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11.
Sanjeev A. Sahu Pradeep K. Saroj Nidhi Dewangan 《Archive of Applied Mechanics (Ingenieur Archiv)》2014,84(2):235-245
The effect of gravity, heterogeneity and internal friction on propagation of SH-waves (horizontally polarised shear waves) in viscoelastic layer over a half-space has been studied. Using the method of separation of variables, dispersion equation has been obtained and used to recover the damped velocity of SH-waves. Both the real and imaginary parts of dispersion equation are in well agreement with the classical Love wave equation. It has been observed that heterogeneity of the medium affects the velocity profile of SH-wave significantly. Some other peculiarities have been observed and discussed in our study. 相似文献
12.
The performance of active queue management (AQM) is measured in terms of throughput, delay, queue size, and loss rate. We have carried out the optimized performance measure of throughput for AQM scheme random early detection (RED) using full factorial design (FDD) technique that is a new approach of performance analysis particularly for congestion control algorithms. We have considered the input factors, viz, buffer size, maximum threshold, and the number of file transfer protocol (FTP) sources for the evaluation of RED that can be used for other AQM schemes, viz, adaptive RED, three‐section RED (TRED), and adaptive queue management with random dropping (AQMRD). The effect of each input factor as well as their interactions are evaluated using factorial design technique that results to obtain the nonlinear equation for performance measure in terms of input factors buffer size, maximum threshold, and the number of FTP sources. Finally, we show the contour plots for variation of performance measure throughput (steady state) from minimum to maximum values with respect to the different setting of input parameters. 相似文献
13.
Sanjeev Kumar Pandey S. L. Patil Praveen V. Pol S. B. Phadke 《International Journal of Electronics》2020,107(10):1682-1703
ABSTRACT In this paper, two control schemes for boost converters affected by uncertainties in input voltage and load are proposed. The boost converter dynamics is redefined in terms of new state variables to facilitate the use of a disturbance observer that can estimate matched and unmatched disturbances. A sliding surface, which is new in the context of boost converters, is proposed to enable tracking and regulation of output voltage without requiring measurement of input voltage and load current. The stability of the overall system including the disturbance observer, the sliding variable and the output is proved. The performance of the schemes is assessed for regulation of output voltage and tracking of reference voltage by simulation as well as experimentation in which various types of uncertainties and various types of reference voltages are considered. 相似文献
14.
15.
Sanjeev K. Sharma Sungeun Heo Byoungho LeeHwangho Lee Changmin KimDeuk Young Kim 《Current Applied Physics》2014,14(12):1696-1702
We report on an n-ZnO/p-GaN heterojunction diode fabricated from zinc oxide (ZnO) films at various growth temperatures (450, 500, 550, and 600 °C) by RF sputtering. The films were subsequently annealed at 700 °C in N2 ambient. To investigate the influence of the growth temperature of n-ZnO films, the microstructural, optical, and electrical properties were measured using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Hall measurements. The XRD pattern showed the preferred orientation along the c-axis (002) regardless of growth temperature. The PL spectra showed a dominant sharp near-band-edge (NBE) emission. Current–voltage (I–V) curves showed excellent rectification behavior. The turn-on voltage of the diode was observed to be 3.2 V for the films produced at 500 °C. The ideality factor of ZnO film was observed to be 1.37, which showed the best performance of the diode. 相似文献
16.
Vishwanath Bhat H. R Shivakumar Rai K. Sheshappa Sanjeev Ganesh P. Prasad G. S. Guru 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):920-926
Blends of Pullulan (PU) and Polyacrylamide (PAM) having biomedical applications were prepared and characterized in order to evaluate the miscibility of natural component with the synthetic one. Blends with different composition ratios were prepared using water as common solvent. Viscosity, ultrasonic velocity and density were measured at 30 and 40°C. Furthermore, the blend films were prepared by a solution casting method and analyzed by DSC, FTIR and TGA methods. Results of ultrasonic and density methods revealed the semi-miscibility of the blend. Using viscosity data, interaction parameters (Chee's ‘μ’ and Sun's ‘α’) were computed. The values confirmed that the blend is miscible when the Pullulan content is less than 20% in the blend. Change in temperature had no effect on the miscibility nature of the blends. Intermolecular interactions of hydrogen bonding type were confirmed by DSC and FTIR methods. Thermal behavior of blends was investigated using TGA method. 相似文献
17.
Sanjeev Kumar Aavula Anil ChikkulapalliN. Hanumanthappa Indira JyothiC.H. Vinod Kumar Sulur G. Manjunatha 《Tetrahedron letters》2013
A series of carboxylic acids were converted into their corresponding esters using the Pd/C catalyzed hydrogenation conditions in the presence of catalytic bromobenzene in alcohols and the method could also be applicable for the transesterification of esters. Good to excellent yields were obtained for different aliphatic or aromatic starting materials. The success of this esterification relies on the in situ generation of hydrobromic acid (HBr) from bromobenzene which provides a mild and acidic reaction environment. The palladium catalyst exhibits a remarkable activity and is reusable for up-to three consecutive cycles. 相似文献
18.
Vinod Kumar Punesh Sangwan A. K. Verma Sanjeev Agrawal 《Applied biochemistry and biotechnology》2014,173(2):646-659
Phytic acid is the major storage form of organic phosphorus in nature- and plant-based animal feed. It forms insoluble complexes with nutritionally important metals and proteins that are unavailable for monogastric or agastric animals. Phytases initiate the stepwise hydrolysis of phytic acid and release inorganic orthophosphate. In the present investigation, the phytase gene from a phytase producing Bacillus licheniformis strain PB-13 was successfully expressed in Escherichia coli BL21. Recombinant phytase ‘rPhyPB13’ was found to be catalytically active, with an activity of 0.97 U/mL and specific activity of 0.77 U/mg. The rPhyPB13 was purified to 14.10-fold using affinity chromatography. Similar to other β-propeller phytases, purified rPhyPB13 exhibited maximal activity at pH 6.0–6.5 and 60 °C in the presence of 1 mM Ca2+ and was highly active over a wider pH range (pH 4.0–8.0) and high temperature (80 °C). It has shown maximum activity towards Na-phytate as substrate. The observed K m , V max and k cat of purified rPhyPB13 were 1.064 mM, 1.32 μmol/min/mg and 27.46 s?1, respectively. PhyPB13 was resistant to trypsin inactivation, activated in presence of Ca2+ and inhibited in presence of EDTA. Crude rPhyPB13 has good digestion efficiency for commercial feed and soybean meal. These results indicate that PhyPB13 is a β-propeller phytase that has application potential in aquaculture feed. 相似文献
19.
Among physical and nutritional parameters optimized by “one variable at a time” approach, four cultural variables (sucrose,
MgSO4
.7H2O, inoculum size, and incubation period) significantly affected glucoamylase production. These variables were, therefore,
selected for optimization using response surface methodology. The p-values of the coefficients for linear effect of sucrose and inoculum size were less than 0.0001, suggesting them to be the
key experimental variables in glucoamylase production. The enzyme production (34 U/ml) attained under optimized conditions
(sucrose, 2%; MgSO4
.7H2O, 0.13%; yeast extract, 0.1%; inoculum size, 5 × 106 spores per 50 ml production medium; incubation time, 48 h; temperature, 40°C; and pH 7.0) was comparable with the value predicted
by polynomial model (34.2 U/ml). An over all 3.1-fold higher enzyme titers were attained due to response surface optimization.
The experimental model was validated by carrying out glucoamylase production in shake flasks of increasing capacity (0.25–2.0 l)
and 22-l laboratory bioreactors (stirred tank and airlift), where the enzyme production was sustainable. Furthermore, the
fermentation time was reduced from 48 h in shake flasks to 32 h in bioreactors. 相似文献
20.
A genetic algorithm (GA) based strategy is presented for deducing an exact or near-exact functional form from a time series. The GA formalism proposed here utilizes (i) the "postfix" representation with a view to reduce the procedural complexities and (ii) the "elitist mating" scheme to produce fitter offspring strings. The GA procedure is exemplified by considering chaotic time series of the well-known logistic, Henon and universal maps. The GA correctly recovers the underlying functional forms for the respective time series. Measurements from a number of finite-dimensional physical, biological, and other systems often give rise to complex time series and the presented methodology should prove useful in obtaining functional forms describing accurately the evolution of the time series. (c) 1999 American Institute of Physics. 相似文献