Corrections to atomic ground state energy due to interaction between atomic electric quadrupole and optical field

We study the ground state energy of an atom interacting with an oscillating optical field with electric dipole and quadrupole coupling.Under the rotating wave approximation,we derive the effective atomic Hamiltonians of the dipole/quadrupole coupling term within the perturbation theory up to the second order.Based on the effective Hamiltonians,we analyze the atomic ground-state energy corrections of these two processes in detail.As an application,we find that for alkali-like atoms,the energy correction from the quadrupole coupling is negligible small in comparison with that from the dipole coupling,which justifies the so-called dipole approximation used in literatures.Some special cases where the quadrupole interaction may have considerable energy corrections are also discussed.Our results would be beneficial for the study of atom–light interaction beyond dipole approximation.

Confined cobalt single-atom catalysts with strong electronic metal-support interactions based on a biomimetic self-assembly strategy

Designing high-performance and low-cost electrocatalysts for oxygen evolu-tion reaction(OER)is critical for the conversion and storage of sustainable energy technologies.Inspired by the biomineralization process,we utilized the phosphorylation sites of collagen molecules to combine with cobalt-based mononuclear precursors at the molecular level and built a three-dimensional(3D)porous hierarchical material through a bottom-up biomimetic self-assembly strategy to obtain single-atom catalysts confined on carbonized biomimetic self-assembled carriers(Co SACs/cBSC)after subsequent high-temperature annealing.In this strategy,the biomolecule improved the anchoring efficiency of the metal precursor through precise functional groups;meanwhile,the binding-then-assembling strategy also effectively suppressed the nonspecific adsorption of metal ions,ultimately preventing atomic agglomeration and achieving strong electronic metal-support interactions(EMSIs).Experimental characterizations confirm that binding forms between cobalt metal and carbonized self-assembled substrate(Co–O_(4)–P).Theoretical calculations disclose that the local environment changes significantly tailored the Co d-band center,and optimized the binding energy of oxygenated intermediates and the energy barrier of oxygen release.As a result,the obtained Co SACs/cBSC catalyst can achieve remarkable OER activity and 24 h durability in 1 M KOH(η10 at 288 mV;Tafel slope of 44 mV dec-1),better than other transition metal-based catalysts and commercial IrO_(2).Overall,we presented a self-assembly strategy to prepare transition metal SACs with strong EMSIs,providing a new avenue for the preparation of efficient catalysts with fine atomic structures.

Model of self-generated magnetic field generation from relativistic laser interaction with solid targets

Generation of self-generated annular magnetic fields at the rear side of a solid target driven by relativistic laser pulse is investigated by using theoretical analysis and particle-in-cell simulations.The spatial strength distribution of magnetic fields can be accurately predicted by calculating the net flow caused by the superposition of source flow and return flow of hot electrons.The theoretical model established shows good agreement with the simulation results,indicating that the magnetic-field strength scales positively to the temperature of hot electrons.This provides us a way to improve the magnetic-field generation by using a micro-structured plasma grating in front of the solid target.Compared with that for a common flat target,hot electrons can be effectively heated with the well-designed grating size,leading to a stronger magnetic field.The spatial distribution of magnetic fields can be modulated by optimizing the grating period and height as well as the incident angle of the laser pulse.

Oscillation of Dzyaloshinskii–Moriya interaction driven by weak electric fields

Dzyaloshinskii–Moriya interaction(DMI) is under extensive investigation considering its crucial status in chiral magnetic orders, such as Néel-type domain wall(DW) and skyrmions. It has been reported that the interfacial DMI originating from Rashba spin–orbit coupling(SOC) can be linearly tuned with strong external electric fields. In this work, we experimentally demonstrate that the strength of DMI exhibits rapid fluctuations, ranging from 10% to 30% of its original value, as a function of applied electric fields in Pt/Co/MgO heterostructures within the small field regime(< 10-2V/nm). Brillouin light scattering(BLS) experiments have been performed to measure DMI, and first-principles calculations show agreement with this observation, which can be explained by the variation in orbital hybridization at the Co/MgO interface in response to the weak electric fields. Our results on voltage control of DMI(VCDMI) suggest that research related to the voltage control of magnetic anisotropy for spin–orbit torque or the motion control of skyrmions might also have to consider the role of the external electric field on DMI as small voltages are generally used for the magnetoresistance detection.

Numerical Study on the Aerodynamic and Fluid−Structure Interaction of An NREL-5MW Wind Turbine

A 5-MW wind turbine has been modeled and analyzed for fluid-structure interaction and aerodynamic performance.In this study, a full-scale model of a 5-MW wind turbine is first developed based on a computational fluid dynamics(CFD) approach, in which the unsteady, noncompressible Reynolds Averaged Navier-Stokes(RANS) method is used. The main focus of the study is to analyze the tower shadow effect on the aerodynamic performance of the wind turbine under different inlet flow conditions. Subsequently, the finite element model is established by considering fluid/structure interactions to study the structural stress, displacement, strain distributions and flow field information of the structure under the uniform wind speed. Finally, the fluid-structure interaction model is established by considering turbulent wind and the tower shadow effect. The variation rules of the dynamic response of the one-way and two-way fluid-structure interaction(FSI) models under different wind speeds are analyzed, and the numerical calculation results are compared with those of the centralized mass model. The results show that the tower shadow effect and structural deformation are the main factors affecting the aerodynamic load fluctuation of the wind turbine, which in turn affects the aerodynamic performance and structural stability of the blades. The structural dynamic response of the coupled model shows significant similarity, while the structural displacement response of the former exhibits less fluctuation compared with the conventional centralized mass model. The one-way fluid-structure interaction(FSI)model shows a higher frequency of stress-strain and displacement oscillations on the blade compared with the two-way FSI model.

The Gravitational Interaction between Moving Mass Particles Explained by the Theory of Informatons

In the article “Newtons Law of Universal Gravitation Explained by the Theory of Informatons” the gravitational interaction between mass particles at rest has been explained by the hypothesis that g-information carried by informatons is the substance of the medium that the interaction in question makes possible. It has been showed that, on the macroscopic level, that medium—the “gravitational field”—manifests itself as the vector field Eg. In this article we will deduce from the postulate of the emission of informatons, that the informatons emitted by a moving mass particle carry not only information about the position (g-information) but also about the velocity (“β-information”) of their emitter. It follows that the gravitational field of a moving mass particle is a dual entity always having a field- and an induction-component (Egand Bg) simultaneously created by their common sources: time-variable masses and mass flows and that the gravitational interaction is the effect of the fact that an object in a gravitational field always tends to become “blind” for that field by accelerating according to a Lorentz-like law.

Electronic interaction between single Pt atom and vacancies on boron nitride nanosheets and its influence on the catalytic performance in the direct dehydrogenation of propane

The electronic metal-support interaction(EMSI)is one of most intriguing phenomena in heterogeneous catalysis.In this work,this subtle effect is clearly demonstrated by density functional theory(DFT)calculations of single Pt atom supported on vacancies in a boron nitride nanosheet.Moreover,the relation between the EMSI and the performance of Pt in propane direct dehydrogenation(PDH)is investigated in detail.The charge state and partial density of states of single Pt atom show distinct features at different anchoring positions,such as boron and nitrogen vacancies(Bvac and Nvac,respectively).Single Pt atom become positively and negatively charged on Bvac and Nvac,respectively.Therefore,the electronic structure of Pt can be adjusted by rational deposition on the support.Moreover,Pt atoms in different charge states have been shown to have different catalytic abilities in PDH.The DFT calculations reveal that Pt atoms on Bvac(Pt-Bvac)have much higher reactivity towards reactant/product adsorption and C–H bond activation than Pt supported on Nvac(Pt-Nvac),with larger adsorption energy and lower barrier along the reaction pathway.However,the high reactivity of Pt-Bvac also hinders propene desorption,which could lead to unwanted deep dehydrogenation.Therefore,the results obtained herein suggest that a balanced reactivity for C–H activation in propane and propene desorption is required to achieve optimum yields.Based on this descriptor,a single Pt atom on a nitrogen vacancy is considered an effective catalyst for PDH.Furthermore,the deep dehydrogenation of the formed propene is significantly suppressed,owing to the large barrier on Pt-Nvac.The current work demonstrates that the catalytic properties of supported single Pt atoms can be tuned by rationally depositing them on a boron nitride nanosheet and highlights the great potential of single-atom catalysis in the PDH reaction.

QSAR Study on Some N-[5-(2-Furanyl)-2-methyl-4-oxo-4H-thieno[2,3-d]pyrimidin-3-yl]-carboxamide and 3-Substituted-5-(2-furanyl)-2-methyl-3H-thieno-[2,3-d]pyrimidin-4-ones Using Three-dimensional Holographic Vector of Atomic Interaction Field

Study on the quantitative structure-activity relationship （QSAR） of 26 compounds, N-[5-（2-furanyl）-2-methyl-4-oxo-4H-thieno[2,3-d]pyrimidin-3-yl]-carboxamide and 3-substituted- 5-（2-furanyl）-2-methyl-3H-thieno[2,3-d]pyrimidin-4-ones, with three-dimensional holographic vector of atomic interaction field （3D-HoVAIF） was carried out. SMR-PLS QSAR models have been created and good correlation coefficients and cross-validated correlation coefficients were obtained. The result shows that the models have good prediction capability and favorable stability and the 3D-HoVAIF is applicable to the molecular structural characterization and biological activity prediction.

Quantum entanglement between the two-mode fields and atomic entropy squeezing in the system of a moving atom interacting with two-mode entangled coherent field

This paper investigates the entropy squeezing of a moving two-level atom interacting with the two-mode entangled coherent field via two-photon transition by using an entropic uncertainty relation and the degree of entanglement between the two-mode fields by using quantum relative entropy.The results obtained from numerical calculation indicate that the squeezed period,the duration of entropy squeezing and the maximal squeezing can be controlled by appropriately choosing the intensity of the light field,the atomic motion and the field-mode structure.The atomic motion leads to the periodic recovery of the initial maximal degree of entanglement between the two-mode fields.Moreover,there exists a corresponding relation between the time evolution properties of the atomic entropy squeezing and those of the entanglement between the two-mode fields.

Relation between stabilization energy, crystal field coefficient and the magnetic exchange interaction for Tb^(3+) ion

Based on a single ion model, Hamiltonian of the simplest form about magnetocrystalline anisotropy for Tb3+ ion was solved by using the numerical method. The relation between the stabilization energy, crystal field coefficient B20 and the magnetic exchange interaction was studied as temperature approaches to 0 K. The results show that the stabilization energy contributed by Tb3+ is linear with crystal field coefficient B20 approximately, but it is insensitive to the change of magnetic exchange interaction for the strong magnetic substances such as TbCo5, Tb2Co17 and Tb2Fe14B compounds.

Generating Even-Photon State via Resonant Interaction Between Ladder-Type Three-Level Atoms with a Single-Mode Field

A scheme is presented to generate even-photon state based on resonant interaction between ladder-type three-level atoms with a single-mode field. In the scheme, a sequence of suitably prepared ladder-type three-level atoms are orderly sent through a single-mode cavity initiaJly in vacuum state. The detection of a J1 the atoms in the ground states collapses the cavity to the desired state. The scheme is based on the resonant interaction of atoms with the cavity, and thus the required interaction time can be greatly shortened. This is important in view of decoherence.

Experimental Studies of Interactions Between Backfires and Coming Surface Fires\+*

In order to study the convection limits of surface fires and interactions between backfires and main fires,several experiments are conducted in a large space indoor laboratory: in which the effects of ambient wind speeds and changing temperatures can be avoided.The research shows that:(1) there is a convection field in front of coming fires in which the wind speed direction is toward the fire.In the convection area,the lower part has higher wind speed and when the height is taller than a certain value the convection wind speed is not significant;(2) the backfire and the main fire interact with each other even though they are far apart.When they come near each other to a certain distance,they begin to draw each other.This increases their rates of spread toward each other significantly.For surface fires with a fire line intensity of 160?kW\5m -1 ,their rate of spread increases by 27%.

BEHAVIORS OF THE HYPERFINE. FIELD AND THE ATOMIC MAGNETIC MOMENT IN AMORPHOUS Fe_(80-x)T_xB_(20)(T=Co,Ni,Mn,V,Ti) ALLOYS

The mean hyper fine field at the Fe nuclei in amorphous alloys Fe80-xTxB20(T=Co,Ni,Mn,V,Ti) by fitting the Moessbauer spectra is displayed. The behaviors of both the hyperfine field and the atomic magnetic moment in these amorphous alloys and the relation between both the properties are discussed.

Atom-based power-frequency electric field measurement using the radio-frequency-modulated Rydberg spectroscopy

The radio-frequency modulated electromagnetically induced transparency(EIT) in a ladder three-level system with Rydberg state is studied. Under the influence of a fast radio-frequency field, the EIT peak splits into a series of sidebands.When attaching a power-frequency electric field directly to the fast radio-frequency field, the odd-order sidebands of the Rydberg-EIT oscillate sensitively with the power-frequency field. The oscillation frequency is equal to twice the power frequency;the oscillation amplitude is monotonically increasing with the amplitude of the power-frequency field when the change of Stark-shift is smaller than the radio frequency. Our work paves the way for measurement of power-frequency electric field based on Rydberg atoms.

Nonclassical properties in the resonant interaction of a three level ∧-type atom with two-mode field in coherent state

In this paper, we study the nonclassical properties of the electromagnetic field resulting from the interaction of a three-level ∧-type atom with a two-mode field initially in the coherent state, such as squeezing properties and sub-Poisson statistics. We show that the squeezing can be enhanced by selective atomic measurement.

Pairwise thermal entanglement in a three-qubit Heisenberg XX model with a nonuniform magnetic field and Dzyaloshinski-Moriya interaction

Pairwise thermal entanglement in a three-qubit Heisenberg XX model is investigated when a nonuniform mag- netic field and the Dzyaloshinski-Moriya interaction are included. We find that the nonuniform magnetic field and Dzyaloshinski-Moriya interaction are the more efficient control parameters for the increase of entanglement and critical temperature. For both the nearest neighbour sites and the next nearest neighbour sites, the magnetic field can induce entanglement to a certain extent and the Dzyaloshinski-Moriya interaction can enhance the entanglement to a stable value. The steady value of the nearest neighbour site entanglement C12 is larger than the next nearest neighbour site entanglement C13. An interesting phenomenon is that the entanglement curve of C12 appears a peak value when the Dzyaloshinski-Moriya interaction is considered in a nonuniform magnetic field.

Topological Magnons in Kitaev Magnets with Finite Dzyaloshinskii–Moriya Interaction at High Field

There have been intensive studies on Kitaev materials for the sake of realization of exotic states such as quantum spin liquid and topological orders.In realistic materials,the Kitaev interaction may coexist with the Dzyaloshinskii–Moriya interaction,and it is of challenge to distinguish their magnitudes separately.Here,we study the topological magnon excitations and related thermal Hall conductivity of kagome magnet exhibiting Heisenberg,Kitaev and Dzyaloshinskii–Moriya interactions exposed to a magnetic field.In a strong magnetic field perpendicular to the plane of the lattice([111]direction)that brings the system into a fully polarized paramagnetic phase,we find that the magnon bands carry nontrivial Chern numbers in the full region of the phase diagram.Furthermore,there are phase transitions related to two topological phases with opposite Chern numbers,which lead to the sign changes of the thermal Hall conductivity.In the phase with negative thermal conductivity,the Kitaev interaction is relatively large and the width of the phase increases with the strength of Dzyaloshinskii–Moriya interaction.Hence,the present study will contribute to the understanding of related compounds.

A miniaturized spin-exchange relaxation-free atomic magnetometer based on uniform light field

We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free(SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve light intensity uniformity, while the volume of the sensor is also reduced. This scheme makes the magnetometer have better sensitivity when the detected light intensity is less than 3.16 m W/cm^(2) at 120℃. When the temperature rises to 150℃ the sensitivity under the action of uniform light field is 18.5 f T/Hz^(1/2). The bandwidth of the sensor remains at the original level and meets application needs. The proposed structure improves transverse polarization uniformity within the miniaturized sensor, which is ideal for the magnetoencephalography and magnetocardiography imaging systems.

Preparation and control of atomic optimal entropy squeezing states for a moving two-level atom under control of the two-mode squeezing vacuum fields

From the viewpoint of quantum information, this paper studies preparation and control of atomic optimal entropy squeezing states （AOESS） for a moving two-level atom under control of the two-mode squeezing vacuum fields. Necessary conditions of preparation of the AOESS are analysed, and numerical verification of the AOESS is finished. It shows that the AOESS can be prepared by controlling the time of the atom interaction with the field, cutting the entanglement between the atom and field, and adjusting squeezing factor of the field. An atomic optimal entropy squeezing sudden generation in different components can alternately be realized by controlling the field-mode structure parameter.

Hydration film measurement on mica and coal surfaces using atomic force microscopy and interfacial interactions

The hydration film on particle surface plays an important role in bubble-particle adhesion in mineral flotation process. The thicknesses of the hydration films on natural hydrophobic coal and hydrophilic mica surfaces were measured directly by atomic force microscopy （AFM） based on the bending mode of the nominal constant compliance regime in AFM force curve in the present study. Surface and solid-liquid interfacial energies were calculated to explain the forming mechanism of the hydration film and atomic force microscopy data. The results show that there are significant differences in the structure and thickness of hydration films on coal and mica surfaces. Hydration film formed on mica surface with the thickness of 22.5 nm. In contrast, the bend was not detected in the nominal constant compliance regime. The van der Waals and polar interactions between both mica and coal and water molecules are characterized by an attractive effect, while the polar attractive free energy between water and mica （-87.36 mN/m） is significantly larger than that between water and coal （-32.89 mN/m）, which leads to a thicker and firmer hydration layer on the mica surface. The interfacial interaction free energy of the coal/water/bubble is greater than that of mica. The polar attractive force is large enough to overcome the repulsive van der Waals force and the low energy barrier of film rupture, achieving coal particle bubble adhesion with a total interfacial free energy of-56.30 mN/m.