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EVOLUTION OF MATURATION SIZE IN HARVESTED PREDATOR-PREY SYSTEM

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EVOLUTION OF MATURATION SIZE IN HARVESTED PREDATOR-PREY SYST...

第三届世界生态高峰会(Eco Summit 2007)

作者： Poos J.J. Brannstrom A. Dieckmann U. Evolution and Ecology Program International Institute for Applied Systems AnalysisLaxenburg Austria Institute for Marine & Ecosystem Studies IJmuiden Netherlands Evolution and Ecology Program International Institute for Applied Systems AnalysisLaxenburg Austria Department of Mathematics and Mathematical Statistics Umea University Umea Sweden Evolution and Ecology Program International Institute for Applied Systems AnalysisLaxenburg Austria

Symbol-based multilevel block τ preconditioners for multilevel block Toeplitz systems: GLT-based analysis and applications

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arXiv 2024年

作者： Hon, Sean Y. Li, Congcong Sormani, Rosita L. Krause, Rolf Serra-Capizzano, Stefano Department of Mathematics Hong Kong Baptist University Kowloon Tong Hong Kong Department of Theoretical and Applied Sciences University of Insubria Italy Center for Computational Medicine in Cardiology University of Italian Switzerland Switzerland Department of Science and High Technology University of Insubria Italy

In recent years, there has been a renewed interest in preconditioning for multi-level Toeplitz systems, a research field that has been extensively explored over the past several decades. This work introduces novel preconditioning strategies using multilevel τ matrices for both symmetric and nonsymmetric multilevel Toeplitz systems. Our proposals constitute a general framework, as they are constructed solely based on the generating function of the multilevel Toeplitz coefficient matrix, when it can be defined. We begin with nonsymmetric systems, where we employ a symmetrization technique by permuting the coefficient matrix to produce a real symmetric multilevel Hankel structure. We propose a multi- level τ preconditioner tailored to the symmetrized system and prove that the eigenvalues of the preconditioned matrix sequence cluster at ±1, leading to rapid convergence when using the preconditioned minimal residual method. The high effectiveness of this approach is demonstrated through its application in solving space fractional diffusion equations. Next, for symmetric systems we introduce another multilevel τ preconditioner and show that the preconditioned conjugate gradient method can achieve an optimal convergence rate, namely a rate that is independent of the matrix size, when employed for a class of ill-conditioned mul- tilevel Toeplitz systems. Numerical examples are provided to critically assess the effectiveness of our proposed preconditioners compared to several leading existing preconditioned solvers, highlighting their superior *** Codes 65F08, 65F10, 65M22, 65Y05 Copyright © 2024, The Authors. All rights reserved.

关键词： Conjugate gradient method

Complexity for an open quantum system

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Physical Review D 2022年第4期105卷 046011-046011页

作者： Arpan Bhattacharyya Tanvir Hanif S. Shajidul Haque Md. Khaledur Rahman Indian Institute of Technology Gandhinagar Gujarat 382355 India Department of Theoretical Physics University of Dhaka Dhaka-1000 Bangladesh High Energy Physics Cosmology & Astrophysics Theory Group and The Laboratory for Quantum Gravity & Strings Department of Mathematics and Applied Mathematics University of Cape Town Rondebosch Cape Town 7700 South Africa National Institute for Theoretical and Computational Sciences (NITheCS) Rondebosch Cape Town 7700 South Africa

We study the complexity for an open quantum system. Our system is a harmonic oscillator coupled to a one-dimensional massless scalar field, which acts as the bath. Specifically, we consider the reduced density matrix by tracing out the bath degrees of freedom for both regular and inverted oscillators and compute the complexity of purification (COP) and complexity by using the operator-state mapping. We find that when the oscillator is regular, the COP saturates quickly for both underdamped and overdamped oscillators. Interestingly, when the oscillator is underdamped, we discover a kink-like behavior for the saturation value of the COP with a varying damping coefficient. For the inverted oscillator, we find a linear growth of the COP with time for all values of the bath-system interaction. However, when the interaction is increased the slope of the linear growth decreases, implying that the unstable nature of the system can be regulated by the bath.

关键词： computational complexity Gauge-gravity dualities Open quantum systems Quantum chaos

Hard convex lens-shaped particles: Characterization of dense disordered packings

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arXiv 2019年

作者： Cinacchi, Giorgio Torquato, Salvatore Instituto de Ciencias de Materiales "Nicolás Cabrera" Universidad Autónoma de Madrid Ciudad Universitaria de Cantoblanco MadridE-28049 Spain Department of Chemistry Department of Physics Institute for the Science and Technology of Materials Program for Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

Among the family of hard convex lens-shaped particles (lenses), the one with aspect ratio equal to 2/3 is ‘optimal’ in the sense that the maximally random jammed (MRJ) packings of such lenses achieve the highest packing fraction φMRJ ' 0.73. This value is only a few percent lower than φDKP = 0.76210 . . . , the packing fraction of the corresponding densest-known crystalline (degenerate) packings. By exploiting the appreciably reduced propensity that a system of such optimal lenses has to positionally and orientationally order, disordered packings of them are progressively generated by a Monte Carlo method-based procedure from the dilute equilibrium isotropic fluid phase to the dense nonequilibrium MRJ state. This allows one to closely monitor how the (micro)structure of these packings changes in the process of formation of the MRJ state. The gradual changes undergone by the many structural descriptors calculated can coherently and consistently be traced back to the gradual increase in contacts between the hard particles until the isostatic mean value of 10 contact neighbors per lens is reached at the effectively hyperuniform MRJ state. Compared to the MRJ state of hard spheres, the MRJ state of such optimal lenses is denser (less porous), more disordered, and rattler-free. This set of characteristics makes them good glass formers. It is possible that this conclusion may also hold for other hard convex uniaxial particles with a correspondingly similar aspect ratio, be they oblate or prolate, and that, by using suitable biaxial variants of them, that set of characteristics might further improve. Copyright © 2019, The Authors. All rights reserved.

关键词： Aspect ratio

Wasserstein Wormhole: Scalable Optimal Transport Distance with Transformers

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arXiv 2024年

作者： Haviv, Doron Kunes, Russell Zhang Dougherty, Thomas Burdziak, Cassandra Nawy, Tal Gilbert, Anna Pe’er, Dana Computational and Systems Biology Program Sloan Kettering Institute Memorial Sloan Kettering Cancer Center United States Tri-Institutional Training Program in Computational Biology and Medicine Weill Cornell Medicine United States Department of Statistics Columbia University United States Department of Mathematics and Statistics Yale University United States Howard Hughes Medical Institute United States

Optimal transport (OT) and the related Wasserstein metric (W) are powerful and ubiquitous tools for comparing distributions. However, computing pairwise Wasserstein distances rapidly becomes intractable as cohort size grows. An attractive alternative would be to find an embedding space in which pairwise Euclidean distances map to OT distances, akin to standard multidimensional scaling (MDS). We present Wasserstein Wormhole, a transformer-based autoencoder that embeds empirical distributions into a latent space wherein Euclidean distances approximate OT distances. Extending MDS theory, we show that our objective function implies a bound on the error incurred when embedding non-Euclidean distances. Empirically, distances between Wormhole embeddings closely match Wasserstein distances, enabling linear time computation of OT distances. Along with an encoder that maps distributions to embeddings, Wasserstein Wormhole includes a decoder that maps embeddings back to distributions, allowing for operations in the embedding space to generalize to OT spaces, such as Wasserstein barycenter estimation and OT interpolation. By lending scalability and interpretability to OT approaches, Wasserstein Wormhole unlocks new avenues for data analysis in the fields of computational geometry and single-cell biology. Software is available at http://***/en/latest/. © 2024, CC BY-NC-ND.

关键词： computational geometry

Spectral neighbor joining for reconstruction of latent tree models

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arXiv 2020年

作者： Jaffe, Ariel Amsel, Noah Nadler, Boaz Chang, Joseph T. Kluger, Yuval Program in Applied Mathematics Yale University New HavenCT06511 United States Department of Computer Science Weizmann Institute of Science Rehovot76100 Israel Department of Statistics Yale University New HavenCT06520 United States Interdepartmental Program in Computational Biology and Bioinformatics New HavenCT06511 Singapore Department of Pathology New HavenCT06511 United States

A key assumption in multiple scientific applications is that the distribution of observed data can be modeled by a latent tree graphical model. An important example is phylogenetics, where the tree models the evolutionary lineages of various organisms. Given a set of independent realizations of the random variables at the leaves of the tree, a common task is to infer the underlying tree topology. In this work we develop Spectral Neighbor Joining (SNJ), a novel method to recover latent tree graphical models. In contrast to distance based methods, SNJ is based on a spectral measure of similarity between all pairs of observed variables. We prove that SNJ is consistent, and derive a sufficient condition for correct tree recovery from an estimated similarity matrix. Combining this condition with a concentration of measure result on the similarity matrix, we bound the number of samples required to recover the tree with high probability. We illustrate via extensive simulations that SNJ requires fewer samples to accurately recover trees in regimes where the tree contains a large number of leaves or long edges. We provide theoretical support for this observation by analyzing the model of a perfect binary tree. Copyright © 2020, The Authors. All rights reserved.

关键词： Recovery

A stochastic generator of global monthly wind energy with tukey g-and-h autoregressive processes

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arXiv 2017年

作者： Jeong, Jaehong Yan, Yuan Castruccio, Stefano Genton, Marc G. CEMSE Division King Abdullah University of Science and Technology Thuwal23955-6900 Saudi Arabia Department of Applied and Computational Mathematics and Statistics University of Notre Dame 153 Hurley Hall Notre DameIN46556 United States

Quantifying the uncertainty of wind energy potential from climate models is a very timeconsuming task and requires a considerable amount of computational resources. A statistical model trained on a small set of runs can act as a stochastic approximation of the original climate model, and be used to assess the uncertainty considerably faster than by resorting to the original climate model for additional runs. While Gaussian models have been widely employed as means to approximate climate simulations, the Gaussianity assumption is not suitable for winds at policy-relevant time scales, i.e., sub-annual. We propose a trans-Gaussian model for monthly wind speed that relies on an autoregressive structure with Tukey g-and-h transformation, a exible new class that can separately model skewness and tail behavior. This temporal structure is integrated into a multi-step spectral framework that is able to account for global nonstationarities across land/ocean boundaries, as well as across mountain ranges. Inference can be achieved by balancing memory storage and distributed computation for a data set of 220 million points. Once fitted with as few as five runs, the statistical model can generate surrogates fast and efficiently on a simple laptop, and provide uncertainty assessments very close to those obtained from all the available climate simulations (forty) on a monthly scale. Copyright © 2017, The Authors. All rights reserved.

关键词： Stochastic systems

DCNet: Densely Connected Neural Network with Global Context for Abnormalities Prediction in Bronchoscopy Images

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DCNet: Densely Connected Neural Network with Global Context ...

IEEE International Conference on Bioinformatics and Biomedicine (BIBM)

作者： Ying Wang Yun Tie Fenghui Liu Lin Qi Ziqing Hu School of Electrical and Information Engineering Zhengzhou University Zhengzhou China The First Affiliated Hospital of Zhengzhou University Zhengzhou University Zhengzhou China Department of Applied and Computational Mathematics and Statistics University of Notre Dame Notre Dame USA

Bronchoscopy plays an important role in the examination of lower respiratory tract diseases. However, the large number of medical images produced by bronchoscopy makes it a time-consuming and labor-intensive task for doctors to analyze. Therefore, developing computer-aided diagnostic algorithms to assist doctors in lung image analysis is of great *** this paper, we propose a novel densely connected convolutional network called DCNet with local and global receptive fields for the automatic prediction of bronchoscopy images. Our experimental results on the clinical bronchoscopy image analysis dataset demonstrate that our proposed method outperforms state-of-the-art algorithms in distinguishing malignant bronchoscopy images, with an accuracy rate of 92.81%. And DCNet achieved 99.31% accuracy on the public data set called Kvasir-Capsule. This model may be a valuable tool to assist medical staff in the analysis of bronchoscopy images.

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Simulating spin dynamics with spin-dependent cross sections in heavy-ion collisions

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Physical Review C 2017年第4期96卷 044618-044618页

作者： Yin Xia Jun Xu Bao-An Li Wen-Qing Shen Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China University of Chinese Academy of Sciences Beijing 100049 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Department of Physics and Astronomy Texas A&M University-Commerce Commerce Texas 75429-3011 USA Department of Applied Physics Xi'an Jiao Tong University Xi'an 710049 China

We have incorporated the spin-dependent nucleon-nucleon cross sections into a Boltzmann-Uehling-Uhlenbeck transport model for the first time, using the spin-singlet and spin-triplet nucleon-nucleon elastic scattering cross sections extracted from the phase-shift analyses of nucleon-nucleon scatterings in free space. We found that the spin splitting of the collective flows is not affected by the spin-dependent cross sections, justifying it as a good probe of the in-medium nuclear spin-orbit interaction. With the in-medium nuclear spin-orbit mean-field potential that leads to local spin polarization, we found that the spin-averaged observables, such as elliptic flows of free nucleons and light clusters, becomes smaller with the spin-dependent differential nucleon-nucleon scattering cross sections.

关键词： Low & intermediate energy heavy-ion reactions Nuclear spin & parity Nucleon-nucleon interactions Polarization phenomena Hydrodynamic models