Properties of chemically treated natural amorphous silica fibers as polyurethane reinforcement

A novel kind of short natural fiber obtained from mineral resources, which consists mainly of pure amorphous SiO₂, was chemically modified with aminosilane to improve its interfacial adhesion in polyurethane composites. The effect of the treatment as well as the aspect ratio of the fibers on the mechanical properties of the composite were evaluated and compared with properties obtained with glass fibers composites, which are commonly used in industry. The results obtained show that these natural fibers are potential candidates for the substitution of glass fibers as a reinforcement phase in polymer composites, since the mechanical properties obtained were in all cases equal or superior to the ones obtained with commercial glass fibers. POLYM. COMPOS. 27:582–590, 2006. © 2006 Society of Plastics Engineers.     

High-feed turning of AISI D2 tool steel using multi-radii tool inserts: Tool life,material removed,and workpiece surface integrity evaluation

Multi-radii tool inserts offer novel configuration that comprises of multiple radii at tool nose. A review of the available literature indicates that there exists a need for experimental investigation on certain key machining characteristics of such tools. This paper reports on tool wear/life, material removed, and workpiece surface roughness when multi-radii mixed alumina TiN coated tool inserts are employed for turning D2 steel. Inserts of three different nose radii (0.40, 0.80, 1.20?mm) at six levels of feed rates (ranging from 0.157 to 0.562?mm/rev) are used. Results show that flank wear is the dominant wear mode with catastrophic tool failure occurring at highest nose radius (1.20?mm) and feed rate (0.562?mm/rev) combination. Also, there is ～59% reduction in tool life accompanied by ～62% increase in quantity of material removed as the feed rate increases from 0.157 to 0.562?mm/rev at maximum nose radius (1.20?mm). Feed rate is found to be statistically significant factor for all three responses considered herein at 95% confidence level. Surface integrity assessment at maximum feed rate reveals presence of a strain hardened layer extending to the depth of 150?µm below the machined surface without any observance of white layer for all the tool conditions and nose radius.     

Hydrogen treated TiO2 nanoparticles onto FTO glass as photoanode for dye-sensitized solar cells with remarkably enhanced performance

Hydrogen treatment is a facile and efficient approach for the enhancement in the functioning of TiO₂ nanoparticles for dye-sensitized solar cells (DSSC). In this work, TiO₂ nanoparticles have been synthesized in the hydrogen environment followed by the deposition onto FTO glass substrates with various film thickness as photoanodes for DSSC. The synthesized hydrogen treated TiO₂ nanoparticles based photoanodes have showed significantly improved photocurrent in the resulting fabricated devices. SEM and TEM analyses have confirmed the particle size and morphology of TiO₂ nanoparticles at various magnifications. The crystalline structure and phase identification were studied by XRD analysis and Raman spectroscopic measurements. The UV–Vis spectroscopy analysis was carried out to find the response of samples for ultraviolet and visible light. The current-voltage measurements have confirmed the improvement of photocurrent that is principally due to improved photo-activity of hydrogen treated TiO₂ nanoparticles. Moreover, hydrogen treated TiO₂ nanoparticles-based photoanode with the film thickness of 11.65 μm has remarkably enhanced power conversion efficiency of 6.05% in DSSCs. The ability of highly photoactive hydrogen treated TiO₂ nanoparticles will provide the new openings in different fields that include photo-electrochemical water splitting and in many other applications.     

Perspectives on development: why does studying information and communication technology for development (ICT4D) matter?

ABSTRACT

The concept of development has been used by scholars and practitioners to demonstrate changes for the better in the lives of individuals, communities, nations and regions. Historically, the practice of development has been associated with interventions and categorizations that have had the opposite effect in countries and regions deemed to be developing. Current notions of development predicated on respect for individual rights, human freedoms, environmental sustainability, health and well-being and education have been more successful in achieving improvements in the lives of people. Yet, historic notions of development persist and continue to drive failing projects. This editorial explores the historical notions of development that persist to this day and offers a view of contemporary perspectives on development. As a growing set of development interventions and papers in this issue involve Information and Communication Technologies (ICTs), the question of why Information and Communication Technology for Development matters? is addressed in the light of development perspectives.     

Synthesis and characterization of a series of cross-linked polyamines for removal of Erichrome Black T from aqueous solution

A new series of polymers comprising four terpolymers was synthesized via Mannich polycondensation of benzene-1,4-diamine, formaldehyde and piperazine by varying the benzene-1,4-diamine and piperazine ratio. The new polyamines (labeled Dipip) were characterized using 13C solid-state NMR, FT-IR, TGA, DSC, XRD, SEM and EDX. The adsorptive performances of the synthesized polymers for Erichrome Black T (EBT) uptake from aqueous solution were investigated under batch process. Equilibrium, kinetic, and thermo-dynamic studies were conducted to determine the influence of different operational parameters of the adsorption process. The two most promising polymers among the series show an excellent EBT removal efficiency of～100％and～95％with high adsorption capacities of 775 mg·g- 1 and 917 mg·g- 1, respectively at a meager dosage of 5 mg. The sorption of EBT on the polymers was well described by Redlich-Peterson&Langmuir model while the kinetic studies indicate that pseudo-second order model was followed. For the thermodynamic studies, the negativeΔG and positiveΔH values obtained suggest a spontaneity of the sorption process which was endothermic in nature. The results of reusability test of the resins were promising even at the fourth cycle, showcasing the potentials of the new polymers in dyes contaminated water treatment.     

Effect of helium xenon as working fluid on centrifugal compressor of power conversion unit of closed Brayton cycle power plant

Closed Brayton cycle (CBC) having single-shaft, centrifugal type compressor is considered as an efficient energy-conversion option associated for gas-cooled reactor (GCR) heat source. In terrestrial power plants and space power systems noble gases are considered as an efficient working fluid for most of the GCR's and CBC engines. The effectiveness of various noble gases as working fluid in closed cycle power plants for the power conversion units is of imperative concern. Although pure helium is relatively difficult to compress nonetheless it is measured as the best coolants for closed Brayton cycle power plants due to its better transport properties. Due to compression properties, its use resulted in the requirement of more mass, bigger size, higher cost and relatively more dynamic problems of rotatory machines in energy conversion system. The mixture of xenon with helium up to a molecular weight of <40 g/mol resulted in an increase of the coefficient of heat transfer as well as the significant increase in the loading of the compressor. Therefore, performance analysis is conducted for a novel design of helium xenon centrifugal compressor. The performance analysis is conducted with different molecular weight mixtures of helium xenon using similarity criteria. It is concluded that the use of helium xenon 40 g/mol is the optimum choice for space applications and 15 g/mol for closed Brayton cycle terrestrial power plants.     

Robust LCMV Beamformer for Direction of Arrival Mismatch Without Beam Broadening

Wireless Personal Communications - In this work, we propose a new and efficient algorithm to mitigate the signal look direction error problem in adaptive beamforming without broadening the main...     

Novel sensing and joint beam and null steering based resource allocation for cross-tier interference mitigation in cognitive femtocell networks

Wireless Networks - Cognitive radios and femtocell networks are gaining much popularity due to the formers ability to carry out unlicensed transmission in licensed bands and the latter’s...     

Modulation of lipopolysaccharide-induced macrophage gene expression by Rhodobacter sphaeroides lipid A and SDZ 880.431

Rhodobacter sphaeroides lipid A (RsDPLA) and SDZ 880.431 (3-aza-lipid X-4-phosphate) are prototypic lipopolysaccharide (LPS) antagonists. Herein, we examined the ability of these structures to regulate murine macrophage tumor necrosis factor (TNF) secretion and LPS-inducible gene expression (tumor necrosis factor alpha [TNF-alpha], interleukin-1 beta [IL-1 beta], IP-10, type 2 TNF receptor [TNFR-2], D3, and D8 genes). We report that RsDPLA alone (> 1 microgram/ml) induced low levels of TNF-alpha secretion and a selective pattern of gene expression in peritoneal exudate macrophages; SDZ 880.431 alone was completely inactive. When LPS was present at a low concentration (1 ng/ml), RsDPLA and SDZ 880.431 blocked TNF secretion and gene induction in a concentration-dependent fashion. In general, gene induction was measurably reduced by 10 to 30 ng of RsDPLA per ml or 300 ng of SDZ 880.431 per ml, but inhibition could be uniformly overridden by increasing the concentration of LPS. Although induction of all six genes by LPS was suppressed by either inhibitor, effective inhibitor concentrations depended on the gene of interest. Induction of TNFR-2 by LPS was relatively resistant to inhibition by RsDPLA, and induction of TNFR-2 and D3 was relatively resistant to inhibition by SDZ 880.431. When LPS was present at > or = 100 ng/ml, correspondingly high concentrations (> or = 20 micrograms/ml) of either inhibitor influenced gene expression in a bidirectional manner. Under these conditions, LPS-induced expression of IP-10, D3, and D8 was suppressed regardless of the LPS concentration used (concentrations tested up to 50 micrograms/ml), while expression of TNF-alpha mRNA was enhanced about fourfold. In toto, RsDPLA and SDZ 880.431, when present at low concentrations, act in a manner consistent with competitive inhibition of LPS, while at higher concentrations, these structures inhibit certain LPS responses noncompetitively and synergize with LPS for other responses.     

GSM signalling in prioritised LEO satellite environment

The authors discuss a number of issues concerned with the functionally efficient integration of GSM signalling and services with a low-earth orbiting (LEO) mobile communication satellite system. Modified GSM signalling procedures are introduced which provide prioritised access and call setup, and reduced call setup delays