• Transactions on Electrical and Electronic Materials
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• 제17권4호
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• pp.227-230
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• 2016

Zn_xMn_3-xO₄ (0.95≤x≤1.20) specimens were prepared using a conventional solid state reaction method. All specimens were sintered in air at 1,200℃ for 12 h, cooled at a rate of 2℃/min to 800℃, and subsequently quenched to room temperature. We investigated the electrical properties of Zn_xMn_3-xO₄ specimens with various amounts of ZnO for use as IR detectors. At a composition of x≥1.15, the ZnO phase precipitates beside the spinel structure. The electrical resistivity at room temperature, activation energy, responsivity, and detectivity of a Zn_1.10Mn_1.90O₄ specimen are 653.2 kΩ-cm, 0.392 eV, 0.016 V/W, and 7.52×10³ cmHz^1/2/W, respectively.

• Journal of applied mathematics & informatics
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• 제40권5_6호
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• pp.1181-1198
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• 2022

In this paper we are concerned with the number of fuzzy subgroups of a finite abelian p-group ℤ_p^m × ℤ_pⁿ × ℤ_p^ℓ of rank three with order p^m+n+ℓ. We obtain a recurrence relation for the number of fuzzy subgroups of a finite abelian p-group ℤ_p^m × ℤ_pⁿ × ℤ_p^ℓ. In order to show that using this recurrence relation, one can find explicit formulas for the number of fuzzy subgroups of ℤ_p^m × ℤ_pⁿ × ℤ_p^ℓ consecutively, we give explicit formulas for the number of fuzzy subgroups of ℤ_p^m × ℤ_pⁿ × ℤ_p^ℓ where (n, ℓ) = (1, 1), (2, 1), (3, 1), (4, 1), (5, 1), (2, 2), (3, 2), (4, 2), (5, 2).

• 방사성폐기물학회지
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• 제18권3호
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• pp.355-362
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• 2020

The corrosion behavior of the Inconel X-750 alloy was investigated for its potential application under a Cl₂-O₂ mixed gas flow in an Ar atmosphere. The corrosion rate was found to be negligible at temperatures up to 400℃ under a flow rate of 30 mL·min^-1 Cl₂ + 170 mL·min^-1 Ar, whereas an exponential increase was observed in the corrosion rate at temperatures greater than 500℃. The suppression of the corrosion reaction due to the presence of O₂ was verified experimentally at flow rates of 30 mL·min^-1 Cl₂ (4.96 g·m^-2·h^-1), 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂ (2.02 g·m^-2 ·h^-1), and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂ (1.34 g·m^-2·h^-1) under a constant Ar flow rate of 170 mL·min^-1 at 600℃ for 8 h. The surface morphology analysis results revealed that porous surfaces with tunnel-type holes were produced under the Cl₂-O₂ mixed-gas condition. Furthermore, the effects of the Cl₂ flow rate on the corrosion rate were investigated, indicating that its impact was negligible within the range of 5-30 mL·min^-1 Cl₂ at 600℃.

• 대한화학회지
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• 제52권6호
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• pp.614-621
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• 2008

• Elastomers and Composites
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• 제59권1호
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• pp.1-7
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• 2024

Nanorod graphitic carbon nitride (g-C₃N₄) was synthesized by reacting melamine (C₃H₆N₆) with trithiocyanuric acid (C₃H₃N₃S₃) in distilled water for 10 h at room temperature. The resulting mixture was calcined at 550℃ for 2 h in an electric furnace under an air atmosphere. Nanorod g-C₃N₄/Ag₃PO₄ composites were prepared by adding nanorod graphitic carbon nitride (g-C₃N₄) powder, silver nitrate (AgNO₃), ammonia (NH₃·H₂O, 25.0-30.0%), and sodium hydrogen phosphate (Na₃HPO₄) to distilled water. The samples were characterized via X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The photocatalytic activities of the nanorod g-C₃N₄/Ag₃PO₄ composites were demonstrated via the degradation of organic dyes, such as methylene blue and methyl orange, under blue light-emitting diode irradiation and evaluated using UV-vis spectrophotometry.

• 한국재료학회지
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• 제7권10호
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• pp.871-871
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• 1997

(1-x)CaTiO/sub 3/-xLa(Zn/sub 1/2/Ti/sub 1/2/)O/sub 3/의 마이크로 유전특성을 조사하였다. x가 증가함에 따라 비유전율과 공진주파수의 온도계수는 감소하였으며, Qㆍf/sub 0/는 증가하였다. 그 결과 x=0.5인 (Ca/sub 0.5/La/sub 0.5/)(Ti/sub 0.75/Zn/sub 0.25/)O/sub 3/의 조성에서 ε/sub r/=51, Qㆍf/sub 0/=38,000 (at 7 GHz), τ/sub f/=+5ppm/℃의 유전특성이 나타났다. (Ca/sub 0.5/La/sub 0.5/)(Ti/sub 0.75/Zn/sub 0.25/) O/sub 3/조성의 소결온도를 저하시키기 위하여 Bi/sub 2/O/sub 3/를 주조성으로한 소결체를 첨가하여 소결 및 유전특성을 조사하였다. 1wt% 0.76Bi/sub 2/O/sub 3/-0.24NiO가 첨가된 경우 소결온도는 150℃ 낮아졌으며, 비유전율 (ε/sub r/), 공진주파수의 온도계수(τ/sub f), Qㆍf/sub 0/가 각각 50+5ppm/℃, 35,000인 마이크로파 유전특성이 얻어졌다. 또한 3wt%의 0.76Bi/sub 2/O/sub 3/-0.24NiO가 첨가된 경우 소결온도는 200℃ 저하되었고, 비유전율 (ε/sub r/)과 공진주파수의 온도계수 (τ/sub f)는 변하기 않았으나, Qㆍf/sub 0/값이 38,000에서 25,000으로 저하되었다.

• Korean Journal of Radiology
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• 제23권4호
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• pp.446-454
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• 2022

Objective: To evaluate whether hyperoxia-induced ΔR₁ (hyperO₂ΔR₁) can accurately identify histological infarction in an acute cerebral stroke model. Materials and Methods: In 18 rats, MRI parameters, including hyperO₂ΔR₁, apparent diffusion coefficient (ADC), cerebral blood flow and volume, and ¹⁸F-fluorodeoxyglucose uptake on PET were measured 2.5, 4.5, and 6.5 hours after a 60-minutes occlusion of the right middle cerebral artery. Histological examination of the brain was performed immediately following the imaging studies. MRI and PET images were co-registered with digitized histological images. The ipsilateral hemisphere was divided into histological infarct (histological cell death), non-infarct ischemic (no cell death but ADC decrease), and nonischemic (no cell death or ADC decrease) areas for comparisons of imaging parameters. The levels of hyperO₂ΔR₁ and ADC were measured voxel-wise from the infarct core to the non-ischemic region. The correlation between areas of hyperO₂ΔR₁-derived infarction and histological cell death was evaluated. Results: HyperO₂ΔR₁ increased only in the infarct area (p ≤ 0.046) compared to the other areas. ADC decreased stepwise from non-ischemic to infarct areas (p = 0.002 at all time points). The other parameters did not show consistent differences among the three areas across the three time points. HyperO₂ΔR₁ sharply declined from the core to the border of the infarct areas, whereas there was no change within the non-infarct areas. A hyperO₂ΔR₁ value of 0.04 s^-1 was considered the criterion to identify histological infarction. ADC increased gradually from the infarct core to the periphery, without a pronounced difference at the border between the infarct and non-infarct areas. Areas of hyperO₂ΔR₁ higher than 0.04 s^-1 on MRI were strongly positively correlated with histological cell death (r = 0.862; p < 0.001). Conclusion: HyperO₂ΔR₁ may be used as an accurate and early (2.5 hours after onset) indicator of histological infarction in acute stroke.

• 한국유기농업학회지
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• 제29권4호
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• pp.601-612
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• 2021

본 연구는 켄터키블루그래스와 토끼풀을 다른 파종방법 각 산파와 점파로 파종 비율(1:0, 1:2, 1:3, 3:1, 2:1, 0:1)을 다르게 하여 종자별 발아특성을 살펴보았다. 이러한 결과를 토대로 켄터키블루그래스와 토끼풀의 순기능이 효과적으로 발휘될 수 있는 적절한 파종비율 및 방법을 규명함으로 조성, 유지관리에 활용할 수 있는 기초자료를 얻기 위해 수행되었다. 그 결과를 요약하면 다음과 같다. 첫째, 산파한 경우 토끼풀과 켄터키블루그래스 모두 종자 비율이 상대적으로 클수록 높은 발아율을 보였으며, 토끼풀과 켄터키블루그래스의 비율이 2:1이 되는 처리구에서 두 종의 발아율이 비슷한 수준을 유지하는 것으로 나타났다. 둘째, 점파한 경우 산파시와 마찬가지로 파종비율이 높을수록 종자발아율이 높았으나 반대로 켄터키블루그래스가 토끼풀 비율의 2배 정도로 유지될 때 두 종자의 발아율이 비슷한 것으로 나타났다. 셋째, 파종방법에 있어서는 켄터키블루그래스와 토끼풀을 혼합하여 파종할 경우 점파보다는 산파하는 것이 발아율 증가에 미치는 영향이 큰 것으로 드러났다. 종합적으로 정리하면, 산파와 점파, 모두 종자의 파종비율이 높을수록 높은 발아율을 가지는 것으로 나타났으나 점파 시 켄터키블루그래스:토끼풀(1:2), 산파 시 켄터키블루그래스:토끼풀(1:2)과 같이 적정 비율범위를 벗어날 경우 한 종이 우점하여 나머지 종의 발아를 억제할 가능성이 있는 것으로 드러났다. 따라서 산파 시에는 토끼풀 종자를 켄터키블루그래스 종자의 2배 이상이 되지 않도록 점파 시에는 역으로 켄터키블루그래스 종자가 2배 이상이 되도록 파종하는 것이 바람직한 것으로 판단되었다. 이러한 연구의 결과는 골프장, 공원 등에 있어 켄터키블루그래스와 토끼풀을 활용하여 녹지 조성 및 유지관리에 적용 가능할 것으로 기대된다. 다만, 본 연구는 자연조건이 아닌 온실 안에서 충분한 관수 조건하에서 이루어져 실질적 파종지 적용에 있어서 연구결과와 상이할 가능성이 있어 외부환경에서의 현장적용 검증 단계가 필요하다. 또한, 연구가 단기간에 발아율 대상으로 한정되어 발아 이후의 장기적 생육 모니터링 역시 필요할 것으로 사료된다.

• 한국전기전자재료학회논문지
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• 제16권9호
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• pp.775-782
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• 2003

In the study, the total conductivies in [(Ce $O_2$)$_{1-x}$ (Zr $O_2$)$_{x}$]$_{0.8}$(Sm $O_{1.5}$)$_{0.2}$ (x- 0, 0.05, 0.1, 0.2) solid solution were measured as a function of temperature and oxygen partial pressure between 80$0^{\circ}C$ and 1,00$0^{\circ}C$ using 4-probe d.c method. Under pure oxygen atmospere, the oxygen ionic conductivity of [(Ce $O_2$)$_{1-x}$ (Zr $O_2$)$_{x}$]$_{0.8}$(Sm $O_{1.5}$)$_{0.2}$ decreased with the concentration of Zr $O_2$At high oxygen partial pressure, the electrical conductivity is almost independent of oxygen partial pressure and decreased with the increase in Zr content. However, the electrical conductivity increase with decreasing oxygen partial pressure and is almost independent of Zr content at low oxygen partial pressure. Empirically, Total conductivity( $\sigma$ ) was expressed by the p$o_{2}$ -independent conductivity as $\sigma$$_{i}$, and the $p_{-1/4}$ $o_{2}$sup -dependent part as $\sigma$$_{e}$. Total, ionic and electronic conductivities fitted by data enabled to determine the transference number. The ionic transference number( $t_{i}$ ) decreased while the electronic transference( $t_{e}$ ) increase with the increase in Zr content and p$o_{2}$.

• 천문학회보
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• 제46권1호
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• pp.34.4-35
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• 2021

We present the TESS photometry and our high-resolution spectra of the semi-detached Algol EW Boo. For an orbital period study, we collected all available times of minima including ours for the last 30 years. It is found that the eclipse timing variation of the system can be represented by a periodic oscillation of 18.5±1.0 yr plus a secular period increase with a rate of [dP/dt]_orb=-6(±3)×10^-8 d yr^-1. From our observed spectra, the effective temperature of the primary star was determined to be T_eff,1=8560±118 K. From a simultaneous analysis of the TESS light and our double-lined radial velocity curves, the absolute masses, radii, and luminosities are M₁=2.30±0.07M_⊙, M₂=0.38±0.01M_⊙, R₁=1.92±0.02 R_⊙, R₂=1.27±0.01 R_⊙, L₁=1.92±0.02 L_⊙, and L₂=0.752±0.007 L_⊙, respectively. Multiple frequency analyses were carried out for the light residuals after subtracting the binary star model. We detected a total of 75 frequencies in the region of 16.50-104.8 day-1. Our results demonstrate that the more hotter primary star of EW Boo is a δ Sct pulsator by considering its position in the δ Scuti region of the Cepheid instability strip and pulsational characteristics.