Effect of anions on the textural and catalytic activity of titania

An attempt has been made to review and studied the effect of ions (phosphate and sulfate) on titania samples. Surface area, average pore diameter and total pore volume increases however crystallite size decreases with increase in anion contents (both phosphate and sulfate case) up to 7.5 wt%, and thereafter decreases on further loading. TG-DTA and XRD patterns showed that phosphate stabilizes the anatase phase of TiO₂ up to 1173 K. FT-IR result showed that both phosphate and sulfate species strongly bound bidentately on TiO₂ support. Total acidity increases with increase in phosphate content up to 10.0 wt%, however, it increases up to 7.5 wt% in case of sulfated samples and thereafter decreases. Samples prepared at pH 3 and aqueous impregnation method exhibit higher acidity than the samples at pH 7 and solid-solid kneading method. Alkylation of benzene gives highest product (cumene) 70 mol% compared to others. Alkylation of aromatic compounds (benzene, toluene and chlorobenzene) with isopropanol is carried out in a fixed bed flow reactor over these catalysts as a function of benzene to isopropanol molar ratio, reaction temperature, percentage and source of sulfate ion.     

Structure of vacuum deposited SnSe films

Tin selenide (SnSe) thin films prepared on mica and glass substrates by vacuum sublimation technique and examined by scanning electron microscopy and transmission electron diffraction techniques showed epitaxial and polycrystalline nature respectively irrespective of substrate temperature. Grain size of the films deposited on glass substrate increased with increase in substrate temperature.     

Evaluation of antilock braking system with an integrated model of full vehicle system dynamics

Antilock braking system (ABS), traction control system, etc. are used in modern automobiles for enhanced safety and reliability. Autonomous ABS system can take over the traction control of the vehicle either completely or partially. An antilock braking system using an on–off control strategy to maintain the wheel slip within a predefined range is studied here. The controller design needs integration with the vehicle dynamics model. A single wheel or a bicycle vehicle model considers only constant normal loading on the wheels. On the other hand, a four wheel vehicle model that accounts for dynamic normal loading on the wheels and generates correct lateral forces is suitable for reliable brake system design. This paper describes an integrated vehicle braking system dynamics and control modeling procedure for a four wheel vehicle. The vehicle system comprises several energy domains. The interdisciplinary modeling technique called bond graph is used to integrate models in different energy domains and control systems. The bond graph model of the integrated vehicle dynamic system is developed in a modular and hierarchical modeling environment and is simulated to evaluate the performance of the ABS system under various operating conditions.     

Organomodified montmorillonite as filler in natural and synthetic rubber

The filler action of dodecylamine (12C) intercalated montmorillonite (MNT) referred to as organomodified montmorillonite (12C‐MNT) up to 4 wt % on natural rubber (NR) and styrene butadiene rubber (SBR) was studied and findings were compared with respect to the unmodified Na‐MNT. X‐ray analysis was used to calculate the interchain separation (R and R′), degree of crystallinity (X_c), and distortion factor (k). It is noted that R and R′ showed the opposite trend, whereas X_c as well as k showed overall increasing trend with an increasing amount of 12C‐MNT on both NR and SBR. For Na‐MNT (1 wt %) filled NR and SBR, the corresponding magnitude of R and R ′ and X_c showed nearly no change, whereas k_c increased significantly. The crosslinking density (v_c) does not show any significant changes in NR, whereas for SBR, it increases with increasing 12C‐MNT as filler. Interestingly, in the case of 1 wt % pure Na‐MNT used as filler for both NR and SBR, v_c was lower compared to the virgin rubbers. Both swelling index (s_i) and sol fraction (Q) do not show any significant variation for NR composites, whereas these decrease for SBR composites with increasing concentration of 12C‐MNT filler. On the contrary, NR and SBR with 1 wt % of Na‐MNT filler show greater magnitude of s_i and Q corresponding to the pure ones. Measurements of mechanical properties showed a significant increase in tensile strength and elongation at break for NR‐12C‐MNT (4 wt %) when compared with either virgin NR. In addition, modulus at the elongation at 100 and 200% in general increases with increasing loading of 12C‐MNT filler in NR. Similar observations were also noted in the case of SBR. Interestingly, when only pure Na‐MNT is used as filler, the strength of NR and SBR decreases drastically. Scanning electron microscopic studies were also to used support the mechanical behavior of NR‐12MNT and SBR‐12CMNT composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3583–3592, 2004     

High impedance fault detection in power distribution networks using time?frequency transform and probabilistic neural network

An intelligent approach for high impedance fault (HIF) detection in power distribution feeders using advanced signal-processing techniques such as time-time and time-frequency transforms combined with neural network is presented. As the detection of HIFs is generally difficult by the conventional over-current relays, both time and frequency information are required to be extracted to detect and classify HIF from no fault (NF). In the proposed approach, S- and TT-transforms are used to extract time-frequency and time-time distributions of the HIF and NF signals, respectively. The features extracted using S- and TT-transforms are used to train and test the probabilistic neural network (PNN) for an accurate classification of HIF from NF. A qualitative comparison is made between the HIF classification results obtained from feed forward neural network and PNN with same features as inputs. As the combined signal-processing techniques and PNN take one cycle for HIF identification from the fault inception, the proposed approach was found to be the most suitable for HIF classification in power distribution networks with wide variations in operating conditions.     

A review of nanofluid preparation,stability, and thermo‐physical properties

This paper represents a comprehensive review on the preparation and stability of nanofluid, the convective heat transfer coefficient and different thermo‐physical properties such as thermal conductivity, specific heat capacity, viscosity, and so on. Here, for each thermo‐physical property, measurement methods, enhancement mechanisms, and criticisms of different studies are also presented. However, based on the available literature, it is concluded that a nanofluid has, in general, better thermo‐physical properties even at a very low particle concentration (typically 1% or less) than conventional heat transfer fluids. The only drawback is high viscosity which leads to a higher pressure drop. At a very low particle concentration, this drawback can be minimized. Three tables are provided for three thermo‐physical properties namely thermal conductivity, specific heat capacity, and viscosity, which can be used as a ready reference for calculating the nanofluid properties.     

Large-Area Si Solar Cells Based on Molybdenum Oxide Hole Selective Contacts

Silicon - Carrier selective contacts based heterojunction Si solar cells are an emerging photovoltaic technology. This paper reports the fabrication of large area Si solar cells based on molybdenum...     

Graft copolymerization with new class of acidic peroxo salts as initiators. I. Grafting of acrylamide onto cotton–cellulose using potassium monopersulfate,catalyzed by co(II)

Graft copolymerization of acrylamide (AM) onto cotton–cellulose has been studied using a new class of acidic peroxo-salt “potassium monopersulfate” as initiator catalyzed by Co(II). It is observed that the graft yield is influenced by the reaction time, temperature, and concentrations of the monomer, catalyst, initiator, at fixed weight of the polymer. Maximum graft yield (30.8%) is obtained at 40°C under nitrogen atmosphere for the concentrations of monomer 1.2M; initiator 4.83 × 10^?3M; Co(II) 5 × 10^?4M for 4 h of reaction time. The graft copolymers after proper purification have been subjected to IR analysis, testing of their water-retention properties, rot resistance, tensile properties, and behavior towards acids and alkalies. The results of such analysis are compared with the base. Suitable mechanism for the graft copolymerization is suggested and grafting rate has been evaluated.     

Power transformer protection using S-transform with complex window and pattern recognition approach

A new approach for power transformer protection using S-transform with complex window to distinguish between inrush current and internal fault is presented. The S-transform with complex window is used to extract patterns of transient current samples during inrush and faults. S-transform is a very powerful tool for non-stationary signal analysis giving the information of transient currents both in time and in frequency domains. The spectral energy is calculated for inrush and internal faults and an energy index is found out to distinguish between inrush magnetising current and internal faults. The simulation results and the results obtained using real-time data from a transformer in the laboratory environment indicate the robustness of the proposed technique