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  • Articles  (27)
  • Articles: DFG German National Licenses  (27)
  • Stability  (27)
  • 2010-2014
  • 1980-1984  (27)
  • 1950-1954
  • Mathematics  (27)
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  • 1
    Electronic Resource
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    Springer
    Mathematical programming 23 (1982), S. 181-192 
    ISSN: 1436-4646
    Keywords: Linear Complementarity Problem ; Stability ; Classes of Matrices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract It has been shown previously that the Linear Complementarity Problem is stable when the defining matrix is positive semidefinite and when (locally) the set of solutions is nonempty and bounded. We enlarge the class of matrices for which this is true and also demonstrate how the boundedness condition leads to other stability type questions.
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  • 2
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    Journal of mathematical biology 16 (1982), S. 49-55 
    ISSN: 1432-1416
    Keywords: Stability ; Diffusion ; Parabolic equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Models for a single species that inhabits an environment that is spatially varying are presented. Simple necessary and sufficient conditions for stability, which are independent of the exact details of the dispersal process, are developed in the case of large diffusion rates. The results highlight the important stabilizing nature of diffusion in a spatially varying environment.
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  • 3
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    Journal of mathematical biology 9 (1980), S. 65-83 
    ISSN: 1432-1416
    Keywords: Nonnegative equilibria ; Stability ; Decompositions ; Sub-communities ; Structural perturbations ; Connective stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary The major objective of this paper is to propose a new decomposition-aggregation framework for stability analysis of Lotka-Volterra equations employing the concept of vector Liapunov functions. Both the disjoint and the overlapping decompositions are introduced to increase flexibility in constructing Liapunov functions for the overall system. Our second objective is to consider the Lotka-Volterra equations under structural perturbations, and derive conditions under which a positive equilibrium is connectively stable. Both objectives of this paper are directed towards a better understanding of the intricate interplay between stability and complexity in the context of robustness of model ecosystems represented by Lotka-Volterra equations. Only stability of equilibria in models with constant parameters is considered here. Nonequilibrium analysis of models with nonlinear time-varying parameters is the subject of a companion paper.
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  • 4
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    Journal of mathematical biology 11 (1981), S. 65-84 
    ISSN: 1432-1416
    Keywords: Population dynamics ; Age-dependent models ; Equilibrium solutions ; Stability ; Evolution equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary A mathematical model describing the dynamics of a population consisting of several species is studied. The interactions in the population are assumed to be age-specific. Using an evolution equation approach, sufficient conditions for well-posedness in L 1 of the dynamics and for existence as well as for stability of equilibrium solutions are given.
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  • 5
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    Journal of mathematical biology 11 (1981), S. 95-103 
    ISSN: 1432-1416
    Keywords: Epidemiology ; SIRS ; Deterministic models ; Distributed delays ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A detailed analysis of a general class of SIRS epidemic models is given. Sufficient conditions are derived which guarantee the global stability of the endemic equilibrium solution. Further conditions are found which ensure instability for the equilibrium. Finally, the dependence of the stability on the contact number and the ratio of the mean length of infection to the mean removed time is considered.
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  • 6
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    Journal of mathematical biology 14 (1982), S. 71-75 
    ISSN: 1432-1416
    Keywords: Epidemiology ; Two host models ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract An epidemic model is derived for a two host infectious disease. It is shown that if a non-trivial equilibrium solution exists, it is globally stable. This result is also proved for a similar one host model.
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  • 7
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    Journal of mathematical biology 16 (1982), S. 33-48 
    ISSN: 1432-1416
    Keywords: Sterile insect release ; Predation ; Stability ; Limit cycles ; Optimal control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A model for the sterile insect release method of pest control in which the target species is under predatory or parasitic regulation is analyzed. The equations are nondimensionalized and the rescaled parameters are interpreted. There are four types of equilibria, whose existence and stability depend on which of ten regions of parameter space contain the rescaled parameters, and in turn give minimal release rates to achieve eradication of the pest. In at least one region, Hopf bifurcation theory shows the existence of limit cycles, but they are found to be unstable. In addition, the optimal release rate to minimize a total cost functional for pest control by the sterile release method is studied. Both approaches show that when predation accounts for a large fraction of the natural deaths, the necessary release rate and total cost are higher than for weak predation. If the predators are removed without being replaced by any other source of mortality, the cost rises in all cases but rises much more dramatically for cases with strong predation. A definite danger of the sterile release method when some predatory control exists is that the predators are frequently driven extinct before the prey, so that the target species could explode to much higher levels and be more difficult to eradicate again after the sterile release is terminated.
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  • 8
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    Journal of mathematical biology 17 (1983), S. 289-304 
    ISSN: 1432-1416
    Keywords: Endemicity ; Epidemics ; Genetics ; Deterministic models ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A discrete time genetics model is developed for populations that are undergoing selection due to infectious disease. It is assumed that the generation time of the host and infectious agent are non-synchronous and that only the host population is evolving. Two classes of epidemic processes are considered. The first class is for infectious agents that confer immunity following infection, while the second class is for those that do not confer immunity. The necessary and sufficient conditions are found in order for the disease to persist in a stable polymorphic host population. These conditions are shown to depend on the density of susceptibles, the selection coefficients, and the severity and class of the disease process.
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  • 9
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    Journal of mathematical biology 11 (1981), S. 1-14 
    ISSN: 1432-1416
    Keywords: Ecological modelling ; Predator-prey systems ; Ordinary non-linear differential equations ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We examine the qualitative effects of constant-rate stocking of either or both species in a predator-prey system. The hypotheses are made as mild as possible so that several types of systems with different qualitative alternatives may be studied.
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  • 10
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    Journal of mathematical biology 12 (1982), S. 101-114 
    ISSN: 1432-1416
    Keywords: Predator-prey systems ; Harvesting ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The global behaviour of a class of predator-prey systems, modelled by a pair of non-linear ordinary differential equations, under constant rate harvesting and/or stocking of both species, is presented. Theoretically possible structures and transitions are developed and validated by computer simulations. The results are presented as transition loci in the F-G (prey harvest rate-predator harvest rate) plane.
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  • 11
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    Journal of mathematical biology 14 (1982), S. 231-250 
    ISSN: 1432-1416
    Keywords: Predator-prey ; Age structure ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A general predator-prey model is considered in which the predator population is assumed to have an age structure which significantly affects its fecundity. The model equations are derived from the general McKendrick equations for age structured populations. The existence, stability and destabilization of equilibria are studied as they depend on the prey's natural carrying capacity and the maturation periodm of the predator. The main result of the paper is that for a broad class of maturation functions positive equilibria are either unstable for smallm or are destabilized asm decreases to zero. This is in contrast to the usual rule of thumb that increasing (not decreasing) delays in growth rate responses cause instabilities.
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  • 12
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    Journal of mathematical biology 15 (1982), S. 37-50 
    ISSN: 1432-1416
    Keywords: Reaction-diffusion system ; Stationary solution ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We consider a spatial population growth process which is described by a reaction-diffusion equation c(x)u t = (a 2(x)u x ) x +f(u), c(x) 〉0, a(x) 〉 0, defined on an interval [0, 1] of the spatial variable x. First we study the stability of nonconstant stationary solutions of this equation under Neumann boundary conditions. It is shown that any nonconstant stationary solution (if it exists) is unstable if a xx⩽0 for all xε[0, 1], and conversely ifa xx〉0 for some xε[0, 1], there exists a stable nonconstant stationary solution. Next we study the stability of stationary solutions under Dirichlet boundary conditions. We consider two types of stationary solutions, i.e., a solution u 0(x) which satisfies u 0 x≠0 for all xε[0, 1] (type I) and a solution u 0(x) which satisfies u 0x = 0 at two or more points in [0, 1] (type II). It is shown that any stationary solution of type I [type II] is stable [unstable] if a xx ⩾0 [a xx ⩽0] for all xε[0, 1]. Conversely, there exists an unstable [a stable] stationary solution of type I [type II] if a xx 〈0 [a xx 〉0] for some xε[0, 1].
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  • 13
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    Journal of mathematical biology 15 (1982), S. 239-247 
    ISSN: 1432-1416
    Keywords: Predator-prey model ; Behavioral adaptation ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The Volterra-Lotka predator-prey equations are modified so that the predator's ability to utilize the prey varies in proportion to the average number of encounters between the two species in the past. The behavior of this adaptive system is then described in terms of three parameters — the carrying capacity of the prey, the relative death rate of the predator, and the predator's memoryspan. The most stable situation is shown to occur when the carrying capacity of the prey is large, the predator's death rate is close to zero, and the predator is able to adapt quickly to changing levels of prey density.
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  • 14
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    Journal of mathematical biology 17 (1983), S. 331-349 
    ISSN: 1432-1416
    Keywords: Stability ; Delay equations ; Stretch reflexes ; Mathematical studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Human stretch reflexes (SRs) are often too weak and ineffectual to provide adequate postural regulation or rhythmic movement boosting (e.g. in ankle pushoff at the end of stance phase in fast running). Recent improvements in methods of artificially enhancing skeletomotor responses, especially in therapeutic regimens, should not be widely employed until the clonus-resisting stability properties of SRs are better understood. We formulate an idealized linear servo model of a segmentally-mediated SR system which includes the often ignored electromechanical coupling delay. For typical closed-loop (delay/gain) ratios, the model is shown to be unstable for all values of loop gain when operating as a position servo, but maximally stable when operating as a velocity servo. We claim that the velocity servo or one of its nonlinear relatives is a better model for some well studied SRs than, e.g., Houk's stiff muscle hypothesis. We also present evidence that even feeble and quickly saturating monosynaptic postural servos are always unstable if operated as pure position regulators.
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  • 15
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    Journal of mathematical biology 18 (1983), S. 93-102 
    ISSN: 1432-1416
    Keywords: Stability ; Time delay ; Feasible equilibrium ; Partially feasible equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A sufficient condition for the existence of a globally asymptotically stable equilibrium in Volterra models with continuous time delay is obtained, and some properties of the stable equilibrium are proven. Furthermore, some applications in which asymptotic stability only depends on the sign of the coefficients are considered.
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  • 16
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    Journal of mathematical biology 10 (1980), S. 33-51 
    ISSN: 1432-1416
    Keywords: Plankton ; Stability ; Perturbations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Linear perturbation theory is used to examine the stability of steady-state distributions of marine phytoplankton in the presence of a mean current with shear. Solutions are obtained for the general initial-value problem and it is found that all distributions are asymptotically stable so long as the rate of shear is greater than the local production. On the other hand, the early time behavior indicates that the system can be altered, if accomplished soon enough, depending upon a relative combination of diffusion, advection and production. Quantitative assessments are made where data are available.
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  • 17
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    Journal of mathematical biology 10 (1980), S. 65-77 
    ISSN: 1432-1416
    Keywords: Predator-prey ; Persistence ; Stability ; Differential inequalities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary The time derivatives of prey and predator populations are assumed to satisfy a set of inequalities, instead of a precise differential equation, reflecting an uncertain environmental and/or lack of knowledge by the modeler. A system of differential equations is found whose solution gives the boundary of a persistent set, which is positive flow invariant for any system satisfying the inequalities. Conditions are given for the persistent set to be bounded away from both axes, which show that resonance effects cannot drive either predator or prey to extinction if that does not happen for an autonomous system satisfying the inequalities. In general predator-prey systems are more persistent when there is strong asymptotic stability, when there is correlation between prey and predator dynamics, when the effect of perturbations is density dependent, and are more persistent under perturbations of the prey than of the predator.
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  • 18
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    Journal of mathematical biology 10 (1980), S. 97-100 
    ISSN: 1432-1416
    Keywords: Reaction diffusion equations ; Wave-trains ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary Stability of a class of solutions to reaction-diffusion equations is studied numerically. It is found that the solutions do not persist under a variety of boundary conditions.
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  • 19
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    Journal of mathematical biology 13 (1981), S. 185-198 
    ISSN: 1432-1416
    Keywords: Epidemiology ; Deterministic models ; Distributed delays ; Thresholds ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary A cyclic, constant parameter epidemiological model is described for a closed population divided into susceptible, exposed and infectious classes. Distributed delays are introduced and the model is formulated as two coupled Volterra integral equations. The delays do not change the general nature of thresholds or asymptotic stability; in all cases considered the disease either dies out, or approaches an endemic steady state.
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  • 20
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    Journal of mathematical biology 16 (1982), S. 25-31 
    ISSN: 1432-1416
    Keywords: Stability ; Community matrix ; Lotka-Volterra models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The explicit function of the community matrix of a three dimensional Lotka-Volterra model is delineated by a set of necessary and sufficient conditions for a positive equilibrium to be asymptotically stable. In the special case that the community matrix is quasi weakly diagonally dominant, it is shown that a positive determinant for the community matrix is not only necessary but is also sufficient for stability. The results are specific to three dimensional models and do not extend to communities of dimension greater than three.
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  • 21
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    Journal of mathematical biology 19 (1984), S. 147-156 
    ISSN: 1432-1416
    Keywords: Stability ; delay ; difference equations ; whale models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract This paper relates the stability properties of a class of delay-difference equations to those of an associated scalar difference equation. Simple but powerful conditions for testing global stability are presented which are independent of the length of the time delay involved. For models which do not have globally stable equilibria, estimates of stability regions are obtained. Some well known baleen whale models are used to illustrate the results.
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  • 22
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    Journal of mathematical biology 9 (1980), S. 37-47 
    ISSN: 1432-1416
    Keywords: Epidemiology ; Endemic infectious diseases ; Deterministic models ; Thresholds ; Distributed delays ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary Endemic infectious diseases for which infection confers permanent immunity are described by a system of nonlinear Volterra integral equations of convolution type. These constant-parameter models include vital dynamics (births and deaths), immunization and distributed infectious period. The models are shown to be well posed, the threshold criteria are determined and the asymptotic behavior is analysed. It is concluded that distributed delays do not change the thresholds and the asymptotic behaviors of the models.
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  • 23
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    Journal of mathematical biology 10 (1980), S. 401-415 
    ISSN: 1432-1416
    Keywords: Stability ; Volterra ecosystems ; Linear complementarity theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In this paper, global asymptotic stability of ecosystems of the generalized Volterra type $$dx_i /dt = x_i \left( {b_{i - } \mathop \sum \limits_{j = 1}^n a_{ij} x_j } \right),{\text{ }}i = 1,...,n,$$ is investigated. We obtain the conditions for the existence of a nonnegative and stable equilibrium point of the system by applying a result of linear complementarity theory. The results of this paper show that there exists a class of systems that do not have multiple domains of attractions. This class is defined in terms of the species interactions alone, and does not involve carrying capacities or species net birth rates.
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  • 24
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    Journal of mathematical biology 11 (1981), S. 207-233 
    ISSN: 1432-1416
    Keywords: Clines ; Population genetics ; Nonlinear diffusion problems ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract If a population, which consists of individuals having genetic variation at one locus, with two alleles A and a, evolves under the influence of migration and selection, gradients in the distribution of alleles may arise. We consider the effect of asymmetry in the migration and spatial dependence of the selection process, upon the emergence and stability of such gradients.
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  • 25
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    Journal of mathematical biology 16 (1982), S. 103-112 
    ISSN: 1432-1416
    Keywords: Bifurcation ; Competition ; Diffusive Lotka-Volterra system ; Predator-prey interaction ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Three examples of the diffusive 3-species Lotka-Volterra system with constant interaction parameters are given, and by bifurcation techniques shown to have stable spatially non-constant equilibrium solutions. One example is competitive; the second one predator-two-competing prey and the third involves two predators and a single prey.
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  • 26
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    Journal of mathematical biology 16 (1983), S. 199-220 
    ISSN: 1432-1416
    Keywords: Nonlinear integral operator ; Travelling wave ; Wave speed ; Asymptotic speed of propagation ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In this paper, we establish the existence and stability property of travelling wave solutions of a nonlinear integral operator in the inferior case.
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  • 27
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    Journal of mathematical biology 18 (1983), S. 213-221 
    ISSN: 1432-1416
    Keywords: Diffusive Lotka-Volterra system ; Hopf-bifurcation ; Spatiotemporal oscillation ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A stability condition for Hopf-bifurcating solutions from the uniform equilibrium of clasical Lotka-Volterra interaction-diffusion equations is presented. Using this condition, it is shown that stable spatio-temporal oscillations exist in the framework of such equations.
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