The Specific Load Capacity of Radial-Flux Radial Magnetic Bearings

This paper addresses the specific load capacity of radial-flux radial magnetic bearings and provides some insight into what values are achievable and how these values depend on various parameters such as air-gap thickness, allowable temperature rise in the coils, certain heat-transfer coefficients, and certain de-rating factors associated with the distribution of the bearing load in time and space. We define the specific load capacity of a radial magnetic bearing as the ratio of the largest sustainable root-mean-square radial force to the total self-weight of all parts necessary for the electromagnetic function of the bearing. We show that it is possible to push the limit of the specific load capacity of naturally cooled bearings up to around 35:1 with present-day materials, for a wide range of practical bearing sizes. This figure is still very small compared with the capacity of mechanical bearings.     

Biotransformation of CI Acid Blue 113 and other dyes by Shewanella sp. P6

The isolate P₆, an indigenous Shewanella sp., was able to decolorise 90% of CI Acid Blue 113 in just 30 min of incubation under anoxic conditions. The decolorisation potential of cells was not significantly affected even in the presence of 2% (w/v) sodium chloride and 8% (w/v) sodium sulphate. Mass spectrometric analysis detected the formation of aniline sodium salt, 1,4‐diaminonaphthalene, 5‐amino‐8‐(phenylamino)‐naphthalene‐1‐sulphonic acid sodium salt and 8‐(phenylamino)‐naphthalene‐1‐sulphonic acid sodium salt. Further, cells of P₆ decolorised the raw effluent collected from the equalisation tank of a textile industry wastewater treatment plant. The water‐soluble dyes/intermediates present in the sludge, generated after chemical flocculation of raw effluent, were transformed by P₆ cells within 24 h of incubation under anoxic conditions. Thus, isolate P₆ has a potential application in the biological treatment of liquid and solid waste of textile processing plants because of its efficient decolorisation and transformation properties.     

Removal of iron from groundwater by ash: a systematic study of a traditional method

A traditional method for removal of iron from ground water by using ash has been systematically investigated. Ashes from five different sources, viz., banana rind, banana pseudostem, banana leaf, rice husk and bamboo has been studied. The principle applied is enhanced precipitation of iron at high pH caused by ash. The study included laboratory analysis of some relevant chemical parameters of the ashes and the efficiency of the ashes in removing iron from prefabricated water with respect to quantity of ash and corresponding increase in pH of water. The ash of banana pseudostem has been found to be most suitable for removal of iron. A low-cost and easily made iron removal system for household use has been designed and tested in the laboratory. The ash of banana pseudostem has been found to remove iron to below 0.3ppm without increasing the pH above the acceptable limit. The optimum values of the different parameters for removal of iron are 200-300mgl(-1) ash, 1.0lh(-1) flow rate and 1h of contact time with ash for groundwater having [Fe] of about 2.20ppm. The amount of ash can be increased for groundwater having higher [Fe] and can be decreased gradually during continuous use of the system. Acceptability of the method has been examined based on chemical analysis of the treated water. Increase in the essential minerals such as Ca, K has been observed in the water after treatment. The designed iron removing system is expected to be suitable for household use.     

Synthesis and characterization of poly(HEMA‐MAA) hydrogel carrier for oral delivery of insulin

Poly(HEMA‐MAA) hydrogel particles were synthesized by redox free‐radical polymerization using 2‐hydroxyethylmethacrylate, different concentration of methacrylic acid as monomer, ethyleneglycol dimethacrylate as crosslinking agent, and APS/TEMED as free‐radical initiator. Fourier transform infrared spectrum of poly(HEMA‐MAA) hydrogels showed intense absorption peak of carbonyl group at ～ 1700 cm^?1 due to carboxylic acid groups of MAA, peak at ～ 2960 cm^?1 due to CH stretching and vinylic peak at 1700 cm^?1 independent of MAA concentration. Highest swelling percentage 587% was observed in case of poly(HEMA‐MAA) hydrogel synthesized using 30% of MAA while lowest swelling percentage 413% was observed in hydrogel synthesized 10% of MAA at basic pH (8.0). Scanning electron micrograph of copolymeric particles showed the irregular shape of poly(HEMA‐MAA) particles with conglomeration with each due to ionization of carboxylic groups. Insulin was radiolabeled using technetium‐99m radionuclide and the radiolabeling efficiency was found to be 99%. Poly(HEMA‐MAA) hydrogel having 60% of MAA showed the highest insulin loading efficiency of 68% while lowest 37% was observed in case of 10% MAA hydrogel. Insulin release studies showed only 35–65% of insulin was released into the medium from particles at pH 2.5 in 60 min, while insulin release was significantly higher at pH 7.4. Hypoglycemic effect of the 60 and 80 I.U./kg insulin dose loaded in poly(HEMA‐MAA) copolymeric particles were carried out in fasted diabetic rats and highest decrease in blood glucose level from 506 mg/dL to 170 mg/dL was observed within first 3 h. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Synthesis of expanded graphite filled polyaniline composites and evaluation of their electrical and electrochemical properties

A series of conducting polyaniline/expanded graphite (PA/EG) composite was synthesized by in situ polymerization of aniline in acid medium followed by the addition of expanded graphite in various proportions (1, 2 and 3 wt%). The synthesized samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, ultraviolet–visible absorption, X-ray diffraction and by electrical conductivity measurements. The dc electrical conductivities of the composites were dramatically increased compared with pure polyaniline and found to be 0.50 × 10² S/cm to 6.11 × 10² S/cm. The PA/EG composites showed a reversible electrochemical response up to 150th repeated cycles as revealed by the cyclic voltametry study.     

Structural and electrical properties of Ba(Sb<Subscript>1/2</Subscript>Nb<Subscript>1/2</Subscript>)O<Subscript>3</Subscript> ceramic

Lead-free perovskite Ba(Sb_1/2Nb_1/2)O₃ was prepared by conventional ceramic fabrication technique at 1200 °C/5 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were determined from the experimental results using FullProf software whereas crystallite size and lattice strain were estimated from Williamson–Hall approach. XRD analysis of the compound indicated the formation of a single-phase monoclinic structure with the space group P2/m. EDAX and SEM studies were carried out to evaluate the quality and purity of the compound. Dielectric study revealed the frequency-dependent dielectric anomaly. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using the impedance data. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in Ba(Sb_1/2Nb_1/2)O₃. The ac conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and apparent activation energy of the compound.     

Chemical synthesis,structural characterization and electrical studies of nanoceria for CMOS applications

Cerium oxide nanoparticles were synthesized using cerium nitrate hexa hydrate and ammonium carbonate as precursors. Structural characterizations were done using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystallite size and lattice strain on the peak broadening of CeO₂ nanoparticles were studied using Williamson-Hall (W-H) analysis. The dielectric properties of nanocrystalline CeO₂ samples with different calcination temperatures, and frequencies have been studied over a temperature range from 303 to 423 K. It is found that the dielectric constant and dielectric loss for all temperatures have high values at low frequencies, which decreases rapidly as frequency is increased and attains a constant value at higher frequencies. The room temperature dielectric constant ε′ obtained for the as prepared CeO₂ nanoparticle sample is 61, which constitutes the highest value ever reported at low frequency. A.C. conductivity, which was derived from dielectric constant and loss tangent data, has a low value at smaller frequencies that increases as the frequency is increased. The dielectric constant and a.c. conductivity values are shifted upwards as the temperature is raised. However, these values are decreased as the annealing temperature is increased. The desired structural properties and high dielectric constant of nanophase CeO₂ make it as a promising material for the high dielectric constant dielectric gate in complementary metal oxide semiconducting (CMOS) devices.     

High temperature in-situ observations of multi-segmented metal nanowires encapsulated within carbon nanotubes by in-situ filling technique

Multi-segmented one-dimensional metal nanowires were encapsulated within carbon nanotubes (CNTs) through in-situ filling technique during plasma-enhanced chemical vapor deposition process. Transmission electron microscopy (TEM) and environmental TEM were employed to characterize the as-prepared sample at room temperature and high temperature. The selected area electron diffractions revealed that the Pd₄Si nanowire and face-centered-cubic Co nanowire on top of the Pd nanowire were encapsulated within the bottom and tip parts of the multiwall CNT, respectively. Although the strain-induced deformation of graphite walls was observed, the solid-state phases of Pd₄Si and Co-Pd remain even at above their expected melting temperatures and up to 1,550 ± 50°C. Finally, the encapsulated metals were melted and flowed out from the tip of the CNT after 2 h at the same temperature due to the increase of internal pressure of the CNT.