Construction of enhanced multi-polarization and high performance electromagnetic wave absorption by self-growing ZnFe_(2)O_(4)on Cu_(9)S_(5)

The development of 3D structural composites with electromagnetic(EM)wave absorption could attenuate EM waves.Herein,magnetized flower-like Cu_(9)S_(5)/ZnFe_(2)O_(4)composites were fabricated through a multistep hydrothermal method.The crystallographic and surface phase chemical information,morphological structure,and magnetic and EM parameters of the composites were analyzed.The prepared Cu_(9)S_(5)/ZnFe_(2)O_(4)composites have multiple loss paths for EM waves and present an overall 3D flower-like structure.The Cu_(9)S_(5)/ZnFe_(2)O_(4)composites exhibit a minimum reflection loss of-54.38 dB and a broad effective absorption bandwidth of 5.92 GHz.Through magnetization,ZnFe_(2)O_(4)particles are self-assembled and grown on the surfaces of Cu_(9)S_(5).Such a modification is conducive to the generation of additional cross-linking contact sites and the effective introduction of a large number of phase interfaces,crystalline defects,special three-dimensional flower-like structures,and magneto-electrical coupling loss effects.Moreover,the synergistic effect of multiple loss strategies effectively improves EM wave absorption by the material.This work can provide a strategy for the use of magnetizationmodified sulfide composite functional materials in EM wave absorption.

Enhancement Factors in Ozone Absorption Based on the Surface Renewal Model and its Application

Based on the Danckwerts surface renewal model, a simple explicit expression of the enhancement factor in ozone absorption with a first order ozone self-decomposition and parallel second order ozonation reactions has been derived. The results are compared with our previous work based on the film theory. The 2,4-dichlorophenol destruction rate by ozonation is predicted using the enhancement factor model in this paper.

Estimation of mass transfer coefficient in ozone absorption by linear least square fitting and Simplex search methods

For physical ozone absorption without reaction,two parametric estimation methods,i.e.the common linear least square fitting and non-linear Simplex search methods,were applied,respectively,to determine the ozone mass transfer coefficient during absorption and both methods give almost the same mass transfer coefficient.While for chemical absorption with ozone decomposition reaction,the common linear least square fitting method is not applicable for the evaluation of ozone mass transfer coefficient due to the difficulty of model linearization for describing ozone concentration dissolved in water.The nonlinear Simplex method obtains the mass transfer coefficient by minimizing the sum of the differences between the simulated and experimental ozone concentration during the whole absorption process,without the limitation of linear relationship between the dissolved ozone concentration and absorption time during the initial stage of absorption.Comparison of the ozone concentration profiles between the simulation and experimental data demonstrates that Simplex method may determine ozone mass transfer coefficient during absorption in an accurate and high efficiency way with wide applicability.

Analytical Absorption Cross-Section for Photon by a Hydrogen 2s Atom

We calculate the absorption cross-section for photon by a hydrogen 2s atom using the quantum-classical approximation for the total photo cross-section of many electron atoms. With the application of the first-order term of the Baker Hausdorf expansion, the absorption cross-section for the hydrogen 2s atom decreases to a minimum, the Cooper paJr minimum, at low photon energy. Such a minimum is absent in the exact absorption cross-section for photon by a hydrogen 2s atom. We have extended the calculation for the absorption cross-section of the hydrogen 2s atom using the quantum-classical approximation for the total photo cross-section of many electron to include the second-order term of the Baker-Hausdorf expansion and observed a great reduction in the dip associated with the Cooper pair minimum at the zero crossing.

Ultrafast Laser Energy Density and Retinal Absorption Cross-Section Determination by Saturable Absorption Measurements

Laser pulse nonlinear transmission measurements through saturable absorbers of known absorption parameters allow the measurement of their energy density. On the other hand, nonlinear transmission measurements of laser pulses of known energy density through absorbing media allow their absorption parameter determination. The peak energy density w0P of second harmonic pulses of a mode-locked titanium sapphire laser at wavelength λP = 400 nm is determined by nonlinear energy transmission measurement TE through the dye ADS084BE (1,4-bis(9-ethyl-3-car-bazovinylene)-2-methoxy-5-(2’-ethyl-hexyloxy)-benzene) in tetrahydrofuran. TE(w0P) calibration curves are calculated for laser pulse peak energy density reading w0P from measured pulse energy transmissions TE. The ground-state absorption cross-section σP and the excited-state absorption cross-section σex at λP, and the number density N0 of the retinal Schiff base isoform RetA in pH 7.4 buffer of the blue-light adapted recombinant rhodopsin fragment of the histidine kinase rhodopsin HKR1 from Chlamydomonas reinhardtii were determined by picosecond titanium sapphire second harmonic laser pulse energy transmission measurement TE through RetA as a function of laser input peak energy density w0P. The complete absorption cross-section spectrum

Optical Path Length,Temperature,and Wavelength Effects Simulation on Ozone Gas Absorption Cross Sections towards Green Communications

Ozone is a green house gas. Ozone absorption cross sections have been reported with discrepancies and inconsistencies. In this paper, simultaneous effects of the optical path length and temperature variations on ozone gas absorption cross sections are investigated at different wavelengths. HITRAN 2012, the latest available line list on spectralcalc.com simulator, is used in this study to simulate ozone gas absorption cross sections in relation to the simultaneous effects of the optical path length and temperature at the wavelengths of 603 nm and 575 nm. Results obtained for gas cells with the optical path length from 10 cm to 120 cm show that the decrease in temperatures from 313 K to 103 K results in the increase in ozone gas absorption cross sections. At wavelengths of 603 nm and 575 nm, the percentage increase of ozone gas absorption cross sections is 1.22% and 0.71%, respectively. Results obtained in this study show that in the visible spectrum, at constant pressure, ozone gas absorption cross sections are dependent on the temperature and wavelength but do not depend on the optical path length. Analysis in this work addresses discrepancies in ozone gas absorption cross sections in relation to the temperature in the visible spectrum; thus, the results can be applied to get optimal configuration of high accuracy ozone gas sensors.

Multifunctional MXene/C Aerogels for Enhanced Microwave Absorption and Thermal Insulation

Two-dimensional transition metal carbides and nitrides(MXene)have emerged as promising candidates for microwave absorption(MA)materials.However,they also have some drawbacks,such as poor impedance matching,high self-stacking tendency,and high density.To tackle these challenges,MXene nanosheets were incorporated into polyacrylonitrile(PAN)nanofibers and subsequently assembled into a three-dimensional(3D)network structure through PAN carbonization,yielding MXene/C aerogels.The 3D network effectively extends the path of microcurrent transmission,leading to enhanced conductive loss of electromagnetic(EM)waves.Moreover,the aerogel’s rich pore structure significantly improves the impedance matching while effectively reducing the density of the MXenebased absorbers.EM parameter analysis shows that the MXene/C aerogels exhibit a minimum reflection loss(RL_(min))value of−53.02 dB(f=4.44 GHz,t=3.8 mm),and an effective absorption bandwidth(EAB)of 5.3 GHz(t=2.4 mm,7.44–12.72 GHz).Radar cross-sectional(RCS)simulations were employed to assess the radar stealth effect of the aerogels,revealing that the maximum RCS reduction value of the perfect electric conductor covered by the MXene/C aerogel reaches 12.02 dB m^(2).In addition to the MA performance,the MXene/C aerogel also demonstrates good thermal insulation performance,and a 5-mm-thick aerogel can generate a temperature gradient of over 30℃ at 82℃.This study provides a feasible design approach for creating lightweight,efficient,and multifunctional MXene-based MA materials.

Two-photon absorption of FAPbBr_(3) perovskite nanocrystals

Perovskite nanocrystals(NCs) with high two-photon absorption(TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microscopy. Among various perovskite materials, FAPbBr_(3) NCs show a better development prospect due to their excellent stability. However, there are few reports on their nonlinear optical properties. In this work, the nonlinear optical behavior of FAPbBr_(3) NCs is studied.The methods of multiphoton absorption photoluminescence saturation and open aperture Z-scan technique were applied to determine the TPA cross-section of FAPbBr_(3)NCs, which was around 2.76 × 10^(-45)cm^(4)·s·photon^(-1) at 800 nm. In addition,temperature-dependent photoluminescence induced by TPA was investigated, and the small longitudinal optical phonon energy and electron–phonon coupling strength was obtained, which confirm the weak Pb–Br interaction. Meanwhile, it is found that the exciton binding energy in FAPbBr_(3) NCs was 69.668 me V, which may be ascribed to the strong hydrogen bond interaction. It is expected that our findings will promote the application of FAPbBr_(3) NCs in optoelectronic devices.

Analysis of Absorption and Reaction Kinetics in the Oxidation of Organics in Effluents Using a Porous Electrode Ozonator

A novel electrode design for the in situ generation of ozone in the reaction zone of a tubular reactor is described in this work.The ozone generator uses a porous inner electrode tube in the corona discharge assembly,and the ozone generated around the outer periphery of the porous tube diffuses into the tubular reactor and reacts with the contaminants in the fluid that is being treated.A mathematical model that includes absorption and second order reaction in the film is developed to describe ozonation kinetics of a contaminant dye in the tubular reactor.The model describes the experimental data for dye decolorization,oxidation byproducts,dissolved ozone,and ozone gas concentrations well.Model analysis indicates that the fast dye decolorization reaction occurs partly in the liquid film and partly in the bulk fluid.The model can be used in the selection of appropriate gas-liquid contactors for efficient oxidation of contaminants in effluents.

Environmentally Friendly and Multifunctional Shaddock Peel-Based Carbon Aerogel for Thermal-Insulation and Microwave Absorption

Eco-friendly electromagnetic wave absorbing materials with excellent thermal infrared stealth property,heat-insulating ability and compression resistance are highly attractive in practical applications.Meeting the aforesaid requirements simultaneously is a formidable challenge.Herein,ultra-light carbon aerogels were fabricated via fresh shaddock peel by facile freeze-drying method and calcination process,forming porous network architecture.With the heating platform temperature of 70℃,the upper surface temperatures of the as-prepared carbon aerogel present a slow upward trend.The color of the sample surface in thermal infrared images is similar to that of the surroundings.With the maximum compressive stress of 2.435 kPa,the carbon aerogels can provide favorable endurance.The shaddock peel-based carbon aerogels possess the minimum reflection loss value(RLmin)of−29.50 dB in X band.Meanwhile,the effective absorption bandwidth covers 5.80 GHz at a relatively thin thickness of only 1.7 mm.With the detection theta of 0°,the maximum radar cross-sectional(RCS)reduction values of 16.28 dB m^(2) can be achieved.Theoretical simulations of RCS have aroused extensive interest owing to their ingenious design and time-saving feature.This work paves the way for preparing multi-functional microwave absorbers derived from biomass raw materials under the guidance of RCS simulations.

Absorption of NO_x into Nitric Acid Solution in Rotating Packed Bed

Absorption of NOx into nitric acid solutions was studied in the presence of ozone by using a rotating packed bed(RPB) contactor.The influences of operating parameters,such as high gravity number,amount of ozone,gas velocity,liquid spray density and inlet concentration of NOx,on the removal efficiency of NOx were investigated,among which the high gravity number and ozone amount are more important.Ozone was introduced to oxidize HNO2 to HNO3 to prevent the decomposition of HNO2 in the liquid phase.The high gravity number presents the effective external force for enhancing the mass transfer of ozone from gas phase to liquid phase.Under the experimental condition,the removal efficiency of NOx is higher than 90%and the concentration of nitric acid product exceeds 45%.

Ultralight Magnetic and Dielectric Aerogels Achieved by Metal-Organic Framework Initiated Gelation of Graphene Oxide for Enhanced Microwave Absorption

The development of a convenient methodology for synthesizing the hierarchically porous aerogels comprising metal–organic frameworks(MOFs)and graphene oxide(GO)building blocks that exhibit an ultralow density and uniformly distributed MOFs on GO sheets is important for various applications.Herein,we report a facile route for synthesizing MOF/reduced GO(rGO)aerogels based on the gelation of GO,which is directly initiated using MOF crystals.Free metal ions exposed on the surface of MIL-88A nanorods act as linkers that bind GO nanosheets to a three-dimensional porous network via metal–oxygen covalent or electrostatic interactions.The MOF/rGOderived magnetic and dielectric aerogels Fe_(3)O_(4)@C/rGO and Ni-doped Fe_(3)O_(4)@C/rGO show notable microwave absorption(MA)performance,simultaneously achieving strong absorption and broad bandwidth at low thickness of 2.5(-58.1 dB and 6.48 GHz)and 2.8 mm(-46.2 dB and 7.92 GHz)with ultralow filling contents of 0.7 and 0.6 wt%,respectively.The microwave attenuation ability of the prepared aerogels is further confirmed via a radar cross-sectional simulation,which is attributed to the synergistic effects of their hierarchically porous structures and heterointerface engineering.This work provides an effective pathway for fabricating hierarchically porous MOF/rGO hybrid aerogels and offers magnetic and dielectric aerogels for ultralight MA.

Absorption,quenching,and enhancement by tracer in acetone/toluene laser-induced fluorescence

To measure the equivalent ratio distribution of the two-stage lean premixed(DLP)flame,we propose using acetone/toluene planar laser-induced fluorescence(PLIF)technology to simultaneously measure the concentrations of the two components.Appropriate excitation laser wavelength and filters are used to assess the influence of acetone and toluene on each other’s fluorescence signal at room temperature.Experimental results show that acetone has a strong absorption effect on toluene’s fluorescence signal,the effective absorption cross-section is 5.77×10-20 cm-2.Acetone has an obvious quenching effect on the toluene fluorescence signal,and the Stern–Volmer coefficient is 0.50 kPa-1.The collisions between the molecules of toluene and acetone will lead to the enhancement of the fluorescence signal of acetone,and the enhancement coefficient is exponential with the acetone’s concentration.The quantitative relationship between the fluorescence intensity and the concentrations of the two tracers is obtained by establishing the photophysical model of toluene and acetone’s fluorescence signals.

Return Signal Intensity Ratio Modulates the Impact of Background Signal on Ozone DIAL Night Time Measurement in the Troposphere

This paper discusses the uncertainty of ozone differential absorption lidar (DIAL) measurements due to the impact of background signal. The impact of background signal on ozone concentration profiles is proportional to the background intensity and the ratio of return signal intensities at “on” and “off” wavelength ( ) (hereinafter we call it the return signal intensity ratio). Analysis suggests that an appropriate return signal intensity ratio can make the impact of background signal very small, negligible. The simulations based on the analysis coincide with the experimental results. The experimental results show that the impact of background signal is negligible at an appropriate return signal intensity ratio of 0.96 at wavelength pair (280,285 nm). In case of unknown background intensity, we can adjust the laser pulse energy levels at the two wavelengths to obtain an appropriate return signal intensity ratio on the oscilloscope to suppress the impact of background signal and ensure the accuracy of night time ozone measurements.

The Effect of Greenhouse Ozone on Human

The article compares the IR absorption spectra of the gases of the Earth’s atmosphere with frequencies, close to the frequency of the maximum of thermal radiation of human. It is shown that such a gas is ozone. Being in the transparency window of the atmosphere, it emits absorbed thermal radiation from the Earth. This radiation, in turn, gets to maximum heat absorption (radiation) of a human, and being with it in resonance, fuels him with energy. In larger cities this nourishment is weakened because of the smog due to the strong scattering of Earth radiation and ozone. Thus, the “greenhouse ozone” as a natural source of infrared radiation has beneficial effect on human.

Microscopic morphology independence in linear absorption cross-section of CsPbBr_(3)nanocrystals

Multiple morphologies of colloidal perovskite nanocrystals(NCs)diversify their optical and electronic properties.Among them,the linear absorption cross-section(σ)is a primary parameter to determine their intrinsic photophysical features,and consequently,application potential.Herein,three morphologies of all-inorganic hybrid colloidal perovskite CsPbBr_(3)NCs,nanocubes(NBs),nanoplatelets(NLs),and nanowires(NWs),were targeted,and their linearσvalues were obtained through femtosecond transient absorption(TA)spectroscopy analysis.At high excitation energy well above the bandgap,theσper particle of all CsPbBr3 NCs linearly increased with the particle volume(VNC)regardless of the morphology with the value ofσ400=9.45×10^(4)cm^(−1)×VNC(cm^(2)).Density functional theory(DFT)calculation confirmed the negligible influence of shapes on the optical selection rules.The Einstein spontaneous emission coefficients calculated from theσvalues define the intrinsic radiative recombination rate.However,reduced size dependence is observed when the excitation energy is close to the bandgap(i.e.,at 460 nm)with the value ofσ460=2.82×10^(8)cm0.65×(VNC)0.45(cm^(2)).This should be ascribed to the discrete energy levels as well as lower density of states close to the band edge for perovskite NCs.These results provide in-depth insight into the optical characteristics for perovskite NCs.

臭氧激光雷达技术及应用研究进展

差分吸收臭氧激光雷达是完善光化学立体监测体系的重要技术,因其高时空分辨率的廓线探测优势而得以迅速发展,目前已被广泛应用于对流层臭氧浓度的遥感探测。阐述了臭氧激光雷达的原理,归纳总结了雷达系统及关键技术的国内外最新研究进展,梳理了臭氧激光雷达在环境领域的应用现状,并基于我国城市臭氧污染问题现状和管理需求,初步探索设计了臭氧激光雷达监测网络业务应用的整体框架。指出了臭氧激光雷达技术及应用中存在厂家众多但缺乏统一的技术规范和行业标准,数据质量及准确性有待提高,与标准分析方法产生数据的可比性较差等不足之处;提出了核心部件国产化,系统小型化、自动化及商用化,多平台以及与其他监测方式联用等发展趋势。

臭氧吸收截面关键参数研究进展

近期,国际计量局(BIPM)修订臭氧吸收截面的新参数,这是该参数在沿用40余年后的首次变更。修订后的臭氧吸收截面值为1.1329×10^(–17)cm^(2)·molecule^(–1),相对标准不确定度0.31%,相对于现行参数,数值上减小了1.23%,不确定度减小到七分之一。BIPM建议新参数于2024年开始在全球推广使用。臭氧吸收截面系数是当前国内外臭氧量值溯源体系中的关键计量参数,该参数的修订将直接影响臭氧气体浓度的测量值及其不确定度,进而影响全球的臭氧浓度监测结果。我国也同样面临该参数的修订问题,为便于相关工作的推进,该文介绍臭氧吸收截面的研究历程,阐述本次修订的背景和意义,重点讨论气相滴定法与分压法这两种臭氧吸收截面的核心研究方法的原理与技术差异,深入分析这两种方法的技术现状,以期为我国臭氧检测和量值溯源工作的进一步国际化接轨打下坚实基础。

利用激光雷达探测潍坊市夏季臭氧分布特征

为了研究潍坊市夏季臭氧的分布特征,使用差分吸收激光雷达在潍坊市进行观测,分析了晴天和雨天臭氧分布的差别,并统计了无降水日臭氧的垂直分布和日变化特征。结果表明:降水发生前强烈的对流运动和大风会使对流臭氧层变厚,臭氧浓度变低;降水发生在一天中的不同时段,对臭氧污染的影响差异很大;无降水日对流臭氧层主要分布在1500 m以下,呈现白天高、夜晚低的日变化特征,高浓度值常出现在12~18时;在垂直结构上呈现分层的特征,其中,300~500 m高度的臭氧浓度随着高度的增加而增大,且在500 m附近达到极大值,该高度和米散射激光雷达探测的边界层高度基本一致;1500 m高度各个时段的臭氧浓度趋于一致,且自该高度往上臭氧无明显日变化特征,可将该层臭氧浓度作为臭氧预报的大气背景值。

基于协相关性和傅里叶变换-差分吸收光谱法的臭氧浓度在线测量研究

采用协相关性和傅里叶变换-差分吸收光谱法对臭氧浓度进行了在线测量研究。先创建1套能够用于实验室在线监测臭氧浓度的发生装置,其测量精度可达到0.1×10^(-6);然后应用协相关性对测得的多组背景谱和吸收谱进行分析与计算,得到最优背景谱和吸收谱,进而准确反演臭氧吸收截面,优化臭氧浓度的计算过程;最后采用傅里叶变换-差分吸收光谱法以及逆傅里叶变换法在320~350 nm波段反演臭氧浓度,成功消除系统噪声的干扰,得到反演臭氧浓度的二次方程。