Nowadays,transmission system operators(TSOs)encounter the challenges of securely operating power grids with high penetration of renewables.In this context,more flexibility is needed than ever to maintain system reliab...Nowadays,transmission system operators(TSOs)encounter the challenges of securely operating power grids with high penetration of renewables.In this context,more flexibility is needed than ever to maintain system reliability.With rapid development of coordinated transmission and distribution technology recently,active distribution networks(ADNs)which have abundant flexible resources,have the potential to provide flexibility to the TSO.Hence,an integrated transmission-distribution flexibility market is proposed in this paper.In the proposed framework,the energy market is first cleared to obtain baseline generation schedules.Then the baseline generation schedules are treated as inputs to the flexibility market.Furthermore,the integrated flexibility market is cleared to facilitate flexibility trading between transmission and distribution networks.To preserve the data privacy of different market participants,an alternating direction method of multipliers(ADMM)based method is utilized to clear the markets in a distributed manner.In the energy market and flexibility market-clearing model,transmission network market clearing models are linear programming(LP)models,and distribution network market clearing models are second order cone programming(SOCP)models.Through the proposed method,only limited information is exchanged between TSO and DSOs.Case studies are conducted on a revised IEEE 30-bus transmission network with two 33-node ADNs.Numerical results demonstrate the proposed flexibility market framework can enhance competitiveness of generation companies in the transmission network and distributed generators(DGs)in the ADNs.Moreover,flexibility purchasing cost is reduced by 17.7%compared to traditional flexibility supplied by generators according to the case study results,and ADNs can gain additional flexibility profit by providing flexibility.展开更多
Tungsten disulfide(WS_2) is a type of anisotropic-layered compound and has broadband saturable absorption features as saturable absorbers(SAs). With WS_2-based SAs, dark solitons in erbium-doped fiber(EDF) lasers are ...Tungsten disulfide(WS_2) is a type of anisotropic-layered compound and has broadband saturable absorption features as saturable absorbers(SAs). With WS_2-based SAs, dark solitons in erbium-doped fiber(EDF) lasers are first obtained. For the generated dark solitons, the center wavelength is measured to be 1530 nm, and the repetition rate is about 116.5 MHz. A series of optical spectra is exhibited. The electrical signal-to-noise ratio is better than 94 d B.Results in this paper demonstrate that WS_2-based SAs are the promising SAs for generating dark solitons in EDF lasers.展开更多
The aim of transit-oriented development(TOD)is to create a livable urban environment by improving the integration between land-use and transportation systems.The capital city of Ethiopia,Addis Ababa,aims to promote a ...The aim of transit-oriented development(TOD)is to create a livable urban environment by improving the integration between land-use and transportation systems.The capital city of Ethiopia,Addis Ababa,aims to promote a sustainable transportation system by launching its first light rail transit(LRT)network to control the current pattern of increased congestion and the need for mass transport.Planning for TOD around existing transit stations helps achieve improved transit choice and encourages local economic development.Therefore,this article proposes a methodology to quantitatively measure the existing TOD in terms of a TOD index within the walkable distance of transit nodes by measuring the criteria that define TOD levels.The TOD index is calculated for areas of 22 stations on the East-West LRT line of Addis Ababa.Depending on the value of the TOD index,certain stations are identified to have a potential TOD but poor transit accessibility.With these results,the recommendation to improve TOD planning can become accurate for each station,depending on its relevant factors.Such results also help identify each station’s potential for TOD planning and its improvements toward future local developments.展开更多
Green transit-oriented development(TOD)is an evolution of the TOD theory,influenced by sustainable development and green urbanism.This advancement expands the environmental and ecological dimensions of conventional TO...Green transit-oriented development(TOD)is an evolution of the TOD theory,influenced by sustainable development and green urbanism.This advancement expands the environmental and ecological dimensions of conventional TOD.However,relevant research has only just started,particularly in combination with high-density cities in Asia.This study measures the built environment of Green TOD and identifies the key factors and characteristics of the Green TOD built environment.An evaluation method for the Green TOD built environment is developed on the basis of the 5D(density,diversity,design,destination,and distance)built environment framework and combined with green urbanism theories.Data from 23 rail station areas in Singapore were collected and analyzed using factor and cluster analysis.Five factors,namely,neighborhood spatial form factor,facility completeness factor,open space factor,high-density mixed land-use factor,and walking amenity factor,are extracted.Twentythree station areas are classified into five clusters.The characteristics and optimization strategies of each cluster are analyzed on the basis of the statistical and graphical analyses.This research displays the characteristics and typology of the Green TOD built environment in an empirical way and offers a foundation for further research in diverse urban contexts.展开更多
It is our great honor and pleasure to be the guest editors for this special issue of the Acta Mathematica Sinica-English Series, a flagship journal of the Chinese Mathematical Society, dedicated to Professor Carlos E....It is our great honor and pleasure to be the guest editors for this special issue of the Acta Mathematica Sinica-English Series, a flagship journal of the Chinese Mathematical Society, dedicated to Professor Carlos E. Kenig from the University of Chicago on the occasion of his 65th birthday.展开更多
The present paper is devoted to a preliminary study towards the establishment of an ergodic theory for stochastic di erential equations(SDEs)with less regular coecients and degenerate noises.These equations are often ...The present paper is devoted to a preliminary study towards the establishment of an ergodic theory for stochastic di erential equations(SDEs)with less regular coecients and degenerate noises.These equations are often derived as mesoscopic limits of complex or huge microscopic systems.By studying the associated Fokker-Planck equation(FPE),we prove the convergence of the time average of globally de ned weak solutions of such an SDE to the set of stationary measures of the FPE under Lyapunov conditions.In the case where the set of stationary measures consists of a single element,the unique stationary measure is shown to be physical.Similar convergence results for the solutions of the FPE are established as well.Some of our convergence results,while being special cases of those contained in Ji et al.(2019)for SDEs with periodic coecients,have weaken the required Lyapunov conditions and are of much simpli ed proofs.Applications to stochastic damping Hamiltonian systems and stochastic slow-fast systems are given.展开更多
Let L be a second-order linear elliptic operator with complex coefficients. It is shown that if the L^p Dirichlet problem for the elliptic system L(u) = 0 in a fixed Lipschitz domain Ω in Rd is solvable for some 1 &l...Let L be a second-order linear elliptic operator with complex coefficients. It is shown that if the L^p Dirichlet problem for the elliptic system L(u) = 0 in a fixed Lipschitz domain Ω in Rd is solvable for some 1 < p = p_0 <2(d-1)/(d-2), then it is solvable for all p satisfying ■ The proof is based on a real-variable argument. It only requires that local solutions of L(u) = 0 satisfy a boundary Cacciopoli inequality.展开更多
This paper is concerned with uniform measure estimates for nodal sets of solutions in elliptic homogenization. We consider a family of second-order elliptic operators {L_ε} in divergence form with rapidly oscillating...This paper is concerned with uniform measure estimates for nodal sets of solutions in elliptic homogenization. We consider a family of second-order elliptic operators {L_ε} in divergence form with rapidly oscillating and periodic coefficients. We show that the(d-1)-dimensional Hausdorff measures of the nodal sets of solutions to L_ε(u_ε) = 0 in a ball in Rdare bounded uniformly in ε > 0. The proof relies on a uniform doubling condition and approximation of u_ε by solutions of the homogenized equation.展开更多
基金supported in part by the joint project of NSFC of China and EPSRC of UK (No.52061635103 and EP/T021969/1)the National Natural Science Foundation of China (No.52007026)。
文摘Nowadays,transmission system operators(TSOs)encounter the challenges of securely operating power grids with high penetration of renewables.In this context,more flexibility is needed than ever to maintain system reliability.With rapid development of coordinated transmission and distribution technology recently,active distribution networks(ADNs)which have abundant flexible resources,have the potential to provide flexibility to the TSO.Hence,an integrated transmission-distribution flexibility market is proposed in this paper.In the proposed framework,the energy market is first cleared to obtain baseline generation schedules.Then the baseline generation schedules are treated as inputs to the flexibility market.Furthermore,the integrated flexibility market is cleared to facilitate flexibility trading between transmission and distribution networks.To preserve the data privacy of different market participants,an alternating direction method of multipliers(ADMM)based method is utilized to clear the markets in a distributed manner.In the energy market and flexibility market-clearing model,transmission network market clearing models are linear programming(LP)models,and distribution network market clearing models are second order cone programming(SOCP)models.Through the proposed method,only limited information is exchanged between TSO and DSOs.Case studies are conducted on a revised IEEE 30-bus transmission network with two 33-node ADNs.Numerical results demonstrate the proposed flexibility market framework can enhance competitiveness of generation companies in the transmission network and distributed generators(DGs)in the ADNs.Moreover,flexibility purchasing cost is reduced by 17.7%compared to traditional flexibility supplied by generators according to the case study results,and ADNs can gain additional flexibility profit by providing flexibility.
基金supported by the National Key Basic Research Program of China (grant nos.2012CB821304,2013CB922401,and 2013CB922402)by the National Natural Science Foundation of China (NSFC) (grant nos.61205064,61378040,and 11078022)+1 种基金by the National Key Technology R&D Program of the Ministry of Science and Technology under grant no.2012BAC23B03by the Fund of State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications,grant no.600100161)
文摘Tungsten disulfide(WS_2) is a type of anisotropic-layered compound and has broadband saturable absorption features as saturable absorbers(SAs). With WS_2-based SAs, dark solitons in erbium-doped fiber(EDF) lasers are first obtained. For the generated dark solitons, the center wavelength is measured to be 1530 nm, and the repetition rate is about 116.5 MHz. A series of optical spectra is exhibited. The electrical signal-to-noise ratio is better than 94 d B.Results in this paper demonstrate that WS_2-based SAs are the promising SAs for generating dark solitons in EDF lasers.
文摘The aim of transit-oriented development(TOD)is to create a livable urban environment by improving the integration between land-use and transportation systems.The capital city of Ethiopia,Addis Ababa,aims to promote a sustainable transportation system by launching its first light rail transit(LRT)network to control the current pattern of increased congestion and the need for mass transport.Planning for TOD around existing transit stations helps achieve improved transit choice and encourages local economic development.Therefore,this article proposes a methodology to quantitatively measure the existing TOD in terms of a TOD index within the walkable distance of transit nodes by measuring the criteria that define TOD levels.The TOD index is calculated for areas of 22 stations on the East-West LRT line of Addis Ababa.Depending on the value of the TOD index,certain stations are identified to have a potential TOD but poor transit accessibility.With these results,the recommendation to improve TOD planning can become accurate for each station,depending on its relevant factors.Such results also help identify each station’s potential for TOD planning and its improvements toward future local developments.
基金This research was funded by the China Postdoctoral Science Foundation(2020M673222)the Chengdu Philosophy and Social Science Planning Project(2020-RK00-00322-ZF).
文摘Green transit-oriented development(TOD)is an evolution of the TOD theory,influenced by sustainable development and green urbanism.This advancement expands the environmental and ecological dimensions of conventional TOD.However,relevant research has only just started,particularly in combination with high-density cities in Asia.This study measures the built environment of Green TOD and identifies the key factors and characteristics of the Green TOD built environment.An evaluation method for the Green TOD built environment is developed on the basis of the 5D(density,diversity,design,destination,and distance)built environment framework and combined with green urbanism theories.Data from 23 rail station areas in Singapore were collected and analyzed using factor and cluster analysis.Five factors,namely,neighborhood spatial form factor,facility completeness factor,open space factor,high-density mixed land-use factor,and walking amenity factor,are extracted.Twentythree station areas are classified into five clusters.The characteristics and optimization strategies of each cluster are analyzed on the basis of the statistical and graphical analyses.This research displays the characteristics and typology of the Green TOD built environment in an empirical way and offers a foundation for further research in diverse urban contexts.
文摘It is our great honor and pleasure to be the guest editors for this special issue of the Acta Mathematica Sinica-English Series, a flagship journal of the Chinese Mathematical Society, dedicated to Professor Carlos E. Kenig from the University of Chicago on the occasion of his 65th birthday.
基金The first author was supported by China Scholarship Council.The second author was supported by University of Alberta,and Natural Sciences and Engineering Research Council of Canada(Grant Nos.RGPIN-2018-04371 and DGECR-2018-00353)The third author was supported by Pacific Institute for the Mathematical Sciences-Canadian Statistical Sciences Institute Postdoctoral Fellowship,Pacific Institute for the Mathematical Sciences-Collaborative Research Group Grant,National Natural Science Foundation of China(Grant Nos.11771026 and 11471344)+2 种基金the Pacific Institute for the Mathematical Sciences-University of Washington site through National Science Foundation of USA(Grant No.DMS-1712701)The fourth author was supported by Natural Sciences and Engineering Research Council of Canada Discovery(Grant No.1257749)Pacific Institute for the Mathematical Sciences-Collaborative Research Group Grant,University of Alberta,and Jilin University.
文摘The present paper is devoted to a preliminary study towards the establishment of an ergodic theory for stochastic di erential equations(SDEs)with less regular coecients and degenerate noises.These equations are often derived as mesoscopic limits of complex or huge microscopic systems.By studying the associated Fokker-Planck equation(FPE),we prove the convergence of the time average of globally de ned weak solutions of such an SDE to the set of stationary measures of the FPE under Lyapunov conditions.In the case where the set of stationary measures consists of a single element,the unique stationary measure is shown to be physical.Similar convergence results for the solutions of the FPE are established as well.Some of our convergence results,while being special cases of those contained in Ji et al.(2019)for SDEs with periodic coecients,have weaken the required Lyapunov conditions and are of much simpli ed proofs.Applications to stochastic damping Hamiltonian systems and stochastic slow-fast systems are given.
文摘Let L be a second-order linear elliptic operator with complex coefficients. It is shown that if the L^p Dirichlet problem for the elliptic system L(u) = 0 in a fixed Lipschitz domain Ω in Rd is solvable for some 1 < p = p_0 <2(d-1)/(d-2), then it is solvable for all p satisfying ■ The proof is based on a real-variable argument. It only requires that local solutions of L(u) = 0 satisfy a boundary Cacciopoli inequality.
基金supported in part by NSF(Grant No.DMS-1501000)supported in part by NSF(Grant No.DMS-1600520)
文摘This paper is concerned with uniform measure estimates for nodal sets of solutions in elliptic homogenization. We consider a family of second-order elliptic operators {L_ε} in divergence form with rapidly oscillating and periodic coefficients. We show that the(d-1)-dimensional Hausdorff measures of the nodal sets of solutions to L_ε(u_ε) = 0 in a ball in Rdare bounded uniformly in ε > 0. The proof relies on a uniform doubling condition and approximation of u_ε by solutions of the homogenized equation.
