Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ra...Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ray Photoelectron emission spectroscopy(HAXPES)and microscopy(HAXPEEM)as well as microscopic X-ray absorption spectroscopy(μ-XAS)techniques.The results reveal the inhomogeneity in the oxide films on the micron-sized Cr_(2)N-and VN-type particles,while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600℃.The oxide film formed on Cr_(2)N-type particles is rich in Cr_(2)O_(3) compared with that on the martensite matrix and VN-type particles.With the increase of tempering temperature,Cr_(2)O_(3) formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.展开更多
CO_2 emitted from ship exhaust is one of the major sources of atmospheric pollution. In order to reduce ship CO_2 emissions, this paper comes up with the idea of recovering CO_2 from ship exhaust by Na OH solution and...CO_2 emitted from ship exhaust is one of the major sources of atmospheric pollution. In order to reduce ship CO_2 emissions, this paper comes up with the idea of recovering CO_2 from ship exhaust by Na OH solution and improves the absorption rate by adding Ca O solid particles. The effect mechanism of Ca O solid particles on CO_2 absorption efficiency is analyzed in detail, and the mathematical model is deduced and the Ca O enhancement factor is calculated through experiments. Experiment result demonstrates that the effect of CaO solid particles on the absorption of CO_2 in alkali solution is significant. The absorption rate of pure CO_2 gas,the simulated ship exhaust gas and 6135 AZG marine diesel engine emission can be increased by 10%, 15.85% and10.30%, respectively. So it can be seen that CaO solid particles play an important role in improving the absorption efficiency of ship CO_2 emission.展开更多
A membrane-based gas absorption （MGA） process was evaluated for the removal of volatile organic compounds （VOCs） based on C6H6/N2 mixture. The absorption of C6H6 from a C6H6/N2 mixture was investigated using a hyd...A membrane-based gas absorption （MGA） process was evaluated for the removal of volatile organic compounds （VOCs） based on C6H6/N2 mixture. The absorption of C6H6 from a C6H6/N2 mixture was investigated using a hydrophobic polypropylene hollow fiber membrane contactor and the aqueous solution of N-formyl morpholine （NFM） as absorbent. The effects of various factors on the overall mass transfer coefficient was investigated. The experimental results showed that the removal efficiency of C6H6 could reach 99.5% in present studied system. A mathematical model based on resistance-in-series concept was presented to predict the value of overall mass transfer coefficient. The average error between the predicted and experimental values is 7.9%. In addition, conventional packed columns for VOCs removal was also evaluated for comparison.展开更多
Absorption and refraction of the inner transition F2 ←→F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1←→F3 and F2←→F4 are resonantly interacted with dr...Absorption and refraction of the inner transition F2 ←→F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1←→F3 and F2←→F4 are resonantly interacted with drive field with frequency ωc and Rabi frequency Ωc, and saturation field with ωs and Ωs, respectively. For the suitable Rabi frequencies Ωc and Ωs, we obtain the Mellow absorption spectrum of probe field. The reason is that the drive field excites the atom to the upper level F3 and simultaneously the saturation field takes the atom out of the lower level F2, leading to the stimulated emission. Meanwhile, due to the dynamic energy splitting induced by the drive and saturation fields, the two- and four-peaked absorption spectra are observed. At the zero off-resonance detuning of probe field, we also find the transfer of dispersion from negative to positive with an increment of Ωs. Finally, the refractive index enhancement is predicted for a wide spectral region.展开更多
The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The m...The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The measured two photon absorption coefficientβwas intensity dependent,inferring that reverse saturated absorption(RSA)is also relevant dur-ing high intensity excitation in ZnSe.At low peak intensity I<5 GW cm^(-2),we findβ=3.5 cm GW^(-1) at 775 nm.The spec-tral properties of the broad blueish two-photon induced fluorescence(460 nm-500 nm)was studied,displaying self-ab-sorption near the band edge while the upper state lifetime was measured to be τ_(e)~3.3 ns.Stimulated emission was ob-served when pumping a 0.5 mm thick polycrystalline ZnSe sample within an optical cavity,confirmed by significant line narrowing fromΔλ=11 nm(cavity blocked)toΔλ=2.8 nm at peak wavelength λ_(p)=475 nm while the upper state life-time also decreased.These results suggest that with more optimum pumping conditions and crystal cooling,polycrystal-line ZnSe might reach lasing threshold via two-photon pumping atλ=775 nm.展开更多
A CO_(2) infrared remote sensing system based on the algorithm of weighting function modified differential optical absorption spectroscopy(WFM-DOAS) is developed for measuring CO_(2) emissions from pollution sources. ...A CO_(2) infrared remote sensing system based on the algorithm of weighting function modified differential optical absorption spectroscopy(WFM-DOAS) is developed for measuring CO_(2) emissions from pollution sources. The system is composed of a spectrometer with band from 900 nm to 1700 nm, a telescope with a field of view of 1.12?, a silica optical fiber, an automatic position adjuster, and the data acquisition and processing module. The performance is discussed,including the electronic noise of the charge-coupled device(CCD), the spectral shift, and detection limits. The resolution of the spectrometer is 0.4 nm, the detection limit is 8.5 × 10^(20)molecules·cm^(-2), and the relative retrieval error is < 1.5%.On May 26, 2018, a field experiment was performed to measure CO_(2) emissions from the Feng-tai power plant, and a twodimensional distribution of CO_(2) from the plume was obtained. The retrieved differential slant column densities(dSCDs)of CO_(2) are around 2 × 10^(21) molecules·cm^(-2) in the unpolluted areas, 5.5 × 10^(21)molecules·cm^(-2) in the plume locations most strongly affected by local CO_(2) emissions, and the fitting error is less than 2 × 10^(20)molecules·cm^(-2), which proves that the infrared remote sensing system has the characteristics of fast response and high precision, suitable for measuring CO_(2) emission from the sources.展开更多
The absorption and emission spectra, as well as the photolysis mechanism of p-phenylbenzoyl methanthiol in methanol and in gas phase were elucidated in detail based on the molecular structures of the ground states, ex...The absorption and emission spectra, as well as the photolysis mechanism of p-phenylbenzoyl methanthiol in methanol and in gas phase were elucidated in detail based on the molecular structures of the ground states, excited states and their spectroscopic characters. The TD-M062 X calculations demonstrate that the S_1 state in gas phase will decompose into SH and p-phenylbenzoyl radical via a barrierless process, but the T_1 and T_2 do not photolyze. By adding 1 and 2 methanol molecules onto p-phenylbenzoyl methanthiol, the CPCM model can perfectly describe the solvation effects of methanol. Methanol may stabilize the excitation states, but also protects the resulting radical products from recombination.展开更多
Burners of metal halide lamps used for illumination are generally made of polycrystalline alumina ceramic （PCA） which is translucent to visible light. We show that the difficulty of selecting a line of sight through...Burners of metal halide lamps used for illumination are generally made of polycrystalline alumina ceramic （PCA） which is translucent to visible light. We show that the difficulty of selecting a line of sight through the lamp prevents the use of optical emission diagnostic. X-rays photons are mainly absorbed and not scattered by PCA. Absorption by mercury atoms contributing to the discharge allowed us to determine the density of mercury in the lamp. By comparing diagnostic methods, we put in evidence the difficulty of taking into account the scattering of light mathematically.展开更多
We report on the discovery of unusual broad absorption lines(BALs)in the bright quasar SDSS J075133.35+134548.3 at z~1,using archival and newly obtained optical and NIR spectroscopic data.The BALs are detected reliabl...We report on the discovery of unusual broad absorption lines(BALs)in the bright quasar SDSS J075133.35+134548.3 at z~1,using archival and newly obtained optical and NIR spectroscopic data.The BALs are detected reliably in HeⅠ*λ3889,HeⅠ*λ10830 and tentatively in AlⅢ,MgⅡ.These BALs show complex velocity structures consisting of two major components:a high-velocity component(HV),with a blueshifted velocity range ofΔv_(HV)~9300--3500 km s^(-1),which can be reliably detected in HeⅠ*λ10830,and tentatively in AlⅢand MgⅡ,whereas it is undetectable in HeⅠ*λ3889;and a low-velocity component(LV),withΔv_(LV)~3500--1800 km s^(-1),is only detected in HeⅠ*λ3889 and HeⅠ*λ10830.With the BALs from different ions,the HV outflowing gas can be constrained to have a density of nH~10^(10.3)-10^(11.4) cm^(-3),a column density of NH~10^(21) cm^(-2)and an ionization parameter of U~10^(-1.83)-10^(-1.72);inferring a distance of RHV~0.5 pc from the central continuum source with a monochromatic luminosityλLλ(5100)=7.0×10^(45)erg s^(-1)at 5100 A.This distance is remarkably similar to that of the normal broad line region(BLR)estimated from reverberation experiments,suggesting association of the BLR and the HV BAL outflowing gas.Interestingly,a blueshifted component is also detected in AlⅢand MgⅡbroad emission lines(BELs),and the AlⅢ/MgⅡof such a BEL component can be reproduced by the physical parameters inferred from the HV BAL gas.The LV BAL gas likely has a larger column density,a higher ionization level and hence a smaller distance than the HV BAL gas.Further spectroscopy with a high S/N ratio and broader wavelength coverage is needed to confirm this to shed new light on the possible connection between BALs and BELs.展开更多
A general relation between the total absorption and emission probabilities for nuclei in thermal equilibrium at a finite temperature is derived,and its relevance to giant resonances built on nuclear excited states dis...A general relation between the total absorption and emission probabilities for nuclei in thermal equilibrium at a finite temperature is derived,and its relevance to giant resonances built on nuclear excited states discussed.展开更多
The vacuum ultraviolet absorption and emission spectra of rare-gas vander Waals molecules were observed.A large broadening of at least 240Åof Xe first resonance absorption line was obtained at cell presgure 4 atm...The vacuum ultraviolet absorption and emission spectra of rare-gas vander Waals molecules were observed.A large broadening of at least 240Åof Xe first resonance absorption line was obtained at cell presgure 4 atm.Strong continuous emission of heavier rare gases at 1300-3000Åwas obtained using self-triggered condensed discharge in aπ-shaped quartz discharge tube.展开更多
In some events, weak fast solar bursts （near the level of the quiet Sun） were observed in the background of numerous spikes in emission and absorption. In such a case, the background contains the noise signals of th...In some events, weak fast solar bursts （near the level of the quiet Sun） were observed in the background of numerous spikes in emission and absorption. In such a case, the background contains the noise signals of the receiver. In events on 2005 September 16 and 2002 April 14, the solar origin of fast bursts was confirmed by simultaneous recording of the bursts at several remote observatories. The noisy background pixels in emission and absorption can be excluded by subtracting a higher level of continuum when constructing the spectra. The wavelet spectrum, noisy pro- files in different polarization channels and a spectrum with continuum level greater than zero demonstrates the noisy character of pixels with the lowest levels of emission and absorption. Thus, in each case, in order to judge the solar origin of all spikes, it is necessary to determine the level of continuum against the background of which the solar bursts are observed. Several models of microwave spikes are discussed. The electron cyclotron maser emission mechanism runs into serious problems with the in- terpretation of microwave millisecond spikes： the main obstacles are too high values of the magnetic field strength in the source （Pe 〈 uB）. The probable mechanism is the interaction of plasma Langmuir waves with ion-sound waves （l ＋ s → t） in a source related to shock fronts in the reconnection region.展开更多
Formamidinium lead bromide(FAPbBr_(3))nanocrystals(NCs)have been considered to be a good optoelectronic material due to their pure green emission,excellent stability and superior carrier transport characteristics.Howe...Formamidinium lead bromide(FAPbBr_(3))nanocrystals(NCs)have been considered to be a good optoelectronic material due to their pure green emission,excellent stability and superior carrier transport characteristics.However,two-photon pumped amplified spontaneous emission(ASE)and the corresponding nonlinear optical properties of FAPbBr_(3) NCs are scarcely revealed.Herein,we synthesized colloidal FAPbBr_(3) NCs with different sizes by changing the molar ratio of FABr/PbBr_(2) in the precursor solution,using ligand assisted precipitation(LARP)technology at room temperature.Photoluminescence(PL)and time resolved photoluminescence(TRPL)spectroscopy were measured to characterize their ASE properties.And their nonlinear optical properties were studied through the Zscan technique and the two-photon excited fluorescence method.The stimulated emission properties including oneand two-photon pumped ASE have been realized from FAPbBr_(3) NCs.With large two-photon absorption coefficient(0.27 cm/GW)and high non-linear absorption cross-section(7.52×10^(5) GM),ASE with threshold as low as 9.8μJ/cm^(2) and 487μJ/cm^(2) have been obtained from colloidal FAPbBr_(3) NCs using one-and two-photon excitations.These results indicate that as a new possible green-emitting frequency-upconversion material with low thresholds,FAPbBr_(3) NCs hold great potential in the development of high-performance two-photon pump lasers.展开更多
To protect environment, and to comply with the IMO＇s （International Maritime Organization） newest regulations about ship＇s SOx emission. This thesis illustrates a closed recycling absorb system based on NaOH solut...To protect environment, and to comply with the IMO＇s （International Maritime Organization） newest regulations about ship＇s SOx emission. This thesis illustrates a closed recycling absorb system based on NaOH solution recycling particularly for SOx onboard. The goal is to use NaOH solution to absorb SOx, and reduce the damage the ships made towards environment. The thesis analyzes the main features that could influence the absorption of SOx on board, and the precipitations during the experiment. To reveal that NaOH solution is very highly effective and economic in absorption of SOx on ships by this experiment, and to set a theoretical basic fundamental for future application of alkali solution recycling absorption system for SOx.展开更多
A theoretical approach based on differential radiative transport is proposed to quantitatively analyze the self- absorption and reemission effects on the emission spectrum for right angle excitation-detection photolum...A theoretical approach based on differential radiative transport is proposed to quantitatively analyze the self- absorption and reemission effects on the emission spectrum for right angle excitation-detection photoluminescence mea- surements, and the wavelength dependence of the reemission effect is taken into account. Simulations and experiments are performed using rhodamine 6G solutions in ethanol as model samples. It is shown that the self-absorption effect is the dominant effect on the detected spectrum by inducing pseudo red-shift and reducing total intensity; whereas the reemission effect partly compensates for signal decrease and also results in an apparent signal gain at the wavelengths without ab- sorption. Both effects decrease with the decrease in the sample concentration and the propagation distance of the emission light inside the sample. We therefore suggest that diluted solutions are required for accurate photoluminescence spectrum measurements and photoluminescence-based measurements.展开更多
Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,how...Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,however,constrain their delicate constructions.Herein,an innovative alternative is proposed:carrageenan-assistant cations-regulated(CACR)strategy,which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon matrix.This unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction,benefiting the delicate construction of defects-rich heterostructures in M_(x)S_(y)/carbon composites(M-CAs).Impressively,these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and,simultaneously,induct local asymmetry of electronic structure to evoke large dipole moment,ultimately leading to polarization coupling,i.e.,defect-type interfacial polarization.Such“Janus effect”(Janus effect means versatility,as in the Greek two-headed Janus)of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first time.Consequently,the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm,compared to sulfur vacancies-free CAs without any dielectric response.Harnessing defects-rich heterostructures,this one-pot CACR strategy may steer the design and development of advanced nanomaterials,boosting functionality across diverse application domains beyond electromagnetic response.展开更多
Developing advanced stealth devices to cope with radar-infrared(IR)fusion detection and diverse application scenarios is increasingly demanded,which faces significant challenges due to conflicting microwave and IR clo...Developing advanced stealth devices to cope with radar-infrared(IR)fusion detection and diverse application scenarios is increasingly demanded,which faces significant challenges due to conflicting microwave and IR cloaking mechanisms and functional integration limitations.Here,we propose a multiscale hierarchical structure design,integrating wrinkled MXene IR shielding layer and flexible Fe_(3)O_(4)@C/PDMS microwave absorption layer.The top wrinkled MXene layer induces the intensive diffuse reflection effect,shielding IR radiation signals while allowing microwave to pass through.Meanwhile,the permeable microwaves are assimilated into the bottom Fe_(3)O_(4)@C/PDMS layer via strong magneto-electric synergy.Through theoretical and experimental optimization,the assembled stealth devices realize a near-perfect stealth capability in both X-band(8–12 GHz)and long-wave infrared(8–14μm)wavelength ranges.Specifically,it delivers a radar cross-section reduction of−20 dB m^(2),a large apparent temperature modulation range(ΔT=70℃),and a low average IR emissivity of 0.35.Additionally,the optimal device demonstrates exceptional curved surface conformability,self-cleaning capability(contact angle≈129°),and abrasion resistance(recovery time≈5 s).This design strategy promotes the development of multispectral stealth technology and reinforces its applicability and durability in complex and hostile environments.展开更多
Gradient magnetic heterointerfaces have injected infinite vitality in optimizing impedance matching,adjusting dielectric/magnetic resonance and promoting electromagnetic(EM)wave absorption,but still exist a significan...Gradient magnetic heterointerfaces have injected infinite vitality in optimizing impedance matching,adjusting dielectric/magnetic resonance and promoting electromagnetic(EM)wave absorption,but still exist a significant challenging in regulating local phase evolution.Herein,accordion-shaped Co/Co_(3)O_(4)@N-doped carbon nanosheets(Co/Co_(3)O_(4)@NC)with gradient magnetic heterointerfaces have been fabricated via the cooperative high-temperature carbonization and lowtemperature oxidation process.The results indicate that the surface epitaxial growth of crystal Co_(3)O_(4) domains on local Co nanoparticles realizes the adjustment of magnetic-heteroatomic components,which are beneficial for optimizing impedance matching and interfacial polarization.Moreover,gradient magnetic heterointerfaces simultaneously realize magnetic coupling,and long-range magnetic diffraction.Specifically,the synthesized Co/Co_(3)O_(4)@NC absorbents display the strong electromagnetic wave attenuation capability of−53.5 dB at a thickness of 3.0 mm with an effective absorption bandwidth of 5.36 GHz,both are superior to those of single magnetic domains embedded in carbon matrix.This design concept provides us an inspiration in optimizing interfacial polarization,regulating magnetic coupling and promoting electromagnetic wave absorption.展开更多
Currently,the demand for electromagnetic wave(EMW)absorbing materials with specific functions and capable of withstanding harsh environments is becoming increasingly urgent.Multi-component interface engineering is con...Currently,the demand for electromagnetic wave(EMW)absorbing materials with specific functions and capable of withstanding harsh environments is becoming increasingly urgent.Multi-component interface engineering is considered an effective means to achieve high-efficiency EMW absorption.However,interface modulation engineering has not been fully discussed and has great potential in the field of EMW absorption.In this study,multi-component tin compound fiber composites based on carbon fiber(CF)substrate were prepared by electrospinning,hydrothermal synthesis,and high-temperature thermal reduction.By utilizing the different properties of different substances,rich heterogeneous interfaces are constructed.This effectively promotes charge transfer and enhances interfacial polarization and conduction loss.The prepared SnS/SnS_(2)/SnO_(2)/CF composites with abundant heterogeneous interfaces have and exhibit excellent EMW absorption properties at a loading of 50 wt%in epoxy resin.The minimum reflection loss(RL)is−46.74 dB and the maximum effective absorption bandwidth is 5.28 GHz.Moreover,SnS/SnS_(2)/SnO_(2)/CF epoxy composite coatings exhibited long-term corrosion resistance on Q235 steel surfaces.Therefore,this study provides an effective strategy for the design of high-efficiency EMW absorbing materials in complex and harsh environments.展开更多
With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite h...With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.展开更多
基金supported by the Vinnova(project number 2020-03778)supported by the Swedish Research Council(Vetenskapsradet,project number 2021-04157).
文摘Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ray Photoelectron emission spectroscopy(HAXPES)and microscopy(HAXPEEM)as well as microscopic X-ray absorption spectroscopy(μ-XAS)techniques.The results reveal the inhomogeneity in the oxide films on the micron-sized Cr_(2)N-and VN-type particles,while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600℃.The oxide film formed on Cr_(2)N-type particles is rich in Cr_(2)O_(3) compared with that on the martensite matrix and VN-type particles.With the increase of tempering temperature,Cr_(2)O_(3) formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.
基金the Shanghai Science and Technology Committee(No.17170712100)
文摘CO_2 emitted from ship exhaust is one of the major sources of atmospheric pollution. In order to reduce ship CO_2 emissions, this paper comes up with the idea of recovering CO_2 from ship exhaust by Na OH solution and improves the absorption rate by adding Ca O solid particles. The effect mechanism of Ca O solid particles on CO_2 absorption efficiency is analyzed in detail, and the mathematical model is deduced and the Ca O enhancement factor is calculated through experiments. Experiment result demonstrates that the effect of CaO solid particles on the absorption of CO_2 in alkali solution is significant. The absorption rate of pure CO_2 gas,the simulated ship exhaust gas and 6135 AZG marine diesel engine emission can be increased by 10%, 15.85% and10.30%, respectively. So it can be seen that CaO solid particles play an important role in improving the absorption efficiency of ship CO_2 emission.
基金supported by the Environmental Protection Science and Technique Foundation of Jiangsu Province (No. 2005005)
文摘A membrane-based gas absorption （MGA） process was evaluated for the removal of volatile organic compounds （VOCs） based on C6H6/N2 mixture. The absorption of C6H6 from a C6H6/N2 mixture was investigated using a hydrophobic polypropylene hollow fiber membrane contactor and the aqueous solution of N-formyl morpholine （NFM） as absorbent. The effects of various factors on the overall mass transfer coefficient was investigated. The experimental results showed that the removal efficiency of C6H6 could reach 99.5% in present studied system. A mathematical model based on resistance-in-series concept was presented to predict the value of overall mass transfer coefficient. The average error between the predicted and experimental values is 7.9%. In addition, conventional packed columns for VOCs removal was also evaluated for comparison.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10334010 10304001, 10521002, 10434020, 10328407 and 90501007）. We are grateful to Professor Zhang J X for her helpful discussions.
文摘Absorption and refraction of the inner transition F2 ←→F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1←→F3 and F2←→F4 are resonantly interacted with drive field with frequency ωc and Rabi frequency Ωc, and saturation field with ωs and Ωs, respectively. For the suitable Rabi frequencies Ωc and Ωs, we obtain the Mellow absorption spectrum of probe field. The reason is that the drive field excites the atom to the upper level F3 and simultaneously the saturation field takes the atom out of the lower level F2, leading to the stimulated emission. Meanwhile, due to the dynamic energy splitting induced by the drive and saturation fields, the two- and four-peaked absorption spectra are observed. At the zero off-resonance detuning of probe field, we also find the transfer of dispersion from negative to positive with an increment of Ωs. Finally, the refractive index enhancement is predicted for a wide spectral region.
文摘The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The measured two photon absorption coefficientβwas intensity dependent,inferring that reverse saturated absorption(RSA)is also relevant dur-ing high intensity excitation in ZnSe.At low peak intensity I<5 GW cm^(-2),we findβ=3.5 cm GW^(-1) at 775 nm.The spec-tral properties of the broad blueish two-photon induced fluorescence(460 nm-500 nm)was studied,displaying self-ab-sorption near the band edge while the upper state lifetime was measured to be τ_(e)~3.3 ns.Stimulated emission was ob-served when pumping a 0.5 mm thick polycrystalline ZnSe sample within an optical cavity,confirmed by significant line narrowing fromΔλ=11 nm(cavity blocked)toΔλ=2.8 nm at peak wavelength λ_(p)=475 nm while the upper state life-time also decreased.These results suggest that with more optimum pumping conditions and crystal cooling,polycrystal-line ZnSe might reach lasing threshold via two-photon pumping atλ=775 nm.
基金Project supported by the Key Program of the National Natural Science Foundation of China(Grant No.41530644)
文摘A CO_(2) infrared remote sensing system based on the algorithm of weighting function modified differential optical absorption spectroscopy(WFM-DOAS) is developed for measuring CO_(2) emissions from pollution sources. The system is composed of a spectrometer with band from 900 nm to 1700 nm, a telescope with a field of view of 1.12?, a silica optical fiber, an automatic position adjuster, and the data acquisition and processing module. The performance is discussed,including the electronic noise of the charge-coupled device(CCD), the spectral shift, and detection limits. The resolution of the spectrometer is 0.4 nm, the detection limit is 8.5 × 10^(20)molecules·cm^(-2), and the relative retrieval error is < 1.5%.On May 26, 2018, a field experiment was performed to measure CO_(2) emissions from the Feng-tai power plant, and a twodimensional distribution of CO_(2) from the plume was obtained. The retrieved differential slant column densities(dSCDs)of CO_(2) are around 2 × 10^(21) molecules·cm^(-2) in the unpolluted areas, 5.5 × 10^(21)molecules·cm^(-2) in the plume locations most strongly affected by local CO_(2) emissions, and the fitting error is less than 2 × 10^(20)molecules·cm^(-2), which proves that the infrared remote sensing system has the characteristics of fast response and high precision, suitable for measuring CO_(2) emission from the sources.
基金jointly supported by the National Natural Science Foundation of China(Nos.21502136 and 51702228)the Natural Science Foundation of Shandong Province(ZR2017LB010)the Scientific Research Initial Foundation for Introduction of Talent of Taishan University(Y-01-2013010)
文摘The absorption and emission spectra, as well as the photolysis mechanism of p-phenylbenzoyl methanthiol in methanol and in gas phase were elucidated in detail based on the molecular structures of the ground states, excited states and their spectroscopic characters. The TD-M062 X calculations demonstrate that the S_1 state in gas phase will decompose into SH and p-phenylbenzoyl radical via a barrierless process, but the T_1 and T_2 do not photolyze. By adding 1 and 2 methanol molecules onto p-phenylbenzoyl methanthiol, the CPCM model can perfectly describe the solvation effects of methanol. Methanol may stabilize the excitation states, but also protects the resulting radical products from recombination.
文摘Burners of metal halide lamps used for illumination are generally made of polycrystalline alumina ceramic （PCA） which is translucent to visible light. We show that the difficulty of selecting a line of sight through the lamp prevents the use of optical emission diagnostic. X-rays photons are mainly absorbed and not scattered by PCA. Absorption by mercury atoms contributing to the discharge allowed us to determine the density of mercury in the lamp. By comparing diagnostic methods, we put in evidence the difficulty of taking into account the scattering of light mathematically.
基金supported by the National Natural Science Foundation of China(NSFC,11573024,11473025,11421303,11573001and 11822301)the National Basic Research Program of China(the 973 Program 2013CB834905and 2015CB857005)+11 种基金supported by the NSFC(11503022)the Natural Science Foundation of Shanghai(No.15ZR 1444200)supported by the NSFC(11233002)support from the Anhui Provincial NSF(1608085QA06)Young Wanjiang Scholar programfunded by the Strategic Priority Research Programthe Emergence of Cosmological Structures(XDB09000000),National Astronomical Observatories,Chinese Academy of Sciencesthe Special Fund for Astronomy from the Ministry of FinanceFunding for SDSS-Ⅲhas been provided by the Alfred P.Sloan Foundationthe Participating Institutionsthe National Science Foundationthe U.S.Department of Energy Office of Science。
文摘We report on the discovery of unusual broad absorption lines(BALs)in the bright quasar SDSS J075133.35+134548.3 at z~1,using archival and newly obtained optical and NIR spectroscopic data.The BALs are detected reliably in HeⅠ*λ3889,HeⅠ*λ10830 and tentatively in AlⅢ,MgⅡ.These BALs show complex velocity structures consisting of two major components:a high-velocity component(HV),with a blueshifted velocity range ofΔv_(HV)~9300--3500 km s^(-1),which can be reliably detected in HeⅠ*λ10830,and tentatively in AlⅢand MgⅡ,whereas it is undetectable in HeⅠ*λ3889;and a low-velocity component(LV),withΔv_(LV)~3500--1800 km s^(-1),is only detected in HeⅠ*λ3889 and HeⅠ*λ10830.With the BALs from different ions,the HV outflowing gas can be constrained to have a density of nH~10^(10.3)-10^(11.4) cm^(-3),a column density of NH~10^(21) cm^(-2)and an ionization parameter of U~10^(-1.83)-10^(-1.72);inferring a distance of RHV~0.5 pc from the central continuum source with a monochromatic luminosityλLλ(5100)=7.0×10^(45)erg s^(-1)at 5100 A.This distance is remarkably similar to that of the normal broad line region(BLR)estimated from reverberation experiments,suggesting association of the BLR and the HV BAL outflowing gas.Interestingly,a blueshifted component is also detected in AlⅢand MgⅡbroad emission lines(BELs),and the AlⅢ/MgⅡof such a BEL component can be reproduced by the physical parameters inferred from the HV BAL gas.The LV BAL gas likely has a larger column density,a higher ionization level and hence a smaller distance than the HV BAL gas.Further spectroscopy with a high S/N ratio and broader wavelength coverage is needed to confirm this to shed new light on the possible connection between BALs and BELs.
文摘A general relation between the total absorption and emission probabilities for nuclei in thermal equilibrium at a finite temperature is derived,and its relevance to giant resonances built on nuclear excited states discussed.
文摘The vacuum ultraviolet absorption and emission spectra of rare-gas vander Waals molecules were observed.A large broadening of at least 240Åof Xe first resonance absorption line was obtained at cell presgure 4 atm.Strong continuous emission of heavier rare gases at 1300-3000Åwas obtained using self-triggered condensed discharge in aπ-shaped quartz discharge tube.
基金supported by the Ministry of Education and Science of theRussian Federationsupported by the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists (Grant Nos. 2011T1J20 and 2010T2J24)+2 种基金supported by the Russian Foundation of Basic Research (RFBR,GrantNos. 11-02-00757,11-02-91151,10-02-00153,12-02-91161-GFEN and FP7-PEOPLE-2011-IRSES)The National Basic Research Program of the Ministry of Science and Technology of China(Grant No. 2006CB806301)CAS-NSFC Key Project (Grant No. 10778605) support the Chinese
文摘In some events, weak fast solar bursts （near the level of the quiet Sun） were observed in the background of numerous spikes in emission and absorption. In such a case, the background contains the noise signals of the receiver. In events on 2005 September 16 and 2002 April 14, the solar origin of fast bursts was confirmed by simultaneous recording of the bursts at several remote observatories. The noisy background pixels in emission and absorption can be excluded by subtracting a higher level of continuum when constructing the spectra. The wavelet spectrum, noisy pro- files in different polarization channels and a spectrum with continuum level greater than zero demonstrates the noisy character of pixels with the lowest levels of emission and absorption. Thus, in each case, in order to judge the solar origin of all spikes, it is necessary to determine the level of continuum against the background of which the solar bursts are observed. Several models of microwave spikes are discussed. The electron cyclotron maser emission mechanism runs into serious problems with the in- terpretation of microwave millisecond spikes： the main obstacles are too high values of the magnetic field strength in the source （Pe 〈 uB）. The probable mechanism is the interaction of plasma Langmuir waves with ion-sound waves （l ＋ s → t） in a source related to shock fronts in the reconnection region.
文摘Formamidinium lead bromide(FAPbBr_(3))nanocrystals(NCs)have been considered to be a good optoelectronic material due to their pure green emission,excellent stability and superior carrier transport characteristics.However,two-photon pumped amplified spontaneous emission(ASE)and the corresponding nonlinear optical properties of FAPbBr_(3) NCs are scarcely revealed.Herein,we synthesized colloidal FAPbBr_(3) NCs with different sizes by changing the molar ratio of FABr/PbBr_(2) in the precursor solution,using ligand assisted precipitation(LARP)technology at room temperature.Photoluminescence(PL)and time resolved photoluminescence(TRPL)spectroscopy were measured to characterize their ASE properties.And their nonlinear optical properties were studied through the Zscan technique and the two-photon excited fluorescence method.The stimulated emission properties including oneand two-photon pumped ASE have been realized from FAPbBr_(3) NCs.With large two-photon absorption coefficient(0.27 cm/GW)and high non-linear absorption cross-section(7.52×10^(5) GM),ASE with threshold as low as 9.8μJ/cm^(2) and 487μJ/cm^(2) have been obtained from colloidal FAPbBr_(3) NCs using one-and two-photon excitations.These results indicate that as a new possible green-emitting frequency-upconversion material with low thresholds,FAPbBr_(3) NCs hold great potential in the development of high-performance two-photon pump lasers.
文摘To protect environment, and to comply with the IMO＇s （International Maritime Organization） newest regulations about ship＇s SOx emission. This thesis illustrates a closed recycling absorb system based on NaOH solution recycling particularly for SOx onboard. The goal is to use NaOH solution to absorb SOx, and reduce the damage the ships made towards environment. The thesis analyzes the main features that could influence the absorption of SOx on board, and the precipitations during the experiment. To reveal that NaOH solution is very highly effective and economic in absorption of SOx on ships by this experiment, and to set a theoretical basic fundamental for future application of alkali solution recycling absorption system for SOx.
基金Project supported by the National Basic Research Program of China(Grant No.2010CB934101)the National Natural Science Foundation of China(Grant No.11174161)the International S&T Cooperation Program of China(Grant No.2011DFA52870)
文摘A theoretical approach based on differential radiative transport is proposed to quantitatively analyze the self- absorption and reemission effects on the emission spectrum for right angle excitation-detection photoluminescence mea- surements, and the wavelength dependence of the reemission effect is taken into account. Simulations and experiments are performed using rhodamine 6G solutions in ethanol as model samples. It is shown that the self-absorption effect is the dominant effect on the detected spectrum by inducing pseudo red-shift and reducing total intensity; whereas the reemission effect partly compensates for signal decrease and also results in an apparent signal gain at the wavelengths without ab- sorption. Both effects decrease with the decrease in the sample concentration and the propagation distance of the emission light inside the sample. We therefore suggest that diluted solutions are required for accurate photoluminescence spectrum measurements and photoluminescence-based measurements.
基金financially supported by the National Natural Science Foundation of China(Grants nos.62201411,62371378,22205168,52302150 and 62304171)the China Postdoctoral Science Foundation(2022M722500)+1 种基金the Fundamental Research Funds for the Central Universities(Grants nos.ZYTS2308 and 20103237929)Startup Foundation of Xidian University(10251220001).
文摘Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,however,constrain their delicate constructions.Herein,an innovative alternative is proposed:carrageenan-assistant cations-regulated(CACR)strategy,which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon matrix.This unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction,benefiting the delicate construction of defects-rich heterostructures in M_(x)S_(y)/carbon composites(M-CAs).Impressively,these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and,simultaneously,induct local asymmetry of electronic structure to evoke large dipole moment,ultimately leading to polarization coupling,i.e.,defect-type interfacial polarization.Such“Janus effect”(Janus effect means versatility,as in the Greek two-headed Janus)of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first time.Consequently,the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm,compared to sulfur vacancies-free CAs without any dielectric response.Harnessing defects-rich heterostructures,this one-pot CACR strategy may steer the design and development of advanced nanomaterials,boosting functionality across diverse application domains beyond electromagnetic response.
基金financial support from the National Nature Science Foundation of China(No.52273247)the National Science and Technology Major Project of China(J2019-VI-0017-0132).
文摘Developing advanced stealth devices to cope with radar-infrared(IR)fusion detection and diverse application scenarios is increasingly demanded,which faces significant challenges due to conflicting microwave and IR cloaking mechanisms and functional integration limitations.Here,we propose a multiscale hierarchical structure design,integrating wrinkled MXene IR shielding layer and flexible Fe_(3)O_(4)@C/PDMS microwave absorption layer.The top wrinkled MXene layer induces the intensive diffuse reflection effect,shielding IR radiation signals while allowing microwave to pass through.Meanwhile,the permeable microwaves are assimilated into the bottom Fe_(3)O_(4)@C/PDMS layer via strong magneto-electric synergy.Through theoretical and experimental optimization,the assembled stealth devices realize a near-perfect stealth capability in both X-band(8–12 GHz)and long-wave infrared(8–14μm)wavelength ranges.Specifically,it delivers a radar cross-section reduction of−20 dB m^(2),a large apparent temperature modulation range(ΔT=70℃),and a low average IR emissivity of 0.35.Additionally,the optimal device demonstrates exceptional curved surface conformability,self-cleaning capability(contact angle≈129°),and abrasion resistance(recovery time≈5 s).This design strategy promotes the development of multispectral stealth technology and reinforces its applicability and durability in complex and hostile environments.
基金financially supported by the National Natural Science Foundation of China(52373271)Science,Technology and Innovation Commission of Shenzhen Municipality under Grant(KCXFZ20201221173004012)+1 种基金National Key Research and Development Program of Shaanxi Province(No.2023-YBNY-271)Open Testing Foundation of the Analytical&Testing Center of Northwestern Polytechnical University(2023T019).
文摘Gradient magnetic heterointerfaces have injected infinite vitality in optimizing impedance matching,adjusting dielectric/magnetic resonance and promoting electromagnetic(EM)wave absorption,but still exist a significant challenging in regulating local phase evolution.Herein,accordion-shaped Co/Co_(3)O_(4)@N-doped carbon nanosheets(Co/Co_(3)O_(4)@NC)with gradient magnetic heterointerfaces have been fabricated via the cooperative high-temperature carbonization and lowtemperature oxidation process.The results indicate that the surface epitaxial growth of crystal Co_(3)O_(4) domains on local Co nanoparticles realizes the adjustment of magnetic-heteroatomic components,which are beneficial for optimizing impedance matching and interfacial polarization.Moreover,gradient magnetic heterointerfaces simultaneously realize magnetic coupling,and long-range magnetic diffraction.Specifically,the synthesized Co/Co_(3)O_(4)@NC absorbents display the strong electromagnetic wave attenuation capability of−53.5 dB at a thickness of 3.0 mm with an effective absorption bandwidth of 5.36 GHz,both are superior to those of single magnetic domains embedded in carbon matrix.This design concept provides us an inspiration in optimizing interfacial polarization,regulating magnetic coupling and promoting electromagnetic wave absorption.
基金financially supported by the National Natural Science Foundation of China(No.52377026 and No.52301192)Taishan Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)+4 种基金Postdoctoral Fellowship Program of CPSF under Grant Number(No.GZB20240327)Shandong Postdoctoral Science Foundation(No.SDCXZG-202400275)Qingdao Postdoctoral Application Research Project(No.QDBSH20240102023)China Postdoctoral Science Foundation(No.2024M751563)the Qingchuang Talents Induction Program of Shandong Higher Education Institution(Research and Innovation Team of Structural-Functional Polymer Composites).
文摘Currently,the demand for electromagnetic wave(EMW)absorbing materials with specific functions and capable of withstanding harsh environments is becoming increasingly urgent.Multi-component interface engineering is considered an effective means to achieve high-efficiency EMW absorption.However,interface modulation engineering has not been fully discussed and has great potential in the field of EMW absorption.In this study,multi-component tin compound fiber composites based on carbon fiber(CF)substrate were prepared by electrospinning,hydrothermal synthesis,and high-temperature thermal reduction.By utilizing the different properties of different substances,rich heterogeneous interfaces are constructed.This effectively promotes charge transfer and enhances interfacial polarization and conduction loss.The prepared SnS/SnS_(2)/SnO_(2)/CF composites with abundant heterogeneous interfaces have and exhibit excellent EMW absorption properties at a loading of 50 wt%in epoxy resin.The minimum reflection loss(RL)is−46.74 dB and the maximum effective absorption bandwidth is 5.28 GHz.Moreover,SnS/SnS_(2)/SnO_(2)/CF epoxy composite coatings exhibited long-term corrosion resistance on Q235 steel surfaces.Therefore,this study provides an effective strategy for the design of high-efficiency EMW absorbing materials in complex and harsh environments.
基金sponsored by National Natural Science Foundation of China(No.52302121,No.52203386)Shanghai Sailing Program(No.23YF1454700)+1 种基金Shanghai Natural Science Foundation(No.23ZR1472700)Shanghai Post-doctoral Excellent Program(No.2022664).
文摘With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.
