• Journal of Power Electronics
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• v.14 no.2
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• pp.302-314
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• 2014

Due to advancements in power electronics and inverter topologies, the current controlled multilevel voltage-source pulse width modulated (PWM) inverter is usually preferred for accurate control, quick response and high dynamic performance. A multilevel topology approach is found to be best suited for overcoming many problems arising from the use of high power converters. This paper presents a comprehensive review and comparative study of several current control (CC) techniques for multilevel inverters with a special emphasis on various approaches of the hysteresis current controller. Since the hysteresis CC technique poses a problem of variable switching frequency, a ramp-comparator controller and a predictive controller to attain constant switching frequency are described along with its quantitative comparison. Furthermore, various methods have been reviewed to achieve hysteresis current control PWM with constant switching frequency operation. This paper complies various guidelines to choose a particular method suitable for application at a given power level, switching frequency and dynamic response.

• Advances in nano research
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• v.1 no.1
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• pp.43-58
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• 2013

Zinc oxide (ZnO) is a unique semiconductor material that exhibits numerous useful properties for dye-sensitized solar cells (DSSCs) and other applications. Various thin-film growth techniques have been used to produce nanowires, nanorods, nanotubes, nanotips, nanosheets, nanobelts and terapods of ZnO. These unique nanostructures unambiguously demonstrate that ZnO probably has the richest family of nanostructures among all materials, both in structures and in properties. The nanostructures could have novel applications in solar cells, optoelectronics, sensors, transducers and biomedical sciences. This article reviews the various nanostructures of ZnO grown by various techniques and their application in DSSCs. The application of ZnO nanowires, nanorods in DSSCs became outstanding, providing a direct pathway to the anode for photo-generated electrons thereby suppressing carrier recombination. This is a novel characteristic which increases the efficiency of ZnO based dye-sensitized solar cells.

• International Journal of Aerospace System Engineering
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• v.7 no.1
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• pp.7-15
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• 2020

In this paper the crack growth, modeling, and simulation of the stiffened and un-stiffened cracked panels presented using commercially available finite element software packages. Computation of stresses and convergence of stress intensity factor for single edge notch (SEN) specimens carried out using the finite element method (FEM) and extended finite element method (XFEM) and compared with an analytical solution. XFEM techniques like cohesive segment method and LEFM using virtual crack closure technique (VCCT), used for crack growth analysis and presented results for un-stiffened and stiffened panels considering various crack domain. The non-linear analysis considering both geometric and material non-linearity on stiffened panels with various stringers like a blade, L, inverted T and Z sections the results were presented. Arrived at the optimum stringer section type for the considered panel under axial loading from the numerical analysis.

• Fashion & Textile Research Journal
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• v.8 no.2
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• pp.214-224
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• 2006

Computer graphics mean a reproduction of various information through image processing or the technology that is widely thought in makeup areas also, recently. Especially, Adobe Illustrator, unlike Adobe Photoshop used in image editing and correction, is software suitable for image drawing and reproducing beauty makeup. Beauty makeup is a work adorning human body to fit to the aesthetic standard in that period, and is a plastic art expressing shapes, colors and textures using design elements. Adobe Illustrator is a 2D graphics designing images using shapes having plane colors. In this study I studied techniques reproducing each element of contours and colors of beauty makeup through Adobe Illustrator CS. In other words, I have prepared a reference data by studying techniques reproducing beauty makeup using Adobe Illustrator CS. In this study, though, I couldn't try various things, because I limited facial contour and skin color to only one kind. Therefore, I hope, in the future, others can expand the ethnics of using Adobe Illustrator in more enriched ways by working on various facial contours and skin colors.

• Journal of Korea Society of Digital Industry and Information Management
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• v.16 no.1
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• pp.55-65
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• 2020

With the development of display hardware, image interpolation techniques have been used in various fields such as image zooming and medical imaging. Traditional image interpolation methods, such as bi-linear interpolation, bi-cubic interpolation and edge direction-based interpolation, perform interpolation in the spatial domain. Recently, interpolation techniques in the discrete cosine transform or wavelet domain are also proposed. Using these various existing interpolation methods and machine learning, we propose decision tree classification-based image interpolation methods. In other words, this paper is about the method of adaptively applying various existing interpolation methods, not the interpolation method itself. To obtain the decision model, we used Weka's J48 library with the C4.5 decision tree algorithm. The proposed method first constructs attribute set and select classes that means interpolation methods for classification model. And after training, interpolation is performed using different interpolation methods according to attributes characteristics. Simulation results show that the proposed method yields reasonable performance.

• The Journal of the Korean dental association
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• v.55 no.3
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• pp.240-248
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• 2017

A keratinized gingiva is important to the natural teeth and it is more essential to the health of the peri-implant mucosa of the implants. There are various surgical methods to restore a keratinized gingiva. First, a clinician could utilize apically positioned flap operation. This flap operation technique could be used as a full or partial thickness. If there is little keratinized gingival tissue available for the apically positioned flap operation, free gingival grafting should be used. Its technique sensitivity is relatively high, but using various surgical techniques and disciplines makes it simple and have the good predictability. There have been many considerations for those surgical techniques. Clinicians who treat for periodontitis or operate implant surgeries have to know the considerations and surgical methods.

• Applied Science and Convergence Technology
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• v.27 no.5
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• pp.79-85
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• 2018

Many studies have been conducted on large-scale graphene synthesis by chemical vapor deposition. Furthermore, numerous researchers have attempted to develop processes that can continuously fabricate uniform and high-quality graphene. To compete with other types of carbon materials (carbon black, carbon fiber, carbon nanotubes, and so on), various factors, such as price, mass manufacturing capability, and quality, are crucial. Thus, in this study, we examine various large-scale graphene production methods focusing on cost competitiveness and productivity improvements for applications in various fields.

• Membrane and Water Treatment
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• v.6 no.4
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• pp.323-337
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• 2015

Membrane Fouling was considered as major drawback in various industrial applications. Thus, this paper reviews the surface modification of polyethersulfone (PES) membranes for antifouling performance. Various modification techniques clearly indicate that hydrophilicity has to improve on the PES membrane surface. Moreover, the mechanism of fouling reduction with corresponds to various modification methods is widely discussed. Incorporation of hydrophilic functional groups on PES membrane surface enhances the surface free energy thereby which reduces the fouling. Characterization techniques adopted for the surface modified membranes was also discussed. These studies might be useful for the other researchers to utilize the modification technique for the applications of waste water treatment, chemical process industry and food industry.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.07a
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• pp.381-382
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• 2019

Recently, various search techniques using artificial intelligence techniques have been introduced. It is also possible to use the artificial intelligence to grasp customer propensity. Analyzing the clothes that customers usually wear, it is possible to analyze various colors such as favorite colors, patterns, and fashion styles. In this study, we use artificial intelligence technology to create an application that distinguish between adults and children by combining various factors such as shape, type, color and size of human clothes. Through this, it will be possible to utilize it in a living area where children can be protected in advance by grasping the intrusion of unauthorized adults in the living area where children live mainly. In addition, in the future, we can obtain good results to detect stranger adult person if we apply this experimental result to the detection system using clothing information.

• Sleep Medicine and Psychophysiology
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• v.1 no.2
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• pp.125-144
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• 1994

Recently excessive daytime sleepiness was found to have relations with various social, occupational, and health problems. This condition is common symptom of several sleep disorders, among which sleep apnea syndrome is most contributive. It is essential to assess daytime sleepiness exactly for the diagnosis of such sleep disorders. Multiple sleep latency test which is a valid and objective measurement technique of sleepiness is time and cost consuming, and so there is increasing need of scales measuring general level of daytime sleepiness which are quick and simple to perform for clinical and research purpose. And also, there have been a lot of sleep researches viewing sleep as a chronobiological process, especially in the study of circadian type of shift workers. In these studies they used various techniques of multiple demensions to assess sleepiness or circadian rhythm which concerns various psychological variables. Of these measurement techniques circadian type questionnaires might have some problems in their psychometric properties. So some of these morningness-eveningness questionnaires have been revised and more valid scales are being suggested by different authors. The author briefly reviewed various measurement techniques of sleepiness and circadian rhythm and introduced recently developed scales which are more valid allegedly, and finally discussed psychometric properties of these morningness-eveningness questionnaires.