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Search Results: 1 - 10 of 27607 matches for " Sang Wook Lee "
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Numerical Estimation of the Uneven Wear of Passenger Car Tires  [PDF]
Sang Wook Lee, Kyoung Moon Jeong, Kee Woon Kim, Jang Hyeon Kim
World Journal of Engineering and Technology (WJET) , 2018, DOI: 10.4236/wjet.2018.64051
Abstract: Tire wear is a very complicated phenomenon that is influenced by various factors such as tire material, structure, vehicle and road conditions. In order to evaluate tire wear, a method for measuring tire wear using the intensity of reflected light was presented[1]. It comprises applying a single layer of reflected paint to a tread surface by spraying, and then measuring the intensity of light reflected from a matrix of blocks on the unworn tire. In this paper, a numerical technique for predicting the uneven wear of passenger car tire is presented. The uneven tire wear produced in wheel alignment condition with vehicle speed, camber angle, and toe angle is predicted by the frictional dynamic rolling analysis of 3D patterned tire model. The proposed numerical technique is illustrated through the method of paint testing the wear on the tread surface of a tire.
Multi-Projector Color Structured-Light Vision
Changsoo Je,Kwang Hee Lee,Sang Wook Lee
Computer Science , 2015, DOI: 10.1016/j.image.2013.05.005
Abstract: Research interest in rapid structured-light imaging has grown increasingly for the modeling of moving objects, and a number of methods have been suggested for the range capture in a single video frame. The imaging area of a 3D object using a single projector is restricted since the structured light is projected only onto a limited area of the object surface. Employing additional projectors to broaden the imaging area is a challenging problem since simultaneous projection of multiple patterns results in their superposition in the light-intersected areas and the recognition of original patterns is by no means trivial. This paper presents a novel method of multi-projector color structured-light vision based on projector-camera triangulation. By analyzing the behavior of superposed-light colors in a chromaticity domain, we show that the original light colors cannot be properly extracted by the conventional direct estimation. We disambiguate multiple projectors by multiplexing the orientations of projector patterns so that the superposed patterns can be separated by explicit derivative computations. Experimental studies are carried out to demonstrate the validity of the presented method. The proposed method increases the efficiency of range acquisition compared to conventional active stereo using multiple projectors.
Color-Stripe Structured Light Robust to Surface Color and Discontinuity
Kwang Hee Lee,Changsoo Je,Sang Wook Lee
Computer Science , 2015, DOI: 10.1007/978-3-540-76390-1_50
Abstract: Multiple color stripes have been employed for structured light-based rapid range imaging to increase the number of uniquely identifiable stripes. The use of multiple color stripes poses two problems: (1) object surface color may disturb the stripe color and (2) the number of adjacent stripes required for identifying a stripe may not be maintained near surface discontinuities such as occluding boundaries. In this paper, we present methods to alleviate those problems. Log-gradient filters are employed to reduce the influence of object colors, and color stripes in two and three directions are used to increase the chance of identifying correct stripes near surface discontinuities. Experimental results demonstrate the effectiveness of our methods.
Comparison of Depth Dose Distributions Using Cerenkov Fiber-Optic Dosimeter and Monte Carlo Simulation for HDR Brachytherapy  [PDF]
Sang Hun Shin, Young Beom Song, Mingeon Kim, Hye Jin Kim, Wook Jae Yoo, Kyoung Won Jang, Bongsoo Lee
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.48157
Abstract:
In this study, we fabricated a Cerenkov fiber-optic dosimeter (CFOD) without any scintillator to measure Cerenkov radiation signals owing to gamma-rays. The relative depth dose (RDD) distributions of Ir-192 HDR brachytherapy source were obtained by using the CFOD based on a subtraction method and the RDD curve was compared with the simulation result of Monte Carlo N-particle extended transport code (MCNPX). Finally, we demonstrated that the CFOD can be used to measure real-time dose information for HDR brachytherapy.
Biomolecular Nano-Flow-Sensor to Measure Near-Surface Flow
Lee Sang-Wook,Kinoshita Haruyuki,Noji Hiroyuki,Fujii Teruo
Nanoscale Research Letters , 2009,
Abstract: We have proposed and experimentally demonstrated that the measurement of the near-surface flow at the interface between a liquid and solid using a 10 nm-sized biomolecular motor of F1-ATPase as a nano-flow-sensor. For this purpose, we developed a microfluidic test-bed chip to precisely control the liquid flow acting on the F1-ATPase. In order to visualize the rotation of F1-ATPase, several hundreds nanometer-sized particle was immobilized at the rotational axis of F1-ATPase to enhance the rotation to be detected by optical microscopy. The rotational motion of F1-ATPase, which was immobilized on an inner surface of the test-bed chip, was measured to obtain the correlation between the near-surface flow and the rotation speed of F1-ATPase. As a result, we obtained the relationship that the rotation speed of F1-ATPase was linearly decelerated with increasing flow velocity. The mechanism of the correlation between the rotation speed and the near-surface flow remains unclear, however the concept to use biomolecule as a nano-flow-sensor was proofed successfully. (See supplementary material 1) Electronic supplementary material The online version of this article (doi:10.1007/s11671-009-9479-3) contains supplementary material, which is available to authorized users. Click here for file
Magnetic Control of Ferroelectric Polarization in a Self-formed Single Magnetoelectric Domain of Multiferroic Ba3NbFe3Si2O14
Nara Lee,Young Jai Choi,Sang-Wook Cheong
Physics , 2014, DOI: 10.1063/1.4866187
Abstract: We have discovered strong magnetoelectric (ME) effects in the single chiral-helical magnetic state of single-crystalline langasite Ba3NbFe3Si2O14 that is crystallographically chiral. The ferroelectric polarization, predominantly aligned along the a axis below the Neel temperature of ~27 K, changes in a highly non-linear fashion in the presence of in-plane magnetic fields (H) perpendicular to the a axis (H//b*). This ME effect as well as smaller ME effects in other directions exhibit no poling dependence, suggesting the presence of a self-formed single ME domain. In addition, these ME effects accompany no-measurable hysteresis, which is crucial for many technological applications.
The Effective Cross-sections of a Lensing-galaxy: Singular Isothermal Sphere with External Shear
Dong-Wook Lee,Sang-Joon Kim
Physics , 2014, DOI: 10.1093/mnras/stu970
Abstract: Numerical studies on the imaging and caustic properties of the singular isothermal sphere (SIS) under a wide range of external shear (from 0.0 to 2.0) are presented. Using a direct inverse-mapping formula for this lens system (Lee 2003), we investigate various lensing properties under both a low (i.e., {\gamma} < 1.0), and a high (i.e., {\gamma} > 1.0) shear case: image separations, total or individual magnifications, flux ratios of 2-images, maximum number of images, and lensing cross-sections. We systematically analyze the effective lensing cross-sections of double-lensing and quad-lensing systems based on the radio luminosity function obtained by Jodrell-VLA Astrometric Survey (JVAS) and Cosmic Lens ALL-Sky Survey (CLASS). We find that the limit of a survey selection bias (i.e., between a brighter- and a fainter-image) preferentially reduces the effective lensing cross-sections of 2-image lensing systems. By considering the effects of survey selection bias, we demonstrate that the long standing anomaly on the high Quads-to-Doubles ratios (i.e., JVAS & CLASS: 50% ~ 70%) can be explained by the moderate effective shear of 0.16 ~ 0.18, which is half of previous estimates. The derived inverse mapping formula could facilitate the SIS + shear lens model to be useful for galaxy-lensing simulations. *Key-words: Cosmology; Theory; Gravitational lens; Strong.
High-Contrast Color-Stripe Pattern for Rapid Structured-Light Range Imaging
Changsoo Je,Sang Wook Lee,Rae-Hong Park
Computer Science , 2015, DOI: 10.1007/978-3-540-24670-1_8
Abstract: For structured-light range imaging, color stripes can be used for increasing the number of distinguishable light patterns compared to binary BW stripes. Therefore, an appropriate use of color patterns can reduce the number of light projections and range imaging is achievable in single video frame or in "one shot". On the other hand, the reliability and range resolution attainable from color stripes is generally lower than those from multiply projected binary BW patterns since color contrast is affected by object color reflectance and ambient light. This paper presents new methods for selecting stripe colors and designing multiple-stripe patterns for "one-shot" and "two-shot" imaging. We show that maximizing color contrast between the stripes in one-shot imaging reduces the ambiguities resulting from colored object surfaces and limitations in sensor/projector resolution. Two-shot imaging adds an extra video frame and maximizes the color contrast between the first and second video frames to diminish the ambiguities even further. Experimental results demonstrate the effectiveness of the presented one-shot and two-shot color-stripe imaging schemes.
Color-Phase Analysis for Sinusoidal Structured Light in Rapid Range Imaging
Changsoo Je,Sang Wook Lee,Rae-Hong Park
Computer Science , 2015,
Abstract: Active range sensing using structured-light is the most accurate and reliable method for obtaining 3D information. However, most of the work has been limited to range sensing of static objects, and range sensing of dynamic (moving or deforming) objects has been investigated recently only by a few researchers. Sinusoidal structured-light is one of the well-known optical methods for 3D measurement. In this paper, we present a novel method for rapid high-resolution range imaging using color sinusoidal pattern. We consider the real-world problem of nonlinearity and color-band crosstalk in the color light projector and color camera, and present methods for accurate recovery of color-phase. For high-resolution ranging, we use high-frequency patterns and describe new unwrapping algorithms for reliable range recovery. The experimental results demonstrate the effectiveness of our methods.
Measurement of Gamma-Rays Induced Luminescence Generated in a Sapphire Based Fiber-Optic Radiation Sensor  [PDF]
Young Beom Song, Kyoung Won Jang, Hye Jin Kim, Dong Eun Lee, Mingeon Kim, Sang Hun Shin, Wook Jae Yoo, Bongsoo Lee
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.48158
Abstract:
In this study, we fabricated a sapphire based fiber-optic radiation sensor. To evaluate the fiber- optic radiation sensor, we measured the spectrum and intensity of the luminescence generated from the fiber-optic radiation sensor according to the thickness of the PMMA block by irradiation of gamma rays emitted from a Co-60 source. And the result was compared with the value calculated from the formula of Lambert-Beer.
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