Several research studies have proven that eliciting and predicting the impact of human activity on ecosystem services will be crucial to support stakeholders’ awareness and to decide how to interact with the environm...Several research studies have proven that eliciting and predicting the impact of human activity on ecosystem services will be crucial to support stakeholders’ awareness and to decide how to interact with the environment in a more sustainable manner. In this sense, the ecosystems known as road verges are particularly important because of their length and surface at an international scale, and their role in mitigating the damage done by roads. Plant pollination by insects is one of the most important ecosystem services. Because of its nature and the fact that they extend across a variety of landscapes, roadside can contribute to the maintenance of healthy ecosystems, under the condition of adapted management practices. This research is the first attempt to develop a System Dynamics-based aiming to estimate the ecological and economic impact of maintenance on the road verge pollination service in France. Maintenance strategies of road verges are simulated to compare their performance. The results show that there are ways to improve current maintenance strategies in terms of pollination value, but also that the model needs to consider other ecosystem services and synergistic effects that could further affect pollination to obtain more accurate estimations.展开更多
In this note, we study a discrete time approximation for the solution of a class of delayed stochastic differential equations driven by a fractional Brownian motion with Hurst parameter H ∈(1/2,1). In order to prove ...In this note, we study a discrete time approximation for the solution of a class of delayed stochastic differential equations driven by a fractional Brownian motion with Hurst parameter H ∈(1/2,1). In order to prove convergence, we use rough paths techniques. Theoretical bounds are established and numerical simulations are displayed.展开更多
Background: Phase II cardiac rehabilitation (CR) is a class IA indication in patients suffering a cardiovascular event (CV). Current guidelines suggest 36 exercise sessions over a period of 3 months. The main aim of t...Background: Phase II cardiac rehabilitation (CR) is a class IA indication in patients suffering a cardiovascular event (CV). Current guidelines suggest 36 exercise sessions over a period of 3 months. The main aim of this study was to analyze the rate of adherence to a cardiac rehabilitation program and the factors influencing it. Methods: This was a cross-sectional study in 421 secondary prevention patients, who assisted to a Phase-II-CR program between 2007 and 2014. At baseline and program end, patients completed a 6-minute walk test and the Short-Form 36 Health Survey (SF-36). Vital signs and anthropometric measurements were also collected. Adherence was quantified as the percentage of individuals who attended all 36 sessions of the program. Factors considered for affecting adherence included: cardiovascular risk factors (RFs), type of health insurance (public or private), aerobic capacity, and SF-36 score parameters. Results: Adherence to Phase-II-CR was 33%, with no significant differences between men and women. The regression model fully adjusted for age, sex, RFs, type of health insurance and SF-36 score, showed that a SF-36 score <50 on physical health (odds ratio (OR): 11.47;3.99 - 32.99;p < 0.0001) and smoking (OR: 4.41;1.25 - 15.62;p = 0.02) were strong predictors for non-adherence. A trend for better adherence was observed in subjects older than 50 years compared to those aged between 17 and 50 years (37% versus 23%, respectively;p = 0.05). No significant differences were observed in adherence according to RFs clustering. Conclusions: Adherence to Phase-II-CR is low in our population. Patient-related factors, such as SF-36 score and smoking, were the best determinants of Phase-II-CR adherence. Health system-related factors did not influence adherence in this population. Prospective studies are warranted to determine all the factors which may influence adherence to Phase-II-CR programs.展开更多
The main object of this paper is to study an extension of the half normal distribution defined by adding a positive truncation to it. The new model is more flexible than the half-normal distribution and contains the h...The main object of this paper is to study an extension of the half normal distribution defined by adding a positive truncation to it. The new model is more flexible than the half-normal distribution and contains the half normal distribution as a special case. Properties of this distribution, such as moments, hazard function and entropy are studied and parameters estimation is dealt with by using moments and maximum likelihood. A real data application indicates good fit performance of the new model when compared to other competitors in literatures.展开更多
A paper, "Non-existence of Shilnikov chaos in continuous-time systems" was published in the journal Applied Mathematics and Mechanics(English Edition).The authors gave sufficient conditions for the non-exist...A paper, "Non-existence of Shilnikov chaos in continuous-time systems" was published in the journal Applied Mathematics and Mechanics(English Edition).The authors gave sufficient conditions for the non-existence of homoclinic and heteroclinic orbits in an nth-order autonomous system.Unfortunately,we show in this comment that the proof presented is erroneous and the result is invalid.We also provide two counterexamples of the wrong criterion stated by the authors.展开更多
A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding ...A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding to two different structural scales. A finite number of imperfect contact conditions are analyzed at each of the scales. The reiterated homogenization method(RHM) is used to construct a formal asymptotic solution. The homogenized problem, the local problems, and the corresponding effective coefficients are obtained. A variational formulation is derived to obtain an estimate to prove the proximity between the solutions of the original problem and the homogenized problem. Numerical computations are used to illustrate both the convergence of the solutions and the gain of the effective properties of a three-scale heterogeneous 1D laminate with respect to their two-scale counterparts. The theoretical and practical ideas exposed here could be used to mathematically model multidimensional problems involving multiscale composite materials with imperfect contact at the interfaces.展开更多
The improved Boussinesq equation is solved with classical finite element method using the most basic Lagrange element k = 1, which leads us to a second order nonlinear ordinary differential equations system in time;th...The improved Boussinesq equation is solved with classical finite element method using the most basic Lagrange element k = 1, which leads us to a second order nonlinear ordinary differential equations system in time;this can be solved by any standard accurate numerical method for example Runge-Kutta-Fehlberg. The technique is validated with a typical example and a fourth order convergence in space is confirmed;the 1- and 2-soliton solutions are used to simulate wave travel, wave splitting and interaction;solution blow up is described graphically. The computer symbolic system MathLab is quite used for numerical simulation in this paper;the known results in the bibliography are confirmed.展开更多
The aim of the present paper is to state an asymptotic property Ρ of Shannon’s sampling theorem type, based on normalized cardinal sines, and keeping constant the sampling frequency of a not necessarilly band...The aim of the present paper is to state an asymptotic property Ρ of Shannon’s sampling theorem type, based on normalized cardinal sines, and keeping constant the sampling frequency of a not necessarilly band- limited signal. It generalizes in the limit the results stated by Marvasti et al. [7] and Agud et al. [1]. We show that Ρ is fulfilled for any constant signal working for every given sampling frequency. Moreover, we conjecture that Gaussian maps of the form e-Λt2 ,Λ∈R+, hold Ρ. We support this conjecture by proving the equality given by for the three first coefficients of the power series representation of e-Λt2 .展开更多
Tumor invasion follows a complex mechanism which involves cell migration and proliferation.To study the processes in which primary and secondary metastases invade and damage the normal cells,mathematical models are of...Tumor invasion follows a complex mechanism which involves cell migration and proliferation.To study the processes in which primary and secondary metastases invade and damage the normal cells,mathematical models are often extremely useful.In this paper,we present a mathematical model of acid-mediated tumor growth consisting of radially symmetric reaction-diffusion equations.The assumption on the radial symmetry of the solutions is imposed here in view that tumors present spherical symmetry at the microscopic level.Moreover,we consider various empirical mechanisms which describe the propagation of tumors by considering cancer cells,normal cells,and the concentration of H+ions.Among other assumptions,we suppose that these components follow logistictype growth rates.Evidently,this is an important difference with respect to various other mathematical models for tumor growth available in the literature.Moreover,we also add competition terms of normal and tumor cells growth.We carry out a balancing study of the equations of the model,and a numerical model is proposed to produce simulations.Various practical remarks derived from our assumptions are provided in the discussion of our simulations.展开更多
The authors study the asymptotic behaviour of solutions of the heat equation and a number of evolution equations using scaling techniques. It is proved that in the framework of bounded data stabilization need not occu...The authors study the asymptotic behaviour of solutions of the heat equation and a number of evolution equations using scaling techniques. It is proved that in the framework of bounded data stabilization need not occur and the general asymptotic behaviour is complex. This behaviour reflects for large times, even on compact sets, the complexity of the initial data at infinity.展开更多
Photoconductive switches were the key components that allowed the generation and detection of coherent broadband electromagnetic pulses at terahertz frequencies, opening the possibility for performing spectroscopy and...Photoconductive switches were the key components that allowed the generation and detection of coherent broadband electromagnetic pulses at terahertz frequencies, opening the possibility for performing spectroscopy and,therefore, measuring complex dielectric properties of materials in this band, which was mostly unexplored. In this paper, we present a brief introduction to the operation principles of these devices. Subsequently, we present a review of the current state-of-the-art in this field and discuss the challenges to be faced in future development of these devices.展开更多
Group theory(GT) provides a rigorous framework for studying symmetries in various disciplines in physics ranging from quantum field theories and the standard model to fluid mechanics and chaos theory. To date, the app...Group theory(GT) provides a rigorous framework for studying symmetries in various disciplines in physics ranging from quantum field theories and the standard model to fluid mechanics and chaos theory. To date, the application of such a powerful tool in optical physics remains limited. Over the past few years however, several quantum-inspired symmetry principles(such as parity-time invariance and supersymmetry) have been introduced in optics and photonics for the first time. Despite the intense activities in these new research directions, only few works utilized the power of group theory. Motivated by this status quo, here we present a brief overview of the application of GT in optics, deliberately choosing examples that illustrate the power of this tool in both continuous and discrete setups. We hope that this review will stimulate further research that exploits the full potential of GT for investigating various symmetry paradigms in optics, eventually leading to new photonic devices.展开更多
In this paper we give necessary and sufficient conditions for a comodule magma over a weak Hopf quasigroup to have a total integral,thus extending the theories developed in the Hopf algebra,weak Hopf algebra and non-a...In this paper we give necessary and sufficient conditions for a comodule magma over a weak Hopf quasigroup to have a total integral,thus extending the theories developed in the Hopf algebra,weak Hopf algebra and non-associative Hopf algebra contexts.From this result we also deduce a version of Maschke’s theorems for right(H,B)-Hopf triples associated to a weak Hopf quasigroup H and a right H-comodule magma B.展开更多
We extend the construction and analysis of the non-overlapping Schwarz preconditioners proposed in[2,3]to the(non-consistent)super penalty discontinuous Galerkin methods introduced in[5]and[8].We show that the resulti...We extend the construction and analysis of the non-overlapping Schwarz preconditioners proposed in[2,3]to the(non-consistent)super penalty discontinuous Galerkin methods introduced in[5]and[8].We show that the resulting preconditioners are scalable,and we provide the convergence estimates.We also present numerical experiments confirming the sharpness of the theoretical results.展开更多
The authors prove that flat ground state solutions(i.e. minimizing the energy and with gradient vanishing on the boundary of the domain) of the Dirichlet problem associated to some semilinear autonomous elliptic equat...The authors prove that flat ground state solutions(i.e. minimizing the energy and with gradient vanishing on the boundary of the domain) of the Dirichlet problem associated to some semilinear autonomous elliptic equations with a strong absorption term given by a non-Lipschitz function are unstable for dimensions N = 1, 2 and they can be stable for N ≥ 3 for suitable values of the involved exponents.展开更多
In this paper,we find all positive squarefree integers d satisfying that the Pell equation X^2-d Y^2=±1 has at least two positive integer solutions(X,Y)and(X′,Y′)such that both X and X′have Zeckendorf represen...In this paper,we find all positive squarefree integers d satisfying that the Pell equation X^2-d Y^2=±1 has at least two positive integer solutions(X,Y)and(X′,Y′)such that both X and X′have Zeckendorf representations with at most two terms.展开更多
文摘Several research studies have proven that eliciting and predicting the impact of human activity on ecosystem services will be crucial to support stakeholders’ awareness and to decide how to interact with the environment in a more sustainable manner. In this sense, the ecosystems known as road verges are particularly important because of their length and surface at an international scale, and their role in mitigating the damage done by roads. Plant pollination by insects is one of the most important ecosystem services. Because of its nature and the fact that they extend across a variety of landscapes, roadside can contribute to the maintenance of healthy ecosystems, under the condition of adapted management practices. This research is the first attempt to develop a System Dynamics-based aiming to estimate the ecological and economic impact of maintenance on the road verge pollination service in France. Maintenance strategies of road verges are simulated to compare their performance. The results show that there are ways to improve current maintenance strategies in terms of pollination value, but also that the model needs to consider other ecosystem services and synergistic effects that could further affect pollination to obtain more accurate estimations.
基金supported by MATH-AmSud 18-MATH-07 SaS MoTiDep ProjectHERMES project 41305+1 种基金partially supported by the Project ECOS-CONICYT C15E05,REDES 150038,MATH-AmSud 18-MATH-07 SaS MoTiDep Project and Fondecyt(1171335)supported by NSF(Grant DMS-1613163)
文摘In this note, we study a discrete time approximation for the solution of a class of delayed stochastic differential equations driven by a fractional Brownian motion with Hurst parameter H ∈(1/2,1). In order to prove convergence, we use rough paths techniques. Theoretical bounds are established and numerical simulations are displayed.
文摘Background: Phase II cardiac rehabilitation (CR) is a class IA indication in patients suffering a cardiovascular event (CV). Current guidelines suggest 36 exercise sessions over a period of 3 months. The main aim of this study was to analyze the rate of adherence to a cardiac rehabilitation program and the factors influencing it. Methods: This was a cross-sectional study in 421 secondary prevention patients, who assisted to a Phase-II-CR program between 2007 and 2014. At baseline and program end, patients completed a 6-minute walk test and the Short-Form 36 Health Survey (SF-36). Vital signs and anthropometric measurements were also collected. Adherence was quantified as the percentage of individuals who attended all 36 sessions of the program. Factors considered for affecting adherence included: cardiovascular risk factors (RFs), type of health insurance (public or private), aerobic capacity, and SF-36 score parameters. Results: Adherence to Phase-II-CR was 33%, with no significant differences between men and women. The regression model fully adjusted for age, sex, RFs, type of health insurance and SF-36 score, showed that a SF-36 score <50 on physical health (odds ratio (OR): 11.47;3.99 - 32.99;p < 0.0001) and smoking (OR: 4.41;1.25 - 15.62;p = 0.02) were strong predictors for non-adherence. A trend for better adherence was observed in subjects older than 50 years compared to those aged between 17 and 50 years (37% versus 23%, respectively;p = 0.05). No significant differences were observed in adherence according to RFs clustering. Conclusions: Adherence to Phase-II-CR is low in our population. Patient-related factors, such as SF-36 score and smoking, were the best determinants of Phase-II-CR adherence. Health system-related factors did not influence adherence in this population. Prospective studies are warranted to determine all the factors which may influence adherence to Phase-II-CR programs.
基金supported by SEMILLERO-UA2014(Chile)supported by CNPq and Fapesp(Brasil)
文摘The main object of this paper is to study an extension of the half normal distribution defined by adding a positive truncation to it. The new model is more flexible than the half-normal distribution and contains the half normal distribution as a special case. Properties of this distribution, such as moments, hazard function and entropy are studied and parameters estimation is dealt with by using moments and maximum likelihood. A real data application indicates good fit performance of the new model when compared to other competitors in literatures.
基金supported by the Ministerio de Educacion y Ciencia,Plan Nacional I+D+I co-financed with FEDER Funds(No.MTM2010-20907-C02)the Consejeria de Educacion y Ciencia de la Juntade Andalucia(Nos.FQM-276,TIC-0130,and P08-FQM-03770)
文摘A paper, "Non-existence of Shilnikov chaos in continuous-time systems" was published in the journal Applied Mathematics and Mechanics(English Edition).The authors gave sufficient conditions for the non-existence of homoclinic and heteroclinic orbits in an nth-order autonomous system.Unfortunately,we show in this comment that the proof presented is erroneous and the result is invalid.We also provide two counterexamples of the wrong criterion stated by the authors.
基金Project supported by the Desenvolvimento e Aplicaoes de Mtodos Matemticos de Homogeneizaao(CAPES)(No.88881.030424/2013-01)the Homogeneizao Reiterada Aplicada a Meios Dependentes de Múltiplas Escalas con Contato Imperfeito Entre as Fases(CNPq)(Nos.450892/2016-6and 303208/2014-7)the Caracterizacin de Propiedades Efectivas de Tejidos Biolgicos Sanos y Cancerosos(CONACYT)(No.2016–01–3212)
文摘A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding to two different structural scales. A finite number of imperfect contact conditions are analyzed at each of the scales. The reiterated homogenization method(RHM) is used to construct a formal asymptotic solution. The homogenized problem, the local problems, and the corresponding effective coefficients are obtained. A variational formulation is derived to obtain an estimate to prove the proximity between the solutions of the original problem and the homogenized problem. Numerical computations are used to illustrate both the convergence of the solutions and the gain of the effective properties of a three-scale heterogeneous 1D laminate with respect to their two-scale counterparts. The theoretical and practical ideas exposed here could be used to mathematically model multidimensional problems involving multiscale composite materials with imperfect contact at the interfaces.
文摘The improved Boussinesq equation is solved with classical finite element method using the most basic Lagrange element k = 1, which leads us to a second order nonlinear ordinary differential equations system in time;this can be solved by any standard accurate numerical method for example Runge-Kutta-Fehlberg. The technique is validated with a typical example and a fourth order convergence in space is confirmed;the 1- and 2-soliton solutions are used to simulate wave travel, wave splitting and interaction;solution blow up is described graphically. The computer symbolic system MathLab is quite used for numerical simulation in this paper;the known results in the bibliography are confirmed.
基金partially supported by MCI(Ministerio de Ciencia e Innovacion)and FEDER(Fondo Europeo Desarrollo Regional),grant number MTM2008--03679/MTMFundacion Seneca de la Region de Murcia,grant number 08667/PI/08JCCM(Junta de Comunidades de Castilla-La Mancha),grant number PEII09-0220-0222.
文摘The aim of the present paper is to state an asymptotic property Ρ of Shannon’s sampling theorem type, based on normalized cardinal sines, and keeping constant the sampling frequency of a not necessarilly band- limited signal. It generalizes in the limit the results stated by Marvasti et al. [7] and Agud et al. [1]. We show that Ρ is fulfilled for any constant signal working for every given sampling frequency. Moreover, we conjecture that Gaussian maps of the form e-Λt2 ,Λ∈R+, hold Ρ. We support this conjecture by proving the equality given by for the three first coefficients of the power series representation of e-Λt2 .
基金wishes to acknowledge the financial support from the National Council of Science and Technology of Mexico(CONACYT)through grant A1-S-45928.
文摘Tumor invasion follows a complex mechanism which involves cell migration and proliferation.To study the processes in which primary and secondary metastases invade and damage the normal cells,mathematical models are often extremely useful.In this paper,we present a mathematical model of acid-mediated tumor growth consisting of radially symmetric reaction-diffusion equations.The assumption on the radial symmetry of the solutions is imposed here in view that tumors present spherical symmetry at the microscopic level.Moreover,we consider various empirical mechanisms which describe the propagation of tumors by considering cancer cells,normal cells,and the concentration of H+ions.Among other assumptions,we suppose that these components follow logistictype growth rates.Evidently,this is an important difference with respect to various other mathematical models for tumor growth available in the literature.Moreover,we also add competition terms of normal and tumor cells growth.We carry out a balancing study of the equations of the model,and a numerical model is proposed to produce simulations.Various practical remarks derived from our assumptions are provided in the discussion of our simulations.
文摘The authors study the asymptotic behaviour of solutions of the heat equation and a number of evolution equations using scaling techniques. It is proved that in the framework of bounded data stabilization need not occur and the general asymptotic behaviour is complex. This behaviour reflects for large times, even on compact sets, the complexity of the initial data at infinity.
文摘Photoconductive switches were the key components that allowed the generation and detection of coherent broadband electromagnetic pulses at terahertz frequencies, opening the possibility for performing spectroscopy and,therefore, measuring complex dielectric properties of materials in this band, which was mostly unexplored. In this paper, we present a brief introduction to the operation principles of these devices. Subsequently, we present a review of the current state-of-the-art in this field and discuss the challenges to be faced in future development of these devices.
基金support from the Photonics and Mathematical Optics Group at Tecnologico de Monterrey and Consorcio enóptica Aplicada through CONACYT FORDECYT#290259 project grantsupport from Henes Center for Quantum Phenomena,Michigan Technological Universitysupport from Spanish MINECO projects FIS2014-57387-C3-3P and DPI2013-47100-C2-1-P
文摘Group theory(GT) provides a rigorous framework for studying symmetries in various disciplines in physics ranging from quantum field theories and the standard model to fluid mechanics and chaos theory. To date, the application of such a powerful tool in optical physics remains limited. Over the past few years however, several quantum-inspired symmetry principles(such as parity-time invariance and supersymmetry) have been introduced in optics and photonics for the first time. Despite the intense activities in these new research directions, only few works utilized the power of group theory. Motivated by this status quo, here we present a brief overview of the application of GT in optics, deliberately choosing examples that illustrate the power of this tool in both continuous and discrete setups. We hope that this review will stimulate further research that exploits the full potential of GT for investigating various symmetry paradigms in optics, eventually leading to new photonic devices.
基金supported by Ministerio de Economía y Competi-tividad(Spain),grant MTM2016-79661-P(AEI/FEDER,UE,support included).
文摘In this paper we give necessary and sufficient conditions for a comodule magma over a weak Hopf quasigroup to have a total integral,thus extending the theories developed in the Hopf algebra,weak Hopf algebra and non-associative Hopf algebra contexts.From this result we also deduce a version of Maschke’s theorems for right(H,B)-Hopf triples associated to a weak Hopf quasigroup H and a right H-comodule magma B.
基金The work was carried out while the second author was visiting the Istituto di Matematica Applicata e Tecnologie Informatiche of the CNR in PaviaShe thanks the Institute for the kind hospitalityThe first author has been supported by ADIGMA project within the 3rd Call of the 6th European Research Framework Programme.The second author has been supported by MTM2005−00714 of the Spanish MEC and by SIMUMAT of CAM.
文摘We extend the construction and analysis of the non-overlapping Schwarz preconditioners proposed in[2,3]to the(non-consistent)super penalty discontinuous Galerkin methods introduced in[5]and[8].We show that the resulting preconditioners are scalable,and we provide the convergence estimates.We also present numerical experiments confirming the sharpness of the theoretical results.
基金supported by the projects of the DGISPI(Spain)(Ref.MTM2011-26119,MTM2014-57113)the UCM Research Group MOMAT(Ref.910480)
文摘The authors prove that flat ground state solutions(i.e. minimizing the energy and with gradient vanishing on the boundary of the domain) of the Dirichlet problem associated to some semilinear autonomous elliptic equations with a strong absorption term given by a non-Lipschitz function are unstable for dimensions N = 1, 2 and they can be stable for N ≥ 3 for suitable values of the involved exponents.
基金supported by the project from Universidad del Valle(Grant No.71079)supported by NRF of South Africa(Grant No.CPRR160325161141)an A-Rated Scientist Award from the NRF of South Africa and by Czech Granting Agency(Grant No.17-02804S)。
文摘In this paper,we find all positive squarefree integers d satisfying that the Pell equation X^2-d Y^2=±1 has at least two positive integer solutions(X,Y)and(X′,Y′)such that both X and X′have Zeckendorf representations with at most two terms.
