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排序方式: 共有207条查询结果,搜索用时 31 毫秒
11.
Tushar Borkar John Sosa Jun Yeon Hwang Thomas W. Scharf Jaimie Tiley Hamish Fraser Rajarshi Banerjee 《JOM Journal of the Minerals, Metals and Materials Society》2014,66(6):935-942
A new class of Ni-Ti-C-based metal-matrix composites has been developed using the laser-engineered net shaping? process. These composites consist of an in situ formed and homogeneously distributed titanium carbide (TiC) phase reinforcing the nickel matrix. Additionally, by tailoring the Ti/C ratio in these composites, an additional graphitic phase can also be engineered into the microstructure. Serial-sectioning, followed by three-dimensional reconstruction of the microstructure in these composites, reveals homogeneously distributed primary and eutectic titanium carbide precipitates as well as a graphitic phase encompassing the primary carbides within the nickel matrix. The morphology and spatial distribution of these phases in three dimensions reveals that the eutectic carbides form a network linked by primary carbides or graphitic nodules at the nodes, which suggests interesting insights into the sequence of phase evolution. These three-phase Ni-TiC-C composites exhibit excellent tribological properties, in terms of an extremely low coefficient of friction while maintaining a relatively high hardness. 相似文献
12.
Suresh Bhalla Praveen Kumar Ashok Gupta Tushar K. Datta 《Canadian Metallurgical Quarterly》2009,22(4):373-382
The electromechanical impedance technique employs surface-bonded lead zirconate titanate piezoelectric ceramic patches as impedance transducers for structural health monitoring and nondestructive evaluation. The patches are bonded to the monitored structures using finitely thick adhesive bond layer, which introduces shear lag effect, thus invariably influencing the electromechanical admittance signatures. This paper presents a new simplified impedance model to incorporate shear lag effect into electromechanical admittance formulations, both one-dimensional and two-dimensional. This provides a closed-form analytical solution of the inverse problem, i.e. to derive the true structural impedance from the measured conductance and susceptance signatures, thus an improvement over the existing models. The influence of various parameters (associated with the bond layer) on admittance signatures is investigated using the proposed model and the results compared with existing models. The results show that the new model, which is far simpler than the existing models, models the shear lag phenomenon reasonably well besides providing direct solution of a complex inverse problem. 相似文献
13.
Tushar S. Basu Baul Pradip Das George Eng Anthony Linden 《Journal of Inorganic and Organometallic Polymers and Materials》2010,20(1):134-141
Four new triphenyltin(IV) complexes containing [((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]acetate ligands (L) have been synthesized with formulations of Ph3SnLH. They have been studied by multinuclear (1H, 13C, 119Sn) NMR, 119Sn M?ssbauer and IR spectroscopy. A full characterization of one complex, Ph3SnL1H (1), was accomplished by single crystal X-ray crystallography, which revealed the compound to be a macrocyclic tetramer. In
the tetramer, the five coordinate tin atoms have distorted trigonal bipyramidal geometries with the three phenyl groups occupying
equatorial positions, while an oxygen atom of the carboxylate group of one L ligand and the oxide O-atom (formerly the hydroxy
group) of a second L ligand in an apical positions. The carboxylate ligands bridge adjacent tin atoms and coordinate in the
zwitterionic form with the phenolic proton moved to the nearby nitrogen atom. 119Sn NMR results indicate that the tetrameric structures of the complexes in the solid state, in which the tin atoms are five-coordinated,
dissociate in solution to yield four coordinate monomeric species. 相似文献
14.
Removal of gaseous and vapor constituents of environmental tobacco smoke (ETS) by activated carbons in a packed bed arrangement was studied under dynamic conditions and was compared with that by silica gel and molecular sieve 13X. ETS is a mixture of sidestream smoke and exhaled mainstream smoke, and it consists of various organic and inorganic compounds, trace heavy metals, and particulate matters. Due to the complex nature of ETS-air mixture, its removal from indoors is a challenging task. For experimentation in a laboratory, the ETS was produced from a specially designed smoking apparatus that simulated the puffng of a cigarette by a person. Air containing ETS was passed through a bed containing about 25 grams of activated carbon at room temperature. The flow rate of air-ETS mixture through the bed was 4000 cm3/min. The relative humidity of the air was 50% and contained about 35 to 40 ppm of hydrocarbons as measured as methane-equivalent. The number of particles in the inlet air stream were in the range of 30,000 to 35,000 particles/cm3. About 60% of hydrocarbons present in ETS were removed at these operating conditions for a period of about 70 hours. Based on 15 adsorption and regeneration cycles, it was noted that the carbon bed did not loose its capacity for ETS significantly as indicated by the BET surface area and water adsorption data. At the beginning of an adsorption cycle, the carbon bed captured a significant number of particles. However, the bed rapidly lost its particle capture effciency as the experiment progressed. The number of particles in the outlet air stream was found to be the same as that of the inlet stream within five minutes. 相似文献
15.
16.
Effect of scale on the drop size distribution in a pump-mix mixer has been studied. A network of zones model was developed to predict the drop size distribution at different locations in the mixer. Computational fluid dynamics model was used to obtain the flow patterns in the mixer and to identify zones based on the flow patterns. Population balance equation was solved for all the zones of the mixer. The model was validated with the experimental data over a wide range of parameters as well experimental data from the published literature. The model was further extended for scale-up studies. Two different scale-up criteria were studied. It was observed that equal power consumption per unit mass and geometrical similarity is a better scale-up criterion as compared with equal tip speed criterion for pump-mix mixers. 相似文献
17.
Comparing error estimation measures for polynomial and kriging approximation of noise-free functions 总被引:1,自引:0,他引:1
Tushar Goel Raphael T. Hafkta Wei Shyy 《Structural and Multidisciplinary Optimization》2009,38(5):429-442
Error estimation measures are useful for assessing uncertainty in surrogate predictions. We use a suite of test problems to
appraise several error estimation measures for polynomial response surfaces and kriging. In addition, we study the performance
of cross-validation error measures that can be used with any surrogate. We use 1,000 experimental designs to obtain the variability
of error estimates with respect to the experimental designs for each problem. We find that the (actual) errors for polynomial
response surfaces are less sensitive to the choice of experimental designs than the kriging errors. This is attributed to
the variability in the maximum likelihood estimates of the kriging parameters. We find that no single error measure outperforms
other measures on all the problems. Computationally expensive integrated local error measures (standard error for polynomials
and mean square error for kriging) estimate the actual root mean square error very well. The distribution-free cross-validation
error characterized the actual errors reasonably well. While the estimated root mean square error for polynomial response
surface is a good estimate of the actual errors, the process variance for kriging is not. We explore a few methods of simultaneously
using multiple error measures and demonstrate that the geometric means of several combinations of error measures improve the
assessment of the actual errors over individual error measures. 相似文献
18.
Ensemble of surrogates 总被引:5,自引:3,他引:2
Tushar Goel Raphael T. Haftka Wei Shyy Nestor V. Queipo 《Structural and Multidisciplinary Optimization》2007,33(3):199-216
The custom in surrogate-based modeling of complex engineering problems is to fit one or more surrogate models and select the
one surrogate model that performs best. In this paper, we extend the utility of an ensemble of surrogates to (1) identify
regions of possible high errors at locations where predictions of surrogates widely differ, and (2) provide a more robust
approximation approach. We explore the possibility of using the best surrogate or a weighted average surrogate model instead
of individual surrogate models. The weights associated with each surrogate model are determined based on the errors in surrogates.
We demonstrate the advantages of an ensemble of surrogates using analytical problems and one engineering problem. We show
that for a single problem the choice of test surrogate can depend on the design of experiments. 相似文献
19.
Eosin-G and ethyl eosin dye sensitized CdS nanowires towards dye sensitized solar cells applications
Bhoomi Khodiyar Avinash C. Mendhe Tushar B. Deshmukh Babasaheb R. Sankapal 《加拿大化工杂志》2024,102(5):1863-1872
One dimensional (1-D) CdS nanowires have been grown through a low temperature chemical route and have been sensitized with eosin-G and ethyl eosin dyes to broaden the absorption spectrum of CdS and to enhance the photoelectrochemical (PEC) performance under illumination. The used method is advantageous due to its simplicity, low cost, scalability, and controllability. Interestingly, eosin-G and ethyl eosin dyes yield nearly four- and six-fold increase in device efficiency compared to bare CdS when tested in dye-sensitized solar cell assembly. Structural, surface morphological, optical, and surface wettability studies have been formulated for CdS, whereas identification of materials along with PEC investigations were conducted through current density–voltage (J-V), external quantum efficiency (EQE), characteristics under the illumination of 94.6 mW/cm2 (AM 1.5G), and electrochemical impedance spectroscopy (EIS). 相似文献
20.
Tushar S. Basu Baul Cheerfulman Masharing Giuseppe Ruisi Claudio Pettinari Anthony Linden 《Journal of Inorganic and Organometallic Polymers and Materials》2009,19(3):395-400
Two new polymeric triorganotin(IV) complexes R3Sn{O2CC6H4[N=C(H)}{C(CH3)CH(CH3)-3-OH]-p} n ([Me3Sn(LH)] n : 1) and ([Ph3Sn(LH)] n : 2) containing a 4-[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)amino]benzoate (LH) framework were prepared. Both compounds have been characterized by 1H, 13C, 119Sn NMR, IR and 119Sn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of complexes 1 and 2 reveal that they exist as polymeric zig-zag chains in which the LH-bridged Sn-atoms adopt a trans-R3SnO2 trigonal bipyramidal configuration with R groups in the equatorial positions and the axial sites occupied by an oxygen atom from the carboxylate ligand and the alcoholic oxygen atom of the next carboxylate ligand in the chain. The carboxylate ligands coordinate in the zwitterionic form with the alcoholic proton moved to the nearby nitrogen atom. 相似文献