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991.
The effect of bed-load transport on flow resistance of alluvial channels with undulated bed was experimentally investigated.
The experiments were carried out in a tilting flume 250mm wide and 12.5m long with glass-sides of rectangular cross-section
and artificial dune shaped floor that was made from Plexi-glass. Steady flow of clear as against sediment-laden water with
different flow depths and velocities were studied in the experiments with a fine sand (d
50 = 0.5mm). The results indicate that the transport of fine particles (d
50 = 0.5mm) can decrease the friction factor by 22% and 24% respectively for smooth and rough beds. Increasing the bed-load
size (d
50 = 2.84 mm) can decrease the friction factor by 32% and 39% respectively for smooth and rough beds. The decrease in flow resistance
is due to filling up of the troughs of dunes. This separation zone is responsible for increasing the flow resistance. On the
upstream side of dunes condition is similar to plane bed. Presence of bed-load causes to increase the shear velocity and hence
increasing flow resistance. But decreasing in flow resistance is more and it causes to decrease the total flow resistance.
Grains saturated the troughs in the bed topography, effectively helping in smoothening of bed irregularities. 相似文献
992.
993.
Joana Tavares Dr. Ali Ouaissi Dr. Paul Kong Thoo Lin Prof. Dr. Inês Loureiro Simranjeet Kaur Nilanjan Roy Dr. Anabela Cordeiro‐da‐Silva Prof. Dr. 《ChemMedChem》2010,5(1):140-147
The NAD+‐dependent deacetylases, namely sirtuins, are involved in the regulation of a variety of biological processes such as gene silencing, DNA repair, longevity, metabolism, apoptosis, and development. An enzyme from the parasite Leishmania infantum that belongs to this family, LiSIR2RP1, is a NAD+‐dependent tubulin deacetylase and an ADP‐ribosyltransferase. This enzyme's involvement in L. infantum virulence and survival underscores its potential as a drug target. Our search for selective inhibitors of LiSIR2RP1 has led, for the first time, to the identification of the antiparasitic and anticancer bisnaphthalimidopropyl (BNIP) alkyl di‐ and triamines (IC50 values in the single‐digit micromolar range for the most potent compounds). Structure–activity studies were conducted with 12 BNIP derivatives that differ in the length of the central alkyl chain, which links the two naphthalimidopropyl moieties. The most active and selective compound is the BNIP diaminononane (BNIPDanon), with IC50 values of 5.7 and 97.4 μM against the parasite and human forms (SIRT1) of the enzyme, respectively. Furthermore, this compound is an NAD+‐competitive inhibitor that interacts differently with the parasite and human enzymes, as determined by docking analysis, which might explain its selectivity toward the parasitic enzyme. 相似文献
994.
A polydimethylsiloxane (PDMS) macroazoinitiator was synthesized from bis(hydroxyalkyl)‐terminated PDMS and 4,4′‐azobis‐4‐cyanopentanoic acid by a condensation reaction. The bifunctional macroinitiator was used for the block copolymerization of ethyl methacrylate (EMA) and 2‐(trimethylsilyloxy)ethyl methacrylate (TMSHEMA) monomers. The poly(DMS‐block‐EMA) and poly(DMS‐block‐TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and 1H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS‐block‐HEMA) and poly(DMS‐block‐EMA) copolymer film surfaces were analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS‐block‐EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS‐block‐HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase‐separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Copyright © 2010 Society of Chemical Industry 相似文献
995.
Enhancement of hydrogen evolution at cobalt-zinc deposited graphite electrode in alkaline solution 总被引:1,自引:0,他引:1
Ali DönerRamazan Solmaz Gülfeza Karda? 《International Journal of Hydrogen Energy》2011,36(13):7391-7397
Thin Co layers were electrochemically deposited on a graphite electrode at different deposition current densities and thicknesses. After determining the best deposition conditions for hydrogen evolution (deposition current density and thickness), co-deposits of Co with Zn were prepared on the graphite electrode. The binary coatings prepared on the graphite electrode (CoZn) were etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the hydrogen evolution reaction (HER). After the leaching process, a low amount of Pt was deposited onto the etched CoZn deposit in order to further improve the catalytic activity of the electrode for the HER. The HER activity is assessed by recording cathodic current-potential curves, electrochemical impedance spectroscopy (EIS) and electrolysis techniques. Chemical composition of layers after alkaline leaching was determined by energy dispersive X-ray (EDX) analysis. The surface morphologies of coatings were investigated by scanning electron microscopy (SEM). It was found that, the HER activity of coatings depends on the metal ratio of Co and Zn, deposition current density and the thickness of coatings. The alkaline leached CoZn coating has a compact and porous structure as well as good electrocatalytic activity for the HER in alkaline media. Moreover, deposition of a low amount of Pt over the CoZn can further enhance its hydrogen evolution activity. 相似文献
996.
Pooria Varahram Somayeh Mohammady Borhanuddin Mohd Ali 《Wireless Personal Communications》2013,72(2):1125-1137
Peak-to-average power ratio (PAPR) is one of the main drawbacks in orthogonal frequency division multiplexing (OFDM) systems. High PAPR forces the power amplifier to back off in order to operate in its linear region, which degrades the power efficiency of the system. Several PAPR reduction techniques have been developed, but most of them have not considered both complexity and PAPR reduction. In this paper, a novel PAPR reduction scheme based on the insertion of dummy sequences to an enhanced partial transmit sequence is proposed. By applying this scheme the PAPR performance is enhanced compared to the conventional methods while the complexity is significantly reduced. Numerical analysis is carried out with OFDM signal and QPSK modulation. 相似文献
997.
Polycarbazole (PCz) was synthesized by chemical polymerization of carbazole in acetonitrile medium using ammonium persulfate as oxidant. The selection of solvent, concentration of the monomer, composition of the solvent, polymerization time, temperature, and pH were optimized to obtain better quality and yield of the polycarbazole. The synthesized polycarbazole was characterized by various techniques such as UV–Visible, FTIR, 1H‐NMR, 13C‐NMR, COSY, NOESY, and XRD spectroscopy. The solubility of the polycarbazole was tested in various solvents. The thermodynamic stability of the polycarbazole was examined by DSC and TGA‐DTA analysis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
998.
Summary Poly(lactic acid) (PLA) was melt blended with epoxidized soybean oil (ESO) in an internal mixer and thermal, mechanical and
rheological properties of the blends were investigated by means of differential scanning calorimetry, dynamic mechanical analysis,
tensile test and small amplitude oscillatory shear rheometry. ESO lowered glass transition temperature and increased the ability
of PLA to cold crystallization. The blend exhibited improved elongation-at-break along with a plastic deformation. The plasticization
effect by ESO was also manifested by the lowering of dynamic storage modulus and viscosity in the melt state of the blends
compared with neat PLA. 相似文献
999.
Peetu Nieminen Salvador Esque Ali Muhammad Jouni Mattila Jukka Vyrynen Mikko Siuko Matti Vilenius 《Fusion Engineering and Design》2009,84(7-11):1420-1424
Department of Intelligent Hydraulics and Automation (IHA) of Tampere University of Technology has been involved in the European Fusion program since 1994 within the ITER reactor maintenance activities. In this paper we discuss the design and development of a six degrees of freedom water hydraulic manipulator with a force feedback for teleoperation tasks. The manipulator is planned to be delivered to Divertor Test Platform 2 (DTP2) during year 2008. The paper also discusses the possibility to improve the fail safe and redundant operation of the manipulator. During the design of the water hydraulic manipulator, special provisions have been made in order to meet the safety requirements such as servo valve block for redundant operation and safety vane brakes for fail safe operation. 相似文献
1000.
Carbon fiber reinforced carbon (C/C) composites are candidate materials for plasma facing components in experimental fusion reactors such as: the ITER; the JT-60 - a Tokamak fusion test facility (JAEA); and for control rods in the next generation fission reactors. Therefore, determining their thermo-mechanical properties under irradiation is essential for safe design-cum-operation of future reactors. Development of reliable models which can predict such materials’ behavior is of massive advantage against the conventional experimental verification which is hugely expensive and time-consuming. Three-dimensional finite element (FE) methods are used here for predicting Young’s modulus of two woven C/C composites where tensile tests are performed for validation. Stress distribution results indicate that a novel image-based route for FE meshes compared to a unit cell approach gives stronger agreement with experimental data. The image-based approach captures true porosity as fine microstructural details are converted from X-ray tomographic data. In comparison, the unit cell model represents idealizations of composite architecture that ignores porosities. 相似文献