Correction of high gradient quadrupole harmonics with magneticshims

Superconducting quadrupole magnets with 70 mm aperture and nominal field gradient of 215 T/m are being developed by the US-LHC Accelerator Project for the Interaction Regions of the Large Hadron Collider. Due to large beam size and orbit displacement in the final focusing triplet, these magnets are subject to stringent field quality requirements. For this reason, a correction scheme based on design calculations, fabrication issues and tests results involving magnetic shims     

Photoelectrochemical performances of indium-doped CdS0.2Se0.8 thin film electrodes prepared by spray pyrolysis

Polycrystalline undoped and indium-doped CdS_0.2Se_0.8 thin films were deposited on FTO-coated glass substrates by spray pyrolysis. The cell configurations CdS_0.2Se_0.8/1 M (Na₂S + S + NaOH)/C and In:CdS_0.2Se_0.8/1 M (Na₂S + S + NaOH)/C were used to study a wide range of photoelectrochemical characteristics including capacitance–voltage in the dark, current–voltage characteristics in the dark and under illumination, photovoltaic power output and spectral response and to perform electrochemical impedance spectroscopy studies. The study reveals that the films exhibit n-type conductivity. Various PEC parameters such as the junction ideality factor under illumination, series and shunt resistances, fill factor and efficiency have been estimated for the PEC cells formed with CdS_0.2Se_0.8 and indium-doped CdS_0.2Se_0.8 thin films. The efficiency and fill factor of these PEC cells are found to be improved from 0.79% and 0.46 to 2.12% and 0.49, respectively, with indium doping in CdS_0.2Se_0.8 thin films. Electrochemical impedance spectroscopy studies show that doping of indium into CdS_0.2Se_0.8 thin film improves the performance of resulting PEC cells.     

Thermal instability of rotating nanofluid layer

In the present paper we have considered thermal instability of rotating nanofluids heated from below. Linear stability analysis has been made to investigate analytically the effect of rotation. The more important effect of Brownian motion and thermophoresis has been included in the model of nanofluid. Galerkin method is used to obtain the analytical expression for both non-oscillatory and oscillatory cases, when boundaries surfaces are free–free. The influence of various nanofluids parameters and rotation on the onset of convection has been analysed. It has been shown that the rotation has a stabilizing effect depending upon the values of various nanofluid parameters. The critical Rayleigh number for the onset of instability is determined numerically and results are depicted graphically. The necessary and sufficient conditions for the existence of over stability are also obtained.     

Natural frequencies of composite plates with random material properties using higher-order shear deformation theory

Composites are known to display a considerable amount of scatter in their material properties due to large number of parameters associated with the manufacturing and fabrication processes. In the present work, the material properties have been taken as random variables for accurate prediction of the system behavior. Higher order shear theory including rotatory inertia effects has been accounted for in the system dynamic equations. A first order perturbation technique has been employed to obtain the solution of the governing equations. An approach has been outlined for obtaining closed form expressions for the variances of eigen solutions. The effects of side to thickness ratio and variation in standard deviation of the material properties have been investigated for cross-ply symmetric and anti-symmetric laminates. The mean and standard deviations of the first five natural frequencies have been worked out for laminated rectangular plates with all edges simply supported. The higher order shear deformation theory results have been validated with Monte Carlo simulation results and compared with the results based on classical laminate and first order shear deformation theories.     

Dielectric and impedance study of lead-free ceramic: (Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>)ZrO<Subscript>3</Subscript>

Polycrystalline sample of (Na_0.5Bi_0.5)ZrO₃ was prepared using a high-temperature solid-state reaction technique. XRD analysis indicated the formation of a single-phase orthorhombic structure. Dielectric study revealed the diffuse phase transition at 425 °C. AC impedance plots were used as tools to analyse the electrical behaviour of the sample as a function of frequency at different temperatures. The ac impedance studies revealed the presence of grain boundary effect at and above 350 °C. Complex impedance analysis indicated non-Debye type dielectric relaxation and negative temperature coefficient of resistance (NTCR) character of (Na_0.5Bi_0.5)ZrO₃. AC conductivity data were used to evaluate the density of states at Fermi level and activation energy of the compound. DC electrical and thermal conductivities of grain and grain boundary have been assessed.     

Theoretical analysis of absorption of chlorine in aqueous slurries of calcium hydroxide: Desorption of hypochlorous acid gas

A theory has been developed for the absorption of chlorine in aqueous slurries of calcium hydroxide accompanied by a two-step instantaneous reaction and desorption and simulation is carried out to study the effects of various parameters. The rates of absorption of chlorine and desorption of HOC1 from the aqueous slurry are enhanced when fine particles are present in two diffusion film regions on the liquid side. It is concluded that intensification in the rates of absorption of chlorine and rates of desorption can be realized by using high loading of smaller particle size. An optimum k_L must be used to enhance rates of Cl₂ absorption and HOG desorption in order to permit the formation of two reaction planes in the diffusion film. Rates can be intensified by an order of magnitude by the proper selection of operating conditions.     

Structural,SEM and dielectric properties of PLZT

Powder of lanthanum-modified lead zirconate titanate (PLZT) with the composition La/Zr/Ti=8/65/35, was synthesized from aqueous nitrate solutions. A single-phase PLZT was obtained at ∼550 °C. The reactivity of the powder during low-temperature heating was determined using X-ray diffraction and various thermal analysis techniques. The dielectric properties of the compound were also studied at 1 and 10 kHz frequency from room temperature to 200 °C. Diffuse phase transition (DPT) in the material was observed around 136 °C at 1 kHz. An increase in peak-permittivity temperature (i.e. the transition temperature) with increasing frequency (a characteristic of relaxor ferroelectrics) was also observed.     

Freestanding 3D Graphene–Nickel Encapsulated Nitrogen‐Rich Aligned Bamboo Like Carbon Nanotubes for High‐Performance Supercapacitors with Robust Cycle Stability

3D hierarchical structures are reported based on graphene–nickel encapsulated nitrogen‐rich aligned bamboo like carbon nanotubes, which show not only high‐performance supercapacitance behavior but also a great robust cyclic stability. A facile synthesis route is developed of 2D nickel oxide decorated functionalized graphene nanosheets (2D‐NiO‐f:GNSs) hybrids and 3D nitrogen doped bamboo‐shaped carbon nanotubes (NCNTs) vertically standing on the functionalized graphene nanosheets (3D‐NCNT@f:GNSs) by using a thermal decomposition method. The chemical reduction and morphology‐dependent electrochemical response are investigated. The enhanced specific capacitance of 3D‐NCNT@f:GNSs as compared to that of 2D‐NiO‐f:GNSs suggests the synergistic effects and indicates the importance of energy storage and superior long‐term cycling performance that are achieved. This 3D‐NCNT@f:GNSs hybrid shows a remarkable cycling stability with a maximum power density of 12.32 kW kg⁻¹ and maximum energy density of 109.13 Wh kg⁻¹ due to the good connection of NCNT and f:GNSs. This unique 3D nano network architecture enables the availability of large surface areas of NCNT, thus endowing the nanohybrids with high specific capacitance and excellent reusability.     

Earthworm coelomocytes as nanoscavenger of ZnO NPs

Earthworms can ‘biotransform’ or ‘biodegrade’ chemical contaminants, rendering them harmless in their bodies, and can bioaccumulate them in their tissues. They ‘absorb’ the dissolved chemicals through their moist ‘body wall’ due to the interstitial water and also ingest by ‘mouth’ while soil passes through the gut. Since the advent of the nanotechnology era, the environmental sink has been continuously receiving engineered nanomaterials as well as their derivatives. Our current understanding of the potential impact of nanomaterials and their natural scavenger is limited. In the present investigation, we studied the cellular uptake of ZnO nanoparticles (NPs) by coelomocytes especially by chloragocytes of Eisenia fetida and their role as nanoscavenger. Results from exposure to 100- and 50-nm ZnO NPs indicate that coelomocytes of the earthworm E. fetida show no significant DNA damage at a dose lower than 3 mg/l and have the potential ability to uptake ZnO NPs from the soil ecosystem and transform them into microparticles.