• Journal of Institute of Control, Robotics and Systems
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• v.14 no.3
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• pp.242-247
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• 2008

As an absolute positioning system, iGS is designed based on ultrasonic signals whose speed can be formulated clearly in terms of time and room temperature, which is utilized for a mobile robot localization. The iGS is composed of an RFID receiver and an ultra-sonic transmitter, where an RFID is designated to synchronize the transmitter and receiver of the ultrasonic signal. The traveling time of the ultrasonic signal has been used to calculate the distance between the iGS system and a beacon which is located at a pre-determined location. This paper suggests an effective operation method of iGS to estimate position of the mobile robot working in unstructured environment. To expand recognition range and to improve accuracy of the system, two strategies are proposed: utilization of beacons belonging to neighboring blocks and removal of the environment-reflected ultrasonic signals. As the results, the ubiquitous localization system based on iGS as a pseudo-satellite system has been developed successfully with a low cost, a high update rate, and relatively high precision.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04a
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• pp.39-42
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• 2004

The $Bi_2Sr_2Ca_nCu_{n+1}O_x$ superconducting thin film fabricated by using the sputtering method was compared with the $Bi_2Sr_2Ca_nCu_{n+1}O_x$ superconducting thin film fabricated by using the evaporation method. In doing the ultra-low deposition because each element can exist on the substrate surface, both the sputtering method and the evaporation method could easily fabricate single phase of the Bi2212 phase. Also, it is cofirmed that by optimizing the deposition condition, each single phase of the Bi2201 phase and the Bi2212 phase can be fabricated, the sticking coefficient of Bi element is clearly related to the changing of substrate temperature and the formation of the Bi2212 phase.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.12-12
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• 2010

By using scanning tunneling microscopy/spectroscopy (STM/S), we can make images of various physical properties in nanometer-scale spatial resolutions. Here, I demonstrate imaging of two electron-correlated subjects; screening and superconductivity by STM/S. The electrostatic potential around a charge is described with the Coulomb potential. When the charge is located in a metal, the potential is modified because of the free electrons in the host. The potential modification, called screening, is one of the fundamental phenomena in the condensed matter physics. Using low-temperature STM we have developed a method to measure electrostatic potential in high spatial and energy resolutions, and observed the potential around external charges screened by two-dimensional surface electronic states. Characteristic potential decay and the Friedel oscillation were clearly observed around the charges [1]. Superconductivity of nano-size materials, whose dimensions are comparable with the coherence length, is quite different from their bulk. We investigated superconductivity of ultra-thin Pb islands by directly measuring the superconducting gaps using STM. The obtained tunneling spectra exhibit a variation of zero bias conductance (ZBC) with a magnetic field, and spatial mappings of ZBC revealed the vortex formation [2]. Size dependence of the vortex formation will be discussed at the presentation.

• Vacuum Magazine
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• v.3 no.3
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• pp.15-18
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• 2016

In future wearable electronic systems, 3-dimensional (3D) devices have attracted much attention due to their high density integration and low-power functionality. Among 3D devices, gate-all-around (GAA) nanowire transistor provides superior gate controllability, resulting in suppressing short channel effect and other drawbacks in 2D metal-oxide-semiconductor field-effect transistor (MOSFET). Silicon nanowires (SiNWs) are the most promising building block for GAA structure device due to their compatibility with the current Si-based ultra large scale integration (ULSI) technology. Moreover, the theoretical limit for subthreshold swing (SS) of MOSFET is 60 mV/dec at room temperature, which causes the increase in Ioff current. To overcome theoretical limit for the SS, it is crucial that research into new types of device concepts should be performed. In our present studies, we have experimentally demonstrated feedback FET (FBFET) and tunnel FET (TFET) with sub-60 mV/dec based on SiNWs. Also, we fabricated SiNW based complementary TFET (c-TFET) and SiNW complementary metal-oxide-semiconductor (CMOS) inverter. Our research demonstrates the promising potential of SiNW electronic devices for future wearable electronic systems.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.27-30
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• 2008

Purpose: This research is that $V_2O_5$ cathode's composition is possible in low temperature. Methods: Transparent in visible spectra range and crystallographically amorphous $V_2O_5$ thin films were prepared by simple vacuum thermal evaporation on soda-lime-silica slide glass substrate. After annealing at 100$^{\circ}C$, 150$^{\circ}C$ and 200$^{\circ}C$ for 10 minutes in air, the surface morphology and the fracture-cross section of the films were investigated by field emission - scanning electron microscope. Transmittance in visible spectra range and surface roughness of the films were analyzed by ultra violet - visible spectrophotometer and scanning probe microscope, respectively. Results: As the increase of annealing temperature from 100$^{\circ}C$ to 150$^{\circ}C$ and 200$^{\circ}C$, transmittance of the $V_2O_5$ films decreased. Optical properties will be fully discussed on the basis of the surface morphological results. Conclusions: Optical transmissivity was superior in case of 100$^{\circ}C$, and could make amorphous $V_2O_5$ thin film that surface quality of thin film did homogeneity.

• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.222-229
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• 2024

The use of low-toxic, hypoallergenic, and environmentally friendly natural pigments has increased. With growing interest in health, research on natural extracts containing beneficial substances for the human body is actively underway. In this study, natural pigments were extracted from sprout barley using a solvent extraction method and CCD-RSM was used to optimize the extraction process. The experiment's independent variables included extraction temperature, alcohol/ultra-pure volume ratio, and extraction time. The response variables were set to achieve a target chromaticity (L = 45, a = -35, b = 45), and to maximize DPPH radical scavenging activity evaluating the antioxidant capacity. The statistical significance of the main effect, interaction effect, and effect on the response value was evaluated and analyzed through the F and P values for the regression equation variables calculated using RSM optimization. Additionally, the reliability of the experiment was also confirmed through the P values of the probability plot graph. The extraction conditions for optimizing the four reaction values are 76.1 vol.% alcohol/ultra pure water volume ratio, an extraction temperature of 52.9 ℃ , and an extraction time of 49.6 min. Under these conditions, the theoretical values of the reaction values are L = 45.4, a = -36.8, and b = 45.0 DPPH radical scavenging activity = 30.9%. When the actual experiment was conducted under these optimal extraction conditions and analyzed, the measured values were L = 46.2, a = -36.1, and b = 48.2, and antioxidant capacity = 31.1% with an average error rate of 2.9%.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.102-109
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• 2011

In this study, in order to develop ultra rapid hardening mortar(URHM) for tunnel repairs using bottom ash of low recycle ratio and Admixture as Eco concept, watertightness and durability properties of URHM on temperature condition of construction field were performed. Test result, seepage quantity and water absorption coefficient regarding watertightness of URHM were as in the following : series II > series I. Seepage quantity for the standard condition were smaller than low temperatures. all specimens were satisfied below 20g as standards of seepage quantity on KS F 4042. Because of the decrease of unit cement content by to replacement of blast furnace slag, the neutrlization resistance for durability properties was reduced. The result of alkali resistance and acide resistance, compressive strengths for specimens soaked in calcium hydroxide solution of seriesI were lower than compressive strengths for specimens not soaked. On the other hand, the case of series II show that the deterioration of compressive strengths for specimens was not almost showed. Compressive strengths of specimens soaked were similar with specimens not soaked except series II-C in $5^{\circ}C$. Therefore, specimens using both blast furnace slag and bottom ash were good in alkali resistance and acide resistance.

• Clean Technology
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• v.28 no.2
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• pp.117-122
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• 2022

This study developed and tested an ultra-low NO_x burner in an 80 kW combustion furnace. The experiment was conducted in an 80 kW single burner combustion furnace with changing the swirl numbers, total equivalence ratios, and primary/secondary oxidizer ratios. In this study, liquefied natural gas (LNG) was used as an auxiliary fuel to significantly reduce NO_x production. In a thermal power plant, the amount of NO_x generated during coal combustion is about 300 ppm. However, using the burner tested in this study, it was possible to reduce the amount of NO_x generated via LNG co-firing to 40 ppm. If the input amount of the primary oxidizer is enough for the gas to be completely combusted and the gas and coal are added simultaneously, the combusted gas forms a high-temperature region at the burner outlet and volatilizes the coal. As a result, the N contained in the devolatilized coal is discharged. Therefore, when the coal is subsequently burned, the amount of NO_x produced decreases because there is almost no N remaining in the coal. If a thermal power plant burner is developed based on the results of this study, it is expected that the NO_x generation will be significantly lower in the early stage of combustion.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.4
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• pp.87-96
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• 1995

The Electron/Hole Pair is generated when the activation energy produced by ultraviolet ray illuminates to the semiconductor and OH- ion produced by water photocleavage reacts with positive Hole. As a results, OH radical acting as strong oxidant is generated and then Photocatalytic oxidation reaction occurs. The photocatalytic oxidation can oxidate the non-degradable and hazardous organic substances such as pesticides and aromatic materials easier, safer and shorter than conventional water treatment process. So in this study, many factors influencing the oxidation of chlorophenols, such as inorganic electrolytes addition, change of oxygen and nitrogen atmosphere, temperature, pH, oxygen concentration, chlorophenol concentration, were throughly examined. According to the experiments observations, it is founded that the rate of chlorophenol oxidation follows a first-order reaction and the modified Langmuir-Hinshelwood relationship. And the photocatalytic oxidation occurs only when activation energy acting as Electron/Hole generation, oxygen acting as electron acceptor to prevent Electron/Hole recombination, $TiO_2$ powder acting as photocatalyst are present. The effects of variation of dissolved oxygen concentration, temperature and inorganic electrolytes concentration on 2-chlorophenol oxidation are negligible. And the lower the organic concentration, the higher the oxidation efficiency becomes. Therefore, the photocatalytic oxidation is much effective to oxidation of hazardous substances at very low concentration. The oxidation is effective in the range of 0.1 g/L-10 g/L of $TiO_2$. Finally when the ultra-violet ray is illuminated to $TiO_2$, the surface characteristics of $TiO_2$ change and Adsorption/Desorption reaction on $TiO_2$ surface occurs.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.220.2-220.2
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• 2011

Biodiesel and biodiesel blend fuel are receiving increasing attention as alternative fuels for diesel engines without substantial modifications. Biodiesel fuels and blending have been widely studied and applied in diesel engine because of biodiesel's lower sulfur, lower aromatic hydrocarbon and higher oxygen content. Biodiesels have the potential to be oxidized in different condition. It has reported that oxidation deterioration of biodiesel is different in the condition of storage and oxidation causes chemical property change of methyl esters. Sunlight intensity, temperature, material of container and contact surface with oxygen are key dominant factors accelerating oxidation deterioration. In this study, we chose temperature among key oxidation conditions and metal container filled with biodiesel was heated at about $110^{\circ}C$ for 10 days in order to accelerate oxidation deterioration. To better understand the effect of biodiesel blends on emission, steady state tests were conducted on a heavy duty diesel engine. The engine was fueled with Ultra Low Sulphur Diesel(ULSD), a blend of 10% and 20%(BD10, BD20) on volumetric basis, equipped with a common rail direct injection system and turbocharger, lives up to the requirements of EURO 3. The experimental results show that the blend fuel of normal biodiesel with BD10 and BD20 increased NOx. The result of PM was similar to diesel fuel on BD10, but the result of PM on BD20 was increased about 63% more than its of diesel. The blend fuel of Oxidation biodiesel with BD10 and BD20 increased NOx as the results of normal biodiesel. But PM was all increased on BD10 and BD20. Especially THC was extremely increased when test fuel contains biodiesel about 140% more than its of diesel. Through this study, we knew that oxidation deterioration of biodiesel affects emission of diesel engine.