• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.291-294
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• 2007

This paper preserts the characteristics of leakage currents flowing through 18 kV zinc oxide (ZnO) surge arrester under the mixed DC and AC voltages. The I-V curves of ZnO surge arrester were measured as a function of the voltage ratio K The I-V curves under the mixed DC and AC voltages lay between the pure DC and AC characteristics, and the cross-over phenomenon in I-V curves was observed at the low current region As a result, the increase of DC component to mixed voltages causes the increase of resistive component of total leakage current th ZnO surge arrester.

• 한국전기전자재료학회논문지
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• 제22권3호
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• pp.230-234
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• 2009

Hydrogen and Oxygen plasma treatments have been done on sonochemical grow ZnO nanorods by varying treatment temperature and time, The changes(position and intensity) in ultraviolet(UV) peaks and green peaks of photoluminescence(PL) spectroscopy have been measured, Experimental results showed; i) in the case of hydrogen plasma treatment, the blue shift of UV peak and the increase of PL intensity of the UV peak were observed as the increase of the process time and temperature, ii) in the case of oxygen plasma treatment, the red shift of green peak was observed and the ratio of $I_{Green}/I_{UV}$ was also increased, as the increase of the process time and the temperature.

• 한국세라믹학회지
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• 제21권3호
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• pp.221-230
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• 1984

In this study an investigation was made to determine optimum ratio between $SO_3$, MgO and $K_2O$ that maximizes $C_2S$ formation in Clinkering reaction Using response surface analysis method. It was proved that 1) Residual $K_2O$ int he clinker should be converted to $K_2SO_4$ because $K_2SO_4$ has less effect on the burnability than $K_2O$, 2) Optimum ratio if $SO_3$/K2O is 1.5, 3) Optimun balance between $CaSO_4$ and MgO is to be adjusted to such a level that w/o SO3=0.7(w/o MgO-2).4) In case of lack of $K_2O$ free CaO was minimized when $K_2SO_4$=2.3w/o and MgO=1.5w/o but if remaining $K_2O$ was 2w/o free CaI was minimized in the level that $K_2SO_4$=2.3w/o and MgO =1.5 w/o but if remaining $K_2O$ was 2 w/o free CaO was minimized in the level that $K_2SO_4$=4.5w/o and MgO =3.0 w/o.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1672-1679
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• 2002

This paper provides an engineering J estimation equation for cylinders with finite internal axial surfacecracks under internal pressure. The proposed equation is the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-O) materials. Based on detailed 3-D FE results using deformation plasticity, plastic influence functions for fully plastic J components are tabulated for practically interesting ranges of the mean radius-to-thickness ratio, the crack depth-to-length ratio, the crack depth-to-thickness ratio. the strain hardening index for the R-O material, and the location along the semi-elliptical crack front. Based on tabilated plastic influence functions, the J estimation equation along the crack front is proposed and validated for R-O materials. Good agreements between the FE results and the proposed J estimation provide confidence in the use of the proposed method to elastic-plastic fracture mechanics of pressurized piping.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.795-797
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• 1998

A $BaTiO_3$, ferroelectric material, was mixed $SrTiO_3$, $(x)BaTiO_3-(1-x)SrTiO_3$($0.7{\leq}x{\leq}1$) ceramic capacitor with stable electrical properties in high voltage was fabricated. And microstructure, electrical property were investigated with $SrTiO_3$ mol ratio. The shrinkage, open porosity, sintering density were predominated at $9BaTiO_3-0.1SrTiO_3$. Increasing $SrTiO_3$ mol ratio, curie temperature was shifted at low temperature and maximum permittivity was increased. Also, $0.9BaTiO_3-0.1SrTiO_3$ was showed stable dielectric properties at $25{\sim}80[^{\circ}C]$. V-I properties of specimen were observed in the temperature range of $21{\sim}143[^{\circ}C]$, were divided into three regions. The region I below 10[kV/cm] was shown Ohmic conduction, the region II from 10 to 30[kV/cm] was explained by the Poole-Frenkel emission theory and the region III above 30[kV/cm] was analysed by the tunneling effect.

• 핵의학기술
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• 제18권2호
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• pp.68-72
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• 2014

핵의학 검사는 반감기로 인한 동위원소의 잔류로 당일에 두 가지 검사를 시행하는데 어려움이 있다. 본 연구는 $^{18}F$-FDG와 $^{99m}TcO_4{^-}$의 상호 영향을 연구함으로써 당일 검사를 진행할 경우 고려될 사항에 대해 알아보고자 한다. NEMA-1994 Phantom을 이용하여 세 번의 실험을 진행했다. 첫 실험은 $^{99m}TcO_4{^-}$을 HOT과 BKG 비 4:1로 만들어 GE사의 INFINIA 장비로 SPECT를 시행하였고, BKG 영역에 $^{18}F$-FDG 37 MBq을 주입 후 동일 조건으로 60분에 1회씩 13회 Scan 했다. 두 번째는 $^{18}F$-FDG를 HOT과 BKG 비 4:1 로 만들어 GE사의 PET/CT Discovery 600 에서 Scan 하였고, BKG 영역에 $^{99m}TcO_4{^-}$을 148 MBq 주입 후 동일 조건으로 60분에 1회씩 6회 Scan 했다. 마지막 실험은 $^{18}F$-FDG를 HOT과 BKG 비 4 : 1로 만들고 1 Bed Scan 후 $^{99m}TcO_4{^-}$을 148 MBq 및 296 MBq씩 증가 시키며 같은 조건으로 1 Bed Scan했다. HOT과 BKG 영역의 비, CNR 혹은 SNR 그리고 총 획득 계수를 측정 후 비교 했다. $^{18}F$-FDG는 SPECT 시행 시 비율 및 CNR에 유의한 차이를 보였다(p>0.05). $^{99m}TcO_4{^-}$는 PET/CT 시행 시 비율 및 SNR이 유의한 차이를 보이지 않았다(p<0.05). $^{99m}TcO_4{^-}$이 PET/CT 검사의 Total Counts를 감소시킨다는 결과를 획득했다. PET/CT 검사를 한 경우 12시간 까지도 $^{99m}TcO_4{^-}$을 이용한 검사에 영향을 미칠 수 있으며, $^{99m}TcO_4{^-}$를 먼저 시행한 경우에는 PET/CT 검사에 SUV 및 SNR에 영향은 없지만 검출 효율을 감소시켰다. 당일 검사 시에는 $^{99m}TcO_4{^-}$을 이용한 검사를 먼저 진행하고 PET/CT의 검사 시간을 늘려 검출 효율을 보완하는 방법을 권장하고자 한다.

• Membrane and Water Treatment
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• 제13권4호
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• pp.201-208
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• 2022

Emulsion Liquid Membrane (ELM) is a prominent technique for the separation of heavy metal ions from wastewater due to the fast extraction and is a single-stage operation of stripping-extraction. The selection of the components (Surfactant and Carrier) of ELM is a very significant step for its preparation. In the ELM technique, the primary water- in-oil (W/O) emulsion is emulsified in water to produce water-in-oil-in-water (W/O/W) emulsion. The water in oil emulsion was prepared by mixing the membrane phase and internal phase. To prepare the membrane phase, the extractant D2EHPA (di-2-ethylhexylphosphoric acid) was used as a mobile carrier, Span-80 as a surfactant, and Paraffin as a diluent. Moreover, the internal (receiving) phase was prepared by dissolving sulphuric acid in water. Di-(2- ethylhexyl) phosphoric acid such as surfactant concentration, carrier concentration, sulphuric acid concentration in the receiving (internal) phase, agitation time (emulsion phase and feed phase), the volume ratio of the membrane phase to the receiving phase, the volume ratio of the external feed phase to the primary water-in-oil emulsion and pH of feed were studied on the percentage extraction of metal ions at 20℃. The results show that it is possible to remove 78% for As(V), 98% for Cd(II), and 99% for Pb(II). Emulsion Liquid Membrane (ELM) is a well-known technique for separating heavy metal ions from wastewater due to the fast extraction and is a single-stage operation of stripping-extraction. The selection of ELM components (Surfactant and Carrier) is a very significant step in its preparation. In the ELM technique, the primary water-in-oil (W/O) emulsion is emulsified to produce water-in-oil-in-water (W/O/W) emulsion. The water in the oil emulsion was prepared by mixing the membrane and internal phases. The extractant D2EHPA (di-2-ethylhexylphosphoric acid) was used as a mobile carrier, Span-80 as a surfactant, and Paraffin as a diluent. Moreover, the internal (receiving) phase was prepared by dissolving sulphuric acid in water. Di-(2-ethylhexyl) phosphoric acid such as surfactant concentration, carrier concentration, sulphuric acid concentration in the receiving (internal) phase, agitation time (emulsion phase and feed phase), the volume ratio of the membrane phase to the receiving phase, the volume ratio of the external feed phase to the primary water-in-oil emulsion and pH of feed were studied on the percentage extraction of metal ions at 20℃. The results show that it is possible to remove 78% for As(V), 98% for Cd(II), and 99% for Pb(II).

• 한국세라믹학회지
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• 제31권6호
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• pp.629-636
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• 1994

The ferrimagnetic glass-ceramics in the system Fe2O3-CaO-SiO2 for hyperthermia were investigated. Glasses could be prepared up to the content of 40 wt% of Fe2O3 and below the weight ratio of 1.0 of CaO/SiO2. The maximum saturation magnetization and the maximum coercive force were 29.85 emu/g and 340.1 Oe respectively, for a glass 40Fe2O3.20CaO.40SiO2 composition heat-treated at 95$0^{\circ}C$ for 8 hours. And for a glass 40Fe2O3.30CaO.30SiO2 composition the maximum saturation magnetization and the maximum coercive force were 18.47 emu/g and 374.4 Oe heat-treated at 1,00$0^{\circ}C$ and 90$0^{\circ}C$ for 8 hours respectively. The maximum hysteresis loss was 1,726.3 cal/g for a glass 40Fe2O3.20CaO.40SiO2 composition heat-treated at 95$0^{\circ}C$ for 8 hours. It was found that the ferrimagnetic Fe2O3.CaO.SiO2 glass-ceramics was little injurious to human body as results of biocompatibility test and biotoxicity test.

• 한국전기전자재료학회논문지
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• 제22권11호
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• pp.941-948
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• 2009

The present study aims at the examination of the effects of 1 mol% NiO addition on the reaction, microstructure development, resultant electrical properties, and especially the bulk trap and interface state levels of $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=0.5, 1.0, and 2.0) systems (ZBS). The samples were prepared by conventional ceramic process, and characterized by density, XRD, SEM, I-V, impedance and modulus spectroscopy (IS & MS) measurement. The sintering and electrical properties of Ni-doped ZBS (ZBSN) systems were controlled by Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$) was decomposed more than $100^{\circ}C$ lowered in ZBS (Sb/Bi=1.0) by Ni doping. The reproduction of pyrochlore was suppressed by the addition of Ni in ZBS. Between two polymorphs of $Zn_7Sb_2O_{12}$ spinel ($\alpha$ and $\beta$), microstructure of ZBSN (Sb/Bi=0.5) composed of a-spinel was more homogeneous than $Sb/Bi{\geq}1.0$ composed of $\beta$-spinel phase. In ZBSN, the varistor characteristics were not improved drastically (non-linear coefficient $\alpha\;=\;6{\sim}11$) and independent on microstructure according to Sb/Bi ratio. Doping of Ni to ZBS seemed to form ${V_0}^{\cdot}$ (0.33 eV) as dominant bulk defect. From IS & MS, especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature.

• 전기의세계
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• 제19권4호
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• pp.12-17
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• 1970

BaO.nFe$_{2}$O$_{3}$ Powder ferrite magnet was made by sintering process. The purity of the powder were 99.6% far BaO. 99.5% for Fe$_{2}$O$_{3}$, and the grain size 1-3 micron. The Optimum mixing ratio n=4.4 the optimum density 4.8gr/cm$^{3}$ and the optimum second sintering temperature 1260.deg. C was found. The theoretical bloch wall, dimension of domain and energy per unit volume of BaFe$_{12}$O$_{19}$ were compared with pure Fe. Also, the saturation magnetization and maximum energy product were computed.d.d.