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排序方式: 共有453条查询结果,搜索用时 187 毫秒
31.
In the present investigation, AB5-type hydrogen storage alloys with compositions Mm0.8La0.2Ni3.7Al0.38Co0.3Mn0.5Mo0.02 and Mm0.75Ti0.05La0.2Ni3.7Al0.38Co0.3Mn0.5Mo0.02 are synthesized by radio-frequency induction melting. The electrochemical properties are studied through the measurements of discharge capacity, activation process, rate capability, self-discharge rate and cyclic stability of both the electrodes. Pressure-composition isotherms are plotted by converting the electrode potential into the hydrogen pressure following the Nernst equation. The structural and microstructural characterizations are performed by means of X-ray diffraction phase analysis and scanning electron microscopy of as-fabricated and electrochemically tested electrodes. An attempt is made to correlate the observed electrochemical properties with the structural–microstructural characteristics. 相似文献
32.
A practical approach towards mathematical modeling of deposition rate during twin-wire submerged arc welding 总被引:1,自引:1,他引:0
Abhay Sharma Navneet Arora Bhanu K. Mishra 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):463-474
The present paper deals with a shop floor applicable mathematical model for deposition rate during twin-wire submerged arc
welding. The salient features of this model are (1) instead of melting rate, as modeled during past investigations, it quantifies
the deposition rate, which is the actual outcome of the process and always remains smaller than the melting rate because of
evaporation or spatters losses and (2) it estimates electrode extension in order to predict the deposition rate which makes
the proposed model more practical than the models constituted with the help of experimental measurement of electrode extension.
The model is more scientific than the simplified models where contact tube to work-piece distance has been considered as the
electrode extension. A critical review of the relevant past investigation is given and a mathematical model is developed for
deposition rate during the twin-wire welding with both the polarities, i.e., direct current electrode positive and direct
current electrode negative. The model is calibrated using the results of 200 experimental runs and it is found to be very
accurate with very high coefficient of regression and admissible standard error. The developed model is further validated
with extra experimental runs. The practicality of the considered approach for prediction of deposition rate can further be
used in future research for other consumable arc welding processes. 相似文献
33.
Nainital City of Kumaun Lesser Himalaya is prone to mass wasting processes during monsoon season, which mischievously triggers the hill slope instability in this region. Slate, dolomitic limestone, silty sandstone and rhythmite of the Krol Formation are the main rock types. The present study focuses on the investigation of slope stability in the region in terms of potential seismicity and landslide. Geological and geotechnical mapping indicates that the major portion of the area is characterized by slope wash materials and buildings. The combination of 3–4 joint sets with one random joint is the main structure at outcrops. The major geological structures of this area are Nainital lake fault passing from the center of the lake, Main Boundary Thrust at SW, and Khuriya Fault passing from the SE direction of Nainital City. This work finds that different types of discontinuities (e.g. joints and faults), overburden due to unplanned civil structures, and neotectonic activity in the vicinity of this area affect the stability of the city. The slate forms the base of the city, dipping slightly towards the lake side along the NW direction, thus accelerating the instability of this area. Rock mass rating (RMR), slope mass rating, factor of safety (FOS) and graphical analysis of the discontinuity for slope kinematics indicate that the study area is a landslide-prone zone. This study can facilitate reducing the risk of human life, and contribute to the ongoing construction works in the area. 相似文献
34.
Ceria (La3+, Sr2+)/Carbonates Nanocomposite Electrolytes with High Electrical Conductivity for Low‐Temperature SOFCs
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Nandini Jaiswal Devendra Kumar Om Parkash Shail Upadhyay 《International Journal of Applied Ceramic Technology》2015,12(5):1080-1087
A series of ceria‐based nanocomposites consisting of lanthanum and strontium codoped ceria with composition Ce0.89La0.07Sr0.04O1.925 (CL7S4) and eutectic mixture of carbonates Li2CO3‐Na2CO3 (LNCO) have been prepared by mixing nanosize powders of CL7S4 and LNCO. Samples have been characterized using differential thermal analysis, X‐ray diffraction, scanning electron microscopy combined with energy‐dispersive spectroscopy, thermal expansion, and impedance spectroscopy. A sharp increase in ionic conductivity is observed in all the composite specimens corresponding to superionic transition. Sample containing 35 wt% of carbonate shows the maximum conductivity (2.56 × 10?1 S/cm at 500°C) with activation energy of conduction, Ea 0.23 eV. 相似文献
35.
P. S. Niranjan Ratna Shukla Santosh K. Upadhyay 《Journal of surfactants and detergents》2012,15(1):53-57
The aggregation behaviour of two cationic surfactants, viz. cetyl trimethyl ammonium bromide (CTAB) and N-cetyl pyridinium
chloride (CPC), in different concentrations of water-soluble polyacrylamide has been studied in alkaline medium by electrical
conductivity and surface tension measurements. A decrease in the critical micelle concentration (CMC) of the surfactant with
an increase in polymer content in the mixture was observed. The thermodynamic and surface parameters have been determined
and discussed. The results indicate that micellisation becomes more favourable at higher polymer content. 相似文献
36.
Due to variety of materials available to any designer for a particular application, there is a need for a proper technique to select. This paper focuses on the optimum selection of materials for electrostatic microactuators using Ashby approach. In this work, performance indices and material indices have been developed for electrostatic actuators and thereafter material selection chart is plotted. The selection chart shows that for high actuation voltage and high actuation force, diamond is the best possible candidate followed by silicon carbide and silicon nitride. On the other hand, if high speed electrostatic actuator is desired, then aluminum is the best possible candidate followed by nickel and copper. 相似文献
37.
Vinod Upadhyay Umesh D. Harkal Dean C. Webster Gordon P. Bierwagen 《Journal of Coatings Technology and Research》2013,10(6):865-878
The influence of structural and systematic compositional variations in glycidyl carbamate (GC) functional polymers on the electrochemical properties of their coatings was studied. There are few reports which focus on the correlation of structural and compositional variations in polymer films with their electrochemical barrier properties, diffusion properties with regards to water and aqueous electrolytes, and corrosion performance. To begin to fill this knowledge gap, two sets of GC functional polymers were studied. The polymer compositions were designed to vary the extent of polar hydrophilic groups, non-polar hydrophobic groups, and reactive epoxy groups in the final coatings. Impedance responses of the coatings were found to be closely related to the structural and compositional variations of these GC polymer films. In addition, single frequency EIS experiments were used in an attempt to understand the water uptake behavior of these polymer films using NaCl solution and ionic liquid under immersed condition. The resulting transport property data of the films was correlated to their polymer structure and composition. Moreover, a novel attempt at ranking the stability of coating using capacitance measurement during a cyclic wetting–drying condition was also attempted. The information obtained from this work can potentially be used to optimize the polymer for the specific performance properties needed in the protective coating applications, saving significant time and effort in the research and development stage. 相似文献
38.
39.
Tianhao Wang Harpreet Sidhar Yuri Hovanski Piyush Upadhyay Blair Carlson 《Science & Technology of Welding & Joining》2013,18(2):178-184
ABSTRACTUnder tensile shear loading, fracture modes of dissimilar lap welds produced by friction stir scribe technology were studied. Three fracture modes were observed. For zone A fracture, the initial crack was restrained, and the joint ultimately fractured in the base mild steel. For zone B fracture, the initial crack progressed through the aluminium sheet just above the Al/steel interface. For zone C fracture, the initial crack proceeded along the steel hook to the aluminium sheet surface. Fracture mode and joint strength were greatly influenced by steel hook size, and the steel hook size was affected by welding parameters and tool scribe height. In this study, the experimental joint strength achieved the calculated joint load limit. 相似文献
40.
Availability analysis of steam and power generation systems in the thermal power plant 总被引:1,自引:0,他引:1
The paper discusses the availability analysis of a steam generation system consisting of three subsystems A, B and D and a power generation system consisting of four subsystems E, F, G and H arranged in series, with three states viz., good, reduced and failed. Taking constant failure and repair rates for each working unit, the mathematical formulation is done using the Birth-Death process. Expressions for steady state availability and the MTBF (mean time between failure) are derived. The graphs are given, depicting the effect of failure and repair rates on the system availability. The results are supplied to the plant personnel, to plan the policies for failure free running of the systems for a long duration. 相似文献