• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.51-54
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• 2003

Tb-doped lead zirconate titanate($Pb_{1.1}(Zr_{0.6}Ti_{0.4})O_3$; PZT) thin films on $Pt(111)/Ti/SiO_2/Si(100)$ substrates prepared by a sol-gel method. Films have a Zr/Ti ratio of 60:40 and perovskite phase structure. The effect on the structural and electrical properties of films measured according to Tb content. Dielectric and ferroelectric properties of PZT thin films were altered significantly by Tb-doping. The PZT thin film with higher dielectric constant and improved leakage current characteristic was obtained by adding 0.3 mol% Tb. At 100 kHz, the dielectric constant and the dielectric loss of the 0.3 mol% Tb-doped PZT thin film were 1611 and 0.24, respectively The remanent polarization(2Pr) of the 0.3 mol% Tb-doped PZT thin film was $61.4\;{\mu}C/cm^2$ and the coercive field was 61.9 kV/cm. Tb-doped PZT thin films showed improved fatigue characteristics comparing to the undoped PZT thin film.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1252-1254
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• 2005

High Tc superconducting(HTS) model coil was prepared. Current-voltage(I-V) characteristic curves of model coil, sub-coils and joints were investigated at 77K and other some temperatures. Cooling system for characteristics measurement was made by using G-M cryocooler. At 77K, quench current(Iq) of model coil was 43.9A and the lowest Iq of sub-coils was 38.8A. At 55K, sub coil SP #06 was 106A. So, 100A was chosen as the operating current at 55K with margin. Joule heat of model coil was 0.65W at 100A, operating current and 58K. Joint resistances between sub-coils were about $70n{\Omega}$ at 77K and about $30n{\Omega}$ at 55K.

• International Journal of Oral Biology
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• v.44 no.3
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• pp.108-114
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• 2019

In the present study, rutile phase titanium dioxide nanoparticles ($R-TiO_2$ NPs) were prepared by hydrolysis of titanium tetrachloride in an aqueous solution followed by calcination at $900^{\circ}C$. The composition of $R-TiO_2$ NPs was determined by the analysis of X-ray diffraction data, and the characteristic features of $R-TiO_2$ NPs such as the surface functional group, particle size, shape, surface topography, and morphological behavior were analyzed by Fourier-transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, transmission electron microscopy, dynamic light scattering, and zeta potential measurements. The average size of the prepared $R-TiO_2$ NPs was 76 nm, the surface area was $19m^2/g$, zeta potential was -20.8 mV, and average hydrodynamic diameter in dimethyl sulfoxide (DMSO)-$H_2O$ solution was 550 nm. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and morphological observations revealed that $R-TiO_2$ NPs were cytocompatible with oral cancer cells, with no inhibition of cell growth and proliferation. This suggests the efficacy of $R-TiO_2$ NPs for the aesthetic white pigmentation of teeth.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.6
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• pp.229-236
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• 2014

A stoichiometric mixture of evaporating materials for $MnAl_2S_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $MnAl_2S_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the $MnAl_2S_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=3.7920eV-5.2729{\times}10^{-4}eV/K)T^2/(T+786 K)$. In order to explore the applicability as a photoconductive cell, we measured the sensitivity (${\gamma}$), the ratio of photocurrent to dark current (pc/dc), maximum allowable power dissipation (MAPD) and response time. The results indicated that the photoconductive characteristic were the best for the samples annealed in S vapour compare with in Mn, Al, air and vacuum vapour. Then we obtained the sensitivity of 0.93, the value of pc/dc of $1.10{\times}10^7$, the MAPD of 316 mW, and the rise and decay time of 14.8 ms and 12.1 ms, respectively.

• Journal of the Korean Electrochemical Society
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• v.18 no.1
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• pp.17-23
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• 2015

$Li_4Ti_5O_{12}$ (LTO) have attracted much attention of researchers in the field of energy storage, because of their excellent stability for electric vehicle application. A main drawback of LTO is however their insulating nature due to the wide bandgap, which should be addressed to enhance the battery performance. In this study, we investigated the effect of water solubility of dopant precursor on the electrochemical characteristics of conducting LTO prepared by doping with $Cr^{3+}$ ions with the well-known wet-mixing method. The solubility of dopant precursor directly affected the morphology and the phase of doped LTO, and therefore their battery performance. In the case of employing the most soluble dopant precursor, $Cr(NO_3)_2$, the doped LTO demonstrated a markedly enhanced discharge capacity at high C-rate (130mAh/g @ 10C), which is about 2 times higher value than that of bare LTO.

• Radiation Oncology Journal
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• v.19 no.1
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• pp.74-80
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• 2001

Purpose : Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials : Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. Results : The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of $35\~85\;cGy/min$ could be achieved from modern accelerators without any modification. and the depth in water of $50\%$ depth dose from backscatter electron located at 6mm for $45^{\circ}$ angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions : The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.

• The Journal of Internal Korean Medicine
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• v.21 no.2
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• pp.259-266
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• 2000

Objectives : The effects of aqueous extracts of Cortex ulmi pumilae (a traditional medicine for cancer treatment in oriental medicine) on the induction of apoptotic cell death were investigated in human liver origm hepatoma cell lines, HepG2. Methods : The death of HepG2 cells was markedly induced by the addition of extracts of Cortex ulmi pumilae in a dose-dependent manner. The apoptotic characteristic ladder pattern of DNA strand break was not observed in cell death of HepG2. In addition, it was not shown nucleus chromatin condensation and fragmentation under hoechst staining. However, by the using annexin V staining assay, externalizations of phosphatidylserine in HepG2 cell which were treated with Cortex ulmi pumilae extracts were detected in the early time (at 9 hr after extract treatment). Furthermore, LDH release was not detected in this early stage. Therefore, Cortex ulmi pumilae extracts-induced cell death of HepG2 cells is mediated by apoptotic death signal processes. Result : The activity of caspase 3-like proteases remained in a basal level in HepG2 cells which treated with the extract of Cordyceps sinensis. However, it was markedly increased in HepG2 cells which treated with two extracts of Cortex ulmi pumilae (C.U.P.-C, C.U.P.-K) which were differently extracted (respectively, 2.3 and 3.3 fold). On a while, the phosphotransferase activities of JNK1 was markedly induced in HepG2 cells which were treated with two extracts of Cortex ulmi pumilae. On the contrary, the activation of transcriptional activator, activating protein1(AP-1) and NF-kB were severely decreased by these two extracts of Cortex ulmi pumilae (C.U.P.-C, C.U.P.-K). In addition, antioxidants (GSH and NAC) and intracellular $Ca2^+$ level regulator (Bapta/AM and Thapsigargin) did not affect Cortex ulmi pumilae extracts-induced apoptotic death of HepG2 cells. Conclusions : In conclusion, our results suggest that two extracts of Cortex ulmi pumilae (C.U.P.-C, C.U.P.-K) induces the apoptotic death of human liver origin hepatoma HepG2 cells via activation of caspase 3-like proteases as well as JNK1, and inhibition of transcriptional activators, AP-1 and $NK-{\kappa}B$.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.12
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• pp.696-704
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• 2015

This study was carried out to evaluate the optimum operational condition of Semi-continuously Fed and Mixed Reactor (SCFMR) to treat the dairy cow manure and saw dust mixture. Step-wise increase in organic loading rates (OLRs) or decrease in hydraulic retention times (HRTs) were utilized until the biogas volume became significantly decreased at mesophilic temperature ($35^{\circ}C$). The optimum operating condition of the SCFMR fed with TS 13% dairy cow manure and saw dust mixture was found to be an HRTs of 25 days and its corresponding OLRs of $4.45kg\;VS/m^3-day$. At this condition the biogas and methane production rates were 1.44 v/v-d and 1.12 v/v-d (volume of biogas per volume of reactor per day), respectively and the TVS removal efficiency of 37% was achieved. The successful operation with such a high OLR was due to the high reactor alkalinity concentration of 14,500~15,600 mg/L as $CaCO_3$ as a result of the characteristic of the original substrate, dairy cow manure and saw dust mixture whose alkalinity was more than 8,000 mg/L as $CaCO_3$. The parameters for the reactor stability, the ratios of volatile acids and alkalinity concentrations (V/A) and the ratio of propionic acid and acetic acid concentrations (P/A) appeared to be 0.11 and 0.43, respectively, that were greatly stable in operation. Free ammonia toxicity was not experienced due to the long term acclimation by the reactor TS content ranged 7.2~10.4% during the entire operational period.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.5
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• pp.448-454
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• 2000

This study was to examine the physicochemical characteristics of coagulation reaction between ignited oyster shell powder (IOSP) and red tide organisms (RTO), and its feasibility, in developing a technology for the removal of RTO bloom in coastal sea,IOSP was made from oyster shell and its physicochemical characteristics were examined for particle size distribution, surface characteristic by scanning electron microscope, zeta potential, and alkalinity and pH variations in sea water. Two kinds of RTO that were used in this study, Cylindrotheca closterium and Skeletonema costatum, were sampled in Masan bay and were cultured in laboratory. Coagulation experiments were conducted using various c(Incentrations of IOSP, RTO, and a jar tester. The supernatant and RTO culture solution were analyzed for pH, alkalinity, RTO cell number, IOSP showed positive zeta potentials of $11.1{\~}50.1\;mV\;at\;pH\;6.2{\~}12.7$, A positive zeta potential of IOSP slowly decreased with decreasing pNa 4,0 to 2,0. When pNa reached zero, the zeta potential approached zero, When a pMg value was decreased, the positive zeta potential of IOSP increased until pMg 3.0 and decreased below pMg 3.0. IOSP showed 4.8 mV of positive zeta potential while RTO showed -9.2 mV of negative zeta potential in sea water. A positive-negative EDL (electrical double-layer) interaction occurred between $Mg(OH)_2$ adsorption layer of IOSP and RTO in sea water so that EDL attractive force always worked between them. Hence, their coagulation reaction occurred at primary minimum on which an extreme attractive force acted because of charge neutralization by $Mg(OH)_2$ adsorption layer of IOSP. As a result, the coagulation reaction was rapidly processed and was irreversible according to DLVO (Deriaguin-Landau-Verwey-Overbeek) theory. Removal rates of RTO were exponentially increased with increasing both IOSP concentration and G-value. The removal rates were steeply increased until 50 mg/l of IOSP and reached $100{\%}\;at\;400\;mg/l$ of IOSP. Removal rates of RTO were $70.5,\;70.5,\;81.7,\;85.3{\%}$ for G-values of $1,\;6,\;29,\;139\;sec^(-1)$at IOSP 100 mg/l, respectively. This indicated that mixing (i.e., collision among particles) was very important for a coagulation reaction.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.4 no.1
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• pp.5-12
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• 2004

Purpose Phenylketonuria is an inborn error of metabolism, which is inherited as an autosomal recessive trait. PKU is resulting from deficiency of phenylalanine hydroxylase. PAH gene spans about 90 kb on chromosome 12q and comprises 13 exons. In order to define the genetic basis of PKU and the frequencies and distribution of PAH mutations in the Korean population, we analyzed PAH gene in independent 80 patients with PKU. Methods All 13 exons including exon-intron boundaries and 2 kb of 5' upstream region of the PAH gene were analyzed by PCR-direct sequencing methods. Results PAH gene analysis revealed 39 different mutations including 10 novel mutations. The novel mutations consisted of 9 missense mutations (P69S, G103S, N207D, T278S, P281A, L293M, G332V, S391I and A447P) and a novel splice site variant (IVS10-3C>G). R243Q, IVS4-1G>A, and E6-96A>G were the most relevant mutations and they accounted in the whole for 38% of the mutant alleles identified in this study. We also observed that. $BH_4$ responsibility was. associated with genotype of R241C, R53H and R408Q. Conc1ustion Our present study with 80 participants extends the previous results to more comprehensive understanding of PAH allele distribution and frequency in Koreans. Although Korean mutation profile of PAH is similar to those of the nearest oriental populations (Japanese, Chinese, and Taiwanese), several different characteristic features are revealed. The characterization of the genotype-phenotype relationship was also performed. Our data would be very useful information for diagnosis, genetic counseling and planning of dietary and therapeutic strategies in Korean PAH patients.