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On the Use of Synthetic Jet Actuators to Induce Jet-Vectoring in Nozzles
No full textThe application of Synthetic Jet (SJ) flow manipulators to the thrust vectoring of supersonic nozzles is investigated numerically. The thrust vectoring is obtained here by SJ induced flow separations, which generate the required asymmetry of the nozzle wall pressure distribution. The computational technique is based on a well-assessed mathematical model of the compressible URANS equations. The domain-decomposition approach is adopted for coupling the flow in the actuators with the nozzle flow. Nozzle performances and thrust vector angles have been computed for a fixed Nozzle Pressure Ratio. Application of SJ to Shock Vector Control and to Dual-Throat Nozzle technologies is investigated. The open-loop response of the nozzles has been computed under different SJ forcing in order to investigate the thrust vectoring effectiveness and controllability
Physical limits to Economic Growth
No full textThe debate on the physical limits and constraints to the economic growth of globalized society is now widespread. This book explores the physical and economic aspects of the conflict between humans, with their thoughtless focus on growth through material production, and environmental constraints. In the context of the looming shortage of material resources and the latest science on climate change, Physical Limits to Economic Growth offers new insights which provide a broad and comprehensive picture of the conflict between humans and environmental constraints. The authors' approach goes beyond the boundaries of specialized disciplines to explore climate change, resource depletion, technical innovation and the interactions between these within the socio-economic-institutional systems we live in. This volume looks at opportunities for rethinking these systems if we moved away from fossil fuel dependence, while considering the status of current mainstream economic thinking around this subject. Physical Limits to Economic Growth provides a genuine interdisciplinary examination of the physical limits to economic growth. It will be of interest to both students and academics in various disciplines in the areas of natural sciences, climate change and economics
Time-dependent spectral analysis of interactions within groups of walking pedestrians and vertical structural motion using wavelets
No full textA multi-scale and multi-object interaction phenomena can arise when a group of walking pedestrians crosses a structure capable of exhibiting dynamic response. This is because each pedestrian is an autonomous dynamic system capable of displaying intricate behaviour affected by social, psychological, biomechanical and environmental factors, including adaptations to the structural motion. Despite a wealth of mathematical models attempting to describe and simulate coupled crowd-structure system, their applicability can generally be considered uncertain. This can be assigned to a number of assumptions made in their development and the scarcity or unavailability of data suitable for their validation, in particular those associated with pedestrian-pedestrian and pedestrian-structure interaction. To alleviate this problem, data on behaviour of individual pedestrians within groups of six walkers with different spatial arrangements are gathered simultaneously with data on dynamic structural response of a footbridge, from a series of measurements utilising wireless motion monitors. Unlike in previous studies on coordination of pedestrian behaviour, the collected data can serve as a proxy for pedestrian vertical force, which is of critical importance from the point of view of structural stability. A bivariate analysis framework is proposed and applied to these data, encompassing wavelet transform, synchronisation measures based on Shannon entropy and circular statistics. A topological pedestrian map is contrived showing the strength and directionality of between-subjects interactions. It is found that the coordination in pedestrians' vertical force depends on the spatial collocation within a group, but it is generally weak. The relationship between the bridge and pedestrian behaviour is also analysed, revealing stronger propensity for pedestrians to coordinate their force with the structural motion rather than with each other
High performing single-ion conducting block copolymer electrolytes based on poly(ethylene oxide) and specifically designed methacrylic sulfonamide
No full textIn the field of polymer electrolytes, new single-ion conductors have attracted increasing interest in recent years, mainly because of their intrinsic safety and peculiar chemical structure that can be tailored as desired to display unique properties, such as tLi+ ≈ 1. Nevertheless, their practical application is still limited by low ionic conductivity (σ, far below 10-5 S cm-1 at 25 °C). Herein, the preparation and characterization of new families of single-ion conducting copolymers based on the specifically designed lithium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethylsulfonyl)imide (LiMTFSI) anionic monomer is described. RAFT polymerization was employed to prepare well-defined anionic di- and tri-block copolymers comprising poly(LiMTFSI) and poly(ethylene oxide) blocks. Block copolymers were semi crystalline with a single Tg. They showed very high σ (≈ 10-4 S cm-1 at 70 °C), impressive t+ ≈ 0.91 and wide 4.5 V electrochemical stability, combined with long lifetime up to 300 cycles and outstanding rate performance in LiFePO4/Li cells at different temperatures
Photocured polymer electrolytes for lithium-based batteries
No full textWe all desire a long-lasting, non-explosive, flexible and small lithium-ion battery (LIB) for our portable electronic devices and (future) electric vehicles. The use of a solid polymer as electrolyte, instead of a flammable solvent, is currently the most promising solution for thinner and safer LIBs. Poly(ethylene oxide)-based polymers (PEO) are widely used, even commercially, thanks to their good ability to transport lithium ions at temperatures over 60 °C. In our Lab, we focus on the structuring of classic −EO− based backbones by photo-polymerization, a fast, cost-effective and solvent-free technique. Solid polymer electrolytes (SPEs) based on different monomers/oligomers are prepared. By incorporating high amounts of plasticizers and lithium salts, outstanding ionic conductivities are obtained (σ > 10-4 S cm-1 at 20 °C) along with wide electrochemical stability window (>5 V vs. Li+/Li) as well as good interfacial stability. Besides, SPEs have remarkable morphological characteristics in terms of homogeneity, flexibility and robustness. All-solid lithium-based polymer cells show very good cycling behavior in terms of rate capability and stability over a wide range of operating temperatures, which confirms the promising prospects of photocured polymer electrolytes for practical application at ambient/sub-ambient temperatures
A new open-source system for strategic freight logistics planning: the SYNCHRO-NET optimization tools
No full textGlobalization and e-commerce facilities have yielded in the recent years an incredibly huge increment of freight movements. Consequently, the underlying supply chains have become more and more complex to manage for the shipping companies, in terms of costs, distances, times, and environmental sustainability. SYNCHRO-NET, a H2020 European research project, aims to de-stress the international supply chains by fostering cost-effective and greener transportation alternatives. Besides other important actions, the SYNCHRO-NET framework provides an optimization and simulation toolset to support decision-making in freight logistics planning at a strategic level. The synchronized use of different transportation modes and the exploitation of smart steaming strategies for ship movements are the two main aspects considered in this innovative optimization system. In this paper, we present the optimization toolset developed, its contribution with respect to the existing platforms, and the experimental set-up implemented to evaluate its performance, usability, and effectiveness. The system is, in fact, currently under evaluation by several world-wide leading companies in freight logistics and transportation. However, the toolset potentialities go beyond the SYNCHRO-NET context, being the system an open-source project that makes use of open data formats and technologies
Reduced order modeling for multistage bladed disks with friction contacts at the flange joint
No full textMost aircraft turbojet engine consist of multiple stages coupled by means of bolted flange joints which potentially represent source of nonlinearities due to friction contacts. The methods aimed at predicting the forced response of a multi-stage bladed disk have to take into account such nonlinear behavior and its effect in damping the blades vibration. In this paper, a novel reduced order modeling method is proposed for studying nonlinear vibration problems of multi-stage bladed disk. The methodology exploits the shape of the single stage normal modes at the inter-stage boundary that are approximated by few spatial Fourier coefficients. Most of the Fourier coefficients refers to the dominant kinematics of the mode shapes of a cyclic symmetric structure (standard harmonics), while the others corresponds to new higher frequency phenomena detectable at the inter-stage boundary (extra harmonics). Under the hypothesis of the Single Harmonic Balance Method the relative displacement field at the inter-stage boundary can be rebuilt and the contact forces calculated by employing the classic Jenkins contact element. The method is here applied to a simple multi-stage bladed disk and its performances are tested using as a enchmark the multi-stagereduced order model obtained by the Craig-Bampton reduction of each single-stages