The role of lubricant feed temperature on the performance of twin groove journal bearings : an experimental study

An experimental assessment of the influence of lubricant feed temperature (Tf) on the behaviour of twin groove hydrodynamic journal bearings has been undertaken. Several loads, shaft speeds and bearing geometries were tested under constant lubricant feed pressure (pf), while Tf took four different values between 29ºC and 58ºC. It was found that the increase of Tf has an effect in bearing performance which is analogous in many ways to the effect of the increase in eccentricity: increase in lubricant flow rate (especially in the low eccentricity range), in outlet temperature (Tout) and in maximum bush temperature (Tmax). Nevertheless, the latter increase was lower than the corresponding increase in Tf. Also, in the high eccentricity range the increase in flow rate due to the increase of Tf could be deceiving in the sense that the additional flow was supplied mainly to the inactive region of the bearing (the unloaded land of the bearing).Fundação para a Ciência e a Tecnologia (FCT

A systematic review of the use of the Satiety Quotient

The satiating efficiency of food has been increasingly quantified using the Satiety Quotient (SQ). The SQ integrates both the energy content of food ingested during a meal and the associated change in appetite sensations. This systematic review examines the available evidence regarding its methodological use and clinical utility. A literature search was conducted in 6 databases considering studies from 1900 to April 2020 that used SQ in adults, adolescents and children. All study designs were included. From the initial 495 references found, 52 were included. Of the studies included, 33 were acute studies (29 in adults and 4 in adolescents) and 19 were longitudinal studies in adults. A high methodological heterogeneity in the application of the SQ was observed between studies. Five main utilizations of the SQ were identified: its association with i) energy intake; ii) anthropometric variables; iii) energy expenditure/physical activity; iv) sleep quality and quantity; as well as v) to classify individuals by their satiety responsiveness (i.e. low and high satiety phenotypes). Altogether, the studies suggest the SQ as an interesting clinical tool regarding the satiety responsiveness to a meal and its changes in responses to weight loss in adults. The SQ might be a reliable clinical indicator in adults when it comes to both obesity prevention and treatment. There is a need for more standardized use of the SQ in addition to further studies to investigate its validity in different contexts and populations, especially among children and adolescents

The work on hydrodynamic journal bearings carried out at Minho University in the last 30 years

The hydrodynamic journal bearing is still one of the most geometrically simple mechanical components, yet highly reliable and efficient and, above all, unique in what concerns to heavy duty – high load, high speed – support of rotating shafts. Analytical studies, not only to understand the physical basis of its performance, but also to develop practical tools for an expedite design, as well as to assure its reliability and improved efficiency, were object of the early developments in fluids’ hydrodynamic sciences, since the late XIX century, and are still been refined and improved on the XXI century. Historical marks can be flagged as (i) simplified analytical resolutions of the hydrodynamic pressure distribution; (ii) computerized iterative resolution of the full pressure development equations; (iii) introduction of the lubricant feeding conditions; (iv) analysis of the thermal aspects and its influence on viscosity; (v) localized aspects of fluid flow, due to thermal/viscous phenomena and geometrical particularities. This evolution led to increased accuracy on the performance predictions and to safer and higher efficiency of the designed components. On the other hand, analysis became more specific in use and, particularly with the introduction of the thermo-hydrodynamic analysis, led to the need of ‘tailored’ solutions to a given set of specific conditions. As a consequence, methods lost much of their ‘universality’ and ease of use to the common and sporadic designer. This work intents to make a first evaluation of the response of three prediction methods – a commercial and widely used isothermal approach and an isothermal and a thermohydrodynamic procedures, these former developed at UMinho over the last years – in an attempt to highlight the variability of the predictions of the main performance parameters by the use of simpler and rapid methods, when compared with those based on more complex and accurate analysis, and their eventual influence on an efficient and reliable design solution

Influence des conditions d’alimentation sur l’amélioration des performances et la réduction du frottement dans les paliers

The performance of hydrodynamic journal bearings is significantly affected by the conditions under which the lubricant is fed to the bearing. However, many conventional analyses are not prepared to suitably incorporate these parameters and their effect on bearing performance, due to the over-simplified way they treat them. A thermohydrodynamic analysis suitable for conveniently deal with lubricant feeding conditions is now presented. It couples the numerical solution of the generalized Reynolds equation, the energy equations within the lubricant film and the heat transfer within the bush body. Special attention has been given to the treatment of the phenomena taking place within the grooves and in their vicinity, as well as to the ruptured film region. The effect that lubricant feed pressure and temperature, groove length ratio, groove width ratio and groove number (single / twin) have on bearing performance has been analyzed for a broad range of conditions. The results were found to be in good agreement with experimental published results and the robustness of the model to suitably treat these phenomena has been confirmed. It was found that a careful tuning of the feeding conditions may indeed improve bearing performance.Les performances des paliers lisses hydrodynamiques sont significativement affectées par les conditions dans lesquelles le lubrifiant est introduit dans le palier. Cependant, de nombreuses analyses classiques ne sont pas prêtes à intégrer convenablement ces paramètres et leurs effets sur les performances des paliers, en raison de la façon trop simplifiée avec laquelle ils les traitent. Une analyse thermohydrodynamique appropriée pour traiter convenablement les conditions d'alimentation de lubrifiant est maintenant présenté. Elle intègre la solution numérique simultanée des équations de Reynolds généralisée, de l'énergie dans le film lubrifiant et de la de chaleur dans le coussinet. Une attention particulière a été portée pour le traitement des phénomènes se produisant dans les rainures et dans leur voisinage, ainsi que dans la région de rupture du film. L'influence de la pression et de la température d'alimentation en lubrifiant, de la longueur et largeur de la rainure et du nombre de rainures (simple ou double) sur les performances du palier a été analysée pour un large éventail de conditions. Les résultats numériques obtenus sont en bon accord avec ceux issus de la littérature expérimentale et la robustesse du modèle à traiter convenablement ces phénomènes a pu être confirmée. Il a été constaté qu'un réglage minutieux des conditions d'alimentation peut effectivement améliorer les performances.FCT - POCTI/EME/39202/2001 & Postdoctoral grant SFRH/BPD/89553/201

Thermohydrodynamic modelling of journal bearings under varying load angle and negative groove flow rate

The performance of hydrodynamic journal bearings is affected by the conditions under which the lubricant is fed to the bearing gap. Axial grooves are often used and, depending on their location relatively to the load line, they might substantially interfere with the hydrodynamic pressure generation and the thermal behaviour of the bearing. However, many of the existing tools for predicting bearing performance are not able to suitably predict bearing behaviour under varying load angle given the oversimplified way under which they treat lubricant feeding conditions. The present work proposes a detailed Thermohydrodynamic approach which realistically incorporates these conditions into the bearing analysis. Special care is put on the mass and energy-conserving models of the ruptured film region and on a detailed treatment of lubricant mixing within the vicinity of grooves. This includes the first full modelling of the effect of negative flow rate in a groove, a phenomenon originally described experimentally in detail by the authors in previous publications, and which happens for a broad range of load/groove angles. An extensive investigation on the influence of loading direction on the performance of twin groove journal bearings has been performed. This parameter is found to affect deeply all major performance parameters due to the interference of groove regions in the hydrodynamic pressure generation and in the flow rates at each groove.Fundação para a Ciência e a Tecnologia (FCT

SmartTools: a generator of interactive environments tools

SmartTools is a development environment generator that provides a structure editor and semantic tools as main features. The well-known visitor pattern technique is commonly used for designing semantic analysis, it has been automated and extended. SmartTools is easy to use thanks to its graphical user interface designed with the Java Swing APIs. It is built with an open architecture convinient for a partial or total integration of SmartTools in other environments. It makes the addition of new software components in SmartTools easy. As a result of the modular architecture, we built a distributed instance of SmartTools which required minimal effort. Being open to the XML technologies offers all the features of Smart Tools to any language defined with those technologies. But most of all, with its open architecture, SmartTools takes advantage of all the developments made around those technologies, like DOM, through the XML APIs. The fast development of SmartTools (which is a young project, one year old) validates our choices of being open and generic. The main goal of this tool is to provide help and support for designing software development environments for programming languages as well as application languages defined with XML technologies

E-MSD: improving data deposition and structure quality

The Macromolecular Structure Database (MSD) () [H. Boutselakis, D. Dimitropoulos, J. Fillon, A. Golovin, K. Henrick, A. Hussain, J. Ionides, M. John, P. A. Keller, E. Krissinel et al. (2003) E-MSD: the European Bioinformatics Institute Macromolecular Structure Database. Nucleic Acids Res., 31, 458–462.] group is one of the three partners in the worldwide Protein DataBank (wwPDB), the consortium entrusted with the collation, maintenance and distribution of the global repository of macromolecular structure data [H. Berman, K. Henrick and H. Nakamura (2003) Announcing the worldwide Protein Data Bank. Nature Struct. Biol., 10, 980.]. Since its inception, the MSD group has worked with partners around the world to improve the quality of PDB data, through a clean up programme that addresses inconsistencies and inaccuracies in the legacy archive. The improvements in data quality in the legacy archive have been achieved largely through the creation of a unified data archive, in the form of a relational database that stores all of the data in the wwPDB. The three partners are working towards improving the tools and methods for the deposition of new data by the community at large. The implementation of the MSD database, together with the parallel development of improved tools and methodologies for data harvesting, validation and archival, has lead to significant improvements in the quality of data that enters the archive. Through this and related projects in the NMR and EM realms the MSD continues to improve the quality of publicly available structural data

Investigation of the superelastic behavior of a Ti-16Zr-13Nb-2Sn sputtered film by nanoindentation

A new Ti-16Zr-13Nb-2Sn superelastic film incorporating beta-stabilizing and highly biocompatible elements was elaborated by magnetron sputtering. The morphological, crystallographic and microstructural characteristics of the obtained films were studied by scanning electron microscopy, atomic force microscopy, X-ray diffraction, and transmission electron microscopy. Superelastic response of the film was investigated at local scale by nano-indentation using both spherical and Berkovich indenters. The sputter-deposited film revealed nanograined beta microstructure with preferential growth orientation along [110] direction and excellent superelastic recovery at room temperature. Special attention was paid to the indenter geometry influencing reliable evaluation of the superelastic nature of the film. Evolution of the deformation mechanisms during nanoindentation at increasing depths was rationalized by the calculated representative strain beneath the indenting tips and is discussed in this work

Surface water temperature, salinity, and density changes in the northeast Atlantic during the last 45,000 years: Heinrich events, deep water formation, and climatic rebounds

We developed a new method to calculate sea surface salinities (SSS) and densities (SSD) from planktonic foraminiferal delta(18)O and sea surface temperatures (SST) as determined from planktonic foraminiferal species abundances. SST, SSS, and SSD records were calculated for the last 45,000 years for Biogeochemical Oceanic Flux Study (BOFS) cores 5K and 8K recovered from the northeast Atlantic. The strongest feature is the dramatic drop in all three parameters during the Heinrich ''ice-rafting'' events. We modelled the possibility of deepwater formation in the northeast Atlantic from the SSD records, by assuming that the surface waters at our sites cooled as they flowed further north. Comparison with modelled North Atlantic deepwater densities indicates that there could have been periods of deepwater formation between 45,000 and 30,000 C-14 years B.P. (interrupted by iceberg meltwater input of Heinrich event 3 and 4, at 27,000 and 38,000 C-14 years B.P.) and during the Holocene. No amount of cooling in the northeast Atlantic between 30,000 and 13,000 years could cause deep water to form, because of the low salinities resulting from the high meltwater inputs from icebergs. Our records indicate that after each Heinrich event there were periods of climatic rebound, with milder conditions persisting for up to 2000 years, as indicated by the presence of warmer and more saline water masses. After these warm periods conditions returned to average glacial levels. These short term cold and warm episodes in the northeast Atlantic ate superimposed on the general trend towards colder conditions of the Last Glacial Maximum (LGM). Heinrich event 1 appears to be unique as it occurs as insolation rose and was coeval with the initial melting of the Fennoscandian ice sheet. We propose that meltwater input of Heinrich event 1 significantly reduced North Atlantic Deep Water formation reducing the heat exchange between the low and high latitudes, thus delaying deglaciation by about 1500 radiocarbon years (2000 calendar years)