Effect of polymer-polymer interactions on the surface tension of colloid-polymer mixtures

The density profile and surface tension for the interface of phase-separated colloid-polymer mixtures have been studied in the framework of the square gradient approximation for both ideal and interacting polymers in good solvent. The calculations show that in the presence of polymer-polymer excluded volume interactions the interfaces have lower widths and surface tensions compared to the case of ideal polymers. These results are a direct consequence of the shorter range and smaller depth of the depletion potential between colloidal particles induced by interacting polymers.Comment: 12 pages, 5 figures, accepted for J. Chem. Phy

A density--functional study of interfacial properties of colloid--polymer mixtures

Interfacial properties of colloid--polymer mixtures are examined within an effective one--component representation, where the polymer degrees of freedom are traced out, leaving a fluid of colloidal particles interacting via polymer--induced depletion forces. Restriction is made to zero, one and two--body effective potentials, and a free energy functional is used which treats colloid excluded volume correlations within Rosenfeld's Fundamental Measure Theory, and depletion--induced attraction within first--order perturbation theory. This functional allows a consistent treatment of both ideal and interacting polymers. The theory is applied to surface properties near a hard wall, to the depletion interaction between two walls, and to the fluid--fluid interface of demixed colloid--polymer mixtures. The results of the present theory compare well with predictions of a fully two--component representation of mixtures of colloids and ideal polymers (the Asakura--Oosawa model), and allow a systematic investigation of the effects of polymer--polymer interactions on interfacial properties. In particular, the wall surface tension is found to be significantly larger for interacting than for ideal polymers, while the opposite trend is predicted for the fluid--fluid interfacial tension.Comment: submitted to J. Phys. Chem. B, special issue in honour of David Chandle

Modelling study of transformations of the exchange flows along the Strait of Gibraltar

Abstract. Vertical transfers of heat, salt and mass between the inflowing and outflowing layers at the Strait of Gibraltar are explored basing on the outputs of a three-dimensional fully nonlinear numerical model. The model covers the entire Mediterranean basin and has a very high spatial resolution around the strait (1/200∘). Another distinctive feature of the model is that it includes a realistic barotropic tidal forcing (diurnal and semi-diurnal), in addition to atmospheric pressure and heat and water surface fluxes. The results show a significant transformation of the properties of the inflowing and outflowing water masses along their path through the strait. This transformation is mainly induced by the recirculation of water, and therefore of heat and salt, between the inflowing and outflowing layers. The underlying process seems to be the hydraulic control acting at the Espartel section, Camarinal Sill and Tarifa Narrows, which limits the amount of water that can cross the sections and forces a vertical recirculation. This results in a complex spatio-temporal pattern of vertical transfers, with the sign of the net vertical transfer being opposite in each side of the Camarinal Sill. Conversely, the mixing seems to have little influence on the heat and salt exchanged between layers (∼2 %–10 % of advected heat and salt). Therefore, the main point of our work is that most of the transformation of water properties along the strait is induced by the vertical advection of heat and salt and not by vertical mixing. A simple relationship between the net flux and the vertical transfers of water, heat and salt is also proposed. This relationship could be used for the fine-tuning of coarse-resolution model parameterizations in the strait

Estimating the air change rates in dwellings using a heat balance approach

Infiltration and ventilation rates in domestic buildings vary with construction type, weather conditions and the operation of openings in the fabric. Generating good estimates of ventilation is important for modelling, simulation and performance assessment as it has a significant impact on energy consumption. Physical tests can be applied to estimate leakage, but this is cumbersome and impractical to apply in most cases. This paper applies a heat balance approach to energy monitoring data to estimate a parameter that describes the combined ventilation and infiltration rates in real family homes. These estimates are compared with published values and a model is presented that describes the air change rate as a function of user behaviour (control of openings) and varying wind speed. The paper demonstrates that it is possible to estimate plausible air change rates from such data

Characterization of the Subsurface of 67P/Churyumov-Gerasimenko's Abydos Site

We investigate the structure of the subsurface of the Abydos site using a cometary nucleus model with parameters adapted to comet 67P/Churyumov-Gerasimenko and the Abydos landing site. We aim to compare the production rates derived from our model with those of the main molecules measured by Ptolemy. This will allow us to retrieve the depths at which the different molecules still exist in solid form

Development and characterization of a new natural fiber reinforced thermoplastic (NFRP) with Cortaderia selloana (Pampa grass) short fibers

[EN] In this work, fully bio-based thermoplastic composites are manufactured with bio-based polyethylene (from sugarcane) and short fibers coming from Cortaderia selloana (CS) wastes. These wastes are characterized by high cellulose content, which can provide high stiffness to the polymeric matrix. The effect of Cortaderia selloana short fibers on thermal properties has been evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The effect of the filler load on mechanical properties has also been evaluated by tensile and impact tests as well as the effects of different coupling agents. Fiber-matrix interactions have been studied by scanning electron microscopy (SEM). The addition of 15-30 wt% Cortaderia selloana short fiber leads to high elastic and flexural modulus without remarkable changes in thermal degradation of the polymer composite. (C) 2017 Elsevier Ltd. All rights reserved.This work was funded by the Conselleria d'Educacio, Cultura i Esport (Generalitat Valenciana) Ref: GV/2014/008. The authors declare that they have no conflict of interest.Jorda-Vilaplana, A.; Carbonell-Verdu, A.; Samper, M.; Pop, A.; García Sanoguera, D. (2017). Development and characterization of a new natural fiber reinforced thermoplastic (NFRP) with Cortaderia selloana (Pampa grass) short fibers. Composites Science and Technology. 145:1-9. https://doi.org/10.1016/j.compscitech.2017.03.036S1914

Energy Modelling and Calibration of Building Simulations: A Case Study of a Domestic Building with Natural Ventilation

[EN] In this paper, the building energy performance modelling tools TRNSYS (TRaNsient SYstem Simulation program) and TRNFlow (TRaNsient Flow) have been used to obtain the energy demand of a domestic building that includes the air infiltration rate and the effect of natural ventilation by using window operation data. An initial model has been fitted to monitoring data from the case study, building over a period when there were no heat gains in the building in order to obtain the building infiltration air change rate. After this calibration, a constant air-change rate model was established alongside two further models developed in the calibration process. Air change rate has been explored in order to determine air infiltrations caused by natural ventilation due to windows being opened. These results were compared to estimates gained through a previously published method and were found to be in good agreement. The main conclusion from the work was that the modelling ventilation rate in naturally ventilated residential buildings using TRNSYS and TRNSFlow can improve the simulation-based energy assessment.Aparicio-Fernández, C.; Vivancos, J.; Cosar-Jorda, P.; Buswell, RA. (2019). Energy Modelling and Calibration of Building Simulations: A Case Study of a Domestic Building with Natural Ventilation. Energies. 12(17):1-13. https://doi.org/10.3390/en12173360S1131217Grygierek, K., & Ferdyn-Grygierek, J. (2018). Multi-Objective Optimization of the Envelope of Building with Natural Ventilation. Energies, 11(6), 1383. doi:10.3390/en11061383Moran, P., Goggins, J., & Hajdukiewicz, M. (2017). Super-insulate or use renewable technology? Life cycle cost, energy and global warming potential analysis of nearly zero energy buildings (NZEB) in a temperate oceanic climate. Energy and Buildings, 139, 590-607. doi:10.1016/j.enbuild.2017.01.029Allouhi, A., El Fouih, Y., Kousksou, T., Jamil, A., Zeraouli, Y., & Mourad, Y. (2015). Energy consumption and efficiency in buildings: current status and future trends. Journal of Cleaner Production, 109, 118-130. doi:10.1016/j.jclepro.2015.05.139Cosar-Jorda, P., Buswell, R. A., & Mitchell, V. A. (2018). Determining of the role of ventilation in residential energy demand reduction using a heat-balance approach. Building and Environment, 144, 508-518. doi:10.1016/j.buildenv.2018.08.053Feijó-Muñoz, J., Poza-Casado, I., González-Lezcano, R. A., Pardal, C., Echarri, V., Assiego De Larriva, R., … Meiss, A. (2018). Methodology for the Study of the Envelope Airtightness of Residential Buildings in Spain: A Case Study. Energies, 11(4), 704. doi:10.3390/en11040704Domínguez-Amarillo, S., Fernández-Agüera, J., Campano, M. Á., & Acosta, I. (2019). Effect of Airtightness on Thermal Loads in Legacy Low-Income Housing. Energies, 12(9), 1677. doi:10.3390/en12091677Cheng, P. L., & Li, X. (2018). Air infiltration rates in the bedrooms of 202 residences and estimated parametric infiltration rate distribution in Guangzhou, China. Energy and Buildings, 164, 219-225. doi:10.1016/j.enbuild.2017.12.062Hou, J., Zhang, Y., Sun, Y., Wang, P., Zhang, Q., Kong, X., & Sundell, J. (2018). Air change rates at night in northeast Chinese homes. Building and Environment, 132, 273-281. doi:10.1016/j.buildenv.2018.01.030Zhai, Z. (John), Mankibi, M. E., & Zoubir, A. (2015). Review of Natural Ventilation Models. Energy Procedia, 78, 2700-2705. doi:10.1016/j.egypro.2015.11.355Han, G., Srebric, J., & Enache-Pommer, E. (2015). Different modeling strategies of infiltration rates for an office building to improve accuracy of building energy simulations. Energy and Buildings, 86, 288-295. doi:10.1016/j.enbuild.2014.10.028Laverge, J., & Janssens, A. (2013). Optimization of design flow rates and component sizing for residential ventilation. Building and Environment, 65, 81-89. doi:10.1016/j.buildenv.2013.03.019Bhandari, M., Hun, D., Shrestha, S., Pallin, S., & Lapsa, M. (2018). A Simplified Methodology to Estimate Energy Savings in Commercial Buildings from Improvements in Airtightness. Energies, 11(12), 3322. doi:10.3390/en11123322Pisello, A. L., Castaldo, V. L., Taylor, J. E., & Cotana, F. (2016). The impact of natural ventilation on building energy requirement at inter-building scale. Energy and Buildings, 127, 870-883. doi:10.1016/j.enbuild.2016.06.023Tronchin, L., Fabbri, K., & Bertolli, C. (2018). Controlled Mechanical Ventilation in Buildings: A Comparison between Energy Use and Primary Energy among Twenty Different Devices. Energies, 11(8), 2123. doi:10.3390/en11082123Ashdown, M. M. A., Crawley, J., Biddulph, P., Wingfield, J., Lowe, R., & Elwell, C. A. (2019). Characterising the airtightness of dwellings. International Journal of Building Pathology and Adaptation, 38(1), 89-106. doi:10.1108/ijbpa-02-2019-0024Crawley, J., Wingfield, J., & Elwell, C. (2018). The relationship between airtightness and ventilation in new UK dwellings. Building Services Engineering Research and Technology, 40(3), 274-289. doi:10.1177/0143624418822199Jones, B., Das, P., Chalabi, Z., Davies, M., Hamilton, I., Lowe, R., … Taylor, J. (2015). Assessing uncertainty in housing stock infiltration rates and associated heat loss: English and UK case studies. Building and Environment, 92, 644-656. doi:10.1016/j.buildenv.2015.05.033Schulze, T., & Eicker, U. (2013). Controlled natural ventilation for energy efficient buildings. Energy and Buildings, 56, 221-232. doi:10.1016/j.enbuild.2012.07.044Stavridou, A. D., & Prinos, P. E. (2017). Unsteady CFD Simulation in a Naturally Ventilated Room with a Localized Heat Source. Procedia Environmental Sciences, 38, 322-330. doi:10.1016/j.proenv.2017.03.087LEEDR Project Home Energy Datasethttps://repository.lboro.ac.uk/articles/LEEDR_project_home_energy_dataset/6176450Met Office Integrated Data Archive System (MIDAS) Land and Marine Surface Stations Data (1853-current)http://catalogue.ceda.ac.uk/uuid/220a65615218d5c9cc9e4785a3234bd0Buswell, R., Webb, L., Mitchell, V., & Leder Mackley, K. (2016). Multidisciplinary research: should effort be the measure of success? Building Research & Information, 45(5), 539-555. doi:10.1080/09613218.2016.1194601National Grid UKhttps://www.nationalgrid.com/uk/gas/market-operations-and-data/calorific-value-cvHome Heating Guide: Boiler Efficiency Tableshttps://www.homeheatingguide.co.uk/efficiency-tablesRuiz, G., & Bandera, C. (2017). Validation of Calibrated Energy Models: Common Errors. Energies, 10(10), 1587. doi:10.3390/en10101587Hong, T., Piette, M. A., Chen, Y., Lee, S. H., Taylor-Lange, S. C., Zhang, R., … Price, P. (2015). Commercial Building Energy Saver: An energy retrofit analysis toolkit. Applied Energy, 159, 298-309. doi:10.1016/j.apenergy.2015.09.002Nasir, Z. A., & Colbeck, I. (2013). Particulate pollution in different housing types in a UK suburban location. Science of The Total Environment, 445-446, 165-176. doi:10.1016/j.scitotenv.2012.12.042Dimitroulopoulou, C. (2012). Ventilation in European dwellings: A review. Building and Environment, 47, 109-125. doi:10.1016/j.buildenv.2011.07.01

CHARACTERIZATION OF THE 105 K SUPERCONDUCTOR Tl2Ba2CaCu208 ("2212")

International audienceHomogeneous Tl1.8Ba2CaCu208 ceramics were synthesized by a novel route, starting from Tl2Ba205 precursors and using high gas pressures. This method allows tight control of thallium losses, resulting in dense, large-grained samples with sharp superconducting transitions above 105 K. Results of a characterization by X-ray diffraction, optical micrographs and micro-probe analysis are presented, together with selected physical properties

The natural capital of temporary rivers: characterising the value of dynamic aquatic-terrestrial habitats. Valuing Nature Natural Capital Synthesis Reports, VNP12

Temporary rivers naturally transition between flowing, pool and dry states, creating aquatic–terrestrial habitat mosaics that change in space and time. These dynamic habitats are common in the UK's cool, wet climate. Here, they take many forms, from headwater streams that may dominate networks in remote uplands, to winterbourne rivers crossing the chalk of south England. We examine published and unpublished sources to provide an evidence-informed characterisation of the natural assets in temporary rivers