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1.
Oxidation kinetics of copper in the temperature range of 973–1173 K atP
O
2=21.27 kPa exhibit enhancement and deceleration in the rates with changing polarity compared to normal oxidation under interrupted mode of directcurrent application. These conditions are achieved by connecting the oxidizing copper covered with an initially formed thin oxide film to the positive and negative terminal of a dc source, respectively. However, the influence of direction of the current is found to be opposite under uninterrupted mode of impressed current flow in the same temperature range. The effect of short-circuiting the metal to the outer oxide/air interface on the reaction kinetics is also reported. The rate of oxide-scale growth under normal condition, and two different modes of current applications as well as with shorting circuitry attachment conform to the parabolic growth law. The results pertaining to the two different modes of impressed current have been discussed considering both the phenomena of electrolysis of the oxide electrolyte and the polarization at the two phase boundaries. The enhancement and the reduction in rates under uninterrupted impressed current conditions are explained on the basis of increased and decreased average defect concentrations, respectively, within the oxide layer. The acceleration and deceleration in the rates under interrupted mode of current flow have been explained in the light of sustenance of a steeper and flatter electrochemical-potential gradient of defects, respectively, across the growing-oxide layer. The possible different responses of the metal/oxide and oxide/air interfaces to the impressed current brought into play by two different modes of current application, have enabled to display a better insight on the mechanistic aspects of scale growth under the influence of an externally applied current. 相似文献
2.
Ananth Ranganathan 《Autonomous Robots》2012,32(4):351-368
A shared vocabulary between humans and robots for describing spatial concepts is essential for effective human robot interaction.
Towards this goal, we present a novel technique for place categorization from visual cues called PLISS (Place Labeling through
Image Sequence Segmentation). PLISS is different from existing place categorization systems in two major ways—it inherently
works on video and image streams rather than single images, and it can detect “unknown” place labels, i.e. place categories
that it does not know about. PLISS uses changepoint detection to temporally segment image sequences which are subsequently
labeled. Changepoint detection and labeling are performed inside a systematic probabilistic framework. Unknown place labels
are detected by using a probabilistic classifier and keeping track of its label uncertainty. We present experiments and comparisons
on the large and extensive VPC dataset. We also demonstrate results using models learned from images downloaded from Google’s
image search. 相似文献
3.
Praveen Siluvai Antony Rajiv Ananth Sohony Rajesh B. Biniwale 《International Journal of Hydrogen Energy》2014
A mathematical model has been developed to study the impact of nozzle-catalyst distance and bulk gas temperature on the conversion and hydrogen evolution rate in a spray pulse reactor. The effects of reactor configuration and operating parameters on conversion and evolution rate were predicted with more than 90% accuracy. Reactor optimization and sensitivity analysis were carried out and an optimal design of nozzle-catalyst distance 5 cm and bulk gas temperature of 50 °C were proposed. The optimized design was predicted to increase the conversion from approximately 32–74%. The model could be in general used for designing any endothermic heterogeneous catalytic reaction in a spray pulse reactor. 相似文献
4.
Kola Srinivas G. Sivakumar Ch. Ramesh Kumar M. Ananth Reddy K. Bhanuprakash V. Jayathirtha Rao Chih-Wei Chen Ying-Chan Hsu Jiann T. Lin 《Synthetic Metals》2011,161(15-16):1671-1681
We have synthesized and characterized donor–π–spacer–acceptor type molecules in which 1,3,4-oxadiazoles are π-spacers, triphenylamines are the donors and cyanoacetic acid are the acceptors for use as sensitizers in dye-sensitized solar cells (DSSCs). Detailed absorption, emission, electrochemical, photoelectrochemical and computational studies have been carried out on five novel derivatives. The dyes have an absorption range of 377–388 nm, and an emission in the range of 494–540 nm. There is a large charge transfer from the donor side to the acceptor side on excitation. The propeller shape of the triphenylamine and the bulky substituents on it help in reducing the dye-aggregation on TiO2 surface. The dyes exhibited good overall conversion efficiency (2.79–3.21%). Plane wave calculations indicate that the dye has a reasonably strong binding to the TiO2 surface and the generated DOS picture shows an overlap of the molecular orbitals of the dye and the TiO2 bands. We conclude that the dyes have a promising role as sensitizers in DSSC. 相似文献
5.
Nicoleta-Luminita Dumitrescu Madalina Icriverzi Anca Bonciu Paula Florian Antoniu Moldovan Anca Roseanu Laurentiu Rusen Valentina Dinca Florin Grama 《International journal of molecular sciences》2022,23(7)
Designing and obtaining new synthetic smart biointerfaces with specific and controlled characteristics relevant for applications in biomedical and bioengineering domains represents one of the main challenges in these fields. In this work, Matrix-Assisted Pulsed Laser Evaporation (MAPLE) is used to obtain synthetic biointerfaces of poly(N-isopropyl acrylamide-butyl acrylate) p(NIPAM-BA) copolymer with different characteristics (i.e., roughness, porosity, wettability), and their effect on normal HEK 293 T and murine melanoma B16-F1 cells is studied. For this, the influence of various solvents (chloroform, dimethylsulfoxide, water) and fluence variation (250–450 mJ/cm2) on the morphological, roughness, wettability, and physico–chemical characteristics of the coatings are evaluated by atomic force microscopy, scanning electron microscopy, contact angle measurements, Fourier-transform-IR spectroscopy, and X-ray photoelectron spectroscopy. Coatings obtained by the spin coating method are used for reference. No significant alteration in the chemistry of the surfaces is observed for the coatings obtained by both methods. All p(NIPAM-BA) coatings show hydrophilic character, with the exception of those obtained with chloroform at 250 mJ/cm2. The surface morphology is shown to depend on both solvent type and laser fluence and it ranges from smooth surfaces to rough and porous ones. Physico–chemical and biological analysis reveal that the MAPLE deposition method with fluences of 350–450 mJ/cm2 when using DMSO solvent is more appropriate for bioengineering applications due to the surface characteristics (i.e., pore presence) and to the good compatibility with normal cells and cytotoxicity against melanoma cells. 相似文献
6.
Diamond-like-carbon (DLC) coating of thickness 3 and 10 μm were developed with and without radical nitriding pretreatment on steel rollers and spur gear pair. The friction coefficient and wear amount were evaluated under sliding rolling contact condition in vacuum and under oil lubrication. Delamination of coatings was observed at the interface of the substrate. The wear resistance of coatings improved with the thickness of the coating. In vacuum both the roller and the gear pair of 10 μm coating thickness with radical nitriding showed identical wear behavior. The radical nitriding seemed to enhance the life of DLC coatings. 相似文献
7.
Polymerization shrinkage and porosity profile of dual cure dental resin cements with different adhesion to dentin mechanisms 下载免费PDF全文
Adrieli Burey Paulo José dos Reis Bruno Luiz Santana Vicentin Cássia Cilene Dezan Garbelini Márcio Grama Hoeppner Carlos Roberto Appoloni 《Microscopy research and technique》2018,81(1):88-96
This research aims to probe the porosity profile and polymerization shrinkage of two different dual cure resin cements with different dentin bonding systems. The self‐adhesive resin cement RelyX U200 (named RU) and the conventional Allcem Core (named AC) were analyzed by x‐ray microtomography (μCT) and Scanning Electron Microscopy (SEM). Each cement was divided into two groups (n = 5): dual‐cured (RUD and ACD) and self‐cured (RUC and ACC). μCT demonstrated that the method of polymerization does not influence the porosity profile but the polymerization shrinkage. Fewer concentration of pores was observed for the conventional resin cement (AC), independently the method used for curing the sample. In addition, SEM showed that AC has more uniform surface and smaller particle size. The method of polymerization influenced the polymerization shrinkage, since no contraction for both RUC and ACC was observed, in contrast with results from dual‐cured samples. For RUD and ACD the polymerization shrinkage was greater in the lower third of the sample and minor in the upper third. This mechanical behavior is attributed to the polymerization toward the light. µCT showed to be a reliable technique to probe porosity and contraction due to polymerization of dental cements. 相似文献
8.
Ananth Dodabalapur V. P. Kesan D. P. Neikirk B. G. Streetman M. H. Herman I. D. Ward 《Journal of Electronic Materials》1990,19(3):265-270
In this study, we describe the correlations between the photoluminescence (PL) spectra and electrical properties of pseudomorphic
modulation-doped AlGaAs/InGaAs/GaAs quantum wells (MDQWs) grown by molecular beam epitaxy. In MDQWs, the presence of a large
sheet carrier density contributes significantly to the PL linewidth. At low temperatures (4.2 K), free carrier induced broadening
of the PL linewidth is influenced by the material quality of the structure. At higher temperatures (77 K), differences in
the material quality do not affect the linewidth significantly, and under these conditions the PL linewidth is a good measure
of the sheet carrier density. The ratio of the 77 K to 4.2 K PL linewidths provides useful information about the crystalline
quality of the MDQW structures as illustrated by the correlation with 77 K Hall mobility data and a simple model. We present
results of Electron Beam Electroreflectance (EBER) to characterize MDQWs and undoped quantum wells in the AlGaAs/InGaAs/GaAs
material system. Several transitions have been observed and fitted to excitonic Lorentzian lineshapes, providing accurate
estimates of transition energy and broadening parameter at temperatures of 96 K and 300 K. 相似文献
9.
We report a sol–gel method to deposit a high-k dielectric, zirconium oxide (ZrO2). This solution-based approach has advantages of easy processing and low fabrication cost. Effects of annealing temperatures
on dielectric properties, such as tunneling current density and capacitance density, are reported. Morphological and chemical
characterizations suggest that the process temperature can be kept at or below 300°C. We have employed the solution-processed
ZrO2 dielectric in a zinc tin oxide thin-film transistor. Saturation mobility of 4.0 cm2/V s at operating voltage of 2 V has been observed. The measured subthreshold swing is 74 mV/decade, which is the result of
the combination of an electronically clean dielectric/semiconductor interface and high insulator capacitance. 相似文献
10.
In this study, we describe the effects of rapid thermal annealing on the electrical and optical properties of modulation-doped
quantum wells (MDQWs). The sheet carrier concentration in MDQW structures which have been annealed in contact with a piece
of GaAs tends to decrease with increasing annealing time due to Si auto-compensation in the doped AlGaAs regions. The high
energy cut-off point of 4.2 K PL spectra, which occurs at the Fermi energy, and the 77 K PL linewidth are accurate measures
of sheet carrier density. These two parameters track variations in carrier density produced by annealing. Photoluminescence
spectra also provide additional insight into annealing-induced changes such as Si migration, which causes a degradation in
the mobility of the two-dimensional electron gas. 相似文献