Forested areas are extremely vulnerable to disasters leading to environmental destruction.Forest Fire is one among them which requires immediate attention.There are lot of works done by authors where Wireless Sensors ...Forested areas are extremely vulnerable to disasters leading to environmental destruction.Forest Fire is one among them which requires immediate attention.There are lot of works done by authors where Wireless Sensors and IoT have been used for forest fire monitoring.So,towards monitoring the forest fire and managing the energy efficiently in IoT,Energy Efficient Routing Protocol for Low power lossy networks(E-RPL)was developed.There were challenges about the scalability of the network resulting in a large end-to-end delay and less packet delivery which led to the development of Aggregator-based Energy Efficient RPL with Data Compression(CAAERPL).Though CAA-ERPL proved effective in terms of reduced packet delivery,less energy consumption,and increased packet delivery ratio for varying number of nodes,there is still challenge in the selection of aggregator which is based purely on probability percentage of nodes.There has been research work where fuzzy logic been employed for Mobile Ad-hoc Routing,RPL routing and cluster head selection in Wireless Sensor.There has been no work where fuzzy logic is employed for aggregator selection in Energy Efficient RPL.So accordingly,we here have proposed Fuzzy Based Aggregator selection in Energy-efficient RPL for region thereby forming DODAG for communicating to Fog/Edge.We here have developed fuzzy inference rules for selecting the aggregator based on strength which takes residual power,Node degree,and Expected Transmission Count(ETX)as input metrics.The Fuzzy Aggregator Energy Efficient RPL(FA-ERPL)based on fuzzy inference rules were analysed against E-RPL in terms of scalability(First and Half Node die),Energy Consumption,and aggregator node energy deviation.From the analysis,it was found that FA-ERPL performed better than E-RPL.These were simulated using MATLAB and results.展开更多
The combination of a 4-node quadrilateral mixed interpolation of tensorial components element(MITC4)and the cell-based smoothed finite element method(CSFEM)was formulated and implemented in this work for the analysis ...The combination of a 4-node quadrilateral mixed interpolation of tensorial components element(MITC4)and the cell-based smoothed finite element method(CSFEM)was formulated and implemented in this work for the analysis of free vibration and unidirectional buckling of shell structures.This formulation was applied to numerous numerical examples of non-woven fabrics.As CSFEM schemes do not require coordinate transformation,spurious modes and numerical instabilities are prevented using bilinear quadrilateral element subdivided into two,three and four smoothing cells.An improvement of the original CSFEM formulation was made regarding the calculation of outward unit normal vectors,which allowed to remove the integral operator in the strain smoothing operation.This procedure conducted both to the simplification of the developed formulation and the reduction of computational cost.A wide range of values for the thickness-to-length ratio and edge boundary conditions were analysed.The developed numerical model proved to overcome the shear locking phenomenon with success,revealing both reduced implementation effort and computational cost in comparison to the conventional FEM approach.The cell-based strain smoothing technique used in this work yields accurate results and generally attains higher convergence rate in energy at low computational cost.展开更多
.It is experimentally verified that nonreciprocal photonic systems with continuous translation symmetry may have an ill-defined topology.The topological classification of such systems is only feasible when the materia....It is experimentally verified that nonreciprocal photonic systems with continuous translation symmetry may have an ill-defined topology.The topological classification of such systems is only feasible when the material response is regularized with a spatial-frequency cutoff.We experimentally demonstrate that adjoining a small air layer to the relevant material interface may effectively imitate an idealized spatial cutoff that suppresses the nonreciprocal response for short wavelengths and regularizes the topology.Furthermore,it is experimentally verified that nonreciprocal systems with an ill-defined topology may be used to abruptly halt the energy flow in a unidirectional waveguide due to the violation of the bulk-edge correspondence.In particular,we report the formation of an energy sink that absorbs the incoming electromagnetic waves with a large field enhancement at the singularity.展开更多
The general use of smartphones assigns additional relevance to QR codes as a privileged tool to the Internet of Things(IoT).Crucial for QR codes is the evolution to IoT-connected smart tags with enhanced storage capac...The general use of smartphones assigns additional relevance to QR codes as a privileged tool to the Internet of Things(IoT).Crucial for QR codes is the evolution to IoT-connected smart tags with enhanced storage capacity and secure accesses.Using the concept of super-modules(s-modules)built from adjacent spatial multiplexed modules with regular geometrical shapes,assisted by colour multiplexing,we modelled and design a single QR code with,at least,the triple storage capacity of an analogous size black/white QR code,acting as a smart-tag ensuring restrict access and trackability.The s-modules are printed using luminescent low-cost and eco-friendly inks based on organic-inorganic hybrids modified by lanthanides with multiplexed colour emission in the orthogonal RGB space.The access to the restrict information is attained only under UV irradiation and encrypted for secure transmission.The concept of active QR codes for smart trackability and IoT was materialised through the development of a free friendly-user mobile app.展开更多
Large-area polycrystalline diamond(PCD)coatings are important for fields such as thermal management,optical windows,tribological moving mechanical assemblies,harsh chemical environments,biological sensors,etc.Microwav...Large-area polycrystalline diamond(PCD)coatings are important for fields such as thermal management,optical windows,tribological moving mechanical assemblies,harsh chemical environments,biological sensors,etc.Microwave plasma chemical vapor deposition(MPCVD)is a standard technique to grow high-quality PCD films over large area due to the absence of contact between the reactive species and the filament or the chamber wall.However,the existence of temperature gradients during growth may compromise the desired uniformity of the final diamond coatings.In the present work,a thick PCD coating was deposited on a 100-mm silicon substrate inside a 915-MHz reactor;the temperature gradient resulted in a non-uniform diamond coating.An attempt was made to relate the local temperature variation during deposition and the different properties of the final coating.It was found that there was large instability inside the system,in terms of substrate temperature(as high asΔT=212℃),that resulted in a large dispersion of the diamond coating’s final properties:residual stress(-15.8 GPa to+6.2 GPa),surface morphology(octahedral pyramids with(111)planes to cubo-octahedrals with(100)flat top surfaces),thickness(190μm to 245μm),columnar growth of diamond(with appearance of variety of nanostructures),nucleation side hardness(17 GPa to 48 GPa),quality(Raman peak FWHM varying from 5.1 cm^(-1) to 12.4 cm^(-1) with occasional splitting).This random variation in properties over large-area PCD coating may hamper reproducible diamond growth for any meaningful technological application.展开更多
We perform a comprehensive analysis of uniform-velocity bilayer spacetime crystals,combining concepts of conventional photonic crystals and special relativity.Given that a spacetime crystal consists of a sequence of s...We perform a comprehensive analysis of uniform-velocity bilayer spacetime crystals,combining concepts of conventional photonic crystals and special relativity.Given that a spacetime crystal consists of a sequence of spacetime discontinuities,we do this by solving the following sequence of problems:(1)the spacetime interface,(2)the double spacetime interface,or spacetime slab,(3)the unbounded crystal,and(4)the truncated crystal.For these problems,we present the following results:(1)an extension of the Stokes principle to spacetime interfaces,(2)an interference-based analysis of the interference phenomenology,(3)a quick linear approximation of the dispersion diagrams,a description of simultaneous wavenumber and frequency bandgaps,and(4)the explanation of the effects of different types of spacetime crystal truncations and the corresponding scattering coefficients.This work may constitute the foundation for a virtually unlimited number of novel canonical spacetime media and metamaterial problems.展开更多
Time-varying media have recently emerged as a new paradigm for wave manipulation,due to the synergy between the discovery of highly nonlinear materials,such as epsilon-near-zero materials,and the quest for wave applic...Time-varying media have recently emerged as a new paradigm for wave manipulation,due to the synergy between the discovery of highly nonlinear materials,such as epsilon-near-zero materials,and the quest for wave applications,such as magnet-free nonreciprocity,multimode light shaping,and ultrafast switching.In this review,we provide a comprehensive discussion of the recent progress achieved with photonic metamaterials whose properties stem from their modulation in time.We review the basic concepts underpinning temporal switching and its relation with spatial scattering and deploy the resulting insight to review photonic time-crystals and their emergent research avenues,such as topological and non-Hermitian physics.We then extend our discussion to account for spatiotemporal modulation and its applications to nonreciprocity,synthetic motion,giant anisotropy,amplification,and many other effects.Finally,we conclude with a review of the most attractive experimental avenues recently demonstrated and provide a few perspectives on emerging trends for future implementations of time-modulation in photonics.展开更多
基金This work is partially funded by FCT/MCTES through national funds and,when applicable,co-funded EU funds under the Project UIDB/50008/2020Ministry of Science and Higher Education of the Russian Federation,Grant 08-08by the Brazilian National Council for Scientific and Technological Development-CNPq,via Grant No.313036/2020-9.
文摘Forested areas are extremely vulnerable to disasters leading to environmental destruction.Forest Fire is one among them which requires immediate attention.There are lot of works done by authors where Wireless Sensors and IoT have been used for forest fire monitoring.So,towards monitoring the forest fire and managing the energy efficiently in IoT,Energy Efficient Routing Protocol for Low power lossy networks(E-RPL)was developed.There were challenges about the scalability of the network resulting in a large end-to-end delay and less packet delivery which led to the development of Aggregator-based Energy Efficient RPL with Data Compression(CAAERPL).Though CAA-ERPL proved effective in terms of reduced packet delivery,less energy consumption,and increased packet delivery ratio for varying number of nodes,there is still challenge in the selection of aggregator which is based purely on probability percentage of nodes.There has been research work where fuzzy logic been employed for Mobile Ad-hoc Routing,RPL routing and cluster head selection in Wireless Sensor.There has been no work where fuzzy logic is employed for aggregator selection in Energy Efficient RPL.So accordingly,we here have proposed Fuzzy Based Aggregator selection in Energy-efficient RPL for region thereby forming DODAG for communicating to Fog/Edge.We here have developed fuzzy inference rules for selecting the aggregator based on strength which takes residual power,Node degree,and Expected Transmission Count(ETX)as input metrics.The Fuzzy Aggregator Energy Efficient RPL(FA-ERPL)based on fuzzy inference rules were analysed against E-RPL in terms of scalability(First and Half Node die),Energy Consumption,and aggregator node energy deviation.From the analysis,it was found that FA-ERPL performed better than E-RPL.These were simulated using MATLAB and results.
基金supported by the Portuguese Foundation for Science and Technology(FCT)through project UID/CTM/00264/2019 of 2C2T—Centro de Ciência e Tecnologia Têxtil,hold by National Founds of FCT/MCTES,and project UID/EEA/04436/2013,COMPETE 2020 with the code POCI-01-0145-FEDER-006941.
文摘The combination of a 4-node quadrilateral mixed interpolation of tensorial components element(MITC4)and the cell-based smoothed finite element method(CSFEM)was formulated and implemented in this work for the analysis of free vibration and unidirectional buckling of shell structures.This formulation was applied to numerous numerical examples of non-woven fabrics.As CSFEM schemes do not require coordinate transformation,spurious modes and numerical instabilities are prevented using bilinear quadrilateral element subdivided into two,three and four smoothing cells.An improvement of the original CSFEM formulation was made regarding the calculation of outward unit normal vectors,which allowed to remove the integral operator in the strain smoothing operation.This procedure conducted both to the simplification of the developed formulation and the reduction of computational cost.A wide range of values for the thickness-to-length ratio and edge boundary conditions were analysed.The developed numerical model proved to overcome the shear locking phenomenon with success,revealing both reduced implementation effort and computational cost in comparison to the conventional FEM approach.The cell-based strain smoothing technique used in this work yields accurate results and generally attains higher convergence rate in energy at low computational cost.
基金the Institution of Engineering and Technology(IET)under the A F Harvey Research Prize 2018the Simons Foundation,by Fundação para Ciência e a Tecnologia under Project PTDC/EEITEL/4543/2014+5 种基金by Instituto de Telecomunicações under Project No.UID/EEA/50008/2020D.E.Fernandes acknowledges the support by FCT,POCH,and the cofinancing of Fundo Social Europeu under the fellowship SFRH/BPD/116525/2016R.A.M.Pereira acknowledges FCT for the Ph.D.grant SFRH/BD/145024/2019T.A.Morgado acknowledges FCT for research financial support with reference CEECIND/04530/2017the CEEC Individual 2017 and IT-Coimbra for the contract as an assistant researcher with reference CT/No.004/2019-F00069S.Lannebère acknowledges FCT and IT-Coimbra for the research financial support with reference DL 57/2016/CP1353/CT000.
文摘.It is experimentally verified that nonreciprocal photonic systems with continuous translation symmetry may have an ill-defined topology.The topological classification of such systems is only feasible when the material response is regularized with a spatial-frequency cutoff.We experimentally demonstrate that adjoining a small air layer to the relevant material interface may effectively imitate an idealized spatial cutoff that suppresses the nonreciprocal response for short wavelengths and regularizes the topology.Furthermore,it is experimentally verified that nonreciprocal systems with an ill-defined topology may be used to abruptly halt the energy flow in a unidirectional waveguide due to the violation of the bulk-edge correspondence.In particular,we report the formation of an energy sink that absorbs the incoming electromagnetic waves with a large field enhancement at the singularity.
基金This work was developed within the scope of the project CICECO-Aveiro Institute of Materials(UIDB/50011/2020&UIDP/50011/2020)Instituto de Telecomunicações(FCT Ref.UIDB/50008/2020-UIDP/50008/2020)WinLEDs(POCI-01-0145-FEDER-030351)and Graphsense(POCI-01-0145-FEDER-032072)financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership through European Regional Development Fund(ERDF)in the frame of Operational Competitiveness and Internationalization Programme(POCI).SFHC thanks Solar-Flex,CENTRO-01-0145-FEDER-030186.A.M.Botas and M.Ferro from the University of Aveiro are acknowledged for help in the hyperspectral and scanning electronic microscopies,respectively。
文摘The general use of smartphones assigns additional relevance to QR codes as a privileged tool to the Internet of Things(IoT).Crucial for QR codes is the evolution to IoT-connected smart tags with enhanced storage capacity and secure accesses.Using the concept of super-modules(s-modules)built from adjacent spatial multiplexed modules with regular geometrical shapes,assisted by colour multiplexing,we modelled and design a single QR code with,at least,the triple storage capacity of an analogous size black/white QR code,acting as a smart-tag ensuring restrict access and trackability.The s-modules are printed using luminescent low-cost and eco-friendly inks based on organic-inorganic hybrids modified by lanthanides with multiplexed colour emission in the orthogonal RGB space.The access to the restrict information is attained only under UV irradiation and encrypted for secure transmission.The concept of active QR codes for smart trackability and IoT was materialised through the development of a free friendly-user mobile app.
文摘Large-area polycrystalline diamond(PCD)coatings are important for fields such as thermal management,optical windows,tribological moving mechanical assemblies,harsh chemical environments,biological sensors,etc.Microwave plasma chemical vapor deposition(MPCVD)is a standard technique to grow high-quality PCD films over large area due to the absence of contact between the reactive species and the filament or the chamber wall.However,the existence of temperature gradients during growth may compromise the desired uniformity of the final diamond coatings.In the present work,a thick PCD coating was deposited on a 100-mm silicon substrate inside a 915-MHz reactor;the temperature gradient resulted in a non-uniform diamond coating.An attempt was made to relate the local temperature variation during deposition and the different properties of the final coating.It was found that there was large instability inside the system,in terms of substrate temperature(as high asΔT=212℃),that resulted in a large dispersion of the diamond coating’s final properties:residual stress(-15.8 GPa to+6.2 GPa),surface morphology(octahedral pyramids with(111)planes to cubo-octahedrals with(100)flat top surfaces),thickness(190μm to 245μm),columnar growth of diamond(with appearance of variety of nanostructures),nucleation side hardness(17 GPa to 48 GPa),quality(Raman peak FWHM varying from 5.1 cm^(-1) to 12.4 cm^(-1) with occasional splitting).This random variation in properties over large-area PCD coating may hamper reproducible diamond growth for any meaningful technological application.
文摘We perform a comprehensive analysis of uniform-velocity bilayer spacetime crystals,combining concepts of conventional photonic crystals and special relativity.Given that a spacetime crystal consists of a sequence of spacetime discontinuities,we do this by solving the following sequence of problems:(1)the spacetime interface,(2)the double spacetime interface,or spacetime slab,(3)the unbounded crystal,and(4)the truncated crystal.For these problems,we present the following results:(1)an extension of the Stokes principle to spacetime interfaces,(2)an interference-based analysis of the interference phenomenology,(3)a quick linear approximation of the dispersion diagrams,a description of simultaneous wavenumber and frequency bandgaps,and(4)the explanation of the effects of different types of spacetime crystal truncations and the corresponding scattering coefficients.This work may constitute the foundation for a virtually unlimited number of novel canonical spacetime media and metamaterial problems.
基金funding from the Engineering and Physical Sciences Research Council via an EPSRC Doctoral Prize Fellowship (Grant No. EP/T51780X/1)a Junior Fellowship of the Simons Society of Fellows (855344,EG)+5 种基金funding from Fundação para a Ciência e a Tecnologia and Instituto de Telecomunicações under project UIDB/50008/2020funded by the CEEC Individual program from Fundação para a Ciência e a Tecnologia with reference CEECIND/02947/2020funding from the Engineering and Physical Sciences Research Council (EP/V048880)funding from the Gordon and Betty More Foundationfunding from the Department of Defense, the Simons Foundationthe Air Force Office of Scientific Research MURI program
文摘Time-varying media have recently emerged as a new paradigm for wave manipulation,due to the synergy between the discovery of highly nonlinear materials,such as epsilon-near-zero materials,and the quest for wave applications,such as magnet-free nonreciprocity,multimode light shaping,and ultrafast switching.In this review,we provide a comprehensive discussion of the recent progress achieved with photonic metamaterials whose properties stem from their modulation in time.We review the basic concepts underpinning temporal switching and its relation with spatial scattering and deploy the resulting insight to review photonic time-crystals and their emergent research avenues,such as topological and non-Hermitian physics.We then extend our discussion to account for spatiotemporal modulation and its applications to nonreciprocity,synthetic motion,giant anisotropy,amplification,and many other effects.Finally,we conclude with a review of the most attractive experimental avenues recently demonstrated and provide a few perspectives on emerging trends for future implementations of time-modulation in photonics.