ON-BOARD AND PRE-FLIGHT MECHANICAL MODEL OF YURCHENKO ONE TWIST ON VAULT: IMPLICATIONS FOR PERFORMANCE

The aim of this study was to point out the biomechanical explanation of the judges’ detection of scores relative to the on-board and pre-flight phases of the Yurchenko vault with one twist on (table). In an attempt to identify the weakness of technique and then to diagnose the likely causes of a poor performance, an extensive analysis was undertaken using a deterministic model. The 4 female gymnasts performing YU vault one twist on during the 2006 Italian Championship for Clubs were filmed by three cameras operating at 100Hz. Spearman’s correlation coefficient was used to establish the strength of the relationship between the mechanical variables of the model and the judges` detection of points. Significant correlations indicated that the loss of credit depended mostly on angular variables. Firstly, low angular velocity of the center of mass (CM) at the impact of the board, then the small angular displacement of CM and high shoulder angular velocity produced on board and finally, a smaller hip extension and a larger shoulders extension at the take off from the board. In addition, other vertical variables determined a worst result: the lack of height of the CM at takeoff from the board, the decreased displacement of the CM on the board and the loss of the vertical velocity on the board

Passive solar solutions for buildings: Criteria and guidelines for a synergistic design

Passive solar system design is an essential asset in a zero-energy building perspective to reduce heating, cooling, lighting, and ventilation loads. The integration of passive systems in building leads to a reduction of plant operation with considerable environmental benefits. The design can be related to intrinsic and extrinsic factors that influence the final performance in a synergistic way. The aim of this paper is to provide a comprehensive view of the elements that influence passive solar systems by means of an analysis of the theoretical background and the synergistic design of various solutions available. The paper quantifies the potential impact of influencing factors on the final performance and then investigates a case study of an existing public building, analyzing the effects of the integration of different passive systems through energy simulations. General investigation has highlighted that latitude and orientation impact energy saving on average by 3–13 and 6–11 percentage points, respectively. The case study showed that almost 20% of the building energy demand can be saved by means of passive solar systems. A higher contribution is given by mixing direct and indirect solutions, as half of the heating and around 25% of the cooling energy demand can be cut off

Passive solar systems for buildings: Performance indicators analysis and guidelines for the design

Data from the International Energy Agency confirm that in a zero-energy perspective the integration of solar systems in buildings is essential. The development of passive solar strategies has suffered the lack of standard performance indicators and design guidelines. The aim of this paper is to provide a critical analysis of the main passive solar design strategies based on their classification, performance evaluation and selection methods, with a focus on integrability. Climate and latitude affect the amount of incident solar radiation and the heat losses, while integrability mainly depends on the building structure. For existing buildings, shading and direct systems represent the easiest and most effective passive strategies, while building orientation and shape are limited to new constructions: proper design can reduce building energy demand around 40%. Commercial buildings prefer direct use systems while massive ones with integrated heat storage are more suitable for family houses. A proper selection must consider the energy and economic balance of different building services involved: a multi-objective evaluation method represents the most valid tool to determine the overall performance of passive solar strategies

Anaerobic Digestion of Macrophytes Algae for Eutrophication Mitigation and Biogas Production

Abstract An economy based on biofuels requires production methods which are economically and technically competitive. The production of biogas from biomass by microorganisms is an attractive and ambitious possibility. Marine and lake algae represents a biomass source that could be used for biogas production and their extraction is of benefit for the aquatic environment reducing eutrophication. The goal of the experimental work is to evaluate the algae biomass naturally present in lagoon environment and analyze the biogas resulting from the anaerobic digestion. The Biomethane Potential (BMP) of macrophytes with inoculums from a sewage sludge treatment plant was measured at the University of Perugia. The CH 4 content of biogas was approximately 52%, cumulative CH 4 yield of 217 Nm 3 /t SV was observed after 41 days of digestion

Cerebral hemodynamics on MR perfusion images before and after bypass surgery in patients with giant intracranial aneurysms

Preoperative assessment of the anatomy and dynamics of cerebral circulation for patients with giant intracranial aneurysm can improve both outcome prediction and therapeutic approach. The aim of our study was to use perfusion MR imaging to evaluate cerebral hemodynamics in such patients before and after extraintracranial high-flow bypass surgery. METHODS: Five patients with a giant aneurysm of the intracranial internal carotid artery underwent MR studies before, 1 week after, and 1 month after high-flow bypass surgery. We performed MR and digital subtraction angiography, and conventional and functional MR sequences (diffusion and perfusion). Surgery consisted of middle cerebral artery (MCA)-internal carotid artery bypass with saphenous vein grafts (n = 4) or MCA-external carotid artery bypass (n = 1). RESULTS: In four patients, MR perfusion study showed impaired hemodynamics in the vascular territory supplied by the MCA of the aneurysm side, characterized by significantly reduced mean cerebral blood flow (CBF), whereas mean transit time (MTT) and regional cerebral blood volume (rCBV) were either preserved, reduced, or increased. After surgery, angiography showed good canalization of the bypass graft. MR perfusion data obtained after surgery showed improved cerebral hemodynamics in all cases, with a return of CBF index (CBFi), MTT, and rCBV to nearly normal values. CONCLUSION: Increased MTT with increased or preserved rCBV can be interpreted as a compensatory vasodilatory response to reduced perfusion pressure, presumably from compression and disturbed flow in the giant aneurysmal sac. When maximal vasodilation has occurred, however, the brain can no longer compensate for diminished perfusion by vasodilation, and rCBV and CBFi diminish. Bypass surgery improves hemodynamics, increasing perfusion pressure and, thus, CBFi. Perfusion MR imaging can be used to evaluate cerebral hemodynamics in patients with intracranial giant aneurysm.BACKGROUND AND PURPOSE: Preoperative assessment of the anatomy and dynamics of cerebral circulation for patients with giant intracranial aneurysm can improve both outcome prediction and therapeutic approach. The aim of our study was to use perfusion MR imaging to evaluate cerebral hemodynamics in such patients before and after extraintracranial high-flow bypass surgery. METHODS: Five patients with a giant aneurysm of the intracranial internal carotid artery underwent MR studies before, 1 week after, and 1 month after high-flow bypass surgery. We performed MR and digital subtraction angiography, and conventional and functional MR sequences (diffusion and perfusion). Surgery consisted of middle cerebral artery (MCA)-internal carotid artery bypass with saphenous vein grafts (n = 4) or MCA-external carotid artery bypass (n = 1). RESULTS: In four patients, MR perfusion study showed impaired hemodynamics in the vascular territory supplied by the MCA of the aneurysm side, characterized by significantly reduced mean cerebral blood flow (CBF), whereas mean transit time (MTT) and regional cerebral blood volume (rCBV) were either preserved, reduced, or increased. After surgery, angiography showed good canalization of the bypass graft. MR perfusion data obtained after surgery showed improved cerebral hemodynamics in all cases, with a return of CBF index (CBFi), MTT, and rCBV to nearly normal values. CONCLUSION: Increased MTT with increased or preserved rCBV can be interpreted as a compensatory vasodilatory response to reduced perfusion pressure, presumably from compression and disturbed flow in the giant aneurysmal sac. When maximal vasodilation has occurred, however, the brain can no longer compensate for diminished perfusion by vasodilation, and rCBV and CBFi diminish. Bypass surgery improves hemodynamics, increasing perfusion pressure and, thus, CBFi. Perfusion MR imaging can be used to evaluate cerebral hemodynamics in patients with intracranial giant aneurysm

A Quantitative Methodology to Measure Injector Fouling Through Image Analysis

Abstract The use of vegetables oils in a compression ignited internal combustion engine presents some critical issues as the large amount of carbon deposits on the tip of injectors, which significantly influence emissions and engine performance. A previous draft methodology was developed by the authors, based on images capture and post-processing. The carbon deposit was correlated with the number of pixels in the gray scale, so it was possible to determine a Fouling Index. First results showed interesting perspectives and some limits: the aim of the present work is the optimization of the test bench and methodology. At first an improvement of image acquisition, increasing sampling frequency and image resolution, is performed, replacing the old camera with a digital microscope and improving both injector and microscope positioning. The test bench prototype has been realized with the aid of 3D printing, obtaining fundamental mechanical components. Also an alternative methodology is proposed to evaluate carbon deposits volume through a Volumetric Index. The new methodology validation was done using images sampled with the previous test bench. The performances of the Fouling index and of the new Volumetric Index were compared and fouling was examined in the real case of a diesel engine, fed with diesel and sunflower oil. Results show a greater reliability of the new Volumetric Index

THERMAL SHOCK RESISTANCE OF A SODA LIME GLASS

We studied the thermal shock of a three millimeters thickness soda lime glass using the hot-cold thermal shock technique. The cooling was made by ambient air jet on previously warmed samples. The heat transfer coefficient was about 600 W/°C.m2 (Biot number β = 0.3). The thermal shock duration was fixed at 6 seconds. The hot temperature was taken between 100°C and 550°C while the cold temperature of the air flux was kept constant at 20°C. The acoustic emission technique was used for determining the failure time and the critical temperature difference (ΔTC). By referring to experimental results, thermal shock modelling computations are conducted. Our aim is especially focused on the fracture initiation moments during the cooling process and on the crack initiation sites. The used modeling is based on the local approach of the thermal shock during the experimental data treatment. For each test, the temperature profile and the transient stress state through the samples thickness are determined. By applying the linear superposition property of the stress intensity factors, evolution of the stress intensity factor KI in function of the pre-existing natural flaws in the glass surface is established. The size of the critical flaw is determined by the linear fracture mechanics laws. Computation results confirm the experimental values of the critical difference temperature obtained that is the source of the glass degradation

Anaerobic Digestion of Spoiled Milk in Batch Reactors: Technical and Economic Feasibility☆

Abstract The economic feasibility of the energy conversion through anaerobic digestion of spoiled milk was assessed for the microscale biogas production and heating value was determined experimentally on a pilot plant with a mixture of spoiled milk and an inoculum previously optimized with Anaerobic Biomethanation Potential tests. Results shows that the feasibility of a 100 kWel plant is characterized by a quite short return time of the investment. Considering a discount rate of 5% and a timespan of investment equal to 20 years, payback period is equal to 8-9 years, Net Present Value is equal to 806,903 € and Internal Rate of Return is equal to 16%

Pyrolysis of Olive Stone for Energy Purposes

Abstract Pyrolysis of biomass is a promising technology for the production of distributed and renewable energy on small and micro-scale since it produces a gas with relatively high calorific value, which can be burned in an internal combustion engine or in a microturbine; pyrolysis also generates by products (char and tar) which can be used to provide energy to the process or for cogeneration purposes. This research is aimed at the exploitation of waste from agricultural production processes, in particular olive mill wastes whose management has critical environmental and disposal costs; the yields of pyrogas, tar and char obtained from the pyrolysis of olive stone in a batch reactor was measured. Pyrogas produced is sampled through a line for the sampling of condensable substances in accordance with existing regulations, CEN/TS 15439, and once purified from water vapor and tars is analyzed with micro-GC. The data collected is used to perform mass and energy balances and to determine the content of tars and the Low Heating Value (LHV) of the gas produced

Methodological factors affecting joint moments estimation in clinical gait analysis: A systematic review

Quantitative gait analysis can provide a description of joint kinematics and dynamics, and it is recognized as a clinically useful tool for functional assessment, diagnosis and intervention planning. Clinically interpretable parameters are estimated from quantitative measures (i.e. ground reaction forces, skin marker trajectories, etc.) through biomechanical modelling. In particular, the estimation of joint moments during motion is grounded on several modelling assumptions: (1) body segmental and joint kinematics is derived from the trajectories of markers and by modelling the human body as a kinematic chain; (2) joint resultant (net) loads are, usually, derived from force plate measurements through a model of segmental dynamics. Therefore, both measurement errors and modelling assumptions can affect the results, to an extent that also depends on the characteristics of the motor task analysed (i.e. gait speed). Errors affecting the trajectories of joint centres, the orientation of joint functional axes, the joint angular velocities, the accuracy of inertial parameters and force measurements (concurring to the definition of the dynamic model), can weigh differently in the estimation of clinically interpretable joint moments. Numerous studies addressed all these methodological aspects separately, but a critical analysis of how these aspects may affect the clinical interpretation of joint dynamics is still missing. This article aims at filling this gap through a systematic review of the literature, conducted on Web of Science, Scopus and PubMed. The final objective is hence to provide clear take-home messages to guide laboratories in the estimation of joint moments for the clinical practice