Study of natural ventilation in wind tunnels and influence of the position of ventilation modules and types of grids on a modular façade system

Natural ventilation requires no energy consumption, which can constitute 25% of a mechanically ventilated building, and both shape and position of inlets and outlets ventilation openings must be properly designed for better natural ventilation performance. Wind tunnel tests are a reliable tool for the determination of the effect of natural ventilation on buildings. This paper reports on results of wind tunnel tests conducted for the evaluation of the influence of the positioning and type of grid of ventilation modules on a façade system. Three ventilation modules were positioned below the window-sill (ventilated window-sill) and three were positioned above and below the façade. Ventilation modules with grid elements positioned vertically and horizontally were tested. Wind speed measurements that considered single-sided and cross ventilation were taken inside and outside the model for the different façade configurations for the evaluation of the best performance in relation to natural ventilation. The façade system proposed is movable and interchangeable, so that the same basic model can be used for the testing of possibilities for ventilation. The results show the use of six ventilation modules positioned below the window-sill and that form a "ventilated window-sill" with a horizontal grid is the best solution regarding natural ventilation. Such a configuration has proved the grid elements of ventilation modules exert a higher influence on the results than the positioning of modules on the façade. Therefore, better conditions of natural ventilation were obtained with a thin and horizontal positioning of the elements.The authors gratefully acknowledge the financial support provided by Erasmus Mundus ISAC – Improving Skills Across Continents.info:eu-repo/semantics/publishedVersio

Canopy Characteristics and Growth Rate of Bahiagrass Monoculture and Mixtures with Rhizoma Peanut

Understanding relationships among canopy light interception (LI), canopy height and structure, and leaf area index (LAI) informs management decisions and can improve efficiency of forage-livestock systems. In a long-term experiment in Florida, USA, we assessed the LI, LAI and sward height relationships of rhizoma peanut (Arachis glabrata Benth., RP)-bahiagrass (Paspalum notatum Flügge) mixed swards compared with bahiagrass monoculture to determine whether changes in canopy structure affect herbage accumulation (HA) rate due to changes in radiation use. Treatments were arranged in a semi-factorial, split-plot design (r=4). Bahiagrass monoculture and bahiagrass-RP mixtures were whole-plot treatments. Sub-plot treatments were an undefoliated control, forage clipped to 5 cm when LAI \u3e 3, and forage clipped to 5 cm when LAI \u3e 3 and fertilized immediately after with 20 kg N ha-1. During 2021, LI, LAI and canopy height were measured weekly using a LiCOR LAI-2200 and a rising plate meter (platemeters g1000), respectively. The proportion of bahiagrass and RP in total herbage mass was determined for each treatment in July 2021. Herbage accumulation rate was calculated as HA during the regrowth period divided by days between clipping events. The relationship of LI and LAI was assessed with a negative exponential model. Relationships of cumulative LAI and sward height and days after clipping were determined using regression analysis. Incorporating RP into bahiagrass increased LI at shorter sward height compared with bahiagrass monoculture due to a greater LAI mm-1 of sward height (190-220 vs. 150-160 mm). Fertilized mixtures achieved LAI95 faster than bahiagrass monoculture, however, changes in mixture canopy structure did not result in greater radiation-use efficiency compared with fertilized bahiagrass monoculture. Herbage accumulation rate decreased for mixtures containing more than 30% RP. Application of this information can improve the efficiency of grazing systems and maximize HA of bahiagrass-RP mixtures, either under rotational or continuous stocking

Size Segregation of Granular Matter in Silo Discharges

We present an experimental study of segregation of granular matter in a quasi-two dimensional silo emptying out of an orifice. Size separation is observed when multi-sized particles are used with the larger particles found in the center of the silo in the region of fastest flow. We use imaging to study the flow inside the silo and quantitatively measure the concentration profiles of bi-disperse beads as a function of position and time. The angle of the surface is given by the angle of repose of the particles, and the flow occurs in a few layers only near the top of this inclined surface. The flowing region becomes deeper near the center of the silo and is confined to a parabolic region centered at the orifice which is approximately described by the kinematic model. The experimental evidence suggests that the segregation occurs on the surface and not in the flow deep inside the silo where velocity gradients also are present. We report the time development of the concentrations of the bi-disperse particles as a function of size ratios, flow rate, and the ratio of initial mixture. The qualitative aspects of the observed phenomena may be explained by a void filling model of segregation.Comment: 6 pages, 10 figures (gif format), postscript version at http://physics.clarku.edu/~akudrolli/nls.htm

Excitation energy transfer in light-harvesting system: Effect of initial state

The light-harvesting is a problem of long interest. It becomes active again in recent years stimulated by suggestions of quantum effects in energy transport. Recent experiments found evidence that BChla 1 and BChla 6 are the first to be excited in the Fenna-Matthews-Olson(FMO) protein, theoretical studies, however, are mostly restricted to consider the exciton in BChla 1 initially. In this paper, we study the energy transport in the FMO complex by taking different initial states into account. Optimizations are performed for the decoherence rates as to maximal transport efficiency. Dependence of the energy transfer efficiency on the initial states is given and discussed. Effects of fluctuations in the site energies and couplings are also examined.Comment: 6 pages, 6 figures, J Phys B accepte

Isothermal omega assisted alpha phase precipitation and microstructural evolution of an aged Ti-30Nb-3Fe alloy

The mechanical behavior of metastable β Ti alloys can be controlled through heat treatments. Thus, the relationship between the precipitation of α phase and the mechanical properties of these alloys is of special interest. In this work, the microstructure evolution of Ti-30Nb-3Fe alloy during aging heat treatments was evaluated using optical microscopy, scanning electron microscopy and X-ray diffraction. Moreover, Vickers hardness and elastic modulus were measured as a function of aging time. Finally, the ultimate strength and ductility of the alloy aged at 500 °C was assessed by tensile tests. In comparison to a Ti-30Nb alloy, the addition of Fe lowered the β-transus temperature, decreased the martensite start temperature to a value below room temperature, increased the precipitation temperature and reduced the dissolution temperature of ω phase, and lastly, decreased the α phase precipitation temperature. Low heating rates enabled isothermal ω phase precipitation and growth, providing favorable conditions for α phase precipitation and increasing the amount of α phase precipitates. Compared to the solution heat-treated and water-quenched condition, aging heat-treated Ti-30Nb-3Fe alloy presented higher Vickers hardness and mechanical strength, without significant loss of ductility233CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP405054/2016-588887.357955/2019-002016/24693-3The authors gratefully acknowledge the LNNano (National Nanotechnology Laboratory) at the CNPEM (National Center for Research on Energy and Materials) for allowing access to its SEM facilities. We also acknowledge the financial support of the Brazilian research funding agencies FAPESP (State of São Paulo Research Foundation) for Grant #2016/24693-3, CNPq (National Council for Scientific and Technological Development) for Grant #405054/2016-5, and CAPES/PNPD (Coordination for the Improvement of Higher Education Personnel) for Grant #88887.357955/2019-00. We thank the Brazilian Niobium Mining and Processing Company CBMM for supplying the Nb used in this stud

Spectrophotometric characterization of simple glazings for a modular façade

A large variety of transparent materials is available for uses in buildings façades and all glazing properties must be considered in their choice. Such a selection should be a careful process of evaluation and weighing of tradeoffs. The correct glazing specifications for façades can reduce energy consumption in buildings, because the heat exchange and passage of radiation into the building as light and heat occur through transparent surfaces. Therefore, glazing significantly contributes to the heat transfer between outdoor and indoor spaces, which act directly on daylighting and thermal comfort. This manuscript addresses a spectrophotometric characterization of glazings for the study of components for the design of a modular façade system based on the climate of Portugal. The study focused on results of spectrophotometric measurements of an optical behavior in different solar spectrum intervals (ultraviolet, visible and near infrared), specifically the transmittance of some types of simple glazings. The results show the percentage of transmission to spectrum intervals, which enabled the analysis (OK?) of the efficiency of the glazing regarding daylighting and correlation to the thermal performance. Indications for specifications and adequate uses based on transmission of transparent surfaces have been obtained and complemented the datasheets available from the manufactures.The authors gratefully acknowledge the financial support provided by Erasmus Mundus ISAC – Improving Skills Across Continents for this research.info:eu-repo/semantics/publishedVersio

Wet solids flow enhancement

The objective was to visualize the flow of granular materials in the silo using Nuclear Magnetic Resonance. This was done by introducing traces. Mustard seeds and poppy seeds were used as trace particles. The region sampled was a cylinder 25 mm in diameter and 40 mm in length. Eight slices containing 128 by 128 to 256 by 256 pixels were generated for each image

Traffic Equations and Granular Convection

We investigate both numerically and analytically the convective instability of granular materials by two dimensional traffic equations. In the absence of vibrations the traffic equations assume two distinctive classes of fixed bed solutions with either a spatially uniform or nonuniform density profile. The former one exists only when the function V(\rho) that monitors the relaxation of grains assumes a cut off at the closed packed density, \rho_c, with V(\rho_c)=0, while the latter one exists for any form of V. Since there is little difference between the uniform and nonuniform solution deep inside the bed, the convective instability of the bulk may be studied by focusing on the stability of the uniform solution. In the presence of vibrations, we find that the uniform solution bifurcates into a bouncing solution, which then undergoes a supercritical bifurcation to the convective instability. We determine the onset of convection as a function of control parameters and confirm this picture by solving the traffic equations numerically, which reveals bouncing solutions, two convective rolls, and four convective rolls. Further, convective patterns change as the aspect ratio changes: in a vertically long container, the rolls move toward the surface, and in a horizontally long container, the rolls move toward the walls. We compare these results with those reported previously with a different continuum model by Hayakawa, Yue and Hong[Phys. Rev. Lett. 75,2328, 1995]. Finally, we also present a derivation of the traffic equations from Enskoq equation.Comment: 34 pages, 10 figure

Wet solids flow enhancemant

WE used glass beads of different sizes as.a model system to study the flow enhancing properties of Octadecyltrichlorosilane (OTS). 0TS provides Si(CH{sub 2}){sub 17}CH{sub 3} groups that bind with the surface hydrox groups to make it hydrophobic. Experimental data showed, indeed, that surface hydrophobicity promotes the flow of wet granular materials. Mixtures of different percentage of silanized/unsilanized particles were prepared for tensile strength measurements. The tensile strength decreased as more silanized particles were added to the samples. The relationship between dimensionless tensile strength and void fraction followed the correlation found by Pierrat (1994). Contact angles were larger for the silanized particles, as compared with unsilanized ones

Distribution of entanglement in light-harvesting complexes and their quantum efficiency

Recent evidence of electronic coherence during energy transfer in photosynthetic antenna complexes has reinvigorated the discussion of whether coherence and/or entanglement has any practical functionality for these molecular systems. Here we investigate quantitative relationships between the quantum yield of a light-harvesting complex and the distribution of entanglement among its components. Our study focusses on the entanglement yield or average entanglement surviving a time scale comparable to the average excitation trapping time. As a prototype system we consider the Fenna-Matthews-Olson (FMO) protein of green sulphur bacteria and show that there is an inverse relationship between the quantum efficiency and the average entanglement between distant donor sites. Our results suggest that longlasting electronic coherence among distant donors might help modulation of the lightharvesting function.Comment: Version accepted for publication in NJ