• Journal of Powder Materials
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• v.21 no.5
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• pp.377-381
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• 2014

This work describes the coloration, chemical stability of $SiO_2$ and $SnO_2$-coated blue $CoAl_2O_4$ pigment. The $CoAl_2O_4$, raw materials, were synthesized by a co-precipitation method and coated with silica ($SiO_2$) and tin oxide ($SnO_2$) using sol-gel method, respectively. To study phase and coloration of $CoAl_2O_4$, we prepared nano sized $CoAl_2O_4$ pigments which were coated $SiO_2$ and $SnO_2$ using tetraethylorthosilicate, $Na_2SiO_3$ and $Na_2SiO_3$ as a coating material. To determine the stability of the coated samples and their colloidal solutions under acidic and basic conditions, colloidal nanoparticle solutions with various pH values were prepared and monitored over time. Blue $CoAl_2O_4$ solutions were tuned yellow color under all acidic/basic conditions. On the other hand, the chemical stability of $SiO_2$ and $SnO_2$-coated $CoAl_2O_4$ solution were improved when all samples pH values, respectively. Phase stability under acidic/basic condition of the core-shell type $CoAl_2O_4$ powders were characterized by transmission electron microscope, X-ray diffraction, CIE $L^*a^*b^*$ color parameter measurements.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.232-234
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• 2006

Diabetic neuropathy is one of the most common diabetic complications. In clinical practices, nerve conduction velocity (NCV) has been used as a standard method for diagnosing diabetic neuropathy. However, it applies maximum of 100mA electric stimulus to nerves causing stress and pain to patients. In this study. as a non-invasive method, $TcpO_2$ was utilized to investigate the difference and relationship between $TcpO_2$ and $SpO_2$ of normal and diabetic neuropathy subjects. In addition, a new method of diagnosing diabetic neuropathy using $TcpO_2$ is suggested. 50 normal subjects and 50 diabetic patients with neuropathy diagnosed by NCV participated in this study. Parameters used in this study were $TcpO_2,\;TcpCo_2$, and $SpO_2$. As a result of the $TcpO_2$ measurements, statistical significances were found from $TcpO_2$ of hands and feet from normal and patients group (p<0.01). $SpO_2$ measured from index finger of normal and patient groups showed no statistical significance (p>0.05). On the other hand, $SpO_2$ measured from great toes of normal and patient group showed statistical significance (p<0.01). Correlation coefficient between $SpO_2$ of finger and $TcpO_2$ of hand was 0.400 (p<0.01) and $SpO_2$ of toe and $TcpO_2$ of foot was 0.471 (p<0.01). Both correlation values were statistically significant. Sensitivities and specificities of the $TcpO_2$ method were found to be 66 % and 92 %, respectively. If suggested $TcpO_2$ method is used periodically. prevention and early diagnosis of diabetic neuropathy is possible.

• Management & Information Systems Review
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• v.38 no.2
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• pp.29-46
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• 2019

O2O services, a form of mobile commerce, are increasing due to the widespread use of smartphones and the rational consumption trend of young consumers. In addition, the introduction of Social Commerce's O2O service has transformed customer experience into innovation. Therefore, the purpose of this study is to investigate the effect of O2O service characteristics and social commerce provider characteristics on the social commerce 's O2O service as a social psychological image that consumers have at the point of purchase and use time, as a smart shopper feeling and a cheapness shopper feeling. And the relationship between consumer satisfaction and intention to use through Structure Equation Modeling, and to suggest the implications for O2O service management that can provide greater satisfaction to consumers by identifying the process of creating satisfaction of O2O service. The results of the study show that price discounts and scarcity of social commerce's O2O service characteristics have shown that it increases smart shopper feeling. Also, it was confirmed that brand awareness and ease of purchase, which are characteristics of social commerce, confirms the increase of cheapness shopper feeling. We also confirmed the effect of smart shopper feeling and cheapness shopper feeling on satisfaction. This satisfaction has a positive effect on the intention to use. The result of this study is that it is necessary to reduce the cheapness shopper feeling of consumers and to emphasize the price discount and scarcity so that the smart shopper feeling occurs in order to satisfy the consumers who purchase O2O service products.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.436-439
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• 1997

We investigated a electrical and CO gas sensing properties of pure ZnO and ZnO-ZrO$_2$ composite ceramics. We made 0∼20mo1% ZrO$_2$added ZnO composite ceramics and observed a microstructure of the broken side of the samples. The properties of the samples were studied with temperature, composition, arid a concentration of carbon monoxid. The measured 1000ppm CO sensitivities of pure ZnO were about 1∼1.42, and that of ZnO-ZrO$_2$were about 1∼10.6. In order words, the 1000ppm CO sensitivities of ZnO-ZrO$_2$composite ceramics were about 1∼2 times larger than that of pure ZnO with temperature. The measured 250ppm, 500ppm CO sensitivities of ZnO-ZrO$_2$composite ceramics were about ∼3.28. ∼5.04, respectively.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.311-317
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• 2003

Vanadium oxides supported on zirconia and modified with MoO₃were prepared by adding Zr(OH)₄powder into a mixed aqueous solution of ammonium metavanadate and ammonium molybdate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using FTIR, Raman spectroscopy and solid-state $^{51}V$ NMR. In the case of a calcination temperature of 773 K, for samples containing low loading of $V_2O_5$, below 15 wt %, vanadium oxide was in a highly dispersed state, while for samples containing high loading of $V_2O_5$, equal to or above 15 wt %, vanadium oxide was well crystallized because the $V_2O_5$ loading exceeded the formation of a monolayer on the surface of $ZrO_2$. The $ZrV_2O_7$ compound was formed through the reaction of $V_2O_5\;and\;ZrO_2$ at 873 K and the compound decomposed into $V_2O_5\;and\;ZrO_2$ at 1073 K, which were confirmed by FTIR spectroscopy and solid-state $^{51}V$ NMR. IR spectroscopic studies of ammonia adsorbed on $V_2O_5-MoO_3/ZrO_2$ showed the presence of both Lewis and Bronsted acids.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.179-190
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• 1997

To study the effects of chemical composition on the fusion temperatures of coal ashes, the chemical composition, mineral matter, and fusion temperature were studied with 54 kinds of coal ash samples including Korean anthracite coals. CaO, MgO and $Fe_2O_3$ were observed to be major fluxing elements in reducing and oxidizing atmosphere. The fluxing effect of $Fe_2O_3$ was increased more in reducing atmosphere. In a base/acid ratio, the fusion temperature decreased with increasing amounts of basic components. Nevertheless, the correlation between a fusion temperature and base/acid ratio was not shown well in a higher ratio of $Fe_2O_3/CaO$. The differences of fusion temperatures between oxidizing and reducing atmosphere showed close relationship with $SiO_2/Al_2O_3$ ratio rather than with $Fe_2O_3$ contents. Multiple regression was used to predict the fusion temperature of coal ashes, and it was established that the major predictors in oxidizing atmosphere were Base/Acid, $Fe_2O_3/CaO$, $SiO_2/Al_2O_3$, and $(SiO_2/A1_2O_3){\cdot}(Base/Acid)$ and Base/Acid, $Fe_2O_3/CaO$, $SiO_2$, and $TiO_2$ were major ones in reducing atmosphere.

• Journal of the Korean Ceramic Society
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• v.33 no.8
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• pp.928-934
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• 1996

Quantitative analysis each portland cement components was conducted by standard calibration method using X-ray fluorescence spectrometer. Standard sample and the unknown sample were prepared by fused cast bead method. In checking the errors of standard cement 227A372 the relative errors of constituents such as CaO, SiO2, Al2O3, Fe2O3, MgO and SrO were less than 1% and the relative errors of constituents such as So3, K2O, TiO2, Na2O P2O5, and Mn2O3 were less than 5% Sample preparation was mainly contributed to the errors. Compared with general wet chemical method the results of X-ray fluorescence analyses were more precise and accurate. Moreover it is possible to analyze precisely a little amount of the constituents such as SrO, Mn2O3 and P2O5 the analyses of which were very difficult using the wet chemical method.

• Korean Journal of Materials Research
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• v.19 no.11
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• pp.613-618
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• 2009

We designed new compositions for lead free and low temperature sealing glass frit of $ZnO-V_2O_5-P_2O_5$ system, which can be used for PDP (Plasma Display Panel) or other electronic devices. The $ZnO-V_2O_5-P_2O_5$ system can be used as a sealing material at temperatures even lower than 430$^{\circ}C$. This system, however, showed lower bonding strength with glass substrate compared to commercialized Pb based sealing materials. So, we added $TiO_2$ as a promoter for bonding strength. We examined the effect of $TiO_2$ addition on sealing behaviors of $ZnO-V_2O_5-P_2O_5$ glasses with the data for flow button, wetting angle, temporary & permanent residual stress of glass substrate, EPMA analysis of interface between sealing materials and glass substrate, and bonding strength. As a result, sealing characteristics of $ZnO-V_2O_5-P_2O_5$ system glasses were improved with $TiO_2$ addition, but showed a maximum value at 5 mol% $TiO_2$ addition. The reason for improved bonding characteristics was considered to be the chemical interaction between glass substrate and sealing glass, and structural densification of sealing glass itself.

• Journal of the Korean Ceramic Society
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• v.23 no.3
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• pp.44-52
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• 1986

$Al_2O_3-ZrO_2$ ceramics was obtained by the co-precipitation method using $Al_2(SO_4)_2$.$18H_2O$ and $ZrOCl_2$.$8H_2O$ as starting materials $MgCl_2$.$6H_2O$ as a sintering aid and NH4OH as a hydrolyzing agent. The coprecipitate from the above raw materials was calcined at 125$0^{\circ}C$ for 1h and again sintered at 1$650^{\circ}C$ for 2h before measurements of strength hardness and fracture toughness. MgO addition was found to increase mechanical properties of the $Al_2O_3-ZrO_2$ system. The strength and frac-ture toughness of $Al_2O_3-ZrO_2$ ceramics were considered to be increased by stress-induced phase tranforma-tion of $ZrO_2$.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.6
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• pp.783-792
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• 2004

In this study, a thick-film semiconductor odor gas sensor for the detection of $CH_3$SH was developed using SnO$_2$ as the main substrate and was investigated in terms of its sensitivity and reaction time. In the process of manufacturing the sensor, Taguchi's design of experiment (DOE) was applied to analyze the effects of a variety of parameters, including the substrate, the additives and the fabrication conditions, systematically and effectively. Eight trials of experiments could be possible using the 27 orthogonal array for the seven factors and two levels of condition, which originally demands 128 trials of experiments without DOE. The additives of Sb$_2$O$_{5}$ and PdCl$_2$ with the H$_2$PtCl$_{6}$ ㆍ6$H_2O$ catalyst were appeared to be important factors to improve the sensitivity, and CuO, TiO$_2$, V$_2$O$_{5}$ and PdO were less important. In addition, TiO$_2$, V$_2$O$_{5}$ and PdO would improve the reaction time of a sensor, and CuO, Sb$_2$O$_{5}$, PdCl$_2$ and H$_2$PtCl$_{6}$ㆍ6$H_2O$ were negligible. Being evaluated simultaneously in terms of both sensitivity and reaction time, the sensor showed the higher performance with the addition of TiO$_2$ and PdO, but the opposite results with the addition of CuO, V$_2$O$_{5}$, Sb$_2$O$_{5}$ and PdCl$_2$. The amount of additives were superior in the case of 1% than 4%. H$_2$PtCl$_{6}$ㆍ6$H_2O$ would play an important role for the increase of sensor performance as a catalyst.nce as a catalyst.