• Journal of IKEEE
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• v.15 no.2
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• pp.149-156
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• 2011

In this paper, a new discrete variable structure controller based on a new sliding surface and discrete version of the disturbance observer is suggested for the control of uncertain linear systems. The reaching phase is completely removed by introducing a new proposed sliding surface. The discrete version of the disturbance observer is derived for the effective compensation of the effect of uncertainties and disturbances. A corresponding control input with the disturbance compensation is selected to guarantee the quasi sliding mode on the predetermined sliding surface for guaranteeing the designed output in the sliding surface from any initial condition to the origin for all the parameter variations and disturbances. By using Lyapunov function, the closed loop stability and the existence condition of the quasi sliding mode is proved. Finally, an illustrative example is presented to show the effectiveness of the algorithm.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.375-383
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• 2020

This study aimed to propose a methodology for quantitatively analyzing problems resulting from the performance and combination of the ionization chamber when using an automatic exposure control (AEC) and to optimize the performance of the digital radiography (DR). In the experimental method, the X-ray quality of the parameters used for the examination of the abdomen and pelvis was evaluated by percentage average error (PAE) and half value layer (HVL). Then, the stability of the radiation output and the image quality were analyzed by calculating the entrance surface dose (ESD) and entropy when the three ionization chambers were combined. As a result, all of the X-ray quality of the digital radiography used in the experiment showed a percentage average error and a half value layer in the normal range. The entrance surface dose increased in proportion to the combination of chambers, and entropy increased in proportion to the combination of ionization chambers except when three chambers were combined. In conclusion, analysis using entrance surface dose and entropy was found to be a useful method for evaluating the performance and combination problems of the ionization chamber, and the optimal performance of the digital radiography can be maintained when two or less ionization chambers are combined.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.592.1-592
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• 2001

Conventional intraoral radiography continues to be the most widely used for the diagnosis of dental caries. But conventional intraoral film has several shortcomings, including processing error, increased radiation dose, etc. Recently, various digital radiographs substitude for conventional radiography to overcome these disadvantages. The digital radiographies are numerous advantages, including elimination of processing errors, lower radiation dose, image quality enhancements such as contrast and density modulation.(omitted)

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.3 no.2
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• pp.87-90
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• 2007

It's important that detect early caries of deciduous and permanent teeth to prevent dental caries and prevserve teeth, especially on proximal surface of deciduous teeth. The reason is that their prominent pulp horn lead to pulp treatment easily due to rapid caries progression. There are conventional exploring, visual inspection and radiographic exam for early caries detection. But, the standard method for diagnosing dental caries is subject and cavitation may be accelerated during exploring procedure. Caries can be diagnosed up to 40% mineral loss with radiograph. $DIFOTI^{(R)}$ (Digital Imaging Fiber-Optic TransIllumination) is diagnostic imaging system for early caries detection using fiber-optic illumination. It is possible that remineralize the tooth surface without tooth preparation and conserve the tooth structure by using $DIFOTI^{(R)}$.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.106-113
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• 2011

We describe a single shot off-axis digital holography based on a Mach-Zehnder interferometic scheme for measuring temperature distribution of a microheater. The proposed scheme has the capability of reconstructing object phase image which is dependent of the temperature distribution in real time. Experimental results shows that there is a moderate linear relationship between the measured phase and temperature in the range of $20^{\circ}C$ to $60^{\circ}C$. We expect that the proposed system can provide a very reliable and fast solution in various surface temperature distribution measurement applications.

• Journal of Fashion Business
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• v.16 no.6
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• pp.36-51
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• 2012

Quilting, a technique to join two or more layers of fabrics, has long been used in the textile and fashion sectors. To evaluate dimensional effect of quilting that changes according to the characteristics of fabrics, 3D scanning method is employed in this study. Goal of this study is to interpret how fabric's composition, stiffness, thickness, and weight affect the appearance when quilted fabrics are used in a garment. Surface reconstruction method based on 3D scanning is used as a research method to evaluate the changing appearance depending on the material properties quantitatively with the quilting method. Besides, exemplary virtual clothing is realized through a virtual quilting method in 3D digital clothing system based on the properties of fabrics.

• International Journal of Contents
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• v.16 no.2
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• pp.41-50
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• 2020

This paper presents Reflectance Transformation Imaging (RTI) as a tool to support the study of paintings and authentication. Manufacturing techniques of the artist are reviewed through the comparison between liberal perspectives and digital imaging techniques. In this study, RTI was applied to focus on the detailed textural information of eight paintings by Korean artist Lee Ji-ho. The RTI result visualizes shallow reliefs of brush strokes and different mediums on the surface technically enhanced through imaging filters, and these morphological textures on the surface act as a key factor in understanding the characteristics of the artist. The surface morphology and art criticism work as qualitative indicators to analyze the change of artistic techniques through time, and the usage of different mediums. The results of this study confirm that the RTI technique can be used as an analysis device in the study of paintings.

• Journal of Information Display
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• v.8 no.1
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• pp.14-17
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• 2007

The toner type paper-like display (PLD) has been developed with two polymer particles having opposite polarity composed of polymer, colorant and external additives (nano-sized silica). Nano-sized silica with triboelectric charge was used for the charge control agent (CCA) and influenced on the electrostatic properties of the silica-coated polymer particles. The surface morphology and the cohesiveness of silica-coated polymer particles were changed with the silica coating time. From these results, it was verified that the PLD cell using silica-coated particles (200 seconds) shows a good white appearance and low driving voltage.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.457-458
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• 2002

The fractal dimension is the characteristics that can quantitatively define the irregularity in natural. It is useful in describing the morphology or various rubbed surface for hydraulic piston motor instead of the stylus profiling method. But fractal parameters had not constructed on the morphological characteristic or rubbed surface because of the insufficient knowledge about a conception of fractal dimension. In this study, for the purpose or applying fractal I parameters practically, we have suggested way to establish the morphological characteristic of rubbed surface with fractal parameters, and we carried out an experiment on the lubricant friction and wear by using Ball-ON-Disk type tester. Materials were the brass and the bronze which are used to slipper-pad in the hydraulic piston motor. We searched for fractal parameters or surface structure with the digital image processing, Surface fractal dimension can be determined by sum of intensity difference of surface pixel. Using the image processing and fractal parameters for rubbed surface in the friction and wear test, morphology of rubbed sur race can be effectively obtained by fractal dimensions.

• Korean Journal of Remote Sensing
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• v.29 no.1
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• pp.81-94
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• 2013

The Radar altimeter transmits radio signals to the surface, receives the backscattered signals and measures the distance between the airplane and the nadir surface. The measurements of radar altimeter are affected by various factors on the surface below the aircraft. This study performed flight campaigns in June 2012 and acquired raw data from radar altimeter, LiDAR and other sensors. Based on the LiDAR DSM (Digital Surface Model) as a reference data, the characteristics of radar altimeter were analyzed in the respect of range and surface area affecting on the receiving power of the radar altimeter. Consequently, the radar altimeter was strongly affected by the surface area within beam width and reflectivity related to RCS (Radar Cross Section) rather than range.