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81.
Kanaparthi Ramesh Yi Ling Eileen Goh C. G. Gwie Chang Jie Timothy John White Armando Borgna 《Journal of Porous Materials》2012,19(4):423-431
Nanocrystalline LaPxOy with various starting P to La ratios from 0.5 to 2.0 catalysts were prepared by a sol?Cgel method using cetyl trimethylammonium bromide (CTAB) as template. The catalysts were thoroughly characterized by N2 physisorption, powder X-ray diffraction (XRD), temperature programmed desorption (TPD) of NH3, solid state 31P and 1H nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM) techniques. XRD results indicate the presence of predominantly monazite LaPO4 with minor amounts of (??3.0 wt%) rhabdophane LaPO4 phase in the samples with starting P/La ratios of 1.0 and 1.5. NH3-TPD results show an increasing trend in the total acidity with increase in P/La ratio. These catalysts were tested in the selective ethanol dehydration in the temperature range between 250 and 400?°C. The catalyst activity (??mol/h/m2) is increased with P/La ratio and the catalyst with highest P/La ratio of 2.0 exhibiting the highest ethanol dehydration activity. The ethanol conversion increased with reaction temperature, reaching 100% at 350?°C and remains unchanged at higher temperatures. On the other hand, the ethylene selectivity is also increased up to 350?°C and then decreased with further increase of reaction temperature. At a P/La ratio of 2, the CTAB templated LaPxOy catalyst showed higher catalytic activities compared to the LaPxOy by hydrothermal method without any template. 相似文献
82.
Abstract Error-diffused quantization has been applied to the generation of cell-oriented computer-generated Fourier transform holograms, resulting in reduced reconstruction errors. Improvements are demonstrated when applied to the algorithms of Lohmann, Lee and Burckhardt after invoking realistic constraints on the minimum size of the printable spot for an electrophotographic laser printer. 相似文献
83.
Raqibul Mostafa Ramesh C. Pallat Uwe Ringel Ashok A. Tikku Jeffrey H. Reed 《ETRI Journal》2012,34(3):319-329
Closed‐loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal‐to‐noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two‐element array. It is shown that for a two‐element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter‐element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors. 相似文献
84.
Hot Corrosion Behaviour of Refractory and Rare Earth Oxide Reinforced CoCrAlY APS Coatings at 700 °C
H. S. Nithin V. Desai M. R. Ramesh 《Transactions of the Indian Institute of Metals》2018,71(10):2403-2413
This paper investigates cyclic hot corrosion of plasma sprayed CoCrAlY?+?Al2O3?+?YSZ (C1) and CoCrAlY?+?CeO2 (C2) composite coatings on MDN 321 and Superni 76 substrates in molten salt (Na2SO4-60%V2O5) environment exposed to 700 °C. Weight change technique is used to evaluate the corrosion performance. Both C1 and C2 coatings showed better corrosion resistance than uncoated alloy. Both the coatings showed linear weight gain during the initial cycles and parabolic weight gain nature with subsequent hot corrosion cycles. The parabolic rate constant (Kp) of C1 and C2 coating was observed to be in the range 0.29–0.32?×?10?10 g2 cm?4 s?1 and 1.0–1.13?×?10?10 g2 cm?4 s?1 respectively. In C1 coating, the globular and continuously packed structure on the corroded surface having CoO, Cr2O3, CoCr2O4 and CoAl2O4 spinel oxides provided superior hot corrosion resistance. While in case of C2 coating, the outward growth of CeVO4 irregular crystals as a corrosion product of CeO2 and V2O5 salt deteriorated the oxide scales resulting in higher corrosion rate. 相似文献
85.
Ramesh Subbaraman 《Journal of Network and Systems Management》2018,26(3):547-572
Traditionally Internet Service Providers (ISPs) have used a centralized traffic filtering architecture, wherein unwanted traffic heading towards a customer who subscribes to their filtering service is diverted to a security data center (SDC); from where only traffic deemed wanted is re-routed back to the customer using an overlay network of tunnels. Given the huge volumes of traffic that are being seen today, this centralized architecture’s scalability is already being stretched from a network capacity point of view. Moreover, the traffic diversion mechanism used necessitates configuring and maintaining tunnels, which is a network management overhead. We argue that this centralized architecture and tunnel necessitating traffic diversion mechanism will not scale as we move further along into the era where ISPs are becoming or providing connectivity to cloud providers. We propose a distributed architecture with multiple SDCs that scales from a capacity perspective, and describe how a standardized router capability, Border Gateway Protocol—Flow Specifications, can be used to selectively propagate traffic diversion routes which eliminates the need for tunnels. Furthermore, we show how the assigning of arriving traffic to specific SDCs can be modeled and solved as a mathematical optimization problem, which enables automated instantiation of the filtering service and also helps quantify the benefits of the distributed architecture from a capacity utilization perspective. 相似文献
86.
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
87.
This paper reported on the work performed to study the formation of silicon nitride and silicon carbide whiskers using the carbothermal nitridation process. A distinctive aspect of the present study lies in the use of the mechanical milling method to alter the regularity of the crystalline network of the silica sand. In order to optimise the processing parameters for the synthesis of silicon carbide, the concept of Taguchi's Design of Experiments was considered, the analysis being based on Taguchi's signal to noise ratio and variance techniques to obtain optimum combination of process parameters. Important factors influencing the formation of silicon carbide were the duration of the mechanical milling, followed by temperature, time and heating rate. 相似文献
88.
Influence of Microstructure and Surface Activation of Dual‐Phase Membrane Ce0.8Gd0.2O2−δ–FeCo2O4 on Oxygen Permeation 下载免费PDF全文
Madhumidha Ramasamy Stefan Baumann Justinas Palisaitis Falk Schulze‐Küppers Maria Balaguer Daejin Kim Wilhelm A. Meulenberg Jochim Mayer Ramesh Bhave Olivier Guillon Martin Bram 《Journal of the American Ceramic Society》2016,99(1):349-355
Dual‐phase oxygen transport membranes are fast‐growing research interest for application in oxyfuel combustion process. One such potential candidate is CGO‐FCO (60 wt% Ce0.8Gd0.2O2?δ–40 wt% FeCo2O4) identified to provide good oxygen permeation flux with substantial stability in harsh atmosphere. Dense CGO‐FCO membranes of 1 mm thickness were fabricated by sintering dry pellets pressed from powders synthesized by one‐pot method (modified Pechini process) at 1200°C for 10 h. Microstructure analysis indicates presence of a third orthorhombic perovskite phase in the sintered composite. It was also identified that the spinel phase tends to form an oxygen deficient phase at the grain boundary of spinel and CGO phases. Surface exchange limitation of the membranes was overcome by La0.6Sr0.4Co0.2Fe0.8O3?δ (LSCF) porous layer coating over the composite. The oxygen permeation flux of the CGO‐FCO screen printed with a porous layer of 10 μm thick LSCF is 0.11 mL/cm2 per minute at 850°C with argon as sweep and air as feed gas at the rates of 50 and 250 mL/min. 相似文献
89.
B. Rajesh Babu M. S. R. Prasad K. V. Ramesh Y. Purushotham 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(3):589-597
The effect of Al substitution on electrical and dielectric parameters of Ni–Zn ferrite has been discussed in the present work. The phase identification, surface morphology was studied using X-ray diffractometer (XRD), scanning electron microscope (SEM), respectively. The XRD patterns confirm the single-phase formation of these ferrites. With Al3+, substitution lattice parameter decreases due to smaller Al3+ ions replacing Fe3+ ions. The average grain size obtained from SEM results are in the range of 390–27 nm. The DC resistivity was observed to increase with increasing Al3+ ions concentration due to the unavailability of Fe3+ ions. Dielectric constant (\(\upvarepsilon ^{\prime }\)) and dielectric loss tangent (tan δ) have been studied as a function of frequency (1 kHz–10 MHz) and temperature (50–300 °C). The observed results are explained on the basis of interfacial polarization as predicted by Maxwell and Wagner. 相似文献
90.
Sh.?Ammar K.?RameshEmail author B.?Vengadaesvaran S.?Ramesh A.?K.?Arof 《Journal of Coatings Technology and Research》2016,13(5):921-930
In this study, ZnO nanoparticles ranging from 1 to 8% (w/w) were introduced into a hybrid acrylic-silicone polymeric matrix to achieve nanocomposite coating systems with remarkable anti-corrosion and hydrophobic characteristics. The chemical structure of the developed hybrid polymeric matrix was investigated using Fourier transform infrared spectroscopy, whereas the morphology and wettability of the developed surfaces were determined using field emission scanning electron microscopy and contact angle measurements (CA), respectively. Furthermore, the anti-corrosion performance and the barrier properties over 60 days of exposure to a 3.5% NaCl solution were studied by electrochemical impedance spectroscopy. All the obtained results revealed that the presence of ZnO nanoparticles significantly influences the performance of the acrylic-silicone polymeric matrix. A coating system with 3% wt ZnO nanoparticles demonstrated the most pronounced anti-corrosion properties and also achieved the highest CA, with a value of 95.6°. 相似文献