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991.
The crystallization behaviour and the mechanical properties of rapidly solidified Al87.5Ni7Mm5Fe0.5 alloy ribbons have been examined in both as-melt-spun and heat-treated condition using differential scanning calorimetry,
X-ray diffractometry (XRD), transmission electron microscopy (TEM), tensile testing and Vicker’s microhardness machine. XRD
and TEM studies revealed that the as-melt-spun ribbons are fully amorphous. The amorphous ribbon undergoes three-stage crystallization
process upon heating. Primary crystallization resulted in the formation of fine nanocrystalline fcc-Al particles embedded
in the amorphous matrix. The second and third crystallization stages correspond to the precipitation of Al11(La,Ce)3 and Al3Ni phases, respectively. Microhardness and tensile strength of the ribbons were examined with the variation of temperature
and subsequently correlated with the evolved structure. Initially, the microhardness of the ribbon increases with temperature
followed by a sharp drop in hardness owing to the decomposition of amorphous matrix that leads to formation of intermetallic
compounds 相似文献
992.
A circularly polarized stacked patch microstrip antenna and a 2?×?2 subarray for circular polarization are proposed in this paper. The proposed design has the input impedance bandwidth and axial ratio bandwidth of about 10% and 4.7% respectively. Circular polarization is obtained with the help of slits cut in the patch. A size reduction of around 37% is also achieved with the help of the slits. A subarray based on sequentially rotated feeding technique for circular polarization is also presented in this paper. Array element was deigned using a high dielectric constant laminate for feed network. In addition to low boresight axial-ratio, the subarray has impedance and 3-dB axial-ratio bandwidths of 12% and 8% respectively. 相似文献
993.
The indium doped silver oxide thin films have been prepared at 275 °C on soda lime glass and silicon substrates by reactive
electron beam evaporation technique; the deposition rate has been varied (by varying the electron beam current) in the range
0.94–16.88 nm/s keeping the oxygen flow rate constant. These films are polycrystalline. The electrical resistivity for these
films decreases with increasing deposition rate. The AIO films prepared with a deposition rate of 5.7 nm/s show near p-type
conductivity. The work function has been measured on these films by contact potential method using Kelvin Probe. The surface
morphology of the films has been evaluated using atomic force microscopy (AFM). The roles of indium doping and oxygen vacancies
in the electrical properties of these films have been analyzed; the ionized impurity scattering is the dominant mechanism
controlling the electrical conduction in these films. 相似文献
994.
Text extraction and document image segmentation using matched wavelets and MRF model. 总被引:1,自引:0,他引:1
Sunil Kumar Rajat Gupta Nitin Khanna Santanu Chaudhury Shiv Dutt Joshi 《IEEE transactions on image processing》2007,16(8):2117-2128
In this paper, we have proposed a novel scheme for the extraction of textual areas of an image using globally matched wavelet filters. A clustering-based technique has been devised for estim ating globally matched wavelet filters using a collection of groundtruth images. We have extended our text extraction scheme for the segmentation of document images into text, background, and picture components (which include graphics and continuous tone images). Multiple, two-class Fisher classifiers have been used for this purpose. We also exploit contextual information by using a Markov random field formulation-based pixel labeling scheme for refinement of the segmentation results. Experimental results have established effectiveness of our approach. 相似文献
995.
Electric field effect on metallic particle contamination in a common enclosure gas insulated busduct
Nagesh Kumar G.V. Singh B.P. Amarnath J. Srivastava K.D. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(2):334-340
Sulphur hexaflouride (SF6) is generally found to be very sensitive to field perturbations such as those caused by conductor surface imperfections and by conducting particle contaminants. A study of CIGRE group suggests that 20% of failures in gas insulated substations (GIS) is due to the existence of various metallic contaminations in the form of loose particles. The presence of contamination can therefore be a problem with gas-insulated substations operating at high fields. If the effects of these particles could be eliminated, then this would improve the reliability of compressed gas insulated substation. It would also offer the possibility of operating at higher fields to affect a potential reduction in the GIS size with subsequent savings in the cost of manufacture and installation. The purpose of this paper is to develop techniques, which will formulate the basic equations that will govern the movement of metallic particles like aluminum and copper in a bus duct. The simulation considers the electric field effect on particle movement and the results have been presented and analyzed 相似文献
996.
Galiveeti Hemakumar Reddy Malepati Krishnmurthy Kiran Pulumithi Sunil Kumar Arup Kumar Goswami Nalin B. Dev Choudhury 《电力部件与系统》2019,47(19-20):1791-1804
AbstractThe equipment failures are highly uncertain in nature and simple average failure rate will not reflect this uncertainty. The uncertainty level further increases in reliability evaluation due to the integration of wind farm (WF) because of the intermittent nature of wind speed and random charging patterns of plug-in electric vehicles (PEVs). In this work, the uncertain variables in the distribution system (failure rate, repair time, WF output, PEVs charging and system load factor) are represented as fuzzy numbers to handle the uncertainty. The available uncertain data are used to find the probability distribution function (PDF) of that parameter and is converted into fuzzy membership function using transformation techniques. Failure rate of equipment is converted into failure probability using Monte Carlo simulation (MCS) method. Sampling method is applied to create the PDF of a variable which has average value. Fuzzy severity index (FSI) is proposed to find the importance of an equipment on reliability and is evaluated by measuring the fuzzy distance between the fuzzy reliability indices. The proposed assessment method is validated on modified RBTS bus 2 by comparing with analytical and MCS methods. The proposed method has been tested with integration of WFs and PEVs. 相似文献
997.
AbstractThe distributed generation (DG) planning with the varying pattern of the practical load is difficult as it calls for the frequent changes in DG size and system configuration, which is neither feasible nor permissible. Rather such a DG size and a configuration, which can be utilized over a wider load pattern, are more acceptable. This work presents a coordinated approach for DG planning and system reconfiguration. While to operate a particular DG size and the system configuration over a wide range of loading pattern, the configurations are ranked under different probabilistic loading patterns. Based upon the ranking of the new configuration, the energy performance of the coordinated planning is evaluated. Further, the observations from coordinated planning are imposed on coordinated operation using harmony search algorithm (HSA). The proposed approach is tested for single as well as multi-objectives on a 33-node system. A significant improvement in the computational efforts and energy performance of the resulting configuration have been observed where losses have reduced to 81.11 and 53.77?kW with single DG and multi-DG allocation respectively. 相似文献
998.
Vundru Anil Kumar Kandru Ammani Rajkumari Jobina Paramanandham Parasuraman Busi Siddhardha 《IET nanobiotechnology / IET》2016,10(6):382
Green synthesis of silver nanoparticles (AgNPs) using plant extracts has been achieved by eco‐friendly reducing and capping agents. The present study was conducted to evaluate the larvicidal efficacies of AgNPs synthesized using aqueous leaf extracts of Excoecaria agallocha against dengue vector, Aedes aegypti. The 3rd and 4th instar larvae of A. aegypti were exposed to various concentrations of aqueous extracts of E. agallocha, synthesized AgNPs and also crude solvent extracts (methanol and chloroform) for 24 h. The formation of AgNPs using aqueous leaf extracts was observed after 30 min with a characteristic colour change. The results recorded from UV‐Vis spectrum, XRD, FTIR, EDX, SEM and HR‐TEM were used to characterize and confirm the biosynthesis of AgNPs. The highest larvicidal efficacy of synthesized AgNPs was observed against 3rd instar larvae at LC50 4.65 mg/L, LC90 14.17 mg/L and 4th instar larvae with a concentration of LC50 6.10 mg/L, LC90 15.64 mg/L. A significant larvicidal activity was also observed with crude methanolic extracts against 3rd instar larvae at a concentration LC50 41.74 mg/L, LC90 123.61 mg/L and 4th instar larvae at a concentration of LC50 52.06 mg/L, LC90 166.40 mg/L as compared to the chloroform extract.Inspec keywords: silver, nanoparticles, nanofabrication, microorganisms, cellular biophysics, organic compounds, ultraviolet spectra, visible spectra, X‐ray diffraction, Fourier transform infrared spectra, X‐ray chemical analysis, scanning electron microscopy, transmission electron microscopyOther keywords: larvicidal activity, green synthesised silver nanoparticles, Excoecaria agallocha L. leaf extract, Aedes aegypti, plant extracts, capping agents, larvicidal efficacies, aqueous leaf extracts, excoecaria agallocha, dengue vector, Aedes aegypti, aegypti, aqueous extraction, E. agallocha, crude solvent extracts, methanol, chloroform, characteristic colour change, ultraviolet‐visible spectrum, X‐ray diffraction, Fourier‐transform infrared spectroscopy, EDX, scanning electron microscopy, high‐resolution transmission electron microscopy, AgNP biosynthesis, larvicidal efficacy, third instar larvae, instar larvae, crude methanolic extracts, chloroform extraction, time 24 h 相似文献
999.
Raj Kumar Sahu 《先进材料力学与结构力学》2016,23(2):170-179
This article experimentally studied the large nonlinear deformation of VHB 4910 elastomer by uniaxial tests. The study reveals that the monotonic tensile stress-strain, hysteresis, cyclic stress softening, and multistep stress relaxation of this elastomer exhibit rate-sensitivity. Toughness, failure stress, and failure strain are shown to vary with strain rate. Maximum cyclic stress, hysteresis loss, residual strains in cyclic loading-unloading, and stress relaxation in multistep relaxation tests are also shown to be rate-sensitive. The analytical models are also proposed to predict certain important parameters, such as dissipative work, cyclic stress softening, cyclic residual strain, and relaxation stress in different states of deformation. 相似文献
1000.
Hydrothermally Oxidized Single‐Walled Carbon Nanotube Networks for High Volumetric Electrochemical Energy Storage 下载免费PDF全文
Tianyuan Liu Amir A. Bakhtiary Davijani Jingying Sun Shuo Chen Satish Kumar Seung Woo Lee 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(25):3423-3431
Improving volumetric energy density is one of the major challenges in nanostructured carbon electrodes for electrochemical energy storage device applications. Herein, a simple hydrothermal oxidation process of single‐walled carbon nanotube (SWNT) networks in dilute nitric acid is reported, enabling simultaneous physical densification and chemical functionalization of the as‐assembled randomly‐packed SWNT films. After the hydrothermal oxidation process, the density of the SWNT films increases from 0.63 to 1.02 g cm?3 and a considerable amount of redox‐active oxygen functional groups are introduced on the surface of the SWNTs. The functionalized SWNT films are used as positive electrodes against Li metal negative electrodes for potential Li‐ion capacitors or Li‐ion battery applications. The functionalized SWNT electrodes deliver high volumetric as well as gravimetric capacities, 154 Ah L?1 and 152 mAh g?1, respectively, owing to the surface redox reactions between the introduced oxygen functional groups and Li ions. In addition, these electrodes exhibit a remarkable rate‐capability by retaining its high capacity of 94 Ah L?1 (92 mAh g?1) at a high discharge rate of 10 A g?1. These results demonstrate the simple hydrothermal oxidation process as an attractive strategy for improving the volumetric performance of nanostructured carbon electrodes. 相似文献