• 한국압력기기공학회 논문집
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• 제15권2호
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• pp.31-39
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• 2019

Cracked component analysis is needed for structural integrity analysis under seismic loading. Under large amplitude cyclic loading conditions, the change in material properties can be complex, depending on the magnitude of plastic strain. Therefore the cracked component analysis under cyclic loading should consider appropriate cyclic hardening model. This study introduces a procedure for determining an appropriate cyclic hardening model for cracked component analysis. The test material was nuclear-grade TP316 stainless steel. The material cyclic hardening was simulated using the Chaboche combined hardening model. The kinematic hardening model was determined from standard tensile test to cover the high and wide strain range. The isotropic hardening model was determined by simulating C(T) test under cyclic loading using ABAQUS debonding analysis. The suitability of the material hardening model was verified by comparing load-displacement curves of cyclic C(T) tests under different load ratios.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 추계학술논문요약집
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• pp.379-379
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• 2018

MXenes are a new family of 2D transition metal carbide nanosheets analogous to graphene (Lv et al., 2017; Sun et al., 2018). Due to the easy availability, hydrophilic behavior, and tunable chemistry of MXenes, their use in applications for environmental pollution remediation such as heavy metal adsorption has recently been explored (Li et al., 2017). In this study, three-dimensional (3D) MXene ($Ti_3C_2T_x$) films with high adsorption capacity, good mechanical strength, and high selectivity for specific radionuclide from aquose solution were successfully fabricated by a polymeric precursor method using vacuum-assisted filtration. The highest removal efficiency on the films was 99.54%, 95.61%, and 82.79% for $Sr^{2+}$, $Co^{2+}$, and $Cs^+$, respectively, using a film dosage of 0.06 g/ L in the initial radionuclide solution (each radionuclide concentration = 1 mg/L and pH = 7.0). Especially, the adsorption process reached an equilibrium within 30 min. The expanded interlayer spacing of $Ti_3C_2T_x$ sheets in MXene films showed excellent radionuclide selectivity ($Cs^+$ and/or $Sr^{2+}/Co^{2+}$) (Simon, 2017). Besides, the MXene films was not only able to be easily retrieved from an aqueous solution by filtration after decontamination processes, but also to selectively separate desired target radionuclides in the solutions. Therefore, the newly developed MXene ($Ti_3C_2T_x$) films has a great potential for radionuclide removal from aqueous solution.

• 한국재료학회지
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• 제32권5호
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• pp.264-269
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• 2022

Ti₃C₂T_x MXene, which is a representative of the two-dimensional MXene family, is attracting considerable attention due to its remarkable physicochemical and mechanical properties. Despite its strengths, however, it is known to be vulnerable to oxidation. Many researchers have investigated the oxidation behaviors of the material, but most researches were conducted at high temperatures above 500 ℃ in an oxidation-retarding environment. In this research, we studied changes in the structural and electrical properties of Ti₃C₂T_x MXene induced by low-temperature heat treatments in ambient conditions. It was found that a number of TiO₂ particles were formed on the MXene surface when it was mildly heated to 200 ℃. Heating the material to higher temperatures, up to 400 ℃, the phase transformation of Ti₃C₂T_x MXene to TiO₂ was accelerated, resulting in a TiO₂/Ti₃C₂T_x hybrid. Consequently, the metallic nature of pure Ti₃C₂T_x MXene was transformed to semiconductive behavior upon heat-treating at ≥ 200 ℃. The results of this research clearly demonstrate that Ti₃C₂T_x MXene may be easily oxidized even at low temperatures once it is exposed to air.

• 광물과산업
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• 제25권
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• pp.1-10
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• 2012

본 연구에서는 경북 울진 보암광산의 리튬광을 대상으로 고품위 리튬 정광 생산을 위한 부유선별 연구를 수행하였다. 리튬의 근원광물은 Lepidolite (0.99% $Li_2O$)이며, 주요 맥석광물은 $SiO_X$를 포함하는 규산염 광물(quartz, muscovite)과 방해석(Calcite)이 존재하였다. 따라서 음이온포수제를 이용하여 방해석을 먼저 부유시켜 제거하고, 규산염 광물을 억제하고 리튬 광물을 부유시키는 공정을 적용하였다. 리튬광물 부유선별에서 포수제는 아민계통의 양이온 포수제(Armac-T, Armac-C, Armafloat-18, Armafloat-1597) 중 Armac-T가 가장 효과적이었다. 실험결과 최적 조건인 포수제(Armac-T) 100g/t, 기포제(AF65) 50g/t, 억제제($Na_2SiO_3$) 600g/t, (Lactic acid) 100g/t, 광액농도 20%solids, pH 5.5 그리고 정선횟수 2회에서 $Li_2O$의 품위와 회수율이 각각 4.33%와 80.3%인 결과를 얻었다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2007년도 High Temperature Superconductivity Vol.XVII
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• pp.9-9
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• 2007

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2007년도 High Temperature Superconductivity Vol.XVII
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• pp.21-21
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• 2007

• Asian Pacific Journal of Cancer Prevention
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• 제15권5호
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• pp.2353-2358
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• 2014

Purpose: We aimed to detect the expression of HIF-1${\alpha}$, VEGF, HPSE-1 and CD31 in SKOV3 xenografts in nude mice treated with different doses of ionizing radiation, trying to explore the possible mechanism of hypoxia and radioresistance. Methods: Nude mice bearing SKOV3 xenografts were randomly divided into 4 groups: Group A (control group, no ionizing radiation), Group B (treated with low dose of ionizing radiation: 50cGy), Group C (treated with high dose of ionizing radiation: 300cGy), Group D ( combined ionizing radiation, treated with ionizing radiation from low dose to high dose : 50cGy first and 300cGy after 6h interval). The mRNA levels of HIF-1 and VEGF in each group were detected by real time polymerase chain reaction, while HPSE-1 expression was measured by ELISA. The microvessel density (MVD) and hypoxic cells were determined through immunohistochemical (IHC) staining of CD31 and HIF-1a. Results: Significant differences of HIF-1${\alpha}$ mRNA level could be found among the 4 groups (F=74.164, P<0.001): Group C>Group A>Group D> Group B. The mRNA level of VEGF in Group C was significantly higher than in the other three groups (t=-5.267, P=0.000), while no significant difference was observed among Group A, B and D (t=1.528, 1.588; P=0.205, 0.222). In addition, the MVD was shown to be the highest in Group C (t=6.253, P=0.000), whereas the HPSE-1 level in Group A was lower than in Group B (t=14.066, P=0.000) and higher than in Group C (t=-21.919, P=0.000), and similar with Group D (t=-2.066, P=0.058). Through IHC staining of HIF-1a, the expression of hypoxic cells in Group A was (++), Group B was (+), Group C was (+++) and Group D was (+). Conclusion: Ionizing radiation with lowerdoses might improve tumor hypoxia through inhibiting the expression of HIF-1 and HPSE-1, whereas higherdoses worsen tumor hypoxic conditions by up-regulating HIF-1${\alpha}$, HPSE-1, VEGF and CD31 levels. A protocol of low-dose ionizing radiation followed by a high-dose irradiation might at least partly improve tumor hypoxia and enhance radiosensitivity.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.133-133
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• 1999

We have fabricated and tested a simple circuit of the rapid single-flux-quantum(RSFQ) four-stage shift register using a single layer high-T$_c$ superconducting (HTS) YBa$_2Cu_3O_{7-x}$ (YBCO) thin film structure with 9 step-edge Josephson junctions. The circuit includes two read superconducting quantum interference devices(SQUID) and four stages. To establish a robust HTS RSFQ device fabrication process, we have focussed the reproducible process of sharp and straight step-edge formation as well as the ratio of film thickness to step height t/h. The spread of step-edge junction parameters was measured from each13 junctions with t/h=l/3, l/2, and 2/3 at various temperatures. We have demonstrated the simplified operation of the shift register at 65 K..

• 한방재활의학과학회지
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• 제31권1호
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• pp.81-93
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• 2021

Objectives The objective of the study was to investigate effects of ChondroT by improvement of blood metabolites in high-fat diet (HFD)-induced hyperlipidemia rat model. Methods Sprague-Dawley rats were randomly assigned to intact, control, simvastatin, and CT100, CT200 and CT400 (each n=6). For observing cholesterol change, animals were first fed high fat diet for 5 weeks and then high fat diet and drugs for 3 weeks. At the end of the experiment, total cholesterol, triglyceride, high density lipoprotein-cholesterol (HDL-C) and low density lipoprotein-cholesterol (LDL-C) were analyzed by obtained blood collection. Further, amplified leptin, peroxisome proliferator activated receptor (PPAR) and adiponectin DNA were observed by reverse transcription polymerase chain reaction analysis. Results Observing the effect of ChondroT on the change of lipid metabolism in hyperlipidemia-induced rats, triglyceride and total cholesterol were significantly decreased in SV100 group, HDL-C was significantly increased in SV100, CT100 and CT200 groups, and LDL-C was significantly decreased in SV100, CT100, CT200 and CT400 groups, compared to the control group. Leptin level in hyperlipidemia-induced rats was significantly decreased in CT100 and CT200 groups, compared to the control group. The effect of ChondroT on adiponectin level in hyperlipidemia-induced rats was significantly increased in SV100, CT100 and CT200 groups. PPAR level in hyperlipidemia-induced rats was significantly decreased in SV100, CT200 and CT400 groups. Platelete activating factor level in hyperlipidemia-induced rats was significantly decreased in CT100 and CT200 groups. Conclusions Based on these results, it could be suggested that ChondroT has certain effects of improving blood metabolites in HFD-induced hyperlipidemia.

• Applied Science and Convergence Technology
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• 제25권4호
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• pp.81-84
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• 2016

InP/InGaP quantum structures (QSs) grown on GaAs substrates by a migration-enhanced molecular beam epitaxy method were studied as a function of growth temperature (T) using photoluminescence (PL) and emission-wavelength-dependent time-resolved PL (TRPL). The growth T were varied from $440^{\circ}C$ to $520^{\circ}C$ for the formation of InP/InGaP QSs. As growth T increases from $440^{\circ}C$ to $520^{\circ}C$, the PL peak position is blue-shifted, the PL intensity increases except for the sample grown at $520^{\circ}C$, and the PL decay becomes fast at 10 K. Emission-wavelength-dependent TRPL results of all QS samples show that the decay times at 10 K are slightly changed, exhibiting the longest time around at the PL peak, while at high T, the decay times increase rapidly with increasing wavelength, indicating carrier relaxation from smaller QSs to larger QSs via wetting layer/barrier. InP/InGaP QS sample grown at $460^{\circ}C$ shows the strongest PL intensity at 300 K and the longest decay time at 10 K, signifying the optimum growth T of $460^{\circ}C$.