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Volume 35 Issue 10
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GENERAL
Renormalization of Tripartite Entanglement in Spin Systems with Dzyaloshinskii–Moriya Interaction
Meng Qin, Li Wang, Bili Wang, Xiao Wang, Zhong Bai, Yanbiao Li
Chin. Phys. Lett. 2018, 35 (10): 100301 .   DOI: 10.1088/0256-307X/35/10/100301
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Quantum entanglement represents a fundamental feature of quantum many-body systems. We combine tripartite entanglement with quantum renormalization group theory to study the quantum critical phenomena. The Ising model and the Heisenberg $XXZ$ model in the presence of the Dzyaloshinskii–Moriya interaction are adopted as the research objects. We identify that the tripartite entanglement can signal the critical point. The derivative of tripartite entanglement shows singularity as the spin chain size increases. Furthermore, the intuitive scaling behavior of the system selected is studied and the result allows us to precisely quantify the correlation exponent by utilizing the power law.
Gravitational Perturbations in Einstein Aether Black Hole Spacetime
Chi-Kun Ding
Chin. Phys. Lett. 2018, 35 (10): 100401 .   DOI: 10.1088/0256-307X/35/10/100401
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We study the gravitational perturbations in Einstein aether black hole spacetime and find that the quasinormal modes (QNMs) of the first kind of aether black hole are similar to that of a Lorentz violation (LV) model, the quantum electrodynamics (QED) extension limit of standard model extension. These similarities between completely different backgrounds may imply that LV in the gravity sector and LV in the matter sector have some connections: damping QNMs more rapidly and prolonging its oscillation period. Compared to the Schwarzschild case, the first kind of black holes have larger damping rates and the second ones have lower damping rates, and they all have smaller real oscillation frequency. These differences could be detected by the new generation of gravitational antennas.
NUCLEAR PHYSICS
Alternating Parity Band in Octupole-Soft $^{140}$Xe with Axial Vibrational-Rotational Model and Triaxial Rigid Rotor Model
Xiao Lu, Bin Qi, Shou-Yu Wang
Chin. Phys. Lett. 2018, 35 (10): 102101 .   DOI: 10.1088/0256-307X/35/10/102101
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Energies of the yrast positive- and negative-parity excited states in $^{140}$Xe are reproduced by two different models considering quadrupole-octupole deformations, namely the axial vibrational-rotational model and the triaxial rigid rotor model, and compared with the stable octupole-deformed $^{222}$Th. The origin of the energy difference between the opposite parity sequences is considered from two different mechanisms, the vibration in axial deformed energy minima and the rotation considering the effective triaxial deformation. The success of reproducing the data in both the models implies that these two mechanisms are equivalent on some level for the octupole-soft nuclei. By investigating the probability distributions for projection of total angular momentum in the triaxial rigid rotor model, it is found that such an energy difference is associated with the difference of orientation of the rotational axis.
ATOMIC AND MOLECULAR PHYSICS
Theoretical Investigation on the Low-Lying States of LaP Molecule
Nagat Elkahwagy, Atif Ismail, S. M. A. Maize, K. R. Mahmoud
Chin. Phys. Lett. 2018, 35 (10): 103101 .   DOI: 10.1088/0256-307X/35/10/103101
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The completely unexplored LaP molecule is investigated by ab initio methods. Potential energy curves for the low-lying states of LaP are constructed by means of the diffusion Monte Carlo method combined with three different trial functions. Spectroscopic constants are also numerically derived and the ground state is assigned, looking forward to experimental comparisons. Moreover, variations of the permanent dipole moments as a function of the internuclear separation for the two lowest states of the diatomic LaP are studied and analyzed.
Transition Dipole Moment Measurements of Ultracold Photoassociated $^{85}$Rb$^{133}$Cs Molecules by Depletion Spectroscopy
Juan-Juan Cao, Ting Gong, Zhong-Hao Li, Zhong-Hua Ji, Yan-Ting Zhao, Lian-Tuan Xiao, Suo-Tang Jia
Chin. Phys. Lett. 2018, 35 (10): 103301 .   DOI: 10.1088/0256-307X/35/10/103301
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The transition dipole moments (TDMs) of ultracold $^{85}$Rb$^{133}$Cs molecules between the lowest vibrational ground level, $X^{1}{\it \Sigma}^{+}$ ($v=0$, $J=1$), and the two excited rovibrational levels, $2^{3}{\it \Pi}_{0^{+}}$ ($v'=10$, $J'=2$) and $2^{1}{\it \Pi}_{1}$ ($v'=22$, $J'=2$), are measured using depletion spectroscopy. The ground-state $^{85}$Rb$^{133}$Cs molecules are formed from cold mixed component atoms via the $2^{3}{\it \Pi}_{0^{-}}$ ($v=11$, $J=0$) short-range level, then detected by time-of-flight mass spectrum. A home-made external-cavity diode laser is used as the depletion laser to couple the ground level and the two excited levels. Based on the depletion spectroscopy, the corresponding TDMs are then derived to be 3.5(2)$\times$$10^{-3}$$ea_{0}$ and 1.6(1)$\times$$10^{-2}$$ea_{0}$, respectively, where $ea_{0}$ represents the atomic unit of electric dipole moment. The enhance of TDM with nearly a factor of 5 for the $2^{1}{\it \Pi}_{1}$ ($v'=22$, $J'=2$) excited level means that it has stronger coupling with the ground level. It is meaningful to find more levels with much more strong coupling strength by the represented depletion spectroscopy to realize direct stimulated Raman adiabatic passage transfer from scattering atomic states to deeply molecular states.
First-Principles Study of Magnetic Properties of TM$_{13}$ and TM$_{13}$@Au$_{32}$ Clusters (TM=Mn, Co)
Yi-Bo Li, Li-Jin Zeng, Chun-Xiang Zhao, Chun-Yao Niu
Chin. Phys. Lett. 2018, 35 (10): 103601 .   DOI: 10.1088/0256-307X/35/10/103601
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The structural and magnetic properties of TM$_{13}$ and TM$_{13}$@Au$_{32}$ clusters (TM=Mn, Co) are studied by first-principles calculations. We find that the Au$_{32}$ cluster can tune not only the magnetic moment but also the magnetic coupling properties between the TM atoms of the TM cluster. The Au$_{32}$ cluster can increase the net magnetic moment of Mn$_{13}$ clusters while reducing that of Co$_{13}$ clusters. The interaction between Au and Mn atoms induces more Mn atoms to form spin parallel coupling, resulting in an increase of the total magnetic moment of Mn$_{13}$ clusters, while for the Co$_{13}$ clusters, the interaction between Au and Co atoms does not change the magnetic coupling states between the Co atoms, but reduces the magnetic moment of the Co atoms, leading to a decrease of the total magnetic moment of this system. Our findings indicate that the encapsulation of Au$_{32}$ clusters can not only raise the chemical stability of TM clusters, but also can tune their magnetic coupling properties and magnetic moment, which enables such systems to be widely applied in fields of spintronics and medical science.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
Q-Switched Erbium-Doped Fiber Laser Using Cadmium Selenide Coated onto Side-Polished D-Shape Fiber as Saturable Absorber
M. F. M. Rusdi, M. B. H. Mahyuddin, A. A. Latiff , H. Ahmad, S. W. Harun
Chin. Phys. Lett. 2018, 35 (10): 104201 .   DOI: 10.1088/0256-307X/35/10/104201
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A stable Q-switched erbium doped fiber laser emitting at 1558 nm is demonstrated using a cadmium selenide (CdSe) material coated onto a side-polished D-shape fiber as the saturable absorber (SA). By elevating the input pump power from the threshold of 91 mW to the maximum available power of 136 mW, a pulse train with a maximum repetition rate of 57.44 kHz, minimum pulse width of 3.76 μs, maximum average output power of 7.99 mW, maximum pulse energy of 0.1391 $\mu$J, and maximum peak power of 36.99 mW are obtained. The signal-to-noise ratio of the spectrum is measured to be around 75 dB. This CdSe based SA is simple, robust, and reliable, and thus suitable for making a portable pulse laser source.
Tunable Supercontinuum Generated in a Yb$^{3+}$-Doped Microstructure Fiber Pumped by Ti:Sapphire Femtosecond Laser
Wei Wang, Fan-Chao Meng, Yuan Qing, Shi Qiu, Ting-Ting Dong, Wei-Zhen Zhu, Yu-Ting Zuo, Ying Han, Chao Wang, Yue-Feng Qi, Lan-Tian Hou
Chin. Phys. Lett. 2018, 35 (10): 104202 .   DOI: 10.1088/0256-307X/35/10/104202
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We experimentally demonstrate that a tunable supercontinuum (SC) can be generated in a Yb$^{3+}$-doped microstructure fiber by the concept of wavelength conversion with a Ti:sapphire femtosecond (fs) laser as the pump. Experimental results show that an emission light around 1040 nm in an anomalous dispersion region is first generated and amplified by fs pulses in the normal dispersion region. Then, SC spectra from 1100 to 1380 nm and 630 to 840 nm can be achieved by combined effects of higher-order soliton fission and Raman soliton self-frequency shift in the anomalous dispersion region and self-phase modulation, dispersive wave, and four-wave mixing in the normal dispersion region. It is also demonstrated that the 20 nm change of pump results in a 280 nm broadband shift of soliton and the further red-shift of soliton is limited by OH$^{-}$ absorption at 1380 nm.
Magneto and Electro-Optic Intensity Modulator Based on Liquid Crystal and Magnetic Fluid Filled Photonic Crystal Fiber
Yue-Lan Lu, Fei-Ru Wang, Chi Zhang, Ji-Wen Yin, Yu Huang, Wei-Min Sun, Yong-Jun Liu
Chin. Phys. Lett. 2018, 35 (10): 104203 .   DOI: 10.1088/0256-307X/35/10/104203
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We propose a novel light intensity modulator based on magnetic fluid and liquid crystal (LC) filled photonic crystal fibers (PCFs). The influences of electric and magnetic fields on the transmission intensity are theoretically and experimentally analyzed and investigated. Both the electric and magnetic fields can manipulate the molecular arrangement of LC to array a certain angle without changing the refractive index of the LC. Therefore, light loss in the PCF varies with the electric and magnetic fields whereas the peak wavelengths remain constant. The experimental results show that the transmission intensity decreases with the increase of the electric and magnetic fields. The cut-off electric field is 0.899 V/μm at 20 Hz and the cut-off magnetic field is 195 mT. This simple and compacted optical modulator will have a great prospect in sensing applications.
High-Efficiency Wide-Band Cross-Polarization Conversion Using Bi-layered Metal Hole Pairs
Yong Zhang, Xian-Ke Li, Cheng-Ping Huang
Chin. Phys. Lett. 2018, 35 (10): 104204 .   DOI: 10.1088/0256-307X/35/10/104204
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We present a polarization converter composed of bi-layered metal films perforated with rectangle hole pairs in each film. The proposed converter can convert the polarization of an incident linearly-polarized electromagnetic wave to its orthogonal direction with high efficiency and large bandwidth in the infrared or microwave regions. To make sure of the mechanism of polarization conversion, the current and electric-field distributions at different resonant frequencies are analyzed. It is found that the cross-polarized transmission is due to the near-field coupling between hole pairs in neighboring metal films. Finally, a prototype of the proposed converter is fabricated and measured in the microwave region. Good agreement between the experimental and simulated results is obtained.
Effects of Metal Absorber Thermal Conductivity on Clear Plastic Laser Transmission Welding
Min-Qiu Liu, De-Qin Ouyang, Chun-Bo Li, Hui-Bin Sun, Shuang-Chen Ruan
Chin. Phys. Lett. 2018, 35 (10): 104205 .   DOI: 10.1088/0256-307X/35/10/104205
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In our previous study, metals have been used as absorbers in the clear plastic laser transmission welding. The effects of metal thermal conductivity on the welding quality are investigated in the present work. Four metals with distinctly different thermal conductivities, i.e., titanium, nickel, molybdenum, and copper, are selected as light absorbers. The lap welding is conducted with an 808 nm diode laser and simulation experiments are also conducted. Nickel electroplating test is carried out to minimize the side-effects from different light absorptivities of different metals. The results show that the welding with an absorber of higher thermal conductivity can accommodate higher laser input power before smoking, which produces a wider and stronger welding seam. The positive role of the higher thermal conductivity can be attributed to the fact that a desirable thermal field distribution for the molecular diffusion and entanglement is produced from the case with a high thermal conductivity.
Acoustic Multi Emission Lens via Transformation Acoustics
H. Barati, Z. Basiri, A. Abdolali
Chin. Phys. Lett. 2018, 35 (10): 104301 .   DOI: 10.1088/0256-307X/35/10/104301
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Based on transformation acoustic methodology, we propose an algorithm for designing acoustic non-resonant lens antenna, which is competent to generate multiple directive beams that are pointing at the desired direction. Unattainable with previous works, the present approach is capable of adjusting the directivity of each radiated beam individually, which is of the utmost importance in several acoustic applications such as in sonar systems. A linear transformation function is intentionally used for eliminating the inhomogeneity of the obtained materials and to pave the way towards more general acoustic patterns. Several numerical simulations are performed to show the capability of the proposed method in manipulating the acoustic waves. To authenticate the concept, a structure that can generate four beams with different directivities is realized with non-resonant meta-fluid bi-layered structure through effective medium theory.
Viscous Slip MHD Flow over a Moving Sheet with an Arbitrary Surface Velocity
Tiegang Fang, Fujun Wang
Chin. Phys. Lett. 2018, 35 (10): 104701 .   DOI: 10.1088/0256-307X/35/10/104701
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The magnetohydrodynamic (MHD) flow induced by a stretching or shrinking sheet under slip conditions is studied. Analytical solutions based on the boundary layer assumption are obtained in a closed form and can be applied to a flow configuration with any arbitrary velocity distributions. Seven typical sheet velocity profiles are employed as illustrating examples. The solutions to the slip MHD flow are derived from the general solution and discussed in detail. Different from self-similar boundary layer flows, the flows studied in this work have solutions in explicit analytical forms. However, the current flows require special mass transfer at the wall, which is determined by the moving velocity of the sheet. The effects of the slip parameter, the mass transfer at the wall, and the magnetic field on the flow are also demonstrated.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Collisional Effects on Drift Wave Microturbulence in Tokamak Plasmas
Wei Hu, Hong-Ying Feng, Chao Dong
Chin. Phys. Lett. 2018, 35 (10): 105201 .   DOI: 10.1088/0256-307X/35/10/105201
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Collisional effects on the microturbulence, excited by the electrostatic drift-wave instability, are investigated through first-principle large scale gyrokinetic particle simulations using the realistic discharge parameters of the DIII–D Tokamak. In the linear simulations, the growth rates of the drift waves are decreased by the collisions compared to the collisionless simulations in the lower and higher $T_{\rm e}$ plasmas. In the lower $T_{\rm e}$ plasma, the collisions can promote the transition of the drift wave regime from the TEM-dominant instability to the ITG-dominant instability. The zonal flows are excited by the microturbulence and work as a modulation mechanism for the microturbulence in the nonlinear simulations. Microturbulence can excite high frequency zonal flows in the collisionless plasmas, which is in agreement with the theoretical work. In the lower $T_{\rm e}$ plasma, the collisions decrease the microturbulence in the nonlinear saturated stage compared to the collisionless simulations, which are beneficial for the plasma confinement. In the higher $T_{\rm e}$ plasma, the final saturated microturbulence shows a slight change.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
Surface Tension and Electrostriction in a Suspended Bridge of Dielectric Liquid
Yan Cen, Chuanshan Tian
Chin. Phys. Lett. 2018, 35 (10): 106801 .   DOI: 10.1088/0256-307X/35/10/106801
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The mechanism of the formation of a surprisingly long suspended liquid bridge subjected to a dc electric field has been intensively studied in the past few decades. However, the role of electrostriction and quantitative evaluation of surface tension in the bridge have not been evaluated. We present combined theoretical and experimental studies on this issue. Electrostriction is pointed out to be the driving force that pushes liquid upward against gravity and into the gap between two containers and forms the suspended bridge, which is within the framework of the Maxwell pressure tensor. Through a comparison between experiment and theory, the surface tension is found to play an important role in holding the long suspended bridge. Ignorance of the surface tension leads to much smaller bridge length than the experimental values. The dynamic stability of the bridge with respect to its diameter, length and conductance is also discussed.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Computational Prediction to Two-Dimensional SnAs
Dawei Zhou, Yangbing Zheng, Chunying Pu, Zhuo Wang, Xin Tang
Chin. Phys. Lett. 2018, 35 (10): 107101 .   DOI: 10.1088/0256-307X/35/10/107101
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By means of the particle-swarm optimization method and density functional theory calculations, the lowest-energy structure of SnAs is determined to be a bilayer stacking system and the atoms on top of each other are of the same types. Using the hybrid functional of Heyd–Scuseria–Ernzerhof, SnAs is calculated to be a semiconductor with an indirect band gap of 1.71 eV, which decreases to 1.42 eV with the increase of the bi-axial tensile stress up to 2%, corresponding to the ideal value of 1.40 eV for potential photovoltaic applications. Based on the deformation potential theory, the two-dimensional (2D) SnAs has high electron motilities along $x$ and $y$ directions ($1.63\times10^{3}$ cm$^{2}$V$^{-1}$s$^{-1}$). Our calculated results suggest that SnAs can be viewed as a new type of 2D materials for applications in optoelectronics and nanoelectronic devices.
Impurity Effects at Surfaces of a Photon-Dressed Bi$_2$Se$_3$ Thin Film
Qiu-Shi Wang, Bin Zhang, Wei-Zhu Yi, Meng-Nan Chen, Baigeng Wang, R. Shen
Chin. Phys. Lett. 2018, 35 (10): 107201 .   DOI: 10.1088/0256-307X/35/10/107201
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We investigate the impurity effects on surfaces of a thin film topological insulator, applied by an off-resonant circular polarized light. It is found that the off-resonant driving induces a quantized total Hall conductivity, when the driving strength is larger than a critical value and the Fermi level lies in the band gap, indicating that our system is converted into the topological phase. We also find that with the increasing disorder strength, the Dirac masses of top and bottom surfaces are renormalized and then fixed to half of their initial values, respectively, which will shrink the widths of the half-integer plateau of anomalous Hall conductivities.
Temperature-Dependent Effect of Near-Interface Traps on SiC MOS Capacitance
Yan-Jing He, Xiao-Yan Tang, Yi-Fan Jia, Ci-Qi Zhou, Yu-Ming Zhang
Chin. Phys. Lett. 2018, 35 (10): 107301 .   DOI: 10.1088/0256-307X/35/10/107301
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A two-dimensional electrical SiC MOS interface model including interface and near-interface traps is established based on the relevant tunneling and interface Shockley–Read–Hall model. The consistency between simulation results and measured data in the different temperatures shows that this interface model can accurately describe the capture and emission performance for near-interface oxide traps, and can well explain the hysteresis-voltage response with increasing temperature, which is intensified by the interaction between deep oxide traps and shallow oxide traps. This also indicates that the near-interface traps result in an increase of threshold-voltage shift in SiC MOSFET with increasing temperature.
Precise, Long-Time Displacement Self-Sensing of Piezoelectric Cantilever Actuators Based on Charge Measurement Using the Sawyer–Tower Circuit
Qiang-zhong Wang, Gang Wang, Fa-xin Li
Chin. Phys. Lett. 2018, 35 (10): 107701 .   DOI: 10.1088/0256-307X/35/10/107701
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Previous studies show that near linearity exists between displacement and charge of piezoelectric actuators, while studies under higher fields are lacking and long-time displacement self-sensing is still a challenge. Here we indicate that precise, long-time displacement self-sensing can be accomplished using the Sawyer–Tower circuit, where a high-impedance electrometer and a non-leaky capacitor are used to measure the charge. Calibrating the results on a piezoelectric unimorph cantilever shows that the displacement resolution of charge self-sensing is $\sim$3 nm, much better than that of $\sim$40 nm for the calibrating laser sensor. Testing results under a unipolar field up to 2 kV/mm with different periods indicate that a direct proportional relationship holds between charge and displacement with the maximum error of 4.65%. The self-sensing time can be over 20 min or even longer if a higher-impedance electrometer is used.
Pascal Realization by Comb-Spectral-Interferometry Based Refractometer
Li-Jun Yang, Yan Li
Chin. Phys. Lett. 2018, 35 (10): 107801 .   DOI: 10.1088/0256-307X/35/10/107801
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To break through the limitations of existing pressure standards, which rely on the gravity and toxic mercury, the national metrological institutes prefer a quantum-based pressure standard. Combining the ideal gas law with helium refractivity measurement, we demonstrate a scheme for the realization of the pressure unit. The refractometer is based on a spectral interferometry with an optical frequency comb and a double-spaced vacuum cell. Through fast Fourier transform of the spectral interferograms of the two beams propagating inside and outside the vacuum cell, the helium refractivity can be obtained with a combined standard uncertainty $u(n)$ of $2.9\times 10^{-9}$. Moreover, the final $u(p)$ is $\sim$$8.7\times 10^{-6}$ in a measurement range of several megapascals (MPa). Our apparatus is compact, fast (15 ms for one single measurement) and easy to handle. Furthermore, the measurement uncertainty will be improved to $\sim$$1\times 10^{-9}$ or lower if a VIPA-based spectrometer is used. The value of $u(p)$ will thus increase to $3\times 10^{-6}$ or better in several MPa.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
An Immersed Boundary-Lattice Boltzmann Prediction for Particle Hydrodynamic Focusing in Annular Microchannels
Tao HU, Meng-Dan HU, Si-si Zhou, Dong-Ke SUN
Chin. Phys. Lett. 2018, 35 (10): 108101 .   DOI: 10.1088/0256-307X/35/10/108101
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We numerically study the dynamics of particle crystals in annular microchannels by the immersed-boundary (IB) lattice Boltzmann (LB) coupled model, analyze the fluid-particle interactions during the migration of particles, and reveal the underlying mechanism of a particle focusing on the presence of fluid flows. The results show that the Reynolds and Dean numbers are key factors influencing the hydrodynamics of particles. The particles migrate onto their equilibrium tracks by adjusting the Reynolds and Dean numbers. Elliptical tracks of particles during hydrodynamic focusing can be predicted by the IB-LB model. Both the small Dean number and the small particle can lead to a small size of the focusing track. This work would possibly facilitate the utilization of annular microchannel flows to obtain microfluidic flowing crystals for advanced applications in biomedicine and materials synthesis.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
Global Statistical Study of Ionospheric Waves Based on COSMIC GPS Radio Occultation Data
Xuan-Yun Zeng, Xiang-Hui Xue, Xin-An Yue, Ming-Jiao Jia, Bing-Kun Yu, Jian-Fei Wu, Chao Yu
Chin. Phys. Lett. 2018, 35 (10): 109401 .   DOI: 10.1088/0256-307X/35/10/109401
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Extracting and parameterizing ionospheric waves globally and statistically is a longstanding problem. Based on the multichannel maximum entropy method (MMEM) used for studying ionospheric waves by previous work, we calculate the parameters of ionospheric waves by applying the MMEM to numerously temporally approximate and spatially close global-positioning-system radio occultation total electron content profile triples provided by the unique clustered satellites flight between years 2006 and 2007 right after the constellation observing system for meteorology, ionosphere, and climate (COSMIC) mission launch. The results show that the amplitude of ionospheric waves increases at the low and high latitudes ($\sim$0.15 TECU) and decreases in the mid-latitudes ($\sim$0.05 TECU). The vertical wavelength of the ionospheric waves increases in the mid-latitudes (e.g., $\sim$50 km at altitudes of 200–250 km) and decreases at the low and high latitudes (e.g., $\sim$35 km at altitudes of 200–250 km). The horizontal wavelength shows a similar result (e.g., $\sim$1400 km in the mid-latitudes and $\sim$800 km at the low and high latitudes).
22 articles