Strain-rate effects on concrete behavior

In this paper, a previously developed meso-scale model for concrete, called the Confinement Shear Lattice (CSL) model, is extended in order to include the effect of loading rate on concrete strength and fracturing behavior. The rate dependence of concrete behavior is assumed to be caused by two different physical mechanisms. The first is a dependence of the fracture process on the rate of crack opening, and the second is the viscoelastic deformation of the intact (unfractured) cement paste. In this study, the first mechanism is described by the activation energy theory applied to the ruptures occurring along the crack surfaces, whereas the second mechanism is modeled by the Microprestress-Solidification theory. The developed model is calibrated and validated on the basis of experimental data gathered from the literature.     

Lattice Discrete Particle Model (LDPM) for failure behavior of concrete. I: Theory

This paper deals with the formulation, calibration, and validation of the Lattice Discrete Particle Model (LDPM) suitable for the simulation of the failure behavior of concrete. LDPM simulates concrete at the meso-scale considered to be the length scale of coarse aggregate pieces. LDPM is formulated in the framework of discrete models for which the unknown displacement field is not continuous but only defined at a finite number of points representing the center of aggregate particles. Size and distribution of the particles are obtained according to the actual aggregate size distribution of concrete. Discrete compatibility and equilibrium equations are used to formulate the governing equations of the LDPM computational framework. Particle contact behavior represents the mechanical interaction among adjacent aggregate particles through the embedding mortar. Such interaction is governed by meso-scale constitutive equations simulating meso-scale tensile fracturing with strain-softening, cohesive and frictional shearing, and nonlinear compressive behavior with strain-hardening. The present, Part I, of this two-part study deals with model formulation leaving model calibration and validation to the subsequent Part II.     

Modeling of thin-film slurry photocatalytic reactors affected by radiation scattering

Photocatalytic oxidation over titanium dioxide is a "green" sustainable process for treatment and purification of water and wastewater. A dimensionless model for steady-state, continuous flow, thin-film, slurry (TFS) photocatalytic reactors for water purification using solar radiation and UV lamps is presented and validated. The model is applicable to TFS flat plate and annular photoreactors of (a) falling film or (b) double-skin designs, operating with three ideal flows: (1) falling film laminar flow (FFLF), (2) plug flow (PF) and (3) slitflow (SF). Model parameters can be estimated easily from real systems, and solutions can be obtained with modest computational efforts. A modified two-flux absorption-scattering model models the radiation field in the photoreactor. Model simulations show that at a scattering albedo higher than 0.3, radiation scattering can significantly affect conversions obtained at different values of optical thickness. However, at lower values, the effect of scattering on conversions is negligible. The conversions with the idealized flow systems follow the sequence FFLF > PF > SF. SF operation should always be avoided. The model estimates the optimum value of optical thickness that maximizes conversion in a photocatalytic reactor. Optimal design of TFS photocatalytic reactors using the photocatalyst TiO2 Degussa P25 requires an optical thickness in the range from 1.8 to 3.4 depending on flow conditions and reaction kinetics.     

Novel JPEG 2000 Compliant DWT and IWT VLSI Implementations

This paper proposes two JPEG 2000 compliant architectures: one for DWT (Discrete Wavelet Transform) and one for IWT (Integer Wavelet Transform) implementation. First of all some theoretical issues about DWT and IWT are discussed, then, starting from transforms characteristics, the architectures are presented showing both performance and cost. In the literature many DWT architectures have been proposed; our implementation is a new architecture that computes the DWT using filters of interest for the forthcoming JPEG 2000 standard. Moreover, we propose a Lifting Scheme based architecture for IWT, JPEG 2000 compliant too. The proposed architectures are able to support real-time streams: the DWT one, which is made of 20,000 cells, with an input throughput of 160 Msamples per second and a clock frequency of 160 MHz, the IWT one, consisting of 50,000 cells, with an input throughput of 4.5 Msamples per second and an internal clock frequency of 108 MHz.     

Catalytic MTO-based C–H insertion reactions of hydrogen peroxide: an investigation on the polymeric support role in heterogeneous conditions

Polymer-supported methyltrioxorhenium (MTO) compounds are shown to act as efficient and selective catalysts for the oxy-functionalization of C–H bonds in representative hydrocarbon derivatives (leading to the corresponding alcohols or ketones), using H₂O₂ as oxidant. The different supports used for the heterogenation of MTO, such as poly(4-vinylpyridine), poly(4-vinylpyridine)-N-oxide and polystyrene resins, all showed different catalytic behaviour in terms of substrate conversion and product yield, depending on the experimental conditions used. It is noteworthy that the novel heterogeneous catalysts were found to be stable, it being possible to effect their recover and recycle at least five times without appreciable loss of activity.     

用于无刷电机旋转测量的无传感器型控制

引言在家用电器、供暖、通风、空调)和汽车应用中,DC无刷电机及其驱动器的使用率越来越高。造成这种现象的原因是其所拥有的高效、可靠、紧凑、低维护等级以及低噪声等优点,而这些都将转化为成本的节省。家用电器常常运用传统技术,比如带有起动电容的AC磁阻单相电机和通用式电机。所有这些解决方案采用AC供电方式,工作速度都是恒定不变的,而且并未关注效率。如今,客户所提出的要求越来越多,他们渴望拥有改良型功率分配方案、更加优越的性能以及更低的噪声电平:传统技术的局限性正日益凸显出来。同时,市场竞争对能量-效率比提出了新的更高…     

Monitoring food quality by microfluidic electrophoresis, gas chromatography, and mass spectrometry techniques: effects of aquaculture on the sea bass (Dicentrarchus labrax)

Monitoring food quality is a critical task for analytical chemistry and an important way to preserve human health. Fish is a valuable source of highly digestible proteins and contains large amounts of polyunsaturated fatty acids and fat-soluble vitamins. Since the world's wild fish stocks are limited, farmed fish is nowadays proposed as an alternative to consumers. It is now emerging that the fish muscle protein content is assuming great importance from an aquaculture perspective. Many data have been collected on the physiology and biochemistry of fish muscle, but few proteomic studies are available on farmed fish. Application of proteomics to aquaculture may play a key role in the development of new farming strategies. In this paper, a proteomic approach based on SDS-PAGE separation of proteins, in situ protein hydrolysis, de novo sequencing of peptides by MALDI and ESI MS(2), protein identification, and relative quantitation of protein by denaturing capillary electrophoresis was coupled with the determination of fatty acids and metal ions content by GM-MS and ICPMS in farmed and wild sea bass filet. Our results show that aquaculture could induce significant chemical and biochemical differences in fish muscle that may have an impact on food quality.     

Interferential lithography of 1D thin metallic sinusoidal gratings: Accurate control of the profile for azimuthal angular dependent plasmonic effects and applications

Nonlinear processes involved in the manufacture of nominally sinusoidal surface relief diffraction gratings generated by interference lithography can introduce distortions into the profile of these surfaces. Such distortions may dramatically affect both the specular reflectivity and diffracted efficiencies from such a surface [H. Raether, Phys. Thin Film 9 (1977) 145–261]. We shall consider in particular the case of metallic gratings used to investigate plasmonic effects that can be engineered for bio-sensing applications. To investigate these effects, interference lithography (IL) has been used for the generation of profile controlled sinusoidal plasmonic crystals. IL exposure contrast study has been performed to control the amplitude oscillation and the surface roughness quality. Bi-metallic layer of silver and gold have been systematically deposited with different film thicknesses. A comprehensive numerical model that studies the optical coupling to surface plasmon polaritons on Ag/Au gratings has been undertaken for the simulation of the reflectivity and azimuthal angle dependence [Z. Chen, I.R. Hooper, J.R. Sambles, J. Opt. A: Pure Appl. Opt. 10 (1) (2008) 015007]. This computation illustrates the sensitivity of individual features to specific harmonic components of the surface, for surface plasmon resonances recorded in both the zeroth and higher diffracted orders. The roughness surface control after development and after bi-metallic evaporation strongly contributes to tighten the width of the reflectivity peak. Optimization process has shown that for an Ag (37 nm) and Au (7 nm) metallic bilayer, a semi-amplitude of 20 nm provides the best reflectivity.