Browsing by Issue Date, starting with "1999"
Now showing 1 - 10 of 28
Results Per Page
Sort Options
- Urethanes and polyurethanes from suberin 2: synthesis and characterizationPublication . Cordeiro, N.; Belgacem, M.N.; Gandini, A.; Pascoal Neto, C.Polyurethanes based on suberin from cork of Quercus suber L. and conventional isocyanate monomers were prepared and fully characterized in terms of both structure (FTIR and 1 H NMR spectroscopy) and thermal properties (differential scanning calorimetry and thermogravimetric analysis). Two fractions were systematically isolated, namely (i) methylene-chloride soluble products, which corresponded to linear and branched macromolecules and (ii) methylene-chloride insoluble products, representing the crosslinked material. The structures of these polymers were regular and no appreciable side reactions were detected. DSC analyses provided information about the glass transition temperature of both fractions and this parameter was correlated with the stiffness of the isocyanate used. The TGA of these polyurethanes showed that they started to degrade at about 175°C and that the residue at 400°C was around 50%. The highest amounts of insoluble fractions, as well as the highest Tgs, were reached when an initial [NCO]/[OH] of unity was used.
- As artes plásticas na Madeira (1910-1990): conjunturas, factos e protagonistas do panorama artístico regional no século XXPublication . Valente, António Carlos Jardim
- Roteiro turístico-cultural da Freguesia de Gaula: Ilha da MadeiraPublication . Sousa, Élvio; Spínola, Hélder; Nunes, Miguel; Mata, Richard da
- The speed of sound and isentropic compressibility of liquid difluoromethane (HFC32) fromT=(248 to 343) K and pressures up to 65 MPaPublication . Pires, P. F.; Guedes, H. J. R.This work reports experimental data on the speed of sound in liquid difluoromethane ŽHFC32, or R32. from T s Ž248 to 343. K and pressures up to 65 MPa. The results were obtained using a newly-built apparatus, calibrated with toluene over the whole experimental region, and show good agreement with two available data sets. The uncertainties are "0.01 K in the temperature, "0.025 MPa in the pressure up to 35 MPa, and "0.2 MPa above this value. The final uncertainty on the speed of sound is estimated to be "0.2 per cent. The data were fitted using a simple analytical equation and the results are discussed. The isentropic compressibility was calculated over the Ž p, T. surface where the reported speed of sound values and the corresponding literature densities overlap.
- Roteiro turístico [do] Concelho de Santana: MadeiraPublication . Sousa, Élvio; Spínola, Hélder
- Three-wave interaction in two-component quadratic nonlinear latticesPublication . V. V. Konotop, V. V.; Cunha, M. D.; Christiansen, P. L.; Clausen, C. BalslevWe investigate a two-component lattice with a quadratic nonlinearity and find with the multiple scale technique that integrable three-wave interaction takes place between plane wave solutions when these fulfill resonance conditions. We demonstrate that energy conversion and pulse propagation known from three-wave interaction is reproduced in the lattice and that exact phase matching of parametric processes can be obtained in non-phase-matched lattices by tilting the interacting plane waves with respect to each other.
- Taxes and women in the labour force in a Southern European country: the case of PortugalPublication . Marques, Ana Cristina Lino; Pereira, Pedro TelhadoAbstract. On looking at the female labour supply in Europe, it is immediately noticed that there is a large variation among countries. One possible explanation for this fact is that different countries have different tax policies, leading to variations in incentive and costs. This has been investigated in papers such as that of Gustafsson (1992a,b) for countries such as Germany and Sweden. The same exercise has been performed by the present authors for a low-income, southern European country, Portugal, which has one of the highest rates of female participation (out of line with neighbouring countries). Female labour supply does not seem to be very sensitive to fiscal policies, as those policies have only a small influence on the take-home wage. This result appears to be independent of the fact that the female labour supply shows a higher elasticity to wages than that which has been reported for other countries. The present authors also show that Portuguese women contribute a much larger proportion of family earnings than do their counterparts in Sweden and Germany, and that the Portuguese fiscal system is rather neutral. Further studies with data from other countries are needed in order to shed more light on the issue of tax harmonization.
- Da compreensão da arte ao ensino da história da arte, hojePublication . Sardinha, Maria Idalina Ferreira Pereira
- O papel das mulheres da Nazaré na economia haliêuticaPublication . Escallier, Christine
- The speed of sound, and derived thermodynamic properties of liquid trifluoromethane (HFC23) fromT=(258 to 303)K at pressures up to 65MPaPublication . Pires, P. F.; Guedes, H. J. R.This work reports experimental data of the speed of sound in liquid trifluoromethane (HFC23, or R23) from T = (258 to 303) K at pressures up to 65 MPa, measured with a pulse-echo method adapted from Papadakis(1) and Guedes et al.(2) The results are fitted to a rational approximant and compared with literature data.(3) Derived thermodynamic properties such as the isentropic compressibility κs, the isothermal compressibility κT , the cubic expansion coefficient αp, and the specific heat capacity at constant pressure cp are calculated by combining the present experimental data with the density values published by other authors.(4–11) The estimated properties are compared, where possible, with literature data.
- «
- 1 (current)
- 2
- 3
- »