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Environmental issues regarding CO2 and recent strategies for alternative fuels through photocatalytic reduction with titania-based materials
No full textCarbon dioxide (CO2) is considered one of the main contributors to the greenhouse effect and is currently a key challenge throughout the world. Therefore, the CO2 complications associated with the environment have in particular been focused on in this review, and various strategies regarding CO2 mitigation, or the utilization of different technologies to produce renewable fuels or useful chemicals to overcome the energy crisis, have been considered together with the recent developments in the photocatalytic reduction of CO2 by means of different titania photocatalysts to produce various energy-bearing products. The problems, progress and future prospects regarding CO2 utilization are presented. This present review indicates that the devolvement of efficient active photocatalysts for this technology is still under way and that better efficiency of the desired products could be accomplished. It is also shown that this technique is still at an embryonic stage, due to a lack of proficiency, and that the yield discrimination is very low. It can therefore be concluded that further research efforts are needed to boost this process towards commercialization in the near future. (C) 2016 Elsevier Ltd. All rights reserved
Assessment and mapping of the shallow geothermal potential in the province of Cuneo (Piedmont, NW Italy)
No full textGround Source Heat Pump (GSHP) is a low carbon heating and cooling technology which can make an important contribution for reaching the ambitious CO2 reduction targets set by the European Union. The economic and technical suitability of this technology strongly depends on the thermal and hydrogeological properties of the ground at the installation site, which need to be assessed in detail. A common indicator adopted to define such suitability is the geothermal potential, i.e. the thermal power that can be exchanged with the ground through a GSHP with a certain setup. In this paper, we present the assessment and mapping of the shallow geothermal potential in the province of Cuneo, a 6900 km2 wide county in NW Italy. Geological, hydrogeological and climatic information are collected and processed to estimate the relevant ground properties. The shallow geothermal potential is then estimated with different methods for closed-loop installations (Borehole Heat Exchangers, BHEs) and open-loop installations (Ground Water Heat Pumps, GWHPs) systems in order to identify the most suitable areas for different technologies. The maps of the geothermal potential are an important planning tool for the installation of GSHPs and for the growth of this renewable energy sourc
On the lack of bound states for certain NLS equations on metric graphs
No full textThe purpose of this paper is to prove some results on the absence of bound states for certain nonlinear Schroedinger equations on noncompact metric graphs with localized nonlinearity. In particular, we show how the topological and metric properties of graphs affect the existence/nonexistence of bound states. This work completes the discussion initiated in \cite{ST,T
Testing general relativity by means of ring lasers
No full textThe paper discusses the optimal conguration of one or more ring lasers to be used for measuring the general relativistic effects of the rotation of the Earth, as manifested on the surface of the planet. The analysis is focused on devices having their normal vector lying in the meridian plane. The crucial role of the evaluation of the angles is evidenced. Special attention is paid to the orientation at the maximum signal, minimizing the sensitivity to the orientation uncertainty. The use of rings at different latitudes is mentioned and the problem of the non-sphericity of the Earth is commented
A study on the role of powertrain system dynamics on vehicle driveability
No full textVehicle driveability describes the complex interactions between the driver and the vehicle, mainly related to longitudinal vibrations. Today, a relevant part of the driveability process optimisation is realised by means of track tests, which require a considerable effort due to the number of parameters (such as stiffness and damping components) affecting this behaviour. The drawback of this approach is that it is carried on at a stage when a design iteration becomes very expensive in terms of time and cost. The objective of this work is to propose a light and accurate tool to represent the relevant quantities involved in the driveability analysis, and to understand which are the main vehicle parameters that influence the torsional vibrations transmitted to the driver. Particular attention is devoted to the role of the tyre, the engine mount, the dual mass flywheel and their possible interactions. The presented nonlinear dynamic model has been validated in time and frequency domain and, through linearisation of its nonlinear components, allows to exploit modal and energy analysis. Objective indexes regarding the driving comfort are additionally considered in order to evaluate possible driveability improvements related to the sensitivity of powertrain parameters
Ground-source pump system for heating and cooling: Review and thermodynamic approach
No full textGround source heat pump (GSHP) is an innovative and perspective technology able to use the ground as a thermal sink or heat source. If combined with system operating at relatively low temperature, it represents a high efficiency solution for the heating of buildings. Complementarily, during cooling operation it has a good advantage with respect to air-cooled systems, because the ground temperature is stably lower than the outdoor air one. Geothermal heat pump systems are able to reduce the environmental impact of buildings for space heating and cooling by using the ground as an energy renewable source. This paper presents a review on the GSHP systems presenting both a summary of different ground-source typologies of heat pumps and a thermodynamic approach for their modeling. The irreversible thermodynamic approach is here summarized and exposed for a complete GSHPs system. This analytical approach is particularly useful for implementing an optimization design tool for GSHP systems. Recently many works have been published about exergy analysis of these systems. Those works suggest that future lines of development may be considered: a) the optimization based on the transient performance of GSHP systems and not on the sole design condition; b) the integration of irreversible thermodynamic optimization approach into the algorithms of control systems. The diffusion of optimized GSHP systems is essential in order to reduce fossil fuel consumption and CO2 emissions, complying with the EU's directive
Customized multi-period stochastic assignment problem for social engagement and opportunistic IoT
No full textAn enormous number of devices are currently available to collect data. One of the main applications of these devices is in the urban environment, where they can collect data useful for improving the operations management and reducing economic, environmental and social costs. This is the main goal of smart cities. To gather these data from devices, companies can build expensive networks able of reaching every part of the city or they can use cheaper alternatives as opportunistic connections, i.e., use the devices of selected people (e.g., mobile users) as mobile hotspots in exchange for a reward. In this paper, we consider this second choice and, in particular, we solve the problem of minimizing the sum of the rewards while providing the connectivity to all sensors. We show that the stochastic approach must be considered since deterministic solutions produce considerable waste. Finally, to reduce the computational time we apply the loss of reduced costs-based variable fixing (LRCVF) heuristic and we compare, by means of computational tests, the performances of the heuristic and a commercial solver. The results prove the effectiveness of the LRCVF heuristic
Alteration of cerebrovascular haemodynamic patterns due to atrial fibrillation: an in silico investigation
No full textThere has recently been growing evidence that atrial fibrillation (AF), the most common cardiac arrhythmia, is independently associated with the risk of dementia. This represents a very recent frontier with high social impact for the number of individuals involved and for the expected increase in AF incidence in the next 40 years. Although a number of potential haemodynamic processes, such as microembolisms, altered cerebral blood flow, hypoperfusion and microbleeds, arise as connecting links between the two pathologies, the causal mechanisms are far from clear. An in silico approach is proposed that combines in sequence two lumped-parameter schemes, for the cardiovascular system and the cerebral circulation. The systemic arterial pressure is obtained from the cardiovascular system and used as the input for the cerebral circulation, with the aim of studying the role of AF on the cerebral haemodynamics with respect to normal sinus rhythm (NSR), over a 5000 beat recording. In particular, the alteration of the haemodynamic (pressure and flowrate) patterns in the microcirculation during AF is analysed by means of different statistical tools, from correlation coefficients to autocorrelation functions, crossing times, extreme values analysis and multivariate linear regression models. A remarkable signal alteration, such as a reduction in signal correlation (NSR, about 3 s; AF, less than 1 s) and increased probability (up to three to four times higher in AF than in NSR) of extreme value events, emerges for the peripheral brain circulation. The described scenario offers a number of plausible cause-effect mechanisms that might explain the occurrence of critical events and the haemodynamic links relating to AF and dementia
Modelling and optimization of machining processes towards economic and environmental sustainability
No full textIn recent years, the increase in energy demand and carbon emission constraints have forced industry sector to improve the process efficiency with respect to environmental sustainability. Therefore, resource saving has become not only an added value, but a real priority for manufacturing in the Industry 4.0 era. Life-Cycle Assessment (LCA) is a common practice for estimating the environmental impact of products during their life-cycle, and can be used more widely and easily if specific models focusing on each life-cycle phase are available. In this thesis, the manufacturing phase of machined products has been modelled by analyzing different process performance metrics. Both the economic efficiency and the environmental sustainability have been accounted for. The Specific Production Time (SPT) is proposed as indicator of the manufacturing productivity; the Specific Production Cost (SPC) is developed in order to quantify the direct and indirect costs related to the manufacturing process; finally, the Specific Energy Requirement (SER) and the Specific Carbon Emission (SCE) indices are proposed in order to assess the environmental sustainability of the manufacturing phase in terms of primary energy demand and carbon footprint, respectively. The models have been developed in order to be valid for conventional machining processes in which cutting tools with defined cutting edge are used. The models are also aimed at the identification of optimum process parameters which allow to minimize each specific goal. In particular, optimum tool life values can be computed as a function of the machine tool, the cutting tool, the metalworking fluid, and the workpiece material. As a consequence, optimum process parameters such as cutting speed can be selected with respect to a specific tool life criterion. The high-efficiency machining range (widely known in literature) has been extended by considering all the four optimal cutting speeds (or tool life values) that minimize each production indicator. Hence, a trade-off criterion is proposed and developed by the introduction of a holistic function which can assign different weights on each optimization target. This advanced optimization method is suggested in order to identify a unique value of cutting speed (or tool life) which can be seen as a compromise among the different criteria of time, cost, and environmental sustainability. Four case studies have been considered in order to apply the proposed models and are focused on the turning of two titanium-based alloys conventionally used for aerospace applications: a Ti-6Al-4V alloy and a Ti-48Al-2Cr-2Nb intermetallic alloy. A Graziano SAG 101 CNC turning lathe was used in the experiments in order to obtain inventory data to test the models. Various set of process parameters such as depth of cut, feed, and cutting speed have been tested in order to identify the coefficients of the Taylor's tool life equation which plays a key role within the proposed models. Three different cutting tools were used. Finally, four lubrication/cooling conditions were adopted such as dry, wet, Minimum Quantity Lubrication (MQL), and Minimum Quantity Cooling (MQC). Overall, the four case studies are presented in order to assess the influence of (1) process parameters, (2) cutting tool geometries, (3) workpiece materials, and (4) lubrication/cooling conditions onto the machining performance measured by the proposed models. The wide applicability of the developed models has been proved by the results related to the analyzed case studies. In particular, the results highlighted that the proposed metrics are suitable for a proper selection of machining conditions that enable at the same time resource savings as well as reduced environmental impacts
Preparation, characterization and environmental/electrochemical energy storage testing of low-cost biochar from natural chitin obtained via pyrolysis at mild conditions
No full textChitin (a biopolymer obtained from shellfish industry) was used as precursor for the production of biochars obtained via pyrolysis treatments performed at mild conditions (in the 290-540 °C range). Biochars were physicochemical characterized in order to evaluate the pyrolysis-induced effects in terms of both functional groups and material structure. Moreover, such carbonaceous materials were tested as adsorbent substrates for the removal of target molecules from aqueous environment as well as in solid-gas experiments, to measure the adsorption capacities and selectivity toward CO2. Lastly, biochars were also investigated as possible cathode materials in sustainable and low-cost electrochemical energy storage devices, such as lithium-sulphur (Li-S) batteries. Interestingly, experimental results evidenced that such chitin-derived biochars obtained via pyrolysis at mild conditions are sustainable, low-cost and easy scalable alternative materials suitable for both environmental and energetic applications