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71.
Raghu V. Prakash 《Transactions of the Indian Institute of Metals》2010,63(2-3):173-179
Damage identification due to fatigue has been studied on 304-Stainless Steel and Al-Cu-Mg alloys 2014-T651 and 7175-T7351, using two different experimental methods: a) cyclic indentation, and b) infrared thermography. Indentation response during load controlled cyclic loading is used to characterize fatigue response of materials. The load vs. depth of penetration data obtained continuously during fatigue testing is used to obtain information on cyclic stress-strain behavior and onset of failure. Infrared thermography is used to study the heat generation during fatigue loading on specimens. The variables that affect the process are: frequency of loading, magnitude of strain (elastic-plastic), thermal properties. The temperature curve can be considered to be having three regions, initial region of rapid increase in temperature, followed by stable temperature rise and final rapid heat generation prior to failure. The slopes in the initial region and stable region are independent of prior damage history in materials in case of specimens subjected to pure elastic load reversals. In case of elastic-plastic loadings, the rate at which the temperature rises in initial region changes as a function of fatigue damage and can thus be used to estimate prior damage in materials. 相似文献
72.
We develop theorems that place limits on the point-wise approximation of the responses of filters, both linear shift invariant (LSI) and linear shift variant (LSV), to input signals and images that are LSV in the following sense: they can be expressed as the outputs of systems with LSV impulse responses, where the shift variance is with respect to the filter scale of a single-prototype fillter. The approximations take the form of LSI approximations to the responses. We develop tight bounds on the approximation errors expressed in terms of filter durations and derivative (Sobolev) norms. Finally, we find application of the developed theory to defoveation of images, deblurring of shift-variant blurs, and shift-variant edge detection. 相似文献
73.
Curcumin (diferuloyl methane) from rhizomes of Curcuma longa L. binds to phosphatidylcholine (PC) micelles. The binding of curcumin with PC micelles was followed by fluorescence measurements.
Curcumin emits at 490 nm with an excitation wavelength of 451 nm after binding to PC-mixed micelles stabilized with deoxycholate.
Curcumin in aqueous solution does not inhibit dioxygenation of fatty acids by Lipoxygenase 1 (LOX1). But, when bound to PC
micelles, it inhibits the oxidation of fatty acids. The present study has shown that 8.6 μM of curcumin bound to the PC micelles
is required for 50% inhibition of linoleic acid peroxidation. Lineweaver-Burk plot analysis has indicated that curcumin is
a competitive inhibitor of LOX1 with K
l
of 1.7 μM for linoleic and 4.3 μM for arachidonic acids, respectively. Based on spectroscopic measurements, we conclude that
the inhibition of LOX1 activity by curcumin can be due to binding to active center iron and curcumin after binding to the
PC micelles acts as an inhibitor of LOX1. 相似文献
74.
Two aluminium alloys with nominal compositions of Al-8Fe-4Ce and Al-8Fe-1V-2Si (all compositions in wt%) were rapidly solidified by ultrasonic gas atomization. The atomized powders with an average particle size (d50) of 30 m were vacuum hot pressed and subsequently hot extruded. The P/M extrusion exhibited similar microstructure and elevated temperature tensile properties. The tensile and stress rupture samples of both the alloys exhibited ductile dimple failure. However, the Al-Fe-V-Si extrusion samples exhibited significantly better creep and stress rupture properties. The Al-Fe-Ce alloy was found to be more susceptible to cavitation at elevated temperatures which resulted in poor stress rupture properties. 相似文献
75.
Nigerloxin [2-amido-3-hydroxy-6-methoxy-5-methyl-4-(prop-1′-enyl) benzoic acid], a fungal metabolite, is an inhibitor of lipoxygenase
and aldose reductase with free radical-scavenging properties. The interaction of nigerloxin with bovine serum albumin (BSA)
was investigated using fluorescence spectroscopy and circular dichroic measurements. The fluorescence of BSA was quenched
following interaction with nigerloxin, and this property was used to generate a binding constant. The estimated association
constant was 1.01±0.2×106 M−1. Job's method of continuous variation indicated that nigerloxin formed a 1∶1±0.1 complex with BSA. To understand the nature
of the interaction, the variance in the association constant as a function of temperature in the range of 14–45°C was used
to calculate the thermodynamic parameters. The thermodynamic parameters at 27°C derived from the mass action plot and van't
Hoff's plot were as follows: ΔG=−8.2±0.1 kcal/mol, ΔH≈0 kcal/mol, and ΔS=27.5±0.4 cal/mol/K (where ΔG is free energy, ΔH is enthalpy, and ΔS is entropy). Increasing ionic strength did not favor interaction. Circular dichroic measurements revealed that the interaction
of nigerloxin with BSA did not lead to changes in the secondary structure of the protein. The reversibility of the interaction
verified by the dilution method was found to be reversible. These measurements suggest that partial hydrophobic and partial
ionic bonding play a role in the interaction of nigerloxin with BSA. 相似文献
76.
77.
Characterization of mechanical properties and three‐body abrasive wear of functionally graded aluminum LM25/titanium carbide metal matrix composite 下载免费PDF全文
Several engineering components require location specific performance under operating conditions. A compositional/microstructural gradient can provide the performance required at specific locations and these materials were named as functionally graded materials. Functionally graded aluminium metal matrix composites were generally established for the tribo‐components where high wear resistance was a necessity. Reports on three body abrasive wear behaviour of functionally graded materials was limited to date. In the present work, a new functionally graded system comprising aluminium/titanium carbide (10 wt%) was produced through stir casting route followed by centrifugal casting technique and its three body abrasive wear behaviour was investigated. Hollow cylindrical part with the dimensions of length 150 mm, outer diameter 150 mm and thickness 16 mm was obtained. Microstructural study was performed on outer (1 mm) and inner surface (13 mm) to analyze the compositional gradient across the thickness of the functionally graded composite. Hardness was measured on different surfaces along the radial distance from outer periphery and tensile test was conducted on the outer and inner zone. Abrasive wear test was conducted on different surfaces of the functionally graded composite under various loads and speeds at constant time. The microstructural results revealed that particle segregation was more at the outer surface and less at the inner surface. Wear test results showed that increase in wear rate was obtained with increase of load and decrease in wear rate was obtained with increase of speed. The outer surfaces of the functionally graded composite had greater mechanical properties and better wear resistance compared to other surfaces. Scanning electron microscopy analysis was done on the abraded surfaces and observed wear mechanisms were interpreted. 相似文献
78.
Firdaus Janoos Boonthanome Nouanesengsy Raghu Machiraju Han Wei Shen Steffen Sammet Michael Knopp István Á. Mórocz 《Computer Graphics Forum》2009,28(3):903-910
Classically, analysis of the time-varying data acquired during fMRI experiments is done using static activation maps obtained by testing voxels for the presence of significant activity using statistical methods. The models used in these analysis methods have a number of parameters, which profoundly impact the detection of active brain areas. Also, it is hard to study the temporal dependencies and cascading effects of brain activation from these static maps. In this paper, we propose a methodology to visually analyze the time dimension of brain function with a minimum amount of processing, allowing neurologists to verify the correctness of the analysis results, and develop a better understanding of temporal characteristics of the functional behaviour. The system allows studying time-series data through specific volumes-of-interest in the brain-cortex, the selection of which is guided by a hierarchical clustering algorithm performed in the wavelet domain. We also demonstrate the utility of this tool by presenting results on a real data-set. 相似文献
79.
80.
Narendar Nasani Srinivas R. Gavinola Vanessa Graca Amarnath R. Allu Raghu C. Reddy Bharat B. Kale 《Journal of the American Ceramic Society》2021,104(11):5689-5697
The ABO3 type perovskite oxide-based ceramic membranes are one of the most important classes of materials for high-temperature solid oxide fuel cell applications. The acceptor-doped calcium titanate (CaTiO3) perovskite has attracted considerable attention as an oxide ion-conducting membrane due to its potentially high ionic conductivity and excellent stability. Nonetheless, the ionic conductivity of the material must still be improved. Following the strategy of the substitution of dopants on the B-site, the current work is focused on exploring the effect of Al and Ni additions on electrical properties, by studying the nominal compositions CaTi0.7Al0.3–xNixO3−δ (x = 0, 0.1, 0.2 and 0.3). The materials were synthesized by the sol–gel method and studied as a function of phase composition, microstructure, and electrical properties. The results demonstrate an increase of both total and specific grain boundary conductivity with increasing Ni content, while predominant p-type behavior is shown under oxygen-rich atmosphere. 相似文献