Rhodium complexes modified by simple trialkylphosphines can be used to carry out homogeneous hydroformylation in supercritical carbon dioxide (scCO(2)). The catalyst derived from PEt3 is more active and slightly more selective for the linear products in scCO2 than in toluene, and under the same reaction conditions [100degreesC, 40 bar of CO/H-2 (1:1)] P(OPri)(3) is also an effective ligand giving good catalyst solubility and activity. Other ligands such as PPh3, POct(3), PCy3, and P(4-C6H4But)(3) are less effective because of the low solubility of their rhodium complexes in scCO(2). P(4-C6H4SiMe3)(n) Ph3-n (n = 3 or 1) and P(OPh)(3) impart activity despite their complexes only being poorly soluble in scCO(2). Under subcritical conditions, using PEt3 as the ligand, C7-alcohols from hydrogenation of the first formed aldehydes are the main products whilst above a total pressure of 200 bar, where the solution remains supercritical (monophasic) throughout the reaction, aldehydes are obtained with 97% selectivity. High pressure IR studies in scCO(2) using PEt3 as the ligand are reported.

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Remains of dinosaurian embryos, hatchlings and early juveniles are currently the subject of increasing interest, as new discoveries and techniques now allow to analyse palaeobiological subjects such as growth and life history strategies of dinosaurs. So far, available ‘embryonic’ material mainly involved Ornithopods and some Theropods of Upper Cretaceous age. We describe here the histology of several bones (vertebrae, limb bones) from the tiny but exceptionally well preserved in ovo remains of Upper Jurassic Theropod dinosaurs from the Paimogo locality near Lourinhã (Portugal). This Jurassic material allows to extend in time and to considerably supplement in great details our knowledge of early phases of growth in diameter and in length of endoskeletal bones of various shape, as well as shape modelling among carnivorous dinosaurs. Endochondral ossification in both short and long bones involves extensive pads of calcified cartilages permeated by marrow buds. We discuss the likely occurrence of genuine cartilage canals in dinosaurs and of an avian-like ‘medullary cartilaginous cone’ in Theropods. Patterns of periosteal ossification suggest high initial growth rates (20 μ m·day−1 or more), at once modulated by precise and locally specific changes in rates of new bone deposition. The resulting very precise shape modelling appears to start early and to involve at once some biomechanical components.

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In this work a new structure is proposed for position sensitive detectors consisting of glass/Cr/aSi:H(n+)/a-Si:H(i)/ZnO, where the ZnO forms an heterojunction with the a-Si:H(i). The results show that this structure works with success in the fabrication of linear position sensitive detectors. The devices present a good nonlinearity of ≈ 2% and a good sensitivity to the light intensity. The main advantages of this structure over the classical p-i-n are an easier to built topology and a higher yield due to a better immunity to the a-Si:H pinholes, since the ZnO does not diffuse so easily into a-Si:H as the metal does, which are the cause of frequent failure in the p-i-n devices due to short-circuits caused by the deposition of the metal over the a-Si:H. In this structure the illumination is made directly on the ZnO, so a transparent substrate is not needed and a larger range of substrates can be used.

The displacement model of the hybrid-{T}refftz finite element formulation is applied to the solution of geometrically and physically linear static and dynamic problems. As the approximation bases solve locally the governing system of differential equations, the errors in the approximation affect only the implementation of the boundary conditions. Potential and elastostatic problems are used to illustrate the enforcement of the boundary conditions and the convergence of the solutions in energy, stresses and displacements, under both p- and h-refinement sequences and their insensitivity to mesh distortion, incompressibility and positioning of the coordinate system of the approximation basis. Also illustrated is the use of elements with arbitrary geometry and the efficiency that can be reached by including in the bases the solutions associated with dominant local effects, in particular those associated with singular stress fields. An adaptive p-refinement algorithm that exploits the naturally hierarchical nature of the approximation bases is presented and assessed. The formulation is generalised for elastodynamic analysis in the frequency domain of both bounded and unbounded domains, which are modelled either with absorbing boundary conditions or with semi-infinite elements that satisfy the Sommerfeld condition. The performance of the formulation is illustrated with tests on the convergence of the solutions in energy, stresses and displacements and on their insensitivity to mesh distortion, wave length and position of the absorbing boundary, for a wide spectrum of forcing frequencies and under both p- and h-refinement sequences.

Hydrogenated amorphous silicon photochemical sensors based on Pd-MIS structures were produced by Plasma Enhanced Chemical Vapor Deposition with two different oxidized surfaces (thermal and chemical oxidation). The behaviour of dark and illuminated current-voltage characteristics in air and in the presence of a hydrogen atmosphere is explained by the changes induced by the gases in the work function of the metal, modifying the electrical properties of the interface. The photochemical sensors produced present more than 2 orders of magnitude variation on the reverse dark current when in presence of 400 ppm hydrogen to which it corresponds a decrease of 45% on the open circuit voltage.

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The aim of this paper is to present data on the dependence of the electro-optical characteristics and structure of n-type microcrystalline silicon films on the r.f. power used during the deposition of films produced by the plasma-enhanced chemical vapour deposition technique. The interest of these films arise from the fact that they combine some electro-optical advantages of amorphous (wide optical gap) and crystalline materials (electronic behaviour), highly interesting in the production of a wide variety of optoelectronic devices such as solar cells and thin film transistors. In this paper, microcrystalline n-type films presenting simultaneously optical gaps of about 2.3 eV, dark conductivity of 6.5 S cm-1 and Hall mobility of about 0.86 cm2 V-1 s-1 will be reported, the highest combined values for n-type microcrystalline silicon films, as far as we know. © 1997 Elsevier Science S.A.

Today one can understand the wider use of the anthropocentrism concept applied to the production architectures, emerging a new value of the intuitive capacities and human knowledge in the optimization and flexibilization of the manufacturing processes. Having a flexible production and assembly system architecture that exists at UNINOVA-CRI, we will try to develop some exploratory hypothesis on the applicability of the hybridizing concept and its repercussions in the definition of working places, in their organization and formation of working teams. We will underline some aspects that should be taken into consideration when are design such systems, including some ergonomical aspects.

The aim of this work is to present the main optoelectronic characteristics of large area 1D position sensitive detectors based on amorphous silicon p-i-n diodes. From that, the device resolution, response time and detectivity are derived and discussed concerning the field of applications of the 1D thin film position sensitive detectors.

In the past we have developed a transient technique, called the Flying Spot Technique (FST). FST allows, not only to infer the ambipolar diffusion length but also the effective lifetime of the photogenerated carriers once the light spot velocity and geometry of the structure were known. In this paper, we propose to apply this technique backwards in order to detect the path and velocity of an object that is moving in the direction of a light source. The light reflected back from the object is analyzed through a p.i.n structure being the transient transverse photovoltage dependent on the movement of the object (position and velocity). Assuming that the transport properties of the material and the geometry of the device are known and using a triangulation method we show that it is possible to map the movement of the object. Details concerning material characterization, simulation and device geometry are presented.

PIN devices based on hydrogenated amorphous silicon (a-Si:H) became fundamental elements of many different types sensors, based on either the transverse or the lateral photovoltaic effect. In the past we have developed a transient technique, called the Flying Spot Technique (FST), based on the lateral photoeffect. FST allows, not only to infer the ambipolar diffusion length but also the effective lifetime of the photogenerated carriers once the light spot velocity and geometry of the structure were known. In this paper we propose to apply this technique backwards in order to detect the path and velocity of an object that is moving in a light source direction. The light reflected back from the object is analyzed through p.i.n. structure being the transient transverse photovoltage dependent on the object movement (position and velocity). Assuming known the transport properties of the material and the geometry of the device and using a triangulation method we show that it is possible to map the object movement. Details concerning material characterization, simulation and device geometry are presented.

In this paper one presents and discuss the hybridation concept using some aspect that integrate it, as the physical architecture of automated systems (hardware), the information system that integrates that architecture and the working places design. Analyzed are also the inter-dependences of those aspects, and we have as a reference the flexible production and assembly system existent at UNINOVA-CRI. The focus is made on possible problems that can occur with the use of possible development of those systems, namely: a) full automation with centralized human control, b) non-automated process of shop-floor work with a system “one man, one machine”, c) hybrid system of automated cells with “elastic” human jobs.

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Mode of operation and area of rnhanced efficiency for series-resonant converters is presented. Frequency control on voltage source DC-DC converters is discussed and other principles of control are introduced. Optimum modes of operation for power transistor resonant converters are also considered. For even better efficiency a resonant current shaping is discussed.

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Undoped and doped hydrogenated amorphous silicon semiconductors (a-Si:H) have been produced by a two consecutive decomposition deposition chamber (TCDDC) system assisted by electromagnetic static fields. Through this technique, a spatial separation is achieved between the plasma chemistry and that of the deposition to avoid ion and electron (with high energies) bombardment on the growing surface. Besides this, the use of a static magnetic field perpendicular to the substrate will promote plasma confinement, so avoiding its contamination by residual gases adsorbed on the reactor walls. On the other hand, the use of two grids dc biased in the deposition chamber, will allow control of the main film precursors, responsible for the electro-optical and structural properties of deposited films. In this paper we shall discuss the deposition method used as well as the transport, structural and morphological properties presented by deposited films and its dependence on deposition parameters used. © 1989.