1,720,972 research outputs found
Existence theorems for some abstract nonlinear non-autonomous systems with delays
Full text linkFor some abstract classes of nonlinear non-autonomous systems with variable and state-dependent delays existence, non-existence and multiplicity of periodic solutions are discussed. To illustrate the efficiency of the method, we obtain some well-known results for applied systems as corollaries of our existence theorems.Fil: Amster, Pablo Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santalo". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santalo"; ArgentinaFil: Idels, Lev. Vancouver Island University; Canad
Existence of periodic solutions in the modified Wheldon model of CML
Full text linkThe Wheldon model (1975) of a chronic myelogenous leukemia (CML) dynamics is modified and enriched by introduction of a time-varying microenvironment and time-dependent drug efficacies. The resulting model is a special class of nonautonomous nonlinear system of differential equations with delays. Via topological methods, the existence of positive periodic solutions is proven. We introduce our main insight and formulate some relevant open problems and conjectures.Fil: Amster, Pablo Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santalo"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; ArgentinaFil: Balderrama, Rocio Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santalo"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; ArgentinaFil: Idels, Lev. Vancouver Island University. Departament of Mathematics; Canad
Harvesting fisheries management strategies with modified effort function
No full textThis is a pre-copyedited, author-produced version of an article published as: Idels, L.V. & Wang, M. (2008). Harvesting fisheries management strategies with modified effort function. International Journal of Modelling, Identification and Control, 3(1), 83-87. DOI: 10.1504/IJMIC.2008.018188.
International Journal of Modelling, Identification and Control is available online at: http://www.inderscienceonline.com/loi/ijmic and this article is available at: http://dx.doi.org/10.1504/IJMIC.2008.018188.In traditional harvesting model, a fishing effort, E, is defined by the fishing intensity and does not address the inverse effect of fish abundance on the fishing effort. In this paper, based on a canonical differential equation model, we developed a new fishing effort model which relies on the density effect of fish population. We obtained new differential equations to describe certain standard Fisheries management strategies. This study concludes that a control parameter β( the magnitude of the effect of the fish population size on the fishing effort function E), changes not only the rate at which the population goes to equilibrium, but also the equilibrium values. To examine systematically the consequences of different harvesting strategies, we used numerical simulations and qualitative analysis of six fishery strategies, e.g., proportional harvesting, threshold harvesting, proportional threshold harvesting, and seasonal and rotational harvesting.https://viuspace.viu.ca/bitstream/handle/10613/3039/Idels.IJMIC.pdf?sequence=3This is a pre-copyedited, author-produced version of an article published as: Idels, L.V. & Wang, M. (2008). Harvesting fisheries management strategies with modified effort function. International Journal of Modelling, Identification and Control, 3(1), 83-87. DOI: 10.1504/IJMIC.2008.018188.
International Journal of Modelling, Identification and Control is available online at: http://www.inderscienceonline.com/loi/ijmic and this article is available at: http://dx.doi.org/10.1504/IJMIC.2008.018188.Pre-print versio
New applications of M-matrix to stability of high-order linear delayed equations
No full textThis is a pre-copyedited, author-produced version of an article which was published as: Amster, P. & Idels, L. (2016). New applications of the M-matrix methods to stability of high-order linear delayed equations. Applied Mathematics Letters, 54, 1-6. DOI: 10.1016/j.aml.2015.10.008
More information about Applied Mathematics Letters can be found at:
http://www.sciencedirect.com/journal/applied-mathematics-letters, and the final version of this article is available at: http://dx.doi.org/10.1016/j.aml.2015.10.008.A substitution is introduced which exploits the parameters of the high-order delayed linear non-autonomous models and consequently allows the use of the M-matrix methods for the stability analysis. To demonstrate the efficacy of the proposed algorithm we obtain explicit and practical stability conditions for the second and third order non-autonomous delayed models.This is a pre-copyedited, author-produced version of an article which was published as: Amster, P. & Idels, L. (2016). New applications of the M-matrix methods to stability of high-order linear delayed equations. Applied Mathematics Letters, 54, 1-6. DOI: 10.1016/j.aml.2015.10.008
More information about Applied Mathematics Letters can be found at:
http://www.sciencedirect.com/journal/applied-mathematics-letters, and the final version of this article is available at: http://dx.doi.org/10.1016/j.aml.2015.10.008.P. Amster was partially supported by grant UBACyt 20020120100029BA and L. Idels was partially supported by NSERC GRF VIU fund.Post-print versio
Periodic solutions of nonautonomous Mackey-type systems with delays
No full textThis is a pre-copyedited, pre-peer reviewed, author produced manuscript version of an article published as: Amster, P. & Idels, L. (2013). Periodic solutions of nonautonomous Mackey-type systems with delays. Journal of Abstract Differential Equations and Applications, 4(1), 11-22.
Journal of Abstract Differential Equations and Applications is available online at:
http://math-res-pub.org/jadea and this article is available at:
http://math-res-pub.org/jadea/4/1/periodic-solutions-nonautonomous-mackey-type-systems-delaysNonautonomous systems of delay differential equations, that model classical
Mackey-type hematopoietic stem cell dynamics and Mackey-type circuit systems, are under study. Explicit sufficient and necessary conditions for the existence of positive periodic solutions were obtained via topological methods. Numerical simulations have also been presented to demonstrate the theoretical analysis.https://viuspace.viu.ca/bitstream/handle/10613/2739/Idels.JADEA.pdf?sequence=3This is a pre-copyedited, pre-peer reviewed, author produced manuscript version of an article published as: Amster, P. & Idels, L. (2013). Periodic solutions of nonautonomous Mackey-type systems with delays. Journal of Abstract Differential Equations and Applications, 4(1), 11-22.
Journal of Abstract Differential Equations and Applications is available online at:
http://math-res-pub.org/jadea and this article is available at:
http://math-res-pub.org/jadea/4/1/periodic-solutions-nonautonomous-mackey-type-systems-delaysPre-print versio
Stability analysis of periodic Fox production models
No full textIn this paper we introduce a nonlinear Fox surplus production model in a periodic environment. The existence and stability of the periodic solutions of nonautonomous nonlinear differential equation (A) are analyzed. Sufficient conditions are obtained for the global attractivity of positive periodic solutions. Our results extend those the well-known results recently obtained by Brauer for a periodic Gompertzian model. We study the combined effects of periodically varying carrying capacity, inherent growth rates, and periodic harvesting of the population. Some numerical simulations illustrate how the Fox model is able to capture the trend in the data for Pacific Ocean perch obtained by the Pacific Biological Station (Nanaimo, BC).https://viuspace.viu.ca/bitstream/handle/10613/2615/Idels.CAMQ.pdf?sequence=4This is an electronic version of an article published as: Idels, L. (2006). Stability analysis of periodic Fox production models. Canadian Applied Mathematics Quarterly, 14(3), 331-341. Canadian Applied Mathematics Quarterly is available online at http://www.math.ualberta.ca/ami/camq.html and this article is available at: http://www.math.ualberta.ca/ami/CAMQ/table_of_content/vol_14/14_3f.ht
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Oscillation and asymptotic stability of a delay differential equation with Richard's nonlinearity
No full textWe obtain sufficient conditions for oscillation of solutions, and for asymptotical stability of the positive equilibrium, of a scalar nonlinear delay differential equation (see abstract image).https://viuspace.viu.ca/bitstream/handle/10613/2618/Idels.Oscillation.pdf?sequence=3This is an electronic version of an article published as: Berezansky, L. & Idels, L. (2005). Oscillation and
asymptotic stability of a delay differential equation with Richard’s nonlinearity. Electronic Journal of
Differential Equations, 2005(Conference 12), 21-27. Electronic Journal of Differential Equations is
available online at: http://ejde.math.txstate.edu/ and this article is available at:
http://ejde.math.txstate.edu/conf-proc/12/b1/berezansky.pdfThis paper was submitted by the authors in the 2004 Conference on Differential Equations and Applications in Mathematical Biology, Nanaimo, BC (July 18-23, 2004). It was refereed and accepted for publication in the special issue of the Electronic Differential Equations
Stability tests for second order linear and nonlinear delayed models
No full textThis is a pre-copyedited, author-produced version of an article published as: Berezansky, L., Braverman, E., & Idels, L. (2015). Stability tests for second order linear and nonlinear delayed models. Nonlinear Differential Equations and Applications, 22(6), 1523-1543. DOI: 10.1007/s00030-015-0334-1.
The final publication is available at Springer via http://dx.doi.org/10.1007/s00030-015-0334-1For the nonlinear second order Lienard-type equations with time-varying delays (see abstract equation image) global asymptotic stability conditions are obtained. The results are based on the new sufficient stability conditions for relevant linear equations and are applied to derive explicit stability conditions for the nonlinear Kaldor–Kalecki business cycle model. We also explore multistability of the sunflower non-autonomous equation and its modifications.https://viuspace.viu.ca/bitstream/handle/10613/3042/Idels.NODEA.2015.pdf?sequence=4This is a pre-copyedited, author-produced version of an article published as: Berezansky, L., Braverman, E., & Idels, L. (2015). Stability tests for second order linear and nonlinear delayed models. Nonlinear Differential Equations and Applications, 22(6), 1523-1543. DOI: 10.1007/s00030-015-0334-1.
The final publication is available at Springer via http://dx.doi.org/10.1007/s00030-015-0334-1Pre-print versio
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