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Critical pore radius and transport properties of disordered hard- and overlapping-sphere models

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Physical Review E 2021年第1期104卷 014127-014127页

作者： Michael A. Klatt Robert M. Ziff Salvatore Torquato Department of Physics Princeton University Princeton New Jersey 08544 USA Institut für Theoretische Physik FAU Erlangen-Nürnberg Staudtstr. 7 91058 Erlangen Germany Center for the Study of Complex Systems and Department of Chemical Engineering University of Michigan Ann Arbor Michigan 48109 USA Department of Chemistry Princeton Institute for the Science and Technology of Materials and Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

Transport properties of porous media are intimately linked to their pore-space microstructures. We quantify geometrical and topological descriptors of the pore space of certain disordered and ordered distributions of spheres, including pore-size functions and the critical pore radius δc. We focus on models of porous media derived from maximally random jammed sphere packings, overlapping spheres, equilibrium hard spheres, quantizer sphere packings, and crystalline sphere packings. For precise estimates of the percolation thresholds, we use a strict relation of the void percolation around sphere configurations to weighted bond percolation on the corresponding Voronoi networks. We use the Newman-Ziff algorithm to determine the percolation threshold using universal properties of the cluster size distribution. The critical pore radius δc is often used as the key characteristic length scale that determines the fluid permeability k. A recent study [Torquato, Adv. Wat. Resour. 140, 103565 (2020)] suggested for porous media with a well-connected pore space an alternative estimate of k based on the second moment of the pore size 〈δ2〉, which is easier to determine than δc. Here, we compare δc to the second moment of the pore size 〈δ2〉, and indeed confirm that, for all porosities and all models considered, δc2 is to a good approximation proportional to 〈δ2〉. However, unlike 〈δ2〉, the permeability estimate based on δc2 does not predict the correct ranking of k for our models. Thus, we confirm 〈δ2〉 to be a promising candidate for convenient and reliable estimates of the fluid permeability for porous media with a well-connected pore space. Moreover, we compare the fluid permeability of our models with varying degrees of order, as measured by the τ order metric. We find that (effectively) hyperuniform models tend to have lower values of k than their nonhyperuniform counterparts. Our findings could facilitate the design of porous media with desirable transport properties via targete

关键词： Geophysical networks Materials Patterns in complex systems

Bidirectional shooting method for extreme nonlinear optics

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Physical Review A 2019年第5期100卷 053818-053818页

作者： A. Hofstrand P. Jakobsen J. V. Moloney Program in Applied Mathematics University of Arizona Tucson Arizona 85721 USA College of Optical Sciences University of Arizona Tucson Arizona 85721 USA Department of Mathematics and Statistics University of Tromso 9037 Tromso Norway

In this paper we introduce a pseudospectral shooting method to model intense, ultrashort optical pulses incident on remote targets. The method naturally extends the unidirectional pulse propagation equation to include backward propagating radiation due to either nonlinear coupling with the “forward” field or reflections generated at material boundaries. The general applicability of the method is highlighted with several examples, including a full simulation of a pulse propagating through air across an ultrathin gold film coated on fused silica.

关键词： Nonlinear optics

End-To-End Quantum Machine Learning Implemented with Controlled Quantum Dynamics

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Physical Review applied 2020年第6期14卷 064020-064020页

作者： Re-Bing Wu Xi Cao Pinchen Xie Yu-xi Liu Department of Automation Tsinghua University Beijing 100084 China Beijing National Research Center for Information Science and Technology Beijing 100084 China Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA Institute of Microelectronics Tsinghua University Beijing 100084 China

To achieve quantum machine learning on imperfect noisy intermediate-scale quantum (NISQ) processors, the entire physical implementation should include as few as possible hand-designed modules with only a few ad hoc parameters to be determined. This work presents such a hardware-friendly end-to-end quantum-machine-learning scheme that can be implemented with imperfect NISQ processors. The proposal transforms the machine-learning task to the optimization of controlled quantum dynamics, in which the learning model is parameterized by experimentally tunable control variables. Our design also enables automated feature selection by encoding the raw input to quantum states through agent control variables. Comparing with the gate-based parameterized quantum circuits, the proposed end-to-end quantum-learning model is easy to implement as there are only a few ad hoc parameters to be determined. Numerical simulations on the benchmarking MNIST (Mixed National Institute of Standards and Technology) dataset of handwritten digits demonstrate that the model can achieve high performance using only 3–5 qubits without downsizing the dataset, which shows great potential for accomplishing large-scale real-world learning tasks on NISQ processors.

关键词： Machine learning Noise Quantum control Quantum information architectures & platforms Artificial neural networks

Navigating the challenges in creating complex data systems: a development philosophy

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arXiv 2022年

作者： Dittmer, Sören Roberts, Michael Gilbey, Julian Biguri, Ander Preller, Jacobus Rudd, James H.F. Aston, John A.D. Schönlieb, Carola-Bibiane Selby, Ian Breger, Anna Thorpe, Matthew Weir-McCall, Jonathan R. Gkrania-Klotsas, Effrossyni Korhonen, Anna Jefferson, Emily Langs, Georg Yang, Guang Prosch, Helmut Stanczuk, Jan Tang, Jing Babar, Judith Sánchez, Lorena Escudero Teare, Philip Patel, Mishal Wassin, Marcel Holzer, Markus Walton, Nicholas Lió, Pietro Shadbahr, Tolou Sala, Evis Department of Applied Mathematics and Theoretical Physics University of Cambridge Cambridge United Kingdom Addenbrooke’s Hospital Cambridge University Hospitals NHS Trust Cambridge United Kingdom Department of Medicine University of Cambridge Cambridge United Kingdom Department of Pure Mathematics and Mathematical Statistics University of Cambridge Cambridge United Kingdom ZeTeM University of Bremen Bremen Germany Department of Radiology University of Cambridge Cambridge United Kingdom Faculty of Mathematics University of Vienna Austria Department of Mathematics University of Manchester Manchester United Kingdom Royal Papworth Hospital Cambridge Royal Papworth Hospital NHS Foundation Trust Cambridge United Kingdom Language Technology Laboratory University of Cambridge Cambridge United Kingdom Population Health and Genomics School of Medicine University of Dundee Dundee United Kingdom Department of Biomedical Imaging and Image-guided Therapy Computational Imaging Research Lab Medical University of Vienna Vienna Austria National Heart and Lung Institute Imperial College London London United Kingdom Research Program in Systems Oncology Faculty of Medicine University of Helsinki Helsinki Finland Data Science & Artificial Intelligence AstraZeneca Cambridge United Kingdom Clinical Pharmacology & Safety Sciences AstraZeneca Cambridge United Kingdom Contextflow GmbH Vienna Austria Institute of Astronomy University of Cambridge Cambridge United Kingdom Department of Computer Science and Technology University of Cambridge Cambridge United Kingdom

In this perspective, we argue that despite the democratization of powerful tools for data science and machine learning over the last decade, developing the code for a trustworthy and effective data science system (DSS) is getting harder. Perverse incentives and a lack of widespread software engineering (SE) skills are among many root causes we identify that naturally give rise to the current systemic crisis in reproducibility of DSSs. We analyze why SE and building large complex systems is, in general, hard. Based on these insights, we identify how SE addresses those difficulties and how we can apply and generalize SE methods to construct DSSs that are fit for purpose. We advocate two key development philosophies, namely that one should incrementally grow – not biphasically plan and build – DSSs, and one should always employ two types of feedback loops during development: one which tests the code’s correctness and another that evaluates the code’s efficacy. Copyright © 2022, The Authors. All rights reserved.

关键词： Software engineering

Scanning protocol influence on relative electron Density-CT number calibrations and radiotherapy dose calculation for a Halcyon Linac

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Radiation Physics and Chemistry 2025年 236卷

作者： Thanh Tai, Duong Nhu Tuyen, Pham Duc Tuan, Hoang Hung, Hoang T.P. Kandemir, Recep Omer, Hiba Sulieman, Abdelmoneim Bradley, David Chow, James C.L. Department of Medical Physics Faculty of Medicine Nguyen Tat Thanh University 298-300A Nguyen Tat Thanh Street Ward 13 District 4 Ho Chi Minh City Viet Nam Department of Radiation Oncology University Medical Shing Mark Hospital Dong Nai 810000 Viet Nam Danang Irradiation Facility Research and Development Center for Radiation Technology VINATOM 550000 Da Nang Viet Nam Dokuz Eylül University Institute of Health Sciences Department of Medical Physics Izmir Turkey Dokuz Eylül University Vocational School of Health Services The Program of Radiotherapy Izmir Turkey Department of Radiological Sciences College of Applied Medical Sciences Imam Abdulrahman Bin Faisal University P. O. Box 1982 Dammam34212 Saudi Arabia Department of Radiological Sciences College of Applied Medical Sciences King Saud Bin Abdulaziz University for Health Sciences Al Ahsa Saudi Arabia Imaging Physics Section Research and Innovation Department King Faisal Specialist Hospital & Research Center Riyadh Saudi Arabia Applied Radiation Physics and Technologies Group Sunway University 46150 PJ Malaysia School of Mathematics and Physics University of Surrey GuildfordGU2 7XH United Kingdom Department of Radiation Oncology University of Toronto TorontoONN5T 1P5 Canada Radiation Medicine Program Princess Margaret Cancer Centre University Health Network ONM5G 1X6 Canada

Tissue Relative Electron Density (RED), typically determined via computation of CT-based Hounsfield unit (HU) values, has an accuracy which is affected by the choice of CT scanning parameters. The influence of these on the RED-CT number calibration curves is of importance, not least concerning variations in CT x-ray tube voltage and current. The purpose of this study was to examine the effect of variations in CT x-ray tube voltage and current on the calibration curves of RED - CT number conversion, with the aim of improving the accuracy of dose calculation in radiotherapy treatment planning. An electron density phantom CIRS have been conducted at 200 mAs, for tube voltages of 80, 110, and 130 kVp, corresponding images being calibrated in terms of RED-CT number conversion curves. Subsequent treatment plans have been generated, identified in terms of the applied tube voltages, the 130 kVp plan being designated the reference plan. The remaining plans have been compared to the reference plan via analysis of isodose distribution and dose. The influence of tube voltage were being found to be greatest for high-density substances such as bone in comparison to low-density materials. Conversely, the CT number of a titanium rod has been consistent, regardless of the choice of tube voltage or current. The effect of tube current variation on the calibration curves has been minor at higher tube voltages but more pronounced using lower voltages and current. The presence in the phantom of plugs of high-density materials has resulted in beam hardening artefacts, impacting on the RED values for other plugs. In achieving accurate dose calculation for radiotherapy treatment plans the work underscores the need to account for effects of CT scanning parameters on the RED-CT number conversion curves. Further emphasized is the importance of careful selection of imaging protocols in seeking to minimize beam hardening artefacts and to ensure accurate determination of RED. The study demonstrat

关键词： X ray tubes

Models for plasma kinetics during simultaneous therapeutic plasma exchange and extracorporeal membrane oxygenation

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arXiv 2020年

作者： Puelz, Charles Danial, Zach Marinaro, Jon Raval, Jay Griffith, Boyce E. Peskin, Charles S. Courant Institute of Mathematical Sciences New York University Department of Emergency Medicine University of New Mexico Department of Pathology University of New Mexico Departments of Mathematics Applied Physical Sciences and Biomedical Engineering University of North Carolina Carolina Center for Interdisciplinary Applied Mathematics University of North Carolina Computational Medicine Program University of North Carolina McAllister Heart Institute University of North Carolina

This paper focuses on the derivation and simulation of mathematical models describing new plasma fraction in blood for patients undergoing simultaneous extracorporeal membrane oxygenation and therapeutic plasma exchange. Models for plasma exchange with either veno–arterial or veno–venous extracorporeal membrane oxygenation are considered. Two classes of models are derived for each case, one in the form of an algebraic delay equation and another in the form of a system of delay differential equations. In special cases, our models reduce to single compartment ones for plasma exchange that have been validated with experimental data [15]. We also show that the algebraic delay equations are forward Euler discretizations of the delay differential equations, with timesteps equal to transit times through model compartments. Numerical simulations are performed to compare different model types, to investigate the impact of plasma device port switching on the efficiency of the exchange process, and to study the sensitivity of the models to their parameters. Copyright © 2020, The Authors. All rights reserved.

关键词： Respiratory therapy

Monitoring of Uterus Electrical Activities using Electromyography in Stage i Induction Labor 1

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Monitoring of Uterus Electrical Activities using Electromyog...

1st International Conference on Computer, Science, Engineering and Technology, ICComSET 2018

作者： Rhomadona, Shinta Wurdiana Widyawati, Melyana Nurul Suryono, S. Postgraduate Applied Science Midwifery Program Poltekkes Kemenkes Semarang Indonesia Diploma III of Midwifery Stikes William Booth-Surabaya Indonesia Department of Physics Faculty of Science and Mathematics Diponegoro University Semarang Indonesia

Labor induction is one of the main contributors of serious complication among mothers and babies. Prolonged artificial uterus muscle contraction may result in uterus hyper stimulation. One method of prevention is using the abdomen palpation technique. However, its practice has so far been less effective, less accurate, time consuming, and somehow subjective, as it requires meticulousness of the examiner. The WHO recommends that laboring mothers using induction technique should continuously be monitored. Therefore, there is a need for a much more accurate measure using a monitoring instrument that is capable of recording contraction. The instrument is electromyography. This research analyzed uterus electrical activities in stage I labor induction. The method used was observing 10 respondents undergoing labor induction for their contraction, every 15 minutes for 10 minutes each using electromyography. Monitoring results were then analyzed for frequency, duration, interval, and action potential, and these were presented as a trend. Results show a trend of frequency, duration, interval, and action potential of uterus contraction in stage I labor, with successful induction showing increasing rhythm, while failed induction indicating constant rhythm. Mean frequency, duration, interval, and action potential is 5.30 time/10 minutes, 55.89 seconds, 4.12 minutes, and 1.64 V respectively. Meanwhile, the 3 mothers with failed induction have mean frequency of 1.64x/10 minute, mean contraction duration of 21.74 seconds, and mean interval of 7.40 minutes, and mean action potential of 1.18 V. © 2019 IOP Publishing Ltd. All rights reserved.

关键词： Muscle

Global convergence of gradient descent for deep linear residual networks

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arXiv 2019年

作者： Wu, Lei Wang, Qingcan Ma, Chao Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

We analyze the global convergence of gradient descent for deep linear residual networks by proposing a new initialization: Zero-asymmetric (ZAS) initialization. It is motivated by avoiding stable manifolds of saddle points. We prove that under the ZAS initialization, for an arbitrary target matrix, gradient descent converges to an "-optimal point in O ( L3 log(1=") ) iterations, which scales polynomially with the network depth L. Our result and the exp((L)) convergence time for the standard initialization (Xavier or near-identity) [18] together demonstrate the importance of the residual structure and the initialization in the optimization for deep linear neural networks, especially when L is large. Copyright © 2019, The Authors. All rights reserved.

关键词： Gradient methods

An optimal algorithm for strict circular seriation

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arXiv 2021年

作者： Armstrong, Santiago Guzmán, Cristóbal Long, Carlos A. Sing Institute for Mathematical and Computational Engineering Pontificia Universidad Católica de Chile Santiago Chile Anid - Millennium Science Initiative Program Millennium Nucleus Center for the Discovery of Structures in Complex Data Santiago Chile Department of Applied Mathematics University of Twente Netherlands Institute for Biological and Medical Engineering Pontificia Universidad Católica de Chile Santiago Chile

We study the problem of circular seriation, where we are given a matrix of pairwise dissimilarities between n objects, and the goal is to find a circular order of the objects in a manner that is consistent with their dissimilarity. This problem is a generalization of the classical linear seriation problem where the goal is to find a linear order, and for which optimal O(n2) algorithms are known. Our contributions can be summarized as follows. First, we introduce circular Robinson matrices as the natural class of dissimilarity matrices for the circular seriation problem. Second, for the case of strict circular Robinson dissimilarity matrices we provide an optimal O(n2) algorithm for the circular seriation problem. Finally, we propose a statistical model to analyze the well-posedness of the circular seriation problem for large n. In particular, we establish O(log(n)/n) rates on the distance between any circular ordering found by solving the circular seriation problem to the underlying order of the model, in the Kendall-tau *** Codes 68R01, 05C85, 05C50, 05C25, 65C20 Copyright © 2021, The Authors. All rights reserved.

关键词： Trees (mathematics)