• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.2
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• pp.89-93
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• 2017

GaN single crystals were grown by controlling of various processing parameters such as growing temperature, V/III ratio and growing rate. We optimized thickness of bulk GaN single crystal by analyzing defect of surface and inside of the GaN single crystal for application to high brightness and power device. 2-inch bulk GaN single crystals were grown by HVPE (hydride vapor phase epitaxy) on sapphire and their thickness was 0.3~7.0 mm. Crystal structure of the grown bulk GaN was analyzed by XRD (X-ray diffraction). The surface characteristics of the grown bulk GaN were observed by OM (optical microscope) and SEM (scanning electron microscopy) with measuring EPD (etch pits density) of the GaN crystals.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.89-96
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• 2006

Recent ULSI and multilevel structure trends in microelectronic devices minimize the line width down to less than $0.25{\mu}m$, which results in high current densities in thin film interconnections. Under high current densities, an EM(electromigration) induced failure becomes one of the critical problems in a microelectronic device. This study is to improve thin film interconnection materials by investigating the EM characteristics in Ag, Cu, Au, and Al thin films, etc. EM resistance characteristics of Ag, Cu, Au, and Al thin films with high electrical conductivities were investigated by measuring the activation energies from the TTF (Time-to-Failure) analysis. Optical microscope and XPS (X-ray photoelectron spectroscopy) analysis were used for the failure analysis in thin films. Cu thin films showed relatively high activation energy for the electromigration. Thus Cu thin films may be potentially good candidate for the next choice of advanced thin film interconnection materials where high current density and good EM resitance are required. Passivated Al thin films showed the increased MTF(Mean-time-to-Failure) values, that is, the increased EM resistance characteristics due to the dielectric passivation effects at the interface between the dielectric overlayer and the thin film interconnection materials.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.3104-3104
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• 2001

The research described here was undertaken with the aim of monitoring, optimizing and ultimately controlling the production of heterofermentative microbes used as starters in the salami industry. The use of starter cultures in the fermented meats industry is a well-established technique used to shorten and standardize the ripening process, and to improve and control the organoleptic quality of the final product. Starter cultures are obtained by the submerged cultivation of suitable microorganisms in stirred, and sometimes aerated, fermenters where monitoring of key physiological parameters such as the concentration of biomass, substrates and metabolites suffers from the general lack of real-time measurement techniques applicable to aseptic processes. In this respect, the results of the present work are relevant to all submerged fermentation processes. Previous work on the application of on-line NIR spectroscopy to the lactic acid fermentation (Dosi et al. - Monreal NIR1995) had successfully used a system based on a measuring cell included in a circulation loop external to the fermenter. The fluid handling and sterility problems inherent in an external circulation system prompted us to explore the use of an in-line system where the NIR probe is immersed in the culture and is thus exposed to the hydrodynamic conditions of the stirred and aerated fluid. Aeration was expected to be a potential source of problems in view of the possible interference of air bubbles with the measurement device. The experimental set-up was based on an in-situ sterilizable NIR probe connected to the instrument by means of an optical fiber bundle. Preliminary work was carried out to identify and control potential interferences with the measurement, in particular the varying hydrodynamic conditions prevailing at the probe tip. We were successful in defining the operating conditions of the fermenter and the geometrical parameters of the probe (flow path, positioning, etc.) were the NIR readings were reliable and reproducible. The system thus defined was then used to construct and validate calibration curves for tile concentration of biomass, carbon source and major metabolites of two different microorganisms used as salami starters. Real-time measurement of such parameters coupled with the direct interfacing of the NIR instrument with the PC-based measurement and control system of the fermenter enabled the development of automated strategies for the interactive optimization of the starter production process.

• Journal of the Korean Institute of Gas
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• v.24 no.5
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• pp.10-19
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• 2020

Valve leak accidents in petrochemistry plants and gas utilities cause human and property damage. The main reason why happen gas inhalation, poisoning, fire and explosion accidents is gas valve leakage. To prevent gas leakage, inspectors check the facilities in the field. And they are at risk of gas leak accidents. So we applied IoT-based risk assessment, monitoring and automatic control system. It can detect both internal and external gas leakage, do real-time monitoring of industrial valve in the plant by using hybrid sensor. As the new safety management system for industrial valve is developed, it needs method to evaluate device performance and environmental components for the system. This study is about development of method to verify performance of the explosion-proofed hybrid sensing system include gas detector and optical fiber sensor supporting wire and wireless communication.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.5
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• pp.277-281
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• 2017

Lately rainfall characteristics that it rains a lot in a short space of time often occurs. Because of this meteorological phenomena, the flow rate and concentration of initial rainfall for runoff and combined sewer overflows are changed. In the case of this inlet fluctuation, the flotation method at high surface loading rate is suitable for water quality management. the flotation method is able to meet the removal rate requirements of water public zone in 5 to 10 min which is irelatively short period. For assessment and diagonision of flotation method, A/S ratio is applied until now. But unfortunately, this has some limits for evaluation standard for certification and assessment of technical diagnosis and operation. This is why there is different efficiency in the bubble distribution at the same A/S ratio. The velocity and time of floating is changed by the different bubble distributions. The floating time affects the plant volume because the time factor make size dicision. Therefore the charateristics of bubble distribution and floating time at the same A/S ratio is necessary to apply to evaluation standard for certification and assessment of technical diagnosis and operation. For generalization of the method in certification and assessment, the characteristics of bubble distribution was studied. Until recently, using the optical device and shooting live video, there are some analysis technology of the floating factors. But this kind of technology is influenced by the equipment. with this level of confidence about the results, it is difficult to apply to generalize. According this reasons, this study should be applied on experiment generalization of method about measurement of relation between bubble distribution and floating time.

• Science of Emotion and Sensibility
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• v.14 no.2
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• pp.221-226
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• 2011

Although diverse researches on sensing method of human movement have been performed, there are still many limitations to the existing methods. As a part of supplementing the limitations to the existing motion sensing methods, this study aimed to execute an exploratory examination on a POF-based sleeve-shaped motion sensor for less restrictive sensing of human movement. In this study, a set of POF-based motion sensor, which was embedded in a sleeve-shaped platform was devised, and a set of exploratory experiments was performed on the possibility of sensing of human movement as diverse as in daily life, through this device. The scope of this research was limited to an exploration on the possibility and basic elements of POF-based sleeve-shaped motion sensor, while the influence of sleeve patterns, those of wearer's somatotype, those of sewing method were not studied in this study. When compared to the pre-existing methods, the POF-based motion sensor platformed on sleeve in this study, which was purposively devised to be applied to the motion sensing clothing shows some beneficial characteristics : more sensitive measurement on human motion, low cost, no timely restriction in sensing, no request for gigantic apparatus and space for sensing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.699-704
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• 2018

One-dimensional nanostructures have attracted increasing attention because of their unique electronic, optical, optoelectrical, and electrochemical properties on account of their large surface-to-volume ratio and quantum confinement effect. Vertically grown nanowires have a large surface-to-volume ratio. The vapor-liquid-solid (VLS) process has attracted considerable attention for its self-alignment capability during the growth of nanostructures. In this study, vertically aligned silicon oxide nano-pillars were grown on Si\$SiO_2$(300 nm)\Pt substrates using two-zone thermal chemical vapor deposition system via the VLS process. The morphology and crystallographic properties of the grown silicon oxide nano-pillars were investigated by field emission scanning electron microscopy and transmission electron microscopy. The diameter and length of the grown silicon oxide nano-pillars were found to be dependent on the catalyst films. The body of the silicon oxide nano-pillars exhibited an amorphous phase, which is consisted with Si and O. The head of the silicon oxide nano-pillars was a crystalline phase, which is consisted with Si, O, Pt, and Ti. The vertical alignment of the silicon oxide nano-pillars was attributed to the preferred crystalline orientation of the catalyst Pt/Ti alloy. The vertically aligned silicon oxide nano-pillars are expected to be applied as a functional nano-material.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.339-344
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• 2014

Purpose: This study relates to the development of the day and night scope using the reflecting surface of a BS (beam splitting) prism. Methods: We have placed the LCD panel and the dot reticle generator to the top and bottom of the reflecting surface of the BS prism, and have placed a reflector, which is designed to doublet type, in the front of the BS prism. Doing so, we have developed a new type of day and night scope, which is able to image the virtual image of dot reticle from the dot reticle generator to the direction of the observer, to make the observer survey the peripheral information of the outside target by 1x magnification, and to make the observer survey the image of the LCD panel directly. Results: We could develope a new type of day and night scope, which has the function of night scope as thermal image display device at night time and the function of day scope as dot sight at day time, by letting the reflective surface of the BS prism have the role of dot sight which reflects the dot reticle and have the role of reflective optical system by which the observer surveys the night thermal image displayed in LCD panel. Conclusions: In this study, we have developed the new type of day and night scope which is able to play the role of the day or night scope selectively, combining the existing dot sight and the existing night scope by using the BS prism. By doing so, we could design and fabricate the new type of day and night scope with the BS prism which can further increase the rapidity of firing and provide more convenience in the mounting of a firearm than the detachable combination of an existing dot sight and an existing night scope.

• Korean Journal of Materials Research
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• v.30 no.4
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• pp.204-210
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• 2020

ZnO thin films are of considerable interest because they can be customized by various coating technologies to have high electrical conductivity and high visible light transmittance. Therefore, ZnO thin films can be applied to various optoelectronic device applications such as transparent conducting thin films, solar cells and displays. In this study, ZnO rod and thin films are fabricated using aqueous chemical bath deposition (CBD), which is a low-cost method at low temperatures, and environmentally friendly. To investigate the structural, electrical and optical properties of ZnO for the presence of citrate ion, which can significantly affect crystal form of ZnO, various amounts of the citrate ion are added to the aqueous CBD ZnO reaction bath. As a result, ZnO crystals show a nanorod form without citrate, but a continuous thin film when citrate is above a certain concentration. In addition, as the citrate concentration increases, the electrical conductivity of the ZnO thin films increases, and is almost unchanged above a certain citrate concentration. Cu(In,Ga)Se₂ (CIGS) solar cell substrates are used to evaluate whether aqueous CBD ZnO thin films can be applicable to real devices. The performance of aqueous CBD ZnO thin films shows performance similar to that of a sputter-deposited ZnO:Al thin film as top transparent electrodes of CIGS solar cells.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.3
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• pp.1-12
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• 2011

Large-sized multi-touch screen is usually made using infrared rays. That is because it has technical constraints or cost problems to make the screen with the other ways using such as existing resistive overlays, capacitive overlay, or acoustic wave. Using infrared rays to make multi-touch screen is easy, but is likely to have technical limits to be implemented. To make up for these technical problems, two other methods were suggested through Surface project, which is a next generation user-interface concept of Microsoft. One is Frustrated Total Internal Reflection (FTIR) which uses infrared cameras, the other is Diffuse Illumination (DI). FTIR and DI are easy to be implemented in large screens and are not influenced by the number of touch points. Although FTIR method has an advantage in detecting touch-points, it also has lots of disadvantages such as screen size limit, quality of the materials, the module for infrared LED arrays, and high consuming power. On the other hand, DI method has difficulty in detecting touch-points because of it's structural problems but makes it possible to solve the problem of FTIR. In this thesis, we study the algorithms for effectively correcting the distort phenomenon of optical lens, and image processing algorithms in order to solve the touch detecting problem of the original DI method. Moreover, we suggest calibration algorithms for improving the accuracy of multi-touch, and a new tracking technique for accurate movement and gesture of the touch device. To verify our approaches, we implemented a table-based multi touch screen.