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11.
Ronald L. Holtz Peter S. Pao Robert A. Bayles Thomas M. Longazel Ramasis Goswami 《Metallurgical and Materials Transactions A》2012,43(8):2839-2849
The fatigue crack growth behavior of aluminum alloy 5083-H131 has been systematically studied as a function of degree of sensitization for aging at 448?K (175?°C). Fatigue crack growth rates were measured at load ratios of 0.1 and 0.85, in vacuum, air, and a corrosive aqueous environment containing 1?pct NaCl with dilute inhibitor. Sensitization does not affect the fatigue crack growth behavior of Al 5083-H131 significantly in vacuum or air, at low- or high-load ratio. For high-load ratio, in the 1?pct NaCl+inhibitor solution, the threshold drops by nearly 50?pct during the first 200?hours of aging, then it degrades more slowly for longer aging times up to 2000?hours. The change in aging behavior at approximately 200?hours seems to be correlated with the transition from partial coverage of the grain boundaries by ?? Al3Mg2 phase, to continuous full ?? coverage. ASTM G-67 mass loss levels below approximately 30?mg/cm2 do not exhibit degraded corrosion-fatigue properties for R?=?0.85, but degradation of the threshold is rapid for higher mass loss levels. 相似文献
12.
Dibakar Sen 《Computer aided design》2012,44(1):15-28
Digital human modeling (DHM) involves modeling of structure, form and functional capabilities of human users for ergonomics simulation. This paper presents application of geometric procedures for investigating the characteristics of human visual capabilities which are particularly important in the context mentioned above. Using the cone of unrestricted directions through the pupil on a tessellated head model as the geometric interpretation of the clinical field-of-view (FoV), the results obtained are experimentally validated. Estimating the pupil movement for a given gaze direction using Listing’s Law, FoVs are re-computed. Significant variation of the FoV is observed with the variation in gaze direction. A novel cube-grid representation, which integrated the unit-cube representation of directions and the enhanced slice representation has been introduced for fast and exact point classification for point visibility analysis for a given FoV. Computation of containment frequency of every grid-cell for a given set of FoVs enabled determination of percentile-based FoV contours for estimating the visual performance of a given population. This is a new concept which makes visibility analysis more meaningful from ergonomics point-of-view. The algorithms are fast enough to support interactive analysis of reasonably complex scenes on a typical desktop computer. 相似文献
13.
Ankita Bose Nandini Das Somendra N. Roy Nitesh Goswami Soumitra Kar R.C. Bindal P.K. Tewari 《International Journal of Hydrogen Energy》2014
An all silica DDR (deca dodecasil rhombohedral) zeolite membrane with dense, interlocked structure has been developed for separation of H2 from HI/I2 mixture of HI decomposition reaction. In this work, the DDR zeolite membrane was synthesized on the seeded clay-alumina substrate within 5 days. The seeds were synthesized by sonication mediated hydrothermal process within short crystallization time which enhanced the nucleation for the membrane growth. The synthesized membranes along with seed crystals were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy (EDAX). The selectivity of hydrogen with respect to CO2 and Ar was evaluated by single gas permeation studies at room temperature. The tests for corrosion resistance were carried out upto 120 h with both support and DDR membrane at 130 °C which confirmed the stability of membrane under the harsh HI/I2 environment. 相似文献
14.
SiO2–CaO–Na2O–P2O5–ZrO2 based bioactive glasses with different compositions of SiO2 and yttrium stabilized ZrO2 were prepared by the conventional melt quenching technique. The effects on the chemical–mechanical properties of bioactive glasses due to the addition of ZrO2 by replacing SiO2 were investigated. Microstructure and phase behavior were studied by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analysis. Compressive strength, porosity, Vickers hardness, and Young’s modulus were measured as mechanical properties. Bioactivity and cell viability were investigated by immersion in simulated body fluid and MTT assay analysis. Osteosarcoma cell proliferation on the specimen surfaces was examined by confocal laser scanning microscopy. The results showed that replacing SiO2 with ZrO2 helps the bioactive glass to be completely vitrified at comparatively lower sintering temperature than conventional Bioglass®. The mechanical properties were also improved without compromising biocompatibility. Bioactive glass containing 10 wt% ZrO2 and 35 wt% SiO2 showed compressive strength of 399.71 MPa, Young's modulus of 22.3 GPa, Vicker’s hardness of 502.54 HV, and porosity of 26 vol%. 相似文献
15.
Dibakar Sarkar Dr. Ipsita Chakraborty Marcello Condorelli Baijayanti Ghosh Thorben Mass Dr. Markus Weingarth Dr. Atin K Mandal Prof. Carmelo La Rosa Dr. Vivekanandan Subramanian Dr. Anirban Bhunia 《ChemMedChem》2020,15(3):293-301
The three GxxxG repeating motifs from the C-terminal region of β-amyloid (Aβ) peptide play a significant role in regulating the aggregation kinetics of the peptide. Mutation of these glycine residues to leucine greatly accelerates the fibrillation process but generates a varied toxicity profile. Using an array of biophysical techniques, we demonstrated the uniqueness of the composite glycine residues in these structural repeats. We used solvent relaxation NMR spectroscopy to investigate the role played by the surrounding water molecules in determining the corresponding aggregation pathway. Notably, the conformational changes induced by Gly33 and Gly37 mutations result in significantly decreased toxicity in a neuronal cell line. Our results indicate that G33xxxG37 is the primary motif responsible for Aβ neurotoxicity, hence providing a direct structure–function correlation. Targeting this motif, therefore, can be a promising strategy to prevent neuronal cell death associated with Alzheimer's and other related diseases, such as type II diabetes and Parkinson's. 相似文献
16.
Iron-Based Nanoparticles for Toxic Organic Degradation: Silica Platform and Green Synthesis 总被引:1,自引:0,他引:1
Meeks ND Smuleac V Stevens C Bhattacharyya D 《Industrial & engineering chemistry research》2012,51(28):9581-9590
Iron and iron oxide nanoparticles (NPs) are finding wide applications for the remediation of various toxic chloro-organic compounds (such as trichloroethylene, TCE), via reductive and oxidative processes. In this study, Fe NPs (30-50 nm) are synthesized by reduction from ferric ions immobilized (by ion exchange) on a platform (two types of sulfonated silica particles), in order to prevent the NP agglomeration. Next, the Fe NPs are oxidized and their effectiveness for the oxidative dechlorination of TCE via the heterogeneous decomposition of hydrogen peroxide to OH? on the surface of the iron oxide NPs was demonstrated. For the reductive approach, the use of ascorbic acid as a "green" reducing agent in conjunction with a secondary metal (Pd) inhibits NP oxidation and agglomeration through surface adsorbed species. The Fe/Pd NPs have been successfully applied for the dechlorination of TCE (k(SA), surface-area normalized reaction rate, = 8.1 ×10(-4) L/m(2)h). 相似文献
17.
18.
Rakesh Kumar A. Arvind M. Goswami S. Bhattacharya V. K. Shrikhande G. P. Kothiyal 《Journal of Materials Science》2009,44(13):3349-3355
We have prepared lithium zinc silicate (LZS) glasses of compositions (mol%) 17.83Li2O–17.73ZnO–(53.52 − x)SiO2–5.25Na2O–1.25P2O5–4.31B2O3–x-NiO, where 0.5 ≤ x ≤ 2.0, by the melt quench technique. The effect of NiO on the phase formation, thermo-physical properties and sealing behaviour
of LZS glass–ceramics was studied using X-Ray diffraction (XRD), thermo-mechanical analysis (TMA) and microhardness (MH) measurements.
It is found that NiO incorporation leads to a change in the role of ZnO from network modifier to intermediate oxide. The intermediate
network forming Zn2+ ions would find it more difficult to diffuse and initiate the transformation of Li3Zn0.5SiO4 to Li2ZnSiO4. Thus Li3Zn0.5SiO4 is formed instead of Li2ZnSiO4 on addition of 2 mol% NiO. Scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) measurements
at the glass–ceramic-to-metal interface reveal a change in the microstructure commensurate with the changing role of ZnO.
Addition of NiO favoured interdiffusion of species at the interface leading to better sealing. 相似文献
19.
The dielectric properties of vacuum-deposited dysprosium oxide films have been studied in the audio-frequency range (102–104 Hz) at various temperatures (78–373 K). The dielectric constant (6.7) was independent of film thickness for thicker films (d > 1000 Å). The capacitance was dependent both on temperature and frequency, but became constant for all frequencies at low temperature. Tan δ showed a frequency minimum and its variation with frequency and temperature was in agreement with the model proposed earlier by Goswami and Goswami. The breakdown field (≌106 V cm-1) followed the Forlani-Minnaja relation. The activation energy and the refractive index of these films were also measured. 相似文献
20.
Among the various possible ways of dealing with notch and crack situations, the scaled boundary finite element method [SBFEM,
(Wolf and Song in Finite element modelling of unbounded structures. Wiley, Chichester, 1996; Wolf in The scaled boundary finite element method. Wiley, Chichester, 2003)] has been adopted in this work. This method has been proved to be versatile, much less time consuming than the finite element
method and generates highly accurate numerical predictions in cases of structures with notches and cracks. The SBFEM gives
the advantage of boundary element method by reducing one dimension in modelling the structures but the mathematical formulations
are more related to conventional displacement based finite element method. This method requires a certain scalability of the
given structure with respect to a point called similarity center. Like in the case of the boundary element method, the structure
needs to be discretized only at the surface where standard displacement based isoparametric finite element formulations are
adequate. Unlike in the boundary element method, however, no fundamental solution is required by the scaled boundary finite
element method. The similarity or scalability of the method requires separation of coordinates such that in the radial direction
(i.e. scaling direction) it yields simple differential equations that can be solved analytically. So this approach can be
considered as a semi-analytical method. Several two-dimensional examples have been analysed for crack and notch situations
that are well known cases in fracture mechanics. A number of three-dimensional cases have been considered for different crack
configurations that yield high order of singularity. The results, according to the authors’ knowledge are up to now unpublished
in the open literature. Parametric studies are conducted for structures with bi-material interfaces. 相似文献