Giordano Franceschini

Amateur football pitches: Mechanical properties of the natural ground and of different artificial turf infills and their biomechanical implications

Abstract Artificial turf is being used more and more often. It is more available than natural turf for use, requires much less maintenance and new products are able to comply with sport performance and athletes’ safety. The purpose of this paper is to compare the mechanical and biomechanical responses of two different artificial turf infills (styrene butadiene rubber, from granulated vehicle tires, and thermoplastic rubber granules) and to compare them to the performance of natural fields where amateurs play (beaten earth, substantially). Three mechanical parameters have been calculated from laboratory tests: energy storage, energy losses and surface traction coefficient; results have been correlated with peak accelerations recorded on an instrumented athlete, on the field. The natural ground proved to be stiffer (−15% penetration depth for a given load), and to have a lower dynamic traction coefficient (−48%); the different kinds of infill showed significantly different stiffnesses (varying by more than 23%) and damping behaviour (varying by more than 31%). In running, peak vertical accelerations were lowest in the artificial ground with thermoplastic rubber granules, while, in slalom, both artificial grounds produced higher horizontal peak accelerations compared to the natural ground. Results are discussed in terms of their implications for athletic performance and injury risk.

Additively manufactured custom load-bearing implantable devices: Grounds for caution

Background Additive manufacturing technologies are being enthusiastically adopted by the orthopaedic community since they are providing new perspectives and new possibilities. First applications were finalised for educational purposes, pre-operative planning, and design of surgical guides; recent applications also encompass the production of implantable devices where 3D printing can bring substantial benefits such as customization, optimization, and manufacturing of very complex geometries. The conceptual smoothness of the whole process may lead to the idea that any medical practitioner can use a 3D printer and her/his imagination to design and produce novel products for personal or commercial use. Aims Outlining how the whole process presents more than one critical aspects, still demanding further research in order to allow a safe application of this technology for fully-custom design, in particular confining attention to orthopaedic/orthodontic prostheses defined as components responding mainly to a structural function. Methods Current knowledge of mechanical properties of additively manufactured components has been examined along with reasons why the behaviour of these components might differ from traditionally manufactured components. The structural information still missing for mechanical design is outlined. Results Mechanical properties of additively manufactured components are not completely known, and especially fatigue limit needs to be examined further. Conclusion At the present stage, with reference to load-bearing implants subjected to many loading cycles, the indication of custom-made additively manufactured medical devices should be restricted to the cases with no viable alternative.

Rider–handlebar injury in two-wheel frontal collisions

This work analyses blunt abdominal trauma produced by driver-handlebar collision, in low speed two-wheel accidents. A simplified dynamic model is introduced, whose parameters have been estimated on the basis of cadaver tests. This model allows calculating the peak impact force and the abdominal penetration depth; therefore the likelihood of occurrence of serious injuries can be estimated for different masses of contacting bodies and different speeds. Results have been checked against literature data and true-accident reports. Numerical simulations demonstrate that serious injuries (AIS>3) can occur even at low speeds (<20km/h), therefore the design of protective clothing is recommendable. The model can allow both the analysis of true accident data and the virtual testing of protective equipment in the conceptual design phase.

A new technique to improve expected aep estimation in very complex terrain

Annual Energy Production (AEP) estimation is a key issue in the development and financing of wind projects; it is fundamental not only for investment evaluation but also in defining the plant lay-out and dimensions. In order to obtain reliable results, detailed analysis of the wind conditions is needed; for wind sites in complex terrains each stage of this analysis is more difficult than in flat land because of the particular wind field conditions that are characterized by high turbulences and different shapes of the wind profile. It is not well known how these conditions affect wind turbine operation; as a result wind energy production can be different than expected. This is mainly due to the misunderstanding of the wind flow characteristics and the turbine efficiency. The present work is focused on a new method which takes into account the effect of orography in terms of available energy rather than the efficiency for the conversion. A technique to customize power curve is proposed and applied with success in the test case of Fossato di Vico (ITALY) wind farm bringing error in estimating AEP below 10%. Present work has been carried out with Anemon s.p.a. (ITALY) which provided turbine production data and participated in the measuring campaign.

ADVANCED AERODYNAMICS METHODS FOR WIND SITE SELECTION

Wind potential — in Italy — has not been completely explored yet, and many investors are still looking into the most promising sites. The interest on the exploitation of a wind site is linked to the possibility of setting up an industrial plan that yields a fast return on investment. The success of this investment depends on the following parameters: • the amount of funding to be spent (cost of the electric lines, roads, turbines, etc.); • the quality of the predicted wind flow; • the price of the electric energy produced. To select a wind site in a fast and convenient way some of the traditional methods of aerodynamics can be borrowed, such as those related to vehicle dynamics. This paper investigates and compares wind site characterization tools and methodologies based on aerodynamics. Simulations and experimental activities were performed in geographical sites located in the center of Italy, where the complex orography requires efficient methods for site characterization and selection, with the aim of speeding up the start-up of wind turbine installations.Copyright

Learning curves of elite car racers

This work is focused on racing cars driver’s training. Nine different tracks are considered and six drivers. Each driver drives on every track and performs consecutive trial sessions on each track; each session is made of various laps, and lap times are fitted using an exponential model, yielding an estimate of the initial performance, the learning constant, and the asymptotic performance. According to results, the learning curve varies significantly among pilots and among tracks; all pilots reach their session asymptotic performance in less than nine laps. The asymptotic performance in consecutive trial sessions improves significantly, and it is strongly correlated to the initial session performance (r2 > 0.99). As a conclusion, it is more profitable to perform separated sessions made of few laps (less than 10) rather than performing a smaller number of longer sessions. Whenever the initial lap time stops decreasing systematically, trial sessions should end because the asymptotic performance is not likely to improve further.

Clinical Assessment of Dental Implant Stability During Follow-Up: What Is Actually Measured, and Perspectives

The optimization of loading protocols following dental implant insertion requires setting up patient-specific protocols, customized according to the actual implant osseointegration, measured through quantitative, objective methods. Various devices for the assessment of implant stability as an indirect measure of implant osseointegration have been developed. They are analyzed here, introducing the respective physical models, outlining major advantages and critical aspects, and reporting their clinical performance. A careful discussion of underlying hypotheses is finally reported, as is a suggestion for further development of instrumentation and signal analysis.

Lower Leg Injury in Relation to Vehicle Front End

Objective: To set up a prescreening tool for vehicle front-end design, allowing numerically forecasting of the results of EC directive tests, with reference to pedestrian lower leg impact. Methods: A numerical legform model has been developed and certified according to EC directive. The frontal end of the vehicle has been simulated through a lumped-parameters model, having considered the predesign stage when the target overall behavior is being established. The stiffness behaviors of the bumper and of the spoiler have been estimated by means of more detailed numerical models. A parametric analysis has been performed to outline the effects of bumper and spoiler stiffness, bumper vertical height, and the longitudinal distance between the spoiler and the bumper. An analytical model has been introduced to predict tibial acceleration, knee shear displacement, and knee lateral bending, given the bumper and spoiler characteristics as input. Results:The parametric analysis has demonstrated that bumper stiffness, bumper profile height, and spoiler stiffness do have an impact on knee lateral bending, knee shear displacement, and peak tibial acceleration. Increasing bumper stiffness can result in higher knee bending, knee shear displacement, and peak tibial acceleration. Increasing bumper profile height produces lower knee bending and shear displacement. Increasing spoiler stiffness can determine higher knee shear displacement and peak tibial acceleration but lower knee bending. Spoiler stiffness and position have a strong correlation: higher bumper stiffness needs to be coupled to a moved forward spoiler position. The mechanical responses of the spoiler and of the bumper can be assumed to be linear: the softening behavior of the expanded polypropylene foam balances the hardening behavior of the fascia (due to contact area increase). The predictive model is well correlated to experimental findings (R 2 > 0.74) Conclusions: This simplified computer model can be used as a prescreening design tool to demonstrate general vehicle front-end design trade-offs and provide approximate results without physical testing.

The Umbria Region Wind Atlas

Wind power distribution is characterized by a strong degree of variability both in temporal terms and in spatial terms in relationship to the orography, to the superficial roughness and the climatology conditions. For this reason an analysis of wind potential cannot exclude field measurements in the most meaningful points. A preliminary estimation of the distribution of the wind resource can be performed through a combined analysis of the orography and the observation of sign on the vegetation. Numerical modeling combined with field data collection can be useful for the definition of wind energy potential over wide territories. Present work is focused on the selection of the best methodology for the elaboration of the Umbria Region wind atlas; after choosing of the most reliable wind model and the input and output data, several simulations have been performed to calculate the regional wind energy potential. Results demonstrate the importance in using fluid dynamics wind models and digital terrain models at high resolution for domains preparation; this work has been used in the elaboration of the Umbria Region Energy Plan. I. Introduction ncreasing interest in the exploitation of renewable energy has made it necessary to characterize wind energy potential over wide areas to select the most interesting sites. Considering the variations in wind speed in mountainous areas, field measurements are always required in a wind farm project; anemometer data can be supported by other methodologies in the development of regional wind maps. Temporal variation of wind resource is usually treated by statistics procedures, spatial variation is much more difficult to understand and is fundamental in selecting the best wind sites. Preliminarily the distribution of wind potential can be obtained from detailed analysis of the orography conformation combined with the observation of the vegetation 1 . The most meaningful anemometer data can be used for a quantitative estimation of windiness through numerical models. Together with the growth of wind energy conversion systems several techniques have been formulated for wind numerical estimation over a domain. In present work the modeling technique most suitable for Umbria Region was selected so that atlas was elaborated with the following items: first screening based on anemometer data, orography characteristics and vegetation (resulting in the selection of 42 wind sites within the Umbria Region); In depth analysis (through numerical model) of the most interesting areas which are not affected by restrictions; comparison and validation of results with the Italian Wind Atlas 2 .