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91.
Yiguang Jiang Benxue Jiang Qihua Zhu Nan Jiang Pande Zhang Shuilin Chen Xu Hu Ge Zhang Jintai Fan Liangbi Su Jiang Li Long Zhang 《Journal of the European Ceramic Society》2018,38(5):2404-2409
Different deformation rates of Nd,Y-codoped CaF2 transparent ceramics were prepared by ceramization of single crystals. The deformation rate effects on the crystallization behaviors, microstructures, mechanical properties, and optical performances were investigated for the first time. The results indicate that the comprehensive performances of Nd,Y-codoped CaF2 ceramic (△a?=?62%) are the most optimal compared with other ceramics having different deformation rates (△a?=?34%, 40%, 50%, and 75%). In further investigations of the optical properties, the Nd,Y-codoped CaF2 ceramic (△a?=?62%) sample exhibited a high transparency (Ta?>?91%, 3-mm thick,250?~?1200?nm), low light scattering, superior fracture toughness (K1c?~?0.71?MPa·m1/2), strong fluorescence emission, long lifetime (τ?=?348.72?μs), and broad FWHM (29.2?nm), promising a good candidate for high-power laser material. 相似文献
92.
Tao Li Zehui Du Nobumichi Tamura Mao Ye Saikumar Inguva Wei Lu Xierong Zeng Shanming Ke Haitao Huang 《Journal of the European Ceramic Society》2018,38(4):1488-1497
(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this work, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25 °C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in x = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (TC), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient. 相似文献
93.
In this study, we present an effective strategy to enhance the energy storage properties of Ba0.4Sr0.6TiO3 (BST) lead-free ceramics by the addition of Bi2O3-B2O3-SiO2 (BBS) glass, which were prepared by the conventional solid state sintering method. The phase structure, microstructure and energy storage properties were investigated in detail. It can be found that the Ba0.4Sr0.6TiO3-x wt%(Bi2O3-B2O3-SiO2) (BST- x wt%BBS, 0 ≤ x ≤ 12) ceramics possess large maximum polarization (Pmax), low remanent polarization (Pr) and slim polarization electric field (P-E) hysteresis loops. The breakdown strength (BDS), recoverable energy storage density (Wrec) and energy storage efficiency (η) are enhanced obviously with the addition of BBS glass. The BST-9 wt%BBS ceramic is found to exhibit excellent energy storage properties with a Wrec of 1.98 J/cm3 and a η of 90.57% at 279 kV/cm. These results indicate that the BST-x wt%BBS ceramics might be good candidates for high energy storage applications. 相似文献
94.
95.
Chloride-induced corrosion of highway bridges constitutes a critical form of environmental deterioration and may result in significant escalation of seismic life-cycle costs due to increased fragility during earthquake events. Most of existing literature tends to adopt simplistic uniform area loss assumptions in lieu of potentially complex, yet realistic and more detrimental, pitting corrosion models for seismic vulnerability analysis. Since the degree of deterioration depends on the severity and duration of exposure, there exists a need to investigate the influence of uniform vs. pitting corrosion assumption on seismic life-cycle costs for varied chloride exposure conditions. A case-study example of a highway bridge in Central and Southeastern US reveals consideration of pitting corrosion as critical for extreme exposures compared to relatively minor settings. Subsequently this study provides recommendations to aid bridge engineers and stakeholders to balance between computational cost and accuracy of results to aid prompt decisions on rehabilitation of ageing bridges in different exposure conditions. A framework is also included to compute seismic life-cycle costs from generic measures of corrosion, independent of assumed exposure scenario. This framework is particularly helpful for seismic loss assessment of highway bridges in chloride exposure zones with periodic field measurements to estimate the extent of structural deterioration. 相似文献
96.
97.
ABSTRACTCrude extracts were extracted from blossoms of Citrus aurantium L. var. amara Engl. with 50% ethanol (CAVAP-E), 50% methanol (CAVAP-M), and hot water (CAVAP-W). CAVAP-W had the highest polyphenol yield of 3.7%. The optimum values of liquid/solid ratio, ultrasonic time, and ultrasonic power were 34.06 mL/g, 1 h, and 81.04 W, respectively. The adsorption characteristics of polyphenols were investigated using different macroporous resins. AB-8 and HP-20 resins offered higher adsorption and desorption capacities. Langmuir equation was more suitable to predict the adsorption of polyphenols. The pseudo second-order model was satisfactory to describe the kinetic data of polyphenols onto AB-8 and HP-20. 相似文献
98.
Enteroaggregative Escherichia coli (EAEC) is an emerging pathogen frequently associated with acute diarrhea in children and travelers to endemic regions. EAEC was found the most prevalent bacterial diarrheal pathogen from hospitalized Bolivian children less than five years of age with acute diarrhea from 2007 to 2010. Here, we further characterized the epidemiology of EAEC infection, virulence genes, and antimicrobial susceptibility of EAEC isolated from 414 diarrheal and 74 non-diarrheal cases. EAEC isolates were collected and subjected to a PCR-based virulence gene screening of seven virulence genes and a phenotypic resistance test to nine different antimicrobials. Our results showed that atypical EAEC (a-EAEC, AggR-negative) was significantly associated with diarrhea (OR, 1.62, 95% CI, 1.25 to 2.09, p < 0.001) in contrast to typical EAEC (t-EAEC, AggR-positive). EAEC infection was most prevalent among children between 7–12 months of age. The number of cases exhibited a biannual cycle with a major peak during the transition from warm to cold (April–June). Both typical and a-EAEC infections were graded as equally severe; however, t-EAEC harbored more virulence genes. aap, irp2 and pic were the most prevalent genes. Surprisingly, we detected 60% and 52.6% of multidrug resistance (MDR) EAEC among diarrheal and non-diarrheal cases. Resistance to ampicillin, sulfonamides, and tetracyclines was most common, being the corresponding antibiotics, the ones that are frequently used in Bolivia. Our work is the first study that provides comprehensive information on the high heterogenicity of virulence genes in t-EAEC and a- EAEC and the large prevalence of MDR EAEC in Bolivia. 相似文献
99.
100.
This paper deals with modeling of the phenomenon of fretting fatigue in
heterogeneous materials using the multi-scale computational homogenization technique
and finite element analysis (FEA). The heterogeneous material for the specimens consists
of a single hole model (25% void/cell, 16% void/cell and 10% void/cell) and a four-hole
model (25% void/cell). Using a representative volume element (RVE), we try to produce
the equivalent homogenized properties and work on a homogeneous specimen for the
study of fretting fatigue. Next, the fretting fatigue contact problem is performed for 3 new
cases of models that consist of a homogeneous and a heterogeneous part (single hole cell)
in the contact area. The aim is to analyze the normal and shear stresses of these models
and compare them with the results of the corresponding heterogeneous models based on
the Direct Numerical Simulation (DNS) method. Finally, by comparing the
computational time and % deviations, we draw conclusions about the reliability and
effectiveness of the proposed method. 相似文献