Study of welding strengh in PVC profiles

Polyvinyl chloride, PVC, is one of the most widely produced and used plastic, being commonly used in civil industry due to its wide range of mechanical properties (from rigid to flexible), low cost, durability, and easy to assemble. Due to its good mechanical and thermal properties, PVC can be used to produce window and door frames, protecting the interior from the external actions, such as noise and temperature gradients. In order to achieve the final dimensions and geometry, previously extruded profiles must be cut and assembled, being the butt welding one of the most efficient techniques. This plastic welding method involves three main steps: i) pressing the parts to be joined against either side of a heated plate; ii) removing the plate when the parts are sufficiently molten and iii) pressing the components together and holding them until they are cooled. The amount of molten material, generated during the heating stage at an adequate heating time and the plate temperature, as well as the amount of material forced out from the joint during the pressing stage (joining displacement), have major influence in the final welding properties. Although the lack of information about the butt welding of PVC, previous studies with for others materials [1-3] showed that the welding strength can be optimized changing the plate temperature and/or joining displacement. The aim of this work was to study the influence of the plate temperature and the heating time in the welding strength of PVC profiles used in windows frames. The profiles were welded in an industrial butt welder machine, setting the plate temperature at 245ºC, 260ºC and 275ºC and the heating time at 15 and 20s. The mechanical properties were evaluated by mechanical bending tests, according to UNE-EN 514 standard and the welding strength was correlated with the morphology of the welded parts observed by optical microscopy. The results are showing that the increase of plate temperature and heating time increase the welding strength. However, the presence of impurities in the joint, such as trapped air or degraded material, as well as the joint alignment, can have a detrimental effect on the welding strength, as observed by the morphological analyses

A unification in the theory of linearization of second order nonlinear ordinary differential equations

In this letter, we introduce a new generalized linearizing transformation (GLT) for second order nonlinear ordinary differential equations (SNODEs). The well known invertible point (IPT) and non-point transformations (NPT) can be derived as sub-cases of the GLT. A wider class of nonlinear ODEs that cannot be linearized through NPT and IPT can be linearized by this GLT. We also illustrate how to construct GLTs and to identify the form of the linearizable equations and propose a procedure to derive the general solution from this GLT for the SNODEs. We demonstrate the theory with two examples which are of contemporary interest.Comment: 8 page

Non universality of entanglement convertibility

Recently, it has been suggested that operational properties connected to quantum computation can be alternative indicators of quantum phase transitions. In this work we systematically study these operational properties in 1D systems that present phase transitions of different orders. For this purpose, we evaluate the local convertibility between bipartite ground states. Our results suggest that the operational properties, related to non-analyticities of the entanglement spectrum, are good detectors of explicit symmetries of the model, but not necessarily of phase transitions. We also show that thermodynamically equivalent phases, such as Luttinger liquids, may display different convertibility properties depending on the underlying microscopic model.Comment: 5 pages + references, 4 figures - improved versio

Prosodic, syntactic, semantic guidelines for topic structures across domains and corpora

This paper presents the annotation guidelines applied to naturally occurring speech, aiming at an integrated account of contrast and parallel structures in European Portuguese. These guidelines were defined to allow for the empirical study of interactions among intonation and syntax-discourse patterns in selected sets of different corpora (monologues and dialogues, by adults and teenagers). In this paper we focus on the multilayer annotation process of left periphery structures by using a small sample of highly spontaneous speech in which the distinct types of topic structures are displayed. The analysis of this sample provides fundamental training and testing material for further application in a wider range of domains and corpora. The annotation process comprises the following time-linked levels (manual and automatic): phone, syllable and word level transcriptions (including co-articulation effects); tonal events and break levels; part-of-speech tagging; syntactic-discourse patterns (construction type; construction position; syntactic function; discourse function), and disfluency events as well. Speech corpora with such a multi-level annotation are a valuable resource to look into grammar module relations in language use from an integrated viewpoint. Such viewpoint is innovative in our language, and has not been often assumed by studies for other languages.info:eu-repo/semantics/acceptedVersio

Tube epifauna of the Polychaete Phyllochaetopterus socialis Claparede.

Made available in DSpace on 2014-07-25T06:11:32Z (GMT). No. of bitstreams: 1 1401.pdf: 272638 bytes, checksum: f25efb35002aebef23759669f7748bb2 (MD5) Previous issue date: 2004-06-0

Tobacco rattle virus and its associated vector trichodorid nematodes in Portugal

Tobacco rattle virus (TRV, genus Tobravirus), transmitted by trichodorid nematodes, occurs as a wide range of serologically distinguishable strains that cause diseases in various economically important crops. The virus and its associated vector nematodes occur world-wide, being particularly prevalent in Europe and North America. In Portugal, an investigation is being conducted to identify TRV strains occurring in association with their natural vector species. The project has focused on potato growing areas in northern and central Portugal, with soil sampling biased in favour of areas where TRV-like symptoms have been reported. Nematodes were extracted from soil and phenotypically identified. TRV was recovered from nematodes in virus transmission studies, and identification confirmed using sap transmission tests, a leaf squash method with EM, ELISA, ISEM, and RT-PCR. Trichodorids were recovered frequently from potato fields, and the species identified were: Trichodorus lusitanicus, T. primitivus, Paratrichodorus anemones, P. hispanus, P. minor, P. pachydermus, also three new undescribed species and an unidentified Paratrichodorus species. TRV occurred in 4 of 58 (7%) soil samples in association with trichodorids: one in the North and the others in the centre of the country. Molecular characterisation of the TRV isolates and their associated vector trichodorids is presently in process

Canalização de efeitos genéticos e ambientais para pesos do nascimento à maturidade e taxa de concepção em fêmeas de bovinos da raça Canchim.

As contribuições relativas dos componentes genéticos e ambientais para as correlações fenotípicas entre pesos do nascimento a maturidade e taxa de concepção, em quatro ciclos reprodutivos, em fêmeas da raca Canchim mantidas em regime de pastagens na Embrapa Pecuária Sudeste, São Carlos, SP, foram determinadas com o objetivo de analisar o padrão de desenvolvimento daquelas características ate a maturidade. Os resultados obtidos mostraram que o padrão de desenvolvimento das características foi influenciado por mecanismos fisiológicos diferentes e que, a maturidade, houve canalização dos efeitos genéticos e ambientais, com antagonismos entre as características de crescimento e a taxa de concepção

Preparation of biodegradable materials by reactive extrusion

This work aimed to prepare biodegradable polymeric materials based on blends of a synthetic high density polyethylene (HDPE) and biodegradable polymers such as polylactic acid (PCL) and poly(caprolactone) (PLA), in a co-rotating twin-screw extruder. A polyethylene modified with maleic anhydride was used as compatibiliser. The mechanical results showed that the addition of PLA improves the blends stiffness while the addition of PCL leads to materials with a greater elongation at break and a lower Young modulus. This feature is related with the mechanical properties of each material as well as the adhesion between them. Concerning the biodegradability tests, it was found that HDPE/PCL blend presents the highest degree of biodegradability

Analysis of return distributions in the coherent noise model

The return distributions of the coherent noise model are studied for the system size independent case. It is shown that, in this case, these distributions are in the shape of q-Gaussians, which are the standard distributions obtained in nonextensive statistical mechanics. Moreover, an exact relation connecting the exponent $\tau$ of avalanche size distribution and the q value of appropriate q-Gaussian has been obtained as q=(tau+2)/tau. Making use of this relation one can easily determine the q parameter values of the appropriate q-Gaussians a priori from one of the well-known exponents of the system. Since the coherent noise model has the advantage of producing different tau values by varying a model parameter \sigma, clear numerical evidences on the validity of the proposed relation have been achieved for different cases. Finally, the effect of the system size has also been analysed and an analytical expression has been proposed, which is corroborated by the numerical results.Comment: 14 pages, 3 fig

Renormalization--Group Solutions for Yukawa Potential

The self--similar renormalization group is used to obtain expressions for the spectrum of the Hamiltonian with the Yukawa potential. The critical screening parameter above which there are no bound states is also obtained by this method. The approach presented illustrates that one can achieve good accuracy without involving extensive numerical calculations, but invoking instead the renormalization--group techniques.Comment: 1 file, 12 pages, RevTe