Frontiers in Physics最新文献

{"title":"A simple two-stage carrier-phase estimation algorithm for 32-QAM coherent optical communication systems","authors":"Min Peng, Xiangqing Wang, Xiaokun Yang, Dongfei Wang","doi":"10.3389/fphy.2024.1452087","DOIUrl":"https://doi.org/10.3389/fphy.2024.1452087","url":null,"abstract":"The combination of high-order modulation formats and linewidth-tolerant carrier phase estimation (CPE) can effectively improve spectrum efficiency and relax the limitation of laser linewidth. This paper presents a simple two-stage CPE algorithm for polarization-multiplexed (PM) 32-quadrature amplitude modulation (32-QAM) coherent optical communication systems. The algorithm uses an enhanced QPSK partitioning algorithm combined with a simplified 4th power CPE method for coarse estimation in the initial stage and maximum likelihood (ML) detection in the subsequent fine stage. The CPE algorithm significantly increases the number of symbols used in the first stage of coarse estimation. This results in a significant increase in the stability and reliability of the phase estimation, and the CPE algorithm significantly reduces the computational complexity. The optimal parameters, phase estimation performance, and system performance of the algorithm were investigated by building a 22 Gbaud PM 32-QAM coherent system simulation platform and a 5 Gbaud PM 32-QAM coherent system experimental platform. The results show that the proposed two-stage CPE algorithm has a stronger linewidth tolerance difference than the conventional QPSK, and the two-stage CPE algorithm with an optimal block length of 105 performs comparable to blind phase search (BPS). The optical signal noise Ratio (OSNR) value is 21.2 dB and the bit error rate (BER) is 1.8 × 10<jats:sup>−3</jats:sup> for the optimal block length of 105. The receiving-end DSP unit with a flexible scheme and good communication performance will have potential applications in adaptive elastic optical networks.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"2 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"What do we learn from impurities and disorder in high-Tc cuprates?","authors":"Henri Alloul","doi":"10.3389/fphy.2024.1406242","DOIUrl":"https://doi.org/10.3389/fphy.2024.1406242","url":null,"abstract":"A series of experimental studies established that the differing morphologies of the phase diagrams &lt;jats:italic&gt;versus&lt;/jats:italic&gt; hole doping &lt;jats:italic&gt;n&lt;/jats:italic&gt;&lt;jats:sub&gt;&lt;jats:italic&gt;h&lt;/jats:italic&gt;&lt;/jats:sub&gt; of the various cuprate families are mostly controlled by defects and disorder. In the minimally disordered cuprate Yttrium Baryum Copper Oxide (YBCO) we introduced controlled detfects that allowed us to probe the metallic and superconducting states. We demonstrate that the extent of the spin glass phase and the superconducting dome can be controlled by the concentration of spinless (Zn, Li) impurities substituted on the planar Cu sites. NMR frequency shift measurements establish that these defects induce, in their vicinity, a cloud with a Kondo-like paramagnetic behavior. Its “Kondo” temperature and spatial extent differ markedly between the pseudogap and strange metal regimes. We have performed transport measurements on single crystals with a controlled content of in-plane vacancies introduced by electron irradiation. At high &lt;jats:italic&gt;T&lt;/jats:italic&gt;, the inelastic scattering of the carriers has been found independent of disorder and completely governed by the excitations of the correlated electronic state. The low &lt;jats:italic&gt;T&lt;/jats:italic&gt; upturns in the resistivity associated with single-site Kondo-like scattering are qualitatively in agreement with local magnetism induced by spinless impurities. The apparent metal insulator crossover is only detected for a very large defect content, and part of the large resistivity upturn remains connected with Kondo-like paramagnetism. In the superconducting state, the defect-induced reduction of &lt;jats:italic&gt;T&lt;/jats:italic&gt;&lt;jats:sub&gt;&lt;jats:italic&gt;c&lt;/jats:italic&gt;&lt;/jats:sub&gt; scales linearly with the increase in residual resistivity induced by disorder. High-field magnetoresistance experiments permit us to determine the paraconductivity due to superconducting fluctuations. The latter vanishes beyond a temperature &lt;jats:italic&gt;T’&lt;/jats:italic&gt;&lt;jats:sub&gt;&lt;jats:italic&gt;c&lt;/jats:italic&gt;&lt;/jats:sub&gt; and a field &lt;jats:italic&gt;H’&lt;/jats:italic&gt;&lt;jats:sub&gt;&lt;jats:italic&gt;c&lt;/jats:italic&gt;&lt;/jats:sub&gt; that both decrease with increasing in-plane defect content. In the pseudogap regime, the weaker decrease of &lt;jats:italic&gt;T’&lt;/jats:italic&gt;&lt;jats:sub&gt;&lt;jats:italic&gt;c&lt;/jats:italic&gt;&lt;/jats:sub&gt; with respect to that of &lt;jats:italic&gt;T&lt;/jats:italic&gt;&lt;jats:sub&gt;&lt;jats:italic&gt;c&lt;/jats:italic&gt;&lt;/jats:sub&gt; reveals a large loss of superconducting phase coherence in the presence of disorder. In light of our experimental results, we initiate a discussion of its interplay with pair breaking. Our data also permit us to confirm that the differing phase diagrams are due to competing orders or disorders that are family-specific. In the ideal phase diagram of a disorder-free cuprate, 2D superconductivity should persist at low doping. This ensemble of experimental results provides serious challenges for the theoretical understanding of s","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"62 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heavy users fail to fall into filter bubbles: evidence from a Chinese online video platform","authors":"Chenbo Fu, Qiushun Che, Zhanghao Li, Fengyan Yuan, Yong Min","doi":"10.3389/fphy.2024.1423851","DOIUrl":"https://doi.org/10.3389/fphy.2024.1423851","url":null,"abstract":"Accelerated by technological advancements, while online platforms equipped with recommendation algorithms offer convenience to obtain information, it also brought algorithm bias, shaping the norms and behaviors of their users. The filter bubble, conceived as a negative consequence of algorithm bias, means the reduction of the diversity of users’ information consumption, garnering extensive attention. Previous research on filter bubbles typically used users’ self-reported or behavioral data independently. However, existing studies have disputed whether filter bubbles exist on the platform, possibly owing to variations in measurement methods. In our study, we took content category diversity to measure the filter bubbles and innovatively used a combination of participants’ self-reported and website behavioral data, examining filter bubbles on a single online video platform (Bilibili). We conducted a questionnaire survey among 337 college students and collected 3,22,324 browsing records with their informed authorization, constituting the dataset for research analysis. The existence of filter bubbles on Bilibli is found, such that diversity will decrease when viewing <jats:italic>Game</jats:italic> videos increases. Furthermore, we considered the factors that influence filter bubbles from the perspective of demographics and user behavior. In demographics, female and non-member users are more likely to be trapped in filter bubbles. In user behavior, results of feature importance analysis indicate that the diversity of information consumption of heavy users is higher than others, and both activity and fragmentation have an impact on the formation of filter bubbles, but in different directions. Finally, we discuss the reasons for these results and a theoretical explanation that the filter bubbles effect may be lower than we thought for both heavy and normal users on online platforms. Our conclusions provide valuable insights for understanding filter bubbles and platform management.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"38 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic behavior of a two-mass nonlinear fractional-order vibration system","authors":"Yu-Xing Han, Jia-Xin Zhang, Yu-Lan Wang","doi":"10.3389/fphy.2024.1452138","DOIUrl":"https://doi.org/10.3389/fphy.2024.1452138","url":null,"abstract":"The two-mass nonlinear vocal cord vibration system (VCVS) serves as a mechanical representation of the fundamental vocalization process. Traditional models of the VCVS, which are based on integer-order dynamics, often overlook the impact of memory effects. To address this limitation and enhance the accuracy of simulations, this study incorporates the memory effects of vocal cord vibrations by integrating the Grunwald–Letnikov fractional derivative into the two-mass nonlinear VCVS framework. Initially, a high-precision computational scheme is formulated for the two-mass nonlinear fractional-order VCVS. Subsequently, the model undergoes a comprehensive series of numerical simulations to investigate its dynamic characteristics. The findings reveal that the dynamics of the fractional-order VCVS exhibit a significantly higher complexity compared to the conventional integer-order models, with the emergence of novel chaotic behaviors that were previously unobserved.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"5 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hyperboloidal method for quasinormal modes of non-relativistic operators","authors":"Christopher Burgess, Friedrich König","doi":"10.3389/fphy.2024.1457543","DOIUrl":"https://doi.org/10.3389/fphy.2024.1457543","url":null,"abstract":"The recently reported compactified hyperboloidal method has found wide use in the numerical computation of quasinormal modes, with implications for fields as diverse as gravitational physics and optics. We extend this intrinsically relativistic method into the non-relativistic domain, demonstrating its use to calculate the quasinormal modes of the Schrödinger equation and solve related bound-state problems. We also describe how to further generalize this method, offering a perspective on the importance of non-relativistic quasinormal modes for the programme of black hole spectroscopy.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"60 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dialectal tsunamis emerging from the Simmel effect: a statistical approach to the snail-paced spread of cultural epidemic","authors":"Kazuya Hayata","doi":"10.3389/fphy.2024.1425907","DOIUrl":"https://doi.org/10.3389/fphy.2024.1425907","url":null,"abstract":"An attempt is made to settle the controversy on a theory of the concentric distribution of dialectal variants for snails. This theory was presented in 1927 by Kunio Yanagita (1875–1962), outstanding Japanese folklorist. Over more than 95 years, however, its verification remains pending. On the basis of the recent achievement in the linguistic atlas project, time series analysis is made for fitting to the long-tailed rank-frequency relations of cumulative syllabics that are included in the entire dialect sequence of snails. The time reversal asymmetry (TRA) is revealed through comparison between the forward and backward analysis. The validity of the methodology is confirmed through comparison with results for several examples. Computed results show substantial TRAs between the periphery-to-center and center-to-periphery analysis for fitting to the long-tailed distribution in the cumulative frequency versus rank. This feature for the categorial data sequence is consistent with those observed for typical numerical data such as music and heartbeat signals that obey non-Gaussian statistics. Application to the most parsimonious principle yields results being compatible with the above ones, which reproduces the validity of our conclusion. Finally, perturbation analysis is made for several artificially disturbed arrangements of the dialectal strata.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"1 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiclass small target detection algorithm for surface defects of chemicals special steel","authors":"Yuanyuan Wang, Shaofeng Yan, Hauwa Suleiman Abdullahi, Shangbing Gao, Haiyan Zhang, Xiuchuan Chen, Hu Zhao","doi":"10.3389/fphy.2024.1451165","DOIUrl":"https://doi.org/10.3389/fphy.2024.1451165","url":null,"abstract":"Introduction: Chemical special steels are widely used in chemical equipment manufacturing and other fields, and small defects on its surface (such as cracks and punches) are easy to cause serious accidents in harsh environments.Methods: In order to solve this problem, this paper proposes an improved defect detection algorithm for chemical special steel based on YOLOv8. Firstly, in order to effectively capture local and global information, a ParC2Net (Parallel-C2f) structure is proposed for feature extraction, which can accurately capture the subtle features of steel defects. Secondly, the loss function is adjusted to MPD-IOU, and its dynamic non-monotonic focusing characteristics are used to effectively solve the overfitting problem of the bounding box of low-quality targets. In addition, RepGFPN is used to fuse multi-scale features, deepen the interaction between semantics and spatial information, and significantly improve the efficiency of cross-layer information transmission. Finally, the RexSE-Head (ResNeXt-Squeeze-Excitation) design is adopted to enhance the positioning accuracy of small defect targets.Results and discussion: The experimental results show that the mAP@0.5 of the improved model reaches 93.5%, and the number of parameters is only 3.29M, which realizes the high precision and high response performance of the detection of small defects in chemical special steels, and highlights the practical application value of the model. The code is available at <jats:ext-link>https://github.com/improvment/prs-yolo</jats:ext-link>.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"1 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Designing electromagnetic resonators with quasinormal modes","authors":"Tong Wu, Philippe Lalanne","doi":"10.3389/fphy.2024.1461106","DOIUrl":"https://doi.org/10.3389/fphy.2024.1461106","url":null,"abstract":"Micro- and nanoresonators, which enable light trapping in small volumes for extended durations, play a crucial role in modern photonics. The optical response of these resonators is determined by their fundamental resonances, known as quasinormal modes (QNMs). Over the past decade, the electromagnetic theory of QNMs has undergone significant development and has now reached a level of maturity that allows its reliable application to numerous contemporary electromagnetic problems. In this review, we explore recent applications of QNM theory for designing and understanding micro and nanoresonators. We highlight why QNMs provide deep physical insights and enhance computational efficiency in scenarios involving mode hybridization and perturbation.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"290 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The polychromatic retrigger: a new tool to mitigate pileup in spectral photon-counting computed-tomography","authors":"Carlo Amato, Christian Disch, Pietro Zambon","doi":"10.3389/fphy.2024.1445538","DOIUrl":"https://doi.org/10.3389/fphy.2024.1445538","url":null,"abstract":"High photon rates, like the ones required in clinical computed tomography, can generate pulse pileup in photon-counting detectors, and in extreme cases induce system paralysis. The instant retrigger technology has been developed by DECTRIS Ltd. to counteract such phenomena, effectively making detectors non-paralyzable. The instant retrigger behavior is regulated by a quantity named retrigger time, which originally was the same for all the energy thresholds of the detector. We developed a new ASIC that features an improved version of the instant retrigger (polychromatic retrigger) that allows different retrigger times for each of the four energy thresholds. In this work, we investigate how this feature can be exploited in computed tomography to mitigate pileup artifacts. Using a Monte Carlo method, we modeled a full computed tomography system with four energy thresholds (20, 50, 70 and 90 keV), and we simulated head scans from low (1<jats:inline-formula><mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"><mml:mo>×</mml:mo></mml:math></jats:inline-formula>10<jats:sup>7</jats:sup> cps/mm<jats:sup>2</jats:sup>) to high (1<jats:inline-formula><mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"><mml:mo>×</mml:mo></mml:math></jats:inline-formula>10<jats:sup>9</jats:sup> cps/mm<jats:sup>2</jats:sup>) photon count rates for different values of the retrigger time. The quality of the resulting images generally degrades when increasing the photon rates (pileup artifacts) and, at the same time, it becomes strongly dependent on the retrigger time. We show how, even at high incoming rates, it is possible to identify for each energy threshold a retrigger time value that restores almost completely the image quality obtained in the low count-rate scenario. The analysis indicates that the higher the energy threshold, the longer the retrigger time has to be set.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"15 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transition metal dichalcogenides: magneto-polarons and resonant Raman scattering","authors":"C. Trallero-Giner, D. G. Santiago-Pérez, D. V. Tkachenko, G. E. Marques, V. M. Fomin","doi":"10.3389/fphy.2024.1440069","DOIUrl":"https://doi.org/10.3389/fphy.2024.1440069","url":null,"abstract":"Topological two-dimensional transition metal dichalcogenides (TMDs) have a wide range of promising applications and are the subject of intense basic scientific research. Due to the existence of a direct optical bandgap, nano-optics and nano-optoelectronics employing monolayer TMDs are at the center of the development of next-generation devices. Magneto-resonant Raman scattering (MRRS) is a non-destructive fundamental technique that enables the study of magneto-electronic levels for TMD semiconductor device applications and hitherto unexplored optical transitions. Raman intensity in a Faraday backscattering configuration as a function of the magnetic field <jats:italic>B</jats:italic>, laser energy, and the circular polarization of light reveals a set of incoming and outgoing resonances with particular spin orientations and magneto-optical interband transitions at the <jats:inline-formula><mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"><mml:mi>K</mml:mi></mml:math></jats:inline-formula>- and <jats:inline-formula><mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"><mml:msup><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mo>′</mml:mo></mml:mrow></mml:msup></mml:math></jats:inline-formula>-valleys of the Brillouin zone. This fact unequivocally allows for a straightforward determination of the important band parameters of TMD materials. A generalization of the MRRS theory is performed for the description of the magneto-polaron (MP) effects in the first-order light scattering process. It shows how strongly the simultaneous presence of the conduction and valence bands modifies the MP energy spectrum. The resonant MP Raman intensity reveals three resonant splitting processes of double avoided-crossing levels reflecting the electron-hole pair energy spectrum. The scattering profile allows for quantifying the relative contribution of the conduction and valence bands in the formation of MPs. Many avoided-crossing points due to the electron–phonon interaction in the MP spectrum, a superposition of the electron and hole states in the excitation branches, and their impact on Raman scattering are exceptional features of monolayer TMDs. Based on this, the reported theoretical studies open a pathway toward MRRS and resonant MP Raman scattering characterization of two-dimensional materials.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"3 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142219687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}