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arXiv 2023年

作者： Hladík, Milan Hartman, David Department of Applied Mathematics Faculty of Mathematics and Physics Charles University Malostranské nám. 25 Prague 111800 Czech Republic Computer Science Institute of Charles University Faculty of Mathematics and Physics Charles University Malostranské nám. 25 Prague 111800 Czech Republic Institute of Computer Science The Czech Academy of Sciences Czech Academy of Sciences Pod Vodárenskou věží 271/2 Prague 818207 Czech Republic

We deal with linear programming problems involving absolute values in their formulations, so that they are no more expressible as standard linear programs. The presence of absolute values causes the problems to be nonconvex and nonsmooth, so hard to solve. In this paper, we study fundamental properties on the topology and the geometric shape of the solution set, and also conditions for convexity, connectedness, boundedness and integrality of the vertices. Further, we address various complexity issues, showing that many basic questions are NP-hard to solve. We show that the feasible set is a (nonconvex) polyhedral set and, more importantly, every nonconvex polyhedral set can be described by means of absolute value constraints. We also provide a necessary and sufficient condition when a KKT point of a nonconvex quadratic programming reformulation solves the original *** Codes 90C26, 90C05, 90C30, 90C10 Copyright © 2023, The Authors. All rights reserved.

关键词： Linear programming

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Analysis of 238u, 232th, 222rn and 220rn Contents in Medical Drugs, Petroleum Products and Petrol/Gas-Oil Exhaust Fumes by Using Cr-39 and Lr-115 Type Ii Nuclear Track Detectors – Experimental and New Monte Carlo Simulation Approaches

SSRN

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SSRN 2023年

作者： Harrass, Hicham Touti, Rodouan El Ouardi, Brahim El Fakir, Makrame Ben Andaloussi, Lamia Hjiyej Chakir, Hamid Nutrition Environment and Cancer Team Faculty of Medicine and Pharmacy Hassan II University of Casablanca Morocco Laboratory of Applied Physics Computer Science and Statistics Faculty of Sciences Dhar El Mahraz Sidi Mohamed Ben Abdellah University Fez Morocco Department of Physics LPMC-ERSA Faculty of Sciences Ben M’sik Hassan II University of Casablanca Morocco Medical Physics Unit Radiation Therapy Service University Hospital Center of Marrakech Morocco

Petroleum products and medical drugs have been studied in order to determine 238U, 232Th, 222Rn, 220Rn and their progenies contents in them using mean detection efficiency based Solid State Nuclear Track Detectors (SSNTDs) experimental method. In the present paper, a Monte Carlo code based theoretical approach has been also developed to determine mean detection efficiencies of SSNTDs;this theoretical approach has been combined with experimental one for deriving levels of natural radioactivity inside different materials studied. The dependence of CR-39 and LR-115 type II mean detection efficiencies on initial alpha particle energy, removed thickness of SSNTDs and SSNTDs areas for different natural materials studied has been highlighted as well. The mean detection efficiency depends clearly on the initial alpha particle energy and the removed layer while it does depend neither on the detector surface nor on the nature of the material being studied. The results obtained using the present method and those obtained by mean critical angle based SSNTD technique and isotope dilution mass spectroscopy (IDMS) are in good agreement with each other: our method has less relative uncertainties, which do not exceed 4%, than the other methods, whose the relative uncertainties exceed 9% and 7%, respectively. © 2023, The Authors. All rights reserved.

关键词： Gasoline

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Effective Classification for Logs of Routers Based on MLP Neural Networks

Effective Classification for Logs of Routers Based on MLP Ne...

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International Conference on Knowledge and Systems Engineering (KSE)

作者： Bao-Thien Nguyen-Tat Duy Khanh Nguyen Faculty of Information Science and Engineering University of Information Technology Ho Chi Minh City Vietnam Vietnam National University Ho Chi Minh City Vietnam Laboratory for Computational Physics Institute for Computational Science and Artificial Intelligence Van Lang University Ho Chi Minh City Vietnam Faculty of Mechanical - Electrical and Computer Engineering School of Technology Van Lang University Ho Chi Minh City Vietnam

This article discusses the classification of abnormal log messages from Juniper routers. Abnormal log messages reflect the unusual activities of these routers. Classifying abnormal log messages into different categories helps monitoring personnel quickly identify errors and take timely measures to protect the devices. We extract features from abnormal logs and use a Multilayer Perceptron (MLP) neural network model for classification. The MLP neural network model requires knowledge of the log data from Juniper routers so that the trained network can analyze and validate that knowledge. We collected log data from Juniper routers operating on SCTV's core network system, identified abnormal log messages, and classified them based on our experience and knowledge.

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Angular harmonic Hall voltage and magnetoresistance measurements of Pt/FeCoB and Pt-Ti/FeCoB bilayers for spin Hall conductivity determination

arXiv

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arXiv 2021年

作者： Skowronski, Witold Grochot, Krzysztof Rzeszut, Piotr Lazarski, Stanislaw Gajoch, Grzegorz Worek, Cezary Kanak, Jaroslaw Stobiecki, Tomasz Langer, Jürgen Ocker, Berthold Vafaee, Mehran AGH University of Science and Technology Institute of Electronics Al. Mickiewicza 30 Kraków30-059 Poland AGH University of Science and Technology Faculty of Physics and Applied Computer Science Al. Mickiewicza 30 Kraków30-059 Poland Singulus Technologies AG Hanauer Landstrasse 103 Kahl am Main63796 Germany

Materials with significant spin-orbit coupling enable efficient spin-to-charge interconversion, which can be utilized in novel spin electronic devices. A number of elements, mainly heavy-metals (HM) have been identified to produce a sizable spin current (js), while supplied with a charge current (j), detected mainly in the neighbouring ferromagnetic (FM) layer. Apart from the spin Hall angle θSH = js/j, spin Hall conductivity (σSH) is an important parameter, which takes also the resistivity of the material into account. In this work, we present a measurement protocol of the HM/FM bilayers, which enables for a precise σSH determination. Static transport measurements, including resistivity and magnetization measurements are accompanied by the angular harmonic Hall voltage analysis in a dedicated low-noise rotating probe station. Dynamic characterization includes effective magnetization and magnetization damping measurement, which enable HM/FM interface absorption calculation. We validate the measurement protocol in Pt and Pt-Ti underlayers in contact with FeCoB and present the σSH of up to 3.3x105 S/m, which exceeds the values typically measured in other HM, such as W or Ta. Copyright © 2021, The Authors. All rights reserved.

关键词： Spin Hall effect

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Combining Gaussian processes and neural networks in surrogate modeling for covariance matrix adaptation evolution strategy 21

Combining Gaussian processes and neural networks in surrogat...

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21st Conference Information Technologies - Applications and Theory, ITAT 2021

作者： Koza, Jan Tumpach, Jiří Pitra, Zbyněk Holeňa, Martin Czech Technical University Faculty of Information Technology Prague Czech Republic Charles University Faculty of Mathematics and Physics Prague Czech Republic Czech Technical University Faculty of Nuclear Sciences and Physical Engineering Prague Czech Republic Academy of Sciences Institute of Computer Science Prague Czech Republic

This paper focuses on surrogate models for Covariance Matrix Adaptation Evolution Strategy (CMA-ES) in continuous black-box optimization. Surrogate modeling has proven to be able to decrease the number of evaluations of the objective function, which is an important requirement in some real-world applications where the evaluation can be costly or time-demanding. Surrogate models achieve this by providing an approximation instead of the evaluation of the true objective function. One of the state-of-the-art models for this task is the Gaussian process. We present an approach to combining Gaussian processes with artificial neural networks, which was previously successfully applied to other machine learning domains. The experimental part employs data recorded from previous CMA-ES runs, allowing us to assess different settings of surrogate models without running the whole CMA-ES algorithm. The data were collected using 24 noiseless benchmark functions of the platform for comparing continuous optimizers COCO in 5 different dimensions. Overall, we used data samples from over 2.8 million generations of CMA-ES runs. The results examine and statistically compare six covariance functions of Gaussian processes with the neural network extension. So far, the combined model did not show up to outperform the Gaussian process alone. Therefore, in conclusion, we discuss possible reasons for this and ideas for future research. Copyright © 2021 for this paper by its authors.

关键词： Neural networks

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DSG-GAN:A dual-stage-generator-based GAN for cross-modality synthesis from PET to CT

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computers in Biology and Medicine 2024年 172卷 108296-108296页

作者： Wang, Huabin Wang, Xiangdong Liu, Fei Zhang, Grace Zhang, Gong Zhang, Qiang Lang, Michael L. Anhui Provincial International Joint Research Center for Advanced Technology in Medical Imaging School of Computer Science and Technology Anhui University Anhui Hefei230601 China Faculty of Engineering Western University Canada Physical Examination Center of The Affiliated Hospital of Inner Mongolia Medical University Inner Mongolia Hohhot010010 China School of Public Health Anhui University of Science and Technology Anhui HuaiNan232001 China Department of Physics University of Winnipeg 515 Portage Ave. WinnipegMB Canada Sino Canadian Health Research Institute WinnipegMB Canada

PET/CT devices typically use CT images for PET attenuation correction, leading to additional radiation exposure. Alternatively, in a standalone PET imaging system, attenuation and scatter correction cannot be performed due to the absence of CT images. Therefore, it is necessary to explore methods for generating pseudo-CT images from PET images. However, traditional PET-to-CT synthesis models encounter conflicts in multi-objective optimization, leading to disparities between synthetic and real images in overall structure and texture. To address this issue, we propose a staged image generation model. Firstly, we construct a dual-stage generator, which synthesizes the overall structure and texture details of images by decomposing optimization objectives and employing multiple loss functions constraints. Additionally, in each generator, we employ improved deep perceptual skip connections, which utilize cross-layer information interaction and deep perceptual selection to effectively and selectively leverage multi-level deep information and avoid interference from redundant information. Finally, we construct a context-aware local discriminator, which integrates context information and extracts local features to generate fine local details of images and reasonably maintain the overall coherence of the images. Experimental results demonstrate that our approach outperforms other methods, with SSIM, PSNR, and FID metrics reaching 0.8993, 29.6108, and 29.7489, respectively, achieving the state-of-the-art. Furthermore, we conduct visual experiments on the synthesized pseudo-CT images in terms of image structure and texture. The results indicate that the pseudo-CT images synthesized in this study are more similar to real CT images, providing accurate structure information for clinical disease analysis and lesion localization. © 2024 Elsevier Ltd

关键词： Discriminators

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A Comprehensive Study on Hot Deformation Behaviour of the Metastable Β Titanium Alloy Prepared by Blended Elemental Powder Metallurgy Approach

SSRN

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SSRN 2023年

作者： Zygula, Krystian Lypchanskyi, Oleksandr Lukaszek-Solek, Aneta Korpala, Grzegorz Stanik, Rafal Kubiś, Michal Przybyszewski, Bartlomiej Wojtaszek, Marek Gude, Maik Prahl, Ulrich AGH University of Science and Technology Faculty of Metals Engineering and Industrial Computer Science Al. A. Mickiewicza 30 Krakow30-059 Poland Institut für Metallformung TU Bergakademie Freiberg 4 Bernhard-von-Cotta-Straße Freiberg09596 Germany Technische Universität Dresden Dresden Germany Faculty of Power and Aeronautical Engineering Institute of Heat Engineering Warsaw University of Technology Nowowiejska St. 21/25 Warsaw00-665 Poland Faculty of Materials Science and Engineering Warsaw University of Technology Woloska 141 Warsaw02-507 Poland

The hot deformation behavior of a Ti-5Al-5Mo-5V-3Cr alloy obtained by the Blended Elemental Powder Metallurgy approach was investigated. The hot compression tests were carried out to determine the stress-strain relationships at the temperature range of 800 °C to 1000 °C and strain rate between 0.1 s-1 and 20 s-1. The constitutive model based on the Arrhenius-type constitutive equation was developed as well as the deformation activation energy map. Based on the Dynamic Material Model theory, processing maps at constant strain values were developed using data obtained from hot compression tests. The processing window that indicated the optimum hot deformation parameters was determined at the temperature range of 900 ºC to 1000 ºC and strain rates of 0.1 – 2.0 s-1. The verification of the developed results was successfully confirmed based on the observations of the microstructures of samples after hot compression tests. Then, the hot rolling process was designed using FEM modeling and successfully verified by laboratory tests. The relationship of the deformation parameters, microstructure, and hardness of Ti-5Al-5Mo-5V-3Cr alloy was analyzed. © 2023, The Authors. All rights reserved.

关键词： Finite element method

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Swarmodroid 1.0: A Modular Bristle-Bot Platform for Robotic Active Matter Studies

arXiv

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arXiv 2023年

作者： Dmitriev, Alexey A. Rozenblit, Alina D. Porvatov, Vadim A. Buzakov, Mikhail K. Molodtsova, Anastasia A. Sennikova, Daria V. Smirnov, Vyacheslav A. Burmistrov, Oleg I. Karimov, Timur I. Puhtina, Ekaterina M. Olekhno, Nikita A. School of Physics and Engineering ITMO University Saint Petersburg197101 Russia Department of Infocommunication Technologies National University of Science and Technology "MISIS" Moscow119991 Russia Faculty of Science University of Amsterdam Amsterdam1098 XH Netherlands Department of Computer-Aided Design Saint Petersburg Electrotechnical University"LETI" Saint Petersburg197376 Russia

Large swarms of extremely simple robots (i.e., capable just of basic motion activities, like propelling forward or self-rotating) are widely applied to study collective task performance based on self-organization or local algorithms instead of sophisticated programming and global swarm coordination. Moreover, they represent a versatile yet affordable platform for experimental studies in physics, particularly in active matter – non-equilibrium assemblies of particles converting their energy to a directed motion. However, a large set of robotics platforms is being used in different studies, while the universal design is still lacking. Despite such platforms possess advantages in certain application scenarios, their large number sufficiently limits further development of results in the field, as advancing some study requires to buy or manually produce the corresponding robots. To address this issue, we develop an open-source Swarmodroid 1.0 platform based on bristle-bots with reconfigurable 3D-printed bodies, external control of motion velocity, and basic capabilities of velocity profile programming. In addition, we introduce AMPy software package in Python featuring OpenCV-based extraction of robotic swarm kinematics accompanied by the evaluation of key physical quantities describing the collective dynamics. We perform a detailed analysis of individual Swarmodroids’ motion characteristics and address their use cases with two examples: a cargo transport performed by self-rotating robots and a velocity-dependent jam formation in a bottleneck by self-propelling robots. Finally, we provide a comparison of existing centimeter-scale robotic platforms, a review of key quantities describing collective dynamics of many-particle systems, and a comprehensive outlook considering potential applications as well as further directions for fundamental studies and Swarmodroid 1.0 platform development. Copyright © 2023, The Authors. All rights reserved.

关键词： Robot programming

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Magnetization reversal driven by electron localization-delocalization crossover in the inverse spinel Co2VO4

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Physical Review B 2022年第9期105卷 094408-094408页

作者： Abhijit Bhat Kademane Churna Bhandari Durga Paudyal Stephen Cottrell Pinaki Das Yong Liu Yuen Yiu C. M. Naveen Kumar Konrad Siemensmeyer Andreas Hoser Diana Lucia Quintero-Castro David Vaknin Rasmus Toft-Petersen Department of Mathematics and Physics Universitetet i Stavanger 4036 Stavanger Norway Ames Laboratory Iowa State University Ames Iowa 50011 USA Department of Electrical and Computer Engineering Iowa State University Ames Iowa 50011 USA ISIS Facility STFC Rutherford Appleton Laboratory Harwell Science and Innovation Campus Chilton Didcot Oxon OX11 0QX United Kingdom Institute of Solid State Physics Vienna University of Technology Wiedner Hauptstrae 810 1040 Vienna Austria AGH University of Science and Technology Faculty of Physics and Applied Computer Science 30-059 Kraków Poland Helmholtz Zentrum Berlin für Materialien und Energie D-14109 Berlin Germany Department of Physics and Astronomy Iowa State University Ames Iowa 50011 USA Department of Physics Technical University of Denmark DK-2800 Kongens Lyngby Denmark European Spallation Source Partikelgatan 2 224 84 Lund Sweden

Neutron diffraction, magnetization, and muon spin relaxation measurements, supplemented by density functional theory (DFT) calculations are employed to unravel temperature-driven magnetization reversal in inverse spinel Co2VO4. All measurements show a second-order magnetic phase transition at TC=168K to a collinear ferrimagnetic phase. Neutron diffraction measurements reveal two antiparallel ferromagnetic (FM) sublattices, belonging to magnetic ions on two distinct crystal lattice sites, where the relative balance between the two sublattices determine the net FM moment in the unit cell. As the evolution of the ordered moment with temperature differs between the two sublattices, the net magnetic moment reaches a maximum at TNC=138K and reverses its sign at TMR=65K. The DFT results suggest that the underlying microscopic mechanism for the reversal is a delocalization of the unfilled 3d-shell electrons on one sublattice just below TC, followed by a gradual localization as the temperature is lowered. This delocalized-localized crossover is supported by muon spectroscopy results, as strong T1 relaxation observed below TC indicates fluctuating internal fields.

关键词： Density of states Ferrimagnetism Metal-insulator transition Oxides Spinels Density functional calculations Magnetization measurements Muon spin relaxation & rotation Neutron scattering

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Exploiting Optical Nonlinear Temporal Coupling for Implementing Physical Unclonable Functions

Exploiting Optical Nonlinear Temporal Coupling for Implement...

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IEEE World Forum on Internet of Things (WF-IoT)

作者： Stavros G. Stavrinides Lydia Bush-Espinosa Carol de Benito Nikolaos Athanasios Anagnostopoulos Tolga Arul Stefan Katzenbeisser Christos Tjortjis M. Moner Al Chawa Rodrigo Picos Physics Department International Hellenic University Kavala Greece Industrial Engineering Department Universitat de les Illes Balears Palma Spain Faculty of Computer Science and Mathematics University of Passau Passau Germany School of Science and Technology International Hellenic University Thessaloniki Greece Institute of Circuits and Systems Technical University Dresden Dresden Germany

ISBN: (数字)9798350311617

ISBN: (纸本)9798350311624

In this work, we study the possibility of utilizing an LED-LDR pair for generating a Physical Unclonable Function. Towards this, the nonlinear response between an optically cou-pled LED-LDR pair, as well as the dynamic behavior of the LDR, were considered. The resulting behavior was highly nonlinear and strongly dependent on the actual physical properties of the components. We tested the idea using different LEDs (red, green, and blue; two of each color), and an LDR. Using a low-cost system (an Arduino development board), we showed that although the static response is very linear, the dynamic response is highly unpredictable, when the system is driven by random values. However, this response is identical for the same LED-LDR pairs, but different for other combinations. Additionally, the described behavior is fully repeatable. Thus, a low-cost PUF can be created using these simple components, allowing not only discrimination of the LED's color, but also for the creation of a digital fingerprint as well as authentication/verification.

关键词： Resistors Resistance Color Fingerprint recognition Physical unclonable function Light emitting diodes Nonlinear optical devices

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