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排序方式: 共有713条查询结果,搜索用时 15 毫秒
121.
Satya Narayan Tripathy B.G. Mishra Mandar M. Shirolkar S. Sen Suprem R. Das David B. Janes Dillip K. Pradhan 《Materials Chemistry and Physics》2013
Polycrystalline nano BiFeO3 powders were synthesized by auto-combustion method using urea as fuel and metal nitrates (Fe(NO3)3·9H2O, Bi(NO3)3·5H2O) as oxidizers. In order to optimize the single-phase synthesis condition of BiFeO3, different fuel to oxidizer ratios have been investigated. The preliminary structural investigation using X-ray diffraction shows the samples were of single phase and crystallize in rhombohedral structure (R3c). The ferroelectric and antiferromagnetic ordering temperatures of BiFeO3 were found to be 832 °C and 364 °C respectively, from differential thermal analysis. The temperature dependent dielectric study shows an anomaly around 215 °C which corresponds to magneto-electric coupling in the material. Field-emission scanning electron micrographs show effect of fuel to oxidizer ratio on grain size evolution. The ferroelectric hysteresis loops for all the samples were measured at a frequency of 100 Hz confirming the ferroelectric nature. An evidence of magneto-electric coupling was also observed at room temperature from magneto-capacitance measurements. 相似文献
122.
Sunil K. Maity Narayan C. Pradhan Anand V. Patwardhan 《Applied catalysis. B, Environmental》2008,77(3-4):418-426
The reduction of nitrochlorobenzenes (NCBs) was carried out in an organic solvent, toluene, under liquid–liquid mode with phase transfer catalyst, tetrabutylammonium bromide (TBAB). The selectivity of chloroanilines (CANs) was found to be 100%. The reaction rate of m-nitrochlorobenzene (MNCB) was found to be highest among the three NCBs followed by o- and p-nitrochlorobenzene (ONCB and PNCB). The reactions were found to be kinetically controlled with apparent activation energies of 22.8, 19.6 and 9.4 kcal/mol for ONCB, PNCB and MNCB, respectively. The effects of different parameters such as TBAB concentration, NCB concentration, sulfide concentration, ammonia concentration, and elemental sulfur loading on the conversion and reaction rate of NCBs were studied to establish the mechanism of the reaction. The rate of reaction of NCBs was found to be proportional to the concentrations of the catalyst and NCBs and to the cube of the concentration of sulfide. A generalized empirical kinetic model was developed to correlate the experimentally obtained conversion versus time data for the three NCBs. 相似文献
123.
Logistic regression is frequently used in many areas of applied statistics. The maximum likelihood estimates (MLE) of the logistic regression parameters are usually computed using the iterative Newton-Raphson method. It is well known that these estimates are biased. Several methods are proposed to correct the bias of these estimates. Among them Firth (1993) and Cordeiro and McCullagh (1991) proposed two promising methods. The conditional exact method (CMLE) is popular for small-sample estimates, and is available in many software packages. In this article we compare these methods in terms of their bias. In general, our extensive simulations show that the methods proposed by Cordeiro and McCullagh and by Firth work well, though Cordeiro and McCullagh is slightly better in our simulations. In case of separation, Firth or CMLE can be used; however, a judicious approach is required when there is a wide variation in results. Two real data analyses are given exhibiting these properties. The data analysis also includes bootstrap results. 相似文献
124.
Upendra Nath Gupta Koteswara Rao Sivaram Pradhan Ratnesh Kumar Jha Harries Muthurajan Venkat Ravi 《International Journal of Applied Ceramic Technology》2008,5(1):101-104
Simple hydroxide precursors were used for the first time for the synthesis of a typical Aurivillius compound (SrBi2 Nb2 O9 (SBN)) at a low temperature. This method is very advantageous because it circumvents the use of SrCO3 in the case of conventional ceramics as well in the coprecipitation methods, thereby lowering the formation of the product phase. Commercially purchased strontium hydroxide is mixed thoroughly with freshly precipitated bismuth and niobium hydroxides in a stoichiometric ratio and heated at different temperatures ranging from 100°C to 750°C for 12 h. The sequence of the reaction and evolution of the product phase was monitored by X-ray diffraction (XRD) studies by recording the XRD for samples calcined at different temperatures. The incipient SBN phase begins to form at temperatures as low as 400°C, and phase formation was complete only at 650°C as revealed by the XRD observations. The differential thermal/thermogravimetric analyses) also corroborate this result. The morphology and average particle size of these powders were investigated by transmission electron microscopy studies. 相似文献
125.
Debabrata Pradhan 《Electrochimica acta》2008,54(2):430-433
Electrodeposition of metallic multilayers on Si is normally preceded by the vapour deposition of a metallic layer. Since vapour deposition produces an additional step in the production process, direct electrodeposition of multilayers on Si is desirable. However, direct electrodeposition on Si has resulted in low magnetoresistance (MR) - of the order of 1% - at room temperature. With the use of (i) electroless plated copper back contact, (ii) composite potentiostatic pulses, (iii) horizontal electrode configuration and (iv) non-continuous mode of deposition, a room temperature MR of 5.8% has been achieved. 相似文献
126.
Sandeep Panda Chinmaya Kumar Sarangi Nilotpala Pradhan Tondepu Subbaiah Lala Behari Sukla Barada Kanta Mishra Gur Lal Bhatoa Mullukutlashivram Prasad Subrat Kumar Ray 《Korean Journal of Chemical Engineering》2012,29(6):781-785
A process flowsheet was developed to recover copper metal from the lean sulfide ore of copper available at Malanjkhand, Hindustan Copper Limited (HCL), India. Copper pregnant leach solution (PLS) obtained from bio-heap leaching of chalcopyrite containing 0.3% copper was purified through solvent extraction (SX) and the copper recovered by electrowinning (EW). The copper-free raffinate obtained from SX stripping unit was returned back to the bioleaching circuit. The purity of the electrolytic copper produced at pilot scale was found to be 99.96%. During electrowinning, the effect of flow rate of electrolyte on current efficiency and energy consumption was also studied. 相似文献
127.
This work reports the facile synthesis of α-Fe(2)O(3) nanorods and nano-hexagons and its application as sunlight-driven photocatalysis. The obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), diffused reflectance spectroscopy (DRUV-vis), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The phase and crystallinity were confirmed from the XRD study. Electron microscopy study clearly indicates the formation of different morphologies of nanocrystals. These hematite nanostructures were used as a model system for studying the shape-dependent photocatalytic degradation of phenol, methylene blue, and congo red. Amongst all the nanostructured semiconductors, Pt-doped hematite nanorod showed 55% efficiency towards the decolonization of methylene blue and 63% toward congo red under sun light illumination. The difference in photocatalytic activity is discussed in terms of their crystallize size and morphological ordering. 相似文献
128.
Maityt D Pradhan P Chandrasekharan P Kale SN Shuter B Bahadur D Feng SS Xue JM Ding J 《Journal of nanoscience and nanotechnology》2011,11(3):2730-2734
In this paper, we report single step synthesis of hydrophilic superparamagnetic magnetite nanoparticles by thermolysis of Fe(acac)3 and their characterization of the properties relevant to biomedical applications like hyperthermia and magnetic resonance imaging (MRI). Size and morphology of the particles were determined by Transmission electron microscopy (TEM) while phase purity and structure of the particles were identified by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Magnetic properties were evaluated using vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) measurements. The as prepared nanoparticles were found to be superparamagnetic with the blocking temperature of 136 K and were easily suspendable in water. Cytotoxicity studies on human cervical (SiHa), mouse melanoma (B16F10) and mouse primary fibroblast cells demonstrated that up to a dose of 0.1 mg/ml, the magnetite nanoparticles were nontoxic to the cells. To evaluate the feasibility of their uses in hyperthermia and MRI applications, specific absorption rate (SAR) and spin-spin relaxation time (T2) were measured respectively. SAR has been calculated to be above 80 Watt/g for samples with the iron concentration of 5-20 mg/ml at 10 kA/m AC magnetic field and 425 kHz frequency. r2 relaxivity value was measured as 358.4 mM(-1)S(-1) which is almost double as compared to that of the Resovist, a commercially available MRI contrast agent. Thus the as-prepared magnetite nanoparticles may be used for hyperthermia and MRI applications due to their promising SAR and r2 values. 相似文献
129.
J. Mathew K. Maharatna B. R. Jose H. Rahaman D. K. Pradhan 《Circuits, Systems, and Signal Processing》2011,30(4):871-882
An optimal implementation of 128-Pt FFT/IFFT for low power IEEE 802.15.3a WPAN using pseudo-parallel datapath structure is
presented, where the 128-Pt FFT is devolved into 8-Pt and 16-Pt FFTs and then once again by devolving the 16-Pt FFT into 4×4
and 2×8. We analyze 128-Pt FFT/IFFT architecture for various pseudo-parallel 8-Pt and 16-Pt FFTs and an optimum datapath architecture
is explored. It is suggested that there exists an optimum degree of parallelism for the given algorithm. The analysis demonstrated
that with a modest increase in area one can achieve significant reduction in power. The proposed architectures complete one
parallel-to-parallel (i.e., when all input data are available in parallel and all output data are generated in parallel) 128-point
FFT computation in less than 312.5 ns and thereby meet the standard specification. The relative merits and demerits of these
architectures have been analyzed from the algorithm as well as implementation point of view. Detailed power analysis of each
of the architectures with a different number of data paths at block level is described. We found that from power perspective
the architecture with eight datapaths is optimum. The core power consumption with optimum case is 60.6 MW which is only less
than half of the latest reported 128-point FFT design in 0.18u technology. Furthermore, a Single Event Upset (SEU) tolerant
scheme for registers is also explored. The SEU tolerant scheme will not affect the performance, however, there is an increase
power consumption of about 42 percent. Apart from the low power consumption, the advantages of the proposed architectures
include reduced hardware complexity, regular data flow and simple counter based control. 相似文献
130.
Srikanta Dinda Narayan C. Pradhan Anand V. Patwardhan 《Chemical Engineering Communications》2013,200(8):1036-1040
In the present work, the self-polymerization reaction of cyclohexanone was studied to develop a synthetic resin. Synthetic resins are extensively used in paint industry to improve the adhesiveness of paints. Polymerization reactions were carried out in a high-pressure reactor. The results suggest that the self-polymerization of cyclohexanone mainly depends on alkali concentration, reaction temperature, and reaction time. As the ketone-to-alkali ratio decreases, the degree of polymerization increases, which leads to an increase in the hydroxyl value and softening point and a remarkable decrease in solubility. A good-quality solid resin could be obtained with a ketone-to-alkali ratio less than 5 in the temperature range between 130°C and 160°C and within the time duration of 12–22 h. These data may be useful to develop the desired quality of resin in the field of paint application. 相似文献