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  • Naphthalene as a Cubesat Cold Gas Thruster Propellant
    Front. Phys. (IF 2.638) Pub Date : 2020-08-11
    Dimitrios Tsifakis; Christine Charles; Rod Boswell

    The “cubesat” form factor (multiples of 10 × 10 × 10 cm3 volume and 1.33 kg mass) has been adopted as the defacto standard for a cost effective and modular, nano-satellite platform. Many commercial options exist for nearly all components required to build such satellite; however, there is a limited range of thruster options that suit the power and size restrictions of a cubesat. This work presents

    更新日期:2020-09-23
  • Auroral Kilometric Radiation and Electron Pairing
    Front. Phys. (IF 2.638) Pub Date : 2020-08-10
    Rudolf A. Treumann; Wolfgang Baumjohann

    We suggest that pairing of bouncing medium-energy electrons in the auroral upward current region close to the mirror points may play a role in driving the electron cyclotron maser instability to generate an escaping narrow band fine structure in the auroral kilometric radiation. We treat this mechanism in the gyrotron approximation, for simplicity using the extreme case of a weakly relativistic Dirac

    更新日期:2020-09-23
  • New Aspects of ZZ Transform to Fractional Operators With Mittag-Leffler Kernel
    Front. Phys. (IF 2.638) Pub Date : 2020-07-24
    Rajarama Mohan Jena; Snehashish Chakraverty; Dumitru Baleanu; Maysaa M. Alqurashi

    In this paper, we discuss the relationship between the Zain Ul Abadin Zafar (ZZ) transform with Laplace and Aboodh transforms. Further, the ZZ transform is applied to the fractional derivative with the Mittag-Leffler kernel defined in both the Caputo and Riemann-Liouville sense. In order to illustrate the validity and applicability of the transform, we solve some illustrative examples.

    更新日期:2020-09-23
  • Dissolution Phase Diagram in Radial Geometry
    Front. Phys. (IF 2.638) Pub Date : 2020-07-31
    Le Xu; Piotr Szymczak; Renaud Toussaint; Eirik G. Flekkøy; Knut J. Måløy

    Fractures play an important role as flow paths in porous media. When an undersaturated reactive fluid is flowing in a fracture, the dissolution process will alter the flow paths locally. Dissolution patterns grow slowly, but they may lead to a dramatic reorganization of the flow. Here, we study dissolution in a radial geometry, which is relevant for a number of practical applications, e.g., the acidization

    更新日期:2020-09-22
  • High Refractive Index Metamaterial Superstrate for Microstrip Patch Antenna Performance Improvement
    Front. Phys. (IF 2.638) Pub Date : 2020-08-20
    Xi Gao; Yan Zhang; Simin Li

    We propose a high refractive index metamaterial (HRIM)that is composed of two identical patch arrays symmetrically etched on both sides of a dielectric plate. By reducing the gap of adjacent patches and the thickness of dielectric plate, the proposed metamaterial can suppress the diamagnetic response and enhance the capacitance coupling, so that the refractive index of the metamaterial is higher than

    更新日期:2020-09-20
  • Intervention Scenarios to Enhance Knowledge Transfer in a Network of Firms
    Front. Phys. (IF 2.638) Pub Date : 2020-08-07
    Frank Schweitzer; Yan Zhang; Giona Casiraghi

    We investigate a multi-agent model of firms in a Research & Development (R&D) network. Each firm is characterized by its knowledge stock xi(t), which follows a non-linear dynamics. xi(t) grows with the input from other firms, i.e., by knowledge transfer, and decays otherwise. However, maintaining the interactions that increase knowledge stock is costly for all partners involved. Because of this, firms

    更新日期:2020-09-20
  • Exact Values for Some Size Ramsey Numbers of Paths and Cycles
    Front. Phys. (IF 2.638) Pub Date : 2020-07-23
    Xiangmei Li; Asfand Fahad; Xiaoqing Zhou; Hong Yang

    For the graphs G1, G2, and G, if every 2-coloring (red and blue) of the edges of G results in either a copy of blueG1 or a copy of redG2, we write G → (G1, G2). The size Ramsey number R^(G1,G2) is the smallest number e such that there is a graph G with size e satisfying G → (G1, G2), i.e., R^(G1,G2)=min{|E(G)|:G→(G1,G2)}. In this paper, by developing the procedure and algorithm, we determine exact

    更新日期:2020-09-20
  • Stock-Index Tracking Optimization Using Auto-Encoders
    Front. Phys. (IF 2.638) Pub Date : 2020-08-10
    Chi Zhang; Shuang Liang; Fei Lyu; Libing Fang

    Deep learning algorithms' powerful capabilities for extracting useful latent information give them the potential to outperform traditional financial models in solving problems of the stock market which is a complex system. In this paper, we explore the use of advanced deep learning algorithms for stock-index tracking. We partially replicate the CSI 300 Index by optimizing with respect to the difference

    更新日期:2020-09-18
  • Estimating the Serial Interval of the Novel Coronavirus Disease (COVID-19): A Statistical Analysis Using the Public Data in Hong Kong From January 16 to February 15, 2020
    Front. Phys. (IF 2.638) Pub Date : 2020-07-23
    Shi Zhao; Daozhou Gao; Zian Zhuang; Marc K. C. Chong; Yongli Cai; Jinjun Ran; Peihua Cao; Kai Wang; Yijun Lou; Weiming Wang; Lin Yang; Daihai He; Maggie H. Wang

    Background: The emerging virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused a large outbreak of novel coronavirus disease (COVID-19) since the end of 2019. As of February 15, there were 56 COVID-19 cases confirmed in Hong Kong since the first case with symptom onset on January 23, 2020. Methods: Based on the publicly available surveillance data in Hong Kong, we identified

    更新日期:2020-09-18
  • Locality Is Dead! Long Live Locality!
    Front. Phys. (IF 2.638) Pub Date : 2020-07-28
    William Sulis

    Several decades of theory and experiment into EPR correlations have led to the widely held belief that reality is non-local, in spite of the fact that this violates special relativity. To date, no experiment has shown a violation of special relativity, and EPR experiments do not demonstrate the existence of superluminal information exchange, merely correlations which violate certain inequalities. Every

    更新日期:2020-09-15
  • Beam Monitors for Tomorrow: The Challenges of Electron and Photon FLASH RT
    Front. Phys. (IF 2.638) Pub Date : 2020-08-03
    Anna Vignati; Simona Giordanengo; Federico Fausti; Oscar A. Martì Villarreal; Felix Mas Milian; Giovanni Mazza; Zahra Shakarami; Roberto Cirio; Vincenzo Monaco; Roberto Sacchi

    The emergent FLASH RadioTherapy (RT) uses ultrahigh dose-rate irradiation (up to 107 Gy/s instantaneous dose-rate in each μs pulse) to deliver a single high dose of irradiation in a very short time (<200 ms). Pre-clinical studies at ultrahigh dose-rates recently showed an increased ratio between tumoricidal effect and normal tissue toxicity (therapeutic index), compared to conventional RT at standard

    更新日期:2020-09-14
  • Fractional Derivative Modeling on Solute Non-Fickian Transport in a Single Vertical Fracture
    Front. Phys. (IF 2.638) Pub Date : 2020-08-05
    Chuantaidou Qiao; Yi Xu; Weidong Zhao; Jiazhong Qian; Yongting Wu; HongGuang Sun

    Solute transport in a single vertical fracture (SVF) cannot be reliably described by the classical advection-dispersion equation (ADE) model, due to the heterogeneity nature of fracture. This study conducted a group of experiments to investigate chloride ion transport in the SVFs under different rough-walled conditions, and then applied a time fractional advection-dispersion equation (F-ADE) model

    更新日期:2020-09-11
  • Transforming an IORT Linac Into a FLASH Research Machine: Procedure and Dosimetric Characterization
    Front. Phys. (IF 2.638) Pub Date : 2020-07-31
    Giuseppe Felici; Patrizio Barca; Salvatore Barone; Eleonora Bortoli; Rita Borgheresi; Silvia De Stefano; Massimo Di Francesco; Luigi Grasso; Stefania Linsalata; Daniela Marfisi; Matteo Pacitti; Fabio Di Martino

    Since Favaudon's paper of 2014, there has been an increasing interest in FLASH radiotherapy. The FLASH modality could represent a breakthrough in radiation oncology; nevertheless, it brings new scientific and technological challenges. Currently, one of the main limits the scientific community has to cope with is the lack of a common technological platform to experiment with. Considering this framework

    更新日期:2020-09-11
  • Shape Evolutions in Fission Dynamics Within Time-Dependent Hartree-Fock Approach
    Front. Phys. (IF 2.638) Pub Date : 2020-07-24
    Marko Pancic; Yu Qiang; Junchen Pei; Paul Stevenson

    We studied the nuclear shape evolutions in fission process of 240Pu by the time-dependent Hartree-Fock approach with various Skyrme forces. Calculations are performed for the later phase of the fission with large initial deformations toward the scission. We show that calculations with Skyrme forces with large surface energies and large symmetry energies can have extremely long fission evolution time

    更新日期:2020-09-11
  • Large Spectral Shift of Reflected Radiation From Laser Plasmas Generated by High Contrast KrF Laser Pulses
    Front. Phys. (IF 2.638) Pub Date : 2020-07-13
    Zsolt Kovács; Barnabás Gilicze; Sándor Szatmári; István B. Földes

    Increasing absorption up to more than 90% with increasing intensity was observed in boron and gold laser plasmas heated by KrF laser pulses of high, but still non-relativistic, intensity. The pulses of 700 fs duration had a temporal contrast of 12 orders of magnitude; thus, the laser pulse of more than 1018 Wcm−2 intensity hit the steep surface of the boron and gold targets. Blue shift of the reflected

    更新日期:2020-09-11
  • One-Way Pedestrian Traffic Is a Means of Reducing Personal Encounters in Epidemics
    Front. Phys. (IF 2.638) Pub Date : 2020-08-03
    Bernardo A. Mello

    Minimizing social contact is an important tool to reduce the spread of diseases but harms people's well-being. This and other more compelling reasons urge people to walk outside periodically. The present work explores how organizing the traffic of pedestrians affects the number of walking or running people passing by each other. By applying certain rules, this number can be significantly reduced, potentially

    更新日期:2020-09-10
  • Dynamic Adjustment and Distinguishing Method for Vehicle Headlight Based on Data Access of a Thermal Camera
    Front. Phys. (IF 2.638) Pub Date : 2020-07-27
    Shixiao Li; Pengfei Bai; Yuanfeng Qin

    In recent years, more and more traffic accidents have been caused by the illegal use of high beams. Therefore, the distinguishing of the vehicle headlight is vital for night driving and traffic supervision. Then, a method for distinguishing vehicle headlight based on data access of a thermal camera was proposed in this paper. There are two steps in this method. The first step is thermal image dynamic

    更新日期:2020-09-10
  • Research on Improved Chaotic Particle Optimization Algorithm Based on Complex Function
    Front. Phys. (IF 2.638) Pub Date : 2020-07-30
    Xiangli Xia; Shijin Li

    In order to improve the performance of Particle Swarm Optimization (PSO) algorithm in solving continuous function optimization problems, a chaotic particle optimization algorithm for complex functions is proposed. Firstly, the algorithm uses qubit Bloch spherical coordinate coding scheme to initialize the initial position of the population. This coding method can expand the ergodicity of the search

    更新日期:2020-09-10
  • ESERK Methods to Numerically Solve Nonlinear Parabolic PDEs in Complex Geometries: Using Right Triangles
    Front. Phys. (IF 2.638) Pub Date : 2020-07-29
    Jesús Martín-Vaquero

    In this paper Extrapolated Stabilized Explicit Runge-Kutta methods (ESERK) are proposed to solve nonlinear partial differential equations (PDEs) in right triangles. These algorithms evaluate more times the function than a standard explicit Runge–Kutta scheme (nt times per step), and these extra evaluations do not increase the order of convergence but the stability region grows with O(nt2). Hence, the

    更新日期:2020-09-10
  • Chemical Design Model for Emergent Synthetic Catch Bonds
    Front. Phys. (IF 2.638) Pub Date : 2020-07-28
    Martijn van Galen; Jasper van der Gucht; Joris Sprakel

    All primary chemical bonds inherently weaken under increasing tension. Interestingly, nature is able to combine such bonds into protein complexes that accomplish the opposite behavior: they strengthen with increasing tensional force. These complexes known as catch bonds are increasingly considered a general feature in biological systems subjected to mechanical stress. Despite their prevalence in nature

    更新日期:2020-09-10
  • Generation of α-Particle Beams With a Multi-kJ, Peta-Watt Class Laser System
    Front. Phys. (IF 2.638) Pub Date : 2020-07-22
    Daniele Margarone; Alessio Morace; Julien Bonvalet; Yuki Abe; Vasiliki Kantarelou; Didier Raffestin; Lorenzo Giuffrida; Philippe Nicolai; Marco Tosca; Antonino Picciotto; Giada Petringa; Giuseppe A. P. Cirrone; Yuji Fukuda; Yasuhiro Kuramitsu; Hideaki Habara; Yasunobu Arikawa; Shinsuke Fujioka; Emmanuel D'Humieres; Georg Korn; Dimitri Batani

    We present preliminary results on generation of energetic α-particles driven by lasers. The experiment was performed at the Institute of Laser Engineering in Osaka using the short-pulse, high-intensity, high-energy, PW-class laser. The laser pulse was focused onto a thin plastic foil (pitcher) to generate a proton beam by the well-known TNSA mechanism which, in turn, was impinging onto a boron-nitride

    更新日期:2020-09-10
  • Quasiclassical Theory of C4-Symmetric Magnetic Order in Disordered Multiband Metals
    Front. Phys. (IF 2.638) Pub Date : 2020-07-27
    Maxim Dzero; Maxim Khodas

    Recent experimental studies performed in the normal state of iron-based superconductors have discovered the existence of the C4-symmetric (tetragonal) itinerant magnetic state. This state can be described as a spin density wave with two distinct magnetic vectors Q→1 and Q→2. Given an itinerant nature of magnetism in iron-pnictides, we develop a quasiclassical theory of tetragonal magnetic order in

    更新日期:2020-09-09
  • Budding and Fission of Membrane Vesicles: A Mini Review
    Front. Phys. (IF 2.638) Pub Date : 2020-07-22
    Samo Penič; Luka Mesarec; Miha Fošnarič; Lucyna Mrówczyńska; Henry Hägerstrand; Veronika Kralj-Iglič; Aleš Iglič

    In this mini-review, a brief historical survey of the mechanisms which determine the shapes of liposomes and cells and the budding and fission of their membrane is presented. Special attention is given to the role of orientational ordering of membrane components in thin membrane necks which connect the membrane buds (daughter vesicles) to the parent membrane. It is indicated that topological anti-defects

    更新日期:2020-09-09
  • Carbon-Deficient Titanium Carbide With Highly Enhanced Hardness
    Front. Phys. (IF 2.638) Pub Date : 2020-07-28
    Hui Li; Shuailing Ma; Lixue Chen; Zhuo Yu

    We report the synthesis of a polycrystalline specimen of TiC1−x under high-pressure and high-temperature (HPHT) conditions. The carbon vacancy, crystal structure, Vicker hardness, elastic constants, and bond features of the synthesized specimen were investigated. Though the specimens were synthesized with stoichiometric ratio at high pressure, a robust carbon vacancy was observed using energy dispersive

    更新日期:2020-09-05
  • Computing Irregularity Indices for Probabilistic Neural Network
    Front. Phys. (IF 2.638) Pub Date : 2020-07-28
    Shunguang Kang; Yu-Ming Chu; Abaid ur Rehman Virk; Waqas Nazeer; Jia Jia

    A topological index (TI) is a quantity expressed as a number that help us to catch symmetry of network. With the help of quantitative structure property relationship (QSPR), we can guess physical and chemical properties of several networks. A neural network is a computer system based on the nerve system. There are numerous uses of these systems in different fields of studies but their most critical

    更新日期:2020-09-05
  • Realization of Terahertz Wavefront Manipulation Using Transmission-Type Dielectric Metasurfaces
    Front. Phys. (IF 2.638) Pub Date : 2020-07-23
    Jiaqi Li; Tingyin Ning; Min Zhang; Ireng Ling Li; Hong Su; Huawei Liang

    Metasurfaces, composed of an array of subwavelength artificial structures, have attracted great interest, owing to their high ability in locally manipulating the wavefront of electromagnetic waves. Here, we propose a dielectric metasurface based on a fused silica resonator, consisting of a rectangular-shaped bar placed in the center of a cross net-shaped structure, to manipulate the wavefront of terahertz

    更新日期:2020-09-05
  • Short-Term Lightning Response to Ground Level Enhancements
    Front. Phys. (IF 2.638) Pub Date : 2020-07-23
    Qiong Wu; Hui Li; Chi Wang

    Cosmic rays (CRs) are considered the primary energetic particle source of atmospheric ionization on Earth. Under the modulation of severe solar eruption events, CR variations are further speculated to impact the Earth's lightning activities. Previous researches show that CR intensity and lightning incidence are positively correlated on the time scale of several days to decades. However, to our knowledge

    更新日期:2020-09-05
  • Feedback Mechanisms for Self-Organization to the Edge of a Phase Transition
    Front. Phys. (IF 2.638) Pub Date : 2020-07-17
    Victor Buendía; Serena di Santo; Juan A. Bonachela; Miguel A. Muñoz

    Scale-free outbursts of activity are commonly observed in physical, geological, and biological systems. The idea of self-organized criticality (SOC), introduced back in 1987 by Bak, Tang, and Wiesenfeld suggests that, under certain circumstances, natural systems can seemingly self-tune to a critical state with its concomitant power-laws and scaling. Theoretical progress allowed for a rationalization

    更新日期:2020-09-05
  • New Solitary Wave Solutions for Variants of (3+1)-Dimensional Wazwaz-Benjamin-Bona-Mahony Equations
    Front. Phys. (IF 2.638) Pub Date : 2020-07-17
    Hadi Rezazadeh; Mustafa Inc; Dumitru Baleanu

    We solve distinct forms of (3+1)-Dimensional Wazwaz-Benjamin-Bona-Mahony [(3+1)-Dimensional WBBM] equations by employing the method of Sardar-subequation. When parameters involving this approach are taken to be special values, we can obtain the solitary wave solutions (sws) which is concluded from other approaches such as the functional variable method, the trail equation method, the first integral

    更新日期:2020-09-05
  • Electron-Only Reconnection in Plasma Turbulence
    Front. Phys. (IF 2.638) Pub Date : 2020-07-10
    Francesco Califano; Silvio Sergio Cerri; Matteo Faganello; Dimitri Laveder; Manuela Sisti; Matthew W. Kunz

    Hybrid-Vlasov–Maxwell simulations of magnetized plasma turbulence including non-linear electron-inertia effects in a generalized Ohm's law are presented. When fluctuation energy is injected on scales sufficiently close to ion-kinetic scales, the ions efficiently become de-magnetized and electron-scale current sheets largely dominate the distribution of the emerging current structures, in contrast to

    更新日期:2020-09-05
  • Scaling of Laser Fusion Experiments for DD-Neutron Yield
    Front. Phys. (IF 2.638) Pub Date : 2020-07-06
    Josef Krása; Daniel Klír

    Yields of neutrons produced in various laser fusion experiments conducted in recent decades are compared with each other. It has surprisingly been found that there is a possibility to make an overall elucidation of the variance in the number of neutrons produced in the various experiments. The common method is based on definition of the energy conversion efficiency as a ratio between the energy carried

    更新日期:2020-09-03
  • Estimation of Local Novel Coronavirus (COVID-19) Cases in Wuhan, China from Off-Site Reported Cases and Population Flow Data from Different Sources
    Front. Phys. (IF 2.638) Pub Date : 2020-07-20
    Zian Zhuang; Peihua Cao; Shi Zhao; Yijun Lou; Shu Yang; Weiming Wang; Lin Yang; Daihai He

    In December 2019, novel coronavirus disease (COVID-19) hit Wuhan, Hubei Province, China and spread to the rest of China and overseas. The emergence of this virus coincided with the Spring Festival Travel Rush in China. It is possible to estimate the total number of COVID-19 cases in Wuhan, by 23 January 2020, given the cases reported in other cities/regions and population flow data between Wuhan and

    更新日期:2020-09-01
  • Hybrid Active-Passive Space Radiation Simulation Concept for GSI and the Future FAIR Facility
    Front. Phys. (IF 2.638) Pub Date : 2020-07-20
    Christoph Schuy; Uli Weber; Marco Durante

    Space radiation is acknowledged as one of the main health risks for human exploration of the Solar system. Solar particle events (SPE) and the galactic cosmic radiation (GCR) can cause significant early and late morbidity, and damage mission critical microelectronics. Systematic studies of the interaction of energetic heavy ions with biological and electronic systems are typically performed at high-energy

    更新日期:2020-08-31
  • Quantum Dot-Driven Stabilization of Liquid-Crystalline Blue Phases
    Front. Phys. (IF 2.638) Pub Date : 2020-07-09
    George Cordoyiannis; Marta Lavrič; Maja Trček; Vasileios Tzitzios; Ioannis Lelidis; George Nounesis; Matej Daniel; Zdravko Kutnjak

    Liquid crystals hosting nanoparticles comprise a fascinating research field, ranging from fundamental aspects of phase transitions to applications in optics and photonics. Liquid-crystalline phases exhibit topological defects that can be used for assembly of nanoparticles in periodical arrays, and at the same time, the nanoparticles can increase the stability range of liquid-crystalline phases. This

    更新日期:2020-08-31
  • Magnetic and Dielectric Properties of La and Ni Co-substituted BiFeO3 Nanoceramics
    Front. Phys. (IF 2.638) Pub Date : 2020-06-23
    Amit Srivastava; Ashwani Kumar Singh; O. N. Srivastava; H. S. Tewari; Khalid B. Masood; Jai Singh

    The increasing plead for the realization of ultra-fast, miniaturized, compact, and ultra-low power consumption in electronic as well as spintronic devices has propelled the quest for novel multiferroic materials that efficiently enable voltage control of magnetism. The present work reports the phase stability, magnetic and dielectric responses of polycrystalline Bi1−xLaxFe1−yNiyO3 (0 ≤ x ≥ 0.2 and

    更新日期:2020-08-31
  • Radioactive Beams in Particle Therapy: Past, Present, and Future
    Front. Phys. (IF 2.638) Pub Date : 2020-07-14
    Marco Durante; Katia Parodi

    Heavy ion therapy can deliver high doses with high precision. However, image guidance is needed to reduce range uncertainty. Radioactive ions are potentially ideal projectiles for radiotherapy because their decay can be used to visualize the beam. Positron-emitting ions that can be visualized with PET imaging were already studied for therapy application during the pilot therapy project at the Lawrence

    更新日期:2020-08-28
  • Unorthodox Dimensional Interpolations for He, Li, Be Atoms and Hydrogen Molecule
    Front. Phys. (IF 2.638) Pub Date : 2020-07-16
    Kumar J. B. Ghosh; Sabre Kais; Dudley R. Herschbach

    We present a simple interpolation formula using dimensional limits D = 1 and D = ∞ to obtain the D = 3 ground-state energies of atoms and molecules. For atoms, these limits are linked by first-order perturbation terms of electron-electron interactions. This unorthodox approach is illustrated by ground-states for two, three, and four electron atoms, with modest effort to obtain fairly accurate results

    更新日期:2020-08-27
  • Terahertz Nonreciprocal Isolator Based on Magneto-Plasmon and Destructive Interference at Room Temperature
    Front. Phys. (IF 2.638) Pub Date : 2020-07-20
    Yunyun Ji; Fei Fan; Zhiyu Tan; Shengjiang Chang

    A terahertz isolator is demonstrated for the THz nonreciprocal reflections in the magneto-optical microstructure composed of InSb and metasurface with a dielectric interlayer. In the Voigt magnetic field configuration, the reflectance of the p-polarization waves obliquely impinging on the InSb wafer exhibits high nonreciprocity, while the reflectance of the s-polarized wave is reciprocal. Based on

    更新日期:2020-08-26
  • Stress Evolution in Punch-Through Shear Tests: A Numerical Study Based on Discrete Element Method
    Front. Phys. (IF 2.638) Pub Date : 2020-07-15
    Jie Liu; Wen Wan; Yanlin Zhao; Xiang Fan

    The discrete element method is adopted to investigate the failure process in punch-through shear tests. The numerical tests agree well with the laboratory tests on crack propagation sequence and the influence of confining stress on effective shear fracture toughness. More importantly, the numerical tests indicate that the increase in axial force first causes stress concentrations. When the stresses

    更新日期:2020-08-26
  • Characterizing the Non-equilibrium Dynamics of Field-Driven Correlated Quantum Systems
    Front. Phys. (IF 2.638) Pub Date : 2020-07-14
    Herbert F. Fotso; James K. Freericks

    Recent experimental advances in ultrafast phenomena have triggered renewed interest in the dynamics of correlated quantum systems away from equilibrium. We review non-equilibrium dynamical mean-field theory studies of both the transient and the steady states of a DC field-driven correlated quantum system. In particular, we focus on the non-equilibrium behavior and how it relates to the fluctuation-dissipation

    更新日期:2020-08-26
  • A Perspective on Correlation-Based Financial Networks and Entropy Measures
    Front. Phys. (IF 2.638) Pub Date : 2020-07-13
    Vishwas Kukreti; Hirdesh K. Pharasi; Priya Gupta; Sunil Kumar

    In this mini-review, we critically examine the recent work done on correlation-based networks in financial systems. The structure of empirical correlation matrices constructed from the financial market data changes as the individual stock prices fluctuate with time, showing interesting evolutionary patterns, especially during critical events such as market crashes, bubbles, etc. We show that the study

    更新日期:2020-08-25
  • Dosimetry for FLASH Radiotherapy: A Review of Tools and the Role of Radioluminescence and Cherenkov Emission
    Front. Phys. (IF 2.638) Pub Date : 2020-07-15
    Muhammad Ramish Ashraf; Mahbubur Rahman; Rongxiao Zhang; Benjamin B. Williams; David J. Gladstone; Brian W. Pogue; Petr Bruza

    While spatial dose conformity delivered to a target volume has been pushed to its practical limits with advanced treatment planning and delivery, investigations in novel temporal dose delivery are unfolding new mechanisms. Recent advances in ultra-high dose radiotherapy, abbreviated as FLASH, indicate the potential for reduction in healthy tissue damage while preserving tumor control. FLASH therapy

    更新日期:2020-08-21
  • Dissipative Soliton Generation From Yb-Doped Fiber Laser Modulated by Mechanically Exfoliated NbSe2
    Front. Phys. (IF 2.638) Pub Date : 2020-07-13
    Longlong Chen; Lin Du; Jie Li; Lingling Yang; Qian Yi; Chujun Zhao

    We experimentally demonstrated that the stable dissipative solitons can be generated from the Yb-doped fiber laser with the interaction of mechanically exfoliated NbSe2 and the evanescent field of the D-shaped fiber. The modulation depth of the saturable absorber with exfoliated layered NbSe2 is 17.26% and the saturation intensity is 34.8 kW/cm2, respectively. With the proposed saturable absorber,

    更新日期:2020-08-21
  • Confucianism and Firm Performance
    Front. Phys. (IF 2.638) Pub Date : 2020-07-10
    Lisong Wang; Yongjie Zhang; LiNa Wang; Jingkai Fu

    This paper examines the impact of Confucianism on firm performance, taking Chinese listed companies from 2000 to 2018 as the research object. The results show that (1) Confucianism provides legitimacy for a company's profit-seeking behavior and therefore helps to improve firm performance; and (2) Confucianism can effectively improve the efficiency of supervision mechanisms but weaken the marginal contribution

    更新日期:2020-08-21
  • Design of Broadband High Gain Polarization Reconfigurable Fabry-Perot Cavity Antenna Using Metasurface
    Front. Phys. (IF 2.638) Pub Date : 2020-07-10
    Chun Ni; Changqing Liu; Zhongxiang Zhang; Mingsheng Chen; Liang Zhang; Xianliang Wu

    A broadband high gain polarization reconfigurable antenna based on metasurface has been presented. The antenna is composed of a planar metasurface, a slot antenna and an air cavity. The metasurface is made up of 64 identical patches, and all the patches are on the top surface of the substrate. The spatial equivalent circuit of the metasurface is discussed and two approximate calculation formulas of

    更新日期:2020-08-21
  • Electronic and Magnetic Anisotropies in FeSe Family of Iron-Based Superconductors
    Front. Phys. (IF 2.638) Pub Date : 2020-07-09
    Tong Chen; Ming Yi; Pengcheng Dai

    Most parent compounds of iron-based superconductors (FeSCs) exhibit a tetragonal-to-orthorhombic lattice distortion below Ts associated with an electronic nematic phase that breaks the four-fold (C4) rotational symmetry of the underlying lattice, and then forms collinear antiferromagnetic (AF) order below TN (TN ≤ Ts). Optimal superconductivity emerges upon suppression of the nematic and AF phases

    更新日期:2020-08-21
  • MR-Guided Drug Release From Liposomes Triggered by Thermal and Mechanical Ultrasound-Induced Effects
    Front. Phys. (IF 2.638) Pub Date : 2020-07-14
    Deyssy Patrucco; Enzo Terreno

    One of the most challenging tasks of the cancer research is the enhancement of the amount of the chemotherapeutic agent that can reach the target site. To achieve this goal, nanovectors capable of encapsulating the drug and releasing it following a specific stimulus have been developed. In light of this, a key point is the necessity to monitor the effective drug release through a safe and highly performing

    更新日期:2020-08-21
  • Effects of Pair-Hopping Coupling on Properties of Multi-Band Iron-Based Superconductors
    Front. Phys. (IF 2.638) Pub Date : 2020-06-23
    Andrzej Ptok; Konrad Jerzy Kapcia; Przemysław Piekarz

    A variety of superconducting materials exhibit multi-band behavior in a form of multicomponent Fermi surfaces. By using a two-band model with a pair hopping, we explain how the interband coupling affects the physical properties of multi-band superconductors. We determine the temperature dependence of the superconducting gap and the specific heat, which strongly diverge from the BCS-type behavior. The

    更新日期:2020-08-19
  • Multiple-Band Terahertz Metamaterial Absorber Using Multiple Separated Sections of Metallic Rectangular Patch
    Front. Phys. (IF 2.638) Pub Date : 2020-07-06
    Ben-Xin Wang; Yuanhao He; Pengcheng Lou; Nianxi Xu; Xiaoyi Wang; Yanchao Wang; Jianjun Cao

    Multiple-band metamaterial absorbers have been widely reported using the co-planar or layered design methods. However, these obtained absorption devices are of complex structure, large unit size, heavy weight, and time-consuming construction steps. Herein, an alternative design strategy is suggested to realize the multiple-band absorption at terahertz frequency. By introducing air gaps into the rectangular

    更新日期:2020-08-14
  • Input Redundancy for Parameterized Quantum Circuits
    Front. Phys. (IF 2.638) Pub Date : 2020-06-30
    Francisco Javier Gil Vidal; Dirk Oliver Theis

    One proposal to utilize near-term quantum computers for machine learning are Parameterized Quantum Circuits (PQCs). There, input is encoded in a quantum state, parameter-dependent unitary evolution is applied, and ultimately an observable is measured. In a hybrid-variational fashion, the parameters are trained so that the function assigning inputs to expectation values matches a target function. The

    更新日期:2020-08-14
  • One-Dimensional Plasmonic Sensors
    Front. Phys. (IF 2.638) Pub Date : 2020-07-07
    Yitian Liu; Yaoguang Ma

    Recent advances in surface plasmon sensors have significantly reduced the limitations of conventional optical sensors. With the recent development of micro- and nano-fabrication technology, miniaturized one-dimensional structures become a promising platform for surface plasmon sensors for its compactness and simple structure. In this review, we describe the generation of surface plasmon polaritons

    更新日期:2020-08-14
  • Estimation of Infection Rate and Predictions of Disease Spreading Based on Initial Individuals Infected With COVID-19
    Front. Phys. (IF 2.638) Pub Date : 2020-07-06
    Seo Yoon Chae; KyoungEun Lee; Hyun Min Lee; Nam Jung; Quang Anh Le; Biseko Juma Mafwele; Tae Ho Lee; Doo Hwan Kim; Jae Woo Lee

    We consider the pandemic spread of COVID-19 in selected countries after the outbreak of the SARS-CoV-2 coronavirus in Wuhan City, China. We estimated the infection rate and the initial individuals infected with COVID-19 by using officially reported data from the early stages of the epidemic for a model of susceptible (S), infectible (I), quarantined (Q), and officially confirmed recovered (Rk) populations

    更新日期:2020-08-14
  • Lattice QCD and Baryon-Baryon Interactions: HAL QCD Method
    Front. Phys. (IF 2.638) Pub Date : 2020-07-03
    Sinya Aoki; Takumi Doi

    In this article, we review the HAL QCD method to investigate baryon-baryon interactions, such as nuclear forces in lattice QCD. We first explain our strategy in detail to investigate baryon-baryon interactions by defining potentials in field theories, such as QCD. We introduce the Nambu-Bethe-Salpeter (NBS) wave functions in QCD for two baryons below the inelastic threshold. We then define the potential

    更新日期:2020-08-14
  • Delineating Changes in the Fundamental Structure of Signed Networks
    Front. Phys. (IF 2.638) Pub Date : 2020-06-29
    Patrick Doreian; Andrej Mrvar

    We tackle two problems. One is understanding parts of the operation of the US Supreme Court. The other is a fundamental problem for network analysis. It is delineating the fundamental structures of networks. Even more important, within this second problem, is delineating changes of this network structure over time. We present a method for doing both for signed networks. The two problems are coupled

    更新日期:2020-08-14
  • Characterizing Radiation Effectiveness in Ion Beam Therapy Part I: Introduction and Biophysical Modeling of RBE Using the LEMIV
    Front. Phys. (IF 2.638) Pub Date : 2020-06-18
    Michael Scholz; Thomas Friedrich; Giulio Magrin; Paolo Colautti; Aleksandra Ristić-Fira; Ivan Petrović

    The specific advantages of ion beams for application in tumor therapy are attributed to their different macroscopic and microscopic energy deposition pattern as compared to conventional photon radiation. On the macroscopic scale, the inverted dose profile with a Bragg peak and small lateral scattering allow a better conformation of the dose to the tumor. On the microscopic scale, the localized energy

    更新日期:2020-08-14
  • Bifurcation and Numerical Simulations of Ca2+ Oscillatory Behavior in Astrocytes
    Front. Phys. (IF 2.638) Pub Date : 2020-06-10
    Hongkun Zuo; Min Ye

    In this paper, the dynamical analysis of Ca2+ oscillations in astrocytes is theoretically investigated by the center manifold theorem and the stability theory of equilibrium point. The global structure of bifurcation and evoked Ca2+ dynamics are presented in a human astrocyte model from a mathematical perspective. Results show that the difference in appearance and disappearance of Ca2+ oscillations

    更新日期:2020-08-14
  • Graphene-Assisted Narrow Bandwidth Dual-Band Tunable Terahertz Metamaterial Absorber
    Front. Phys. (IF 2.638) Pub Date : 2020-07-03
    Dexian Yan; Miao Meng; Jiusheng Li; Xiangjun Li

    A tunable graphene terahertz metamaterial absorber is designed by treating a monolayer continuous dumbbell-shaped structure graphene layer, which can simultaneously realize the narrow bandwidth and dual-band absorption with transverse magnetic (TM) polarization and wide incident angle operation. Two pronounced absorption peaks are caused by the novel toroidal dipole phenomenon and magnetic plasmon

    更新日期:2020-08-12
  • Endowing Metal Surfaces With Underwater Superoleophobicity by Femtosecond Laser Processing for Oil-Water Separation Application
    Front. Phys. (IF 2.638) Pub Date : 2020-07-02
    Jiale Yong; Qing Yang; Xun Hou; Feng Chen

    In this paper, a widely applicable method that has promise in endowing various metals with oil-water separation ability by femtosecond laser processing is reported. We take an iron sheet as an example to show how to use a femtosecond laser to prepare underwater superoleophobic microstructure on metal substrates and then achieve oil-water separation. An array of through microholes was previously prepared

    更新日期:2020-08-12
  • Hydrodynamic Quantum Field Theory: The Onset of Particle Motion and the Form of the Pilot Wave
    Front. Phys. (IF 2.638) Pub Date : 2020-06-30
    Matthew Durey; John W. M. Bush

    We consider the hydrodynamic quantum field theory proposed by Dagan and Bush, a model of quantum dynamics inspired by Louis de Broglie and informed by the hydrodynamic pilot-wave system discovered by Couder and Fort. According to this theory, a quantum particle has an internal vibration at twice the Compton frequency that generates disturbances in an ambient scalar field, the result being self-propulsion

    更新日期:2020-08-11
  • Coal Mine Abutment Pressure Distribution Based on a Strain-Softening Model
    Front. Phys. (IF 2.638) Pub Date : 2020-06-11
    Ang Li; Qiang Ma; Li Ma; Li Kang; Qian Mu; Jianbo Chen

    The coal in front of the mining face presents strain softening deformation characteristics. An analytical model is proposed to simulate the abutment pressure distribution over the coal in front of the mining face under elastic and inelastic conditions. A new theoretical formula is derived from calculating the abutment pressure distribution and its width in elastic and inelastic regions of the coal

    更新日期:2020-08-11
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