Structural analysis of a rugby wheelchair frame during field and laboratory tests

Structural analysis of a rugby wheelchair frame during field and laboratory tests with fem simulation and comparison between experimental and numerical resultsopenEmbargo per motivi di segretezza e/o di proprietà dei risultati e informazioni di enti esterni o aziende private che hanno partecipato alla realizzazione del lavoro di ricerca relativo alla tes

Reologia e dinamica di propagazione delle colate detritiche: analisi e modellazione a diversa scala

This research focuses on small scale laboratory tools to characterize the rheological behavior of the matrix (maximum diameter of sediment analyzed equal to 19 mm) of real debris flows affecting Eastern Italian Alps. The main aim is to define novel, easily reproducible and low-cost procedures that make available to a wider audience, in particular to the end users of numerical models, this kind of information. The research seeks therefore to delineate a connection between the laboratory data and the numerical models because, as mentioned by Calligaris and Zini (2012), the current main objective of debris-flow modeling is to clearly describe the input variables in order to better understand the formation of debris flow fans and to predict, mitigate or control the hazard posed by these phenomena to communities situated into the mountain areas. This research takes into account monophasic numerical models because of their widespread and proven efficiency (Rickenmann et al., 2006; Bisantino et al., 2009; Calligaris and Zini, 2012). Summarizing, the detailed aims of this research are: - Debris-flow behavior investigation through small scale laboratory tools and original and easily reproducible procedures; - Identify methodologies for applying the laboratory data to the numerical modeling and to calibrate the rheological parameters; - Verify the methodologies identified through a performance analysis of numerical simulations of real and well documented debris flows. Initially, the objectives have been pursued through a literature review focused, in particular, on the methodologies for analyzing debris-flow behaviors. In the following laboratory investigation, the results of two different tools are displayed: the vane spindle rheometer Brookfield DVIII Ultra and the tilting plane rheometer of the Institute for Hydrological and Geological Protection of the Italian Research Council (CNR IRPI) (D’Agostino and Cesca, 2009-a; D’Agostino et al., 2010). Moreover, a standard and easily repeatable procedure, based on the two-dimensional simplification suggested by Hungr (1995), is proposed to estimate the mean basal shear stress, which develops during the runout phase. Interesting considerations about flow regime and depositional features have been achieved thanks to the velocity recorded in the tilting plane laboratory test. Considering the definition of procedures to calibrate the rheological parameters, two approaches have been proposed. The first is based on the tilting plane rheometer results while the second uses the relation between magnitude and debris-flow mobility (Rickenmann, 1999; Lorente et al., 2003) and a specifically-shaped index. In the last part of the research work, a performance analysis about two monophasic numerical models is presented. The compared models are FLO-2D (O’Brien et al., 1993) and RAMMS (Rapid Mass MovementS, Christen et al. 2010). The models have been tested in the simulation of some debris flows with heterogeneous characteristics: different rheological behavior, magnitude and topographic situation. The efficiency of the laboratory tests in the calibration of the rheological parameters of the model has been also investigated through this performance analysis. The output of the model has been assessed through two indexes: the first analyzes the positive accuracy (Scheidl e Rickenmann, 2010), whereas the second expresses the model efficiency quantifying the excess deposit simulation

Comparison of measurement methods of the front velocity of small-scale debris flows

Debris flow is a gravity-driven process, which is characterized by a travelling dense surge including large boulders, and it is followed by a more fluid tail. These characteristics make difficult the measurement of the mean flow velocity by means of common hydraulic techniques. Different methods can be used at real scale and small-scale to measure the front velocity but a dedicate comparison between available methods is still lacking. This research aims to compare the front velocity measurements in the transport zone of a miniature debris flow using three devices: i) a common digital video camera (29 frames per second); ii) a high speed thermo camera (60 fps); and iii) a laser photoelectric sensors system. The statistical analysis of data has highlighted no significant differences exist between front velocities obtained by means of the video camera and the thermo camera, whereas photocells data statistically differ from those achieved via the other systems. Some lack of data recorded by photocell was documented, while the thermo camera technique did not show significant loss of information being also helpful to detect the kinematic behaviour of single particles. Finally, the tests confirmed the influence of the solid volumetric concentration in the debris-flow mechanics, which promotes, ceteris paribus, the debris-flow slowing down

Analysis of wheelchair sprint biomechanics on two elite athletes on an instrumented drum ergometer

Introduction. Wheelchair athletics requires the maximization of pushing technique throughout the full length of the race, with particular attention to the transition from start to full speed. The use of dynamometric handrims, introduced for complete propulsion analysis has only recently made available with lightweight portable solutions for athletics [1]. Drum ergometers have also showed to be effective for the study several disciplines in the analysis of propulsion techniques [2]. The use of force plates under the wheels only accounts for the first start push; the use of IMU can instead follow the action along the full race in both simulated or track measurements [3]. In the present work, the combination of a validated drum ergometer, IMU sensors and EMG analysis was adopted to study and compare the sprint biomechanics of two elite athletes on a simulated 100m sprint. Methods. A drum ergometer [2] was adapted to host the athletics wheelchairs restrained at the front wheels. Inertial disks were applied to the drums to match the equivalent linear inertia of each subject (Figure 1.a). A set of Inertial sensors was placed on the hands and wheels of the athletes. Eight EMG sensors were placed on trapezius descendens (TD) right, deltoideus anterior (DA) right, latissimus dorsi (LD) right, pectoralis major (PM) right, biceps brachii (BB) left & right and triceps brachii (TB) left & right. IMU and EMG were captured with a MuscleLab system from Ergomotion. Two elite wheelchair athletes of Italian National Team, D.G. (T 53, 77kg, 100m P.B. 15.92s) and G.S. (T54, 56kg, 100m P.B. 14.93s) volunteered for the study and performed 5 repetitions of a simulated 100m sprint. As previous researchers, two events related to hand-to-rim contact were evaluated using hand acceleration profiles: Hand contact (HC) and Hand Release (HR). As a result, the Push Phase (PP), and the Recovery Phase (RP), were calculated, together with the Total Push Angle (TPA). Similarly to other experiences [4], athletes were asked to perform static maximal voluntary pushes against the blocked drum resistance at three hand positions on the rim: HC, HR and an intermediate position. Isometric tangential push forces at the rim were calculated from the peak torque recorded at the drum and normalized to body weight BW as in Figure 1.b. EMG moving 50 ms window RMS signals were normalized to the trial maximum value: a threshold of 20% was chosen to consider the muscle activation pattern in a polar graph as in Figure 1.c. Results. Simulated best sprint time on the drum ergometer resulted 15.25s for D.G. and 14.72s for G.S., very close to their personal best, thus confirming the validity of the equivalent intertial drum ergometer. Highest isometric forces were obtained at the HC position as shown in Figure 1.b. EMG results presented in Figure 1.c showed how the two athletes adopted different pushing techniques at 5th and 25th push. Both athletes shift forward the HC and HR position at higher speed and widen their TPA, but G.S. TPA increase is more evident. Clock polar diagram allow to capture the differences in muscle coordination among athletes and the change of activation from slow to high speed. Discussion. The use of wireless sensors for IMU and EMG analysis allows for the extension of the method to track tests, in combination with the collection of loads from instrumented handrims that are under development

Stereophotogrammetric Analysis of Pushing Kinematics of Wheelchair Rugby Players on an Inertial Ergometer

The aim of the work was the kinematic analysis of pushing technique of four wheelchair rugby players using a stereophotogrammetric motion capture system. The four players presented an increasing level of ability expressed by their wheelchair rugby classification point. An original contribution of the work is the fact that exercises were recorded on an inertial drum ergometer with players using their own game wheelchair. The ergometer inertia was tuned to reproduce the linear inertia of each player: subjects performed sprint tests without additional resistance and Wingate tests. The Initial Contact and Hand Release values at the wheel were recorded for each test in the early stages and at the end. The shoulder flexion/extension angle and the elbow flexion angle were plotted against each other to highlight a tendency to a synchronous joint kinematics with increasing classification points

Functional effects of schizophrenia-linked genetic variants on intrinsic single-neuron excitability: A modeling study

Background: Recent genome-wide association studies (GWAS) have identified a large number of genetic risk factors for schizophrenia (SCZ) featuring ion channels and calcium transporters. For some of these risk factors, independent prior investigations have examined the effects of genetic alterations on the cellular electrical excitability and calcium homeostasis. In the present proof-of-concept study, we harnessed these experimental results for modeling of computational properties on layer V cortical pyramidal cell and identify possible common alterations in behavior across SCZ-related genes. Methods: We applied a biophysically detailed multi-compartmental model to study the excitability of a layer V pyramidal cell. We reviewed the literature on functional genomics for variants of genes associated with SCZ, and used changes in neuron model parameters to represent the effects of these variants. Results: We present and apply a framework for examining the effects of subtle single nucleotide polymorphisms in ion channel and Ca2+ transporter-encoding genes on neuron excitability. Our analysis indicates that most of the considered SCZ- related genetic variants affect the spiking behavior and intracellular calcium dynamics resulting from summation of inputs across the dendritic tree. Conclusions: Our results suggest that alteration in the ability of a single neuron to integrate the inputs and scale its excitability may constitute a fundamental mechanistic contributor to mental disease, alongside with the previously proposed deficits in synaptic communication and network behavior

A new statistical method to assess potential debris flow erosion

Debris-flow erosion patterns were investigated for two adjacent catchments, Molinara and Val del Lago creeks (Eastern Alps, Trento Province, Italy), where two debris flows were triggered by an intense storm in the summer of 2010. Both basins have been inactive over the last two centuries. The debris flows were activated by channel and bank erosion under stable bed conditions before the event. The erosive process was analysed by combining a field campaign (two hundred cross sections were surveyed along the creeks) and pre- and post-event LiDAR surveys. Data were analysed by selecting morphologically-homogenous channel reaches and deriving for each reach: erosion depth, creek width, eroded volume and peak discharge. Investigating the frequency distribution of the erosion depth we found out that it follows an EV1 probability distribution. On this basis, a new approach has been proposed to predict event volumes when the expected maximum potential depth erosion is known. The procedure would be of high interest in predicting debris flow volume in mountain channels characterized by long silent periods

Numerical evaluation of the forest protective role against rockfall after a windthrow: the case study of the Mt. Pore (North-Eastern Italy)

Protection forests effectively preserve people and infrastructures against natural hazards such as rockfall, snow avalanches, landslides, debris flows, soil erosion and floods. Consequently, a reduction of this protective effect due to changes in forest structure can drastically increase the degree of risk related to these phenomena. The Vaia winter storm (29-30 October 2018) affected 41000 ha of forest in North-Eastern Italy, with an amount of windthrow timber volume of 8.6\u2022106 m3, compromising the protective function of a large portion of the forests. The aim of this study is to evaluate changes in the protective effect against rockfall of a forest located on the southern slope of the Mt. Pore after the damages of the Vaia winter storm. Three scenarios have been considered: 1) forest before the windstorm (condition at summer 2018), 2) uncleared windthrow (current status after the windstorm), and 3) cleared windthrow (removal of all fallen dead stems). Rockfall numerical simulations have been pursued considering these three scenarios using the 3D rockfall trajectory model Rockyfor3D. The protective effect of the forest in the three scenarios has been evaluated using the model outputs to calculate quantitative indicators at the distance of the infrastructures at risk. Field surveys and a UAV survey carried out during summer 2018 allowed the collection and the spatialization of the model input parameters, including the forest characteristics before the wind storm. Furthermore, after event on-site investigations allowed the estimation of the windthrow damages and the calibration of the model parameters in the second and third scenarios. Modelling results show that the great amount of dead stems lying on the ground after windthrow (second scenario) can provide protection against rockfall comparable to the living forest (first scenario) in the short period. Effectively, even though the forest and the elements on the ground are not able to stop all the boulders, they can significantly decrease the kinetic energy of the boulders, reducing the speed and rebound height, and decreasing the magnitude of the phenomenon. On the other hand, clearing the windthrow (scenario 3) increase the rockfall risk, especially for the infrastructures at higher distances from the rock cliff. Finally, field surveys supported by remote sensing surveys are revealed essential in order to achieve simulations adherent to reality

GRF ANALYSIS OF TWO ELITE PARALYMPIC SPRINTERS IN STEADY AND RESISTED ACCELERATED TREADMILL RUNNING

Analysis of ground reaction forces (GRFs) allows evaluating performances of paralympic runners with transfemoral amputation. Instrumented treadmills are expensive and low-cost solutions to gather GRFs are worth to be studied. This study aimed to use a commercial treadmill placed on four force platforms to evaluate vertical impulse, braking and propulsive horizontal impulses during steady-speed (SSR) and resisted accelerated (RAR) running. The RAR vertical impulses of the unaffected limb (UL) of the two athletes doubled the values of the affected limb (AL) that has, however, on average 23% larger propulsive action than UL in SSR. The horizontal impulse of AL remains positive in the first 10 steps during RAR, as expected. Agreement between present results and literature confirms that the proposed setup gives sufficient confidence in the evaluation of the sprint technique

Natural Disturbances and Protection Forests: At the Cutting Edge of Remote Sensing Technologies for the Rapid Assessment of Protective Effects against Rockfall

Protection forests can be severely affected by natural disturbances, whose consequences could greatly alter the fundamental ecosystem services they are providing. Assessing and monitoring the status of the protective effects, particularly within disturbed stands, is therefore of vital importance, with timing being a critical issue. Remote sensing technologies (e.g., satellite imagery, LiDAR, UAV) are widely available nowadays and can be effectively applied to quantify and monitor the protective effects of Alpine forests. This is especially important after abrupt changes in forest cover and structure following the occurrence of a disturbance event. In this contribution, we present a brief introduction on remote sensing technologies and their potential contribution to protection forest management, followed by two case studies. In particular, we focus on research areas within protection forests against rockfall affected by windthrow (i.e., the 2018 storm Vaia in the Eastern Italian Alps, where LiDAR and UAV data were used), and forest fires (i.e., the 2017 fall fires in the Western Italian Alps, involving Sentinel-2 image analyses)