Adaptation of the plasma process with automatic wire feeding for recovery of surfaces by automated welding

Damaged surfaces are normally recovered by means of processes of welding; they normally have complex geometries and are located in positions that are unfavourable for welding. Automated welding is the natural alternative as it presents advantages when compared with the manual process, such as reductions in the time and total cost of the recovery, better control of the geometry of the recovered surface, better uniformity and welding quality. Automated welding using the plasma process with automatic wire feed, although it provides excellent geometric and surface quality for the deposits, a significant reduction in welding defects and an absence of spatter, is very sensitive to variations in the torch–piece distance and to changes of welding position. In this context, the present work deals with an analysis of the changes made to the position of the wire in relation to the electric arc and the weld bead, to the orientation of the torch in relation to the surface to be welded and to the welding parameters that make the plasma welding process more robust due to geometric alterations to the surface to be welded. The practical results achieved in the most critical situations, from the point of view of welding damaged surfaces, are presented with the objective of validating the changes proposed for the fed plasma process.     

Analogue CMOS prototype vision chip with fuzzy Kohonen network processing for grey level image segmentation

In this paper, the design and realization of an analogue CMOS prototype vision chip for grey level image segmentation for two regions is presented with Fuzzy-Kohonen Network processing as an alternative to neuromorphic and cellular neural networks approaches for vision chips. This alternative is due to the compensation that fuzziness gives in order to utilize simple analogue circuits with small layout areas instead of robust analogue circuits with bigger layout areas required. This helps to relieve the signal to noise ratio when crisp computations are present. The vision chip is based on the elaboration of an array of basic cells that work simultaneously. Every basic cell has embedded one vertical phototransistor and one network implemented under weak inversion techniques. The chip processes one image in 35 us with consumption of 733 uW per cell, signal to noise ratio of 43?dB and dynamic range of 49?dB.     

Influence of taste disorders on dietary behaviors in cancer patients under chemotherapy

Objectives  

To determine the relationship between energy and nutrient consumption with chemosensory changes in cancer patients under chemotherapy.     

A novel CMOS process compatible high performance parallel-stacked RF spiral inductor

In this study, a deep-submicron CMOS process compatible parallel-stacked inductor has been successfully developed. We use the mature CMOS compatible technology and air gap structure to reduce substrate losses and parallel-stacked structure to reduce the resistance, thus can promote the Q factor. Experimental results evidence that by using the parallel-stacked structure, the chip area can be reduced significantly for the issue of continuing reduction of the chip size. Furthermore, the resistance can be reduced by using the parallel-stacked structure and thus results in an obviously improving of the Q at low frequency. The measured peak Q and peak-Q frequency with the parallel metal layer of M8//M7//M6//M5 are 7.06 and 1.8 GHz, thus enhancing its applications for higher frequency RF IC. Therefore, the developed deep-submicron CMOS process compatible parallel-stacked inductor is suitable for CMOS RF integrated circuit applications.     

Optimizing the evolution of strength for lime-stabilized rammed soil

In the present study,unconfined compressive strength(q_u)values of two lime-treated soils(soil 1 and 2)with curing times of 28 d,90 d and 360 d were optimized.The influence of void/lime ratio was represented by the porosity/volumetric lime content ratio(η/L_(iv))as the main parameter.η/L_(iv) represents the volume of void influenced by compaction effort and lime volume.The evolution of qu was analyzed for each soil using the coefficient of determination as the optimization parameter.Aiming at providing adjustments to the mechanical resistance values,the η/L_(iv) parameter was modified to η/L_(iv)~C using the adjustment exponent C(to make q_u-η/L_(iv) variation rates compatible).The results show that with the decrease of η/L_(iv)~C.qu increases potentially and the optimized values of C were 0.14-0.18.The mechanical resistance data show similar trends between q_u and η/L_(iv)~C for the studied silty soil-ground lime mixtures,which were cured at ambient temperature(23±2)℃ with different curing times of 28—360 d.Finally,optimized equations were presented using the normalized strengths and the proposed optimization model,which show 6% error and 95% acceptability on average.     

The influence of positive polarity time on GTAW AC of aluminium

In this work, experiments were carried out to determine the welding behaviour of aluminium 1200 based on an increase in the activation time of the positive polarity for tungsten inert gas AC welding of this metal. To achieve this objective, a series of experiments was developed, in such a way that the intensity of the electrical current in the positive and negative polarities was the same; only the duration times in each polarity were modified. During the experiments, the current and voltage signals were acquired. In this way, the arc voltage and potential could be determined for each condition tested. In terms of the fusion behaviour, an increase in penetration and in welded areas was verified to the extent that longer positive polarity times were used. This behaviour is different from that commonly indicated in the literature about welding processes with non-consumable electrodes, which suggests a reduction in penetration with an increase in the positive polarity activation time. However, this trend grows constantly during the experiments from a determined point, where the positive polarity activity times are greater than 4.0 ms in a total period of 20.0 ms. The use of a minimum positive polarity time (1.3 ms) was shown to be effective for cathode cleaning, as it produced welds with satisfactory fusion characteristics and with minimum wear to the tungsten electrode. The good fusion capacity obtained in welds produced with long positive polarity times was attributed to phenomena arising from the emission of electrons due to the field effect that occurs during the positive electrode phases.     

A Comparative Study of the 1-Hexene Hydroformylation Either Under Syngas Conditions or with Paraformaldehyde Catalyzed by Rhodium/Diphosphine Systems

In order to carry out a comparison, the hydroformylation of 1-hexene to their corresponding aldehydes (heptanal and 2-methyl-hexanal) was studied both under syngas conditions and with paraformaldehyde using the catalytic rhodium/diphosphine precatalysts; the catalytic systems were formed in situ by the addition of one or two equivalents of the corresponding diphosphine, Ph₂P(CH₂)_nPPh_2, n = 2 (dppe), 3 (dppp) and 4 (dppb), to the carbonyl complex Rh(acac)(CO)₂. For the hydroformylation reactions under syngas conditions, the more active systems were the ones containing one equivalent of the diphosphine, which produce trigonal bipyramidal species like RhH(CO)₂(diphos). The activity and selectivity of these systems strongly depend on the bite angle of the ligand: when the bite angle increases both parameters are higher (dppb > dppp > dppe). Contrary to these results, for the reaction with paraformaldehyde, the systems containing two equivalents of the diphosphine ligand, which produce the cationic square planar species [Rh (diphos)₂]⁺, were more active than those containing one equivalent; the reaction rate decreases with the enlargement of the carbon chain of the bridge between the two phosphorous atoms of the diphosphine (dppe > dppp > dppb). These results may be explained by a higher steric effect on the metal center, which probably produces a decreasing of the rate of the CH₂O oxidative addition reactions. For both reactions, these effects were explained through DFT calculations of the corresponding resting states.     

Cavitation erosion resistance of deposits processed by plasma transferred arc weldingArticle based on a version presented at the XXXI CONSOLDA,São Paulo,Nov 29–Dec 1 2005.

This work sets out a development of the equipment and an evaluation of the process of powder fed transferred arc plasma welding (PTA powder) with an emphasis on its utilization in coating metallic surfaces out of a flat position. After analysing the possibility of using the process in refurbishing hydraulic turbines eroded by cavitation, an analysis was made of the performance of the process and of the influence of the type of current (constant direct current and pulsed direct current) on resistance to cavitation of Stellite 6 alloy in accordance with ASTM standard G-32/92, by the indirect method. From the Stellite 6 alloy coatings deposited by the PTA process – powder using constant direct current and pulsed direct current, no significant difference was observed in the resistance to cavitation. On the other hand, the resistance to cavitation of the Stellite 6 alloy coatings obtained by the PTA powder process showed a performance higher than that of the Cavitec alloy obtained with the MIG and wire fed PTA welding processes.     

Cassava starch functional properties by etherification – hydroxypropylation

Starches are important food biopolymers with gelling properties that are well explored by the food industry for texture and physical food characteristic control. Brazil contributes to a large part of the starches produced world wide, but the modified starches used are imported and expensive. The objective of this work was to develop a hydroxypropylated starch from cassava starch, at a lower price and in conditions in accordance with Brazilian reality. Dihydroxypropylstarch (DHPS) was produced with a less expensive and less harmful substituting molecule, chloropropylene glycol. DHPS physical chemistry properties, retrogradation and micro structural characteristics were studied and compared with native corn, cassava starches and a commercial hydroxypropylated (HPS) cassava starch, with an extensive use in the food industry. DHPS showed the highest values for swelling power and viscosity, low retrogradation and higher freezing–thawing stability, compared with HPS, cassava and native corn starches. The microstructure of DHPS remained unmodified when compared with commercial HPS. Retrogradation and physical chemistry properties are superior to DHPS, which would indicate its use in industrial food production.     

Computational fretting fatigue maps for different plasticity models

This paper presents qualitative elastoplastic simulations and analyses of fretting fatigue. Three hardening constitutive models are considered, and their effects on stick–slip conditions and lifetime prediction are compared. The computational analysis consists of the estimation of the shakedown limit cycle and the fatigue prediction using Dang Van or Crossland criterion. A particular configuration, the interaction of a flat pad with rounded corners in contact with a flat substrate made, respectively, of Inconel In718 and Titanium Ti64 alloys, is studied. The shakedown state is analysed using the cyclic and ratcheting equivalent strain concepts already discussed in the literature. In the paper, different fretting maps, based on slip, shakedown and fatigue regimes, are numerically produced and analysed. A new variable, the global slip percentage, is proposed for the characterization of the stick–slip regimes. Analyses of a series of slip maps show that the different hardening models do not introduce significant changes in the stick–slip conditions. Using finite element method simulations combined with fatigue limit criteria (Dang Van and Crossland), fretting fatigue maps are qualitatively reproduced. The main contribution of this work is a comparative discussion on the influence of the hardening models complexity on such maps.