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991.
Some applications require norm computation of frequency-truncated systems. A typical frequency-truncated system is one whose frequency response is rational in certain frequency bands and is zero in others. This note explains how to compute the L2 norm of such systems. 相似文献
992.
An n+-p-p+ structure was formed by depositing a thin Al layer on one side and a semitransparent Pd layer on other side of a p-Si wafer, and the diffusion length L was determined from the slope of short circuit current density Jsc vs. illumination intensity Pin characteristics by illuminating the p+ side with a laser light of wavelength λ = 789 nm, following the photocurrent generation method. The slope was found to decrease after the specimen was exposed to air for a few hours before the measurement. The present investigation revealed that the degradation of slope was owing to increase in surface recombination velocity S significantly, e.g. to 2800 cm/s for air exposure of 8 h, above its initial value 10 cm/s. This resulted from adsorption of moisture on Pd surface which decreases work function of Pd and lowers the accumulation potential barrier. The adsorbed water molecules could be removed from Pd surface by vacuum pumping and then S again became small and the slope regained its original value. The true value of L, smaller or larger than the wafer thickness, can be determined using single monochromatic illumination if S is known or has a negligibly small value, as in our case where the specimen was stored in vacuum. In our specimen we determined L = 56 μm when S was negligibly small. However, using the experimental slopes of Jsc-Pin curves at two monochromatic illuminations obtained by Sharma et al. we determined both S and L and found their values 1390 cm/s and 94 μm, respectively. 相似文献
993.
Dynamic model incorporating damping characteristics, namely joint damping and structural damping in flexible links, of the
serial robots with rigid and flexible links is presented. A novel procedure, based on the unified approach of theoretical
formulation and analysis of experimental data, is proposed for the estimation of damping coefficients. First, the dynamic
model of a robotic system with rigid and flexible links is presented. Next, the modifications in the dynamic model due to
the considerations of damping characteristics of joints and structural damping characteristics of the flexible links are presented.
A systematic methodology based on analysis of data obtained from experiments is presented for estimation and determination
of damping coefficients of rigid-flexible links. The determination of joint damping coefficients, is based on the logarithmic
decay of the amplitude of the oscillations of robotic links, while the structural damping coefficients are estimated mainly
using the modal analysis and the method of evolving spectra. The method of evolving spectra, based on the Fast Fourier Transform
of the decay of the amplitude in structural vibrations of the robot links in progressive windows is used to estimate the structural
damping ratios while the critical structural coefficients are determined using the modal analysis. The methodology is illustrated
through a series of simple experiments on simple robotic systems. The experimental results are then compared with the simulation
results incorporating the damping coefficients determined using the proposed procedure. The comparisons leads to the validation
of the proposed dynamic modeling technique, modeling of the damping characteristics, and the method proposed for estimation
of damping coefficients for rigid-flexible link robotic systems. 相似文献
994.
Swati Ghosh Vishav Preet Singh Rana Vivekanand Kain Vivek Mittal S.K. Baveja 《Materials & Design》2011,32(7):3823-3831
Effect of residual stress generated during tube fabrication, roll expansion and machining of stainless steel on the stress corrosion cracking (SCC) susceptibility was studied by testing fabricated tubes, tube–tube sheet joint and heavily machined plate of austenitic stainless steel (SS) in boiling MgCl2. U bend samples of machined plate were exposed to acidified SO4 + Cl? environment at room temperature to study its ambient temperature SCC behavior. The results correlate the SCC behavior of the SS tubes and roll expanded joints to the nature and magnitude of residual stresses present. The study also highlights the distinct difference in ambient temperature SCC behavior of machined vs. nonmachined surfaces. 相似文献
995.
Effect of Fiber Bridging Stress on the Fracture Resistance of Silicon-Carbide-Fiber/Zircon Composites 总被引:1,自引:0,他引:1
Yu-Lin Wang Umashankar Anandakumar Raj N. Singh 《Journal of the American Ceramic Society》2000,83(5):1207-1214
The room-temperature fracture-resistance behavior ( R -curve) of unidirectional silicon-carbide-fiber-reinforced zircon-matrix composites has been studied experimentally and numerically. The composites showed strong rising R -curve behavior from experimental results that used in situ crack-length measurements taken via optical microscopy as well as the compliance method. A numerical calculation, based on the available models, then was performed to determine the bridging-stress function from the experimental R -curve. In addition, the effect of the residual stress and constituent properties on the bridging-stress function also has been considered in the numerical calculations. These results have indicated that the bridging-stress function, which controls the fracture resistance of ceramic composites, can be obtained from the carefully measured R -curve. 相似文献
996.
In present communication, we propose a modified resource allocation strategy, namely, hybrid connection algorithm, for achieving efficient restoration in WDM optical networks. The main theme of the algorithm is that, while attempting connection establishment, a wavelength is reserved in advance for providing resources for backup lightpaths. The analysis and the comparison of the proposed strategy with other existing strategies has been undertaken using metrics such as, restoration efficiency, number of wavelength links used by primary and backup lightpaths, and the percent link utilization. The proposed strategy provides 100% restoration efficiency and much better performance than the existing techniques. 相似文献
997.
Brajesh Tiwari Babu Baijnath Prasad Rajveer Jha Dharmendra Kumar Singh V. P. S. Awana 《Journal of Superconductivity and Novel Magnetism》2014,27(10):2181-2183
In the present short letter, we report on the low dimensional 4d and 5d transition metals-chalcogenide based compounds i.e., Ta2PdxS6, showing semiconducting to superconducting transition at around 4K with their upper critical fields outside the Pauli paramagnetic limit. It seems couple of different superconducting phases do exist in these new set of compounds. Our short letter in this regards is thought provoking, asking to explore various unearthed possible new superconducting phases in (Nb/Ta)2Pdx(S/Se/Te)y systems. 相似文献
998.
The experimental results of a bed dryer (at Ludhiana) have been analyzed. The experimental results are well predicted by the small scale laboratory experiments on a spouted bed dryer. 相似文献
999.
1000.
Novel sol-gel derived calcium phosphate coatings on Mg4Y alloy 总被引:1,自引:0,他引:1
Abhijit RoySatish S. Singh Moni Kanchan DattaBoeun Lee J. OhodnickiPrashant N. Kumta 《Materials Science and Engineering: B》2011,176(20):1679-1689
Calcium phosphates (CaPs) and silicon containing calcium phosphates (Si-CaPs) coatings on a biodegradable magnesium yttrium alloy (Mg4Y) were prepared by a sol-gel technique to improve the bioactivity of the alloy surface. The experimental results show that thick porous coatings comprised of nano-sized calcium phosphate particles can be prepared by heating the as dip coated substrates at 450 °C. The in vitro degradation results show that the coatings do not alter the degradation kinetics of the substrates significantly and the release of magnesium and yttrium ions at initial time points was very similar for both the coated and bare substrates. The cyto-compatibility studies using MC3T3-E1 osteoblasts show that the coated substrates were more bioactive than the uncoated substrates as the cells begin to grow and form a matrix on the coated substrates more easily than on the bare metal. These preliminary results collectively show the potential of use of sol-gel derived calcium phosphate coatings on magnesium based degradable scaffolds to improve their surface bioactivity. 相似文献