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A study of gravitational and non-gravitational modelling errors in cross-over differences

manuscripta geodaetica 2024年第4期15卷 187-206页

作者： Moore, P. Rothwell, D. A. Department of Computer Science and Applied Mathematics Aston University Aston Triangle Birmingham UK

Gravitational and non—gravitational modelling—errors in the satellite radial ephemeris are formulated with applications to altimeter cross—over difference measurements. Throughout use is made of Seasat altimetry and orbit determination. Gravitational errors are presented in a concise manner resulting from the use of an expansion of the geopotential in a form reminiscent of lumped harmonics in resonant studies. The effect of modelling errors in air drag on the radial distance is shown to be predominantly secular, but with a small sinusoidal term of increasing amplitude. Solar radiation similarly is seen to give rise to a sinusoidal term of increasing amplitude superimposed on a secular trend. From these radial expressions errors in cross—over difference measurements are derived. Cross—over errors are dominated by gravitational effects, but air—drag can give rise to an error proportional to the time difference, δt, between the crossover epochs, whilst solar radiation errors are translated into a term increasing with δt in addition to sinusoidal terms of increasing amplitudes. In particular, solar radiation pressure mis—modelling of the orbital eccentricity is seen to be the likely cause of the geographical North—South bias in cross—over residuals observed by several authors. The introduction of altimetry as tracking data is a powerful methodology to reduce such bias. By differencing successive cross—over differences on a given circle of latitude a data set is formed that is effectively independent of solar radiation and drag modelling errors and reflects the pure periodic component of the gravitational modelling error. Fourier analysis of SEASAT residuals has shown several lumped harmonics in GEM—T1 to be in need of improvement.

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Entropy generation optimisation for unsteady stagnation Casson nanofluid flow over a stretching sheet with binary chemical reaction and Arrhenius activation energy using the bivariate spectral quasi-linearisation method

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International Journal of Ambient Energy 2022年第1期43卷 6489-6501页

作者： Oyelakin, I.S. Mthethwa, H. Sithole Kameswaran, Peri K. Shaw, S. Sibanda, P. School of Computer Science and Applied Mathematics University of the Witwatersrand Johannesburg Braamfontein South Africa School of Mathematics Statistics and Computer Science University of KwaZulu-Natal Scottsville Pietermaritzburg South Africa Department of Mathematics School of Advanced Sciences Vellore Institute of Technology Vellore India Department of Mathematics and Statistical Sciences Botswana International University of Science and Technology Palapye Botswana

The heat and mass transport with Arrhenius activation energy has countless uses such as in nuclear reactors, the synthesis of chemical compounds, geothermal artificial lakes, and retrieval of thermal lubricants. The focus of this work is the analysis of Arrhenius activation energy and binary chemical reaction in a stagnation point Casson nanofluid flow over a stretching sheet. The system is subjected to a nonlinear radiation and a magnetic field. The transport equations are simplified using the Williams and Rhyne non-similar transformation. The solution to the transformed coupled system of nonlinear partial differential equations is obtained using the bivariate spectral quasi-linearisation method. Entropy generation that measures the degenerate useful energy and deprivation of the performance of engineering systems is analysed. Numerical results describing changes in the fluid velocity, temperature, concentration, entropy generation and Bejan number are presented and discussed for different fluid parameters. Activation energy parameter boosts up the solute concentration at the surface while an opposite is observed far away from the surface. The entropy generation decreases with an increase in the unsteady parameter and Casson number, while the opposite response was observed for a higher Reynolds number. Brinkman number gears up the entropy generation while it shows an opposite phenomenon for Bejan number. © 2022 Informa UK Limited, trading as Taylor & Francis Group.

关键词： Reynolds number

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Adaptive Reversible Visible Watermarking Based on Total Variation for BTC-Compressed Images

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computers, Materials & Continua 2023年第3期74卷 5173-5189页

作者： Hengfu Yang Mingfang Jiang Zhichen Gao School of Computer Science Hunan First Normal UniversityChangsha410205China Hunan Provincial Key Laboratory of Informationization Technology for Basic Education Changsha410205China Department of Applied Mathematics and Statistics College of Engineering and Applied SciencesStony Brook UniversityNY 11794USA

Few previous Reversible Visible Watermarking(RVW)schemes have both good transparency and watermark *** adaptive RVW scheme that integrates Total Variation and visual perception in Block Truncation Coding(BTC)compressed domain,called TVB-RVW is proposed in this paper.A new mean image estimation method for BTC-compressed images is first developed with the help of Total ***,a visual perception factor computation model is devised by fusing texture and luminance *** adaptive watermark embedding strategy is used to embed the visible watermark with the effect of the visual perception factor in the BTC ***,a lossless embedding method of the encrypted visible watermark is exploited to deter illegal watermark *** visible watermark can be removed since the visual perception factor and the estimated mean image remain unchanged before and after watermark *** experiments validate the superiority of the proposed algorithm over previous RVW schemes in BTC in terms of the visual quality of watermarked images and watermark visibility,and it can achieve a good balance between transparency and watermark visibility.

关键词： Reversible visible watermark block truncation coding visual perception total variation

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Exploring Teachers' Adoption of Web 2.0 Tools in a Thai University: A Case Study 8

Exploring Teachers' Adoption of Web 2.0 Tools in a Thai Univ...

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8th International Conference on Information Technology, InCIT 2024

作者： Rongbutsri, Nikorn Khalid, Md. Saifuddin Mae Fah Luang University School of Information Technology Chiang Rai Thailand Technical University of Denmark Department of Applied Mathematics and Computer Science Copenhagen Denmark

ISBN: (纸本)9798350366303

This paper explores the integration of Web 2.0 tools into teaching and learning at a Thai university, focusing on the alignment of these tools with specific pedagogical approaches to enhance engagement and learning outcomes. The study, conducted within the context of a blended learning environment influenced by the COVID-19 pandemic, employed problem-tree analysis and semi-structured interviews with faculty, IT support staff, and students. Findings reveal challenges related to tool complexity, the need for comprehensive teacher training, and the importance of aligning technology with pedagogical strategies. The research highlights the need for a more streamlined approach to Web 2.0 tool integration, emphasizing careful selection, effective teacher training, and a thoughtful blending of online and on-site learning experiences to improve student engagement and learning. The study contributes to the ongoing conversation surrounding effective technology integration in higher education by offering practical insights for improving teaching and learning in diverse contexts. © 2024 IEEE.

关键词： Contrastive Learning

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On a diffusive bacteriophage dynamical model for bacterial infections

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International Journal of Biomathematics 2023年第7期16卷 47-89页

作者： Hyacinthe M.Ndongmo Teytsa Berge Tsanou Jean Lubuma Samuel Bowong Department of Mathematics and Computer Science University of Dschang P.O.Bor 67DschangCameroon Department of Mathematics and Applied Mathematics University of Pretoria Pretoria 0002South Africa IRD UMI 209 UMMISCO University of Yaounde I P..Bor 337YaoundeCameroon LIRIMA-EPITAG Team Project University of Yaounde I P.O.Bor 812YaoundeCameroon Department of Mathematics and Computer Science University of Douala P.0.Bor 24157DoualaCameroon

Bacteriophages or phages are viruses that infect bacteria and are increasingly used to control bacterial *** develop a reaction-diffusion model coupling the interactive dynamic of phages and bacteria with an epidemiological bacteria-borne disease *** the submodel without phage absorption,the basic reproduction number Ro is *** disease-free equilibrium(DFE)is shown to be globally asymptotically stable whenever Ro is less than one,while a unique globally asymptotically endemic equilibrium is proven whenever Ro exceeds *** the presence of phage absorption,the above stated classical condition based on Ro,as the average number of secondary human infections produced by susceptible/lysogen bacteria during their entire lifespan,is no longer suficient to guarantee the global stability of the *** thus derive an additional threshold No,which is the average offspring number of lysogen bacteria produced by one infected human during the phage-bacteria interactions,and prove that the DFE is globally asymptotically stable whenever both Ro and No are under unity,and infections persist uniformly whenever Ro is greater than ***,the discrete counterpart of the continuous partial differential equation model is derived by constructing a nonstandard finite difference scheme which is dynamically *** consistency is shown by constructing suitable discrete Lyapunov functionals thanks to which the global stability results for the continuous model are *** scheme is implemented in MatLab platform and used to assess the impact of spatial distribution of phages,on the dynamic of bacterial infections.

关键词： Bacterial infections diffusion NSFD phage absorption global stability

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Findings of the Third Shared Task on Multilingual Coreference Resolution 7

Findings of the Third Shared Task on Multilingual Coreferenc...

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7th Workshop on Computational Models of Reference, Anaphora and Coreference, CRAC 2024

作者： Novák, Michal Dohnalová, Barbora Konopík, Miloslav Nedoluzhko, Anna Popel, Martin Pražák, Ondřej Sido, Jakub Straka, Milan Žabokrtský, Zdeněk Zeman, Daniel Charles University Faculty of Mathematics and Physics Institute of Formal and Applied Linguistics Prague Czech Republic University of West Bohemia Faculty of Applied Sciences Department of Computer Science and Engineering Pilsen Czech Republic

ISBN: (纸本)9798891761711

The paper presents an overview of the third edition of the shared task on multilingual coreference resolution, held as part of the CRAC 2024 workshop. Similarly to the previous two editions, the participants were challenged to develop systems capable of identifying mentions and clustering them based on identity coreference. This year’s edition took another step towards real-world application by not providing participants with gold slots for zero anaphora, increasing the task’s complexity and realism. In addition, the shared task was expanded to include a more diverse set of languages, with a particular focus on historical languages. The training and evaluation data were drawn from version 1.2 of the multilingual collection of harmonized coreference resources CorefUD, encompassing 21 datasets across 15 languages. 6 systems competed in this shared task. © 2024 Association for Computational Linguistics.

关键词： Computational linguistics

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On Dynamic α+ 1 Arboricity Decomposition and Out-Orientation 47

On Dynamic α+ 1 Arboricity Decomposition and Out-Orientatio...

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47th International Symposium on Mathematical Foundations of computer science, MFCS 2022

作者： Christiansen, Aleksander B.G. Holm, Jacob Rotenberg, Eva Thomassen, Carsten Department of Applied Mathematics and Computer Science Technical University of Denmark Denmark Department of Computer Science University of Copenhagen Copenhagen Denmark

ISBN: (纸本)9783959772563

A graph has arboricity α if its edges can be partitioned into α forests. The dynamic arboricity decomposition problem is to update a partitioning of the graph's edges into forests, as a graph undergoes insertions and deletions of edges. We present an algorithm for maintaining partitioning into α + 1 forests, provided the arboricity of the dynamic graph never exceeds α. Our algorithm has an update time of O(n3/4) when α is at most polylogarithmic in n. Similarly, the dynamic bounded out-orientation problem is to orient the edges of the graph such that the out-degree of each vertex is at all times bounded. For this problem, we give an algorithm that orients the edges such that the out-degree is at all times bounded by α + 1, with an update time of O (n5/7), when α is at most polylogarithmic in n. Here, the choice of α + 1 should be viewed in the light of the well-known lower bound by Brodal and Fagerberg which establishes that, for general graphs, maintaining only α out-edges would require linear update time. However, the lower bound by Brodal and Fagerberg is non-planar. In this paper, we give a lower bound showing that even for planar graphs, linear update time is needed in order to maintain an explicit three-out-orientation. For planar graphs, we show that the dynamic four forest decomposition and four-out-orientations, can be updated in O(n1/2) time. © 2022 Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing. All rights reserved.

关键词： Forestry

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Emotion Recognition Techniques 1

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1st international conference on Machine Intelligence and computer science Applications, ICMICSA 2022

作者： Knouzi, Maryam Ennaji, Fatima Zohra Hafidi, Imad Laboratory of Process Engineering Computer Science and Mathematics Department of Mathematics and Informatics National School of Applied Sciences University Sultan Moulay Slimane Beni-Mellal Morocco

ISBN: (数字)9783031293139

ISBN: (纸本)9783031288456

This article evaluates techniques for obtaining facial images from convolutional neural networks to identify emotion expressions. The primary goal of the paper is to discuss the most often used approaches to analyzing and recognizing emotional expressions on the face. The works that were reviewed might be divided into two major trends: the traditional techniques and those that were especially developed using neural *** analysis revealed that using CNNs improved level of performance. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Emotion Recognition

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Data-Driven Bandwidth Selection in Kernel Density Estimation via Unsupervised Learning 8th

Data-Driven Bandwidth Selection in Kernel Density Estimatio...

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8th International Symposium on Modelling and Implementation of Complex Systems, MISC 2024

作者： Guidoum, Arsalane Chouaib Henider, Amel Department of Mathematics and Computer Science Faculty of Sciences and Technology University of Tamanghasset Tamanghasset11000 Algeria Department of Finance and Actuarial National Higher School of Statistics and Applied Economics Kolea42003 Algeria

ISBN: (纸本)9783031821110

The selection of optimal bandwidth bw in Kernel Density Estimation (KDE) is crucial for accurate density estimation. Traditional methods, such as unbiased and biased cross-validation and their variants, often suffer from performance and computational limitations. This study presents a novel, data-driven approach to bandwidth selection using unsupervised machine learning techniques. Synthetic samples are generated from the original data, a comprehensive set of statistical parameters is calculated, and bandwidth is estimated using a rule-of-thumb [2]. Feature importance is assessed through random forests (RF) to identify the most influential factors in bandwidth selection. Various unsupervised learning models are then applied to predict the optimal bandwidth for the original sample bwos. The results demonstrate that this machine learning-based approach achieves superior accuracy and computational efficiency compared to traditional cross-validation methods. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.

关键词： Adversarial machine learning

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Developing an Artificial Intelligence Tool for Image Generation Using a Unique Dataset with Image-to-Image Functionality 24

Developing an Artificial Intelligence Tool for Image Generat...

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25th International Conference on computer Systems and Technologies, CompSysTech 2024

作者： Toktosunova, Akbiike Ergeshov, Alymbek Esenalieva, Gulzada Ermakov, Andrei Isaev, Ruslan Department of Applied Mathematics and Informatics Ala-Too International University Kyrgyzstan Department of Compute Science Ala-Too International University Kyrgyzstan Faculty of Engineering and Computer Science Ala-Too International University Kyrgyzstan

ISBN: (纸本)9798400716843

This article describes the application of a unique artificial intelligence model, trained on the basis of a special dataset, for drawing images. Artificial intelligence is very important in the modern world because it is a key driver of progress, offering innovative solutions to improve processes in various fields. A feature of this work is the use of the Stable Diffusion model and the creation of the LoRa model to create a specific object. The use of a special dataset, which is a classified set of images, to train models based on a stable propagation mechanism. The application of the image-to-image method, which consists in completely generating an image by having the model reproduce all the objects in the image, trying to preserve the maximum amount of detail in the image. As a result, a tool has been developed that can generate images of characters of a certain style. © 2024 ACM.

关键词： Adversarial machine learning

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