OPAC - Pencarian Artikel Jurnal & Majalah Library USD
Menampilkan semua artikel (Halaman 220 dari 34169, Total: 341690 data)
On Traveling Front of Ignition in Co-Flow Laminar Reactive Jets
klik untuk membaca file PDF
| Pengarang | : | Peter V. Gordon |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 1) |
| Halaman | : | 47-59 |
| Abstrak | : | In this paper we derive a simple, still experimentally feasible, model for propagation of traveling fronts of ignition which were recently observed in experimental studies of autoignition of co-flow reactive jets at high pressure. We obtain a closed form analytical solution for this model and present a detailed analysis of this solution. We also present a qualitative comparison of the model predictions with available experimental data. |
Inverse Time-Harmonic Electromagnetic Scattering from Coated Polyhedral Scatterers With a Single Far-Field Pattern
| Pengarang | : | Guang-Hui Hu |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 1) |
| Halaman | : | 25-46 |
| Abstrak | : | It is proved that a convex polyhedral scatterer of impedance type can be uniquely determined by the electric far-field pattern of a nonvanishing incident field. The incoming wave is allowed to be an electromagnetic plane wave, a vector Herglotz wave function, or a point source wave incited by some magnetic dipole. Our proof relies on the reflection principle for Maxwell's equations with the impedance (or Leontovich) boundary condition enforcing on a hyperplane. We prove that it is impossible to analytically extend the total field across any vertex of the scatterer. This leads to a data-driven inversion scheme for imaging an arbitrary convex polyhedron. |
The Effects of Fast Inactivation on Conditional First Passage Times of Mortal Diffusive Searchers
| Pengarang | : | Sean D. Lawley |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 1) |
| Halaman | : | 1-24 |
| Abstrak | : | The first time a searcher finds a target is called a first passage time (FPT). In many physical, chemical, and biological processes, the searcher is “mortal,” which means that the searcher might become inactivated (degrade, die, etc.) before finding the target. In the context of intracellular signaling, an important recent work discovered that fast inactivation can drastically alter the conditional FPT distribution of a mortal diffusive searcher, if the searcher is conditioned to find the target before inactivation. In this paper, we prove a general theorem that yields an explicit formula for all the moments of such conditional FPTs in the fast inactivation limit. This formula is quite universal, as it holds under very general conditions on the diffusive searcher dynamics, the target, and the spatial domain. These results prove in significant generality that if inactivation is fast, then the conditional FPT compared to the FPT without inactivation is (i) much faster, (ii) much less affected by spatial heterogeneity, and (iii) much less variable. Our results agree with recent computational and theoretical analysis of a certain discrete intracellular diffusion model and confirm a conjecture related to the effect of spatial heterogeneity on intracellular signaling. |
An Inverse Parameter Problem with Generalized Impedance Boundary Condition for Two-Dimensional Linear Viscoelasticity
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 4) |
| Halaman | : | 1668-1690 |
| Abstrak | : | We analyze an inverse boundary value problem in two-dimensional viscoelastic media with a generalized impedance boundary condition on the inclusion via boundary integral equation methods. The model problem is derived from a recent asymptotic analysis of a thin elastic coating as the thickness tends to zero [F. Caubet, D. Kateb, and F. Le Loue?r, J. Elasticity, 136 (2019), pp. 17--53]. The boundary condition involves a new second order surface symmetric operator with mixed regularity properties on tangential and normal components. The well-posedness of the direct problem is established for a wide range of constant viscoelastic parameters and impedance functions. Extending previous research in the Helmholtz case, the unique identification of the impedance parameters from measured data produced by the scattering of three independent incident plane waves is established. The theoretical results are illustrated by numerical experiments generated by an inverse algorithm that simultaneously recovers the impedance parameters and the density solution to the equivalent boundary integral equation reformulation of the direct problem. |
Modified Poisson--Nernst--Planck Model with Coulomb and Hard-sphere Correlations
| Pengarang | : | Manman Mai |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 4) |
| Halaman | : | 1645-1667 |
| Abstrak | : | We develop a modified Poisson--Nernst--Planck model which includes both the long-range Coulomb and short-range hard-sphere correlations in its free energy functional such that the model can accurately describe the ion transport in complex environment and under a nanoscale confinement. The Coulomb correlation including the dielectric polarization is treated by solving a generalized Debye--Hu?ckel equation which is a Green's function equation with the correlation energy of a test ion described by the self Green's function. The hard-sphere correlation is modeled through the modified fundamental measure theory. The resulting model is available for problems beyond the mean-field theory such as problems with variable dielectric media, multivalent ions, and strong surface charge density. We solve the generalized Debye--Hu?ckel equation by the Wentzel--Kramers--Brillouin approximation, and study the electrolytes between two parallel dielectric surfaces. In comparison to other modified models, the new model is shown to be more accurate in agreement with particle-based simulations and capturing the physical properties of ionic structures near interfaces. |
Autocatalytic Networks: An Intimate Relation between Network Topology and Dynamics
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 4) |
| Halaman | : | 1623-1644 |
| Abstrak | : | We study a family of networks of autocatalytic reactions, which we call hyperchains, that are a generalization of hypercycles. Hyperchains and the associated dynamical system called replicator equations are a possible mechanism for macromolecular evolution and proposed to play a role in abiogenesis, the origin of life from prebiotic chemistry. The same dynamical system also occurs in evolutionary game dynamics, in genetic selection, and as Lotka--Volterra equations of ecology. An arrow in a hyperchain encapsulates the enzymatic influence of one species on the autocatalytic replication of another. We show that the network topology of a hyperchain, which captures all such enzymatic influences, is intimately related to the dynamical properties of the mass action system it generates. Dynamical properties such as existence, uniqueness, and stability of a positive equilibrium, as well as permanence, are determined by graph-theoretic properties such as existence of a spanning linear subgraph, being unrooted, being cyclic, and Hamiltonicity |
Persistence and Spread of Solutions in a Two-Species Lotka--Volterra Competition-Diffusion Model with a Shifting Habitat
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 4) |
| Halaman | : | 1600-1622 |
| Abstrak | : | We consider a two-species Lotka--Volterra competition-diffusion model with a shifting habitat. The growth rate of each species is nondecreasing along the ????-axis, and it changes sign and shifts rightward at a speed ????. We investigate the population dynamics of the model in the habitat suitable for growth of both species for two cases: (i) one species is competitively stronger and has a slower spreading speed, and (ii) both species coexist. We obtain conditions under which the outcome of competition depends critically on a number –?????(∞) given by the model parameters. We show that under appropriate conditions, if –?????(∞) >????, then the species with the faster spreading speed spreads into the open space at its own speed and the species with the slower spreading speed spreads into its rival at speed –?????(∞), and if –?????(∞) <????, then the species with the slower spreading speed eventually dies out in space. Our results particularly demonstrate the possibility that a competitively weaker species with a faster spreading speed can drive a competitively stronger species with a slower spreading speed to extinction. The mathematical proofs involve linear determinacy analysis, integral equations, and comparison. |
Recruitment Dynamics of Social Insect Colonies
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 4) |
| Halaman | : | 1579-1599 |
| Abstrak | : | Recruitment plays a vital role in the ecological and evolutionary successes of social insect colonies. In this paper, we formulate a four-compartment model and its simplified version to explore how we should model the recruitment dynamics of workers in social insect colonies properly. Our four-compartment model has the components of the unalarmed patrollers, the alarmed patrollers, the alarmed recruiters, and the available workers, while its simplified version has three components where we combine the unalarmed patrollers and the alarmed patrollers into the patrollers. We perform complete mathematical and bifurcation analyses on both the full system and its simplified system. We have many interesting findings, including that (i) the simplified three-compartment system has only simple equilibrium dynamics, i.e., no periodic and chaotic dynamics; (ii) the four-compartment system has very complex dynamics; for example, it can have up to three subcritical Hopf bifurcations, two supercritical Hopf bifurcations, two limit point bifurcations, and a fold bifurcation of the limit cycle. Those important results provide theoretical guidance for modeling and studying recruitment dynamics of social insect colonies: It is critical to have proper compartments for biological systems as the number of compartments could lead to totally different dynamics, and hence affect policy-making. |
On the Darwin--Howie--Whelan Equations for the Scattering of Fast Electrons Described by the Schro?dinger Equation
| Pengarang | : | Thomas Koprucki |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 4) |
| Halaman | : | 1552-1578 |
| Abstrak | : | The Darwin--Howie--Whelan equations are commonly used to describe and simulate the scattering of fast electrons in transmission electron microscopy. They are a system of infinitely many envelope functions, derived from the Schro?dinger equation. However, for the simulation of images only a finite set of envelope functions is used, leading to a system of ordinary differential equations in thickness direction of the specimen. We study the mathematical structure of this system and provide error estimates to evaluate the accuracy of special approximations, like the two-beam and the systematic-row approximation. |
Erratum: Monotonicity in Inverse Medium Scattering on Unbounded Domains
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 81 (No. 3) |
| Halaman | : | 1332-1337 |
| Abstrak | : | We correct a mistake in the proof of Theorem 5.3 in [R. Griesmaier and B. Harrach, SIAM J. Appl. Math., 78 (2018), pp. 2533--2557]. |