Synthesis and characterization of MWCNT impregnated with different loadings of SnO2 nanoparticles for hydrogen storage applications

Multi-walled carbon nanotubes (MWCNTs) loaded with different wt % of tin oxide (MWCNT: SnO₂) nanocomposites have been synthesized by impregnation method and their hydrogen uptake capacity is investigated. The hydrogen storage capacity of MWCNT: SnO₂ (3 wt %), MWCNT: SnO₂ (5 wt %), MWCNT: SnO₂ (7 wt %) and MWCNT: SnO₂ (9 wt %) composites is found to be 2.03, 1.95, 0.94 and 1.59 wt % respectively. The enhanced hydrogen storage capacity is due to SnOC bond formation and summative adsorption of hydrogen by MWCNT and SnO₂ nanoparticles. Moreover, physical/chemical properties of composites are examined by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, thermogravimetric and Raman analyses. Hydrogen adsorption and desorption behavior of the composites are analyzed using Raman and thermogravimetric analyses. The stored hydrogen is desorbed in the temperature range of 183 ?C-536 °C.     

Characterization and hydrogen storage properties of SnO2 functionalized MWCNT nanocomposites

Structural, spectral, morphological, thermal and hydrogen storage properties of the multi-walled carbon nanotubes functionalized with SnO₂ particles (MWCNT/SnO₂) heat treated at 300, 350 and 400 °C in air were systematically investigated. X-ray diffraction from (110), (101) and (211) planes of SnO₂, (002) plane of MWCNT and shift towards higher angle confirmed the formation of composites. XPS, Raman, FTIR and TGA analyses revealed that C–O bond on the surface of MWCNT acts as the nucleation sites for SnO₂ which resulted in a strong interaction between MWCNT and SnO₂. Presence of C, Sn and O was confirmed by EDX and XPS analyses. Hydrogen adsorption was carried out using hydrogenation set-up and H₂ adsorption/desorption behavior of the composites were studied employing Raman and thermogravimetric analyses. Size, morphology and interaction between MWCNT and SnO₂ were impacted significantly by the heat treatment which resulted in high hydrogen storage capacity of 2.13 and 2.62 wt % for 15 and 30 min hydrogenation time for the nanocomposite heat treated at 400 °C.     

Friction Factors for Spatially Varied Flow with Increasing Discharge

This paper describes an experimental investigation of how friction factors change for spatially varied flow in sloping channels receiving lateral inflow. The results are compared with those of Beij in 1934, and it is concluded that uniform flow resistance coefficients are not always appropriate for spatially varied flow. Moreover, the common technique of assuming a constant friction factor over the entire length of the channel has been found to have little theoretical justification. The method of Keulegan in 1952 for calculating friction factors in spatially varied flow gives a better estimate, but does not explicitly take account of the lateral inflow rate or velocity. Beij’s 1934 experimental data, which was used by Keulegan does not show a systematic variation of friction factor with lateral inflow rate for a constant Reynolds number although this may be due to the low flowrates used. The results of the present study indicate that the friction factor increases with lateral inflow rate for a constant Reynolds number in the experiments that included subcritical and supercritical flow conditions. A method for calculating friction factors which allows for lateral inflow is presented as a precursor to the development of a general method of evaluating friction factors for spatially varied flow with increasing discharge.     

Dependable communication synthesis for distributed embedded systems

Embedded control applications such as drive-by-wire in cars require dependable interaction between various sensors, processors, and actuators. This paper addresses the design of low-cost communication networks guaranteeing to meet both the performance and fault-tolerance requirements of such distributed applications. We develop a fault-tolerant allocation and scheduling method, which maps messages onto a low-cost multiple-bus system to ensure predictable inter-processor communication. The proposed method targets time-division multiple access (TDMA) communication protocols, and is applicable to protocols such as FlexRay and TTP which have recently emerged as possible networking standards for embedded systems such as automobile controllers. Finally, we present a case study involving some advanced automotive control applications to show that our approach uses the available network bandwidth efficiently to guarantee message deadlines.     

Nanodimensional organostannoxane molecular assemblies

Organooxotin cages, clusters, and coordination polymers containing [Sn 2(mu-O)], [Sn 2(mu-OH)], [Sn 2(mu-O) 2], [Sn 2(mu-OH) 2], and [Sn 3(mu 3-O)(mu-OR) 3] building blocks have been assembled by the reactions of organotin precursors with phosphonic, phosphinic, carboxylic, or sulfonic acids. Various synthetic methodologies including Sn-C bond cleavage reactions and solventless procedures have been utilized to generate several nanodimensional organostannoxane assemblies. The synthesis, structure, and structural interrelationship of these diverse organostannoxane compounds are discussed. The synthetic knowledge gained to prepare specific organostannoxane structural forms in high yields has been utilized for the construction of dendrimer-like molecules. These contain a central stannoxane core and a functional periphery. The functional periphery can be readily modulated to assemble photoactive, electroactive, or multisite coordinating molecules. The synthesis, structure, and potential uses of these compounds are discussed.     

Efficient Single-Stage Bridgeless AC to DC Converter Using Grey Wolf Optimization

Bridgeless single-stage converters are used for efficient (alternative current) AC-(direct current) DC conversion. These converters control generators, like electromagnetic meso- and micro-scale generators with low voltage. Power factor correction helps increase the factor of the power supply. The main advantage of the power factor is it shapes the input current for increasing the real power of the AC supply. In this paper, a two-switch bridgeless rectifier topology is designed with a power factor correction capability. For the proposed converter topology to have good power quality parameters, the closed loop scheme, which uses the grey wolf optimization (GWO) algorithm, is implemented. The successes of GWO encourage this research to implement GWO in the topology. The performance of the proposed topology is analyzed under different load conditions. Simulation is carried out using the MATLAB/Simulink environment, and the results are compared with those of conventional (proportional integral derivative) PID and (particle swarm optimization) PSO controllers. To validate the simulation results, a 350-W hardware prototype is implemented, and the voltage ripple, efficiency, and power factor under different load conditions are analyzed and tabulated. The comparative study clearly indicates that the proposed converter topology with a closed loop control scheme using the GWO algorithm improves the power factor to 0.9732 and reduces the voltage ripple to 0.12% with a conversion efficiency of 98.25%.     

Thermal and toughness property studies on a polybenzimidazole‐modified epoxy resin system

The effect of polybenzimidazole (PBI) on a silica‐filled epoxy resin matrix has been investigated. Polybenzimidazole (PBI) was incorporated into a difunctional epoxy resin matrix to the extent of 10 %, before being cured with an anhydride hardener. The effects of PBI on the curing reaction and glass transition temperature (T_g) and on the toughness of the cured epoxy matrix have been studied using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and a universal testing machine (Instron). The results indicate that the PBI modifier enhanced not only the glass transition temperature of the difunctional epoxy matrix but also its toughness, by its catalytic action. Further investigations have been carried out on the fractured specimens, using scanning electron microscopy (SEM) to support the enhanced toughness property of the epoxy matrix. © 2000 Society of Chemical Industry     

Thermophoresis and chemical reaction effects on non-Darcy mixed convective heat and mass transfer past a porous wedge with variable viscosity in the presence of suction or injection

The effects of variable viscosity, thermophoresis and non-Darcy mixed convection flow with heat and mass transfer over a porous wedge are presented here, taking into account the homogeneous chemical reaction of first order. The fluid viscosity is assumed to vary as an inverse linear function of temperature. Favorable comparison with previously published work is performed. The governing fundamental equations are approximated by a system of nonlinear ordinary differential equations and are solved numerically by using the Runge Kutta Gill and shooting methods. The steady-state velocity, temperature and concentration profiles are shown graphically. It is observed that due to the presence of first-order chemical reaction the concentration decreases with increasing values of the chemical reaction parameter. The results also showed that the particle deposition rates were strongly influenced by thermophoresis and buoyancy force, particularly for opposing flow and hot surfaces. Numerical results for the skin-friction coefficient, wall heat and mass transfer are obtained and reported graphically for various parametric conditions to show interesting aspects of the solution.     

关于环上半模的研究

半模是模的概念的推广.显然, 每个模都是一个半模,但反之不然.为了定义一个半模, 采用了半子环,它是从属于环的运算下的环的子集.利用半子环来定义半模,并且证明了半模依赖于所定义的半子环.此外,可以得证,任何一个半模,都能得到不只一个由半模所确定的半子环,还可以定义一个半模的子半模.最后,得到了一个环包含一个半子环的充分必要条件.     

Toward 18F-Labeled Theranostics: A Single Agent that Can Be Labeled with 18F, 64Cu,or 177Lu

We report a single-molecule radiotracer that can be labeled independently with ¹⁸F-fluoride or radiometals (⁶⁴Cu, ¹⁷⁷Lu) in a single step. A prostate-specific membrane antigen (PSMA)-targeting ligand, armed with both an organotrifluoroborate and a metal-chelator (DOTA), was designed to optionally afford ¹⁸F-, ⁶⁴Cu- or ¹⁷⁷Lu-labeled products that were injected into mice bearing prostate cancer (LNCaP) xenografts. PET/CT images and ex vivo biodistribution data show high, specific tumor uptake irrespective of which radionuclide is used, thereby demonstrating a new approach to combining, in a single molecule, ¹⁸F-labeling capabilities for PET imaging with radiometalation for potential imaging and therapeutic applications.