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991.
Sumit Kumar Jana Asit Baran Biswas Sudip Kumar Das 《Korean Journal of Chemical Engineering》2014,31(4):574-581
Experimental studies on the gas holdup in two tapered bubble columns using non-Newtonian pseudoplastic liquid have been reported. The effects of different variables such as gas flow rate, liquid viscosity, bed height, and orifice diameter of sieve plate on gas holdup have been investigated. An empirical correlation has been developed for the prediction of the gas holdup as a function of various measurable parameters of the system. The correlation is statistically acceptable. 相似文献
992.
The effect of liquid and gas velocities, solid concentrations, and operating pressure has been studied experimentally in a 15 cm diameter air-water-glass beads bubble column. The superficial gas and liquid velocities varied from 1.0 to 40.00 cm/s and 0 to 16.04 cm/s, respectively, while the solid loading varied from 1 to 9%. The gas holdup in the column was reduced sharply as we switched from batch to co-current mode of operation. At low gas velocity, the effect of liquid velocity was insignificant; while at high gas velocity, increasing liquid velocity decreased the gas holdup. Drift flux approach was applied to quantify the combined effect of liquid and gas velocities over gas holdup. For co-current three phase flows, the gas holdup decreased with increase in solid loading for all pressures. But for batch operations, when solid loading was 5% or more, settling started leading to higher gas holdup. Increasing pressure from atmospheric conditions increased the gas holdup significantly, flattening asymptotically. 相似文献
993.
Experimental investigation has been done in unbaffled gas-liquid stirred tanks using dual concave blade impeller to analyze the mass transfer, power consumption and gas holdup. Optimal impeller clearance has been suggested for lower and upper impeller based on maximum mass transfer rate. Numerical modeling has been done to analyze the flow pattern for different combinations of impeller clearance. The lower impeller positioned at 0.3 of tank diameter and clearance between lower and upper impeller at 0.4 of tank diameter gave the maximum mass transfer coefficient. Scale-up criteria for mass transfer rate, power and gas holdup have been developed for optimal geometrical similar systems of unbaffled stirred tanks with dual concave impeller. 相似文献
994.
Mohd. Hashim Sagar E. Shirsath S.S. Meena Pramod Bhatt R.K. Kotnala Shalendra Kumar Ravi Kumar Dachepalli Ravinder Alimuddin 《Ceramics International》2014
The Cr3+ ions doped multi-oxide ZnFe2−xCrxO4 ferrite nanoparticles have been synthesized by chemical co-precipitation method. Site occupancies of Zn2+, Cr3+ and Fe3+ ions were analyzed using X-ray diffraction data and Buerger's method. The effect of the constituent phase variation on the magnetic hysteresis behavior was examined by saturation magnetization which decreases with the increase in Cr3+ content in place of Fe3+ ions at octahedral B-site. Typical blocking temperature (TB) around 90 K was observed by zero field cooling and field cooling magnetization study. Room temperature Mössbauer spectra show two paramagnetic doublets (tetrahedral and octahedral sites). The isomer shifts of both doublets decrease whereas quadrupole splitting and relative area of tetrahedral A-site increases with increasing Cr3+ substitution. The dielectric constant (measured on compositions x=0, 0.4, 0.8 and 1.0) increases when the temperature increases as in the semiconductor. This behavior is attributed to the hopping of electrons between Fe2+ and Fe3+ ions with a thermal activation. 相似文献
995.
Sandan Kumar Sharma B. Venkata Manoj Kumar Kwang-Young Lim Young-Wook Kim S.K. Nath 《Ceramics International》2014
Dense silicon carbide (SiC) ceramics were prepared with 0, 10, 30 or 50 wt% WC particles by hot pressing powder mixtures of SiC, WC and oxide additives at 1800 °C for 1 h under a pressure of 40 MPa in an Ar atmosphere. Effects of alumina or SiC erodent particles and the WC content on the erosion performance of sintered SiC–WC composites were assessed. Microstructures of the sintered composites consisted of WC particles distributed in the equi-axed grain structure of SiC. Fracture surfaces showed a mixed mode of fracture, with a large extent of transgranular fracture observed in SiC ceramics prepared with 30 wt% WC. Crack bridging by WC enhanced toughening of the SiC ceramics. A maximum fracture toughness of 6.7 MPa*m1/2 was observed for the SiC ceramics with 50 wt% WC, whereas a high hardness of 26 GPa was obtained for the SiC ceramics with 30 wt% WC. When eroded at normal incidence, two orders of magnitude less erosion occurred when SiC–WC composites were eroded by alumina particles than that eroded by SiC particles. The erosion rate of the composites increased with increasing angle of SiC particle impingement from 30° to 90°, and decreased with WC reinforcement up to 30 wt%. A minimum erosion wear rate of 6.6 mm3/kg was obtained for SiC–30 wt% WC composites. Effects of mechanical properties and microstructure on erosion of the sintered SiC–WC composites are discussed, and the dominant wear mechanisms are also elucidated. 相似文献
996.
The solvothermal synthesis of highly luminescent and homogeneous Gd2O3:Eu3+ nanophosphor using diethylene glycol as medium, followed by controlled combustion with citric acid as fuel is reported. The influence of concentrations of carboxylic acid and metal cations on the structure, morphology and luminescence properties are investigated in detail. The microscopic investigations indicate the nanocrystalline nature and the strong influence of cation concentration on the size, shape and agglomeration of the particles. It is found that increase in concentration of metal cations lead to the reduction in agglomeration of nanophosphors. The large value of intensity parameter Ω2, suggested that Eu3+ ions reside in a more asymmetric environment, resulted in intense emission due to 5D0–7F2 electric dipole transition. Emission decay analysis of the samples exhibited one exponential nature. The samples prepared under optimum conditions showed a quantum efficiency of 78.63% and a moderately high life time of 1.217 ms. 相似文献
997.
Ansuman Barman Nilesh Kumar Shrivastava Bhanu Bhusan Khatua Bidhan Chandra Ray 《Polymer Composites》2015,36(12):2157-2166
Here we report the preparation and characterization of a green composite based on high‐density polyethylene and Kaans grass (Saccharum spontaneum). The composites were prepared by conventional melt‐mixing method, using maximum loading of Kaans grass in powder form (KG‐filler) to achieve acceptable range of required properties. Maleic anhydride grafted polyethylene was used as compatibilizer to achieve effective interaction for improved surface adhesion which was confirmed by FT‐IR spectroscopy. Morphological studies revealed good interaction between the base polymer matrices and the KG‐fillers that improved the mechanical and thermal properties of the composites up to certain (10 phr) KG‐filler loading. Study on water absorption property revealed moderate increase in weight at higher KG‐filler loadings. Thermogravimetric analysis (TGA) and melt flow index (MFI) studies indicated retention of thermal stability and flow property of the HDPE/KG‐filler composite at lower filler loadings. POLYM. COMPOS., 36:2157–2166, 2015. © 2014 Society of Plastics Engineers 相似文献
998.
Jaspal Singh Sanjeev Kumar N. K. Verma 《Journal of Materials Science: Materials in Electronics》2014,25(5):2267-2272
Cd1?xNixSe (x = 0.0, 0.02, 0.05 and 0.1) nanoparticles have been synthesized by chemical route. X-ray diffraction analysis shows crystalline nature of synthesized nanoparticles possessing wurtzite phase having hexagonal structure. Transmission electron microscopy depicts spherical morphology and uniform particle size distribution of pure and Ni-doped CdSe nanoparticles. The blue-shift in band gap has been observed with Ni-doping concentration. Photoluminescence study shows the presence of intrinsic defects (VCd–VSe) in the synthesized nanoparticles. Electron spin resonance (ESR) analysis reveals the long range ferromagnetic ordering in pure and doped nanoparticles. ESR study also indicates that Ni ions exist in +2 oxidation state in host nanoparticles. The magnetic hysteresis (M-H) loops display ferromagnetism at room temperature in pure and Ni-doped CdSe nanoparticles. The increase of ferromagnetic behavior has been observed with Ni-doping concentration. M-H analyses indicate that defects and carrier mediated exchange interactions are responsible for ferromagnetic ordering, in the present study. 相似文献
999.
Susanta Kumar Saha Ashis Banerjee Shashwat Banerjee Susmita Bose 《Materials science & engineering. C, Materials for biological applications》2009,29(7):2294-2301
Hydroxyapatite (HA) nanopowder was synthesized by reverse microemulsion technique using calcium nitrate and phosphoric acid as starting materials in aqueous phase. Cyclohexane, hexane, and isooctane were used as organic solvents, and Dioctyl sulfosuccinate sodium salt (AOT), dodecyl phosphate (DP), NP5 (poly(oxyethylene)5 nonylphenol ether), and NP12 (poly(oxyethylene)12 nonylphenol ether) as surfactants to make the emulsion. Effect of synthesis parameters, such as type of surfactant, aqueous to organic ratio (A/O), pH and temperature on powder characteristics were studied. It was found that the surfactant templates played a significant role in regulating the morphology of the nanoparticle. Hydroxyapatite nanoparticle of different morphologies such as spherical, needle shape or rod-like were obtained by adjusting the conditions of the emulsion system. Synthesized powder was characterized using X-ray diffraction (XRD), BET surface area and transmission electron microscopy (TEM). Phase pure HA nanopowder with highest surface area of 121 m2/g were prepared by this technique using NP5 as a surfactant. Densification studies showed that this nanoparticle can give about 98% of their theoretical density. In vitro bioactivity of the dense HA compacts was confirmed by excellent apatite layer formation after 21 days in SBF solution. Cell material interaction study showed good cell attachment and after 5 days cells were proliferated on HA compacts in OPC1 cell culture medium. The results imply this to be a versatile approach for making hydroxyapatite nanocrystals with controlled morphology and excellent biocompatibility. 相似文献
1000.
Raj Kumar Singh Sunil Kumar Sinha A. Rama Rao 《Nuclear Engineering and Design》2009,239(10):1760-1767
The primary function of the shut down system in a nuclear reactor is to terminate any reactivity transient occurring in the core during its entire design life. Normally there is more than one system, which are independent and diverse in its mode of operation. They consist of quick acting mechanisms like dropping of safety rods by gravity, poison injection, etc. Typically in liquid poison injection system wherein high flow velocities are involved, there is significant fluid structure interaction associated with cyclic shock transients in the system. One such phenomenon has been captured and analyzed to understand the dynamics involved in the loop. The trends of loop pressure and vibration indicated presence of more than two pressure transients after complete injection of poison. The first transient arrived after 1.44 s and the second after 0.75 s. The reverse pressure pulses that manifested in the loop as a result of fast injection of fluid has been mathematically characterized by solving basic fluid balance equations. Possibility of ball lifting due to momentum pulse is also discussed. 相似文献