Mechanical reliability,how do we advance?

The development of theory and practice for electronic and mechanical reliability is described, and mechanical reliability is seen to be lagging in practice. Theory and practice are described for a project from conception to market feedback for mechanical as well as for electronic reliability. It is noted that for each phase theoretical and practical methods exist for mechanical as well as for electronic reliability analysis. Activities are listed which can strengthen mechanical reliability theory and practice.     

Quality analysis of scalable video coding on unstable transmissions

This paper presents a study of quality on scalable video sequences coded using the scalable extension of the H.264 standard (SVC). A group of experiments was performed to measure, primarily, the effects that transmission instability has in the quality of the videos and the relationship among three scalability methods (spatial, temporal and quality) in terms of quality. A set of experiments was performed to measure the subjective quality using the ACR-HRR methodology and recommendations from ITU-R Rec. BT.500 and ITU-T Rec. P.910. The results show that the amount of instability is not as important as just the presence of instability, that video quality can be deteriorated due to instability and that temporal scalability usually produces videos with worse quality than spatial and quality scalabilities.     

A model approach to assess the long-term trends of indirect photochemistry in lake water. The case of Lake Maggiore (NW Italy)

A model-based approach is here developed and applied to predict the long-term trends of indirect photochemical processes in the surface layer (5 m water depth) of Lake Maggiore, NW Italy. For this lake, time series of the main parameters of photochemical importance that cover almost two decades are available. As a way to assess the relevant photochemical reactions, the modelled steady-state concentrations of important photogenerated transients (^•OH, ³CDOM* and CO₃^-•) were taken into account. A multivariate analysis approach was adopted to have an overview of the system, to emphasise relationships among chemical, photochemical and seasonal variables, and to highlight annual and long-term trends. Over the considered time period, because of the decrease of the dissolved organic carbon (DOC) content of water and of the increase of alkalinity, a significant increase is predicted for the steady-state concentrations of the radicals ^•OH and CO₃^−•. Therefore, the photochemical degradation processes that involve the two radical species would be enhanced. Another issue of potential photochemical importance is related to the winter maxima of nitrate (a photochemical ^•OH source) and the summer maxima of DOC (^•OH sink and ³CDOM* source) in the lake water under consideration. From the combination of sunlight irradiance and chemical composition data, one predicts that the processes involving ^•OH and CO₃^−• would be most important in spring, while the reactions involving ³CDOM* would be most important in summer.     

Chemical and optical phototransformation of dissolved organic matter

Dissolved organic matter represents the main reservoir of organic carbon in most aquatic ecosystems. In the present study, we determined the optical changes and the quantum yields of transient species formation for chromophoric dissolved organic matter (CDOM) samples undergoing photodegradation. The results show that the triplet states ³CDOM^∗ are potentially key players in CDOM photodegradation and that such transformations are strongly influenced by small differences in CDOM sources and sinks. In contrast, OH radicals are very unlikely to play a key role in phototransformation. These results represent an important first step in combining optical and transient species analyses to understand photodegradation processes of dissolved organic matter.     

Influence of substituents in electrochemical and conducting properties of polyaniline derivatives and multi walled carbon nanotubes nanocomposites

Poly(o-methoxyaniline) and poly(o-methylaniline) were synthesized by oxidative polymerization in the presence of multi-walled carbon nanotubes (MWNT) for the fabrication of chloroform processable nanocomposites obtained by embedding MWNT in the polymer matrix without the formation of covalent bonds. The study of pressure-area isotherms highlighted different substituents along the aromatic rings affected the packing grade of macromolecules when spreading on different subphases in relation to the associated sterical hindrance. The presence of MWNT inside the polymer matrix showed to favor a more stretched conformation of macromolecules with a subsequent increment of area/molecule values with respect to the corresponding pure conducting polymers. Furthermore, the sterical hindrance affected the nanocomposite electrochemical properties and conducting polymers containing less hindering substituents along the aromatic rings turned out to be faster electrochemical systems. Less hindering substituents were also able to enhance the conducting properties of nanocomposite materials in association with MWNT.     

Indirect Determination of the Piezospectroscopic Coefficients of Ceria-Stabilized Tetragonal Zirconia Polycrystals

A method is proposed for the indirect determination of the stress dependence (expressed as piezospectroscopic (PS) coefficients) of spectroscopic bands of ceramic materials/phases. This method is based on the intimate mixture (intimate at the microstructural, grain-size level) of two phases/materials when the stress in one is independently known; it is used to determine the PS coefficients of the most intense Raman bands in ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP). Different amounts of Ce-TZP were mixed with alumina and the composite pellets sintered; subsequently, the stress in alumina was determined through the PS coefficient of its R2 luminescence band and the stress in Ce-TZP derived from the static equilibrium condition. The frequency shifts of each Raman band of Ce-TZP have been plotted against the stress and the slopes provide the PS coefficients. The method has the advantage of not requiring any type of loading device (i.e., diamond anvil-cell, bending jig). Finally, the limits are also discussed, the most important one being the requirement of immiscibility of the two materials/phases.     

Mechanical behaviour modelling of a new anchor system for large diameter GFRP bars

The strong anisotropy of unidirectionally-reinforced FRP composites makes it difficult to design an efficient anchorage for measuring the tensile strength and this difficulty increases together with the cross section area of the specimen. To overcome this difficulty a new anchor system was developed for tension testing of large diameter GFRP bars in a universal testing machine. The anchor body designed and tested consists of two shells, pushed one against the other by the jaws of the testing machine, leaving an inner conical hole. The ends of the bar are provided with resin heads having the shape of the hole inside the anchor body. The present paper details the modelling investigation to verify and improve the shape and hence the performances of this anchor system. The approach adopted consists in a parametric numerical analysis that rests on the experimental data already gathered.     

Sorption of Pyrene to Two Estonian Soils

Two typical Estonian soils, Brown pseudopodzolic and Rendzina, were used for sorption studies with pyrene. The soil samples were subjected to a variety of chemical and physical tests. The specific surface area reached 3.05 m² g^?1 for Rendzina, and 0.87 m² g^?1 for Brown pseudopodzolic soil. The Rendzina type of soil was characterized also by a high organic matter content (22.9%) compared with the Brown pseudopodzolic soil (6.64%). A batch technique was used to perform all adsorption studies. K_oc values 2.7 × 10⁴ mg g^?1 for Rendzina and 4.5 × 10⁴ mg g^?1 for Brown pseudopodzolic were obtained. The results suggets that pyrene sorption behaviour could be in some instances mainly influenced by the composition of organic compounds in the soil, not so much by the overall organic matter content. Also the mineral part of the soil can have a impact to pyrene sorption through Ca-binded humic substances.