Frontiers in Physics最新文献_第2页

Manipulation of magnetization and spin transport in hydrogenated graphene with THz pulses 太赫兹脉冲对氢化石墨烯磁化和自旋输运的操纵

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-23 DOI: 10.3389/fphy.2023.1237383

Jakob Kjaerulff Svaneborg, Aleksander Bach Lorentzen, F. Gao, A. Jauho, M. Brandbyge

{"title":"Manipulation of magnetization and spin transport in hydrogenated graphene with THz pulses","authors":"Jakob Kjaerulff Svaneborg, Aleksander Bach Lorentzen, F. Gao, A. Jauho, M. Brandbyge","doi":"10.3389/fphy.2023.1237383","DOIUrl":"https://doi.org/10.3389/fphy.2023.1237383","url":null,"abstract":"Terahertz (THz) field pulses can now be applied in scanning tunneling microscopy (THz-STM) junction experiments to study time-resolved dynamics. The relatively slow pulse compared to the typical electronic time-scale calls for approximations based on a time-scale separation. Here, we contrast three methods based on non-equilibrium Green’s functions: i) the steady-state, adiabatic results, ii) the lowest-order dynamic expansion in the time variation, and iii) the auxiliary mode propagation method without approximations in the time variation. We consider a concrete THz-STM junction setup involving a hydrogen adsorbate on graphene where the localized spin polarization can be manipulated on/off by a local field from the tip electrode and/or a back-gate affecting the in-plane transport. We use steady-state non-equilibrium Green’s function theory combined with density functional theory to obtain a Hubbard model for the study of the junction dynamics. Solving the Hubbard model in a mean-field approximation, we find that the near-adiabatic first-order dynamic expansion in the time variation provides a good description for STM voltage pulses up to the 1 V range.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"349 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82588344","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}

引用次数: 0

A neural state-space-based model predictive technique for effective vibration control in nano-beams 基于神经网络状态空间的纳米梁振动有效控制模型预测技术

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-23 DOI: 10.3389/fphy.2023.1253642

Hajid Alsubaie

{"title":"A neural state-space-based model predictive technique for effective vibration control in nano-beams","authors":"Hajid Alsubaie","doi":"10.3389/fphy.2023.1253642","DOIUrl":"https://doi.org/10.3389/fphy.2023.1253642","url":null,"abstract":"Model predictive control (MPC) is a cutting-edge control technique, but its susceptibility to inaccuracies in the model remains a challenge for embedded systems. In this study, we propose a data-driven MPC framework to address this issue and achieve robust and adaptable performance. Our framework involves systematically identifying system dynamics and learning the MPC policy through function approximations. Specifically, we introduce a system identification method based on the Deep neural network (DNN) and integrate it with MPC. The function approximation capability of DNN enables the controller to learn the nonlinear dynamics of the system then the MPC policy is established based on the identified model. Also, through an added control term the robustness and convergence of the closed-loop system are guaranteed. Then the governing equation of a non-local strain gradient (NSG) nano-beam is presented. Finally, the proposed control scheme is used for vibration suppression in the NSG nano-beam. To validate the effectiveness of our approach, the controller is applied to the unknown system, meaning that solely during the training phase of the neural state-space-based model we relied on the data extracted from the time history of the beam’s deflection. The simulation results conclusively demonstrate the remarkable performance of our proposed approach in effectively suppressing vibrations.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"13 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84313589","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}

引用次数: 0

Editorial: Recent developments in Si-based materials and devices 编辑:硅基材料和器件的最新发展

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-22 DOI: 10.3389/fphy.2023.1272399

Chandrasekar Perumalveeramalai, Chuanbo Li, Jun Zheng

引用次数: 0

LIBS at high duty-cycles: effect of repetition rate and temporal width on the excitation laser pulses 高占空比LIBS:重复频率和时间宽度对激发激光脉冲的影响

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-22 DOI: 10.3389/fphy.2023.1241533

J. Riedel, Josefin Hufgard, Y. You

{"title":"LIBS at high duty-cycles: effect of repetition rate and temporal width on the excitation laser pulses","authors":"J. Riedel, Josefin Hufgard, Y. You","doi":"10.3389/fphy.2023.1241533","DOIUrl":"https://doi.org/10.3389/fphy.2023.1241533","url":null,"abstract":"Laser-induced breakdown spectroscopy (LIBS) is becoming a more mature technology every year with new variants such as laser ablation molecular isotopic spectrometry, reheating by various discharge techniques, and multiple pulse excitation schemes, in which sometimes lasers of different pulse lengths are used. However, lasers with inherent parameters like pulse length and repetition rate are still almost exclusively employed. Recent years have witnessed the advent of novel high-repetition-rate laser concepts for machining processes, like welding, milling, and engraving. Here, a comprehensive study of single-pulse LIBS spectra of a single aluminum target is presented to showcase the applicability of flexible high duty-cycle master oscillator power amplifier (MOPA) lasers. Although traditional flashlamp-pumped Fabry–Pérot lasers only permit a variation in the pulse energy and are operated at very low duty-cycles, MOPA lasers add repetition rate and pulse length as variable parameters. A thorough analysis of the temporal plasma behavior revealed the emission dynamic to closely match the excitation laser pulse pattern. An aluminum sample’s spectral response was shown to be significantly impacted by variations in both rate and length. Although the spectral emission strength of the elemental lines of Al, Sr, and Ca all peaked at slightly different parameter settings, the strongest impact was found on the relative abundance of molecular AlO bands. Unlike in previous laser ablation molecular isotopic spectrometry (LAMIS) publications, the latter could be readily detected with a good intensity and well-resolved spectral features without any temporal gating of the detector. This finding, together with the fact that MOPA lasers are both inexpensive and dependable, makes for a promising combination for future studies including the detection of diatomic band structures.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"105 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82236023","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}

引用次数: 0

Topological data analysis of Chinese stocks’ dynamic correlations under major public events 重大公共事件下中国股票动态相关性的拓扑数据分析

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-22 DOI: 10.3389/fphy.2023.1253953

Hongfeng Guo, Ziwei Ming, Bing Xing

{"title":"Topological data analysis of Chinese stocks’ dynamic correlations under major public events","authors":"Hongfeng Guo, Ziwei Ming, Bing Xing","doi":"10.3389/fphy.2023.1253953","DOIUrl":"https://doi.org/10.3389/fphy.2023.1253953","url":null,"abstract":"Topological data analysis has been acknowledged as one of the most successful mathematical data analytic methodologies in many fields. Additionally, it has also been gradually applied in financial time series analysis and proved effective in exploring the topological features of such data. We select 100 stocks from China’s markets and construct point cloud data for topological data analysis. We detect critical dates from the Lp-norms of the persistence landscapes. Our results reveal the dates are highly consistent with the transition time of some major events in the sample period. We compare the correlations and statistical properties of stocks before and during the events via complex networks to describe the markets’ situation. The strength and variation of links among stocks are clearly different during the major events. We also investigate the neighborhood features of stocks from topological perspectives. This helps identify the important stocks and explore their situations under each event. Finally, we cluster the stocks based on the neighborhood features, which exhibit the heterogeneity impact on stocks of the different events. Our work demonstrates that topological data analysis has strong applicability in the dynamic correlations of stocks.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"28 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81572679","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}

引用次数: 0

A review of the shear rheology of carbon black suspensions 炭黑悬浮液的剪切流变学研究进展

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-17 DOI: 10.3389/fphy.2023.1245847

Jeffrey J Richards, Paolo Z Ramos, Qingsong Liu

引用次数: 0

Biplanar quadrature coil for versatile low-field extremity MRI 双平面正交线圈用于多功能低场肢体MRI

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-17 DOI: 10.3389/fphy.2023.987197

M. Yushchenko, P. Choquet, N. Salameh, M. Sarracanie

{"title":"Biplanar quadrature coil for versatile low-field extremity MRI","authors":"M. Yushchenko, P. Choquet, N. Salameh, M. Sarracanie","doi":"10.3389/fphy.2023.987197","DOIUrl":"https://doi.org/10.3389/fphy.2023.987197","url":null,"abstract":"Biplanar magnets offer extended flexibility in MRI, particularly appealing due to unmatched accessibility to the patient. At low field strength (<0.2 T), such geometries could be particularly suitable for interventional settings or purpose-built applications such as musculoskeletal imaging. In the proposed work, we present a dual-channel, biplanar coil array for low-field MRI featuring almost fully open access when sited in a biplanar magnet. The proposed detector relies on the assembly of two orthogonal biplanar coils (single transmit channel, two receive channels in quadrature) respectively interfaced with custom inductive couplers. Simulations of the B1 field in each element were performed before the quadrature coil was built and used at ∼ 0.1 T (4.33 MHz). Once assembled, the best performance in our setup was achieved in undermatched conditions in place of conventional 50-Ω matching. Phantom images display the extended coverage of the quadrature coil, with similar SNR from each individual biplanar coil. The combined images show an expected SNR gain of 2 that confirms good decoupling between the two channels (−36 dB). To the best of our knowledge, the proposed coil represents the first implementation of a biplanar geometry at low field and the first quadrature detection for a biplanar design. The open design and overall good sensitivity of our biplanar design enabled fast and quasi-isotropic 3D imaging with (1.6 × 1.6 × 2.2) mm3 resolution in vivo in human extremities.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"55 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73579374","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}

引用次数: 0

Tunable narrowband and broadband coexisting absorber enabled by a simple all-metal grating for sensing applications 可调谐窄带和宽带共存吸收器，由一个简单的全金属光栅实现，用于传感应用

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-16 DOI: 10.3389/fphy.2023.1234275

Jianwei Wang, Ze Zhang, Z. Lin, Hanting Li, Huan Gao, Z. Fan, Haifeng Liu

{"title":"Tunable narrowband and broadband coexisting absorber enabled by a simple all-metal grating for sensing applications","authors":"Jianwei Wang, Ze Zhang, Z. Lin, Hanting Li, Huan Gao, Z. Fan, Haifeng Liu","doi":"10.3389/fphy.2023.1234275","DOIUrl":"https://doi.org/10.3389/fphy.2023.1234275","url":null,"abstract":"We realize a tunable narrowband and broadband coexisting absorber based on a simple step-shaped all-metal grating structure. The absorber presents an ultra-narrow absorption band of 1.5 nm and a relatively broad absorption band of 29.8 nm, both with nearly 100% absorption in the infrared region. The mechanism underlying the dual-band perfect absorption is the interaction between two diffraction coupled surface plasmon polariton (SPP) modes with one of them modulated by a cavity resonance. Influences of structure parameters on the absorption performance are numerically investigated. It is found that the positions of the two perfect absorption peaks can be easily tuned both independently and together by changing the structural parameters. In addition, the designed grating structure presents excellent sensing performance with sensitivity and figure of merit as high as 2,514 nm/RIU and 1,600 RIU−1, respectively. The excellent sensing performance, flexible tenability and simple structure design endow this grating absorber with great potential in high-precision biochemical sensing applications.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"16 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84152041","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}

引用次数: 0

Editorial: Uncertainty quantification in nuclear physics 社论:核物理中的不确定性量化

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-15 DOI: 10.3389/fphy.2023.1270577

M. Piarulli, E. Epelbaum, C. Forssén

引用次数: 0

2.79-μm high peak power LiNbO3 acousto-optic Q-switched Er,Cr:YSGG laser with thermal lensing effect compensation 具有热透镜效应补偿的2.79 μm峰值功率LiNbO3声光调q Er,Cr:YSGG激光器

IF 3.1 3区物理与天体物理

Frontiers in Physics Pub Date : 2023-08-15 DOI: 10.3389/fphy.2023.1201822

Lingling Jiang, Zhongchao Wu, Shengjie Ma, Yongbin Zhu, Tingqing Cheng, Hai-he Jiang

{"title":"2.79-μm high peak power LiNbO3 acousto-optic Q-switched Er,Cr:YSGG laser with thermal lensing effect compensation","authors":"Lingling Jiang, Zhongchao Wu, Shengjie Ma, Yongbin Zhu, Tingqing Cheng, Hai-he Jiang","doi":"10.3389/fphy.2023.1201822","DOIUrl":"https://doi.org/10.3389/fphy.2023.1201822","url":null,"abstract":"A new type of lithium niobate (LiNbO3) acousto-optic Q-switched Er,Cr:YSGG laser with high peak power was designed and the thermal lensing effect compensation was studied. The values of thermal focal length in the gain medium were calculated theoretically and measured experimentally. The experimental results validate the designed plane-convex resonator validity, and the output performance of the 2.79 μm Er,Cr:YSGG laser was obviously improved. When the laser operated at free running region, the maximum values of pulse energy was 160 mJ at 60 Hz, compared with the plane-parallel resonator, the pulse energy was increased by 2 times in the plane-convex resonator. When the LiNbO3 Q-switched laser operated at 60 Hz, the maximum values of pulse energy was 8.5 mJ, and the minimum values of pulse duration was 60.8 ns, and the corresponding peak power approximately was 140 kW, respectively. Compared with the plane-parallel resonator, the pulse energy was increased by 1.6 times in the plane-convex resonator, the corresponding peak power was increased by 2.3 times.","PeriodicalId":12507,"journal":{"name":"Frontiers in Physics","volume":"10 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77819051","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}

引用次数: 0