Analysis of the Effects of Al on the Ductile-to-Brittle Transition Behavior of Ferritic Heat-Resistant Stainless Steels

Yingbo Zhang,Dening Zou,Xiaoqiao Wang,Fengshe Xia,Yong Wang,Wei Zhang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7

The effect of Al content on the microstructure and ductile-brittle transition temperature (DBTT) of 18Cr–Al–Si ferritic heatresistantstainless steel have been studied by Charpy impact testing over temperatures ranging from 20 to 90 ℃. Charpy impacttest results show that DBTT increased with increasing Al content. Meanwhile, fracture morphology changed with increasingAl content, where the amount of dimples decreased and cleavage facets increased, indicating increases in the tendency forbrittle fracture. Furthermore, ferrite grain size, volume fraction and size of (Cr, Fe)23C6 carbides increased with increasingAl content, which led to decreasing toughness and increasing DBTT.

SOME RESULTS OF p-BIHARMONIC MAPS INTO A NON-POSITIVELY CURVED MANIFOLD

Yingbo Han,Wei Zhang 대한수학회 2015 대한수학회지 Vol.52 No.5

In this paper, we investigate p-biharmonic maps u : (M, g) → (N, h) from a Riemannian manifold into a Riemannian manifold with nonpositive sectional curvature. We obtain that if ∫M |τ(u)|a+pdvg < ∞ and ∫M |d(u)|2dvg < ∞, then u is harmonic, where a ≥ 0 is a nonnegative constant and p ≥ 2. We also obtain that any weakly convex p-biharmonic hypersurfaces in space form N(c) with c ≤ 0 is minimal. These results give affirmative partial answer to Conjecture 2 (generalized Chen’s conjecture for p-biharmonic submanifolds).

Thermal Stability of GH4065A Superalloy Based on Microstructural and Performance Evolution Following Long-Term Aging

Yingbo Bai,Rui Zhang,Chuanyong Cui,Yizhou Zhou,Xiaofeng Sun 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.2

This study investigates the thermal stability of a GH4065A superalloy at intermediate temperatures by conducting long-termaging treatments for 100–6000 h at 700–800 °C. Secondary γ′-phase coarsening and intergranular M6Ccarbide precipitationoccurred during aging. The activation energy for secondary γ′-phase coarsening was 259.89 ± 25.45 kJ mol−1, suggestingthat this process was predominantly controlled by elemental diffusion. The tensile strength at a testing temperature of 700 °Cwas stably above 1200 MPa for the alloys aged at 700 °C but continuously declined as the aging temperature increased, witha direct correlation identified between the secondary γ′-phase coarsening and strength reduction upon aging. Increasing theaging temperature transitioned the deformation mechanism from Orowan bowing around the γ′ phase to dislocation slipthrough the broadened matrix channels, leading to decreased strength. Long-term aging effectively eliminated intermediatetemperatureintergranular brittle fracture. The elongation to failure at a testing temperature of 700 °C increased by approximately35% after aging at 800 °C for 6000 h, attributed to grain-boundary diffusion of W and Mo and intragranular softening,which improved the deformation coordination ability at the grain boundaries. Finally, the precipitation of intergranular M6Cparticles after prolonged aging promoted plastic deformation via micropore aggregation.

SOME RESULTS OF p-BIHARMONIC MAPS INTO A NON-POSITIVELY CURVED MANIFOLD

HAN, YINGBO,ZHANG, WEI Korean Mathematical Society 2015 대한수학회지 Vol.52 No.5

In this paper, we investigate p-biharmonic maps u : (M, g) $\rightarrow$ (N, h) from a Riemannian manifold into a Riemannian manifold with non-positive sectional curvature. We obtain that if ${\int}_M|{\tau}(u)|^{{\alpha}+p}dv_g$ < ${\infty}$ and ${\int}_M|d(u)|^2dv_g$ < ${\infty}$, then u is harmonic, where ${\alpha}{\geq}0$ is a nonnegative constant and $p{\geq}2$. We also obtain that any weakly convex p-biharmonic hypersurfaces in space formN(c) with $c{\leq}0$ is minimal. These results give affirmative partial answer to Conjecture 2 (generalized Chen's conjecture for p-biharmonic submanifolds).

Stem-leaf saponins from Panax notoginseng counteract aberrant autophagy and apoptosis in hippocampal neurons of mice with cognitive impairment induced by sleep deprivation

Yin Cao,Yingbo Yang,Hui Wu,Yi Lu,Shuang Wu,Lulu Liu,Changhong Wang,Fei Huang,Hailian Shi,Beibei Zhang,Xiaojun Wu,Zhengtao Wang 고려인삼학회 2020 Journal of Ginseng Research Vol.44 No.3

Backgroud: Sleep deprivation (SD) impairs learning and memory by inhibiting hippocampal functioningat molecular and cellular levels. Abnormal autophagy and apoptosis are closely associated with neurodegenerationin the central nervous system. This study is aimed to explore the alleviative effect and theunderlying molecular mechanism of stemeleaf saponins of Panax notoginseng (SLSP) on the abnormalneuronal autophagy and apoptosis in hippocampus of mice with impaired learning and memory inducedby SD. Methods: Mouse spatial learning and memory were assessed by Morris water maze test. Neuronalmorphological changes were observed by Nissl staining. Autophagosome formation was examined bytransmission electron microscopy, immunofluorescent staining, acridine orange staining, and transienttransfection of the tf-LC3 plasmid. Apoptotic event was analyzed by flow cytometry after PI/annexin Vstaining. The expression or activation of autophagy and apoptosis-related proteins were detected byWestern blotting assay. Results: SLSP was shown to improve the spatial learning and memory of mice after SD for 48 h,accomanied with restrained excessive autophage and apoptosis, whereas enhanced activation of phosphoinositide3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway in hippocampalneurons. Meanwhile, it improved the aberrant autophagy and apoptosis induced by rapamycinand re-activated phosphoinositide 3-kinase/Akt/mammalian target of rapamycin signaling transductionin HT-22 cells, a hippocampal neuronal cell line. Conclusion: SLSP could alleviate cognitive impairment induced by SD, which was achieved probablythrough suppressing the abnormal autophagy and apoptosis of hippocampal neurons. The findings maycontribute to the clinical application of SLSP in the prevention or therapy of neurological disordersassociated with SD.

Phytochemical analysis of Panax species: a review

Yuangui Yang,Zhengcai Ju,Yingbo Yang,Yanhai Zhang,Li Yang,Zhengtao Wang 고려인삼학회 2021 Journal of Ginseng Research Vol.45 No.1

Panax species have gained numerous attentions because of their various biological effects on cardiovascular, kidney, reproductive diseases known for a long time. Recently, advanced analytical methods including thin layer chromatography, high-performance thin layer chromatography, gas chromatography, high-performance liquid chromatography, ultra-high performance liquid chromatography with tandem ultraviolet, diode array detector, evaporative light scattering detector, and mass detector, two-dimensional high-performance liquid chromatography, high speed counter-current chromatography, high speed centrifugal partition chromatography, micellar electrokinetic chromatography, high-performance anion-exchange chromatography, ambient ionization mass spectrometry, molecularly imprinted polymer, enzyme immunoassay, <SUP>1</SUP>H-NMR, and infrared spectroscopy have been used to identify and evaluate chemical constituents in Panax species. Moreover, Soxhlet extraction, heat reflux extraction, ultrasonic extraction, solid phase extraction, microwave-assisted extraction, pressurized liquid extraction, enzyme-assisted extraction, acceleration solvent extraction, matrix solid phase dispersion extraction, and pulsed electric field are discussed. In this review, a total of 219 articles published from 1980 to 2018 are investigated. Panax species including P. notoginseng, P. quinquefolius, sand P. ginseng in the raw and processed forms from different parts, geographical origins, and growing times are studied. Furthermore, the potential biomarkers are screened through the previous articles. It is expected that the review can provide a fundamental for further studies.

Stem-leaf saponins from Panax notoginseng counteract aberrant autophagy and apoptosis in hippocampal neurons of mice with cognitive impairment induced by sleep deprivation

Cao, Yin,Yang, Yingbo,Wu, Hui,Lu, Yi,Wu, Shuang,Liu, Lulu,Wang, Changhong,Huang, Fei,Shi, Hailian,Zhang, Beibei,Wu, Xiaojun,Wang, Zhengtao The Korean Society of Ginseng 2020 Journal of Ginseng Research Vol.44 No.3

Backgroud: Sleep deprivation (SD) impairs learning and memory by inhibiting hippocampal functioning at molecular and cellular levels. Abnormal autophagy and apoptosis are closely associated with neurodegeneration in the central nervous system. This study is aimed to explore the alleviative effect and the underlying molecular mechanism of stem-leaf saponins of Panax notoginseng (SLSP) on the abnormal neuronal autophagy and apoptosis in hippocampus of mice with impaired learning and memory induced by SD. Methods: Mouse spatial learning and memory were assessed by Morris water maze test. Neuronal morphological changes were observed by Nissl staining. Autophagosome formation was examined by transmission electron microscopy, immunofluorescent staining, acridine orange staining, and transient transfection of the tf-LC3 plasmid. Apoptotic event was analyzed by flow cytometry after PI/annexin V staining. The expression or activation of autophagy and apoptosis-related proteins were detected by Western blotting assay. Results: SLSP was shown to improve the spatial learning and memory of mice after SD for 48 h, accomanied with restrained excessive autophage and apoptosis, whereas enhanced activation of phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway in hippocampal neurons. Meanwhile, it improved the aberrant autophagy and apoptosis induced by rapamycin and re-activated phosphoinositide 3-kinase/Akt/mammalian target of rapamycin signaling transduction in HT-22 cells, a hippocampal neuronal cell line. Conclusion: SLSP could alleviate cognitive impairment induced by SD, which was achieved probably through suppressing the abnormal autophagy and apoptosis of hippocampal neurons. The findings may contribute to the clinical application of SLSP in the prevention or therapy of neurological disorders associated with SD.

Effect of Cooling Rate on Solidification and Segregation Characteristics of 904L Super Austenitic Stainless Steel

Yunong Li,Dening Zou,Wanwan Chen,Yingbo Zhang,Wei Zhang,Fanghong Xu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

To study and understand the solidification behavior of super austenitic stainless steel under different cooling rates and segregationlaws of alloying elements is of great significance to optimize the subsequent diffusion annealing homogenizationtreatment process and improve product quality. According to Thermo-Calc thermodynamic simulation results and combinedwith high temperature laser confocal scanning electron microscope (HT-CSLM), the tissue morphology of 904L superaustenitic stainless steel was observed in-situ during solidification. The solidification path of the test steel was determinedvia calculation with the Scheil-Gulliver model. Microscopy techniques, including true color microscopy, scanning electronmicroscopy (SEM), energy dispersive spectrometer (EDS), and electron probe microanalyzer (EPMA) were used to analyzethe influence of different cooling rates (6 ℃/min, 50 ℃/min, and 100 ℃/min) on the solidification structure and determine themain distribution law of alloying elements. This analysis determined that the solute distribution coefficient (K) of Cr, Mn,Mo, Cu, and Si elements is less than 1 during the solidification process, which means that they will accumulate in the liquidphase. Among them, elemental Mo segregation is the most severe, while elemental Ni hardly segregates. As the cooling rateincreases, the crystallization temperature of the test steel decreases, and the secondary dendrite arm spacing λ2 decreases,the concentration of Mo in the residual liquid phase increases.

Easily prepared graphene-modified melamine sponge and its solar-aided adsorption performance on viscous oil

Fan Mingkan,Liu Huie,Guo Qilin,Zhang Yingbo,Chen Shuang,Zhang Wanqing,Shen Qi,Dou Xiangyan 한국탄소학회 2024 Carbon Letters Vol.34 No.3

Graphene-modified melamine sponges (RGO-MSs) were prepared, as adsorbents with photothermal conversion ability, utilizing solar energy to achieve heavy oil temperature rise, viscosity reduction, and efficient adsorption recovery of highly viscous oil. The RGO-MSs were prepared through a simple impregnation method. The photothermal performance and heavy oil adsorption performances of RGO-MSs with different densities and thicknesses were observed. It was found that as the density increases, the thermal conductivity of RGO-MS increases too, leading to the increase of the average oil absorption rate. The reduction of thickness is beneficial to improving of the adsorption rate. The prepared RGO-MS with a density of 21.5 mg/cm−3 and a height of 1 cm (RGO-MS-3-1) shows excellent mechanical properties and fatigue resistance. Cyclic adsorption–desorption of RGO-MS-3-1 was achieved through extrusion/ ethanol washing. After 10 cycles of reuse through extrusion, the adsorption capacity decreased from 52.90 to 50.02 g g−1, with a loss of 5.4%. The material was then washed with petroleum ether and ethanol in turn. Its adsorption capacity can restored to 98.8% of the initial value, showing a promising application prospect on heavy oil leakage treatment. The easily prepared RGO-MS exhibits excellent light absorption and photothermal oil adsorption properties, providing a good solution for the problem of heavy oil leakage at sea.