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PERSPEKTIF SEKURITI DI SAMUDERA INDONESIA
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| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Analisa |
| Volume / Edisi | : | V-6, JUNI (No. 6) |
| Halaman | : | 15-32 |
| Abstrak | : | - |
PERANAN UNCTAD DAN OPEC: KERJASAMA ATAU KONFRONTASI?
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Analisa |
| Volume / Edisi | : | V-6, JUNI (No. 6) |
| Halaman | : | 1-14 |
| Abstrak | : | Abstrak tidak tersedia. |
Random Walks of Swarming on Monotonic Resource Distribution in a Landscape
| Pengarang | : | Zhenfeng Shi, Daqing Jiang, Hao Wang |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 85 (No. 3) |
| Halaman | : | 1287-1313 |
| Abstrak | : | This study introduces a novel resource-consumer model that uniquely integrates stochastic consumer movement with spatially monotonic resource distributions, advancing our understanding of consumer dynamics in heterogeneous environments. In this framework, swarming consumer movement within a home range is modeled using the Ornstein–Uhlenbeck process, realistically capturing random walks within home range. By accounting for resource heterogeneity, the model enables consumers to access variable resource levels based on location, offering a fresh approach to simulating consumer-resource interactions in spatially structured landscapes. Key contributions include the derivation of the consumption threshold that determines the asymptotic behavior of the consumer population, distinguishing scenarios of persistence, and extinction. In addition, a novel control function is constructed to rigorously establish the existence and uniqueness of the invariant density. |
Analysis of a Model for Polymorphism in Gravity-Driven, Antisolvent Crystallization
| Pengarang | : | Milton Assunção, Kevin M. Moroney, Doireann O’Kiely, Michael Vynnycky |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 85 (No. 3) |
| Halaman | : | 1261-1286 |
| Abstrak | : | In this paper, we develop a population-balance approach to model the effect of gravity on polymorphism in antisolvent crystallization. In particular, the model accounts for nucleation, growth, supersaturation, and antisolvent fraction. Mathematically, the model consists of two first-order nonlinear hyperbolic equations for the number densities of the two polymorphs and an ordinary differential equation for the solute concentration in the solvent. Employing the simplest possible descriptions for nucleation and growth, we find a degeneracy in the model equations. Overcoming this via a variable transformation leads to a formulation in which there are three shocks; the locations of two of them are unknown functions of time. The solutions to the resulting equations are considered qualitatively from the point of view of the method of characteristics and are also obtained numerically. The model is then applied to the crystallization of L-histidine, an essential amino acid that is used in the food and pharmaceutical industries, as a test molecule. |
Inverse Random Potential Scattering for the Polyharmonic Wave Equation Using Far-Field Patterns
| Pengarang | : | Jianliang Li, Peijun Li, Xu Wang, Guanlin Yang |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 85 (No. 3) |
| Halaman | : | 1237-1260 |
| Abstrak | : | This paper addresses the inverse scattering problem of a random potential associated with the polyharmonic wave equation in two and three dimensions. The random potential is represented as a centered complex-valued generalized microlocally isotropic Gaussian random field, where its covariance and relation operators are characterized as conventional pseudodifferential operators. Regarding the direct scattering problem, the well-posedness is established in the distributional sense for sufficiently large wavenumbers through analysis of the corresponding Lippmann–Schwinger integral equation. Furthermore, in the context of the inverse scattering problem, the uniqueness is attained in recovering the microlocal strengths of both the covariance and relation operators of the random potential. Notably, this is accomplished with only a single realization of the backscattering far-field patterns averaged over the high-frequency band. |
Asymmetric Deformations of a Perturbed Spherical Bubble in an Incompressible Fluid
| Pengarang | : | Chen-Chih Lai, Michael I. Weinstein |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 85 (No. 3) |
| Halaman | : | 1212-1236 |
| Abstrak | : | We study the dynamics of a gas bubble in a fluid with surface tension, starting near a spherical equilibrium. While there are many studies and applications of radial bubble dynamics, the theory of general deformations from a spherical equilibrium is less developed. We aim to understand how asymmetrically perturbed equilibrium bubbles evolve toward spherical equilibrium due to thermal or viscous dissipation in an incompressible liquid. We focus on the isobaric approximation [22], under which the gas pressure within the bubble is spatially uniform and obeys the ideal gas law. The liquid outside the bubble is incompressible, irrotational, and has surface tension. We prove that any equilibrium gas bubble must be spherical by showing that the bubble boundary is a closed surface of constant mean curvature. We then study the initial value problem (IVP) for the coupled PDEs, constitutive laws, and interface conditions of the isobaric approximation for general (asymmetric) small initial perturbations of the spherical bubble in the linearized approximation. Our first result, considering thermal damping without viscosity, proves that the linearized IVP is globally well-posed. The monopole (radial) component of the perturbation decays exponentially over time, while the multipole (nonradial) components undergo undamped oscillations. This indicates a limitation of the isobaric model for nonspherical dynamics. Our second result, incorporating viscous dissipation, shows that the IVP is linear and nonlinearly ill-posed due to an incompatibility of normal stress boundary conditions for nonspherical solutions and the irrotationality assumption. Our study concludes that to accurately capture the dynamics of general deformations of a gas bubble, the model must account for either vorticity generated at the bubble-fluid boundary, spatial nonuniformities in the gas pressure, or both. |
Global Competitive Dynamics of Aedes aegypti and Aedes albopictus with Favorable-unfavorable Seasonal Shifts
| Pengarang | : | Bo Zheng, Lijie Chang, Hongpeng Guo, Jianshe Yu |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 85 (No. 3) |
| Halaman | : | 1189-1211 |
| Abstrak | : | Of concern is the global competitive dynamics of Aedes aegypti and Aedes albopictus. We develop a planar time-switched model that considers favorable-unfavorable seasonal shifts, the interspecific mating competition in the favorable season, and the overwintering capacity in the unfavorable season. During the favorable season, we find a sharp estimation of a separatrix that determines the fate of Aedes aegypti and Aedes albopictus. When the two species undergo seasonal transition, the separatrix disappears and the time switching results in the discontinuity of the vector field, which causes complex dynamical behaviors. By analyzing the associated Poincaré map, we obtain sufficient and/or necessary conditions for the existence and stability of periodic solutions. The results show that asymmetric mating interference and wintering ability in suitable seasons were important factors affecting the interaction dynamics of Aedes aegypti and Aedes albopictus. By understanding and potentially manipulating these interactions, it might be possible to effectively reduce the size of unwanted species. |
Anisotropic Extended Burgers Model, Its Relaxation Tensor, and Properties of the Associated Boltzmann Viscoelastic System
| Pengarang | : | Maarten V. de Hoop, Masato Kimura, Ching-Lung Lin, Gen Nakamura, Kazumi Tanuma |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 85 (No. 3) |
| Halaman | : | 1172-1188 |
| Abstrak | : | We provide a new method for constructing the anisotropic relaxation tensor and proving its exponential decay property for the extended Burgers model (EBM). The EBM is an important viscoelasticity model in rheology, and used in Earth and planetary sciences. Upon having this tensor, the EBM can be converted to a Boltzmann-type viscoelastic system (BVS) of equations. Historically, the relaxation tensor for the EBM is derived by solving the constitutive equation using the Laplace transform. (We refer to this approach by the L-method.) Since inverting the inverse Laplace transform needs a partial fractions expansion, the L-method needs to assume that the EBM elasticity tensors satisfy a commutivity condition. The new method not only avoids this condition but also enables obtaining several important properties of the relaxation tensor, including its positivity, smoothness with respect to the time variable, its exponential decay property together with its derivative, and its causality. Furthermore, by connecting a spring unit parallel to EBM, we show that the BVS converted from this modified EBM has the exponential decay property. That is, any solution for its initial boundary value problem with homogeneous boundary data and source decays exponentially as time tends to infinity. |
Generating Customized Field Concentration via Virtual Surface Transmission Resonance
| Pengarang | : | Yueguang Hu, Hongyu Liu, Xianchao Wang, Deyue Zhang |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 85 (No. 3) |
| Halaman | : | 1143-1171 |
| Abstrak | : | In this paper, we develop a mathematical framework for generating strong customized field concentration locally around the inhomogeneous medium inclusion via surface transmission resonance. The purpose of this paper is two-fold. First, we show that for a given inclusion embedded in an otherwise uniformly homogeneous background space, we can design an incident field to generate strong localized field concentration at any specified places around the inclusion. The aforementioned customized field concentration is crucially reliant on the peculiar spectral and geometric patterns of certain transmission eigenfunctions. Second, we prove the existence of a sequence of transmission eigenfunctions for a specific wavenumber, and they exhibit distinct surface resonant behaviors, accompanying strong surface-localization and surface-oscillation properties. These eigenfunctions as the surface transmission resonant modes fulfill the requirement for generating the field concentration. |
Stochastic Gene Expression Model of Nuclear-to-Cell Ratio Homeostasis
| Pengarang | : | Xuesong Bai, Thomas G. Fai |
| Nama Majalah/Jurnal | : | Siam Journal On Applied Mathematics |
| Volume / Edisi | : | 85 (No. 3) |
| Halaman | : | 1121-1142 |
| Abstrak | : | Cell size varies between different cell types, and between different growth and osmotic conditions. However, the nuclear-to-cell volume ratio (N/C ratio) remains nearly constant. In this paper, we build on existing deterministic models of N/C ratio homeostasis and develop a simplified protein translation model to study the effect of stochasticity on the N/C ratio homeostasis. We solve the corresponding chemical master equation and obtain the mean and variance of the N/C ratio. We also use a Taylor expansion approximation to study the effects of the system size on the fluctuations of the N/C ratio. We then combine the translation model with a cell division model to study the effects of extrinsic noises from cell division on the N/C ratio. Our model demonstrates that the N/C ratio homeostasis is maintained when the stochasticity in cell growth is taken into account, that the N/C ratio is largely determined by the gene fraction of nuclear proteins, and that the fluctuations in the N/C ratio diminish as the system size increases. |