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Automated Detection and Depth Determination of Melt Ponds on Sea Ice in ICESat-2 ATLAS Data-The Density-Dimension algorithm for Bifurcating Sea-Ice Reflectors (DDA-Bifurcate-Seaice)

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2023年 61卷 1页

作者： Herzfeld, Ute Christina Trantow, Thomas M. Han, Huilin Buckley, Ellen Farrell, Sinead Louise Lawson, Matthew Univ Colorado Boulder Dept Elect Comp & Energy Engn Geomathemat Remote Sensing & Cryospher Sci Lab Boulder CO 80309 USA Brown Univ Ctr Fluid Mech Providence RI 02912 USA Univ Maryland Dept Geog Sci College Pk 20742 MD USA Univ Maryland Dept Atmospher & Ocean Sci College Pk MD 20742 USA

As climate warms and the transition from a perennial to a seasonal Arctic sea-ice cover is imminent, understanding melt ponding is central to understanding changes in the new Arctic. National Aeronautics and Space Administration (NASA)'s Ice, Cloud and land Elevation Satellite (ICESat-2) has the capacity to provide measurements and monitoring of the onset of melt in the Arctic and on melt progression. Yet ponds are currently not identified on the ICESat-2 standard sea-ice products, in which only a single surface is determined. The objective of this article is to introduce a mathematical algorithm that facilitates automated detection of melt ponds in the ICESat-2 Advanced Topographic Laser Altimeter System (ATLAS) data, retrieval of two surface heights, pond surface and bottom, and measurements of depth and width of melt ponds. With ATLAS, ICESat-2 carries the first spaceborne multibeam micropulse photon-counting laser altimeter system, operating at 532-nm frequency. ATLAS data are recorded as clouds of discrete photon points. The Density-Dimension algorithm for bifurcating sea-ice reflectors (DDA-bifurcate-seaice) is an autoadaptive algorithm that solves the problem of pond detection near the 0.7-m nominal along-track spacing of ATLAS data, utilizing the radial basis function for calculation of a density field and a threshold function that automatically adapts to changes in the background, apparent surface reflectance, and some instrument effects. The DDA-bifurcate-seaice is applied to large ICESat-2 datasets from the 2019 and 2020 melt seasons in the multiyear Arctic sea-ice region. Results are evaluated by comparison with those from a manually forced algorithm.

关键词： Sea ice Sea surface Photonics Arctic Laser beams Surface topography Ice Arctic sea ice computational algorithm cryospheric sciences Cloud and land Elevation Satellite (ICESat-2) melt pond satellite altimetry

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Investigation on cumulative displacement of tension-only metallic yielding dissipators

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ENGINEERING STRUCTURES 2023年第1期285卷

作者： Gu, Zi Lu, Wensheng Gao, Yuqing Tongji Univ Coll Civil Engn Shanghai Peoples R China Univ Calif Berkeley Dept Civil & Environm Engn Berkeley CA 94720 USA

This paper investigates a cumulative displacement issue on the tension-only metallic yielding dissipators (TMYDs). Two potential risks caused by cumulative displacement are pointed out, namely (1) the intruded length issue, which could result in the dissipator's failure to degrade to an ordinary tension-only brace, and (2) the dissipative member strain issue, which could lead to the dissipator fracture. Theoretical models of the TMYDs, and computational algorithms of intruded length and dissipative member strain are proposed considering cu-mulative displacement in three types of TMYD, i.e., asymmetrical elastic-plastic dissipator (AEPD), hook-no-damage dissipator (HNDD), and self-centering dissipator (SCD). Accordingly, three finite element models are built up for nonlinear time history analysis, where intruded length and dissipative member strain are computed. From the results, cumulative displacement is proved to be important in designing the dissipators, and TMYDs may have the potential risk of failing while the structure is under earthquakes, exposing the structure to un-predictable danger.

关键词： Tension-only brace Yielding dissipator Cumulative displacement computational algorithm Vibration control

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Efficient spherical surface integration of Gauss functions in three-dimensional spherical coordinates and the solution for the modified Bessel function of the first kind

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JOURNAL OF MATHEMATICAL CHEMISTRY 2021年第2期59卷 505-515页

作者： Wang, Yiting Kong, Jing Middle Tennessee State Univ Ctr Computat Sci 1301 E Main St Murfreesboro TN 37132 USA Middle Tennessee State Univ Dept Chem 1301 E Main St Murfreesboro TN 37132 USA

An efficient solution of calculating the spherical surface integral of a Gauss function defined as h(s, Q) = integral(2 pi)(0) integral(pi)(0) (s + Q)(x)(i) (s + Q)(y)(i) (s + Q)(z)(k) e(-gamma(s+Q)2) sin theta d theta d phi is provided, where gamma >= 0, and i, j, k are nonnegative integers. A computationally concise algorithm is proposed for obtaining the expansion coefficients of polynomial terms when the coordinate system is transformed from cartesian to spherical. The resulting expression for h(s, Q) includes a number of cases of elementary integrals, the most difficult of which is II(n, mu) = integral(pi)(0) cos(n) theta(-cos theta)(e)d theta, with a nonnegative integer n and positive mu. This integral can be formed by linearly combining modified Bessel functions of the first kind B(n, mu) = 1/pi integral(pi)(0) e(mu cos theta) cos (n theta)d theta, with a nonnegative integer n and negative mu. Direct applications of the standard approach using Mathematica and GSL are found to be inefficient and limited in the range of the parameters for the Bessel function. We propose an asymptotic function for this expression for n = 0,1,2. The relative error of asymptotic function is in the order of 10(-16) with the first five terms of the asymptotic expansion. At last, we give a new asymptotic function of B(n, mu) based on the expression for e(-mu) II(n, mu) when n is an integer and mu is real and large in absolute value.

关键词： Bessel function Gauss function Recursive relation computational algorithm

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Modeling Sediment Resuspension and Transport Processes Induced by Propeller Wash from Ship Traffic

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JOURNAL OF HYDRAULIC ENGINEERING 2023年第5期149卷

作者： Craig, Paul M. M. Jung, Jeffrey Y. Y. Mausolff, Zander Bastidas, Luis A. A. Mathis, Thomas Wang, Pei-Fang DSI LLC 110 W Dayton St 202 Edmonds WA 98020 USA Naval Informat Warfare Ctr Pacific 53560 Hull St San Diego CA 92152 USA

Resuspension and redistribution of sediments induced by propeller wash may significantly influence aquatic ecosystems at contaminated sediment sites. This study describes a numerical modeling method developed to predict the sediment resuspension and subsequent transport processes resulting from ship traffic, with a fully coupled simulation of hydrodynamics, sediment transport, and propeller wash. By including propeller momentum effects in the flow field computation, the advection and dispersion of resuspended sediments are better represented than in previously available methods. To achieve this improvement, a computational algorithm was first developed to calculate the propeller wash effects from one or more ships (e.g., erosion rate and momentum flux);these results were then dynamically linked to a hydrodynamic and sediment transport computation using Environmental Fluid Dynamics Code Plus (EFDC+). This modeling framework was evaluated using a field experiment conducted by the US Navy. The model was calibrated with flow velocities and sediment erosion depths, and then validated with resuspended sediment concentrations in the water column. The model results reproduced the horizontal and vertical distributions of resuspended sediments better when the propeller-induced momentum was incorporated into the flow field computation. The sensitivity test indicated that the increased flow energy from propeller momentum resulted in significant dispersion of resuspended sediments in both longitudinal and lateral directions. The maximum scour was dependent on the propeller revolution speed, the ship engine power, and the distance between the propellers and the sediment bed.

关键词： Propeller wash Sediment resuspension computational algorithm Hydrodynamic and sediment transport simulation Environmental fluid dynamics code plus (EFDC plus )

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Surface characterization of bio-fillers from typical mollusk shell using computational algorithms

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INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES 2018年 84卷 48-53页

作者： Yao, Zhitong Wu, Daidai Heng, Jerry Y. Y. Zhao, Hongting Wu, Weihong Tang, Junhong Hangzhou Dianzi Univ Coll Mat Sci & Environm Engn Hangzhou 310018 Zhejiang Peoples R China Chinese Acad Sci Guangzhou Inst Energy Convers Guangzhou 510640 Guangdong Peoples R China Tsinghua Univ Minist Educ China Key Lab Solid Waste Management & Environm Safety Beijing 100084 Peoples R China Imperial Coll London Dept Chem Engn South Kensington Campus London SW7 2AZ England

The generation of surface free energy parameters calculated from contact angle data is a burdensome and time-consuming process. To facilitate these calculations, computational algorithms using three different programming languages-MATLAB, C and Python-were developed and validated by surface properties determination of PO and CPO. The results indicated that the surface free energy parameters calculated using the three algorithms were consistent. The unknowns were obtained directly from within the C and Python programs, however, indirectly from within MATLAB function. In addition, the assembly statements of the C function were longer than those of the other two. The obtained results were also compared with those from an IGC analysis. It showed that the gamma(D)(S) values determined using the contact angle methods were consistent, although lower than those obtained by IGC analysis. Compared to gamma(D)(S) , the gamma(SP)(S) component contributed less to gamma(T)(S).The lower gamma(D)(S) and gamma(SP)(S) values for CPO which added up to a lower gamma(T)(S) value, could reduce filler particle/particle interactions, allowing a better dispersion in a polymer matrix.

关键词： computational algorithm Programming language Surface characterization Pearl oyster shell Bio-filler

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Discrete heat transfer model with space-time nonlocality

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INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2022年第0期138卷

作者： Eremin, A. V. Kishov, E. A. Popov, A. I. Samara State Tech Univ Dept Ind Heat Power Engn Molodogvardeyskaya StBldg 244 Samara 443100 Russia Samara Natl Res Univ 34 Moskovskoye Shosse Samara 443086 Russia

The study of processes occurring under locally non-equilibrium conditions is of great interest due to the intensive development of laser technologies and the emerging opportunity to carry out technological operations under extreme conditions (at ultrahigh temperatures, pressures and their gradients). This paper presents the results of the development for a discrete mathematical model of thermal conductivity that takes into account the inertia of the heat transfer process in solids. A computational algorithm using the APDL language has been developed on the basis of the finite element method. APDL (ANSYS Parametric Design Language) is a scripting language that you can use to automate common tasks or even create your own model expressed in terms of parameters (variables). Developed algorithm allows one to automatically calculate temperature fields in solids of arbitrary geometric shape taking into account the heat transfer inertia. The APDL algorithm is adapted for the ANSYS software product which makes it available to a wide range of users. Verification of the algorithm developed is performed by comparing the obtained numerical results with the exact analytical solution of the model task.

关键词： Relaxation properties Thermal inertia Discrete model Finite element method Numerical solution computational algorithm ANSYS Parametric Design Language

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Asymptotic stability of quasi-periodic orbits

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PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 2022年第2259期478卷 20210787-20210787页

作者： Breunung, Thomas Swiss Fed Inst Technol Inst Mech Syst Leonardstr 21 CH-8092 Zurich Switzerland

Stability is one of the most fundamental properties of solutions to differential equations and, for example, can explain the presence of harmful vibrations. While the stability type of fixed points and periodic orbits can be assessed with standard tools, no general and reliable method allows to conclude about the stability of quasi-periodic orbits. Here, we overcome this limitation and develop a novel and universal method to rigorously assess the asymptotic stability of quasi-periodic solutions to differential equations. Furthermore, we develop an automated algorithm for such stability investigations and demonstrate its applicability on two explicit mechanical examples.

关键词： vibrations nonlinear oscillations stability quasi-periodic oscillations computational algorithm linear time-varying systems

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The hydra string method: a novel means to explore potential energy surfaces and its application to granular materials

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GRANULAR MATTER 2022年第1期24卷 24-24页

作者： Moakler, Christopher Newhall, Katherine A. Univ N Carolina Dept Phys & Astron Chapel Hill NC 27515 USA Univ N Carolina Dept Math Chapel Hill NC 27515 USA

We present a novel means to understand granular materials, the Hydra String Method (HSM). This is an efficient and autonomous way to trawl an arbitrary potential energy surface (or any similarly high dimensional function) that enumerates the saddle points, minima, and minimum energy paths between them. In doing so, it creates a reduced dimensional network representation of this surface. We also present a series of tests to choose optimized parameters for the application of the HSM. We apply this to the potential energy function of a granular system consisting of a configuration of bi-disperse, frictionless, soft spheres. Future work will make use of the found ensemble of transition pathways to statistically predict the dynamics of a system of grains.

关键词： Transition path Frictionless soft spheres Stable packings computational algorithm Energy landscape

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Optimal design of vascular stents using a network of 1D slender curved rods

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2022年 394卷 1页

作者： Canic, Suncica Grubisic, Luka Lacmanovic, Domagoj Ljulj, Matko Tambaca, Josip Univ Calif Berkeley Dept Math Berkeley CA 94720 USA Univ Zagreb Dept Math Zagreb Croatia

In this manuscript we present a mathematical theory and a computational algorithm to study optimal design of mesh-like structures such as metallic stents by changing the stent strut thickness and width to optimize the overall stent compliance. The mathematical constrained optimization problem is to minimize the "compliance functional" over a closed and bounded set of constraints. The compliance functional is the stent's overall elastic energy. The constraints are the minimal and maximal strut thickness, and a given fixed volume of the stent material. We prove the existence of a minimizer, thereby proving that the constrained optimization problem has a solution. A numerical scheme based on an iteration procedure is introduced, and implemented within a Finite Element Method framework. Optimal design of three different stent prototypes is considered: (1) a single zig-zag ring, which can be found in many complex stent designs on the US market as a basic cell in the modular stent design, (2) a Palmaz-Schatz type stent consisting of 6 zig-zag rings, and (3) a Cypher(TM) type stent consisting of zig-zag rings with sinusoidal connectors. Several interesting optimization solutions are found, some of which have already been implemented in the design of the currently available stents on the US market. The resulting computational algorithm is compared to a Genetic algorithm, and it is shown that our computational approach outperforms the Genetic algorithm in the following three key aspects: (1) computation time, (2) accuracy, and (3) maintaining the symmetry of the solution. (C) 2022 The Author(s). Published by Elsevier B.V.

关键词： Optimal stent design Vascular stents computational algorithm Cypher stent

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Reconstructing gene regulatory networks in single-cell transcriptomic data analysis

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Zoological Research 2020年第6期41卷 599-604页

作者： Hao Dai Qi-Qi Jin Lin Li Luo-Nan Chen Key Laboratory of Systems Biology Shanghai Institute of Biochemistry and Cell BiologyCenter for Excellence in Molecular Cell ScienceChinese Academy of SciencesShanghai 200031China Institute of Brain-Intelligence Technology Zhangjiang LaboratoryShanghai 201210China University of Chinese Academy of Sciences Beijing 100049China School of Life Science and Technology ShanghaiTech UniversityShanghai 201210China Key Laboratory of Systems Biology Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesChinese Academy of SciencesHangzhouZhejiang 310024China Center for Excellence in Animal Evolution and Genetics Chinese Academy of SciencesKunmingYunnan 650223China

Gene regulatory networks play pivotal roles in our understanding of biological processes/mechanisms at the molecular *** studies have developed sample-specific or cell-type-specific gene regulatory networks from single-cell transcriptomic data based on a large amount of cell ***,we review the state-of-the-art computational algorithms and describe various applications of gene regulatory networks in biological studies.

关键词： Gene regulatory network Single-cell RNA sequencing computational algorithm Sample-specificnetwork Cell-type-specific network Cell-specific network

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