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The purpose of this research is to show that wavelets are mathematical tools capable of separating vibration data into different frequency components, allowing the study of each component with a resolution matched to its specific time scale. Wavelets have advantages over traditional Fourier methods, particularly when a signal contains sharp spikes, discontinuities, and transients.

This paper presents a brief description of wavelets and shows their application to the analysis of typical transient signals due to vibrations in a steel‐reinforced concrete beam.

The research clearly shows that it is possible to evaluate modes and components separately by using the wavelet analysis.

The beam analysed can be used as a simple model of other more complicated structures, such as bridges and other high scale civil engineering constructions, where vibration analysis is a key issue for maintenance and failure assessments, thus representing an alternative mathematical tool for condition monitoring.

The wear behavior of a novel composite aluminum‐graphite composite prepared by simple powder metallurgy techniques is reported. Graphite powders were surface‐treated with copper to activate the powder surface and to improve the wettability of the graphite surface. The mixed Al‐C (7 percent, 5 percent, 3 percent, 1 percent y 0.5 percent C weight content) powders <100 μm were pressed at room conditions and then heat‐treated at 600°C. The tests showed improvements in wear resistance as the graphite content decreases, achieving the optimal behavior at 1 percent content.

The corrosion performance of ceramic films of SiO₂‐Al₂O₃ prepared by the sol‐gel processing of organometallic compounds and deposited by dip‐coating technique on 1008 steel foils has been evaluated. Two kinds of procedures were developed to produce the sol‐gel coatings. The influence of the coatings on the chemical corrosion of the substrate has been measured by using potentiodynamical polarization curves in 0.5 M H₂SO₄ and 1 M HCl solutions at room temperature. Sol‐B showed the best behaviour in protective corrosion, in addition to the fact that the number of applications does not influence the resistant corrosion. Protection of coatings was limited by the growing of film cracking due to residual stress between coating and substrate. The results were supplemented by SEM analysis.

The purpose of this paper is to report a study of microbiological influenced corrosion (MIC) of copper due to bacteria strains isolated from potable water pipes and oxidation lagoons using electrochemical noise (EN) analysis and scanning electron microscopy (SEM).

Bacteria strains isolated from copper surfaces of potable water pipes and from oxidation lagoons were identified, based on the 16S rDNA gene sequence analysis. Corrosion studies were undertaken over a period of six weeks, placing copper electrodes inside an LB culture media with and without bacteria. The corrosion resistance was obtained using EN analysis. In all the cases, the corrosion type was identified. SEM images of the copper electrodes were taken to evaluate the surface condition.

The bacteria strains identified were: Pantoea agglomerans, Alcaligenes faecalis, Bacillus cereus, Brucellaceae bacterium, Enterobacter cloacae, Delftia tsuruhatensis, and Pseudochrobactrum asaccharolyticum. EN analysis gave noise resistance values in the range 1,036‐5,040 Ωcm² for the control samples and in the range of 2,336‐22,573 Ωcm² for samples that had been inoculated with bacteria. It was found that a decrease in the rate of corrosion took place due to the development of a biofilm by the microorganisms on the copper surface. SEM images corroborated the presence of the biofilm on the copper electrodes.

The isolated bacteria strain reduced the rate of corrosion on the copper electrodes, as shown by the SEM images and EN analysis results, due to the formation of a biofilm that can act as an anticorrosive coating.

Even though MIC is a known phenomenon, it has not been reported that isolated bacteria strains can reduce corrosion on the surface of copper potable water pipes and in oxidation lagoons.

A spatial micropositioning device for the alignment of substrates employed in thin films synthesis by the so‐called combustion flame technique, utilized for producing thin diamond films, was designed and built. A combination of mechanical, electronic and optical components allowed, with high accuracy, the alignment of the substrate during the film deposition process. The system always kept the substrate surface perpendicular to the oxy‐acetylene flame produced by the torch, in such a way that each deposited film consists of a circular disk, approximately 4mm in diameter and 20μm thick, over the region of the substrate that intersects the inner acetylene‐rich flame. The films obtained under these conditions showed low nitrogen content, as confirmed by the Fourier‐transform infrared spectrum (FTIR), which is also presented. Accordingly, the present work represents the first step towards a complete automation of the combustion diamond deposition technique, aiming to design an operating industrial‐level technology.

The purpose of this paper is to know the effect of graphite particles distribution on wear behavior of ingots of an aluminium‐graphite, Al‐Gr_(p), composite.

By SEM and optical microscope, it was observed that the graphite particles were entrapped and placed at different regions of the aluminium ingots as they were cooled under three different cooling rate during solidification, mantaining 4.5 wt% of graphite content. Size of particles entrapped, were measured at three different region of the ingots.

Smaller size of graphite particles distribution were found in regions where the cooling rate was higher, while bigger size were located in regions where the cooling rate was lower, this phenomenon could improve the wear resistant performance found in ingots containing smaller graphite particles.

A suitable dispersion of small graphite particles entrapped into a fine structure of the aluminium‐graphite composite as a result of high cooling rate while casting, could be extended to another processes for future researches.

This material could be used in sliding mechanical pieces improved by a uniform dispersion of small particles inside.

The improvement of wear behavior could be succeeded by dispersion of smaller graphite particles into the ingots, influenced by a higher cooling rate, and maintaining the weight fraction content of reinforcement.

The study of pressure‐volume‐temperature (PVT) process is necessary to understand the physical behaviour of materials. This paper seeks to develop a simulation procedure to predict phase behaviour.

The procedure consisted of the application of a thermo‐mechanical nonlinear model that simulated the behavior of the test sample in the PVT apparatus. Software Ansys was used for modeling this case, making a subroutine in APDL language. The real time data of the experimental procedure in PVT apparatus were applied in the computer simulation, that is the real time of application of pressure and heating scaling of the sample were taken into account. A specific case was simulated and its results compared with those obtained from the real experimental test. In order to evaluate phase changes, enthalpy was considered using an approximated expression described in the paper.

Results obtained from the simulation were compared with the resulting isobaric graphics of the experimental test. Results show a good correlation, obtaining in addition stress‐strain behavior of the sample. This simulation procedure allows one in a simple way to vary the properties and characteristics of the sample. This makes the computer simulation a useful tool together with the experimental test, in the development of novel materials.

Results of the numerical simulation are based on the properties and characteristics of the sample. In this study, real data of the material were used; however, some others had to be assumed based on references on this topic.

The coupled field analysis and the subroutine built in an Ansys environment are of a general purpose applicable to many kinds of material without practical limitations but getting a priori the required data and properties needed for running the simulation test.

Computer simulation of PVT process is not a common procedure – the experimental study of the material is mainly the procedure used to define the stated equations of a material and for knowing their phase changes. Computer simulation is a procedure that provides other important features of the material that the experimental study cannot produce simultaneously.

Aluminium‐based matrix composites were prepared by infiltration with an ammoniacal zirconium chelate within an Al matrix synthesized via aluminium powder compactation. Based on differential thermal analysis, Fourier transformed infrared, X‐ray diffraction, and scanning electron microscopy, we confirm the reaction sequence to obtain the tetramer, the phase transformation sequence within the Al matrix, and the development of phases that leads to the synthesis of the Al‐ZrO₂ composite.

Social and task groups need a few high-status members who can be leaders and trend setters, and many more lower-status members who can follow and contribute work without challenging the group's direction (Caporael (1997). Personality and Social Psychology Review, 1, 276–298; Caporael & Baron (1997). In: J. Simpson, & D. Kenrick (Eds), Evolutionary social psychology (pp. 317–343). Hillsdale, NJ: Lawrence Erlbaum; Brewer (1997). In: C. McGarty, & S.A. Haslam (Eds), The message of social psychology: Perspectives on mind in society (pp. 54–62). Malden, MA: Blackwell). When groups come together without a priori status differentiation, a status hierarchy must be implemented; however, if the new members are too homogeneously status seeking, then it is not clear what will result. We argue that hierarchy will develop even in uniformly status-seeking groups, and that the social context and members’ relational characteristics – specifically, the degree to which they are group oriented rather than self-serving – will predict which status seekers succeed in gaining status. We discuss why and how a “status sorting” process will occur to award status to a few members and withhold it from most, and the consequences of this process for those who are sorted downward.

Aluminium alloys are frequently applied in automotive and other industries, since they provide mass reduction. Besides positive effects, aluminium alloys have their shortcomings reflected, first of all, in inappropriate tribological properties of these materials. The aim of this research was to enable the production of cheap aluminium alloy matrix composite with favourable combination of structural, mechanical and tribological properties, focusing on the tribological behaviour.

The A356 Al-Si alloy was used as a matrix for producing metal matrix composites in compocasting process. Three different materials, in form of particles, were added to the matrix (Al₂O₃, SiC and graphite). Hardness and tribological properties (wear, friction and wear mechanism) of heat-treated (T6) samples were examined and compared. Tribological tests were carried out on ball-on-block tribometer under dry sliding conditions. Sliding was linear (reciprocating). Counter body was alumina ball. Average velocity was 0.038 m/s (max. 0.06 m/s), sliding distance was 500 m and normal load was 1 N.

The effect of two different ceramic particles and graphite particles on tribological properties of obtained composites was evaluated. Wear resistance of composites reinforced with SiC particles was higher and coefficient of friction was lower compared to the composite reinforced with Al₂O₃ particles. A dual hybrid composite (with SiC and graphite particles) showed the lowest value of wear rate and friction coefficient. Dominant wear mechanism for all tested material was adhesion.

It seems useful to continue the work on developing hybrid composites containing soft graphite particles with A356 Al-Si alloy as matrix. The major task should be to improve particles distribution (especially with higher graphite content) and to explore tribological behaviour in diverse working conditions.

Particulate composites with A356 aluminium alloy as a matrix produced in compocasting process using ceramic particles (Al₂O₃, SiC) were investigated in many researches, but there are only few detailed analyses of dual composites (with the addition of ceramic and graphite particles). In some previous studies, it was shown that compocasting process, as relatively cheap technology, can obtain good structural and mechanical characteristics of composites. In this study, it was shown that even a low graphite content, under specified conditions, can improve tribological properties.