Search results for "Thermal"
showing 10 items of 3576 documents
Emergence of field pennycress (Thlaspi arvense L.): Comparison of two accessions and modelling
2015
Many weed species are becoming rare due to intense agricultural management, which leads to a decrease of biodiversity in agroecosystems. Cultivating some of these species for their oilseed content may help preserve them while profiting agronomically. Thlaspi arvense is one of these species with potential as an industrial crop. The aim of this work was to develop a model to describe the emergence of this species, and that can help to make decisions for its management, whether for conservation or production purposes. The emergence of two accessions of T. arvense, one from Spain and the other from USA, sown in Spain (Almenar) and USA (Morris), over two seasons (2011–12 and 2012–13) and in Riga…
Energy-saving potential of ground source multiple chillers in simple and hybrid configurations for Mediterranean climates
2022
Air conditioning accounts for a large share of energy usage in residential and tertiary sectors. Renewable energy technologies offer promising solutions to reduce the environmental impacts of meeting buildings’ energy loads. The possibility of using the soil as a thermal reservoir for heating and cooling systems has gained growing attention in the last decade due to its high potential for energy saving. In this paper, the benefits achievable using ground source chillers for air conditioning in an office building located in Southern Italy are discussed. A multiple chillers system coupled with a borehole heat exchanger is investigated and compared to conventional air-cooled and water-cooled s…
COOLING OF COMMERCIAL BUILDINGS BY MEANS OF LARGE COLD RADIANT CEILINGS
1991
ABSTRACT The possibility of using different cooling tools working with lower radiant temperatures and higher air velocity is explored. Lower energy consumptions may be achieved in specific climates with reasonable levels of thermal comfort.
Synthesis, characterization, and thermal behavior of steroidal dendrons
2004
A series of novel dendritic steroidal polyesters of first and second generation has been synthesized in convergent fashion by the use of 2,2-bis(hydroxymethyl)propionic acid as a repeating unit. The first- and second-generation hydroxy-functionalized dendrons with a variety of surface modifications were produced through the use of four bile acids: lithocholic acid (LCA), ursodeoxycholic acid (UDCA), deoxycholic acid (DCA), and cholic acid (CA). The thermal behavior of the steroidal dendrons was characterized by differential scanning calorimetry (DSC) and by thermogravimetric analysis (TGA). Finally, quantum chemical calculation methods were used to study the geometries of the dendrons and t…
Adsorption and diffusion of linear and dibranched C6 paraffins in a ZSM-5 zeolite
2002
The adsorption of n-hexane and 2,2-dimethylbutane on a commercial ZSM-5 zeolite is studied under isothermal and isobaric conditions. ZSM-5 exhibits two different behaviours with linear and dibranched alkanes. A substep at 4 molec.uc−1 is observed on the adsorption isotherm of n-hexane at 348 K. A singular adsorption-desorption process is evidenced on the adsorption isobar at 5.5 kPa with 2,2-dimethylbutane at a temperature close to 343 K when the sample is activated at 298 K under vacuum. The diffusivities have been determined by fitting directly the uptake curves with a numerical resolution of second Fick's law based on finite difference method. Microporous diffusion seems to be rate limit…
Insights into the decomposition pathway of a lutetium alkylamido complex via intramolecular C–H bond activation
2017
Abstract Synthesis, characterization and reaction chemistry of lutetium alkylamido LLu(CH2SiMe3)(NHCPh3) (2), L = 2,5-[Ph2P=N(4-iPrC6H4)]2N(C4H2)–, is reported. Complex 2 undergoes cyclometalation of the NHCPh3 ligand at elevated temperatures to produce the orthometalated complex LLu(κ2−N,C-(NHCPh2(C6H4))) (3) which converts to 0.5 equivalents of bis(amido) LLu(NHCPh3)2 (4) upon heating at 80 °C for 24 h. Reaction of complex 2 with 4-dimethylaminopyridine (DMAP) does not promote alkane elimination nor imido formation. A kinetic analysis of the thermal decomposition of complex 2, supported by deuterium labelling studies and computational analysis (PBE0/def2-TZVP/SDD(Lu)), indicate direct Csp…
Catalytic cracking of n-alkane naphtha: The impact of olefin addition and active sites differentiation
2015
An extended dual kinetic model allows to fit the n-heptane cracking results working in a wide range of reaction conditions. The duality of the model is provided by the contribution of monomolecular and bimolecular cracking mechanisms. It takes into account the role played by the olefins formed on the global cracking or added within the feed. Furthermore by means of this model and the kinetic parameters obtained when cracking n-heptane on ZSM-5, it has been observed that, while some characterization techniques show a homogeneous zeolite surface from the point of view of the active sites, rigorous kinetic experiments point to the possibility that the reactant sees a heterogeneous surface with…
The hydrothermal system of the Domuyo volcanic complex (Argentina): A conceptual model based on new geochemical and isotopic evidences
2016
The Domuyo volcanic complex (Neuquén Province, Argentina) hosts one of the most promising geothermal systems of Patagonia, giving rise to thermal manifestations discharging hot and Cl−-rich fluids. This study reports a complete geochemical dataset of gas and water samples collected in three years (2013, 2014 and 2015) from the main fluid discharges of this area. The chemical and isotopic composition (δD-H2O and δ18O-H2O) of waters indicates that rainwater and snow melting are the primary recharge of a hydrothermal reservoir located at relative shallow depth (400–600 m) possibly connected to a second deeper (2–3 km) reservoir. Reactive magmatic gases are completely scrubbed by the hydrotherm…
Notes on the Use of the Tables of Standard ISO 7730 for the Evaluation of the PMV Index
1996
Standard ISO 7730, which is also known as European Standard EN-ISO 7730, provides two alternative methods for the evaluation of the predicted mean vote (PMV) index: a calculation program and a set of tables. In order to use the tables, the operative temperature must be calculated beforehand. The impres sion is given from reading the standard that for a relative humidity of 50%, the two methods are equivalent, i.e. provide the same value for PMV, from the same initial values. In this paper, examples are given showing that the two methods are not equivalent. Differences between them are analysed and a proposal made to introduce an amendment in the next revision of the stan dard.
Co-precipitation synthesis of Nd:YAG nano-powders: the effect of Nd dopant addition with thermal treatment
2007
Nanopowders of Yttrium Aluminium Garnet doped with neodymium ions were obtained by the co-precipitation method from the reaction of aluminium, yttrium and neodymium nitrate with ammonia. The amount of neodymium was selected in order to produce samples of nominal stoichiometry NdXY (3-X)Al5O12 (where X = 0.006, 0.012, 0.024, 0.048, 0.081, 0.096, 0.17, 0.19, 0.38, 0.54, and 0.72, respectively). After washing and drying, the hydroxide precursors were subjected to Thermo-Gravimetry and Differential Thermal Analysis experiments from room temperature up to 1500 °C, which showed the presence of exothermal events accompanying phase transformation phenomena. X-ray diffraction investigations conducte…