27 research outputs found
An alternating direction implicit spectral method for solving two dimensional multi-term time fractional mixed diffusion and diffusion-wave equations
In this paper, we consider the initial boundary value problem of the two
dimensional multi-term time fractional mixed diffusion and diffusion-wave
equations. An alternating direction implicit (ADI) spectral method is developed
based on Legendre spectral approximation in space and finite difference
discretization in time. Numerical stability and convergence of the schemes are
proved, the optimal error is , where are the
polynomial degree, time step size and the regularity of the exact solution,
respectively. We also consider the non-smooth solution case by adding some
correction terms. Numerical experiments are presented to confirm our
theoretical analysis. These techniques can be used to model diffusion and
transport of viscoelastic non-Newtonian fluids
Observatory of Strategic Developments Impacting Urban Logistics (2017 version)
Urban freight living labs need to operate in full recognition of the challenges that will shape the mobility of goods in urban areas in the future. These challenges are several: macroeconomic, micro-economic, demographic, technological, societal, and legal. To help CITYLAB cities implement their urban freight initiatives, a better understanding of These challenges is necessary. This is what this Observatory of strategic developments impacting urban logistics intends to do, by providing data and analysis on some of the most important, or less well known, trends that will shape the urban mobility of goods in the future.
This second version (2017) of the Observatory provides data and analyses on 1) Logistics
Sprawl; 2) E-commerce; and 3) Service trips. Our findings about the main impacts of these three trends for cities involved in urban freight living labs are the following:
- The number of logistics facilities (in their diversity: warehouses, fulfilment centres, distribution centres, cross-dock terminals) is increasing in cities, especially cities of some logistics importance as large consumer markets and/or logistics hubs processing the flow of goods generated by the global economy. These facilities are generally located in suburban areas, but a new niche market of urban warehouses
is emerging.
- Both e-commerce and logistics sprawl generate a rise in freight vehicles in urban areas, dominated by small vehicles, while medium to large lorries are relatively less important. These vehicles performing delivery operations are visible in neighbourhoods and at times of day when they were not identified before: residential neighbourhoods, residential building blocks, side streets, in the early evening and on week-ends. Emerging new types of vehicles (clean delivery vehicles, two and three wheelers) are now visible in urban centres.
- Innovations in the urban supply chains include diverse forms of pick-up points and click-and-collect solutions, while the recent but extremely rapid rise in Technologies and algorithms supporting instant deliveries (on-demand deliveries within less than
two hours) brings with it a flourish of new companies connecting customers, suppliers and independent couriers, often using bicycles.
- The overall impact of these new trends on energy and carbon emission related to urban freight is difficult to assess. Urban freight in general, for the Paris region, brings the following environmental impact: the share of traffic-related CO2, NOx and PM10 due to urban freight is 2.5 times larger than the share of vans and trucks in the regional traffic. The contribution of urban freight to air pollution is larger in the city of Paris. Social costs of air pollution caused by road traffic in general amount to 0.9% of the regional GDP in 2012. Some of the new trends bring more CO2 emissions, such as the relocation of logistics facilities far away in the suburbs, as deconsolidated shipments are delivered to urban consumers and businesses in smaller and more numerous vans. Some trends bring less CO2 emissions, with a rise in cleaner vehicles and innovative solutions such as drop-off/pickup points or bikesupported instant deliveries. Substitution patterns between personal mobility and professional freight mobility can be a good, or a bad, thing for CO2 emissions, depending on the initial circumstances and the way personal shopping was done before online orders.
- What is certain is that these changes bring diversity in the urban traffic flow.
Instant couriers are using all sorts of transport modes, including foot, bicycles, electrically assisted cargocycles, motorbikes, and various types of vans and lorries.
This can negatively impact traffic management, road safety and conflicts in road uses, congestion, air pollution. Also, the trends we have looked at bring new types of urban jobs, with many unresolved legal issues and poor working conditions in many instances. New types of logistics buildings bring architectural diversity and innovation in cities, but also complaints about noise, aesthetics, as well as congestion and pollution at entrance and exit points.
- These environmental and social impacts have been so far poorly documented and researched. Consumers are the main drivers of the changes we have observed, but they are also the residents or visitors of urban areas, and for that they carry an important share of the burdens, as well as the benefits, of the new landscape of urban logistics.
- Service trips are trips in commercial traffic induced by service oriented activities.
According to the German study KiD 2010 service traffic accounts for 11.8% of traffic
in terms of trips and for 19.9% in terms of kilometres travelled. There are differences in terms of vehicle types and economic sectors but few variations in Terms of spatial types.
- An observatory on service traffic must take into account light duty vehicles and passenger cars in general. Establishment based analysis as well as vehicle based
analysis can give detailed insight in traffic generation and traffic behaviour in Service traffic
The evolution of French innovation policies for SMEs : the case of Anvar
La France, comme dâautres pays, cherche Ă valoriser son excellence scientifique et Ă augmenter la compĂ©titivitĂ© de ses petites et moyennes entreprises (PME) pour tirer plein profit de lâinnovation et soutenir la croissance Ă©conomique et lâemploi. Il nây a pas, ni en France ni ailleurs, une politique spĂ©cifique de soutien Ă lâinnovation dans les PME mais des politiques scientifiques et de la recherche industrielle, en particulier en faveur des petites entreprises, et des politiques dâinnovation, dans lesquelles peuvent ĂȘtre identifiĂ©es des mesures spĂ©cifiques visant Ă promouvoir le dĂ©veloppement technologique et lâinnovation dans les PME. Cette Ă©tude sâintĂ©resse Ă la façon dont en France, Ă travers les diffĂ©rentes Ă©poques, ces politiques publiques sont dĂ©finies et organisĂ©es et sâinterroge sur lâefficacitĂ© et lâimpact des interventions publiques dans le dĂ©veloppement de capacitĂ© dâinnovation des PME françaises. Elle se dĂ©roule en trois parties, en respectant une chronologie historique correspondant aux grandes Ă©tapes de lâĂ©volution des politiques depuis les annĂ©es 1960-1970 jusquâĂ prĂ©sent. Ces trois parties analytiques sont enrichies par lâanalyse du cas de lâAgence nationale de valorisation de la recherche (Anvar). A la fin de ce travail, nous suggĂ©rons que la France entre dans une phase critique oĂč des rĂ©formes structurelles doivent ĂȘtre menĂ©es pour assurer le dĂ©veloppement de la compĂ©titivitĂ© des PME et de lâinnovation.France, like other countries, seeks to promote its scientific excellence and to increase the competitiveness of its small and medium enterprises (SMEs) by taking full advantage of innovation to sustain economic growth and employment. In France as in other countries, there is no specific policy to support innovation in SMEs but both science and industrial research policies, especially for small businesses, and innovation policies, in which can be identified specific measures to promote technological development and innovation in SMEs. This study focuses on "how", in France, such public policies are defined and organized through different periods and it questions the effectiveness and impact of public interventions aimed at developing French SMEsâ innovation capacity. The study is divided in three parts, following a historical chronology corresponding to major stages of political evolution from the years 1960-1970 till now. These three analytical parts are enriched by a case analysis of the French National Agency for Valorisation of the Research (Anvar). At the end of this study, we suggest that France is now entering a critical phase in which structural reforms have to be undertaken in order to ensure French SMEsâ innovation and competitiveness
LâĂ©volution des politiques du soutien lâinnovation dans les PME en France : le cas de l'Anvar
France, like other countries, seeks to promote its scientific excellence and to increase the competitiveness of its small and medium enterprises (SMEs) by taking full advantage of innovation to sustain economic growth and employment. In France as in other countries, there is no specific policy to support innovation in SMEs but both science and industrial research policies, especially for small businesses, and innovation policies, in which can be identified specific measures to promote technological development and innovation in SMEs. This study focuses on "how", in France, such public policies are defined and organized through different periods and it questions the effectiveness and impact of public interventions aimed at developing French SMEsâ innovation capacity. The study is divided in three parts, following a historical chronology corresponding to major stages of political evolution from the years 1960-1970 till now. These three analytical parts are enriched by a case analysis of the French National Agency for Valorisation of the Research (Anvar). At the end of this study, we suggest that France is now entering a critical phase in which structural reforms have to be undertaken in order to ensure French SMEsâ innovation and competitiveness.La France, comme dâautres pays, cherche Ă valoriser son excellence scientifique et Ă augmenter la compĂ©titivitĂ© de ses petites et moyennes entreprises (PME) pour tirer plein profit de lâinnovation et soutenir la croissance Ă©conomique et lâemploi. Il nây a pas, ni en France ni ailleurs, une politique spĂ©cifique de soutien Ă lâinnovation dans les PME mais des politiques scientifiques et de la recherche industrielle, en particulier en faveur des petites entreprises, et des politiques dâinnovation, dans lesquelles peuvent ĂȘtre identifiĂ©es des mesures spĂ©cifiques visant Ă promouvoir le dĂ©veloppement technologique et lâinnovation dans les PME. Cette Ă©tude sâintĂ©resse Ă la façon dont en France, Ă travers les diffĂ©rentes Ă©poques, ces politiques publiques sont dĂ©finies et organisĂ©es et sâinterroge sur lâefficacitĂ© et lâimpact des interventions publiques dans le dĂ©veloppement de capacitĂ© dâinnovation des PME françaises. Elle se dĂ©roule en trois parties, en respectant une chronologie historique correspondant aux grandes Ă©tapes de lâĂ©volution des politiques depuis les annĂ©es 1960-1970 jusquâĂ prĂ©sent. Ces trois parties analytiques sont enrichies par lâanalyse du cas de lâAgence nationale de valorisation de la recherche (Anvar). A la fin de ce travail, nous suggĂ©rons que la France entre dans une phase critique oĂč des rĂ©formes structurelles doivent ĂȘtre menĂ©es pour assurer le dĂ©veloppement de la compĂ©titivitĂ© des PME et de lâinnovation
An alternating direction implicit spectral method for solving two dimensional multi-term time fractional mixed diffusion and diffusion-wave equations
In this paper, we consider the initial boundary value problem of the two dimensional multi-term time fractional mixed diffusion and diffusion-wave equations. An alternating direction implicit (ADI) spectral method is developed based on Legendre spectral approximation in space and finite difference discretization in time. Numerical stability and convergence of the schemes are proved, the optimal error is O(Nâr+Ï2), where N,Ï,r are the polynomial degree, time step size and the regularity of the exact solution, respectively. We also consider the non-smooth solution case by adding some correction terms. Numerical experiments are presented to confirm our theoretical analysis. These techniques can be used to model diffusion and transport of viscoelastic non-Newtonian fluids.</p
An ExplicitâImplicit Spectral Element Scheme for the Nonlinear Space Fractional Schrödinger Equation
In this paper, we solve the space fractional nonlinear Schrödinger equation (SFNSE) by developing an explicitâimplicit spectral element scheme, which is formulated based on the Legendre spectral element approximation in space and the CrankâNicolson leap frog (CNLF) difference discretization in time. Both mass and energy conservative properties are discussed for the spectral element scheme. Numerical stability and convergence of the scheme are proved. Numerical experiments are performed to confirm the high accuracy and efficiency of the proposed numerical scheme
Fully discrete spectral methods for solving time fractional nonlinear Sine-Gordon equation with smooth and non-smooth solutions
We consider the initial boundary value problem of the time fractional nonlinear SineâGordon equation and the fractional derivative is described in Caputo sense with the order α(1âŻ<âŻÎ±âŻ<âŻ2). Two fully discrete schemes are developed based on Legendre spectral approximation in space and finite difference discretization in time for smooth solutions and non-smooth solutions, respectively. Numerical stability and convergence are analysed. Numerical experiments for both the fully discrete schemes are presented to confirm our theoretical analysis
Recommended from our members
Method for generating spatiotemporal coherency vortices and spatiotemporal dislocation curves
A simple method for designing spatiotemporal coherency vortices (STCVs) and spatiotemporal dislocation curves (STDCs) is introduced by means of coherent-mode representation and Fourier transforms. A partially coherent pulsed beam is represented by an incoherent superposition of a Gaussian and a Hermite-Gaussian pulsed beam with different waist positions. It well demonstrates that there exist STCVs and STDCs in the space-time plane. The detailed numerical calculations are performed to address the dependence of waist distance of two modes, reference position, beam order, distribution of original spectrum, topological charge and mode weights ratio on the STCVs and STDCs. The physical interpretation behind numerical results is shown. A possible scheme for experimental synthesis of the STCVs is proposed. The obtained results may have potential applications in the fields of light-matter interaction, spatiotemporal spin-orbit angular momentum coupling and STCV-based optical trapping and optical manipulation