• Corrosion Science and Technology
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• 제18권6호
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• pp.285-291
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• 2019

In this study, the corrosion characteristics of T22 and T92 steel were investigated in 6O₂ + 16CO₂ + 2SO₂ gas environment at 650 ℃. Corrosion characteristics were characterized by weight gain, oxide layer thickness, scanning electron microscope, optical microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction. T22 and T92 steel tended to stagnate oxide layer growth over time. Oxidation kinetics were analyzed using the data of oxide layer thickness, and a regression model was presented. The regression model was significantly acceptable. The corrosion rate between the two steels through the regression model showed significant difference. The T92 steel was approximately twice as large as the time exponent and showed very good corrosion resistance compared to the T22 steel. In both steels, the oxide layer mainly formed a Fe-rich oxide layer composed of hematite (Fe₂O₃), magnetite (Fe₃O₄), and spinel (FeCr₂O₄). Sulfide segregation occurred in the oxide layer due to SO₂ gas. However, the locations of segregation for the T22 and T92 steel were different.

• 한국세라믹학회지
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• 제40권5호
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• pp.447-454
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• 2003

B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+{delta}$의 출발조성비로 99.99%의 순도를 갖는 B $i_2$ $O_3$, PbO, SrC $O_3$, CaC $O_3$, CuO 분말 시약을 사용하여 고상반응법으로 합성하였다. 이렇게 합성된 Bi계 110 K 단일상의 고온초전도 물질을 다시 분말 상태로 만든 후, AgO, A $u_2$ $O_3$, MgO 금속산화물 분말을 각각 50 wt%의 비율로 혼합하였다. AgO, A $u_2$ $O_3$, MgO의 금속분말이 혼합된 시편들을 820~85$0^{\circ}C$로 각각 최종 소결시킨 후, 각 시편들에 대하여 XRD, $T_{c}$, SEM, EDS 등의 실험을 진행하였다. 얻어진 시편들의 $T_{c}$는 순수한 Bi-2223 상보다 낮지만, AgO 금속분말을 50 wt% 혼합한 시편의 임계전이온도가 99.58 K로 A $u_2$ $O_3$나 MgO를 50 wt% 혼합한 시편들보다 더 높게 나타났다. 또한, 표면 입자(grain)의 배열 상태는 AgO 금속분말을 50 wt% 혼합한 시편이 A $u_2$ $O_3$나 MgO를 50 wt% 혼합한 시편들보다 더 치밀화 되는 경향을 나타내었다.내었다.나타내었다.내었다.

• 한국세라믹학회지
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• 제32권5호
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• pp.617-625
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• 1995

In order to reduce reflectance of soda-lime glass having average reflectance of 7.35% and refractive index of 1.53, single (SiO2), double (SiO2/20SiO2-80ZrO2), and triple (SiO2/ZrO2/75SiO2-25ZrO2) layers were designed and fabricated on the glass substrate by Sol-Gel method. Stble sols of SiO2-ZrO2 binary system for antireflective (AR) coatings were synthesized with tetraethyl orthosilicate (TEOS) and zirconium n-butoxide as precursors and ethylacetoacetate (EAcAc) as a chelating agent in an atmosphere environment. Films were deposited on soda-lime glass at the withdrawal rates of 3~11 cm/min using the prepared polymeric sols by dip-coating and they were heat-treated at 45$0^{\circ}C$ for 10 min to obtain homogeneous, amorphous and crack-free films. In case of SiO2-ZrO2 binary system, refractive index of film increased with an increase of ZrO2 mol%. Designed optical constant of films could be obtained through varying the withdrawal rate. In the visible region (380~780nm), reflectance was measured with UV/VIS/NIR Spectrophotometer. Average reflectances of the prepared single-layer [SiO2 (n=1.46, t=103nm)], double-layer [SiO2 (n=1.46, t=1-4nm)/20SiO2-80ZrO2 (n=1.81, t=82nm)], and triple-layer [SiO2 (n=1.46, t=104nm)/ZrO2 (n=1.90, t=80nm)/75SiO2-25ZrO2 (n=1.61, t=94 nm)] were 4.74%, 0.75% and 0.38%, respectively.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.537-544
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• 2011

본 연구에서는 탄화수소가스 중에서 가장 발화온도가 높은 메탄을 대상으로 전이금속 촉매의 산화반응 특성을 수행하였다. 망간의 경우 MnO, $MnO_2$, $Mn_2O_3$, $Mn_3O_4$, $Mn_4O_5$와 같이 다양한 산화가를 나타내므로 산화망간을 선택하여 메탄산화반응실험을 실시하였다. 메탄의 산화를 위한 전이금속 촉매중 망간을 산화물형태로 $Al_2O_3$, $TiO_2$에 담지하였으며, 조촉매로는 Ni, Co 등을 이용하여 활성능과 수명의 향상을 연구하였다. 본 연구에서 촉매 제조는 과잉용액 함침법을 사용하였다. 촉매의 활성화에너지, $T_{50}$, $T_{90}$을 계산하기 위하여 온도와 공간속도에 대한 전환율을 측정하였다. Mn-Co, Mn-Ni의 두성분의 전이금속촉매의 수명이 망간촉매에 비하여 10%이상 증가하고 활성은 약간 감소함을 알 수 있었다.

• 한국작물학회지
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• 제48권3호
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• pp.173-178
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• 2003

제주도에서 쇠무릎을 생약(뿌리) 또는 ecdysteroid(뿌리+포과)를 생산하기 위하여 재배할 경우 적정 인산시비량을 구명하고자 질소시비량 2수준(90, 180kg/ha)과 인산시비량 5수준 (0, 100, 200, 300, 400kg/ha)에서 시험하였던 결과는 다음과 같다. 초장, 엽장, 엽폭, 경직경, 화서당 포과수, 주근장, 주근경은 인산시비량에 유의한 영향을 받지 않았는데, 주당 분지수와 화서수는 무인산구에 비하여 인산 100kg/ha 시비에 의하여 각각 18, 38%증가되었으나 인산 200kg 이상 시비구에서 감소되는 경향이었다. 주당 뿌리수는 인산 200kg에서 18.9개로 가장 많았다. 포과건물수량은 인산 100kg 시비구에서 2.92t/ha로 가장 많았고 200kg 이상 시비구에서 감소되었다. 건근수량은 무인산구에서 2.36t/ha이었던 것이 인산 100, 200kg 시비구에서 각각 3.55, 3.80t/ha 으로 유의성 있게 증가하였다가 300, 400kg 시비구에서는 3.14, 2.86 kg로 감수되었다. 지상부의 인산회수율은 인산 100kg 시비구에서 34.0%이었던 것이 400kg 시비구에서는 7.1%로 감소되었다.

• 한국재료학회지
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• 제23권6호
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• pp.309-315
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• 2013

$GdBa_2Cu_3O_{7-y}$(Gd123) powders were synthesized by the solid-state reaction method using $Gd_2O_3$ (99.9% purity), $BaCO_3$ (99.75%) and CuO (99.9%) powders. The synthesized Gd123 powder and the Gd123 powder with $Gd_2O_3$ addition ($Gd_{1.5}Ba_2Cu_3O_{7-y}$(Gd1.5)) were used as raw powders for the fabrication of Gd123 bulk superconductors. The Gd123 and Gd1.5 bulk superconductors were fabricated by sintering or a top-seeded melt growth (TSMG) process. The superconducting transition temperature ($T_{c,onset}$) of the sintered Gd123 was 93 K and the transition width was as large as 20 K. The $T_{c,onset}$ of the TSMG processed Gd123 was 82 K and the transition width was also as large as 12 K. The critical current density ($J_c$) at 77 K and 0 T of the sintered Gd123 and TSMG processed Gd123 were as low as a few hundreds A/$cm^2$. The addition of 0.25 mole $Gd_2O_3$ and 1 wt.% $CeO_2$ to Gd123 enhanced the $T_c$, $J_c$ and magnetic flux density (H) of the TSMG processed Gd123 sample owing to the formation of the superconducting phase with high flux pinning capability. The $T_c$ of the TSMG processed Gd1.5 was 92 K and the transition width was 1 K. The $J_cs$ at 77 K (0 T and 2 T) were $3.2{\times}10^4\;A/cm^2$ and $2.5{\times}10^4\;A/cm^2$, respectively. The H at 77 K of the TSMG-processed Gd1.5 was 1.96 kG, which is 54% of the applied magnetic field (3.45 kG).

• 한국전기전자재료학회논문지
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• 제19권1호
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• pp.29-34
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• 2006

The effects of $B_2O_3$ addition on the low-temperature sintering behavior and microwave dielectric properties of $(Zn_{0.8}Mg_{0.2})TiO_3$ ceramic system were investigated. Highly dense samples were obtained at the sintering temperatures below $900^{\circ}C$. The $Q{\times}f_o$ values were determined by the microstructures and sintering shrinkages which are affected by the amount of $B_2O_3$ and sintering temperature. Temperature coefficient of resonance frequency($T_f$) changes to a positive value with increasing the amount of $B_2O_3$ due to the increased amount of rutile phase which is one of the reaction products between $(Zn_{0.8}Mg_{0.2})TiO_3$ and $B_2O_3$. For $6.19 moi.{\%}B_2O_3$-added $(Zn_{0.8}Mg_{0.2})TiO_3$ system, it exhibits ${\epsilon}_r$ = 23.5, $Q{\times}f_o$ = 53,000 GHz, and $T_f$ = 0 ppm/$^{\circ}C$ when sintered at $900^{\circ}C$ for 5 h.

• 대한임상검사과학회지
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• 제51권2호
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• pp.205-213
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• 2019

크롬염의 일종인 중크롬산칼륨($K_2Cr_2O_7$)의 세포독성을 배양 NIH3T3 섬유모세포를 재료로 산화적 손상측면에서 조사하였으며, 또한 $K_2Cr_2O_7$의 세포독성에 대한 짚신나물(Agrimonia pilosa var., AP) 추출물의 영향을 세포생존율을 비롯한 LDH 억제능 및 superoxide anion-radical (SAR) 소거능과 같은 항산화 측면에서 분석하였다. 본 실험에서 배양 NIH3T3 섬유모세포에 $25{\sim}35{\mu}M$의 $K_2Cr_2O_7$을 각각 처리한 결과, 처리 농도에 따라 대조군에 비하여 세포생존율이 유의하게 감소되었으며, 이 때 $XTT_{50}$값은 $37.5{\mu}M$에서 나타나 고독성(highly-toxic)인 것으로 나타났다. 또한, 항산화제인 BHT는 $K_2Cr_2O_7$의 세포독성을 유효하게 방어하였다. AP 추출물은 $K_2Cr_2O_7$의 세포독성에 의하여 감소된 세포생존율을 유의하게 증가시킴으로서 세포독성을 방어하였다. 이와 동시에, AP 추출물은 LDH 활성 저해능을 비롯하여 SAR 소거능을 보임으로서 항산화 효과를 나타냈다. 위의 결과로부터 $K_2Cr_2O_7$의 세포독성에 산화적 손상이 관여하고 있는 것을 확인하였고, AP 추출물은 $K_2Cr_2O_7$의 독성을 항산화능에 의하여 효과적으로 방어하였다. 따라서, AP 추출물과 같은 천연성분은 크롬과 같은 산화적 손상과 관련된 독성을 방어할 수 있으므로 산화적 손상에 의한 질환 치료를 위한 물질로 활용적 가치가 크다고 사료된다.

• 한국결정성장학회지
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• 제15권5호
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• pp.188-192
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• 2005

High $T_c(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_2Cu_3O_y[(YNS)-123]$ superconductors with/without $CeO_2$ additive were systematically investigated by the zone melt growth process in air. Cylindrical green rods of (YNS)-123 oxides were fabricated by cold isostatic pressing (CIP) method using rubber mould. A sample prepared by this method showed well-textured microstructure, and $(Y_{0.5}Nd_{0.25}Sm_{0.25})_2BaCuO_5[(YNS)211]$ nonsuperconducting inclusions were uniformly dispersed in large $(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_2Cu_3O_y$[(YNS)123] superconducting matrix. In this study, optimum melting temperature and growth rate were $1100^{\circ}C$ and 3 mm/hr, respectively. The directionally melt-textured (YNS)-123 sample with $CeO_2$ additive showed an onset critical temperature $(T_c)\;T_c{\geq}93K$ and sharp superconducting transition.

• Journal of Korean Neurosurgical Society
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• 제64권6호
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• pp.913-921
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• 2021

Objective : Accurate measurement of T1 slope (a component of T1s minus cervical lordosis [CL]) is often constrained by anatomical limitations. In this situation, efforts should be made to find the exact meaning of T1s-CL and whether there are any alternatives to it. Methods : We enrolled 117 patients who received two-level anterior cervical discectomy and fusion (ACDF). Occipital slope, C2 slope (C2s), C7 slope (C7s), T1, O-C2 angle (O-C2A), C2-7 angle (C2-7A), O-C7 angle (O-C7A), T1s-CL, C7-T1 angle (C7-T1A), and C2-7 sagittal vertical axis were measured. We determined 16° (T1s-CL) as the reference point for dividing subjects into the mismatch group and the balance group, and a comparative analysis was performed. Results : The mean value of C7-T1A was constantly maintained within 2.6° peri-operatively. In addition, C2s and T1s-CL showed the same absolute change (Δ|0.8|°). The mean values of T1s-CL of the mismatch and balance groups were 23.0° and 7.6°, respectively. The five factors with the largest differences between the two groups were as follows : C2s (Δ13.3°), T1s-CL (Δ15.4°), O-C2A (Δ8.7°), C2-7A (Δ14.7°), and segmental angle (Δ7.9°) before surgery. Only four factors showed statistically significant change between the two groups after ACDF : T1s-CL (Δ4.0° vs. Δ0.2°), C2s (Δ3.2° vs. Δ0.7°), O-C2A (Δ2.6° vs. Δ1.3°), C2-7A (Δ6.3° vs. Δ1.3°). A very strong correlation between T1s-CL and C2s was also found (r=|0.88-0.96|). Conclusion : C2s itself may be the essential key to represent T1s-CL. The amounts and directions of change of these two factors (T1s-CL and C2s) were also almost identical. The above phenomenon was re-confirmed once again through the correlation analysis.