS method to the three-dimensional volume. We discuss the error analysis and numerical study to the synthetic and the experimental data. As a result, we have shown that the DS method is more efficient than the median filtering methods as much as 79.97%~83.64%, 85.62%~87.76% in AAE, AFA respectively for the corticospinal tract of the experimental data.

• Journal of Korea Multimedia Society
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• v.13 no.11
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• pp.1698-1705
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• 2010

In this paper, we propose a fast liver segmentation method from magnetic resonance(MR) images. Our method efficiently divides a MR image into a set of discrete objects, and boundaries based on the normalized gradient magnitude information. Then, the objects belonging to the liver are detected by using 2D seeded region growing with seed points, which are extracted from the segmented liver region of the slice immediately above or below the current slice. Finally, rolling ball algorithm, and connected component analysis minimizes false positive error near the liver boundaries. Our method was validated by twenty data sets and the results were compared with the manually segmented result. The average volumetric overlap error was 5.2%, and average absolute volumetric measurement error was 1.9%. The average processing time for segmenting one data set was about three seconds. Our method could be used for computer-aided liver diagnosis, which requires a fast and accurate segmentation of liver.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.6
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• pp.1881-1900
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• 2014

Since 802.11 wireless LANs are so widely used, it has become common for numerous access points (APs) to overlap in a region, where most of those APs are managed individually without any coordinated control. This pattern of wireless LAN usage is called the private OBSS (Overlapping Basic Service Set) environment in this paper. Due to frame collisions across BSSs, each BSS in the private OBSS environment suffers severe performance degradation. This study approaches the problem from the perspective of congestion control rather than noise or collision resolution. The retry limit, one of the 802.11 attributes, could be used for traffic control in conjunction with TCP. Reducing the retry limit causes early discard of a frame, and it has a similar effect of random early drops at a router, well known in the research area of congestion control. It makes the shared link less crowded with frames, and then the benefit of fewer collisions surpasses the penalty of less strict error recovery. As a result, the network-wide performance improves and so does the performance of each BSS eventually. Reducing the retry limit also has positive effects of merging TCP ACKs and reducing HOL-like blocking time at the AP. Extensive experiments have validated the idea that in the OBSS environment, reducing the retry limit provides better performance, which is contrary to the common wisdom. Since our strategy is basically to sacrifice error recovery for congestion control, it could yield side-effects in an environment where the cost of error recovery is high. Therefore, to be useful in general network and traffic environments, adaptability is required. To prove the feasibility of the adaptive scheme, a simple method to dynamically adjust the value of the retry limit has been proposed. Experiments have shown that this approach could provide comparable performance in unfriendly environments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.6
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• pp.666-674
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• 2019

In the mass spectrum of the mass spectrometer, the spectrum of the low peak adjacent to the spectrum having the high peak value is connected to each other and thus the separation is difficult. This inter-spectral overlap causes degradation of the mass spectral detection performance and resolution. In this paper, we propose a method to improve the mass spectrum detection performance and peak accuracy of residual gas analyzer. The type discrimination according to the characteristics of the ion signal block and the pre-correction for the peak position error can separate and detect the spectrum of the low peak connected to the adjacent spectra. To verify the performance of the proposed method, we compared the proposed method with the conventional method in simulations using actual ion signals obtained from the mass spectrometer under development.

• The Korean Journal of Nuclear Medicine Technology
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• v.28 no.1
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• pp.57-69
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• 2024

Purpose: Quantitative analysis through count measurement in nuclear medicine planar images is limited by analysis techniques that are useful for obtaining various clinical information or by organ overlap or artifacts in actual clinical practice. On the other hand, the use of SPECT tomography images is quantitative analysis using volume rather than planar, which is not only free from problems such as projection overlap, but also has excellent quantitative accuracy. In the use of developing SPECT quantitative analysis technology, this study aims to compare the accuracy of quantitative analysis between ROI of the conventional planar images and VOI of the SPECT tomographic images in evaluating the count change happened by the volume change of the source. Materials and Methods: A ^99mTcO₄^- source(200.17 MBq) was filled with sterilized water in the syringe to create a phantom with an inner diameter volume of 60 cc, and a planar image and a SPECT image were obtained by reducing the volume by 15 cc (25%) respectively. ROI and VOI(threshold: 1~45%, 5% interval) were set for each image obtained to estimate true count and measure the total count, and compared with the preseted volumetric change rate(%). Results: When volume changes of 25%, 50%, and 75% occurred in the initial volume of 60 cc(100%) of the phantom, the average count changes of the measured planar image were 26.8%, 53.2%, 77.5%, and the average count changes of the SPECT image were 24.4%, 50.9%, and 76.8%. In this case, the VOI size(cm³) set showed an average change rate of 25.4%, 51.1%, and 76.6%. The highest threshold value for the accuracy of radioactive concentration by VOI size (average error -1.03%) was 35%, and the VOI size of the same threshold had an error of -17.1% on average compared to the actual volume. Conclusion: On average, the count-based volumetric change rate in nuclear medicine images was able to track changes more accurately using VOI than ROI, but there was no significant difference with relatively similar value. However, the accuracy of radioactive concentration according to individual VOI sizes did not match, but it is considered that a relatively accurate quantitative analysis can be expected when the size of VOI is set smaller than the actual volume.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.4
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• pp.47-52
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• 2009

The transmitted signal from a source is transmitted to a destination through wireless channels. But if the mobile destination is out of the coverage of the source or exists in the shady side of the coverage, the destination can not receiver the signal from the source and they can not maintain communication. In order to overcome these problems, we adopt relays. A system employing relays is a multi-hop relay system. In the multi-hop relay system, coverages of each relay that is used for different systems can overlap each other in some place. When there is a destination in this place, interference occurs at the destination. In this paper, we study on the efficient co-channel interference (CCI) cancellation algorithm. In the proposed strategy, CCI is mitigated by zero forcing (ZF) or minimum mean square error (MMSE) receivers. Moreover, successive interference cancellation (SIC) with optimal ordering algorithm is applied for rejecting CCI efficiently. And we analyzed and simulated the proposed system performance in Rayleigh fading channel. In order to justify the benefit of the proposed strategy, the overall system performance is illustrated in terms of bit error probability.

• The Journal of the Petrological Society of Korea
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• v.17 no.2
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• pp.51-56
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• 2008

The geologic age of the Okcheon metamorphic belt, used to be a longstanding puzzle, has been settled down to Neoproterozoic to Paleozoic with discovery of fossils and isotopic age dating of metavolcanic rocks. As isotopic ages become accumulated, there appeared a controversy over the age of peak metamorphism in the Okcheon metamorphic belt, i.e., a single late Permian-early Triassic metamorphism (CHIME allanite age and U-Pb age of metamorphic zircon), or earlier independent presence of early Permian metamorphism (U-Pb age of allanite within garnet porphyroblast). If we compare the isotopic ages that can represent metamorphism, the data for the latter have much larger error than those of the former with some overlap considering the error limits. It means that, the former, supported by two independent ages, is considered a better representation for the age of metamorphism of the Okcheon metamorphic belt. Therefore, I propose the idea of early Permian metamorphism should better be reserved until conclusive evidence appears. The late Permian-early Triassic metamorphic age suggest that the effect of continental collision influenced much of the middle part of Korean Peninsula, namely, the Imjingang belt, the Gyeonggi massif and the Okcheon belt.

• Journal of Korea Multimedia Society
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• v.14 no.3
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• pp.348-355
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• 2011

In this paper, we propose an automatic prostate segmentation method from dynamic magnetic resonance (MR) images. Our method detects contrast-enhanced images among the dynamic MR images using an average intensity analysis. Then, the candidate regions of prostate are detected by the B-spline non-rigid registration and subtraction between the pre-contrast and contrast-enhanced MR images. Finally, the prostate is segmented by performing a dilation operation outward, and sequential shape propagation inward. Our method was validated by ten data sets and the results were compared with the manually segmented results. The average volumetric overlap error was 6.8%, and average absolute volumetric measurement error was 2.5%. Our method could be used for the computer-aided prostate diagnosis, which requires an accurate prostate segmentation.

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.79-83
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• 2004

The curved blocks which compose the bow and stem of a ship contain many skewed joints that are inclined horizontally and vertically. Most of these joints have a large fitness error and are continuously changing their form and are not easily accessible. The welding position and parameter values should be appropriately set in correspondence to the shape and the inclination of the joints. The welding parameters such as current, voltage, travel speed, and melting rate, are related to each other and their values must be in a specific limited range for the sound welding. These correlations and the ranges are dependent up on the kind and size of wire, shielding gas, joint shape and fitness. To determine these relationships, extensive welding experiments were performed. The experimental data were processed using several information processing technologies. The regression method was used to determine the relationship between current voltage, and deposition rate. When a joint is inclined, the weld bead should be confined to a the limited size, inorder to avoid undercut as well as overlap due to flowing down of molten metal by gravity. The dependency of the limited weld size which is defined as the critical deposited area on various factors such as the horizontally and vertically inclined angle of the joint, skewed angle of the joint, up or down welding direction and weaving was investigated through a number of welding experiments. On the basis of this result, an ANN system was developed to estimate the critical deposited area. The ANN system consists of a 4 layer structure and uses an error back propagation learning algorithm. The estimated values of the ANN were validated using experimental values.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1121-1129
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• 1988

An economic and efficient system for measuring drop sizes was developed. Pattern recognition technique was used with conventional oil-bath sampling and photographic method. The system was designed to measure and count relatively large number of drops in a very short time, and also to filter out abnormal images such as drops in contact or overlap as well as odd-shaped foreign materials. In this measuring system, most important error originates from the process of converting the original image to the binary image. If the photograph contains a large number of spray drops, the relative size of the pixel to the drops is not infinitesimally small; thus the proper choice of threshold level to convert the original image to the binary image becomes very important. In present case, most of the images lay in one of the two separate bands of brightness level and the arithmetic mean of the most popular brightness levels from each band was chosen as the threshold level. Present image processing system reduces the subjective error by the observers in counting and measuring drops and turns out to be substantially effective. The processing time can be further reduced by improving the hardware system concerned with the digital image coding.