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  • Accounting for Underreporting in Mathematical Modeling of Transmission and Control of COVID-19 in Iran
    Front. Phys. (IF 2.638) Pub Date : 2020-06-26
    Meead Saberi; Homayoun Hamedmoghadam; Kaveh Madani; Helen M. Dolk; Andrei S. Morgan; Joan K. Morris; Kaveh Khoshnood; Babak Khoshnood

    Iran has been the country most affected by the outbreak of SARS-CoV-2 in the Middle East. With a relatively high case fatality ratio and limited testing capacity, the number of confirmed cases reported is suspected to suffer from significant underreporting. Therefore, understanding the transmission dynamics of COVID-19 and assessing the effectiveness of the interventions that have taken place in Iran

    更新日期:2020-07-10
  • First Phantom-Based Quantitative Assessment of Scandium-44 Using a Commercial PET Device
    Front. Phys. (IF 2.638) Pub Date : 2020-06-03
    Thiago V. M. Lima; Silvano Gnesin; Egbert Nitzsche; Pablo G. Ortega; Cristina Müller; Nicholas P. van der Meulen

    Scandium (Sc) is a promising candidate for theranostic applications due to the existence of radioisotopes suitable for both imaging and therapy. A “proof-of-concept” study regarding first-in-human use of 44Sc for imaging metastatic neuroendocrine tumors was reported recently, however, quantitative assessment of 44Sc-based PET images was not performed. The aim of this study was to evaluate quantitative

    更新日期:2020-07-10
  • A Relation Between Moore-Penrose Inverses of Hermitian Matrices and Its Application in Electrical Networks
    Front. Phys. (IF 2.638) Pub Date : 2020-06-02
    Yujun Yang; Dayong Wang; Douglas J. Klein

    A novel relation between the Moore-Penrose inverses of two nullity-1 n × n Hermitian matrices which share a common null eigenvector is established, and its application in electrical networks is illustrated by applying the result to Laplacian matrices of graphs.

    更新日期:2020-07-10
  • Beyond the Formulations of the Fluctuation Dissipation Theorem Given by Callen and Welton (1951) and Expanded by Kubo (1966)
    Front. Phys. (IF 2.638) Pub Date : 2020-06-02
    Lino Reggiani; Eleonora Alfinito

    The quantum formula of the fluctuation dissipation theorem (FDT) was given by Callen and Welton in 1951 [1] for the case of conductors, and then expanded by Kubo in 1966 [2, 3]. The drawback of these quantum relations concerns with the appearance of a zero-point contribution, hω/2 with h the reduced Planck constant and ω the angular frequency of the considered photon, which implies a divergence of

    更新日期:2020-07-10
  • Renormalization in Quantum Theories of Geometry
    Front. Phys. (IF 2.638) Pub Date : 2020-06-04
    Jan Ambjorn; Jakub Gizbert-Studnicki; Andrzej Görlich; Jerzy Jurkiewicz; Renate Loll

    A hallmark of non-perturbative theories of quantum gravity is the absence of a fixed background geometry, and therefore the absence in a Planckian regime of any notion of length or scale that is defined a priori. This has potentially far-reaching consequences for the application of renormalization group methods à la Wilson, which rely on these notions in a crucial way. We review the status quo of attempts

    更新日期:2020-07-09
  • Different Types of Progressive Wave Solutions via the 2D-Chiral Nonlinear Schrödinger Equation
    Front. Phys. (IF 2.638) Pub Date : 2020-05-20
    M. S. Osman; Dumitru Baleanu; Kalim Ul-Haq Tariq; Melike Kaplan; Muhammad Younis; Syed Tahir Raza Rizvi

    A versatile integration tool, namely the protracted (or extended) Fan sub-equation (PFS-E) technique, is devoted to retrieving a variety of solutions for different models in many fields of the sciences. This essay presents the dynamics of progressive wave solutions via the 2D-chiral nonlinear Schrödinger (2D-CNLS) equation. The solutions acquired comprise dark optical solitons, periodic solitons, singular

    更新日期:2020-07-07
  • Time Scales of Fickian Diffusion and the Lifetime of Dynamic Heterogeneity
    Front. Phys. (IF 2.638) Pub Date : 2020-05-18
    Rajsekhar Das; Chandan Dasgupta; Smarajit Karmakar

    Dynamic heterogeneity, believed to be one of the hallmarks of the dynamics of supercooled liquids, is expected to affect the diffusion of the particles comprising the liquid. We have carried out extensive molecular dynamics simulations of two model glass forming liquids in three dimensions to study the time scales at which Fick's law of diffusion starts to set in. We have identified two different Fickian

    更新日期:2020-07-07
  • Gaussian Doubling Times and Reproduction Factors of the COVID-19 Pandemic Disease
    Front. Phys. (IF 2.638) Pub Date : 2020-06-22
    Martin Kröger; Reinhard Schlickeiser

    The Gauss model for the time evolution of the first corona pandemic wave is rendered useful in the estimation of peak times, amount of required equipment, and the forecasting of fade out times. At the same time, it is probably the simplest analytically tractable model that allows us to quantitatively forecast the time evolution of infections and fatalities during a pandemic wave. In light of the various

    更新日期:2020-07-03
  • The Time-Dependent Generator Coordinate Method in Nuclear Physics
    Front. Phys. (IF 2.638) Pub Date : 2020-05-28
    Marc Verriere; David Regnier

    The emergence of collective behaviors and the existence of large amplitude motions are both central features in the fields of nuclear structure and reactions. From a theoretical point of view, describing such phenomena requires increasing the complexity of the many-body wavefunction of the system to account for long-range correlations. One of the challenges, when going in this direction, is to keep

    更新日期:2020-07-03
  • On the Possibility of Experimental Detection of the Discreteness of Time
    Front. Phys. (IF 2.638) Pub Date : 2020-05-14
    Marios Christodoulou; Carlo Rovelli

    The Bose-Marletto-Vedral (BMV) experiment tests a quantum gravitational effect predicted by low energy perturbative quantum gravity. It has received attention because it may soon be within observational reach in the lab. We point out that: (i) in relativistic language, the experiment tests an interference effect between proper-time intervals; (ii) the feasibility study by Bose et al. suggests that

    更新日期:2020-07-03
  • GGA and GGA Plus U Study of Half-Metallic Quaternary Heusler Compound CoCrScSn
    Front. Phys. (IF 2.638) Pub Date : 2020-05-28
    Chuankun Zhang; Haiming Huang; Chengrui Wu; Zhanwu Zhu; Zedong He; Guoying Liu

    The structural, mechanical, electronic, magnetic, and half-metallic properties of quaternary Heusler compound CoCrScSn are studied using the GGA and GGA + U method based on first-principles calculations. It is found that Type-I structure of CoCrScSn compound is the most stable, and its ground state is ferromagnetic. At the equilibrium lattice constant, the electronic structures obtained by GGA and

    更新日期:2020-06-30
  • Wideband Absorbing Plasmonic Structures via Profile Optimization Based on Genetic Algorithm
    Front. Phys. (IF 2.638) Pub Date : 2020-05-28
    Ruichao Zhu; Jiafu Wang; Sai Sui; Yueyu Meng; Tianshuo Qiu; Yuxiang Jia; Xiaofeng Wang; Yajuan Han; Mingde Feng; Lin Zheng; Shaobo Qu

    Plasmonic structures that support the spoof surface plasmon polariton (SSPP) mode can be tailored to achieve strong absorption of electromagnetic (EM) waves. In particular, the profile of an absorbing plasmonic structure (APS) plays an important role in realizing its wideband absorption performance. In this paper, we propose a method of optimizing the longitudinal profile of APS based on Genetic Algorithm

    更新日期:2020-06-30
  • Wavelength-Tunable Ultra-Stable Optical Frequency Comb Based on All-Polarization-Maintaining Fiber Laser
    Front. Phys. (IF 2.638) Pub Date : 2020-05-25
    Xin He; Pan Zhang; Yanyan Zhang; Qimeng Lin; Hongyu Guo; Lei Hou; Kaige Wang

    This study details the implementation of a wavelength-tunable ultra-stable optical frequency comb (OFC), which is generated by a passively mode-locked all-polarization-maintaining Erbium (Er)-doped fiber laser based on a non-linear amplifying loop mirror. The center wavelength can be tuned from 950 to 1,080 nm and from 1,650 to 2,080 nm by adjusting the pump's power. Standard deviations of 100 μHz

    更新日期:2020-06-30
  • Solitons and Jacobi Elliptic Function Solutions to the Complex Ginzburg–Landau Equation
    Front. Phys. (IF 2.638) Pub Date : 2020-05-25
    Kamyar Hosseini; Mohammad Mirzazadeh; M. S. Osman; Maysaa Al Qurashi; Dumitru Baleanu

    The complex Ginzburg–Landau (CGL) equation which describes the soliton propagation in the presence of the detuning factor is firstly considered; then its solitons as well as Jacobi elliptic function solutions are obtained systematically using a modified Jacobi elliptic expansion method. In special cases, several dark and bright soliton solutions to the CGL equation are retrieved when the modulus of

    更新日期:2020-06-30
  • Localized Electromagnetic Resonance Enabled THz Photothermoelectric Detection in Graphene
    Front. Phys. (IF 2.638) Pub Date : 2020-05-20
    Meng Chen; Yingxin Wang; Ziran Zhao

    We propose a graphene-based terahertz (THz) photodetector with a microstructure array designed to manipulate the surface electromagnetic modes. Benefiting from the generated localized electromagnetic resonance, a nearly perfect absorption to the incident THz radiation is observed, an asymmetrical temperature distribution is realized along the graphene channel under uniform THz illumination, and thereby

    更新日期:2020-06-30
  • T-EDGE: Temporal WEighted MultiDiGraph Embedding for Ethereum Transaction Network Analysis
    Front. Phys. (IF 2.638) Pub Date : 2020-05-11
    Dan Lin; Jiajing Wu; Qi Yuan; Zibin Zheng

    Recently, graph embedding techniques have been widely used in the analysis of various networks, but most of the existing embedding methods omit the network dynamics and the multiplicity of edges, so it is difficult to accurately describe the detailed characteristics of the transaction networks. Ethereum is a blockchain-based platform supporting smart contracts. The open nature of blockchain makes the

    更新日期:2020-06-30
  • Is Export a Probe for Domestic Production?
    Front. Phys. (IF 2.638) Pub Date : 2020-04-27
    Francesco Saltarelli; Valeria Cimini; Andrea Tacchella; Andrea Zaccaria; Matthieu Cristelli

    Recent works leverage export data to assess country production structure and ultimately country relative competitiveness. These works mostly rely only on the exported part of the total country output for reasons of data availability, homogeneity, and quality. Here we use the World Input-Output Database (WIOD), which offers cross-country harmonized data that accounts both for domestic production and

    更新日期:2020-06-26
  • Entropy-Based Pandemics Forecasting
    Front. Phys. (IF 2.638) Pub Date : 2020-06-19
    Umberto Lucia; Thomas S. Deisboeck; Giulia Grisolia

    A great variety of natural phenomena follows some statistical distributions. In epidemiology, such as for the current COVID 19 outbreak, it is essential to develop reliable predictions of the evolution of an infectious disease. In particular, a statistical projection of the time of maximum diffusion of infected carriers is fundamental in order to prepare healthcare systems and organize a robust public

    更新日期:2020-06-25
  • A New Iterative Method for the Numerical Solution of High-Order Non-linear Fractional Boundary Value Problems
    Front. Phys. (IF 2.638) Pub Date : 2020-05-22
    Amin Jajarmi; Dumitru Baleanu

    The boundary value problems (BVPs) have attracted the attention of many scientists from both practical and theoretical points of view, for these problems have remarkable applications in different branches of pure and applied sciences. Due to this important property, this research aims to develop an efficient numerical method for solving a class of non-linear fractional BVPs. The proposed method is

    更新日期:2020-06-25
  • Automated Discovery of Local Rules for Desired Collective-Level Behavior Through Reinforcement Learning
    Front. Phys. (IF 2.638) Pub Date : 2020-05-05
    Tiago Costa; Andres Laan; Francisco J. H. Heras; Gonzalo G. de Polavieja

    Complex global behavior patterns can emerge from very simple local interactions between many agents. However, no local interaction rules have been identified that generate some patterns observed in nature, for example the rotating balls, rotating tornadoes and the full-core rotating mills observed in fish collectives. Here we show that locally interacting agents modeled with a minimal cognitive system

    更新日期:2020-06-25
  • The Dust-to-Gas Ratio, Size Distribution, and Dust Fall-Back Fraction of Comet 67P/Churyumov-Gerasimenko: Inferences From Linking the Optical and Dynamical Properties of the Inner Comae
    Front. Phys. (IF 2.638) Pub Date : 2020-05-26
    Raphael Marschall; Johannes Markkanen; Selina-Barbara Gerig; Olga Pinzón-Rodríguez; Nicolas Thomas; Jong-Shinn Wu

    In this work, we present results that simultaneously constrain the dust size distribution, dust-to-gas ratio, fraction of dust re-deposition, and total mass production rates for comet 67P/Churyumov-Gerasimenko. We use a 3D Direct Simulation Monte Carlo (DSMC) gas dynamics code to simulate the inner gas coma of the comet for the duration of the Rosetta mission. The gas model is constrained by ROSINA/COPS

    更新日期:2020-06-24
  • Microbial Active Matter: A Topological Framework
    Front. Phys. (IF 2.638) Pub Date : 2020-04-28
    Anupam Sengupta

    Topology transcends boundaries that conventionally delineate physical, biological, and engineering sciences. Our ability to mathematically describe topology, combined with recent access to precision tracking and manipulation approaches, has triggered a fresh appreciation of topological ramifications in biological systems. Microbial ecosystems, a classic example of living matter, offer a rich test bed

    更新日期:2020-06-23
  • Metapopulation Network Models for Understanding, Predicting, and Managing the Coronavirus Disease COVID-19
    Front. Phys. (IF 2.638) Pub Date : 2020-06-10
    Daniela Calvetti; Alexander P. Hoover; Johnie Rose; Erkki Somersalo

    Mathematical models of SARS-CoV-2 (the virus which causes COVID-19) spread are used for guiding the design of mitigation steps and helping identify impending breaches of health care system surge capacity. The challenges of having only lacunary information about daily new infections and mortality counts are compounded by geographic heterogeneity of the population. This complicates prediction, particularly

    更新日期:2020-06-19
  • On the Boundary of Incidence Energy and Its Extremum Structure of Tricycle Graphs
    Front. Phys. (IF 2.638) Pub Date : 2020-05-15
    Hongyan Lu; Zhongxun Zhu

    With the wide application of graph theory in circuit layout, signal flow chart and power system, more and more attention has been paid to the network topology analysis method of graph theory. In this paper, we construct a graph transformation which can reflect the monotonicity of coefficients and reduce the number of graphs. A sharp lower bound for incidence energy in the tricyclic graphs is given

    更新日期:2020-06-19
  • Predicting Sites of Epitranscriptome Modifications Using Unsupervised Representation Learning Based on Generative Adversarial Networks
    Front. Phys. (IF 2.638) Pub Date : 2020-05-01
    Sirajul Salekin; Milad Mostavi; Yu-Chiao Chiu; Yidong Chen; Jianqiu Zhang; Yufei Huang

    Epitranscriptome is an exciting area that studies different types of modifications in transcripts, and the prediction of such modification sites from the transcript sequence is of significant interest. However, the scarcity of positive sites for most modifications imposes critical challenges for training robust algorithms. To circumvent this problem, we propose MR-GAN, a generative adversarial network

    更新日期:2020-06-19
  • Advanced Analysis of the Water/Fat Distribution in Skeletal Muscle Tissue Using Magnetic Resonance Imaging in Patients With Neuromuscular Disease
    Front. Phys. (IF 2.638) Pub Date : 2020-05-01
    Christian Nasel; Uros Klickovic; Hakan Cetin; Walter Struhal; Ewald Moser

    Purpose: Neuromuscular diseases (NMDs) frequently cause severe disabilities. Magnetic resonance imaging (MRI)–based calculation of the so-called fat fraction (FF) in affected muscles was recently described as a reliable biomarker for monitoring progression of NMDs. This is of high interest as newly available modern gene therapies, currently subject to intensive investigations, may provide at least

    更新日期:2020-06-19
  • Set-Valued Weighted Value at Risk and Its Computation
    Front. Phys. (IF 2.638) Pub Date : 2020-04-30
    Yichuan Dong; Yijun Hu; Yu Feng

    In this paper, we propose a new class of set-valued coherent risk measures called the set-valued weighted value at risk. Firstly, the “regulator” version is independent of other market scenarios. The second version, which is called the market extension, is related to different market scenarios. The proofs of the properties of both versions are given, and equivalent representations are provided that

    更新日期:2020-06-19
  • Predicting COVID-19 Peaks Around the World
    Front. Phys. (IF 2.638) Pub Date : 2020-05-20
    Constantino Tsallis; Ugur Tirnakli

    The official data for the time evolution of active cases of COVID-19 pandemics around the world are available online. For all countries, a peak has been either observed (China and South Korea) or is expected in the near future. The approximate dates and heights of those peaks have important epidemiological implications. Inspired by similar complex behavior of volumes of transactions of stocks at the

    更新日期:2020-05-20
  • A Logistic Model for Counting Crowds and Flowing Particles
    Front. Phys. (IF 2.638) Pub Date : 2020-05-18
    Byung Mook Weon

    Counting how many people or particles pass through a specific space within a specific time is an interesting question in applied physics and social science. Here a logistic model is developed to estimate the total number of moving crowds or flowing particles. This model sheds light on a collective contribution of crowd or particle growth rate and transient probability within a specific space. This

    更新日期:2020-05-18
  • Effective Transfer Entropy Approach to Information Flow Among EPU, Investor Sentiment and Stock Market
    Front. Phys. (IF 2.638) Pub Date : 2020-05-13
    Can-Zhong Yao; Hong-Yu Li

    In contrast to the traditional view that economic policy affects investor sentiment and eventually causes stock price fluctuations, we reveal that investor sentiment is a reflection of both economic policy and stock market information. This article first proposes an improved ETE method with a sliding window. We verify that this new method can capture the dynamic orders effectively by validating this

    更新日期:2020-05-13
  • High Temperature Treatment of Diamond Particles Toward Enhancement of Their Quantum Properties
    Front. Phys. (IF 2.638) Pub Date : 2020-05-11
    Marco D. Torelli; Nicholas A. Nunn; Zachary R. Jones; Thea Vedelaar; Sandeep Kumar Padamati; Romana Schirhagl; Robert J. Hamers; Alexander I. Shames; Evgeny O. Danilov; Alexander Zaitsev; Olga A. Shenderova

    Fluorescence of the negatively charged nitrogen-vacancy (NV−) center of diamond is sensitive to external electromagnetic fields, lattice strain, and temperature due to the unique triplet configuration of its spin states. Their use in particulate diamond allows for the possibility of localized sensing and magnetic-contrast-based differential imaging in complex environments with high fluorescent background

    更新日期:2020-05-11
  • Classification of Cancer Types Using Graph Convolutional Neural Networks
    Front. Phys. (IF 2.638) Pub Date : 2020-05-08
    Ricardo Ramirez; Yu-Chiao Chiu; Allen Hererra; Milad Mostavi; Joshua Ramirez; Yidong Chen; Yufei Huang; Yu-Fang Jin

    Background: Cancer has been a leading cause of death in the United States with significant health care costs. Accurate prediction of cancers at an early stage and understanding the genomic mechanisms that drive cancer development are vital to the improvement of treatment outcomes and survival rates, thus resulting in significant social and economic impacts. Attempts have been made to classify cancer

    更新日期:2020-05-08
  • Thermodynamic Integration in 3n Dimensions without Biases or Alchemy for Protein Interactions.
    Front. Phys. (IF 2.638) Pub Date : 2020-05-06
    Liao Y Chen

    Thermodynamic integration (TI), a powerful formalism for computing Gibbs free energy, has been implemented for many biophysical processes with alchemical schemes that require delicate human efforts to choose/design biasing potentials for sampling the desired biophysical events and to remove their artifactitious consequences afterwards. Theoretically, an alchemical scheme is exact but practically, an

    更新日期:2020-05-06
  • Temporal stability of lipid-shelled microbubbles during acoustically-mediated blood-brain barrier opening.
    Front. Phys. (IF 2.638) Pub Date : 2020-05-06
    Antonios N Pouliopoulos,Daniella A Jimenez,Alexander Frank,Alexander Robertson,Lin Zhang,Alina R Kline-Schoder,Vividha Bhaskar,Mitra Harpale,Elizabeth Caso,Nicholas Papapanou,Rachel Anderson,Rachel Li,Elisa E Konofagou

    Non-invasive blood-brain barrier (BBB) opening using focused ultrasound (FUS) is being tested as a means to locally deliver drugs into the brain. Such FUS therapies require injection of preformed microbubbles, currently used as contrast agents in ultrasound imaging. Although their behavior during exposure to imaging sequences has been well described, our understanding of microbubble stability within

    更新日期:2020-05-06
  • Numerical Treatment for 3D Squeezed Flow in a Rotating Channel With Soret and Dufour Effects
    Front. Phys. (IF 2.638) Pub Date : 2020-05-05
    Abdullah K. Alzahrani; Malik Zaka Ullah; Taseer Muhammad

    This article examines magnetohydrodynamic three-dimensional (3D) squeezed flow by a rotating permeable channel subject to Dufour and Soret impacts. Impact of viscous dissipation is also considered. An applied magnetic field is considered subject to electrically conducting viscous fluid. The change from the non-linear partial differential framework to the non-linear ordinary differential framework is

    更新日期:2020-05-05
  • Generalization of the Cover Pebbling Number for Networks
    Front. Phys. (IF 2.638) Pub Date : 2020-05-04
    Zheng-Jiang Xia; Zhen-Mu Hong

    Pebbling can be viewed as a model of resource transportation for networks. We use a graph to denote the network. A pebbling move on a graph consists of the removal of two pebbles from a vertex and the placement of one pebble on an adjacent vertex. The t-pebbling number of a graph G is the minimum number of pebbles so that we can move t pebbles on each vertex of G regardless of the original distribution

    更新日期:2020-05-04
  • Research on Dynamic Evolution of Systemic Risk in Chinese Banking System
    Front. Phys. (IF 2.638) Pub Date : 2020-05-04
    Hong Fan; Wanqin Sheng

    Systemic risk is not only related to the contagious risk of interbank market risk exposure, but also to the credit risk exposure. At the same time, the dynamic characteristics of banking system also affect the systemic risk. A large number of studies have revealed the contagious risk of interbank market risk exposure, but the systematic risk research that considers these factors at the same time is

    更新日期:2020-05-04
  • Orbital Angular Momentum Optical Amplifier Based on PbS-Doped Ring-Core Fiber
    Front. Phys. (IF 2.638) Pub Date : 2020-05-04
    Lingmin Xu; Yana Shang; Jinhong Yang; Zhenyi Chen; Fufei Pang; Huanhuan Liu; Yanhua Dong; Na Chen; Jianxiang Wen; Tingyun Wang

    A unique orbital angular momentum (OAM) optical amplifier based on a ring-core fiber doped with lead sulfide (PbS) is realized for the first time in this study. The PbS-doped ring-core fiber is fabricated using the modified chemical vapor deposition method. The cross-sectional microscope image of the fiber is obtained. The difference in the refractive index between the ring core and the fiber cladding

    更新日期:2020-05-04
  • Improving the Sensitivity of Surface-Enhanced Laser-Induced Breakdown Spectroscopy by Repeating Sample Preparation
    Front. Phys. (IF 2.638) Pub Date : 2020-04-30
    Xinyan Yang; Xiangyou Li; Zhifeng Cui; Guanxin Yao; Zhengxian Zhou; Kuanguo Li

    To further improve the detection sensitivity of surface-enhanced laser-induced breakdown spectroscopy (SENLIBS), the number of repeating sample preparations in a fixed area was increased. The trace elements in an aqueous solution were quantitatively analyzed successfully. The results showed that the spectral intensities were strengthened. The limit of detection (LoD) values of Cu, Pb, Cr, and Cd were

    更新日期:2020-04-30
  • Some Effective Numerical Techniques for Chaotic Systems Involving Fractal-Fractional Derivatives With Different Laws
    Front. Phys. (IF 2.638) Pub Date : 2020-04-30
    Behzad Ghanbari; Kottakkaran Sooppy Nisar

    Chaotic systems are dynamical systems that are highly sensitive to initial conditions. Such systems are used to model many real-world phenomena in science and engineering. The main purpose of this paper is to present several efficient numerical treatments for chaotic systems involving fractal-fractional operators. Several numerical examples test the performance of the proposed methods. Simulations

    更新日期:2020-04-30
  • Perturbation Theory for Time-Dependent Quantum Systems Involving Complex Potentials
    Front. Phys. (IF 2.638) Pub Date : 2020-04-30
    Jeong Ryeol Choi

    We explore how to apply perturbation theory to complicated time-dependent Hamiltonian systems that involve complex potentials. To do this, we introduce a generalized time-dependent oscillator to which the complex potentials are connected through a weak coupling strength. We regard the complex potentials in the Hamiltonian as the perturbed terms. Quantum characteristics of the system, such as wave functions

    更新日期:2020-04-30
  • Design of an Open Electrowetting on Dielectric Device Based on Printed Circuit Board by Using a Parafilm M
    Front. Phys. (IF 2.638) Pub Date : 2020-04-30
    Zichuan Yi; Haoqiang Feng; Xiaofeng Zhou; Lingling Shui

    In recent years, the open electrowetting on dielectric (EWOD) device has been widely used in biomedical detection, chemical synthesis analysis, and so on. However, the cost of using ITO glass as surface material is difficult to meet the requirement for large-scale array chip production. So, a low-cost, easy-to-manufacture open EWOD platform is designed in this paper. In hardware platform, an operation

    更新日期:2020-04-30
  • Local Realistic Interpretation of Entangled Photon Pairs in the Weyl-Wigner Formalism
    Front. Phys. (IF 2.638) Pub Date : 2020-04-30
    Emilio Santos

    A polarization correlation experiment with two maximally entangled photons created by spontaneous parametric down-conversion is studied in the Weyl-Wigner formalism, that reproduces the quantum predictions. A realistic stochastic interpretation is proposed suggesting that an analysis of the experiments more detailed than the Bell approach may be compatible with local realism. Entanglement appears as

    更新日期:2020-04-30
  • On Characterizing the Quantum Geometry Underlying Asymptotic Safety
    Front. Phys. (IF 2.638) Pub Date : 2020-04-29
    Aleksandr Kurov; Frank Saueressig

    The asymptotic safety program builds on a high-energy completion of gravity based on the Reuter fixed point, a non-trivial fixed point of the gravitational renormalization group flow. At this fixed point the canonical mass-dimension of coupling constants is balanced by anomalous dimensions induced by quantum fluctuations such that the theory enjoys quantum scale invariance in the ultraviolet. The crucial

    更新日期:2020-04-29
  • From Renormalization Group Flows to Cosmology
    Front. Phys. (IF 2.638) Pub Date : 2020-04-29
    Alessia Platania

    According to the asymptotic-safety conjecture, the gravitational renormalization group flow features an ultraviolet-attractive fixed point that makes the theory renormalizable and ultraviolet complete. The existence of this fixed point entails an antiscreening of the gravitational interaction at short distances. In this paper we review the state-of-the-art of phenomenology of Asymptotically Safe Gravity

    更新日期:2020-04-29
  • A Variety of Novel Exact Solutions for Different Models With the Conformable Derivative in Shallow Water
    Front. Phys. (IF 2.638) Pub Date : 2020-04-27
    Dipankar Kumar; Melike Kaplan; Md. Rabiul Haque; M. S. Osman; Dumitru Baleanu

    For different nonlinear time-conformable derivative models, a versatile built-in gadget, namely the generalized exp(−φ(ξ))-expansion (GEE) method, is devoted to retrieving different categories of new explicit solutions. These models include the time-fractional approximate long-wave equations, the time-fractional variant-Boussinesq equations, and the time-fractional Wu-Zhang system of equations. The

    更新日期:2020-04-27
  • Technical Aspects of in vivo Small Animal CMR Imaging
    Front. Phys. (IF 2.638) Pub Date : 2020-04-27
    Hao Li; Alireza Abaei; Patrick Metze; Steffen Just; Qinghua Lu; Volker Rasche

    Cardiovascular magnetic resonance (CMR) imaging has become an accurate and versatile imaging modality to visualize the cardiovascular system in normal or abnormal conditions. In preclinical research, small rodent animal models of human cardiovascular diseases are frequently used to investigate the basic underlying mechanism of normal and abnormal cardiac function and for monitoring the disease progression

    更新日期:2020-04-27
  • Novel Microstructural Features on Heat and Mass Transfer in Peristaltic Flow Through a Curved Channel
    Front. Phys. (IF 2.638) Pub Date : 2020-04-27
    Raheel Ahmed; Nasir Ali; Sami Ullah Khan; A. M. Rashad; Hossam A. Nabwey; Iskander Tlili

    Recently, significant interest has been developed by researchers toward the peristaltic transport of fluid, as this phenomenon involves a variety of applications in the biomechanics, bioengineering, and biomedical industries. In the present contribution, we investigate the effect of heat and mass transfer on magnetically influenced micropolar flow induced by peristaltic waves. The fundamental laws

    更新日期:2020-04-27
  • Neural Network Backstepping Controller Design for Uncertain Permanent Magnet Synchronous Motor Drive Chaotic Systems via Command Filter
    Front. Phys. (IF 2.638) Pub Date : 2020-04-27
    Ricai Luo; Yanping Deng; Yuling Xie

    In this study, an adaptive neural network (NN) command filtered control (CFC) method is proposed for a permanent magnet synchronous motor (PMSM) system with system uncertainties and external disturbance by means of a backstepping technique. At every backstepping step, a novel command filter is proposed, and the complicated virtual input and its derivative together can be approximated by this filter

    更新日期:2020-04-27
  • New Soliton Applications in Earth's Magnetotail Plasma at Critical Densities
    Front. Phys. (IF 2.638) Pub Date : 2020-04-27
    Hesham G. Abdelwahed; Mahmoud A. E. Abdelrahman; Mustafa Inc; R. Sabry

    New plasma wave solutions of the modified Kadomtsev Petviashvili (MKP) equation are presented. These solutions are written in terms of some elementary functions, including trigonometric, rational, hyperbolic, periodic, and explosive functions. The computational results indicate that these solutions are consistent with the MKP equation, and the numerical solutions indicate that new periodic, shock,

    更新日期:2020-04-27
  • The Dynamic Correlations Between Mass Media News and New Media News in Stock Market
    Front. Phys. (IF 2.638) Pub Date : 2020-04-27
    Zuochao Zhang; Yongjie Zhang; Dehua Shen

    In this paper, we examine the dynamic correlations between mass-media news and new-media news as well as their reprints in the Chinese stock market. We mainly find that: (1) there is a significant positive correlation between the four types of news and the correlation between reprints and their congener media news is stronger; (2) both the mass-media news and new-media news have significant positive

    更新日期:2020-04-27
  • Necessary and Sufficient Conditions for Expressing Quadratic Rational Bézier Curves
    Front. Phys. (IF 2.638) Pub Date : 2020-04-24
    Chaoyu Yang; Jie Yang; Ying Liu; Xianya Geng

    Quadratic rational Bézier curve transformation is widely used in the field of computational geometry. In this paper, we offer several important characteristics of the quadratic rational Bézier curve. More precisely, on the basis of proving its monotonicity, the necessary and sufficient conditions for transforming a quadratic rational Bézier curve into a point, line segment, parabola, elliptic arc,

    更新日期:2020-04-24
  • Recent Progress in Nuclear Lattice Simulations
    Front. Phys. (IF 2.638) Pub Date : 2020-04-24
    Dean Lee

    We review several recent results on lattice simulations by the Nuclear Lattice Effective Field Theory Collaboration. In the first part we discuss the implementation of nuclear forces on the lattice using chiral effective field theory. The new development we highlight is the use of non-local lattice operators to achieve a simpler spin channel decomposition, in contrast with previous studies that considered

    更新日期:2020-04-24
  • On the Testability of the Equivalence Principle as a Gauge Principle Detecting the Gravitational t3 Phase
    Front. Phys. (IF 2.638) Pub Date : 2020-04-24
    Chiara Marletto; Vlatko Vedral

    There have been various claims that the Equivalence Principle, as originally formulated by Einstein, presents several difficulties when extended to the quantum domain, even in the regime of weak gravity. Here we point out that by following the same approach as used for other classical principles, e.g., the principle of conservation of energy, one can, for weak fields, obtain a straightforward quantum

    更新日期:2020-04-24
  • Low-Field MRI: How Low Can We Go? A Fresh View on an Old Debate
    Front. Phys. (IF 2.638) Pub Date : 2020-04-23
    Mathieu Sarracanie; Najat Salameh

    For about 30 years, MRI set cruising speed at 1.5 T of magnetic field, with a gentle transition toward 3 T systems. In its first 10 years of existence, there was an open debate on the question of most relevant MRI field strengths considering the gain in T1 contrast, simpler cooling strategies, lower predisposition to generating image artifacts, and naturally cost reduction of small footprint low field

    更新日期:2020-04-23
  • Polarization Correlation of Entangled Photons Derived Without Using Non-local Interactions
    Front. Phys. (IF 2.638) Pub Date : 2020-04-22
    Kurt Jung

    Entangled photons leaving parametric down-conversion sources exhibit a pronounced polarization correlation. The data violate Bell's inequality thus proving that local realistic theories cannot explain the correlation results. Therefore, many physicists are convinced that the correlation can only be brought about by non-local interactions. Some of them even assume that instantaneous influences at a

    更新日期:2020-04-22
  • A Single-Particle Trigger for Time-of-Flight Measurements in Prompt-Gamma Imaging
    Front. Phys. (IF 2.638) Pub Date : 2020-04-22
    Paulo Magalhaes Martins; Riccardo Dal Bello; Michael Seimetz; German Hermann; Thomas Kihm; Joao Seco

    Tracking of single particles accelerated by synchrotrons is a subject that crosses several physics fields. The high clinical intensities used in particle therapy that can exceed 109 p/s make this task very challenging. The tracking of the arrival time of single particles in the ion beam is fundamental for the verification of the particle range and dose delivered to the patient. We present a prototype

    更新日期:2020-04-22
  • Transport Ratios of the Kinetic Alfvén Mode in Space Plasmas
    Front. Phys. (IF 2.638) Pub Date : 2020-04-21
    Yasuhito Narita; Owen Wyn Roberts; Zoltán Vörös; Masahiro Hoshino

    Fluctuation properties of the kinetic Alfvén mode, such as polarization of the wave electric and magnetic field around the mean magnetic field, parallel fluctuation to the mean field, ratios of the electric to magnetic field, and density fluctuations are analytically estimated by constructing the dielectric tensor of plasma based on the linear Vlasov theory. The dielectric tensor contains various fluid-picture

    更新日期:2020-04-21
  • A New Dynamic Scheme via Fractional Operators on Time Scale
    Front. Phys. (IF 2.638) Pub Date : 2020-04-21
    Saima Rashid; Muhammad Aslam Noor; Kottakkaran Sooppy Nisar; Dumitru Baleanu; Gauhar Rahman

    The present work investigates the applicability and effectiveness of the generalized Riemann-Liouville fractional integral operator integral method to obtain new Minkowski, Grüss type and several other associated dynamic variants on an arbitrary time scale, which are communicated as a combination of delta and fractional integrals. These inequalities extend some dynamic variants on time scales, and

    更新日期:2020-04-21
  • Stock Network Stability After Crashes Based on Entropy Method
    Front. Phys. (IF 2.638) Pub Date : 2020-04-20
    Ming-Yuan Yang; Fei Ren; Sai-Ping Li

    This paper studies the stability of stock networks after crashes based on the entropy method. By measuring network stability using the entropy calculated with the degree distribution, we find that the entropy of a stock network is close to that of the Erdös-Rényi and Watts-Strogatz networks. We further introduce government rescue policies as a natural experiment and use the entropy measurement to study

    更新日期:2020-04-20
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