• Korean Journal of Materials Research
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• v.8 no.5
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• pp.408-412
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• 1998

Thermoelectric properties of Bi$_{2}$(Te$_{1-x}$Se$_{ x}$)$_{3}$(0.05$\leq$x$\leq$0.25) prepared by mechanical alloying and hot pressing, were investigated. Contrary to the p-type behavior of single crystals, the hot-pressed Bi$_{2}$(Te$_{1-x}$Se$_{ x}$)$_{3}$ exhibited ntype conduction without addition of donor dopant. When $Bi_2(Te_{0.85}Se_{0.15})_3$powders were annealed in (50% $H_2$ + 50% Ar) atmosphere, the hot-pressed specimen exhibited a positive Seebeck coefficient due to the reduction of the electron concentration by removal of the oxide layer on the powder surface and annealing-out of the excess Te vacancies. Among the Bi$_{2}$(Te$_{1-x}$Se$_{ x}$)$_{3}$fabricated by mechanical alloying and hot pressing, $Bi_2(Te_{0.85}Se_{0.15})_3$ exhibited a maximum figure-of-merit of 1.92 $\times$ $lO^{-3}$/K.

• Journal of Conservation Science
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• v.33 no.1
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• pp.1-10
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• 2017

The rock-carved seated Buddha of Unju temple of Hwasun, Jeonnam, the only Triad Buddha among the stone Buddhas of Unju temple, is currently designated as a tangible cultural property No. 275 of Jeollanam-do. The rock of the seated Triad Buddha bedrock is light-green andesitic tuff breccia that is composed of quartz and feldspar. The results of measurement of the whole rock magnetic susceptibility characteristics, the rock consists of a single sedimentary layer from top to bottom. The results of ultrasonic velocity measurement, show that the number of frequency of 1500~2000 m/s increased and the number of frequency of 2000~2500 m/s decreased in 2009 compared to 2015, and the measurement value for 2000 m/s or below was 87.5% in 2015, a 68.8% increase in comparison to that in 2009. Moreover, on the top, bottom, left side, and head areas of the Triad Buddha, a partial expanding tendency was observed in the range of low ultrasonic velocity. As weathering of the Triad Buddha occurs in the long term, on-going monitoring is required to ascertain the degree of change with time.

• Restorative Dentistry and Endodontics
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• v.26 no.4
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• pp.307-315
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• 2001

The application of Nd:YAG laser and irrigants to the root surface can change its surface configurations. The purpose of this study was to investigate the effects of Nd:YAG laser and irrigants on the apical seal of obturated canals. In this study, 66 single rooted teeth were randomly assigned to 4 group of 14 teeth each. 8 teeth were served us positive and negative controls. The teeth were divided into 6 groups as follows. Group A: Nd:YAG laser, 5% NaOCl + Rc-prep Group B: Nd:YAG laser, Saline Group C: 5% NaOCl + Rc-prep Group D: Saline Group E: Positive control Group F: Negative control 66 teeth were instrumented using Maillefer ProFile$^{\circledR}$ (Orifice Shapers, .04 taper, .06 taper Dentsply, Switzerland). Two of each group were selected at random, and the canal wall surfaces were examined under a SEM. 12 teeth of each group were obturated using by lateral condensation technique. Specimens were immersed in india ink for 7days, decalcified by 10% nitric acid, dehydrated by 75. 80. 85, 90, 95 and 100% alcohol in order cleared by methyl salicylate and then measured of dye penetration with stereomicroscope($\times$15 magnification) and Image Pro plus. The data were analyzed statistically by one-way ANOVA test and Duncan's Multiple Range test. The results were as follows : 1. The mean leakage was 0.128$\pm$0.376 for group A, 0.237$\pm$0.325 for group B, 0.397$\pm$0.468 for group C, 0.586$\pm$0.402 for group D, and there were statistically significant differences between group A and group D, group B and group D. (p<0.05). 2. Group A had better sealing ability than Group C, but there was statistically no significant differences. (p>0.05). 3. Group B had better sealing ability than Group D and there was statistically significant difference. (p<0.05). 4 Group A had better sealing ability than Group B, but there was statistically no significant difference. (p>0.05). 5. Group C had better sealing ability than Group D, but there was statistically no significant difference. (p>0.05). 6. As a result of observation under SEM, Smear layers were removed in Group A, B. but Smear layers were partially removed and smear plugs were remained in Group C, Smear layers were not removed in Group D. To be specially, Melting of smear layer were showed in Group C. 7. These results suggests that the laser has a potential in reducing the apical microleakage of obturated canals.

• Journal of the Korean GEO-environmental Society
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• v.14 no.9
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• pp.31-37
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• 2013

In this study installation diameter, interval, area replacement ratio and ground hardness of applicable ground in C.G.S method should be mastered through surrounding ground by conducting modeling. Optimum artificial neural network was selected through the study of the parameter of artificial neural network and prediction model was developed by the relationship with numerical analysis and artificial neural network. As this result, C.G.S pile settlement and ground settlement were found to be equal in terms of diameter, interval, area replacement ratio and ground hardness, presented in a single curve, which means that the behavior pattern of applied ground in C.G.S method was presented as some form, and based on such a result, learning the artificial neural network for 3D behavior was found to be possible. As the study results of artificial neural network internal factor, when using the number of neural in hidden layer 10, momentum constant 0.2 and learning rate 0.2, relationship between input and output was expressed properly. As a result of evaluating the ground behavior of C.G.S method which was applied to using such optimum structure of artificial neural network model, is that determination coefficient in case of C.G.S pile settlement was 0.8737, in case of ground settlement was 0.7339 and in case of ground heaving was 0.7212, sufficient reliability was known.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.587-590
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• 2013

Solid-liquid equilibria for mixtures composed of n-vinyl-2-pyrrolidone (NVP) and 2-pyrrolidone were measured as a basic study for the melt crystallization process to remove 2-pyrrolidone as impurity included in NVP. A differential scanning calorimeter (DSC) and a crystallizer were used and the experimental results obtained from two methods were similar. The mixture showed a eutectic system which has a single composition at the minimum melting temperature. Calculation results from simple thermodynamic equations were found in general agreements with present data. To determine the growth rate of NVP crystal which is important for the design of crystallization process, thicknesses of the crystal were measured with the time using a layer melt crystallizer. The growth rates increased as cooling temperatures decreased. Heat transfer coefficient correlated from present data was found to successfully describe the crystal growth behavior.

• 전기의세계
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• v.28 no.4
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• pp.53-63
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• 1979

Interface recombination velocity in $Al_{x}$G $a_{1-x}$ As-GaAs and $Al_{0.85}$, G $a_{0.15}$ As-GaA $s_{1-y}$S $b_{y}$ heterojunction systems is studied as a function of lattice mismatch. The results are applied to the design of highly efficient III-V heterojunction solar cells. A horizontal liquid-phase epitaxial growth system was used to prepare p-p-p and p-p-n $Al_{x}$G $a_{1-x}$ As-GaA $s_{1-y}$S $b_{y}$-A $l_{x}$G $a_{1-x}$ As double heterojunction test samples with specified values of x and y. Samples were grown at each composition, with different GaAs and GaAs Sb layer thicknesses. A method was developed to obtain the lattice mismatch and lattice constants in mixed single crystals grown on (100) and (111)B oriented GaAs substrates. In the AlGaAs system, elastic lattice deformation with effective Poisson ratios .mu.$_{eff}$ (100=0.312 and .mu.$_{eff}$ (111B) =0.190 was observed. The lattice constant $a_{0}$ (A $l_{x}$G $a_{1-x}$ As)=5.6532+0.0084x.angs. was obtained at 300K which is in good Agreement with Vegard's law. In the GaAsSb system, although elastic lattice deformation was observed in (111) B-oriented crystals, misfit dislocations reduced the Poisson ratio to zero in (100)-oriented samples. When $a_{0}$ (GaSb)=6.0959 .angs. was assumed at 300K, both (100) and (111)B oriented GaAsSb layers deviated only slightly from Vegard's law. Both (100) and (111)B zero-mismatch $Al_{0.85}$ G $a_{0.15}$As-GaA $s_{1-y}$S $b_{y}$ layers were grown from melts with a weight ratio of $W_{sb}$ / $W_{Ga}$ =0.13 and a growth temperature of 840 to 820 .deg.C. The corresponding Sb compositions were y=0.015 and 0.024 on (100) and (111)B orientations, respectively. This occurs because of a fortuitous in the Sb distribution coefficient with orientation. Interface recombination velocity was estimated from the dependence of the effective minority carrier lifetime on double-heterojunction spacing, using either optical phase-shift or electroluminescence timedecay techniques. The recombination velocity at a (100) interface was reduced from (2 to 3)*10$^{4}$ for y=0 to (6 to 7)*10$^{3}$ cm/sec for lattice-matched $Al_{0.85}$G $a_{0.15}$As-GaA $s_{0.985}$S $b_{0.015}$ Although this reduction is slightly less than that expected from the exponential relationship between interface recombination velocity and lattice mismatch as found in the AlGaAs-GaAs system, solar cells constructed from such a combination of materials should have an excellent spectral response to photons with energies over the full range from 1.4 to 2.6 eV. Similar measurements on a (111) B oriented lattice-matched heterojunction produced some-what larger interface recombination velocities.ities.ities.s.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1185-1189
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• 2005

Two new copper vanadium borophosphate compounds, $(NH_4)(C_2H_{10}N_2)_{5.5}[Cu(C_2H_8N_2)_2]_3[V_2P_2BO_{12}]_6{\cdot}17H_2O,\;Cu-VBPO1\;and\;(NH_4)(C_2H_{10}N_2)_{3.5}[Cu(C_2H_8N_2)_2]_5[V_2P_2BO_{12}]_6{\cdot}18H_2O$, Cu-VBPO2 have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, thermogravimetric analysis, IR spectroscopy, and elemental analysis. The structure of Cu-VBPO1 contains a layer anion, {$[Cu(C_2H_8N_2)_2]_3[V_2P_2BO_{12}]_6$}$^{12-}$, whereas Cu-VBPO2 has an open framework anion, {$[Cu(C_2H_8N_2)_2]_5[V_2P_2BO_{12}]_6$}$^{8-}$. Crystal Data: $(NH_4)(C_2H_{10}N_2)_{5.5}[Cu(C_2H_8N_2)_2]_3[V_2P_2BO_{12}]_6{\cdot}17H_2O$, monoclinic, space group I2/m (no. 12), $\alpha$ = 15.809(1) $\AA$, b = 31.107(2) $\AA$, c = 12.9343(8) $\AA$, $\beta$ = 104.325(1)$^{\circ}$, Z = 2; $(NH_4)(C_2H_{10}N_2)_{3.5}[Cu(C_2H_8N_2)_2]_5[V_2P_2BO_{12}]_6{\cdot}18H_2O$, tetragonal, space group $P4_2$/mnm (no.136), $\alpha$ = 26.832(1) $\AA$, c = 18.021(1) $\AA$, Z = 4.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.28-37
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• 2017

Multipath TCP (MPTCP), which is a layer 4 protocol that can get the reliability and the efficiency of the transmission by using multipath transfer, was standardized by the IETF. MPTCP provides superior performance when compared to a single TCP when used in a homogeneous network with similar network characteristics. However, MPTCP degrades performance when used in heterogeneous networks with different network characteristics. In this paper, we propose 'Delay-alerted path-blocking scheduler'. It measures the delay of each path and blocks the path with a long delay to reduce the order of packets in the receive buffer. If the duplicated packet is sent to the blocked path to measure the delay and the congestion on the blocking path is reduced, the blocked path is unblocked. For performance analysis, the proposed scheduler was implemented in the Linux kernel and improved performance was obtained in the test bed. We also confirmed that the proposed scheduler reduces the degradation of MPTCP performance in real wireless networks with heterogeneous path characteristics.

• Korean Journal of Bronchoesophagology
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• v.6 no.1
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• pp.29-37
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• 2000

Background and Objectives : The concentration of sulfur dioxide($SO_2$) gas in the ambient air appears increasing in the industry and urban area day by day. It was known that $SO_2$ is noxious gas. $SO_2$ can be irritating to the eyes, nose, throat, upper respiratory tract and skin. It produces sulfurous acid on contact with water and is extremely irritating to the nasopharynx and respiratory tract. Laminin is a family of extracellular matrix glycoproteins localized in the basement membrane that separates epithelial cells from the underlying stroma. The biological activities of laminin are to promote cell migration, wound healing, growth and differentiation. Meterials and Methods : The histologic changes and the expression of laminin in tracheal mucosa sacrificed at every weeks (to 7 weeks) after continued $SO_2$ exposure of 250ppm for 30 minutes a day were studied in rats. Results : Pathologic tissue was formed at the tracheal mucosa and the underlying tissue by the infiltration of monocytes and epithelium was transformed to the single cell layered epithelium above 5 weeks after exposure. At the 6 weeks after exposure, epithelial cells were partially lost and epithelial cell layer was transformed to be leaf-shaped. Submucosal tissue was transformed to be lymphatic tissue. An intense positive staining for laminin was found in apical cytoplasm and lateral surface of the normal epithelial cells and basement membrane but at the 5 and 6 weeks after exposure, laminin activity was decreased to the moderate activity. At the 7 weeks after exposure, laminin activity was decreased to the weak activity. Conclusion : Our finding suggests that $SO_2$ makes histologic damage on the tracheal mucosa and decreases immunoreactivity for laminin. Longer duration of the exposure of $SO_2$ makes more histologic damage on the tracheal mucosa and decreases immunoreactivity for laminin.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.300-307
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• 1998

The $Co_{90}Fe_{10}$ single layer films were deposited on various substrates (glass, Si, polymide) using high vacuum RF magnetron sputtering system and nominall 1000 $\AA$ thick $Co_{90}Fe_{10}$ alloy films had a good high frequency characteristic. $M_S$ and $H_{an}$ values obtained from the B-H characteristic of the $10{\times}[100 nm \;Co_{90}Fe_{10}/100 nm\; SiO_2]$ multilayers agreed well with those obtained by calculation. Complex relative permeability $(={\{\mu}_r={\mu}_r',-j{\mu}$\mu$_r")$ at frequency f was measured from the transmission characteristics $(S_{11},\; S_{21}\;parameters)$ of the microstrip line which has a stacked structure consisting of sample magnetic films and a conductor and is connected to a network analyzer. The ${\mu}_r'-f$ characteristic was abtained from the megnetic absorption, which was analyzed from the S-parameter characteristics of the microstrip line. The ${\mu}_r'-f$ characteristic was also calculated from the ${\mu}_r"-f$-f characteristic using the Kramers-Kronig relation. The measurement results were confirmed to agree well with those obtained by calculations.culations.