323 research outputs found
Facile synthesis of Fe3O4 nanorod decorated reduced graphene oxide (RGO) for supercapacitor application
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The development of electrode materials capable of delivering high electrochemical performance is a major challenge. Herein, we demonstrate a facile approach for the synthesis of rod-shaped Fe3O4 nanostructures anchored on the reduced graphene oxide (RGO) surface and its application as an active electrode material for supercapacitors. The RGO-Fe3O4 nanocomposite was prepared by the spontaneous deposition of the rod-like FeOOH nanostructure onto the self-reduced GO surface followed by a thermal annealing process. The physical characterizations demonstrate the decoration of the rod-like Fe3O4 nanostructure over the RGO surface. Morphology analysis demonstrates that Fe3O4 nanorods with an average size of 150 nm are distributed over the RGO surface. The surface area analysis demonstrates that the as-synthesized RGO-Fe3O4 nanorod nanocomposite has 186 m(2) g(-1) specific surface area, which is higher compared to the Fe3O4 nanorods. As an active electrode material, the RGO-Fe3O4 nanocomposite shows excellent electrochemical performance compared to Fe3O4 nanorods. On the RGO-Fe3O4 nanocomposite based electrode a specific capacity of 315 C g(-1) was observed at 5 A g(-1) current density. Additionally, the RGO-Fe3O4 nanocomposite based electrode displayed excellent cycling stability with 95% specific capacity retention after 2000 cycles. The electrochemical results demonstrates that the RGO-Fe3O4 nanocomposite could be a promising material for energy conversion and storage.</p
Classification of -injective proper maps between non-compact surfaces
No full textWe show that almost all -injective proper maps between two non-compact
surfaces, where surfaces are possibly of infinite type, can be properly
homotoped to finite-sheeted covering maps.Comment: 19 Pages, 1 figure. Comments welcome
Strong Topological Rigidity of Non-Compact Orientable Surfaces
No full textWe show that every orientable infinite-type surface is properly rigid as a consequence of a more general result. Namely, we prove that if a homotopy equivalence between any two non-compact orientable surfaces is a proper map, then it is properly homotopic to a homeomorphism, provided surfaces are neither the plane nor the punctured plane. Thus all non-compact orientable surfaces, except the plane and the punctured plane, are topologically rigid in a strong sense.42 pages, 9 figures. v3: incorporates the referee\u27s comments, accepted in the Algebraic & Geometric Topolog
Thermo-luminescence and neutron absorption cross section evaluations of compounds of Lithium based oxide ceramic breeders in Li-Zr-O system
No full textA new aircraft architecture based on the ACHEON Coanda effect nozzle: flight model and energy evaluation
No full textPurpose
Aeronautic transport has an effective necessity of reducing fuel consumption and emissions to deliver efficiency and competitiveness driven by today commercial and legislative requirements. Actual aircraft configurations scenario allows envisaging the signs of a diffused technological maturity and they seem very near their limits. This scenario clearly shows the necessity of radical innovations with particular reference to propulsion systems and to aircraft architecture consequently.
Methods
This paper presents analyses and discusses a promising propulsive architecture based on an innovative nozzle, which allows realizing the selective adhesion of two impinging streams to two facing jets to two facing Coanda surfaces. This propulsion system is known with the acronym ACHEON (Aerial Coanda High Efficiency Orienting Nozzle). This paper investigates how the application of an all-electric ACHEONs propulsion system to a very traditional commuter aircraft can improve its relevant performances. This paper considers the constraints imposed by current state-of-the-art electric motors, drives, storage and conversion systems in terms of both power/energy density and performance and considers two different aircraft configurations: one using battery only and one adopting a more sophisticated hybrid cogeneration. The necessity of producing a very solid analysis has forced to limit the deflection of the jet in a very conservative range (±15°) with respect to the horizontal. This range can be surely produced also by not optimal configurations and allow minimizing the use of DBD. From the study of general flight dynamics equations of the aircraft in two-dimensional form it has been possible to determine with a high level of accuracy the advantages that ACHEON brings in terms of reduced stall speed and of reduced take-off and landing distances. Additionally, it includes an effective energy analysis focusing on the efficiency and environmental advantages of the electric ACHEON based propulsion by assuming the today industrial grade high capacity batteries with a power density of 207 Wh/kg.
Results
It has been clearly demonstrated that a short flight could be possible adopting battery energy storage, and longer duration could be possible by adopting a more sophisticated cogeneration system, which is based on cogeneration from a well-known turboprop, which is mostly used in helicopter propulsion. This electric generation system can be empowered by recovering the heat and using it to increase the temperature of the jet. It is possible to transfer this considerable amount of heat to the jet by convection and direct fluid mixing. In this way, it is possible to increase the energy of the jets of an amount that allows more than recover the pressure losses in the straitening section. In this case, it is then possible to demonstrate an adequate autonomy of flight and operative range of the aircraft. The proposed architecture, which is within the limits of the most conservative results obtained, demonstrates significant additional benefits for aircraft manoeuvrability. In conclusion, this paper has presented the implantation of ACHEON on well-known traditional aircraft, verifying the suitability and effectiveness of the proposed system both in terms of endurance with a cogeneration architecture and in terms of manoeuvrability. It has demonstrated the potential of the system in terms of both takeoff and landing space requirements.
Conclusions
This innovation opens interesting perspectives for the future implementation of this new vector and thrust propulsion system, especially in the area of greening the aeronautic sector. It has also demonstrated that ACHEON has the potential of renovating completely a classic old aircraft configuration such as the one of Cessna 402
Quantum correlations and violation of the Bell inequality induced by an external field in a two-photon radiative cascade
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Integrating multiscale numerical simulations with machine learning to predict the strain sensing efficiency of nano-engineered smart cementitious composites
No full textPrediction of in-situ strain sensing efficiency of self-sensing cementitious composites using machine learning (ML) requires a large, representative, consistent, and accurate dataset. However, such large experimental dataset is not readily available. Moreover, the success of the ML approach depends on its ability to abide by the fundamental laws of physics. To address these challenges this paper synergistically integrates a validated finite element analysis (FEA)-based multiscale simulation framework with ML to predict the strain-sensing ability of self-sensing cementitious composites enabled by incorporating nano-engineered interfaces. The multiscale simulation framework is leveraged to develop a balanced, representative, complete, and consistent dataset containing 3000 combinations of strain-dependent electromechanical responses. This large dataset is used to predict the strain-sensing ability of the nanoengineered cementitious composites using a feed-forward multilayer perceptron-based neural network (NN) approach which shows excellent prediction efficacy. This paper also applies a Shapley Additive Explanations (SHAP) algorithm to interpret the NN predictions in light of the relative importance of different design parameters on the strain-sensing ability of the composite. Overall, the synergistic and comprehensive approach presented here can be used as a starting point toward the development of reliable performance standards to accelerate the acceptance of these self-sensing cementitious composites for large-scale applications
Elucidating the Interfacial Bonding Behavior of Over-Molded Hybrid Fiber Reinforced Polymer Composites: Experiment and Multiscale Numerical Simulation
No full textThis paper implements molecular dynamics (MD) simulation using reactive force field (ReaxFF) to evaluate the
atomistic origin of the interfacial behavior in the overmolded hybrid unidirectional continuous carbon fiber low-melt PAEK (CFR- LMPAEK)-short carbon fiber reinforced PEEK (SFR-PEEK) polymer composites. From the MD simulation, it was observed that the
interfacial properties improve with increasing maximum processing temperature and injection pressure although such an improving trajectory gets saturated beyond specific limits. The interfacial strength and fracture response of the hybrid polymer system at the interface are also evaluated. The mechanical responses obtained from MD simulation are used as adhesive properties in the macroscale finite element analysis (FEA)-based single lap joint (SLJ) model where the interfacial behavior between the adherends (CFR-LMPAEK and SFR-PEEK) is implemented using cohesive zone model (CZM). The simulated FE results show a good correlation with the SLJ experimental data. Thus, by linking the interfacial properties at the molecular scale to the performance of the interfacial bond at the macroscale, the comprehensive approach presented here opens up various efficient avenues toward atomistically engineered performance tuning in hybrid overmolded fiber-reinforced polymer composites to meet desired large-scale performance needs
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