• Science of Emotion and Sensibility
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• v.21 no.2
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• pp.137-144
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• 2018

The study figured out the operational conditions of a two-way movement actuator made of one-way shape memory alloy (OWSMA) for versatile ventilation intelligent garments. To develop a low-power actuator that consumes energy only when a garment changes its form such as opening and closing, multiple channels of OWSMA were used, and optimum diameter of the wires was examined. For the switch device, optimum voltage application unit time was determined. Optimum diameter of OWSMA wire was determined by applying 3.7V to the pre-determined candidate diameters, which demonstrated two-way operation in previous studies. In order to evaluate the optimum voltage application time, the internal diameter of the actuator was measured while increasing and decreasing by 50 ms from the unit time of voltage application. Delay time under two-way operation of the actuator was measured to minimize interference caused by heat between channels. Power of 3.7V was applied to OWSMA for assessment of optimal time, and the whole process from heating to cooling was video-recorded with a thermal image camera to determine the point of time at which the temperature of OWSMA wire dropped below the phase transformation temperature. The results showed that $0.4{\Phi}$ was the most suitable diameter, and the optimum unit time of voltage applied to open and close the actuator was 4100ms. It was also shown that the delay time should be more than 1.8 seconds between two-way operations of the actuator.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.220-225
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• 1998

The spinel structured $LiMn_2O_4$ was prepared from $Li_2CO_3$ and $MnO_2$ by calcination at various temperatures in the range of $750{\sim}900^{\circ}C$. It was found that the most suitable cubic structure of $LiMn_2O_4$ was obtained by heating at $850^{\circ}C$ for 12 hrs. However, in the calcination at $900^{\circ}C$, $Mn^{4+}$ of 0.06M was changed to $Mn^{+3}$ by the oxygen loss, so that it has been shown that the formula has changed to $LiMn_2O_{3.97}$. This phenomena were in agreement with the Jahn-Teller distortion by the increment of $Mn^{+3}$ ion on the octahedral sites of the spinel structured $LiMn_2O_4$. The results showed that after 15 charge/discharge cycles in the voltage range from 3.5V to 4.3V versus Li/$Li^+$ with a current density of $0.25mA/cm^2$, the spinel structured $LiMn_2O_4$ that was prepared at $900^{\circ}C$ showed a lower discharge capacity, 82~50 mAh/g, while the $LiMn_2O_4$, prepared at $850^{\circ}C$, showed the discharge capacity of 102~64 mAh/g.

• Analytical Science and Technology
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• v.12 no.1
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• pp.34-39
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• 1999

Estrone such as estriol and estradiol can not be determined by votammetric methods, because these are electrochemically inactive in the potential windows for mercury drop electrode. Nitro-derivatives of estrone are electro active and nitration of estrone is accomplished by heating the solution involving estrone and sodium nitrite in a water-bath at $100^{\circ}C$ for 30 min. Such nitro-derivatives are determined directly by voltammetry. The electrochemical behavior for nitrated estrone was investigated by cyclic voltammetry. The trace estrone was determinated by differential pulse adsorptive cathodic stripping voltammetry. Nitrated estrone gives a well defined voltammetric wave at ca. - 0.61 V (vs. Ag/AgCl electrode). The electrochemical reaction was irreversible process in sodium borate buffer at pH 11 and nitrated estrone was strongly adsorbed on the surface of mercury electrode. The optimal experimental conditions for the determination of nitrated esterone were found to be 0.05 M sodium nitrate, 0.01 M sodium borate, pH 11.0, and an accumlation potential of 0.10 V (vs. Ag/AgCl). The detection limit was as low as $1{\times}10^{-9}M$ for estrone with 2 min accumulation time.

• The Journal of the Korea Contents Association
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• v.17 no.11
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• pp.221-228
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• 2017

This paper aimed to find out the eco-friendly approach enabling to directly print patterns and dye colors on fabrics using leaves of plants. In the research process, I found out the 'eco-printing' which could effectively express unique colors and patterns of plants. While eco-printing can design the patterns and colors of plants in nature using the leaves of plant(Eucalyptus), it is difficult to implement because it is not systematically and academically investigated including the dictionary definition in Korea until now. Thus, I tried to define the eco-printing and natural dyeing using leaves or flowers of plants enabling to get natural patterns and colors and do the experimental research and production using the leaves of Eucalyptus. The leaves of Eucalyptus were arranged on a wool scarf and a silk scarf, tied and applied pressure to them and made pigments penetrate into fabrics by heating or steaming them. This approach is to directly print the patterns using the shapes of plants on fabrics unlike the existing approaches dyeing by extracting dyeing solution from natural materials. Furthermore, the change of colors was attempted by using the color fixers. In accordance with the results of this experimental research, the scarf design differentiated from the existing products could be acquired. It was identified that eco-printing could induce the color variables depending on the conditions of each material and environment. For improving the color variables, various kinds of fabrics and divers kinds of materials which can be easily acquired in a daily life will be investigated and compared. Furthermore, it is expected that the experimental research and production techniques on eco-printing be utilized when starting natural dyeing and the scope of natural dyeing be more expanded.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.19-28
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• 2011

This study developed a solar radiation reflection pavement, so called a cool pavement, to lessen the urban heat island effect by coating a pavement surface with acrylic resins mixed with light-colored pigments. From a laboratory test, simulating solar heating process in pavements, the cool pavement reduced more than $12^{\circ}C$ of pavement temperature at $60^{\circ}C$ compared to a control porous pavement. With the increase of the mixing ratio of the pigments to acrylic resins, the temperature reduction effect increased, but its workability became worse due to higher viscosity. As a result, an appropriate mixing ratio was determined as 15%. The cool pavement had better durability than the control pavement: One quarter of Catabro loss and twofold dynamic stability. Its adhesion was also higher enough not to be debonded under traffic loading. In-situ noise and friction tests conducted in two field sites showed that the cool pavement reduced its noise level by 3.7dB in average and increased its friction level by 30% compared to the control pavement. The permeability of the cool pavement was little lower than the control pavement, but higher enough to satisfy the minimum requirement for porous pavements.

• Journal of Ginseng Research
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• v.37 no.1
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• pp.124-134
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• 2013

The authentication of the physico-chemical properties of ginsenosides reference materials as well as qualitative and quantitative batch analytical data based on validated analytical procedures is a prerequisite for certifying good manufacturing practice (GMP). Ginsenoside Rb1 and Rg1, representing protopanaxadiol and protopanaxatriol ginsenosides, respectively, are accepted as marker substances in quality control standards worldwide. However, the current analytical methods for these two compounds recommended by Korean, Chinese, European, and Japanese pharmacopoeia do not apply to red ginseng preparations, particularly the extract, because of the relatively low content of the two agents in red ginseng compared to white ginseng. In manufacturing fresh ginseng into red ginseng products, ginseng roots are exposed to a high temperature for many hours, and the naturally occurring ginsenoside Rb1 and Rg1 are converted to artifact ginsenosides such as Rg3, Rg5, Rh1, and Rh2 during the heating process. The analysis of ginsenosides in commercially available ginseng products in Korea led us to propose the inclusion of the (20S)- and (20R)-ginsenoside Rg3, including ginsenoside Rb1 and Rg1, as additional reference materials for ginseng preparations. (20S)- and (20R)-ginsenoside Rg3 were isolated by Diaion HP-20 adsorption chromatography, silica gel flash chromatography, recrystallization, and preparative HPLC. HPLC fractions corresponding to those two ginsenosides were recrystallized in appropriate solvents for the analysis of physico-chemical properties. Documentation of those isolated ginsenosides was achieved according to the method proposed by Gaedcke and Steinhoff. The ginsenosides were subjected to analyses of their general characteristics, identification, purity, content quantification, and mass balance tests. The isolated ginsenosides showed 100% purity when determined by the three HPLC systems. Also, the water content was found to be 0.534% for (20S)-Rg3 and 0.920% for (20R)-Rg3, meaning that the net mass balances for (20S)-Rg3 and (20R)-Rg3 were 99.466% and 99.080%, respectively. From these results, we could assess and propose a full spectrum of physico-chemical properties of (20S)- and (20R)-ginsenoside Rg3 as standard reference materials for GMP-based quality control.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.450-455
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• 2002

Cu-cored Sn-Ag solder balls were fabricated by coating pure Sn and Ag on Cu balls. The melting behavior and the solderability of the BGA joint with the Ni/Au coated Cu pad were investigated and were compared with those of the commercial Sn-Ag and Sn-Ag-Cu balls. DSC analyses clarified the melting of Cu-cored solders to start at a rather low temperature, the eutectic temperature of Sn-Ag-Cu. It was ascribed to the diffusion of Cu and Ag into Sn plating during the heating process. After reflow soldering the microstructures of the solder and of the interfacial layer between the solder and the Cu pad were analyzed with SEM and EPMA. By EDX analysis, formation of a eutectic microstructure composing of $\beta$-Sn, Ag$_3$Sn, ad Cu$_{6}$Sn$_{5}$ phases was confirmed in the solder, and the η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer was found to form at the interface between the solder and the Cu pad. By conducting shear tests, it was found that the BGA joint using Cu-cored solder ball could prevent the degradation of joint strength during aging at 423K because of the slower growth me of η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer formed at the solder, pad interface. Furthermore, Cu-cored multi-component Sn-Ag-Bi balls were fabricated by sequentially coating the binary Sn-Ag and Sn-Bi solders on Cu balls. The reflow property of these solder balls was investigated. Melting of these solder balls was clarified to start at the almost same temperature as that of Sn-2Ag-0.75Cu-3Bi solder. A microstructure composing of (Sn), Ag$_3$Sn, Bi and Cu$_{6}$Sn$_{5}$ phases was found to form in the solder ball, and a reaction layer containing primarily η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ was found at the interface with Ni/Au coated Cu pad after reflow soldering. By conducting shear test, it was found that the BGA joints using this Cu-core solder balls hardly degraded their joint shear strength during aging at 423K due to the slower growth rate of the η'-(Au, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer at the solder/pad interface.he solder/pad interface.

• Journal of the Korean Chemical Society
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• v.4 no.1
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• pp.18-26
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• 1957

There are two problems to be solved by our efforts in the enamel frit. One is how we can cover the enamel frit thin with complete milk white as possible, and the other is how it can be, made resistant for chemicals than before one. The frit which can solved the two problems just mentioned above is titanium enamel frit. This frit has been developed in America after War Ⅱ, and now the research for concerning antimony frit into titanium frit is under development entirely. In order to develope the enamel industry in Korea, it is urgent problem to convert antimony frit into titanium frit. By the way the titanium frit is emulsified titanium oxide crystal which made through reheating the supersaturated solution of titanium oxide in the basis of glass. Unfortunately, there are many obscure points in active fact or which influence on its composition and characteristics yet. However, this task was tried for the first in Korea. As first step, the test was carried on the reference books, and we can be possible convert antimony frit into titanium frit as a result of this experiment. As a conclusion, for the purpose of developing the enamel industry in Korea, we studied that the research for converting antimony enamel frit which has been used popularly into titanium enamel frit which is more economic and resistant for chemicals. As a result of experiments, the following points concerning with titanium frit have become clearly. 1. It is better when the composition of titanium enamel frit has as following table.Man Duck San Silica 24 An Yang Feldspar 20 Borax 28 Sodium Nitrate 4 Cryolite 7 Calcium Carbonate 3.6∼1 Titanium Oxide 10 Calcium phosphate 0 ∼3.2 Calcium Fluoride 0∼1.8 Antimony Oxide 0∼0.5 2. The amount of $TiO_2$, to be added is $10%\;to\;12{%,\;CaF_2\;is\;under\;1.8%,\;P_2O_5\;is\;under\;1.6%,\;Sb_2O_3\;is\;under\;0.5%$. 3. In the titanium frit, the limit of iron oxide amount to be included is under 0. 5%. 4. Comparing the titanium enamel frit with antimony enamel frit not only the titanium frit can be savely 20.6% in the price of raw materials, but one time of glazing and heating process is omitted in each case, and it is known the titanium frit is more resistant for chemicals than antimony frit.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.15-19
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• 2015

We demonstrated an inspection system for detecting discoloration of PCB Cu ball pad with an OSP surface finish. Though the OSP surface finish has many advantages such as eco-friendly and low cost, however, it often shows a discoloration phenomenon due to a heating process. In this study, the discoloration was analyzed with device-independent CIELAB color space. First of all, the PCB samples were inspected with standard lamps and CCD camera. The measured data was processed with Labview program for detecting discoloration of Cu ball pad. From the original PCB sample image, the localized Cu ball pad image was selected to reduce the image size by the binarization and edge detection processes and it was also converted to device-independent CIELAB color space using $3{\times}3$ conversion matrix. Both acquisition time and false acceptance rate were significantly reduced with this proposed inspection system. In addition, $L^*$ and $b^*$ values of CIELAB color space were suitable for inspection of discoloration of Cu ball pad.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.430-437
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• 1997

Uranyl-peroxide compound was prepared by the reaction of excess hydrogen peroxide solution and trace uranium in filtrate from nuclear fuel conversion plant. The $CO_3{^{2-}}$ in filtrate was removed first by heating more than $98^{\circ}C$, because uranyl-peroxide compound could not be precipitated by $CO_3{^{2-}}$ remaining in filtrate. The optimum condition for uranyl-peroxide compound was ageing for 1 hr after controling the pH with $NH_3$ gas and adding the excess $H_2O_2$ of 10ml/lit.-filtrate. Uranium concentration in the filtrate was appeared to 3 ppm after the precipitation of uranyl-peroxide compound, and the chemical composition of this compound was analyzed to $UO_4{\cdot}2NH_4F$ with FT-IR, X-ray diffractometry, TG and chemical analysis. Also, this fine particle, about $1{\sim}2{\mu}m$, could be grown up to $4{\mu}m$ at pH 9.5 and $60^{\circ}C$. The separation efficiency of precipitate from mother liquor was increased with increase of pH and reaction temperature. Otherwise, the crystal form of this particle showed octahedral by SEM and XRD, and $U_3O_8$ powder was obtained by thermal decomposition at $650^{\circ}C$ in air atmosphere.