973 research outputs found

    Application of new measurement techniques and strategies to measure ammonia emissions from agricultural activities

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    Agriculture is the main contributor to the ammonia emissions in the Netherlands. In order to comply with the ammonia emission reduction assigned to the Netherlands, new techniques have been implemented to reduce the ammonia emissions from animal houses, and after application of slurry into the field

    Free-energy functional for freezing transitions: Hard sphere systems freezing into crystalline and amorphous structures

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    A free-energy functional that contains both the symmetry conserved and symmetry broken parts of the direct pair correlation function has been used to investigate the freezing of a system of hard spheres into crystalline and amorphous structures. The freezing parameters for fluid-crystal transition have been found to be in very good agreement with the results found from simulations. We considered amorphous structures found from the molecular dynamics simulations at packing fractions η\eta lower than the glass close packing fraction ηJ\eta_{J} and investigated their stability compared to that of a homogeneous fluid. The existence of free-energy minimum corresponding to a density distribution of overlapping Gaussians centered around an amorphous lattice depicts the deeply supercooled state with a heterogeneous density profile

    Technique of uncertainty and sensitivity analysis for sustainable building energy systems performance calculations

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    Sustainable buildings design process is typical for modeling and simulation usage. The main reason is because there is generally no experience with such buildings and there is lot of new approaches and technical solutions to be used. Computer simulation could be supporting tool in engineering design process and can bring the good way for reducing energy consumption together with optimalization algorithm. For the optimization process we have to know which most sensitive input parametr from many of them has to be investigate. Therefore at first is necessary to perform the sensitivity analysis and find out the "strongest" input parametrs which most affecting the results under observation. Also still the simulation tools are mainly using to predict energy consumption, boiler and chiller loads, indoor air quality, etc. before the building is build. The information about the building envelope, schedule and HVAC components are unclear and can bring large uncertainty in results by setting this inputs to the simulation tools. Paper presents preview of uncertainty and sensitivity analysis. This techniques are shown on case study concretely BESTEST case600 with DRYCOLD climate conditions. Also systems VAV (variable volume of air) and water fancoil system are compared. For this prototype the simulation tool IES was chosen

    Residual absorption at zero temperature in d-wave superconductors

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    In a d-wave superconductor with elastic impurity scattering, not all the available optical spectral weight goes into the condensate at zero temperature, and this leads to residual absorption. We find that for a range of impurity parameters in the intermediate coupling regime between Born (weak) and unitary (strong) limit, significant oscillator strength remains which exhibits a cusp like behavior of the real part of the optical conductivity with upward curvature as a function of frequency, as well as a quasilinear temperature dependence of the superfluid density. The calculations offer an explanation of recent data on ortho-II YBa2_2Cu3_3O6.5_{6.5} which has been considered anomalous.Comment: Accepted for publication by Phys. Rev. B 7 Pages and 4 Figure

    A Consistent Picture of Electronic Raman Scattering and Infrared Conductivity in the Cuprates

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    Calculations are presented for electronic Raman scattering and infrared conductivity in a dx2−y2d_{x^{2}-y^{2}} superconductor including the effects of elastic scattering via anisotropic impurities and inelastic spin-fluctuation scattering. A consistent description of experiments on optimally doped Bi-2212 is made possible by considering the effects of correlations on both inelastic and elastic scattering.Comment: 4 pages Revtex, 5 embedded eps file

    Optimization of a Solar Chimney Design to Enhance Natural Ventilation in a Multi-Storey Office Building

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    Natural ventilation of buildings can be achieved with solar-driven , buoyancy-induced airflow through a solar chimney channel. Research on solar chimneys has covered a wide range of topics, yet study of the integration in multi-storey buildings has been performed in few numerical studies , where steady-state conditions were assumed. In practice, if the solar chimney is to be used in an actual building, dynamic performance simulations would be required for the specific building design and climate. This study explores the applicability of a solar chimney in a prototype multi-storey office building in the Netherlands. Sensitivity analysis and optimization of the design will be performed via dynamic performance simulations in ESP-r. The robustness of the optimized design will be tested at the final stage , against e.g. windows' opening by users. This is an ongoing project; calibration of the solar chimney model and preliminary sensitivity analysis results are presented here.

    Exploring the Optimal Thermal Mass to Investigate the Potential of a Novel Low-Energy House Concept

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    In conventional buildings thermal mass is a permanent building characteristic depending on the building design. However, none of the permanent thermal mass concepts are optimal in all operational conditions. We propose a concept that combines the benefits of buildings with low and high thermal mass by applying hybrid adaptable thermal storage (HATS) systems and materials to a lightweight building. The HATS concept increases building performance and the robustness to changing user behavior, seasonal variations and future climate changes. In this paper the potential of the novel HATS concept is investigated by determining the sensitivity of the optimal thermal mass of a building to the change of seasons and to changing occupancy patterns. The optimal thermal mass is defined as the quantity of the thermal mass that provides the best building performance (based on a trade-off between the building performance indicators). Building performance simulation and multi-objective optimization techniques are used to define the optimal thermal mass of a case study in the Netherlands. Simulation results show that the optimal quantity of the thermal mass is sensitive to the change of seasons and occupancy patterns. This implies that the building performance will benefit from implementing HATS. Furthermore, the results show that using HATS reduces the heating energy demand of the case study with 26% and reduces weighted over- and underheating hours with 85%

    Optical and Thermal-Transport Properties of an Inhomogeneous d-Wave Superconductor

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    We calculate transport properties of disordered 2D d-wave superconductors from solutions of the Bogoliubov-de Gennes equations, and show that weak localization effects give rise to a finite frequency peak in the optical conductivity similar to that observed in experiments on disordered cuprates. At low energies, order parameter inhomogeneities induce linear and quadratic temperature dependencies in microwave and thermal conductivities respectively, and appear to drive the system towards a quasiparticle insulating phase.Comment: 5 pages,3 figure

    The Guaymas Basin Subseafloor Sedimentary Archaeome Reflects Complex Environmental Histories

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    Highlights ‱ Archaeal community composition reflects locally specific environmental challenges ‱ Biogeochemical properties do not predict archaeal community structure ‱ Environmental history controls subseafloor archaeal populations Summary We explore archaeal distributions in sedimentary subseafloor habitats of Guaymas Basin and the adjacent Sonora Margin, located in the Gulf of California, MĂ©xico. Sampling locations include (1) control sediments without hydrothermal or seep influence, (2) Sonora Margin sediments underlying oxygen minimum zone water, (3) compacted, highly reduced sediments from a pressure ridge with numerous seeps at the base of the Sonora Margin, and (4) sediments impacted by hydrothermal circulation at the off-axis Ringvent site. Generally, archaeal communities largely comprise Bathyarchaeal lineages, members of the Hadesarchaea, MBG-D, TMEG, and ANME-1 groups. Variations in archaeal community composition reflect locally specific environmental challenges. Background sediments are divided into surface and subsurface niches. Overall, the environmental setting and history of a particular site, not isolated biogeochemical properties out of context, control the subseafloor archaeal communities in Guaymas Basin and Sonora Margin sediments
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