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arXiv 2025年

作者： Delgado, Paola C.M. Ganz, Alexander Lin, Chunshan Thériault, Roxane CEICO FZU - Institute of Physics of the Czech Academy of Sciences Na Slovance 1999/2 Prague182 00 Czech Republic Institute for Theoretical Physics Leibniz University Hannover Appelstraße 2 Hannover30167 Germany Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Krakow30-348 Poland

Scalar particles traveling faster than a subluminal gravitational wave generate gravitons via gravitational Cherenkov radiation. In this paper, we investigate graviton production by the primordial plasma within the framework of modified gravity in the early Universe, generating a relic graviton background. We find that for the minimal model, where only the speed of gravitational waves is modified and a standard model plasma minimally couples to gravity, the relic graviton background can be enhanced by several orders of magnitude, but still agrees with the Big Bang Nucleosynthesis (BBN) bound in most cases. Moreover, we also find that for Horndeski theories, such as Galileon theory, the relic background produced by the thermalized scalar field can reach significant amplitudes, exceeding the BBN bound for a region of the parameter space. By requiring the relic graviton background to remain consistent with the BBN constraint, we derive limits on the gravitational wave speed at early times in these modified gravity theories. Copyright © 2025, The Authors. All rights reserved.

关键词： Gravitational effects

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Robust Feature Engineering Techniques for Designing Motor Imagery-Based Bci Systems

SSRN

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SSRN 2025年

作者： Gardezi Ahmed, Syed Saim Khan, Mahnoor Bukhari, Syeda Muneeba Khan, Rizwan Ahmed Jawed, Soyiba Department of Biomedical Engineering Faculty of Engineering Salim Habib University Karachi Pakistan Department of Computer Software Engineering College of Electrical and Mechanical Engineering NUST Islamabad Pakistan Department of Physics Faculty of Applied Sciences Riphah International University Islamabad Pakistan Department of Biomedical Engineering Faculty of Engineering NED University Karachi Pakistan Department of Computer Science Faculty of Information Technology Salim Habib University Karachi Pakistan

A multitude of individuals across the globe grapple with motor disabilities. Neural prosthetics utilizing Brain-computer Interface (BCI) technology exhibit promise for improving motor rehabilitation outcomes. The intricate nature of EEG data poses a significant hurdle for current BCI systems. Recently, a qualitative repository of EEG signals tied to both upper and lower limb execution of motor and motor imagery tasks has been unveiled. Despite this, the productivity of the Machine Learning (ML) Models that were trained on this dataset was alarmingly deficient, and the evaluation framework seemed insufficient. To enhance outcomes, robust feature engineering (signal processing) methodologies are implemented. A collection of time domain, frequency domain, and wavelet-derived features was obtained from 16-channel EEG signals, and the Maximum Relevance Minimum Redundancy (MRMR) approach was employed to identify the four most significant features. For classification K Nearest Neighbors, Support Vector Machine, Decision Tree, and Naive Bayes models were implemented with these selected features, evaluating their effectiveness through metrics such as testing accuracy, precision, recall, and F1 Score. By leveraging SVM with a Gaussian Kernel, a remarkable maximum testing accuracy of 92.50% for motor activities and 95.48% for imagery activities is achieved. These results are notably more dependable and gratifying compared to the previous study, where the peak accuracy was recorded at 74.36%. This research work provide an in-depth analysis of the MI Limb EEG dataset and it will help in designing and developing simple, cost-effective and reliable BCI systems for neuro-rehabilitation. © 2025, The Authors. All rights reserved.

关键词： Image enhancement

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Investigating the Redshift Evolution of Lensing Galaxy Density Slopes via Model-Independent Distance Ratios

arXiv

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arXiv 2025年

作者： Geng, Shuaibo Grespan, Margherita Thuruthipilly, Hareesh Harikumar, Sreekanth Pollo, Agnieszka Biesiada, Marek National Centre for Nuclear Research ul. Pasteura 7 Warsaw02-093 Poland Astronomical Observatory of the Jagiellonian University Faculty of Physics Astronomy and Applied Computer Science ul. Orla 171 Kraków30-244 Poland

Context. Strong lensing systems, expected to be abundantly discovered by next-generation surveys, provide a powerful tool for studying cosmology and galaxy evolution. The coupling between galaxy structure and cosmology through distance ratios makes examining the evolution of lensing galaxy mass density profiles essential for advancing both fields. Aims. We introduce a novel, dark energy-model-independent method to investigate the mass density slopes of lensing galaxies and their redshift evolution using an extended power-law (EPL) model. Methods. We adopt a non-parametric approach based on Artificial Neural Networks (ANNs) trained on Type Ia Supernovae (SNIa) data to reconstruct the distance ratios of strong lensing systems. These reconstructed ratios are compared with theoretical predictions to estimate the evolution of EPL model parameters. The analysis is performed at three levels - combined sample, individual lenses, and binned groups - to ensure robust estimates of the EPL parameters. Results. A negative evolutionary trend of mass density power-law exponent with increasing redshift is observed across different analysis levels. Assuming a triangular prior for the anisotropy of lensing galaxies, we find evidence for redshift evolution of the mass density slope, quantified as ∂γ/∂z = −0.20 ± 0.12. Conclusions. This study confirms that the redshift evolution of matter density slopes in lensing galaxies can be determined independent of dark energy models at the population level. Using simulations informed by Legacy Survey of Space and Time (LSST) Rubin Observatory forecasts, which is expected to identify 100,000 strongly lensed galaxies, we show that spectroscopic follow up of just 10% of these systems can reduce the uncertainty in the redshift evolution coefficient of the total mass density slope (∆∂γ/∂z) to 0.021. Such precision would be able to distinguish between evolving and non-evolving pictures for lensing galaxies. © 2025, CC BY-NC-ND.

关键词： Dark energy

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Contrastive Learning via Randomly Generated Deep Supervision

Contrastive Learning via Randomly Generated Deep Supervision

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Shibo Wang Zili Ma Ka-Hou Chan Yue Liu Tong Tong Qinquan Gao Guangtao Zhai Xiaohong Liu Tao Tan Faculty of Applied Sciences Macao Polytechnic University China Ischemaview Inc Menlo Park CA USA College of Physics and Information Engineering Fuzhou University Fuzhou China John Hopcroft Center for Computer Science Shanghai Jiao Tong University Shanghai China

ISBN: (数字)9798350368741

ISBN: (纸本)9798350368758

Unsupervised visual representation learning has gained significant attention in the computer vision community, driven by recent advancements in contrastive learning. Most existing contrastive learning frameworks rely on instance discrimination as a pretext task, treating each instance as a distinct category. However, this often leads to intra-class collision in a large latent space, compromising the quality of learned representations. To address this issue, we propose a novel contrastive learning method that utilizes randomly generated supervision signals. Our framework incorporates two projection heads: one handles conventional classification tasks, while the other employs a random algorithm to generate fixed-length vectors representing different classes. The second head executes a supervised contrastive learning task based on these vectors, effectively clustering instances of the same class and increasing the separation between different classes. Our method, Contrastive Learning via Randomly Generated Supervision(CLRGS), significantly improves the quality of feature representations across various datasets and achieves state-of-the-art performance in contrastive learning tasks.

关键词： Representation learning Visualization computer vision Signal processing algorithms Clustering algorithms Contrastive learning Signal processing Vectors Robustness Speech processing

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Miniaturization of Dimensions Based on Square Loop Resonator with NP Fractal Model for Sensor Applications

Miniaturization of Dimensions Based on Square Loop Resonator...

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International Electrical Engineering Congress (iEECON)

作者： Nutyada Nantapanich Norakamon Wongsin Nipont Tangthong Chawalit Rakluea Paitoon Rakluea Wanchalerm Chanwattanapong Nonchanutt Chudpooti Chatree Mahatthanajatuphat Department of Electronics and Telecommunication Engineering Faculty of Engineering Rajamangala University of Technology Thanyaburi Thailand Department of Industrial Physics and Medical Instrumentation Faculty of Applied Science King Mongkut's University of Technology North Bangkok Bangkok Thailand Department of Electrical and Computer Engineering Faculty of Engineering King Mongkut's University of Technology North Bangkok Bangkok Thailand

ISBN: (数字)9798331543952

ISBN: (纸本)9798331543969

This paper proposes a reduction in the dimensions of a square loop resonator via the utilization of fractal techniques. The 2 nd order NP fractal model is investigated to minimize the dimensions of the square loop resonator. The suggested fractal resonator is indirectly fed via the coupling line encircling the resonator to enhance impedance matching. The suggested fractal resonator has a frequency response of 2.936 GHz, with |S11| and |S21| evaluated at -16.17 dB and -2.09 dB, respectively. The dimensions of the suggested fractal resonator are 10.5×10.5 mm 2 , representing a reduction of roughly 56.9% compared to the square loop resonator. Consequently, the suggested fractal resonator may serve as a sensor for the measuring instrument.

关键词： Electrical engineering Couplings Instruments Impedance matching Fractals Frequency response

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Design of Ultra-Wideband Antipodal Vivaldi Antenna with Improving Impedance Matching using Elliptical Stub for GPR Applications

Design of Ultra-Wideband Antipodal Vivaldi Antenna with Impr...

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International Electrical Engineering Congress (iEECON)

作者： Patchadaporn Sangpet Wanchalerm Chanwattanapong Chayapol Sangmook Chatree Mahatthanajatuphat Thinnawat Jangjing Nonchanutt Chudpooti Paitoon Rakluea Norakamon Wongsin Department of Electronics and Telecommunication Engineering Faculty of Engineering Rajamangala University of Technology Thanyaburi Thailand Department of Electrical and Computer Engineering Faculty of Engineering King Mongkut's University of Technology North Bangkok Bangkok Thailand Department of Industrial Physics and Medical Instrumentation Faculty of Applied Science King Mongkut's University of Technology North Bangkok Bangkok Thailand

ISBN: (数字)9798331543952

ISBN: (纸本)9798331543969

This paper presents the design of an Antipodal Vivaldi Antenna (AVA) including open elliptical stubs on either side to improve impedance matching at lower frequencies. The stubs further serve as reflectors at 300 MHz, significantly enhancing the antenna gain across the specified frequency ranges. The Antipodal Vivaldi Antenna, measuring 552 × 700 × 1.6 mm 3 , is analyzed and evaluated to determine its characteristics. It possesses ultra-wideband characteristics, providing it suitable for signal exploration systems, and operates effectively throughout the 298–3000 MHz frequency range, which corresponds to the frequencies utilized by GPR technology. The suggested antenna demonstrates directed radiation patterns at all operational frequencies, achieving an average gain of 8.5 dBi.

关键词： Antenna measurements Electrical engineering Impedance matching Vivaldi antennas Reflector antennas Ultra wideband antennas Frequency measurement Reflection coefficient Gain Antenna radiation patterns

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Cross-linked chitosan/H-ZSM-5 zeolite composite film for chromium removal from aqueous solutions: optimization using response surface methodology and adsorption mechanism assessment

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Environmental science and Pollution Research 2025年 1-23页

作者： Slamani, Imene Bengharez, Zohra Boudouaia, Nacer Bendaoudi, Amine Ahmed Jellali, Salah Benhafsa, Fouad Mekhalef Mahmoudi, Hacene Benhadria, Naceur Guemra, Kaddour Jeguirim, Mejdi Laboratory of Advanced Materials and Physico-Chemistry for Environment and Health Faculty of Exact Sciences Djillali Liabes University Sidi Bel Abbes22000 Algeria Center for Environmental Studies and Research Sultan Qaboos University Muscat Oman Scientific and Technical Research Center in Physico-Chemical Analysis CRAPC Tipaza Algeria Faculty of Exact Sciences and Computer Science Abdelhamid Benbadis University Mostaganem Algeria National Higher School of Nanosciences and Nanotechnologies Algiers Sidi Abdellah Algeria University of Oran 1 Ahmed Ben Bella Oran Algeria Higher School of Applied Sciences P.O. Box 165 RP Tlemcen13000 Algeria Laboratory of Organic Chemistry Physics and Macromolecules Faculty of Exact Sciences Djillali Liabes University Sidi Bel Abbes22000 Algeria University of Haute Alsace University of Strasbourg CNRS UMR 7361 MulhouseF-68100 France

The present work investigates, for the first time, the synthesis of a composite film based on glutaraldehyde-cross-linked chitosan (GA-CS) and a natural zeolite (H-ZSM-5) and its application for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions under wide experimental conditions. The composite film (GA-CS-ZEO) characterization by using various analytical techniques confirms its successful production with promising physical, chemical, and thermal properties. The use of the response surface methodology (RSM) for the optimization of the Cr(VI) adsorption by this composite shows that that the maximum removal efficiency (82.39%) was achieved for a Cr(VI) concentration of 50 mg L−1, an initial pH of 2.0, a contact time of 100 min, and a temperature of 20 °C. Moreover, the analysis of variance (ANOVA) and 3D graphs indicated that the pH and initial Cr(VI) concentration were the main factors that influence the Cr(VI) uptake efficiency. Besides that, the Cr(VI) removal by the GA-CS-ZEO was found to be spontaneous and endothermic and occurs mainly via physical mechanisms involving electrostatic interactions and hydrogen bonding. Regeneration study of the Cr(VI)-loaded composite showed that Cr(VI) can be rapidly and efficiently desorbed by 0.1 M sulfuric acid. The results of the current research work highlight the important adsorption potential of Cr(VI) by the GA-CS-ZEO composite film and underscore its attractiveness and suitability for water treatment applications. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.

关键词： Hydrogen bonds

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Bulk-boundary correspondence from hyperinvariant tensor networks

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Physical Review D 2025年第2期111卷 026006-026006页

作者： Rafał Bistroń Mykhailo Hontarenko Karol Życzkowski Institute of Theoretical Physics Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University ul. Łojasiewicza 11 30-348 Kraków Poland Doctoral School of Exact and Natural Sciences Jagiellonian University ul. Łojasiewicza 11 30-348 Kraków Poland Center for Theoretical Physics (CFT) Polish Academy of Sciences Al. Lotników 32/46 02-668 Warszawa Poland

We introduce a tensor network designed to faithfully simulate the AdS/CFT correspondence, akin to the multiscale entanglement renormalization ansatz (MERA), following hyperinvariant tensor network. The proposed construction integrates bulk indices within the network architecture to uphold the key features of the HAPPY code, including complementary recovery. This framework accurately reproduces the boundary conformal field theory’s (CFT) two- and three-point correlation functions, while considering the image of any bulk operator. Furthermore, we provide an explicit methodology for calculating the correlation functions in an efficient manner. Our findings highlight the physical aspects of the relation between bulk and boundary within the tensor network models, contributing to the understanding and simulation of holographic principles in quantum information.

关键词：

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Structure, Electrical Resistivity and Superconductivity of Lowalloyed γ-U Phase Retained to Low Temperatures by Means of Rapid Cooling

引用

Acta Metallurgica Sinica(English Letters) 2016年第4期29卷 388-398页

作者： M.Krupska N.-T.H.Kim-Ngan S.Sowa M.Paukov I.Tkach D.Drozdenko L.Havela Z.Tarnawski Institute of Physics Pedagogical University Faculty of Mathematics and Physics Charles University Faculty of Physics and Applied Computer Science AGH University of Science and Technology

The γ-U phase alloys can be retained down to low temperatures with less required alloying concentration by using the splat-cooling technique with a cooling rate better than 10^6 K/s. Doping with 15 at.% Mo, Pt, Pd, Nb leads to a stabilization of the cubic γ-U phase, while it requires much higher Zr concentrations （≥30 at.% Zr）. All U-T splats become superconducting with Tc in the range of 0.61-2.11 K. A good agreement of the experimentally observed specific-heat jump at Tc with that from BCS theory prediction was obtained for U-15 at.% Mo consisting of the γ-U phase with an ideal bcc A2 structure.

关键词： Crystal structure Electrical resistivity Metallic system Superconductivity

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CONSTRUCTION AND CHARACTERISATION OF A CODED-MASK GAMMA CAMERA FOR BEAM RANGE MONITORING IN PROTON THERAPY

arXiv

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arXiv 2025年

作者： Kolodziej, Magdalena Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Kraków Poland

The major advantage of proton therapy over conventional radiotherapy is the dose deposition pattern: unlike X-rays, protons are entirely stopped in patient’s tissues with a distinct maximum of energy deposition at the end of their range, the Bragg peak. This enables precise coverage of the tumour volume while sparing nearby healthy tissues. However, accurate control of the proton beam range online during patient irradiation is still considered a challenge. Thus, there are extensive efforts to develop a detector capable of in vivo beam range monitoring for proton therapy, among them, the coded-mask gamma camera developed by the SiFi-CC group. The assembly of this detector, as well as its first test under clinical conditions, are the subject of this thesis. The detector consists of a structured collimator made of tungsten, and a stack of thin, elongated scintillation fibres, read out at both ends by silicon photomultipliers. Such a design allows for efficient detection of prompt gammas and reconstruction of a prompt gamma depth profile, which is strongly correlated with the proton beam range. The readout system for the detector was selected in an extensive comparison study of five different systems. After detector assembly, the detector was tested under clinical conditions: a phantom was irradiated with proton beams of energies from 70.51 MeV to 108.15 MeV, the detector response was processed with low-level reconstruction software, and the maximum-likelihood expectation maximisation algorithm was applied to reconstruct the prompt-gamma depth profiles (images). The distal falloff positions of these profiles were determined and compared with the calculated proton ranges. The image reconstruction parameters were optimised in terms of accuracy of proton range shift determination. The results obtained were checked against a Geant4 simulation, showing good consistency. The statistical precision was found to be 1.7 mm for 108 protons for a reference position close to the cen

关键词： Proton beam therapy

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