Achieving Ultra-Broad Microwave Absorption Bandwidth Around Millimeter-Wave Atmospheric Window Through an Intentional Manipulation on Multi-Magnetic Resonance Behavior

The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range,posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth.However,existing millimeter-wave absorbers are still inadequate in addressing these issues due to their monotonous magnetic resonance pattern.In this work,rare-earth La^(3+)and non-magnetic Zr^(4+)ions are simultaneously incorporated into M-type barium ferrite(BaM)to intentionally manipulate the multi-magnetic resonance behavior.By leveraging the contrary impact of La^(3+)and Zr^(4+)ions on magnetocrystalline anisotropy field,the restrictive relationship between intensity and frequency of the multi-magnetic resonance is successfully eliminated.The magnetic resonance peak-differentiating and imitating results confirm that significant multi-magnetic resonance phenomenon emerges around 35 GHz due to the reinforced exchange coupling effect between Fe^(3+)and Fe^(2+)ions.Additionally,Mosbauer spectra analysis,first-principle calculations,and least square fitting collectively identify that additional La^(3+)doping leads to a profound rearrangement of Zr^(4+)occupation and thus makes the portion of polarization/conduction loss increase gradually.As a consequence,the La^(3+)-Zr^(4+)co-doped BaM achieves an ultra-broad bandwidth of 12.5+GHz covering from 27.5 to 40+GHz,which holds remarkable potential for millimeter-wave absorbers around the atmospheric window of 35 GHz.

Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction,and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investigation also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hydrodynamic parameters and the physical properties.

Optical absorption in asymmetrical Gaussian potential quantum dot under the application of an electric field

We theoretically investigate the optical absorption coefficient(OAC)in asymmetrical Gaussian potential quantum dots subject to an applied electric field.Confined wave functions together with energies of electron energies in an effective mass approximation framework are obtained.The OAC is expressed according to the iterative method and the compact-density-matrix approach.Based on our results,OAC is sensitively dependent on external electric field together with the incident optical intensity.Additionally,peak shifts into greater energy as the quantum dot radius decrease.Moreover,the parameters of Gaussian potential have a significant influence on the OAC.

The effects of a static magnetic field on the microwave absorption of hydrogen plasma in carbon nanotubes: a numerical study

We theoretically investigate the microwave absorption properties of hydrogen plasma in iron-catalyzed high- pressure disproportionation-grown carbon nanotubes under an external static magnetic field in the frequency range 0.3 GHz to 30 GHz, using the Maxwell equations in conjunction with a general expression for the effective complex permittivity of magnetized plasma known as the Appleton Hartree formula. The effects of the external static magnetic field intensity and the incident microwave propagation direction on the microwave absorption of hydrogen plasma in CNTs are studied in detail. The numerical results indicate that the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes can be obviously improved when the exter- nal static magnetic field is applied to the material. It is found that the specified frequency microwave can be strongly absorbed by the hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes over a wide range of incidence angles by adjusting the external magnetic field intensity and the parameters of the hydrogen plasma.

Constructing Built-In Electric Fields with Semiconductor Junctions and Schottky Junctions Based on Mo-MXene/Mo-Metal Sulfides for Electromagnetic Response

The exploration of novel multivariate heterostructures has emerged as a pivotal strategy for developing high-performance electromagnetic wave(EMW)absorption materials.However,the loss mechanism in traditional heterostructures is relatively simple,guided by empirical observations,and is not monotonous.In this work,we presented a novel semiconductor-semiconductor-metal heterostructure sys-tem,Mo-MXene/Mo-metal sulfides(metal=Sn,Fe,Mn,Co,Ni,Zn,and Cu),including semiconductor junctions and Mott-Schottky junctions.By skillfully combining these distinct functional components(Mo-MXene,MoS_(2),metal sulfides),we can engineer a multiple heterogeneous interface with superior absorption capabilities,broad effective absorption bandwidths,and ultrathin matching thickness.The successful establishment of semiconductor-semiconductor-metal heterostructures gives rise to a built-in electric field that intensifies electron transfer,as confirmed by density functional theory,which collaborates with multiple dielectric polarization mechanisms to substantially amplify EMW absorption.We detailed a successful synthesis of a series of Mo-MXene/Mo-metal sulfides featuring both semiconductor-semiconductor and semiconductor-metal interfaces.The achievements were most pronounced in Mo-MXene/Mo-Sn sulfide,which achieved remarkable reflection loss values of-70.6 dB at a matching thickness of only 1.885 mm.Radar cross-section calculations indicate that these MXene/Mo-metal sulfides have tremendous potential in practical military stealth technology.This work marks a departure from conventional component design limitations and presents a novel pathway for the creation of advanced MXene-based composites with potent EMW absorption capabilities.

Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction, and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investiga- tion also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hy- drodynamic parameters and the physical properties.

Terahertz field-induced modulations of intersubband absorptions in quantum wells

Nonlinear optical properties of intersubband electrons in a 3-level quantum well under intense terahertz field are investigated by using a density matrix approach. The results show that the terahertz fields with different frequencies cause the distinct modulations of the intersubband absorptions. The terahertz-indueed sideband and Autler-Towns splitting in the absorption spectrum are obtained, respectively for the terahertz-photon energy below and close to the transition energy between the ground and first excited state.

Optical absorption and electromagnetically induced transparency in semiconductor quantum well driven by intense terahertz field

An approach for solving the excitonic absorption in a semiconductor quantum well driven by an intense terahertz field is presented.The formalism relies on the stationary single-photon Schro¨dinger equation in the full quantum mechanical framework.The optical absorption dynamics in both weak and strong couplings are discussed and compared.The excitonic absorption spectra show the Autler-Townes doublets for the resonance terahertz field,a replica peak for the non-resonance terahertz field,and the electromagnetically induced transparency phenomenon for modulating the decay rate of the second electron state in the weak coupling.In particular,the electromagnetically induced transparency phenomenon window range is discussed.In the strong coupling region,the multi-order energy level resonance splitting due to the strong optical field is found.There are three（non-resonance terahertz field） or four（resonance terahertz field） peaks in the optical absorption spectra.This work provides a simple and convenient approach to deal with the optical absorption in the exciton system.

Polarization control of multi-photon absorption under intermediate femtosecond laser field

It has been shown that the femtosecond laser polarization modulation is a very simple and well-established method to control the multi-photon absorption process by the light-matter interaction. Previous studies mainly focused on the multi- photon absorption control in the weak field. In this paper, we further explore the polarization control behavior of multi- photon absorption process in the intermediate femtosecond laser field. In the weak femtosecond laser field, the second- order perturbation theory can well describe the non-resonant two-photon absorption process. However, the higher order nonlinear effect （e.g., four-photon absorption） can occur in the intermediate femtosecond laser field, and thus it is necessary to establish new theoretical model to describe the multi-photon absorption process, which includes the two-photon and four-photon transitions. Here, we construct a fourth-order perturbation theory to study the polarization control behavior of this multi-photon absorption under the intermediate femtosecond laser field excitation, and our theoretical results show that the two-photon and four-photon excitation pathways can induce a coherent interference, while the coherent interference is constructive or destructive that depends on the femtosecond laser center frequency. Moreover, the two-photon and four- photon transitions have the different polarization control efficiency, and the four-photon absorption can obtain the higher polarization control efficiency. Thus, the polarization control efficiency of the whole excitation process can be increased or decreased by properly designing the femtosecond laser field intensity and laser center frequency. These studies can provide a clear physical picture for understanding and controlling the multi-photon absorption process in the intermediate femtosecond laser field, and also can provide a theoretical guidance for the future experimental realization.

Optical absorption in asymmetric double quantum wells driven by two intense terahertz fields

Optical absorption is investigated for asymmetric double quantum wells driven by a resonant terahertz field and a varied terahertz field,both polarized along the growth direction.Rich nonlinear dynamics of the replica peak and the Autler-Townes splitting of various dressed states are systematically studied in undoped asymmetric double quantum wells by taking account of multiple factors,such as the frequency of the varied terahertz field and the strength of the resonant terahertz field.Each electron subband splits into two dressed states when the resonant terahertz field is applied in the absence of the varied terahertz field,the optical absorption spectrum shows the first-order Autler-Townes splitting of the electron subbands.When a varied terahertz field is added into the resonant system,the replica peak and the second-order Autler-Townes splitting of the dressed states near the band edge respectively emerge when the varied terahertz field is non-resonant and resonant with these dressed states.When the strength of the resonant terahertz field is increased,the first-order Autler-Townes double peaks and the replica peak in the optical absorption spectrum shift with the shifts of the dressed states.The presented results have potential applications in electro-optical devices.

Modulation of absorption manner in helicon discharges by changing profile of low axial magnetic field

The modulation of absorption manner in helicon discharge by changing the profile of low axial magnetic field is explored experimentally in this work. The experiments are carried out in Boswell-type antenna driven by 13.56-MHz power source in 0.35-Pa argon environment. The peak of the external non-uniform magnetic field （Bex） along the axis is observed in a range from 0 Gs to 250 Gs （1 Gs=10^-4 T）, where the electron density varies from 0.5×10^16 m^-3 to 9×10^16 m^-3. When Bex is located near the tube upper end sealed by a dielectric plate, or near the tube bottom end connected with a diffusion chamber, the plasmas are centralized in the tube in the former case while the strong luminance appears between the edge of the tube and the axial line in the latter case. When Bex is located in the middle of the antenna, moreover, an effective resistance （Reff） peak appears apparently with increasing magnetic field. The glow moves toward first the edge of the tube and then the two antenna legs as the magnetic field increases. The discharge in this case is caused by the absorption of Trivelpiece-Gould （TG） wave. It is suggested that Bex is located in the middle of the antenna to obtain a higher efficiency of power transfer.

Polarization and absorption principle of corona virus in the electric field

The polarization and absorption principle of corona virus in the electric field is presented. It is expressed by the mathematic differential equation based on the physical model. According to the parameters of the dipole moment of virus, the electric field force exerted by the external electric field can be calculated. According to the parameters of size, mass and elastic modular, etc., the moment of inertia of virus can be calculated. According to the viscosity of tissues, the resistant force when virus rotates can be calculated. According to the balance condition of relaxation polarization, when the drive force equals to the resistant force, the rotating or swaying frequency of virus can be calculated. According to the heat producing condition such as friction, the temperature rising of virus can be calculated. When the temperature exceeds a certain threshold, virus would be inactivated. Through the calculation, it is found that the movement type of the virus depends on the intensity and frequency of the external electric field, which are the effects of "intensity widows" and "frequency windows". It also gives approximate calculation of the temperature rising of the virus according to this model. The vitro experiment confirms the reasonability of this model. The electric fields of different densities of a certain frequency are applied to the solution of avian infectious bronchitis virus. Through the toxicity experiment of the SPF chicken embryo, it is found that the toxicity is decreased exceedingly with a certain intensity of the applied voltage. EID50 decreases from 6.70/0.2 mL to 2.66/0.2 mL. It is proved that the avian infectious bronchitis virus can be inactivated with a certain low frequency and low-density electric field.

Magnetic Field Enhancement in Ammonia-Water Absorption Refrigeration Systems

Absorption enhancement has been considered as an effective way of improving coefficient of performance (COP) of refrigeration systems and magnetic enhancement is one of these methods. A model of magnetic field enhancement in ammonia-water absorption systems is presented in this paper. A numerical model using finite difference scheme was developed based on the conservation equations and mass transport relationship. Macroscopic magnetic field force was introduced in the momentum equation. The model was validated using data obtained from the literature. Changes in the physical properties of ammonia solution while absorbing both in the direction of falling film and across its thickness were investigated. The magnetic field was found to have some positive effect on the ammonia-water falling film absorption. The results indicate that absorption performance enhancement increased with magnetic intensity. The COP of simple ammonia solution absorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0 Tesla respectively.

Variation of Two-photon Absorption Cross Sections and Optical Limiting of Compounds Induced by Static Electric Field

By numerically solving the Maxwell-Bloch equations using an iterative predictor-corrector finite-difference time-domain technique, we investigate propagating properties of a few-cycle laser pulse in a 4,4＇-bis（di-n-butylamino） stilbene （BDBAS） molecular medium when a static electric field exists. Dynamical two-photon absorption （TPA） cross sections are obtained and optical limiting （OL） behavior is displayed. The results show that when the static electric field intensity increases, the dynamical TPA cross section is enhanced and the OL behavior is improved. Moreover, both even- and odd-order harmonic spectral components are generated with existence of the static electric field because it breaks the inversion symmetry of the BDBAS molecule. This work provides a method to modulate the nonlinear optical properties of the BDBAS compounds.

Excitonic Absorption of Semiconductor Nanorings under Terahertz Fields

The optical absorption of GaAs nanorings （NRs） under adc electric field and a terahertz （THz） ac electric field applied in the plane containing the NRs is investigated theoretically. The NRs may enclose some magnetic flux in the presence of a magnetic field perpendicular to the NRs plane. Numerical calculation shows that the excitonic effects are essential to correctly describe the optical absorption in NRs. The applied lateral THz electric field, as well as the dc field leads to reduction, broadening and splitting of the exciton peak. In contrast to the presence of a dc field, significant optical absorption peak arises below the zero-field bandgap in the presence ofa THz electric field at a certain frequency. The optical absorption spectrum depends evidently on the frequency and amplitude of the applied THz field and on the magnetic flux threading the NRs. This promises potential applications of NRs for magneto-optical and THz electro-optical sensing.

Simulation of Intermediate State Absorption Enhancement in Rare-Earth Ions by Polarization Modulated Femtosecond Laser Field

We extend the third perturbation theory to study the polarization control behavior of the intermediate state absorption in Nd^（3＋）ions. The results show that coherent interference can occur between the single-photon and three-photon excitation pathways, and depends on the central frequency of the femtosecond laser field. Moreover,single-photon and three-photon absorptions have different polarization control efficiencies, and the relative weight of three-photon absorption in the whole excitation processes can increase with increasing the laser intensity.Therefore, the enhancement or suppression of the intermediate state absorption can be realized and manipulated by properly designing the intensity and central frequency of the polarization modulated femtosecond laser field.This research can not only enrich theoretical research methods for the up-conversion luminescence manipulation of rare-earth ions, but also can provide a clear physical picture for understanding and controlling multi-photon absorption in a multiple energy level system.

Dependence of Gravity Induced Absorption Changes on the Earth’s Magnetic Field as Measured during Parabolic Flight Campaigns

Various spectroscopic experiments performed on the AIRBUS ZERO G—located in Bordeaux, France—in the years 2002 to 2012 exhibit minute optical reflection/absorption changes (GIACs) as a result of gravitational changes between 0 and 1.8 g in various biological species such as maize, oats, Arabidopsis and particularly Phycomyces sporangiophores. During a flight day, the AIRBUS ZERO G conducts 31 parabolas, each of which lasts about three minutes including a period of 22 s of weightlessness. So far, we participated in 11 parabolic flight campaigns including more than 1000 parabolas performing various kinds of experiments. During our campaigns, we observed an unexplainable variability of the measuring signals (GIACs). Using GPS-positioning systems and three dimensional magnetic field sensors, these finally were traced back to the changing earth’s magnetic field associated with the various flight directions. This is the first time that the interaction of gravity and the Earth’ magnetic field in the primary induction process in living system has been observed.

Studies on Linear and Nonlinear Intersubband Optical Absorptions in a Wurtzite AlGaN/GaN Coupling Quantum Well

Based on the density matrix approach and iterative procedure, a detailed procedure for the calculation of the linear and nonlinear intersubband optical absorption coefficients is given in wurtzite GaN-based coupling quantum wells （CQWs）. The simple analytical formulas for electronic eigenstates and the linear and nonlinear optical absorption coefficients in the systems are also deduced. Numerical result on a typical A1GaN/GaN CQW shows that, the linear and nonlinear optical absorption coefficients sensitively depend on the structural parameters of the CQW system as well as the incident optics beam intensity.

Analysis on characteristics of aerosol absorption and scattering over Zhangye, China

The first China-US joint dust field experiment was carried out by Lanzhou University, Chinese Academy of Sciences, China Me- teorological Administration, and University of Maryland, the Department of Energy （DOE）, USA, from April to June, 2008. The observation sites are located at Zhangye National Climatological Observatory, Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL）, and Jingtai with the Mobile Facilities of SACOL. The measurements of Particle Soot Absorp- tion Photometer and TSI Integrating Nephelometer are used to analyze the aerosol absorption and scattering characteristics over Zhangye. The results are： the aerosol absorption, total scattering, and backscattering coefficients present similar diurnal variation trends with their bi-peaks at 08：00 and 22!00, and they are generally higher in nighttime than in daytime. Their monthly average coefficient is the highest in April, and the!l drops in succession in May and June. Frequency analysis of aerosol single scattering albedo （SSA） shows that the magnitudes＇0f SSA at 450, 550, and 700 nm are mainly within 0.7q3.9. The maximum frequency of SSA at 450 and 700 nm distribute at 0.8, and at 0.85 for 550 nm. The averages of SSA at 450, 550, and 700 nm are 0.72, 0.75, and 0.68, respectively.

化肥减量配施生物炭和秸秆对砂姜黑土区水稻产量、养分吸收和土壤碳的影响

为探讨砂姜黑土区养分资源高效管理和秸秆资源化利用方式,采用田间定位试验,连续2 a研究化肥减量配施生物炭和秸秆对该区域水稻产量、养分吸收和土壤碳的影响。试验设5个处理:①不施肥(CK);②常规施肥(100%NPK);③化肥减量20%(80%NPK);④化肥减量20%+秸秆(80%NPK+S);⑤化肥减量20%+生物炭(80%NPK+B),测定并分析水稻籽粒产量、地上部生物量、植株氮、磷、钾养分含量、土壤总有机碳(TOC)和微生物量碳(MBC)。结果显示,化肥减量20%配施生物炭或秸秆均有利于提高水稻产量和地上部生物量,且生物炭较秸秆的效果更为显著。化肥减量20%配施生物炭(80%NPK+B)处理的水稻产量和地上部生物量较100%NPK处理分别增加5.2%和4.7%,较80%NPK处理分别增加7.9%和7.2%;化肥减量20%配施秸秆(80%NPK+S)较100%NPK处理的水稻产量和地上部生物量分别增加3.4%和3.0%;80%NPK与100%NPK处理的籽粒和地上部生物量无显著差异;化肥减量20%配施生物炭显著提高了水稻地上部N、P_(2)O_(5)和K_(2)O养分累积量,较100%NPK处理分别提高了10.4%、7.2%和20.0%;化肥减量20%配施秸秆可显著提高氮、钾养分累积量,但却同时显著降低了磷素累积量;化肥减量20%配施生物炭或者秸秆,均有利于改善土壤总有机碳的累积,并且显著提高了土壤微生物量碳的含量,其中生物炭提高土壤总有机碳含量效果优于秸秆,而秸秆提高土壤微生物量碳含量效果优于生物炭。综合来看,在沿淮砂姜黑土区,化肥减量20%配施生物炭或者氮钾减量20%配施秸秆可增加或维持水稻产量,提高水稻对养分的吸收能力,利于固碳培肥。