• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.7-10
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• 2002

A novel two-phase PIV algorithm using a single camera has been proposed, which introduces a method of image-separation into respective phase images, and is applied to freely rising single bubble. Gas bubble, tracer particle and background each have different gray intensity ranges on the same image frame when reflection and dispersion in the phase interface are intrinsically eliminated by optical filters and fluorescent material. Further, the signals of the two phases do not interfere with each other. Gas phase velocities are obtained from the separated bubble image by applying the two-frame PTV. On the other hand, liquid phase velocities are obtained from the tracer particle image by applying the cross-correlation algorithm. Moreover, in order to increase the SNR (signal-to-noise ratio) of the cross-correlation of tracer particle image, image enhancement is employed.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.1
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• pp.50-57
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• 2005

We present a simple and effective method of face and facial feature detection under pose variation of user face in complex background for the human-robot interaction. Our approach is a flexible method that can be performed in both color and gray facial image and is also feasible for detecting facial features in quasi real-time. Based on the characteristics of the intensity of neighborhood area of facial features, new directional template for facial feature is defined. From applying this template to input facial image, novel edge-like blob map (EBM) with multiple intensity strengths is constructed. Regardless of color information of input image, using this map and conditions for facial characteristics, we show that the locations of face and its features - i.e., two eyes and a mouth-can be successfully estimated. Without the information of facial area boundary, final candidate face region is determined by both obtained locations of facial features and weighted correlation values with standard facial templates. Experimental results from many color images and well-known gray level face database images authorize the usefulness of proposed algorithm.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.65-71
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• 2014

Atmospheric plasma spraying (APS) is world-widely used process in the automotive industry as a method to provide wear resistance coatings for engine cylinder bore, using various materials. The weight of engine blocks can be considerably decreased by removing cast iron liners, which can finally result in the improvement of fuel efficiency. In this study, five kinds of powder materials, 1.2C steel powder and 1.2C steel powder mixed with 5, 10, 15, 20 wt.%. molybdenum powder, were deposited by atmospheric plasma spraying in order to investigate the effect of molybdenum on the wear resistance of coatings. Microstructural analysis showed that molybdenum splats were well distributed in 1.2C steel matrix with intimate bonding. The molybdenum added coatings showed better tribological properties than 1.2C steel coating. However, above the 15 wt.%. blending fraction, wear resistance was somewhat degraded with poor roughness of worn surface due to the brittle fracture occurred in molybdenum splats. Consequently, compared to conventional liner material, gray cast iron, 10 wt. pct. molybdenum blended 1.2C steel coating showed much better tribological properties and therefore it looks very feasible to replace gray cast iron liner.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2C
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• pp.109-116
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• 2006

Many application scenarios of ultra-wideband(UWB) radio assume non-line-of-sigit(non-LoS) signal propagations. Through-material propagation of UWB signal introduces a distortion of the waveform as well as attenuation, which will introduce a decrease of the correlation coefficient between the correlator template and the received signal. A hypothesis test approach to selection of the template waveform for UWB rake receivers is posed. Linde-Buzo-Gray(LBG) algorithm is used to select the candidate waveforms which are used to setup the hypothesis test. The performance of the algorithm is tested using a set of indoor non-LoS propagation measurement data.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.653-657
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• 2004

The average bit error rate (HER) performance of a Gray coded arbitrary rectangular quadrature amplitude modulation (AR-QAM) signal with maximal ratio combining (MRC) diversity in an arbitrarily correlated Nakagami-m fading channel is derived and analyzed. The derived two types of general solutions are a simple closed-form and an integral form, depending on the types of the values (integer and non-integer) of the fading parameter. Using the derived equations in this paper, we analyzed the HER performances numerically based on the practical base station antenna configuration. The results show that MRC reception is a very effective scheme so far even though the combined signals are not independent each other because of the correlation values. The antenna height and separation of the MRC system relate to the correlation coefficient value between antennas, and go a long way with the diversity advantage. In particular, it is needed to be determined the antenna height that is carefully do for the diversity advantage because the correlation coefficient and the antenna height gain are contrary to each other from the aspect of the system performance. The expressions presented here can offer a convenient way to evaluate the exact HER performance of an arbitrary rectangular QAM signal with MRC diversity reception for various cases of practical interest on a correlated Nakagami fading channel.

• Progress in Medical Physics
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• v.33 no.4
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• pp.158-163
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• 2022

Purpose: We subjected scanning electron microscopic (SEM) images of the active layer of EBT3 film to texture analysis to determine the dose-response curve. Methods: Uncoated Gafchromic EBT3 films were prepared for direct surface SEM scanning. Absorbed doses of 0-20 Gy were delivered to the film's surface using a 6 MV TrueBeam STx photon beam. The film's surface was scanned using a SEM under 100× and 3,000× magnification. Four textural features (Homogeneity, Correlation, Contrast, and Energy) were calculated based on the gray level co-occurrence matrix (GLCM) using the SEM images corresponding to each dose. We used R-square to evaluate the linear relationship between delivered doses and textural features of the film's surface. Results: Correlation resulted in higher linearity and dose-response curve sensitivity than Homogeneity, Contrast, or Energy. The R-square value was 0.964 for correlation using 3,000× magnified SEM images with 9-pixel offsets. Dose verification was used to determine the difference between the prescribed and measured doses for 0, 5, 10, 15, and 20 Gy as 0.09, 1.96, -2.29, 0.17, and 0.08 Gy, respectively. Conclusions: Texture analysis can be used to accurately convert microscopic structural changes to the EBT3 film's surface into absorbed doses. Our proposed method is feasible and may improve the accuracy of film dosimetry used to protect patients from excess radiation exposure.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.823-830
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• 2010

This study was designed to examine the morphological measurement and characteristics of trabecullae based on femoral radiographic image for prediction of osteoporosis. Study subjects were 34 females (average age of 62.1 years) and 6 males (average age of 60.1 years), they were categorized into normal group and osteoporosis group in accordance with the T-score value. Measurement of the bone density of femoral bone was measured with DEXA(Dual Energy X-ray absorptiometry). ROI(Region of interests) was selected on femoral neck and trochanter. Characteristics of trabecullae was analyzed by using the skeletonization analysis of trabecular image. Morphological measurement was analyzed through femoral radiographic image in order to examine the correlation with osteoporosis. The result demonstrated statistically significant correlation between neck cortical thickness, shaft width, shaft cortical thickness, periphery, mean gray level and trabeculae area with BMD average (T-score) of femoral part. The results show that morphological measurement and characteristics of trabecullae based on femoral radiographic images for osteoporosis prediction could be effective.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.113-124
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• 1997

This work is performed to investigate the pressure drop and heat transfer characteristics in the air side of finned-tube heat exchanger for air conditioner. Experimental apparatus and method are described to simulate the heat exchanger performance by using the three times enlarged model. The pressure drop and heat transfer coefficient were measured and compared for the heat exchangers with a plane fin and a commercial strip fin. The measured data for the strip fin agree well with those of prototype within a few percentages. For the plane fin, the measured data had similar trend to Gray & Webb's correlation at high air velocity, however a new correlation is needed to give more accurate prediction at low air velocity. It is found that most heat was transferred around the front row of the two-row heat exchanger, and the ratio of thermal load at the front tube row was increased for decreasing air velocity.

• Biomedical Science Letters
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• v.10 no.2
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• pp.115-120
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• 2004

To investigate the correlation between the magnetic resonance imaging (MRI) of cerebral fat embolism that is induced by injecting oleic acid into 10 cats, and a pathologic diagnosis. Using a microcatheter, 30 ${mu}ell$ of oleic acid was injected into the internal carotid artery of 10 cats. MR T2-weighted image (T2WI), diffusion-weighted image (DWI) and Gadolinium-enhanced T1-weighted image (Gd-enhanced T1WI) were obtained after 30 minutes and 2 hours of embolization. After 30 minutes of the embolization, lesions of very high signal intensity were detected by T2WI in 6 cats, and of slightly high signal intensity in 2 cats; in the remaining 2 cats, signal intensity was normal. DWI showed lesions of very high intensity in 9 cats and of slightly high intensity in one cat. According to the findings of light microscopic examination, infarcted lesions mainly involved the gray matter, but also some white matter. A magnetic resonance imaging diagnosis for cerebral fat embolism that was induced by oleic acid through the internal carotid artery in cats showed high signal intensity on the T2WI and the DWI within an initial 2 hours, and with a well enhancement on the Gd-enhanced T1WI. Considering cellular edema, cerebrovascular injury and extracellular space widening, we assumed pathologically that cytotoxic and vasogenic edema exists at the same time.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.124-127
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• 2009

In this paper, we proposed automatically video colorization method with partial color sources in first frame. The input color sources are propagated to other gray pixels with the high correlation between two pixels. To robust again the errors in portion of the weak boundary, we calculate correlation between two pixels using dual-path comparison. Video colorization method should maintain the color connectivity between frames. Accordingly, we define reliability of primarily color by compare the color of neighborhood frames. We perform the color correction by blending neighboring color when the reliability of primarily color is low. We formalize this premise with energy function, and find the color to minimize the energy function. In this way, using property of video, we reduce the error caused by propagation and get result of natural changes between frames. Through simulation results, we show the proposed method derive a natural result more than previous method.