Under many aspects Italy would be ideal for cycling:the weather is favourable for a good part of the year and many historic centres are characterized by roads which would mainly be suitable for bicycle traffic.The pos...Under many aspects Italy would be ideal for cycling:the weather is favourable for a good part of the year and many historic centres are characterized by roads which would mainly be suitable for bicycle traffic.The positive aspects relating to cycling are well known,but unfortunately,the use of bicycles in Italy is still poor and the main cause of this phenomenon is certainly relating to a general lack of safety in cycling.In the last decade,in Italy the trend of road accidents and victims is generally decreasing,but,at the same time,the number of cyclists involved in road accidents increased by 24,5%,therefore,more attention to cyclists as Vulnerable Road Users is absolutely needed.The causes of this high accident rate is mainly relating to a lack of national legislation or to standards which are old,often overlapped to regional guidelines,uneven,confusing and in some case also contradictory.In terms of cycle network planning,it should be reminded that in Italy there is no regulation that establishes the criteria for a functional classification of bicycle paths.As a consequence,the infrastructure geometry and facilities(bicycle parking,places of refreshments,cycle repair shops,etc.)are not properly put in relation to the role played by the cycle path in the territory.In the course of time,we assisted to the realization of isolated cycle path trunks,generally out of a planning strategy and characterized by their own geometry.Therefore,taking also inspiration by the standards developed in other European Countries,this research tries to provide guidelines for pre-normative functional classification of cycle paths,for their design and planning,in order to obtain safe and homogeneous cycling routes in Italy.It should be noted that the technical solutions,devices and traffic regulations,adopted in other countries,are very effective for a safe cycle mobility,but need to be revised in relation to the existing Italian law.展开更多
The age hardening behavior of gravity cast B356 aluminum alloy was investigated by differential scanning calorimetry(DSC), hardness measurements and tensile tests. Three different artificial aging temperatures were se...The age hardening behavior of gravity cast B356 aluminum alloy was investigated by differential scanning calorimetry(DSC), hardness measurements and tensile tests. Three different artificial aging temperatures were selected, namely 155, 165 and 180 °C, with heat treatment time from 40 min to 32 h. DSC analysis results show that cluster formation begins below room temperature(at around-10 °C). Since cluster formation influences the subsequent precipitation of the main strengthening β'' phase, it can be inferred that a delay between solutionizing and artificial aging has a detrimental effect on the mechanical properties of the alloy. It was also confirmed that the hardness and the tensile properties of the alloy reach the maximum values when β'' phase is completely developed during the artificial aging. This happens after 16 h for samples aged at 155 °C, after 6 h for samples aged at 165 °C and after 4 h for samples aged at 180 °C. A subsequent decrease of the mechanical properties, observed only in the sample aged at the highest temperature, with increasing aging time can be associated with the transformation of the coherent β'' phase into the semi-coherent β' phase. Finally, the activation energy associated with the precipitation of β'' phase was calculated to be 57.2 k J/mol.展开更多
In recent years,certain foundry processes have made it possible to obtain products with very thin parts,below the4mmthreshold of the permanent mold casting technology.The safety margins of these castings have been red...In recent years,certain foundry processes have made it possible to obtain products with very thin parts,below the4mmthreshold of the permanent mold casting technology.The safety margins of these castings have been reduced,so the T6heattreatment conditions adopted for the Al?7Si?Mg alloys need to be investigated to identify the best combination of strength andductility.Furthermore,the cost and the production time associated with T6heat treatment have to be optimized.In the present work,an experimental study was carried out to optimize the solution treatment and artificial aging conditions in gravity cast thin bars ofB356aluminum alloy modified with Sr.Two solution temperatures were selected,530°C and550°C,respectively,with solutiontime ranging from2to8h,followed by water quenching and artificial aging at165°C with aging time from2to32h.The results ofhardness and tensile tests were correlated with differential scanning calorimetry(DSC)analysis.The best combination of mechanicalproperties and heat treatment duration was obtained with2h solutionizing at550°C and8h aging at165°C.DSC analysis showedthat the alloy’s mechanical properties reach the maximum value when theβ''phase is completely developed during the artificialaging.展开更多
Dam-break analysis is of great importance in mountain environment,especially where reservoirs are located upstream of densely populated areas and hydraulic hazard should be assessed for land planning purposes.Accordin...Dam-break analysis is of great importance in mountain environment,especially where reservoirs are located upstream of densely populated areas and hydraulic hazard should be assessed for land planning purposes.Accordingly,there is a need to identify suitable operative tools which may differ from the ones used in flat flood-prone areas.This paper shows the results provided by a 1D and a 2D model based on the Shallow Water Equations(SWE) for dam-break wave propagation in alpine regions.The 1D model takes advantage of a topographic toolkit that includes an algorithm for pre-processing the Digital Elevation Model(DEM) and of a novel criterion for the automatic cross-section space refinement.The 2D model is FLO-2D,a commercial software widely used for flood routing in mountain areas.In order to verify the predictive effectiveness of these numerical models,the test case of the Cancano dam-break has been recovered from the historical study of De Marchi(1945),which provides a unique laboratory data set concerning the consequences of the potential collapse of the former Cancano dam(Northern Italy).The measured discharge hydrograph at the dam also provides the data to test a simplified method recently proposed for the characterization of the hydrograph following a sudden dam-break.展开更多
This paper provides a summary of the objectives and principles which underpin the 2004 edition of the New Zealand earthquake design standard, AS/NZS 1170 Part 5. As with many modern earthquake design standards, the Ne...This paper provides a summary of the objectives and principles which underpin the 2004 edition of the New Zealand earthquake design standard, AS/NZS 1170 Part 5. As with many modern earthquake design standards, the New Zealand earthquake design standard recognizes that earthquake resistant design that only addresses life safety goals without addressing both operational continuity of essential facilities and damage control, falls short of public expectations. Such standards not longer meet societal expectations. The paper outlines how these issues have been addressed within New Zealand, and some of the issues addressed when preparing appendices to the standard to provide guidance for materials standard writers to ensure consistency with the proposed approach. Recognizing the significance of non-structural components and parts of buildings in both damage control and operational continuity has been an important step forward in attaining the performance levels required.展开更多
To quantify water erosion rates and annual soil loss in mountainous areas,two different empirical models were used to estimate the effects of soil erosion in a small mountain basin,the Guerna Creek watershed,located i...To quantify water erosion rates and annual soil loss in mountainous areas,two different empirical models were used to estimate the effects of soil erosion in a small mountain basin,the Guerna Creek watershed,located in the Central Southern Alps(Northern Italy).These two models,Revised Universal Soil Loss Equation(RUSLE) and Erosion Potential Model(EPM),were implemented in a Geographical Information System,accounting for the geographical,geomorphological,and weather-climate parameters,which are fundamental to evaluating the intensity and variability of the erosive processes.Soil characterization was supported by laboratory analysis.The results(computed soil loss of 87 t/ha/year and 11.1 m^(3)/ha/year,using RUSLE equation and EPM method,respectively,and sediment yield of 7.5 m^(3)/ha/year using EPM method) were compared to other studies reported in the literature for different case studies with similar topographic and climatic features,as well as to those provided by the European Soil Data Centre(ESDAC).In both cases,the agreement was satisfactory,showing consistency of the adopted procedures to the parametrization of the physical processes.展开更多
Nonlinear frequency conversion is one of the most fundamental processes in nonlinear optics.It has a wide range of applications in our daily lives,including novel light sources,sensing,and information processing.It is...Nonlinear frequency conversion is one of the most fundamental processes in nonlinear optics.It has a wide range of applications in our daily lives,including novel light sources,sensing,and information processing.It is usually assumed that nonlinear frequency conversion requires large crystals that gradually accumulate a strong effect.However,the large size of nonlinear crystals is not compatible with the miniaturisation of modern photonic and optoelectronic systems.Therefore,shrinking the nonlinear structures down to the nanoscale,while keeping favourable conversion efficiencies,is of great importance for future photonics applications.In the last decade,researchers have studied the strategies for enhancing the nonlinear efficiencies at the nanoscale,e.g.by employing different nonlinear materials,resonant couplings and hybridization techniques.In this paper,we provide a compact review of the nanomaterials-based efforts,ranging from metal to dielectric and semiconductor nanostructures,including their relevant nanofabrication techniques.展开更多
Oxidation of metallic components often results in degradation and structural failure,prevention is therefore an important topic.On the other hand,oxidation process creates new products such as metal oxides,can be used...Oxidation of metallic components often results in degradation and structural failure,prevention is therefore an important topic.On the other hand,oxidation process creates new products such as metal oxides,can be used as a production route.A well-known process in semiconductor industry is that oxidation in dry or wet atmosphere is a popular way for growth of multi-functional SiO_2 films on Si wafers. Recently,oxidation processes under controlled conditions(atmosphere,temperature,and time) are used to prepare various oxides,carbides,or nitrides with micro-/nano-struetures,well-defined composition,dimension, shape and properties.The use of oxidation now includes thin film and nano-/micro-sized devices, and porous oxides for sensing and catalysis purposes.This paper introduces the research activities in the authors' group on applications of oxidation as a tool for synthesis of functional materials.展开更多
Layered van der Waals(vdW)materials have emerged as a promising platform for nanophotonics due to large refractive indexes and giant optical anisotropy.Unlike conventional dielectrics and semiconductors,the absence of...Layered van der Waals(vdW)materials have emerged as a promising platform for nanophotonics due to large refractive indexes and giant optical anisotropy.Unlike conventional dielectrics and semiconductors,the absence of covalent bonds between layers allows for novel degrees of freedom in designing optically resonant nanophotonic structures down to the atomic scale:from the precise stacking of vertical heterostructures to controlling the twist angle between crystallographic axes.Specifically,although monolayers of transition metal dichalcogenides exhibit giant second-order nonlinear responses,their bulk counterparts with 2H stacking possess zero second-order nonlinearity.In this work,we investigate second harmonic generation(SHG)arising from the interface of WS_(2)/MoS_(2)hetero-bilayer thin films with an additional SHG enhancement in nanostructured optical antennas,mediated by both the excitonic resonances and the anapole-driven field enhancement.When both conditions are met,we observe up to 102 SHG signal enhancement,compared to unstructured bilayers,with SHG conversion efficiency reaching≈10^(−7).Our results highlights vdW materials as a platform for designing unique multilayer optical nanostructures and metamaterial,paving the way for advanced applications in nanophotonics and nonlinear optics.展开更多
When decisions are based on empirical observations,a trade-off arises between flexibility of the decision and ability to generalize to new situations.In this paper,we focus on decisions that are obtained by the empiri...When decisions are based on empirical observations,a trade-off arises between flexibility of the decision and ability to generalize to new situations.In this paper,we focus on decisions that are obtained by the empirical minimization of the Conditional Value-at-Risk(CVa R)and argue that in CVa R the trade-off between flexibility and generalization can be understood on the ground of theoretical results under very general assumptions on the system that generates the observations.The results have implications on topics related to order and structure selection in various applications where the CVa R risk-measure is used.A study on a portfolio optimization problem with real data demonstrates our results.展开更多
Two-dimensional transition-metal dichalcogenides(TMDCs)with intrinsically broken crystal inversion symmetry and large secondorder nonlinear responses have shown great promise for future nonlinear light sources.However...Two-dimensional transition-metal dichalcogenides(TMDCs)with intrinsically broken crystal inversion symmetry and large secondorder nonlinear responses have shown great promise for future nonlinear light sources.However,the sub-nanometer monolayer thickness of such materials limits the length of their nonlinear interaction with light.Here,we experimentally demonstrate the enhancement of the second-harmonic generation from monolayer MoSe_(2) by its integration onto a 220-nm-thick silicon waveguide.Such on-chip integration allows for a marked increase in the interaction length between the MoSe_(2) and the waveguide mode,further enabling phase matching of the nonlinear process.The demonstrated TMDC–silicon photonic hybrid integration opens the door to second-order nonlinear effects within the silicon photonic platform,including efficient frequency conversion,parametric amplification and the generation of entangled photon pairs.展开更多
Appropriate solid waste management(SWM)strategies are necessary to avoid severe environmental and sanitary impacts,especially in low-income countries.Such strategies are most likely to succeed whether implementing act...Appropriate solid waste management(SWM)strategies are necessary to avoid severe environmental and sanitary impacts,especially in low-income countries.Such strategies are most likely to succeed whether implementing actors are supported by scientific research.In this paper,the results of a collaboration between local authorities and researchers are presented and discussed that are the assessment of waste generation in the city of Quelimane(Mozambique),integrating existing and field-collected data and the design of a small-scale center for plastic sorting to complement the SWM system of the city.The center is expected to receive about 0.3-0.4 t/day of plastic waste(5%-7%of the overall amount of plastic waste daily produced in Quelimane).As long-term sustainability represents a typical issue,simplicity of operation was a leading principle in the design of the center;moreover,the design included a treatment plant(WWTP)for generated wastewater,whose management is usually neglected in such interventions.Among others,natural wastewater treatment(constructed wetlands)has been chosen for its affordability.Noteworthy,the so-conceived WWTP appears as a novelty in the scientific literature associated with small-scale plastic sorting plants.The system is designed to treat an average flow of 6 m3/day and consisted of a septic tank followed by a subsurface flow constructed wetland.Overall,the COD(chemical oxygen demand)and TSS(total suspended solids)removal higher than 80%and 90%were estimated,respectively.Based on this work,both the center and the WWTP were successfully realized,which are waiting to become operational.In the authors’opinion,the implemented procedure could become a reference for broader investigations and surveys.展开更多
Dielectric nanocavities are emerging as a versatile and powerful tool for the linear and nonlinear manipulation of light at the nanoscale. In this work, we exploit the effective coupling of electric and toroidal modes...Dielectric nanocavities are emerging as a versatile and powerful tool for the linear and nonlinear manipulation of light at the nanoscale. In this work, we exploit the effective coupling of electric and toroidal modes in AIGaAs nanodimers to locally enhance both electric and magnetic fields while minimizing the optical scattering, thereby optimizing their second-harmonic generation efficiency with respect to the case of a single isolated nanodisk. We also demonstrate that proper near-field coupling can provide fitrther degrees of freedom to control the polari- zation state and the radiation diagram of the second-harmonic field.展开更多
At present,there is a shortage of experimental and simulation studies on fire spread in medium-and large-scale compartments while the existing models of the fire spread are limited for typical engineering applications...At present,there is a shortage of experimental and simulation studies on fire spread in medium-and large-scale compartments while the existing models of the fire spread are limited for typical engineering applications.This paper proposes a new model for large-scale fire spread on medium density fibreboard(MDF)panels.Validating the model with single burning item(SBI)experiments,it is found that the numerical simulation closely predicts the experimental heat release rate(HRR)with some error near the peak.The predicted heat flux and distance of lateral flame spread are consistent with the experiments and an existing model.The effects of kinetic properties and heat of combustion are identified through a sensitivity analysis.The decrease of activation energy and increase of pre-exponential factor make the MDF easier to pyrolyze and the increase of heat of combustion enhances the flame temperature and thus provide more heat feedback to the sample surface.The low activation energy(71.9 kJ/mol)and high heat of combustion(46.5 MJ/kg)of the model ensure the occurrence of flame spread.Furthermore,the model was validated using medium-scale compartment fire experiments and the results showed that the model can accurately predict the HRR after flashover(the error is within 7%).While the burner is ignited,the predictions of in-compartment gas temperature and heat flux are more accurate.However,when the burner is extinguished,the modelled in-compartment gas temperature is lower than the experimental values,resulting in a lower heat flux prediction.The model leads to easier flame spread;therefore,the modelled flame spreads faster in the compartment compared to the experiment,and thus the HRR increases more rapidly.展开更多
Multimode optical fibers are attracting a growing interest for their capability to transport high-power laser beams,coupled with novel nonlinear optics-based applications.However,optical fiber breakdown occurs when be...Multimode optical fibers are attracting a growing interest for their capability to transport high-power laser beams,coupled with novel nonlinear optics-based applications.However,optical fiber breakdown occurs when beam intensities exceed a certain critical value.Optical breakdown associated with irreversible modifications of the refractive index,triggered by multiphoton absorption,has been largely exploited for fiber material microstructuration.Here we show that,for light beam intensities slightly below the breakdown threshold,nonlinear absorption strongly affects the dynamics of a propagating beam as well.We experimentally analyze this subthreshold regime and highlight the key role played by spatial self-imaging in graded-index fibers for enhancing nonlinear optical losses.We characterize the nonlinear power transmission properties of multimode fibers for femtosecond pulses propagating in the near-infrared spectral range.We show that an effective N-photon absorption analytical model is able to describe the experimental data well.展开更多
Carbon black (CB) is the most widely used reinforcing filler for rubber. Nowadays there are several concerns regarding this traditional petroleum-based filler: on one side its environmental footprint is enormous and i...Carbon black (CB) is the most widely used reinforcing filler for rubber. Nowadays there are several concerns regarding this traditional petroleum-based filler: on one side its environmental footprint is enormous and its production process is no more sustainable and on the other side its price increases annually. For these reasons, sustainable alternative fillers are being studied. In the present research the main waste of the steel industry, namely the steel slag from electric arc furnace (EAF), is investigated as non-conventional filler for a nitrile butadiene rubber matrix (NBR). The slag has been characterized to ensure its safe reuse as filler according to the heavy metals leaching. The slag filled compounds have been characterized and compared to CB filled compounds, in terms of processability by rheometric parameters, mechanical properties, Payne effect, and physicochemical properties to investigate the filler-matrix interaction. From the obtained results, it was shown that EAF slag-filled NBRs are comparable to CB filled NBRs in terms of crosslink kinetics and, when compared at the same hardness level, are comparable in terms of viscosity, stiffness, and elongation at break, while when compared at the same filler volume fraction are similar in terms of compression set and stress relaxation.展开更多
文摘Under many aspects Italy would be ideal for cycling:the weather is favourable for a good part of the year and many historic centres are characterized by roads which would mainly be suitable for bicycle traffic.The positive aspects relating to cycling are well known,but unfortunately,the use of bicycles in Italy is still poor and the main cause of this phenomenon is certainly relating to a general lack of safety in cycling.In the last decade,in Italy the trend of road accidents and victims is generally decreasing,but,at the same time,the number of cyclists involved in road accidents increased by 24,5%,therefore,more attention to cyclists as Vulnerable Road Users is absolutely needed.The causes of this high accident rate is mainly relating to a lack of national legislation or to standards which are old,often overlapped to regional guidelines,uneven,confusing and in some case also contradictory.In terms of cycle network planning,it should be reminded that in Italy there is no regulation that establishes the criteria for a functional classification of bicycle paths.As a consequence,the infrastructure geometry and facilities(bicycle parking,places of refreshments,cycle repair shops,etc.)are not properly put in relation to the role played by the cycle path in the territory.In the course of time,we assisted to the realization of isolated cycle path trunks,generally out of a planning strategy and characterized by their own geometry.Therefore,taking also inspiration by the standards developed in other European Countries,this research tries to provide guidelines for pre-normative functional classification of cycle paths,for their design and planning,in order to obtain safe and homogeneous cycling routes in Italy.It should be noted that the technical solutions,devices and traffic regulations,adopted in other countries,are very effective for a safe cycle mobility,but need to be revised in relation to the existing Italian law.
基金funded by Regione Lombardia-MIUR (Research Program "2 MILLIMETRI" ID 30152773)
文摘The age hardening behavior of gravity cast B356 aluminum alloy was investigated by differential scanning calorimetry(DSC), hardness measurements and tensile tests. Three different artificial aging temperatures were selected, namely 155, 165 and 180 °C, with heat treatment time from 40 min to 32 h. DSC analysis results show that cluster formation begins below room temperature(at around-10 °C). Since cluster formation influences the subsequent precipitation of the main strengthening β'' phase, it can be inferred that a delay between solutionizing and artificial aging has a detrimental effect on the mechanical properties of the alloy. It was also confirmed that the hardness and the tensile properties of the alloy reach the maximum values when β'' phase is completely developed during the artificial aging. This happens after 16 h for samples aged at 155 °C, after 6 h for samples aged at 165 °C and after 4 h for samples aged at 180 °C. A subsequent decrease of the mechanical properties, observed only in the sample aged at the highest temperature, with increasing aging time can be associated with the transformation of the coherent β'' phase into the semi-coherent β' phase. Finally, the activation energy associated with the precipitation of β'' phase was calculated to be 57.2 k J/mol.
基金partly funded by Regione Lombardia–MIUR(research program “2 MILLIMETRI” ID 30152773)
文摘In recent years,certain foundry processes have made it possible to obtain products with very thin parts,below the4mmthreshold of the permanent mold casting technology.The safety margins of these castings have been reduced,so the T6heattreatment conditions adopted for the Al?7Si?Mg alloys need to be investigated to identify the best combination of strength andductility.Furthermore,the cost and the production time associated with T6heat treatment have to be optimized.In the present work,an experimental study was carried out to optimize the solution treatment and artificial aging conditions in gravity cast thin bars ofB356aluminum alloy modified with Sr.Two solution temperatures were selected,530°C and550°C,respectively,with solutiontime ranging from2to8h,followed by water quenching and artificial aging at165°C with aging time from2to32h.The results ofhardness and tensile tests were correlated with differential scanning calorimetry(DSC)analysis.The best combination of mechanicalproperties and heat treatment duration was obtained with2h solutionizing at550°C and8h aging at165°C.DSC analysis showedthat the alloy’s mechanical properties reach the maximum value when theβ''phase is completely developed during the artificialaging.
基金developed within the European Project Kulturisk (Grant agreement 265280)
文摘Dam-break analysis is of great importance in mountain environment,especially where reservoirs are located upstream of densely populated areas and hydraulic hazard should be assessed for land planning purposes.Accordingly,there is a need to identify suitable operative tools which may differ from the ones used in flat flood-prone areas.This paper shows the results provided by a 1D and a 2D model based on the Shallow Water Equations(SWE) for dam-break wave propagation in alpine regions.The 1D model takes advantage of a topographic toolkit that includes an algorithm for pre-processing the Digital Elevation Model(DEM) and of a novel criterion for the automatic cross-section space refinement.The 2D model is FLO-2D,a commercial software widely used for flood routing in mountain areas.In order to verify the predictive effectiveness of these numerical models,the test case of the Cancano dam-break has been recovered from the historical study of De Marchi(1945),which provides a unique laboratory data set concerning the consequences of the potential collapse of the former Cancano dam(Northern Italy).The measured discharge hydrograph at the dam also provides the data to test a simplified method recently proposed for the characterization of the hydrograph following a sudden dam-break.
文摘This paper provides a summary of the objectives and principles which underpin the 2004 edition of the New Zealand earthquake design standard, AS/NZS 1170 Part 5. As with many modern earthquake design standards, the New Zealand earthquake design standard recognizes that earthquake resistant design that only addresses life safety goals without addressing both operational continuity of essential facilities and damage control, falls short of public expectations. Such standards not longer meet societal expectations. The paper outlines how these issues have been addressed within New Zealand, and some of the issues addressed when preparing appendices to the standard to provide guidance for materials standard writers to ensure consistency with the proposed approach. Recognizing the significance of non-structural components and parts of buildings in both damage control and operational continuity has been an important step forward in attaining the performance levels required.
基金supported by MC s.r.l.,by the university research project (University of Brescia) Health and Wealth 2015“URBAID (Rigenerazione urbana assistita e integrata)”by the call H2020-SwafS-2016-17 Science with and for Society (European project:“SciShops”: Enhancing the Responsible and Sustainable Expansion of the Science Shops Ecosystem in Europe)。
文摘To quantify water erosion rates and annual soil loss in mountainous areas,two different empirical models were used to estimate the effects of soil erosion in a small mountain basin,the Guerna Creek watershed,located in the Central Southern Alps(Northern Italy).These two models,Revised Universal Soil Loss Equation(RUSLE) and Erosion Potential Model(EPM),were implemented in a Geographical Information System,accounting for the geographical,geomorphological,and weather-climate parameters,which are fundamental to evaluating the intensity and variability of the erosive processes.Soil characterization was supported by laboratory analysis.The results(computed soil loss of 87 t/ha/year and 11.1 m^(3)/ha/year,using RUSLE equation and EPM method,respectively,and sediment yield of 7.5 m^(3)/ha/year using EPM method) were compared to other studies reported in the literature for different case studies with similar topographic and climatic features,as well as to those provided by the European Soil Data Centre(ESDAC).In both cases,the agreement was satisfactory,showing consistency of the adopted procedures to the parametrization of the physical processes.
文摘Nonlinear frequency conversion is one of the most fundamental processes in nonlinear optics.It has a wide range of applications in our daily lives,including novel light sources,sensing,and information processing.It is usually assumed that nonlinear frequency conversion requires large crystals that gradually accumulate a strong effect.However,the large size of nonlinear crystals is not compatible with the miniaturisation of modern photonic and optoelectronic systems.Therefore,shrinking the nonlinear structures down to the nanoscale,while keeping favourable conversion efficiencies,is of great importance for future photonics applications.In the last decade,researchers have studied the strategies for enhancing the nonlinear efficiencies at the nanoscale,e.g.by employing different nonlinear materials,resonant couplings and hybridization techniques.In this paper,we provide a compact review of the nanomaterials-based efforts,ranging from metal to dielectric and semiconductor nanostructures,including their relevant nanofabrication techniques.
基金supports from the Royal Society of New Zealand and the Foundation for Research,Science and Technology,New Zealand for some of the research projects reported in this paperand the contributions from the postgraduate studentsin their group,including Sean Li,Ray Chen and Ian Yan.
文摘Oxidation of metallic components often results in degradation and structural failure,prevention is therefore an important topic.On the other hand,oxidation process creates new products such as metal oxides,can be used as a production route.A well-known process in semiconductor industry is that oxidation in dry or wet atmosphere is a popular way for growth of multi-functional SiO_2 films on Si wafers. Recently,oxidation processes under controlled conditions(atmosphere,temperature,and time) are used to prepare various oxides,carbides,or nitrides with micro-/nano-struetures,well-defined composition,dimension, shape and properties.The use of oxidation now includes thin film and nano-/micro-sized devices, and porous oxides for sensing and catalysis purposes.This paper introduces the research activities in the authors' group on applications of oxidation as a tool for synthesis of functional materials.
基金Funded by the European Union(ERC,METANEXT,101078018 and EIC,NEHO,101046329)Views and opinions expressed are however those of the author(s)only and do not necessarily reflect those of the European Union,the European Research Council Executive Agency,or the European Innovation Council and SMEs Executive Agency(EISMEA).Neither the European Union nor the granting authority can be held responsible for them.This work was also funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Germany’s Excellence Strategy(EXC 2089/1-390776260)+7 种基金Sachbeihilfe MA 4699/7-1 and the Emmy Noether program(TI 1063/1)the Bavarian program Solar Energies Go Hybrid(SolTech)and the Center for NanoScience(CeNS)L.S.acknowledges funding support through a Humboldt Research Fellowship from the Alexander von Humboldt FoundationA.To.acknowledges the financial support from the European Union through”FESR o FSE,PON Ricerca e Innovazione 2014-2020-DM 1062/2021”the University of Palermo through”Fondo Finalizzato alla Ricerca di Ateneo 2024(FFR2024)”This work was partially supported by the European Union under the Italian National Recovery and Resilience Plan(NRRP)of Next Generation EU,of partnership on“Telecommunications of the Future”(PE00000001-program“RESTART”)S2 SUPER-Programmable Networks,Cascade project PRISM-CUP:C79J24000190004.C.D.A.and P.F.acknowledge the financial support from the European Union”METAFAST”H2020-FETOPEN-2018-2020 project,grant agreement no.899673from Ministero Italiano dell’Istruzione(MIUR)through the”METEOR”project PRIN-20202020EY2LJT_002.
文摘Layered van der Waals(vdW)materials have emerged as a promising platform for nanophotonics due to large refractive indexes and giant optical anisotropy.Unlike conventional dielectrics and semiconductors,the absence of covalent bonds between layers allows for novel degrees of freedom in designing optically resonant nanophotonic structures down to the atomic scale:from the precise stacking of vertical heterostructures to controlling the twist angle between crystallographic axes.Specifically,although monolayers of transition metal dichalcogenides exhibit giant second-order nonlinear responses,their bulk counterparts with 2H stacking possess zero second-order nonlinearity.In this work,we investigate second harmonic generation(SHG)arising from the interface of WS_(2)/MoS_(2)hetero-bilayer thin films with an additional SHG enhancement in nanostructured optical antennas,mediated by both the excitonic resonances and the anapole-driven field enhancement.When both conditions are met,we observe up to 102 SHG signal enhancement,compared to unstructured bilayers,with SHG conversion efficiency reaching≈10^(−7).Our results highlights vdW materials as a platform for designing unique multilayer optical nanostructures and metamaterial,paving the way for advanced applications in nanophotonics and nonlinear optics.
基金partially Regione Lombardia under Grant MoSoRe E81B19000840007。
文摘When decisions are based on empirical observations,a trade-off arises between flexibility of the decision and ability to generalize to new situations.In this paper,we focus on decisions that are obtained by the empirical minimization of the Conditional Value-at-Risk(CVa R)and argue that in CVa R the trade-off between flexibility and generalization can be understood on the ground of theoretical results under very general assumptions on the system that generates the observations.The results have implications on topics related to order and structure selection in various applications where the CVa R risk-measure is used.A study on a portfolio optimization problem with real data demonstrates our results.
基金support from the China Scholarship Council for PhD scholarship no.201206110047support from the Australian Research Council through Discovery Projects and participation in the Erasmus Mundus NANOPHI project,contract number 20135659/002-001supported by the ACT node of the Australian National Fabrication Facility.
文摘Two-dimensional transition-metal dichalcogenides(TMDCs)with intrinsically broken crystal inversion symmetry and large secondorder nonlinear responses have shown great promise for future nonlinear light sources.However,the sub-nanometer monolayer thickness of such materials limits the length of their nonlinear interaction with light.Here,we experimentally demonstrate the enhancement of the second-harmonic generation from monolayer MoSe_(2) by its integration onto a 220-nm-thick silicon waveguide.Such on-chip integration allows for a marked increase in the interaction length between the MoSe_(2) and the waveguide mode,further enabling phase matching of the nonlinear process.The demonstrated TMDC–silicon photonic hybrid integration opens the door to second-order nonlinear effects within the silicon photonic platform,including efficient frequency conversion,parametric amplification and the generation of entangled photon pairs.
基金This research was developed based on the project(Europe-Aid/150577/DD/ACT/MZ)funded by the European Union and implemented by the Italian Non-Governmental Organization Celim(Centro Laici Italiani per le Missioni)in partnership with local authorities.
文摘Appropriate solid waste management(SWM)strategies are necessary to avoid severe environmental and sanitary impacts,especially in low-income countries.Such strategies are most likely to succeed whether implementing actors are supported by scientific research.In this paper,the results of a collaboration between local authorities and researchers are presented and discussed that are the assessment of waste generation in the city of Quelimane(Mozambique),integrating existing and field-collected data and the design of a small-scale center for plastic sorting to complement the SWM system of the city.The center is expected to receive about 0.3-0.4 t/day of plastic waste(5%-7%of the overall amount of plastic waste daily produced in Quelimane).As long-term sustainability represents a typical issue,simplicity of operation was a leading principle in the design of the center;moreover,the design included a treatment plant(WWTP)for generated wastewater,whose management is usually neglected in such interventions.Among others,natural wastewater treatment(constructed wetlands)has been chosen for its affordability.Noteworthy,the so-conceived WWTP appears as a novelty in the scientific literature associated with small-scale plastic sorting plants.The system is designed to treat an average flow of 6 m3/day and consisted of a septic tank followed by a subsurface flow constructed wetland.Overall,the COD(chemical oxygen demand)and TSS(total suspended solids)removal higher than 80%and 90%were estimated,respectively.Based on this work,both the center and the WWTP were successfully realized,which are waiting to become operational.In the authors’opinion,the implemented procedure could become a reference for broader investigations and surveys.
基金Australian Research Council(ARC)Education,Audiovisual and Culture Executive Agency(EACEA)(5659/002-001)SATT IdF-Innov UniversitéSorbonne(Double Culture-PhD program)
文摘Dielectric nanocavities are emerging as a versatile and powerful tool for the linear and nonlinear manipulation of light at the nanoscale. In this work, we exploit the effective coupling of electric and toroidal modes in AIGaAs nanodimers to locally enhance both electric and magnetic fields while minimizing the optical scattering, thereby optimizing their second-harmonic generation efficiency with respect to the case of a single isolated nanodisk. We also demonstrate that proper near-field coupling can provide fitrther degrees of freedom to control the polari- zation state and the radiation diagram of the second-harmonic field.
基金This work was supported by the National Key Research&Development(R&D)Plan of China under(No.2020YFC 1522800)the National Natural Science Foundation of China(NSFC)(No.51876148)the Science and Technology Project of State Grid Anhui Electric Corporation of China(No.52120518001S).
文摘At present,there is a shortage of experimental and simulation studies on fire spread in medium-and large-scale compartments while the existing models of the fire spread are limited for typical engineering applications.This paper proposes a new model for large-scale fire spread on medium density fibreboard(MDF)panels.Validating the model with single burning item(SBI)experiments,it is found that the numerical simulation closely predicts the experimental heat release rate(HRR)with some error near the peak.The predicted heat flux and distance of lateral flame spread are consistent with the experiments and an existing model.The effects of kinetic properties and heat of combustion are identified through a sensitivity analysis.The decrease of activation energy and increase of pre-exponential factor make the MDF easier to pyrolyze and the increase of heat of combustion enhances the flame temperature and thus provide more heat feedback to the sample surface.The low activation energy(71.9 kJ/mol)and high heat of combustion(46.5 MJ/kg)of the model ensure the occurrence of flame spread.Furthermore,the model was validated using medium-scale compartment fire experiments and the results showed that the model can accurately predict the HRR after flashover(the error is within 7%).While the burner is ignited,the predictions of in-compartment gas temperature and heat flux are more accurate.However,when the burner is extinguished,the modelled in-compartment gas temperature is lower than the experimental values,resulting in a lower heat flux prediction.The model leads to easier flame spread;therefore,the modelled flame spreads faster in the compartment compared to the experiment,and thus the HRR increases more rapidly.
基金Ministero dell’Istruzione,dell’Universitàe della Ricerca(R18SPB8227)European Research Council(740355,874596)+1 种基金Region Nouvelle Aquitaine(F2MH,SIP2)National Research Agency under the Investments for the future program(ANR-10-LABX-0074-01 Sigma-LIM)。
文摘Multimode optical fibers are attracting a growing interest for their capability to transport high-power laser beams,coupled with novel nonlinear optics-based applications.However,optical fiber breakdown occurs when beam intensities exceed a certain critical value.Optical breakdown associated with irreversible modifications of the refractive index,triggered by multiphoton absorption,has been largely exploited for fiber material microstructuration.Here we show that,for light beam intensities slightly below the breakdown threshold,nonlinear absorption strongly affects the dynamics of a propagating beam as well.We experimentally analyze this subthreshold regime and highlight the key role played by spatial self-imaging in graded-index fibers for enhancing nonlinear optical losses.We characterize the nonlinear power transmission properties of multimode fibers for femtosecond pulses propagating in the near-infrared spectral range.We show that an effective N-photon absorption analytical model is able to describe the experimental data well.
文摘Carbon black (CB) is the most widely used reinforcing filler for rubber. Nowadays there are several concerns regarding this traditional petroleum-based filler: on one side its environmental footprint is enormous and its production process is no more sustainable and on the other side its price increases annually. For these reasons, sustainable alternative fillers are being studied. In the present research the main waste of the steel industry, namely the steel slag from electric arc furnace (EAF), is investigated as non-conventional filler for a nitrile butadiene rubber matrix (NBR). The slag has been characterized to ensure its safe reuse as filler according to the heavy metals leaching. The slag filled compounds have been characterized and compared to CB filled compounds, in terms of processability by rheometric parameters, mechanical properties, Payne effect, and physicochemical properties to investigate the filler-matrix interaction. From the obtained results, it was shown that EAF slag-filled NBRs are comparable to CB filled NBRs in terms of crosslink kinetics and, when compared at the same hardness level, are comparable in terms of viscosity, stiffness, and elongation at break, while when compared at the same filler volume fraction are similar in terms of compression set and stress relaxation.
