Gallium-doped zinc oxide films were prepared by rf magnetron sputtering at room temperature as a function of the substrate-target distance. The best results were obtained for a distance of 10 cm, where a resistivity as low as 2.7×10-4 Ωcm, a Hall mobility of 18 cm2/Vs and a carrier concentration of 1.3×1021 cm-3 were achieved. The films are polycrystalline presenting a strong crystallographic c-axis orientation (002) perpendicular to the substrate. The films present an overall transmittance in the visible part of the spectra of about 85 %, in average. The low resistivity, accomplished with a high growth rate deposited at RT, enables the deposition of these films onto polymeric substrates for flexible applications.

Amorphous undoped a-Si:H films have been produced by hot wire plasma assisted chemical vapour deposition (HWPA-CVD), which combines the hot wire chemical vapour deposition (HW-CVD) and plasma enhanced chemical vapour deposition techniques. In this work we analyse the dissociation mechanism of the gas during the film growth in both processes with a quadrupole mass spectrometer. Besides that, the energy delivered to the gas dissociation is determined and correlated with the films properties. Thus, based on the results of the dissociated species for each deposition condition and process, we explain why the growth rate is enhanced when the filament temperature rises in HW-CVD process and why it decreases as r.f. power is enhanced in HWPA-CVD process. © 2002 Elsevier Science B.V. All rights reserved.

Low-density polyethylene (LDPE) films were thermally aged in a sodium chloride aqueous solution at constant temperature (thermal aging). Some of the samples were simultaneously immersed in solution and subjected to an electric AC field (electrical aging). The dielectric relaxation spectra at 30 degreesC in the range of 10(-5) Hz to 10(5) Hz were obtained for unaged and aged samples. For the low frequency (LF) region (10(-5) Hz to 10(-1) Hz) the time domain technique was used. A lock-in amplifier was used for the 10(-1) Hz to 10(1) Hz medium frequency (MF) region. While for the high frequency (HF), 10(-1) Hz to 10(5) Hz, RLC bridge measurements were performed. The main differences can be seen between electrically, thermally aged and unaged LDPE in the HF and LF regions. The LF peak is a broad peak related to localized space charge injection driven by the electric field. For electrically aged samples this peak increases in an earlier stage of electrical aging, decreasing afterwards. While in thermally aged samples the peak amplitude always increases with aging time. Finally the HF shows the beginning of a peak due to the gamma and beta transitions. This peak decreases with aging disappearing for the most aged samples.

Low-density polyethylene (LDPE) films were thermally aged in a sodium chloride aqueous solution at constant temperature (thermal aging). Some of the samples were simultaneously immersed in solution and subjected to an electric AC field (electrical aging). The dielectric relaxation spectra at 30 degreesC in the range of 10(-5) Hz to 10(5) Hz were obtained for unaged and aged samples. For the low frequency (LF) region (10(-5) Hz to 10(-1) Hz) the time domain technique was used. A lock-in amplifier was used for the 10(-1) Hz to 10(1) Hz medium frequency (MF) region. While for the high frequency (HF), 10(-1) Hz to 10(5) Hz, RLC bridge measurements were performed. The main differences can be seen between electrically, thermally aged and unaged LDPE in the HF and LF regions. The LF peak is a broad peak related to localized space charge injection driven by the electric field. For electrically aged samples this peak increases in an earlier stage of electrical aging, decreasing afterwards. While in thermally aged samples the peak amplitude always increases with aging time. Finally the HF shows the beginning of a peak due to the gamma and beta transitions. This peak decreases with aging disappearing for the most aged samples.

In this work we present results of a study performed on MIS diodes with the following structure: substrate (glass) / Cr (2000Å) / a-Si:H n + (400Å) / a-Si:H i (5500Å) / oxide (0-40Å) / Au (100Å) to determine the influence of the oxide passivation layer grown by different techniques on the electrical performance of MIS devices. The results achieved show that the diodes with oxides grown using hydrogen peroxide present higher rectification factor (2×106) and signal to noise (S/N) ratio (1×107 at -1V) than the diodes with oxides obtained by the evaporation of SiO2, or by the chemical deposition of SiO 2 by plasma of HMDSO (hexamethyldisiloxane), but in the case of deposited oxides, the breakdown voltage is higher, 30V instead of 3-10 V for grown oxides. The ideal oxide thickness, determined by spectroscopic ellipsometry, is dependent on the method used to grow the oxide layer and is in the range between 6 and 20 Å. The reason for this variation is related to the degree of compactation of the oxide produced, which is not relevant for applications of the diodes in the range of ± 1V, but is relevant when high breakdown voltages are required.

The relativistic version of the binary-encounter Bethe (BEB) model is used to calculate cross sections for K-shell ionization of atoms by electron impact. The BEB model requires only two atomic constants, the binding energy and kinetic energy of the K electrons. These constants are listed for carbon to antimony. Comparisons with available experimental data on N, O, Na, Al, Cl, Ca, Cu, Se and Sb show good agreement. The K-shell ionization cross sections for C, Mg, P, S, Cr, As and Cd are tabulated.

This article is based on the lesson presented in the scope of academy activities in the area of Sociology (at FCT-UNL). It is intended to approach the controversies concerning the relation between technology and society (technological determinism, effect on employment, importance of the social behaviours in the definition of needs for new products and equipment), and on the most recent trends (over all, since middle of the last century) in terms of technological evolution and of its social and cultural change. Finally, this subject was dedicated to the presentation of the main factors that has lead to the development of the contribution of sociology for the training and education in engineering. Thus, one intends to acquire new elements on this area of knowledge also presented in other schools of engineering of other countries (for examples, United States and Holland), and how the theoretical beddings are been developed since the beginning of 20th century on the modalities of work organization that imply a cooperation between engineering and social sciences.

Recent studies continue to indicate the existence of a narrow relationship between flexible work organizations and the economic growth, in particular, Sweden and Germany. The measure of this relationship is many times the result of the value added per worker. Therefore, the causes of economic growth must be perceived from the interior of the company (work organization, technology, infrastructures, product design). On the other hand, the capacity of innovation can be perceived by the market through new products and services, and still significant changes with the introduction of new equipment and design of an efficient work organization. In this article it is analyzed the evolution of the productivity and employment levels in Portugal and other European countries, over all, during the decade of 90. An analysis for sector is made still. One verifies often that economic growth can be without employment growth. However, the growth can be obtained when if it reaches bigger added value and the efficiency can be verified when there are diminished costs for a same period of time, although that the labor productivity is also the pointer of the quality of life in a economy, therefore it represents the value produced by the work. Moreover, the total factors productivity is the measure of the technological and organizational progress (don’t includes only the technological investments). It is tried to get and to analyze the available statistics on these dimension in Portugal, concluding that Portugal presents an enterprise structure predominantly based on small and very small companies, a great number of which is market by a weak potential of adaptability, innovation and sustainability. It becomes urgent to take the non-material factors that integrate the productivity dimension, as factors of intervention for a benchmarking that allows a process of sustainable growth.

{Summary: We consider a class of consistent semi-parametric estimators of a positive tail index $\gamma$, parameterized by a tuning or control parameter $\alpha$. Such a control parameter enables us to have access, for any available sample, to an estimator of $\gamma$ with a null dominant component of asymptotic bias, and with a reasonably flat mean squared error pattern, as a function of $k$, the number of top order statistics considered. Moreover, we are able to achieve a high efficiency relative to the classical Hill estimator [ıt B. M. Hill}, Ann. Stat. 3, 1163–1174 (1975; Zbl 0323.62033)], provided we may have access to a larger number of top order statistics than the number needed for optimal estimation through the Hill estimator.}

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