一种高效的OpenFlow流表存储与查找实现方法

目前Open Flow流表的存储与查找还面临一些挑战,如流表项匹配字段数量的不断增加、流表规模的爆炸性增长以及实现Open Flow硬件交换机的端口线速处理更加困难.针对这些问题,本文提出了一种高效的Open Flow流表存储与查找实现方法.该方法将Open Flow流表划分成多个规模更小、匹配字段更少的子流表,进一步根据字段匹配类型将子流表切分成多个字段,不同字段采用不同的算法和硬件进行存储和查找,得到字段匹配结果后再结合汇总表查找从而得到子流表的匹配结果.通过划分流表与切分子流表来压缩流表存储空间,根据子流表的查找选择和子流表内部查找优化来减少查找过程中硬件资源开销.通过大量模拟实验表明,该存储与查找方法能够压缩50%左右的存储空间,且可以有效减少流表项匹配过程中80%硬件资源的消耗.

CO_2 laser-micro plasma arc hybrid welding for galvanized steel sheets

A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal, which is steel. In the autogenous laser welding, the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters and blow holes on the weld surface and porosity inside the welds. The laser-arc hybrid welding was suggested as an alternative method for the laser lap welding because the arc can preheat or post-beat the weldment according to the arrangement of the laser beam and the arc. CO2 laser-micro plasma hybrid welding was applied to the lap welding of zinc-coated steel with zero-gap. The relationships among the weld quality and process parameters of the laser-arc arrangement, and the laser-arc interspacing distance and arc current were investigated using a full-factorial experimental design. The effect of laser-arc arrangement is dominant because the leading plasma arc partially melts the upper steel sheets and vaporizes or oxidizes the coated zinc on the lapped surfaces. Compared with the result from the laser-TIG hybrid welding, the heat input from arc can be reduced by 40%.

Stability and Drag Reduction in Transient Channel Flow of Fibre Suspension

Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory. The modified stability equation was obtained based on the slender-body theory and natural closure approximation. Results of the stability analysis show attenuating effects of fibre additives to the flow instability. For the cases leading to transition, drag reduction rate increases with the characteristic parameter H of fibres. The mechanism of drag reduction by fibres is revealed through the variation of velocity profile and the decrease of wall shear stress. The theoretical results are qualitatively consistent with some typical experiments.

Band gap modulation of nanostructured WO_(3) nanoplate film by Ti doping for enhanced photoelectrochemical performance

Despite being a promising photoanode material for water splitting,WO_(3) has low conductivity,high onset potential,and sluggish water oxidation kinetics.In this study,we designed Ti-doped WO_(3) nanoplate arrays on fluoride-doped tin oxide by a seed-free hydrothermal method,and the effects of doping on the photoelectrochemical performance were investigated.The optimal Ti-doped WO_(3) electrode achieved a photocurrent density of 0.53 mA/cm^(2) at 0.6 V(vs Ag/AgCl),110%higher than that of pure WO_(3) nanoplate arrays.Moreover,a significant cathodic shift in the onset potential was observed after doping.X-ray photoelectron spectroscopy valence band and ultraviolet–visible spectra revealed that the band positions of Ti-doped WO_(3) photoanodes moved upward,yielding a lower onset potential.Furthermore,electrochemical impedance spectroscopy measurements revealed that the conductivities of the WO_(3) photoanodes improved after doping,because of the rapid separation of photo-generated charge carriers.Thus,we report a new design route toward efficient and low-cost photoanodes for photoelectrochemical applications.

Synergistic effects of CuO and Au nanodomains on Cu_2O cubes for improving photocatalytic activity and stability

Cu2O is a promising photocatalyst,but it suffers from poor photocatalytic activity and stability,especially for Cu2O cubes.Herein,we report the deposition of CuO and Au nanodomains on Cu2O cubes to form dual surface heterostructures(HCs)to improve photocatalytic activity and stability.The apparent quantum efficiency of Au/CuO/Cu2O HCs was ca.123 times that of pristine Cu2O.In addition,the Au/CuO/Cu2O HCs maintained nearly 80%of its original activity after eight cycles in contrast to five cycles for the Au/Cu2O material.Therefore,CuO and Au domains greatly improved the photocatalytic activity and stability of the Cu2O cubes due to the synergistic effect of the HCs.

Silane coupling agent treated copper foil as a current collector for silicon anode

Since the volume variation of silicon particles during cycling,the binding spots between Cu current collector and silicon anode raised to be one of the critical binding problems.In this work,an amino-modified Cu current collector(Cu^(*))is fabricated to tackle this issue.The amino groups on Cu^(*)surface increase its hydrophilicity,which is conducive to the curing process of aqueous slurry on its surface.Meanwhile,these amino groups can form abundant amide bonds with carboxyl groups from the adopted polyacrylic acid(PAA)binder.The combined action composed of the covalent bond and mechanical interlocking could reduce the contact loss inside the electrode.However,high concentration silane coupling agent treatment will weaken the surface roughness of Cu^(*)and weaken mechanical interlocking.What is more,the insulation of silane coupling agent reduces the conductivity of Cu and increases the impedance of battery.Considering the effect of silane coupling agent comprehensively,electrochemical performance of Cu^(*)-0.05%is best.

Gas-Phase Deposited Plasmonic Nanoparticles Supported on 3D-Graphene/Nickel Foam for Highly SERS Detection

In this work, we proposed a novel three-dimensional (3D) plasmonic nanostructure based on porous graphene/nickel foam (GNF) and gas-phase deposited Ag nanoparticles (NPs). Ag NPs with high density were directly deposited on the surface of 3D GNF by performing a novel cluster beam deposition approach. In comparison with traditional Ag substrate (SiO2/Ag), such hot-spots enriched 3D nanostructure showed extremely high electromag-netic field enhancement under incident light irradiation which could be used as a sensitive chemical sensor based on surface enhanced Raman scattering (SERS). The experimental results demonstrated that the proposed nanostructure showed superior SERS performance in terms of Raman signal reproducibility and sensitivity for the probe molecules. 3D full-wave simulation showed that the enhanced SERS performance in this 3D hierarchical plasmonic nanostructure was mainly obtained from the hot-spots between Ag NPs and the near-field coupling between Ag NPs and GNF sca olds. This work can provide a novel assembled SERS substrate as a SERS-based chemical sensor in practical applications.

Simulation of Wave Impact on a Horizontal Deck Based on SPH Method

A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.

Computational modeling of free-surface slurry flow problems using particle simulation method

The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is to treat granular or other materials as an assembly of many particles.Compared with the continuum-mechanics-based numerical methods such as the finite element and finite volume methods,the movement of each particle is accurately described in the particle simulation method so that the free surface of a slurry flow problem can be automatically obtained.The major advantage of using the particle simulation method is that only a simple numerical algorithm is needed to solve the governing equation of a particle simulation system.For the purpose of illustrating how to use the particle simulation method to solve free-surface flow problems,three examples involving slurry flow on three different types of river beds have been considered.The related particle simulation results obtained from these three examples have demonstrated that:1) The particle simulation method is a promising and useful method for solving free-surface flow problems encountered in both the scientific and engineering fields;2) The shape and irregular roughness of a river bed can have a significant effect on the free surface morphologies of slurry flow when it passes through the river bed.

Numerical Simulation of Dam Breaking Using Smoothed Particle Hydrodynamics and Viscosity Behavior

Smoothed particle hydrodynamics (SPH) is a Lagrangian meshless particle method. It is one of the best method for simulating violent free surface flows in fluids and solving large fluid deformations. Dam breaking is a typical example of these problems. The basis of SPH was reviewed, including some techniques for governing equation resolution, such as the stepping method and the boundary handling method. Then numerical results of a dam breaking simulation were discussed, and the benefits of concepts like artificial viscosity and position correction were analyzed in detail. When compared with dam breaking simulated by the volume of fluid (VOF) method, the wave profile generated by SPH had good agreement, but the pressure had only reasonable agreement. Improving pressure results is clearly an important next step for research.

Dual Manipulation of Ferromagnetism in Co-Doped ZnO Thin Films by Surfactant and n-Type Carriers

We present a conceptually-new approach “dual manipulation effect” using the surfactant passivation and the electron carrier doping for mediating intrinsic ferromagnetism in Codoped ZnO dilute magnetic semiconductor (DMS) thin films. The first-principles calculations show that the surface passivation by hydrogen serves as a magnetism switch for the Co-O-Co magnetic coupling at the surface of the thin film, and thus can control the spin polarization of the doped Co atoms. Meanwhile, the electron carrier doping can further function as an effective layerlike ferromagnetism mediator for the underneath layer. The dual manipulation effect sheds light on the essential magnetism origin of n-type Co:ZnO DMS thin films, and may be used as an alternative strategy for enhancing the ferromagnetism in other n-type DMS oxides thin films.

Anion Content in Surface and Subsurface Water Flows in Grassland

Grassland devoted about 90% of agricultural Irish land. Anion retention capacity of most agriculture soils is less than cation retention capacity, therefore chemical analyzed for anion （NO3 （nitrate）, CI- （chloride）, SO42 （sulphate） and HPO4 （biphosphate）） in different water flow types （overland flow, interflow and vertical flow or drainage） samples. In this work, simple equipment was used to operationally distinguish between overland flow and interflow while vertical flow collected in different depths using soil water sampler equipments. Episodes of overland flow and interflow occurred even though the site is located in the lowest rainfall in Ireland and on well-drained soil. Samples of different origin showed marked differences in their anion contents, while HPO4 concentrations were almost equal to zero in all water flow types, nitrate where relatively high in overland and interflow samples and was very high in drainage samples. No sampling was carried out below the root zone but it must be assumed that the high concentrations measured in drainage samples would constitute a threat to groundwater resources. When overland flow and interflow did occur, NO3 concentrations were usually close to or in excess of the maximum admissible concentrations for drinking water and it will be constituted a threat to inland surface water bodies.

Study on the heat transfer of cross flow in vertical upward tubes

A special device was designed to measure temperature difference in this study of heat transfer of water and oil cross flow inside vertical upward tubes. A new heat transfer correlation was obtained for cross flow. The experimental results showed that the dependence of heat transfer on Reynolds is much smaller in a narrow space than that in a wide space. It was found that the heat transfer correlation of cross flow in a narrow space is obviously different from that in a wide space, and that the heat transfer correlation obtained in a wide space may not be applicable to the cross-flow heat transfer in a narrow space. Further, the single-phase heat transfer capability of water cross flow was compared with that of oil cross flow. The experimental results showed that the average heat transfer coefficient of water is about 2～3 times that ofoil when they have the same superficial velocity.

Electrodeposition and Surface Characterization of Sulfur on Polycrystalline Platinum from Sulfide Polluted Brine

This paper investigated the electrodeposition of sulfur on polycrystalline platinum from sulfide polluted brine. Anodic polarization, potentiostatic and electrochemical impedance spectroscopy （EIS） techniques were performed. The slope of Warburg straight line in Nyquiest plot of the EIS spectra performed at 0.0 V indicates diffusion control mechanism of the electrodeposition process. At 0.5 V the Rp （determined from EIS measurements） increased rapidly with time indicating more sulfur deposition and more passivation of platinum surface. Samples subjected to potentiostatic experiments at 0.4, 0.9 and 1.0 V were investigated under Scanning Electron Microscope （SEM）. SEM images reveal the deposition of sulfur on the sample surfaces. The degree of sulfur deposit coverage and its morphology depend on both the potential and time of deposition.

Characterization of Phase Transition in Heisenberg Fluids from Density Functional Theory

The phase transition of Heisenberg fluid has been investigated with the density functional theory in mean-field approximation （MF）. The matrix of the second derivatives of the grand canonical potential Ω with respect to the particle density fluctuations and the magnetization fluctuations has been investigated and diagonalized. The smallest eigenvalue being 0 signalizes the phase instability and the related eigenvector characterizes this phase transition. We find a Curie line where the order parameter is pure magnetization and a spinodal where the order parameter is a mixture of particle density and magnetization. Along the spinodal, the character of phase instability changes continuously from predominant condensation to predominant ferromagnetic phase transition with the decrease of total density. The spinodal meets the Curie line at the critical endpoint with the reduced density p＊=pσ3=0.224 and the reduced temperature T＊ =kT/ε=1.87 （σ is the diameter of Heisenberg hard sphere and e is the coupling constant）.

Influence of Nonionic Surfactant Addition on Drag Reduction of Water Based Nanofluid in a Small Diameter Pipe

The goal of this research was to determine the impact of nonionic surfactants on drag reduction effect in water and metal oxide nanofluid. Two nonionic surfactants （Rokacet 07 and Rokanol KT） and copper（II） oxide wa- ter-based nanofluid were examined. Friction factors in a 4 mm diameter pipe for the Reynolds number between 8000 and 50000 were determined. Results showed that addition of nonionic surfactants caused the decrease of fric- tion factor in water and nanofluid. The drag reduction effect was similar in both cases. Presence of nanoparticles in the system has no great influence on drag reduction effect.

Study on Surface Properties for Non-polar Fluids with Density Functional Theory

The density functional theory, simplified by the local density approximation and mean-field approxi-mation, is applied to study the surface properties of pure non-polar fluids. A reasonable long rang correction is adopted to avoid the truncation of the potential. The perturbation theory is applied to establish the equation for the phase equilibrium, in which the hard-core chain fluid is as the reference fluid and the Yukawa potential is used as the perturbation term. Three parameters, ε/κ, d and ms, are regressed frorn the vapor-liquid equilibria, and the surface properties, including density profile, surface tension and local surface tension profile are predicted with these parameters.

Analysis of Synonymous Codon Usage Bias in 09H1N1

A novel subtype of influenza A virus 09H1N1 has rapidly spread across the world. Evolutionary analyses of this virus have revealed that 09H1N1 is a triple reassortant of segments from swine, avian and human influenza viruses. In this study, we investigated factors shaping the codon usage bias of 09H1N1 and carried out cluster analysis of 60 strains of influenza A virus from different subtypes based on their codon usage bias. We discovered that more preferentially used codons of 09H1N1 are A-ended or U-ended, and the intra-genomic codon usage bias of 09H1N1 is quite low. Base composition constraint, dinucleotide biases and translational selection are the main factors influencing the codon usage bias of 09H1N1. At the genome level, we find that the codon usage bias of 09H1N1 is similar to H1N1 (A/swine/Kansas/77778/2007H1N1), H9N2 from Asia, H1N2 from Asia and North America and H3N2 from North America. Our results provide insight for understanding the processes governing evolution, regulation of gene expression, and revealing the evolution of 09H1N1.

Effects of Precipitation on Sonic Anemometer Measurements of Turbulent Fluxes in the Atmospheric Surface Layer

Effects caused by precipitation on the measurements of three-dimensional sonic anemometer are analyzed based on a field observational experiment conducted in Maoming, Guangdong Province, China. Obvious fluctuations induced by precipitation are observed for the outputs of sonic anemometer-derived temperature and wind velocity components. A technique of turbulence spectra and cospectra normalized in the framework of similarity theory is utilized to validate the measured variables and calculated fluxes. It is found that the sensitivity of sonic anemometer-derived temperature to precipitation is significant, compared with that of the wind velocity components. The spectra of wind velocity and cospectra of momentum flux resemble the standard universal shape with the slopes of the spectra and cospectra at the inertial subrange, following the-2/3 and-4/3 power law, respectively, even under the condition of heavy rain. Contaminated by precipitation, however, the spectra of temperature and cospectra of sensible heat flux do not exhibit a universal shape and have obvious frequency loss at the inertial subrange. From the physical structure and working principle of sonic anemometer, a possible explanation is proposed to describe this difference, which is found to be related to the variations of precipitation particles. Corrections for errors of sonic anemometer-derived temperature under precipitation is needed, which is still under exploration.

The Surface Plasmons＇ Frequencies of Two Adjacent Metallic Nanospheres by Bloch-Jensen Hydrodynamical Model

The wave guides and optical fibers have long been known to transmit light and electromagnetic fields in large dimensions. Recently, surface plasmons, which are collective plasma oscillations of valence electrons at metal surfaces, have been introduced as an entity that is able to guide light on the surfaces of the metal and to concentrate light in subwavelength volumes. It has been found that periodic array of metallic nanospheres, could be able to enhance the light transmission, and guiding light at nanoscale. The coupling between two nanoparticles in these devices is very important. The Bloch-Jensen hydrodynamical method has been used for computing surface plasmons＇ frequencies of a single metallic nanosphere. It contains the entire pole spectrum automatically, so it is more exactly than the other computational methods. In this research, we have computed the surface plasmons＇ frequencies of two adjacent nanospheres by Bloch-Jensen hydrodynamical model for the first time. The results show that there are two modes for this system, which depend explicitly on interparticle spacing. In addition, we have shown that the excitation modes yield to a single mode of a nanoparticle as the interparticle spacing increases.