• Ocean Systems Engineering
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• v.9 no.4
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• pp.391-407
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• 2019

Tracking the location (position) of a surface or underwater marine vehicle is important as part of guidance and navigation. While the Global Positioning System (GPS) works well in an open sea environment but its use is limited whenever testing scaled-down models of such vehicles in the laboratory environment. This paper presents the design, development and implementation of a low energy ultrasonic augmented single beacon-based localization technique suitable for such requirements. The strategy consists of applying Extended Kalman Filter (EKF) to achieve location tracking from basic dynamic distance measurements of the moving model from a fixed beacon, while on-board motion sensor measures heading angle and velocity. Iterative application of the Extended Kalman Filter yields x and y co-ordinate positions of the moving model. Tests performed on a free-running ship model in a wave basin facility of dimension 30 m by 30 m by 3 m water depth validate the proposed model. The test results show quick convergence with an error of few centimeters in the estimated position of the ship model. The proposed technique has application in the real field scenario by replacing the ultrasonic sensor with industrial grade long range acoustic modem. As compared with the existing systems such as LBL, SBL, USBL and others localization techniques, the proposed technique can save deployment cost and also cut the cost on number of acoustic modems involved.

• The Korean Journal of Ceramics
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• v.1 no.4
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• pp.191-196
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• 1995

Using sol-gel processing method, thin films of lathanum modified lead titanate(PLT) on Corning 7059 glass were prepared. A differential thermal analysis (DTA/TG) curve of gel powder and infrared spectra (FT-IR) of the films were measured to estimate residual organices in them. The heat-treated films were characterized by X-ray diffraction(XRD). Microstructures of the films were observed by a scanning electron microscope (SEM). Optical properties of the films were determined by a UV-VIS spectrophotometer. The waveguiding properties and optical attenuation were measured with the end coupling method and the cut back method. Effects of the drying conditions on the transmittance and the propagation loss of the films were investigated. Experimemtal results showed that the content of residual organics in the film decreased as the drying temperature of the film increased. As the La content of the film increased, the grain size decreased and the transmittance increased. The transmittances of the films increased with the increasing of the drying temperature. The propagation losses in the film decreased as the drying temperature increased.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.75.1-75.1
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• 2019

The universe has been ionized in the post-reionization by several photon contributors. The dominant source to produce the hydrogen ionizing photons is not revealed so far. Faint quasars have been expected to generate UV photon budgets required to maintain ionization state of universe. Observational limits, however, hinder to discover them despite their higher number density than bright one. Consequently, the influence of faint quasars on post-reionization are not considered sufficiently. Therefore, a survey to find faint quasars at z ~ 5 is crucial to determine the main ionizing source in the post-reionization era. Deep images from the Hyper Suprime-Cam Subaru Strategic Program (HSC SSP) allow us to search for quasar swith low luminosities in the ELAIS-N1 field. J band information are obtained by the Infrared Medium-deep Survey (IMS) and the UKIRT Infrared Deep Sky Survey (UKIDSS) - Deep ExtragalacticSurvey (DXS). Faint quasar candidates were selected from several multi-band color cut criteria based on simulated quasars on color-color diagram. To choose the reliable candidates with possible Lyman break, we have performed medium-bands observations. Whether a candidate is a quasar or a dwarf star contamination was decided by results from chi-square minimization of quasar/dwarf model fitting. Spectroscopic follow-up observations confirm three quasars at z ~ 5. 100% spectral confirmation success rate implies that the medium-band observations effectively select faint quasars with strong Lyman alpha emission.

• Clean Technology
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• v.11 no.3
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• pp.123-128
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• 2005

Among various metal oxides semiconductors, $TiO_2$ is the most studied semiconductor for environmental clean-up applications due to its unique ability in photocatalyzing various organic contaminants, its chemical inertness, and nontoxicity. $TiO_2$, however, has a few drawbacks to be solved such as reactivity mainly working under ultraviolet irradiation (${\lambda}$ < 387 nm) and electron - hole recombination on $TiO_2$. In this study, to extend the absorption range of $TiO_2$ into the visible range and enhance electron - hole separation, we synthesized platinum (Pt) deposited $C-TiO_2$. The presence of Pt as an electron sink has been known to snhance the separation of photogenerated electron-hole pairs and induce the thermal decomposition. The characterization of as-synthesized $Pt-C-TiO_2$ was performed by Transmission Electron Microscopic (TEM), the Brunuer-Emmett-Teller (BET) method, X-ray Diffractometer (XRD), UV-vis spectrometer (UV-DRS), and X-ray Photoelectron Spectroscopy (XPS). In order to estimate the photocatalytic activity of the synthesized materials, the photoelectron Spectroscopy (XPS). In order to estimate the photocatalytic activity of the synthesized materials, the photodegradation experiment of an azo dye (Acid Red 44; $C_{10}H_7N=NC_{10}H_3(SO_3Na)_2OH$)was carried out by using an Xe arc lamp (300 W, Oriel). A 420 nm cut-off filter was used for visible light irradiation. From the results, Pt-deposited $C-TiO_2$ showed a far superior phothdegradation activity to Degussa P25, the commercial product under the irradiation of visible light and enhanced photocatalytic activity of visible-working $C-TiO_2$. This is a useful result into the application for the purification system of dye wastewater using visible energy of sun light.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.140-144
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• 2014

Co-(0.7 wt%) and Pr-(2.0, 3.5 or 5.0 wt%) doped cubic zirconia ($ZrO_2:Y_2O_3=50:50wt%$) single crystals grown by a skull melting method were heat-treated in $N_2$ at $1150^{\circ}C$ for 5 hrs. The brown colored as-grown single crystals were changed into either dark brownish green, greenish blue and light green color after the heat treatment. Before and after the heat treatment, the YSZ (yttria-stabilized zirconia) single crystals were cut for wafer form (${\phi}7.5mm{\times}t3mm$). The optical and structural properties were examined by UV-VIS spectrophotometer and X-ray diffraction. Absorption by $Co^{2+}$(${\fallingdotseq}589nm$: ${\Gamma}_8[^4A_2(^4F)]{\rightarrow}{\Gamma}_8+{\Gamma}_7[^4T_1(^4F)]$, ${\fallingdotseq}610nm$: ${\Gamma}_8[^4A_2(^4F)]{\rightarrow}{\Gamma}_8[^4T_1(^4F)]$], ${\fallingdotseq}661nm$: ${\Gamma}_8[^4A_2(^4F)]{\rightarrow}{\Gamma}_6[^4T_1(^4F)]$]) and $Pr^{3+}$(${\fallingdotseq}450nm$: ${^3}H{_4}-{^3}P{_2}$, ${\fallingdotseq}473nm$: ${^3}H{_4}{\rightarrow}{^3}P{_1}$, ${\fallingdotseq}484nm$: ${^3}H{_4}{\rightarrow}{^3}P{_0}$), change of ionization energy and lattice parameter were confirmed.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.400-405
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• 2015

Traditional anti-reflective (AR) coating films prepared using tetraethylorthosilicate (TEOS) as a precursor absorbs water easily in addition to having a weak abrasion resistance. To improve the transmittance, hydrophobicity and abrasion resistance of AR coating film, various AR coating films were prepared using methyltrimethoxysilane (MTMS) as a precursor in addition to introducing a fluoroalkylsilane, acid catalyst, base catalyst and acid-base two step catalyst. The prepared AR coating films were then characterized by UV-Vis spectroscopy, contact angle analyzer, atomic force microscope (AFM), pencil scratch hardness test and cross-cut test. As a result, the transmittance of bare glass was 90.5%, while that of AR coating glass increased to 94.8% at curing temperature of $300^{\circ}C$. When the fluoroalkylsilane was added, the water contact angle of AR coating film increased from $96.3^{\circ}$ to $108^{\circ}$, indicating that the hydrophobicity of the film was greatly improved. The abrasion resistance of AR coating film was also improved by the acid catalyst, whereas the transmittance increased by the base catalyst. In the case of AR coating film prepared using an acid-base two step catalyzed reaction, both the transmittance and abrasion resistance of the film was synergistically enhanced as compared with those of AR coating films prepared without introduction of a catalyst.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.1047-1053
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• 2008

This study was to evaluate the optimum conditions for chemical coagulation to remove color from the effluent of a piggery wastewater treatment process. The DOC concentration in the effluent was about 227.3 mg/L, color was 2,430 CU, turbidity was 22.1 NTU, and UV$_{254}$-absorbance was 3.7 cm$^{-1}$. The fractions of hydrophobic, transphilic, and hydrophilic substance of the effluent was about 55.3%, 17.4%, 27.3% respectively. Also, molecular weight cut-off(MWCO) of below 0.5 K, 0.5 K to 1 K, 1 K to 10 K, 10 K to 30 K, and over 30 K were 74.2%, 7.3%, 5.5%, 7.1%, and 5.9% respectively. SCD(streaming current Detector) was used to find out the optimum pH values and coagulant dosages. The optimum dosages and pH of Al$^{3+}$ were 5.84 mM and 5.3, while those of Fe$^{3+}$ were 9.25 mM and 5.0, respectively. At optimum conditions of coagulation, color removal efficiencies for aluminium sulfate and ferric chloride were as high as 91.9 and 98.7%, respectively. Chemical coagulation showed good performance to remove color from on biologically treated piggery wastewater.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.2
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• pp.73-77
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• 2012

Co-(0.8 wt%) and Ce-(0.4 wt%) doped cubic zirconia ($ZrO_2$ : $Y_2O_3$ = 80 : 20, 70 : 30, 60 : 40, 50 : 50 wt%) single crystals grown by a skull melting method were heat-treated in $N_2$ at $1000^{\circ}C$ for 5 hrs. The orange, yellowish brown and brown colored as-grown single crystals were changed into either brownish red, yellow and green color after the heat treatment. Before and after the heat treatment, the YSZ (yttria-stabilized zirconia) single crystals were cut for wafer form (${\phi}6.5mm{\times}t2mm$). The optical and structural properties were examined by UV-VIS spectrophotometer and X-ray diffraction. Absorption by $Ce^{3+}(^2F_{5/2,7/2}(4f){\rightarrow}^2T_g(5d^1))$, $Co^{2+}(^4A_2(^4F){\rightarrow}^4T_1(^4F)$ or $^4T_1(^4P))$ and $Co^{3+}$, change of ionization energy and lattice parameter were confirmed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.382-389
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• 2019

A novel folding process is proposed using a repeated cold-die forging and annealing to form a sterling silver ring. Sterling silver plate was cut into a doughnut shape, and lattices with 0.43-mm line-width were imprinted on it. The sample was folded by forging using dies with slopes of $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$ and annealing. For comparison, samples were also fabricated without annealing. Strain was identified by measuring the length of lattices. Vernier calipers, a Vickers hardness tester, an optical microscope, and a UV-VIS colorimeter were used to determine the size, hardness, microstructure, and body color. Without annealing, cracks occurred. However, successful deformation was possible when annealing was used. The results of macro strain measurements show that the outer diameter and width decreased, while the inner diameter and thickness increased after the final process. The maximum strain was increased 0.128 toward the parallel direction. The Vickers hardness decreased after annealing and increased after the folding process. The microstructure results showed that the grain size increased after annealing but decreased after folding. The color difference based on the Lab index was under 10 for all processes. Eventually, a doughnut-shaped silver plate was successfully deformed into a ring shape by the folding process.

• Journal of Conservation Science
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• v.37 no.2
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• pp.120-134
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• 2021

A Woolen carpet from the late Joseon Dynasty was unearthed in the process of repairing Seongjeonggak in Changdeokgung. Since relics are rarer than documentary records, the woolen carpet is highly valued as a relics. It is presumed to have been woven in the late 19th or early 20th century because there is a record of repairing Seongjeonggak in 1907. In the carpet, a pattern is made by inserting colored yarn dyed yellow and red onto a reddish-purple ground weave. The selvage of the woolen carpet used cotton thread, and jute is used for the warp and weft of the ground weave. The colored patterns is made of wool in the form of loop pile. Cut piles may appear occasionally when the colored yarn changes, but are almost invisible from the surface because they are pressed tightly with a shuttered weft. Making carpets with jute and wool is thought to be influenced by the Brussels carpets of the mid-18th century. Furthermore, the woolen carpet is torn and the pattern is completely unclear; however, it is understandable that the pattern is partially repeated. Microscopic and Fourier transform-Infrared spectrometer(FT-IR) analyses were performed for the above investigation. To identify the dyes used in relics, we compared them with natural dyed fabric samples based on chromaticity measurements and Ultraviolet/Visible spectrophotometer(UV-Vis) analysis. These analyses revealed that the woolen carpet's dyed green yarn did not use indigo, and reddish-purple ground weave is estimated to have used Caesalpinia sappan.