• Korean Journal of Materials Research
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• v.11 no.4
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• pp.305-311
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• 2001

$PbO-B_2O_3-SiO_2-Al_2O_3$, system was investigated for optical, thermal and electrical properties of transparent dielectric. We also studied the reaction between transparent dielectric and transparent electrode(Indium Tin Oxide, ITO) during firing. For the evaluation of properties, dielectrics were prepared under the conditions fired at 520~58$0^{\circ}C$ with 12$\mu\textrm{m}$ thickness. In the reaction between dielectrics and electrode(ITO), In ions diffused into dielectric layer, while Sn ion diffusion was not observed. The coefficient of thermal expansion, the dielectric constant, the glass transition temperature and the transmittance of the dielectric were greatly dependent on PbO content. The increase of the coefficient of thermal expansion and the dielectric constant were monitored by increasing PbO, while the glass transition temperature and the transmittance were decreased. With the increased $Al_2O_3/B_2O_3$ ratio, the coefficient of thermal expansion and the transmittance were decreased, while the dielectric constant was increased. The glass transition temperature did not change significantly.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.45-56
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• 2006

Recently, the more potential waste sites are being required as increasing the demand of better human life. But the construction of waste disposals has many restrictions because of lack of good quality clay and high cost of liners. So, in this study, we studied the liner materials to develop more cheaper soil liner that can be satisfied the environmental criterion for the coefficient of permeability and shear strength. A series of compaction test and triaxial (consolidation, permeability, and shear) tests were performed to obtain the optimized weight ratio of Bentonite-Soil mixture (B/S) including the least amount of bentonite. A series of soil tests were performed to acquire the appropriate weathered granite soil-bentonite mixture that is satisfied the environmental criterion of soil liner($k=1{\times}10^{-7}cm/sec$). At first, weathered granite soils were classified with four different particle-size soils, and B/S ratio was increased as 5% step for each particle-size. The test results showed that in case of weathered granite soil passing through No. 100 sieve, B/S=15% satisfied the soil liner criterion. The measured coefficient of permeability and the Chapuis's two equations were also compared. And a predicting equation for the coefficient of permeability was suggested, which is suitable for the mixture soil with the B/S ratio used in this study. The optimal weight ratio for the mixture soils used in this study was 15% in the both cases of permeability and shear strength.

• Honam Mathematical Journal
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• v.15 no.1
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• pp.75-85
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• 1993

For A and B, $-1{\leq}B<A{\leq}1$, let P[A, B] be the class of functions p analytic in the unit disk E with P(0) = 1 and subordinate to $\frac{1+Az}{1+Bz}$. We introduce the class $T_{\alpha}[A,B]$ of functions $f:f(z)=z+\sum\limits_{n=2}^{{\infty}}a_nz^n$ which are analytic in E and for $z{\in}E$, ${\alpha}{\geq}0$, $[(1-{\alpha}){\frac{f(z)}{z}}+{\alpha}f^{\prime}(z)]{\in}P[A,B]$. It is shown that, for ${\alpha}{\geq}1$, $T_{\alpha}[A,B]$ consists entirely of univalent functions and the radius of univalence for $f{\in}T_{\alpha}[A,B]$, $0<{\alpha}<1$ is obtained. Coefficient bounds and some other properties of this class are studied. Some radii problems are also solved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.682-685
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• 2002

The $0.96MgTiO_3-0.04SrTiO_3$ ceramics with $B_2O_3$(10wt%) were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature by XRD. According to the X-ray diffraction pattern of the $0.96MgTiO_3-0.04SrTiO_3$ ceramics with $B_2O_3$(10wt%), the ilmenite $MgTiO_3$ and perovskite $SrTiO_3$ structures were coexisted and secondary phase of the $MgTi_2O_5$ were appeared. In the case of $0.96MgTiO_3-0.04SrTiO_3+B_2O_3$(10wt%) ceramics sintered $1225^{\circ}C$, dielectric constant, quality factor and temperature coefficient of resonant frequency were 19.82, 62,735GHz, $-2.983ppm/^{\circ}C$, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.43-46
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• 2018

This paper has designed a wideband bandpass filter (WBSF : Wide Band Stop Filter) using a stepped impedance resonator (SIR : Stepped Impedance Resonator) with improved performance and improved hairpin coupling structure. The SIR WBSF is small in size and has the advantage of having excellent bandstop characteristics. The designed BSF has a structure in which a quadrangular shaped hairpin of a / 4 length is arranged symmetrically on the upper and lower sides of the input and output transmission lines. The input and output terminals were terminated at 50 ohms for system applications. The center frequency of the SIR WBSF is 6.3 GHz, which is the second harmonic of 3.15 GHz. The designed filter has a 3dB bandwidth of 2.9 GHz and a transmission coefficient ($S_{21}$) of 33.2 dB. The reflection coefficient ($S_{11}$) at the center frequency is 0.106 dB. The application field is used for fixed microwave relay stations, fixed satellite and earth stations, and fixed satellite communications. The overall size is $20mm{\times}10mm$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.75-78
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• 2005

Silicon boride ($SiB_6$) is very promising for use as thermoelectric materials at high temperature because of its high melting point and relatively large Seebeck coefficient. In the present work, spark plasma sintering (SPS) was applied for preparing dense $SiB_6$ ceramics, and their thermoelectric properties were investigated, together with their microstructural evaluation. The SPS process was found to be effective in densifying a $SiB_6$ ceramic, typically 99 % of the theoretical density at low temperature of $1500^{\circ}C$. In comparison with $SiB_6$ specimen prepared by hot-pressing, the SPS-processed specimen exhibited the significantly improved Seebeck coefficient, resulting in the higher power factor.

• Journal of IKEEE
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• v.19 no.1
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• pp.87-93
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• 2015

In this paper, a $145{\mu}W$, 87dB SNR, Low power 3rd order Sigma-Delta Modulator with Op-amp sharing is proposed. Conventional architecture with analog path and digital path is improved by adding a delayed feed -forward path for disadvantages that coefficient value of the first integrator is small. Proposed architecture has a larger coefficient value of the first integrator to remove the digital path. Power consumption of proposed architecture using op-amp sharing is lower than conventional architecture. Simulation results for the proposed SDM designed in $0.18{\mu}m$ CMOS technology with power supply voltage 1.8V, signal bandwidth 20KHz and sampling frequency 2.8224MHz shows SNR(Signal to Noise Ratio) of 87dB, the power consumption of $145{\mu}W$.

• Journal of the Korean Home Economics Association
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• v.20 no.4
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• pp.1-12
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• 1982

This study was to investigate the changes of shape of the lower limb surface, the rate of the measurement of expansion and contraction and correlation coefficient between variables caused by hip joint and knee joint movements. The results of the investigation are as follows; 1. According to the development figure of shell when the leg was raised $45^{\circ}$forward($M_{2}$), total length of F.L shortened while B.L lengthened. This result is contarary to $M_{3}$raising the leg $15^{\circ}$ backward. In both $M_{2}$, $M_{3}$movements, the rate of expansion and contraction to the course direction was insignificant. When hip joint was bent $15^{\circ}$ with knee joint $120^{\circ}$bent ($M_{4}$) and hip joint was bent $30^{\circ}$ with knee joint $90^{\circ}$ bent($M_{5}$), upper section of back hip expanded while the front hip section contracted slightly. In the Movement of sitting on the chair($M_{6}$), abdomen, front hip section and upper thight section contracted to the wale direction remarkably while the back hip section expanded conspicuously. 2. According to the rate of expansion and contraction of skin (surface) by the somatometry. In $M_{2}$, C.F.L. upper and middle thight girth contracted and B.L, C.L, L.L expanded. This fact is contarary to M3. In M4, M5, C.F.L showed remarkable contraction and C.B.L expanded remarkably. In $M_{6}$, C.B.L contracted most of all the items measured and knee girth, F.L, L.L, C.B.L, hip girth expanded conspicuously. 3. According to the correlation coefficient between variables. In various movements, the correlation among girth items commonly showed a high or middle grade, the correlation among length items also commonly showed a low grade and that girth and length items showed a very low grade commonly. Waist girth, hip grith, F.L, B.L, L.L items showed that there were significant correlation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1757-1763
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• 2009

The composites were fabricated by adding 0, 15, 20, 25[vol.%] Zirconium Diboride(hereafter, $ZrB_2$) powders as a second phase to Silicon Carbide(hereafter, SiC) matrix. The physical, mechanical and electrical properties of electroconductive SiC ceramic composites by Spark Plasma Sintering(hereafter, SPS) were examined. Reactions between ${\beta}-SiC$ and $ZrB_2$ were not observed in the XRD analysis. The relative density of mono SiC, SiC+15[vol.%]$ZrB_2$, SiC+20[vol.%]$ZrB_2$ and SiC+25[vol.%]$ZrB_2$ composites are 90.93[%], 74.62[%], 74.99[%] and 72.61[%], respectively. The XRD phase analysis of the electroconductive SiC ceramic composites reveals high of SiC and $ZrB_2$ and low of $ZrO_2$ phase. The lowest flexural strength, 108.79[MPa], shown in SiC+15[vol.%] $ZrB_2$ composite and the highest - 220.15[MPa] - in SiC+20[vol.%] $ZrB_2$composite at room temperature. The trend of the mechanical properties of the electroconductive SiC ceramic composites moves in accord with that of the relative density. The electrical resistivities of mono SiC, SiC+15[vol.%]$ZrB_2$, SiC+20[vol.%]$ZrB_2$ and SiC+25[vol.%]$ZrB_2$ composites are 4.57${\times}10^{-1}$, 2.13${\times}10^{-1}$, 1.53${\times}10^{-1}$ and 6.37${\times}10^{-2}$[${\Omega}$ cm] at room temperature, respectively. The electrical resistivity of mono SiC, SiC+15[vol.%]$ZrB_2$. SiC+20[vol.%]$ZrB_2$ and SiC+25[vol.%]$ZrB_2$ are Negative Temperature Coefficient Resistance(hereafter, NTCR) in temperature ranges from 25[$^{\circ}C$] to 100[$^{\circ}C$]. The declination of V-I characteristics of SiC+20[vol.%]$ZrB_2$ composite is 3.72${\times}10^{-1}$. It is convinced that SiC+20[vol.%]$ZrB_2$ composite by SPS can be applied for heater or electrode above 1000[$^{\circ}C$]

• The korean journal of orthodontics
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• v.13 no.1
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• pp.105-114
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• 1983

the author studied the corelativity between the head and face and the maxillary arch in Korean. This study was undertaker in 336 persons at age from 9 to 19 years who had normal occlusion by means of angle's classification. The following results were obtained. 1. The corelative coefficient between the Height of Head and Face (H.H.F.) and the Arch Length (A.L.) was 0.203-0.543, 2. The corelative coefficient between the Bizygomatic width (Z.W.) and the Bicanine width (C-C) was 0.203-0.543. 3. The corelative coefficient between the Bizygomatic width (Z.W.) and the Bimolar width (M-M) was 0.206-0.600. 4. The corelative coefficient between the Face shape (Index a) and Maxillaxy arch shape (In-dex c) was 0.232-0.404. 5. The corelative coefficient between the Face shape (Index a) and Maxillary arch shape (Index d) was 0.221-0.401. 6. There was no corelativity between the Anterior-posterior width of head (A.P.W.) and Arch Length A.L.), Head shape (Index b) and Maxillary arch shape (Index c, Index d).