Recent work analysing magnesium hydrogenation using Reflecting Electron Energy Loss Spectroscopy(REELS)and Density Function Theory(DFT)has indicated interfacial polarisation and interstitial hydrogen clustering influe...Recent work analysing magnesium hydrogenation using Reflecting Electron Energy Loss Spectroscopy(REELS)and Density Function Theory(DFT)has indicated interfacial polarisation and interstitial hydrogen clustering influence the reaction rate.The site availability model has been modified to include interstitial hydrogen clustering within the site availability factor and interface polarisation using interface treatment.The new model,SAM-CV-S,has demonstrated improved modelling of magnesium hydrogenation across wide operating conditions,such as temperatures from 330 to 400℃and pressures up to 40 bar.This wide applicability makes it a robust model that can be used to simulate bed performance in solid-state hydrogen stores.Thus,the site availability factor successfully combines interstitial hydrogen clustering with thermal resistance effects,which are known to strongly influence metal hydride reactor designs at scale.The next phase of the model is to incorporate a predictive hydrogen capacity method into the model.展开更多
This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisati...This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisation test results. X-ray photoelectron spectroscopy analyses of fluoride ion-labelled samples show that PCPT cannot remove the surface film completely due to the low reaction rate. Potentiodynamic polarisation tests demonstrate that PCPT with proper operating parameters,-1.0 V SCE for 5 min with subsequent open circuit potential(OCP) stabilisation in this study, is necessary because it can improve the test reproducibility without affecting the corrosion parameters by unifying the initial surface state. However, PCPT with lower potentials, longer time or no OCP stabilisation has significant effects on the electrochemical corrosion parameters due to the hydrogen absorption under the conditions of this study.展开更多
SrBi4-xFexTi4015 （SBFT-x） thin films （x = 0.00, 0.05, 0.08, 0.15） have been synthesized on Pt/Ti/SiO2/Si （100） substrates by sol-gel method. This paper finds that Fe-doping does not change the crystal structure ...SrBi4-xFexTi4015 （SBFT-x） thin films （x = 0.00, 0.05, 0.08, 0.15） have been synthesized on Pt/Ti/SiO2/Si （100） substrates by sol-gel method. This paper finds that Fe-doping does not change the crystal structure of SrBi4Ti4015 （SBTi）. The coercive filed （Ec） and remnant polarisation （Pr） increase at first, then decrease with the increase of Fe doping content. At a maximum applied field of 229 kV/cm, the 2Pr reaches a maximum value of 91.1μC/cm2 at x = 0.05 and the corresponding Ec is 72 kV/cm. The 2Pr increases by about 260% and the Ec decreases by about 6%, respectively. Obviously, the ferroelectric property of SrBi4Ti4015 is greatly enhanced by Fe doping. The fatigueendurance characteristic of the SBFT-0.05 is not improved. After 1.1× 10^9 read/write cycles at a frequency of 50 kHz, the nonvolatile polarisations （Pnv = P＊ - P^） decreased about 48% of its initial value.展开更多
The Mg corrosion mechanism was explored using galvanostatic polarisation curves,hydrogen evolution and weight loss.The data(a)were consistent with the existence of the uni-positive Mg+ion,(b)indicated that some hydrog...The Mg corrosion mechanism was explored using galvanostatic polarisation curves,hydrogen evolution and weight loss.The data(a)were consistent with the existence of the uni-positive Mg+ion,(b)indicated that some hydrogen dissolved in the WE43 metal,and(c)indicated that self corrosion was more important than the applied current density in causing weight loss.展开更多
A range of partial top full bottom electrodes are used to explore the use of bi-polar Polarisation-Electricfield(PeE)measurements to quantify recoverable energy(Wrec),energy loss(W_(loss))and the efficiency(h)of ferro...A range of partial top full bottom electrodes are used to explore the use of bi-polar Polarisation-Electricfield(PeE)measurements to quantify recoverable energy(Wrec),energy loss(W_(loss))and the efficiency(h)of ferroelectric BaTiO_(3)ceramics.The values obtained are dependent on the ratio of sample thickness(S)and top contact radius(r).With increasing S/r from 0.17 to 1.96 the P-E responses become increasingly distorted and broader.Measurements show Wrec increases by a factor of~1.4 but Wloss increases by a factor of~7 with h decreasing from~29%to 8%.Finite element modelling was used to simulate the experimental set-up of the sample/electrode arrangements using the Jiles-Atherton model to replicate the ferroelectric behaviour of BaTiO_(3).These models demonstrate the experimentally applied electricfield using a simple geometric correction for sample thickness is an underestimation of the actualfield experienced by the material under the top contact at high S/r values.We stress the importance of reporting the contact sizes and thicknesses of samples when using PeE measurements to assess Wrec,W_(loss)andηin non-linear dielectric materials.This will allow a fairer comparison of performances between various types of materials being considered for high-energy-density ceramic capacitors.展开更多
The editorial office regrets that mistakes occurred during the presentation of Figs.1 and 4.Specifically,a typographic error in Figs.1 and 4 was mistakenly taken from a different article.The editorial office would lik...The editorial office regrets that mistakes occurred during the presentation of Figs.1 and 4.Specifically,a typographic error in Figs.1 and 4 was mistakenly taken from a different article.The editorial office would like to apologise for any inconvenience caused,and the corrected figures are pending as below.展开更多
Peripheral nerve injury poses a great threat to neurosurgery and limits the regenerative potential of sacral nerves in the neurogenic bladder.It remains unknown whether electrical stimulation can facilitate sacral ner...Peripheral nerve injury poses a great threat to neurosurgery and limits the regenerative potential of sacral nerves in the neurogenic bladder.It remains unknown whether electrical stimulation can facilitate sacral nerve regeneration in addition to modulate bladder function.The objective of this study was to utilise electrical stimulation in sacra nerve crush injury with newly constructed electroconductive scaffold and explore the role of macrophages in electrical stimulation with crushed nerves.As a result,we generated a polypyrrole-coated polycaprolactone/silk fibroin scaffold through which we applied electrical stimulation.The electrical stimulation boosted nerve regeneration and polarised the macrophages towards the M2 phenotype.An in vitro test using bone marrow derived macrophages revealed that the pro-regenerative polarisation of M2 were significantly enhanced by electrical stimulation.Bioinformatics analysis showed that the expression of signal transducer and activator of transcriptions(STATs)was differentially regulated in a way that promoted M2-related genes expression.Our work indicated the feasibility of electricals stimulation used for sacral nerve regeneration and provided a firm demonstration of a pivotal role which macrophages played in electrical stimulation.展开更多
Owing to the low p-type doping efficiency in the hole injection layers(HILs)of GaN-based ultra-violet(UV)vertical-cavity surface-emitting laser(VCSEL),effective hole injection in multi-quantum wells(MQW)is not achieve...Owing to the low p-type doping efficiency in the hole injection layers(HILs)of GaN-based ultra-violet(UV)vertical-cavity surface-emitting laser(VCSEL),effective hole injection in multi-quantum wells(MQW)is not achieved,significantly limiting the photoelectric performance of UV VCSELs.We developed a slope-shaped HIL and an EBL structure in AlGaN-based UV VCSELs.In this study,by improving hole in-jection efficiency,the hole concentration in the HIL is increased,and the hole barrier at the electron barrier layer(EBL)/HIL interface is decreased.This minimises the hindering effect of hole injection.A mathematic-al model of this structure was established using a commercial software,photonic integrated circuit simulator in three-dimension(PICS3D).We conducted simulations and theoretical analyses of the band structure and carrier concentration.Introducing polarisation doping through the Al composition gradient in the HIL en-hanced the hole concentration,thereby improving the hole injection efficiency.Furthermore,modifying the EBL eliminated the abrupt potential barrier for holes at the HIL/EBL interface,smoothing the valence band.This improved the stimulated radiative recombination rate in the MQW,increasing the laser power.There-fore,the sloped p-type layer can enhance the optoelectronic performance of UV VCSELs.展开更多
Multi-scale methods that separate different time or spatial scales are among the most powerful techniques in physics,especially in applications that study nonlinear systems with noise.When the time scales(noise and pe...Multi-scale methods that separate different time or spatial scales are among the most powerful techniques in physics,especially in applications that study nonlinear systems with noise.When the time scales(noise and perturbation)are of the same order,the scales separation becomes impossible.Thus,the multi-scale approach has to be modified to characterise a variety of noise-induced phenomena.Here,based on stochastic modelling and analytical study,we demonstrate in terms of the fluctuation-induced phenomena and Hurst R/S analysis metrics that the matching scales of random birefringence and pump–signal states of polarisation interaction in a fibre Raman amplifier results in a new random birefringence-mediated phenomenon,which is similar to stochastic anti-resonance.The observed phenomenon,apart from the fundamental interest,provides a base for advancing multi-scale methods with application to different coupled nonlinear systems ranging from lasers(multimode,mode-locked,random,etc.)to nanostructures(light-mediated conformation of molecules and chemical reactions,Brownian motors,etc.).展开更多
Multi-photon lithography has emerged as a powerful tool for photonic integration,allowing to complement planar photonic circuits by 3D-printed freeform structures such as waveguides or micro-optical elements.These str...Multi-photon lithography has emerged as a powerful tool for photonic integration,allowing to complement planar photonic circuits by 3D-printed freeform structures such as waveguides or micro-optical elements.These structures can be fabricated with a high precision on the facets of optical devices and enable highly efficient package-level chip-chip connections in photonic assemblies.However,plain light transport and efficient coupling is far from exploiting the full geometrical design freedom offered by 3D laser lithography.Here,we extended the functionality of 3D-printed optical structures to manipulation of optical polarisation states.We demonstrate compact ultra-broadband polarisation beam splitters(PBSs)that can be combined with polarisation rotators and mode-field adapters into a monolithic 3D-printed structure,fabricated directly on the facets of optical devices.In a proof-of-concept experiment,we demonstrate measured polarisation extinction ratios beyond 11 dB over a bandwidth of 350 nm at near-infrared telecommunication wavelengths around 1550 nm.We demonstrate the viability of the device by receiving a 640 Gbit/s dual-polarisation data signal using 16-state quadrature amplitude modulation(16QAM),without any measurable optical-signal-to-noise-ratio penalty compared to a commercial PBS.展开更多
The electrochemical behavior of Ti-6Al-4V with 1 mm and 16 mm thickness prepared by electron beam powder bed fusion(EB-PBF)was investigated in phosphate buffered saline.Electrochemical results showed that EB-PBF Ti-6A...The electrochemical behavior of Ti-6Al-4V with 1 mm and 16 mm thickness prepared by electron beam powder bed fusion(EB-PBF)was investigated in phosphate buffered saline.Electrochemical results showed that EB-PBF Ti-6Al-4V with a larger component size was more resistant to corrosion compared to the smaller component,because of less acicularαʹphase content and moreβphase content.As a non-equilibrium phase in the“high-energy state”,αʹphase has a greater susceptibility to corrode and reduces the corrosion resistance of the material,whileβphase improves corrosion resistance of titanium alloys.The results show that the phase composition has a more significant effect on the corrosion performance than the grain size.展开更多
Potentiodynamic polarisation, potential-time measurements, X-ray diffraction (XRD) and infrared spectroscopy (IR) have been used to investigate the effect of different concentrations of Na2SO4 in the absence and prese...Potentiodynamic polarisation, potential-time measurements, X-ray diffraction (XRD) and infrared spectroscopy (IR) have been used to investigate the effect of different concentrations of Na2SO4 in the absence and presence of NaCI, on the corrosion of Cu-alloy. The electrochemical measurements showed that the increase of Na2SO4 concentration led to increase the corrosion current density of Cu alloy and vice versa. The presence of NaCI shifted the potential to more cathodic potential, which had a great influence on the protectiveness of the Cu oxide layer formed on the surface in presence of Na2SO4. The spectrometric measurements indicated the constituents of the film formed on the alloy surface were mainly Cu2O, in addition to the oxides, NiO and Fe2O3, which were traced by XRD analysis.展开更多
The effect of tetra ethyl ammonium bromide （TEAB） as an additive on the structural, morphological characteristics of the cobalt metal produced from aqueous sulphate solutions was investigated. The concentration of T...The effect of tetra ethyl ammonium bromide （TEAB） as an additive on the structural, morphological characteristics of the cobalt metal produced from aqueous sulphate solutions was investigated. The concentration of TEAB was varied in a range of 1-50 mg/L to evaluate its effect on current efficiency, energy consumption and quality of electrodeposited cobalt metal. Smooth and bright deposits of cobalt were obtained at low concentration of TEAB （10 mg/L） maintaining a current efficiency of 99.6%, with a low energy consumption of 2.38 kW＇h/kg. X-ray diffraction studies reveal that （100） plane is the most preferred plane of crystal growth during cobalt electrodeposition. Scanning electron micrographs indicate that smooth and uniform deposit of cobalt is obtained at 10 mg/L beyond which the deposit quality deteriorates. Cyclic voltammetric studies indicate that the presence of TEAB in the electrolytic bath polarizes the cathode and decreases the cathodic current considerably. XPS results confirm the electrodeposition of high pure cobalt with no sign of chemical bonding with TEAB as evident from the FTIR spectra.展开更多
A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a ...A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567-575, 605-614 and 656-666 nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre.展开更多
Effect of added Co2 +(aq)on copper electrowinning was studied using doped polyaniline(Pani)and Pb-Ag(1%)anodes and a stainless steel cathode.The presence of added Co2+ (aq)in the electrolyte solution was found to decr...Effect of added Co2 +(aq)on copper electrowinning was studied using doped polyaniline(Pani)and Pb-Ag(1%)anodes and a stainless steel cathode.The presence of added Co2+ (aq)in the electrolyte solution was found to decrease the anode potentials.The optimum level of Co2 +(aq)concentration in the electrolyte,with respect to the maximum saving of power consumption was established.Linear sweep voltammetry(LSV)was used to study the influence of added Co2 +(aq)on the anodic processes in a copper sulfate-sulfuric acid electrolyte.The oxygen-evolution potential for Pani anode is depolarised at lower current densities(≤0.01 A/cm2)and attains saturation atρ(Co 2+ )o≈0.789 g/L;whilst the oxygen-evolution potential for Pb-Ag(1%)anode is depolarised at higher current densities(≤0.02 A/cm2)and attains saturation atρ(Co 2+ )o≈1.315 g/L.The preferred orientations of the copper deposits change from(220)to(111)with the addition of 0.394?0.789 g/L Co 2+ but higher concentrations favor(220)orientation again.展开更多
We report the femtosecond(fs)laser fabrication of biomimetic omnidirectional iridescent metallic surfaces exhibiting efficient diffraction for practically any angle of light incidence.Such diffractive behavior is real...We report the femtosecond(fs)laser fabrication of biomimetic omnidirectional iridescent metallic surfaces exhibiting efficient diffraction for practically any angle of light incidence.Such diffractive behavior is realized by means of multi-directional low-spatial-frequency,laser-induced periodic surface structures(LSFL)formed upon exploiting the cylindrical symmetry of a cylindrical vector(CV)fs field.We particularly demonstrate that the multi-directional gratings formed on stainless steel surface by a radially polarized fs beam,could mimic the omnidirectional structural coloration properties found in some natural species.Accordingly,the fabricated grating structures can spatially disperse the incident light into individual wavelength with high efficiency,exhibiting structural iridescence at all viewing angles.Analytical calculations using the grating equation reproduced the characteristic variation of the vivid colors observed as a function of incident angle.We envisage that our results will significantly contribute to the development of new photonic and light sensing devices.展开更多
The corrosion behaviour of the hard anodic coatings prepared by three different methods viz., conventional hard anodizing （C-HA）, pulse hard anodizing （P-HA） and low voltage room temperature pulse hard anodizing ...The corrosion behaviour of the hard anodic coatings prepared by three different methods viz., conventional hard anodizing （C-HA）, pulse hard anodizing （P-HA） and low voltage room temperature pulse hard anodizing （LVP- HA） on AA 6061 was compared using electrochemical impedance spectroscopy （EIS） and linear polarisation. Scanning electron microscope （SEM） was used to study the surface morphology before and after corrosion. EIS data revealed that no significant difference in corrosion resistance was observed among three types. Rp, Icorr and Ecorr were found to be highly stable over the exposure period up to 72 h which confirms the excellent corrosion resistance. The studies indicate that the corrosion resistance of LVP-HA and P-HA, which are processed at lower voltage and at relatively higher temperatures, are comparable to that of C-HA which is processed at sub-zero temperatures and high operating voltages. The corrosion resistance of all coatings was found to be improved after hydrothermal sealing.展开更多
This paper presents a theoretical study of wavelength dependence four-wave-mixing （FWM） spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatc...This paper presents a theoretical study of wavelength dependence four-wave-mixing （FWM） spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke- narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.展开更多
基金funded through Engineering and Physical Sciences Research Council(EPSRC)[grant numbers EP/W005131/1,EP/V042556/1].
文摘Recent work analysing magnesium hydrogenation using Reflecting Electron Energy Loss Spectroscopy(REELS)and Density Function Theory(DFT)has indicated interfacial polarisation and interstitial hydrogen clustering influence the reaction rate.The site availability model has been modified to include interstitial hydrogen clustering within the site availability factor and interface polarisation using interface treatment.The new model,SAM-CV-S,has demonstrated improved modelling of magnesium hydrogenation across wide operating conditions,such as temperatures from 330 to 400℃and pressures up to 40 bar.This wide applicability makes it a robust model that can be used to simulate bed performance in solid-state hydrogen stores.Thus,the site availability factor successfully combines interstitial hydrogen clustering with thermal resistance effects,which are known to strongly influence metal hydride reactor designs at scale.The next phase of the model is to incorporate a predictive hydrogen capacity method into the model.
基金the National Science and Technology Major Project of China(No.2016ZX05016-004)the National Natural Science Foundation of China(Nos.51801218 and 51571200)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA13040500)。
文摘This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisation test results. X-ray photoelectron spectroscopy analyses of fluoride ion-labelled samples show that PCPT cannot remove the surface film completely due to the low reaction rate. Potentiodynamic polarisation tests demonstrate that PCPT with proper operating parameters,-1.0 V SCE for 5 min with subsequent open circuit potential(OCP) stabilisation in this study, is necessary because it can improve the test reproducibility without affecting the corrosion parameters by unifying the initial surface state. However, PCPT with lower potentials, longer time or no OCP stabilisation has significant effects on the electrochemical corrosion parameters due to the hydrogen absorption under the conditions of this study.
文摘SrBi4-xFexTi4015 （SBFT-x） thin films （x = 0.00, 0.05, 0.08, 0.15） have been synthesized on Pt/Ti/SiO2/Si （100） substrates by sol-gel method. This paper finds that Fe-doping does not change the crystal structure of SrBi4Ti4015 （SBTi）. The coercive filed （Ec） and remnant polarisation （Pr） increase at first, then decrease with the increase of Fe doping content. At a maximum applied field of 229 kV/cm, the 2Pr reaches a maximum value of 91.1μC/cm2 at x = 0.05 and the corresponding Ec is 72 kV/cm. The 2Pr increases by about 260% and the Ec decreases by about 6%, respectively. Obviously, the ferroelectric property of SrBi4Ti4015 is greatly enhanced by Fe doping. The fatigueendurance characteristic of the SBFT-0.05 is not improved. After 1.1× 10^9 read/write cycles at a frequency of 50 kHz, the nonvolatile polarisations （Pnv = P＊ - P^） decreased about 48% of its initial value.
文摘The Mg corrosion mechanism was explored using galvanostatic polarisation curves,hydrogen evolution and weight loss.The data(a)were consistent with the existence of the uni-positive Mg+ion,(b)indicated that some hydrogen dissolved in the WE43 metal,and(c)indicated that self corrosion was more important than the applied current density in causing weight loss.
基金the EPSRC funding to support this work through a CASE conversion DTP grant EP/T517835/1.
文摘A range of partial top full bottom electrodes are used to explore the use of bi-polar Polarisation-Electricfield(PeE)measurements to quantify recoverable energy(Wrec),energy loss(W_(loss))and the efficiency(h)of ferroelectric BaTiO_(3)ceramics.The values obtained are dependent on the ratio of sample thickness(S)and top contact radius(r).With increasing S/r from 0.17 to 1.96 the P-E responses become increasingly distorted and broader.Measurements show Wrec increases by a factor of~1.4 but Wloss increases by a factor of~7 with h decreasing from~29%to 8%.Finite element modelling was used to simulate the experimental set-up of the sample/electrode arrangements using the Jiles-Atherton model to replicate the ferroelectric behaviour of BaTiO_(3).These models demonstrate the experimentally applied electricfield using a simple geometric correction for sample thickness is an underestimation of the actualfield experienced by the material under the top contact at high S/r values.We stress the importance of reporting the contact sizes and thicknesses of samples when using PeE measurements to assess Wrec,W_(loss)andηin non-linear dielectric materials.This will allow a fairer comparison of performances between various types of materials being considered for high-energy-density ceramic capacitors.
文摘The editorial office regrets that mistakes occurred during the presentation of Figs.1 and 4.Specifically,a typographic error in Figs.1 and 4 was mistakenly taken from a different article.The editorial office would like to apologise for any inconvenience caused,and the corrected figures are pending as below.
基金supported by Capital’s Funds for Health Improvement and Research(No.CFH2022-2-5022).
文摘Peripheral nerve injury poses a great threat to neurosurgery and limits the regenerative potential of sacral nerves in the neurogenic bladder.It remains unknown whether electrical stimulation can facilitate sacral nerve regeneration in addition to modulate bladder function.The objective of this study was to utilise electrical stimulation in sacra nerve crush injury with newly constructed electroconductive scaffold and explore the role of macrophages in electrical stimulation with crushed nerves.As a result,we generated a polypyrrole-coated polycaprolactone/silk fibroin scaffold through which we applied electrical stimulation.The electrical stimulation boosted nerve regeneration and polarised the macrophages towards the M2 phenotype.An in vitro test using bone marrow derived macrophages revealed that the pro-regenerative polarisation of M2 were significantly enhanced by electrical stimulation.Bioinformatics analysis showed that the expression of signal transducer and activator of transcriptions(STATs)was differentially regulated in a way that promoted M2-related genes expression.Our work indicated the feasibility of electricals stimulation used for sacral nerve regeneration and provided a firm demonstration of a pivotal role which macrophages played in electrical stimulation.
文摘Owing to the low p-type doping efficiency in the hole injection layers(HILs)of GaN-based ultra-violet(UV)vertical-cavity surface-emitting laser(VCSEL),effective hole injection in multi-quantum wells(MQW)is not achieved,significantly limiting the photoelectric performance of UV VCSELs.We developed a slope-shaped HIL and an EBL structure in AlGaN-based UV VCSELs.In this study,by improving hole in-jection efficiency,the hole concentration in the HIL is increased,and the hole barrier at the electron barrier layer(EBL)/HIL interface is decreased.This minimises the hindering effect of hole injection.A mathematic-al model of this structure was established using a commercial software,photonic integrated circuit simulator in three-dimension(PICS3D).We conducted simulations and theoretical analyses of the band structure and carrier concentration.Introducing polarisation doping through the Al composition gradient in the HIL en-hanced the hole concentration,thereby improving the hole injection efficiency.Furthermore,modifying the EBL eliminated the abrupt potential barrier for holes at the HIL/EBL interface,smoothing the valence band.This improved the stimulated radiative recombination rate in the MQW,increasing the laser power.There-fore,the sloped p-type layer can enhance the optoelectronic performance of UV VCSELs.
文摘Multi-scale methods that separate different time or spatial scales are among the most powerful techniques in physics,especially in applications that study nonlinear systems with noise.When the time scales(noise and perturbation)are of the same order,the scales separation becomes impossible.Thus,the multi-scale approach has to be modified to characterise a variety of noise-induced phenomena.Here,based on stochastic modelling and analytical study,we demonstrate in terms of the fluctuation-induced phenomena and Hurst R/S analysis metrics that the matching scales of random birefringence and pump–signal states of polarisation interaction in a fibre Raman amplifier results in a new random birefringence-mediated phenomenon,which is similar to stochastic anti-resonance.The observed phenomenon,apart from the fundamental interest,provides a base for advancing multi-scale methods with application to different coupled nonlinear systems ranging from lasers(multimode,mode-locked,random,etc.)to nanostructures(light-mediated conformation of molecules and chemical reactions,Brownian motors,etc.).
基金supported by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)in the framework of the Collaborative Research Center(CRC)Wave Phenomena(SFB 1173,project-ID 258734477)under Germany's Excellence Strategy via the Excellence Cluster 3D Matter Made to Order(EXC-2082/1–390761711)+4 种基金by the Bundesministerium für Bildung und Forschung(BMBF)within the projects PRIMA(#13N14630),DiFeMiS(#16ES0948),Open6GHub(#16KISK010)by the European Research Council(ERC Consolidator Grant‘TeraSHAPE’,#773248)by the Photonic Packaging Pilot Line PIXAPP(#731954)by the Alfried Krupp von Bohlen und Halbach Foundation,by the Karlsruhe School of Optics and Photonics(KSOP)by the Karlsruhe Nano-Micro Facility(KNMF).A.N.was supported by the Erasmus Mundus Joint Doctorate Programme Europhotonics(grant number 159224-1-2009-1-FR-ERA MUNDUS-EMJD).
文摘Multi-photon lithography has emerged as a powerful tool for photonic integration,allowing to complement planar photonic circuits by 3D-printed freeform structures such as waveguides or micro-optical elements.These structures can be fabricated with a high precision on the facets of optical devices and enable highly efficient package-level chip-chip connections in photonic assemblies.However,plain light transport and efficient coupling is far from exploiting the full geometrical design freedom offered by 3D laser lithography.Here,we extended the functionality of 3D-printed optical structures to manipulation of optical polarisation states.We demonstrate compact ultra-broadband polarisation beam splitters(PBSs)that can be combined with polarisation rotators and mode-field adapters into a monolithic 3D-printed structure,fabricated directly on the facets of optical devices.In a proof-of-concept experiment,we demonstrate measured polarisation extinction ratios beyond 11 dB over a bandwidth of 350 nm at near-infrared telecommunication wavelengths around 1550 nm.We demonstrate the viability of the device by receiving a 640 Gbit/s dual-polarisation data signal using 16-state quadrature amplitude modulation(16QAM),without any measurable optical-signal-to-noise-ratio penalty compared to a commercial PBS.
基金This work was supported partially by the National Natural Science Foundation of China(U2241245)the CAS Interdisciplinary Innovation Team Project(JCTD-2020-10)of China+2 种基金the State Key Laboratory of Light Alloy Casting Technology for High-End Equipment(LACT-007)the Opening project of National Key Laboratory of Shock Wave and Detonation Physics(2022JCJQLB05702)the Original Fund of Nuclear Power Institute of China(kJCX-2022-YC2-20).
文摘The electrochemical behavior of Ti-6Al-4V with 1 mm and 16 mm thickness prepared by electron beam powder bed fusion(EB-PBF)was investigated in phosphate buffered saline.Electrochemical results showed that EB-PBF Ti-6Al-4V with a larger component size was more resistant to corrosion compared to the smaller component,because of less acicularαʹphase content and moreβphase content.As a non-equilibrium phase in the“high-energy state”,αʹphase has a greater susceptibility to corrode and reduces the corrosion resistance of the material,whileβphase improves corrosion resistance of titanium alloys.The results show that the phase composition has a more significant effect on the corrosion performance than the grain size.
文摘Potentiodynamic polarisation, potential-time measurements, X-ray diffraction (XRD) and infrared spectroscopy (IR) have been used to investigate the effect of different concentrations of Na2SO4 in the absence and presence of NaCI, on the corrosion of Cu-alloy. The electrochemical measurements showed that the increase of Na2SO4 concentration led to increase the corrosion current density of Cu alloy and vice versa. The presence of NaCI shifted the potential to more cathodic potential, which had a great influence on the protectiveness of the Cu oxide layer formed on the surface in presence of Na2SO4. The spectrometric measurements indicated the constituents of the film formed on the alloy surface were mainly Cu2O, in addition to the oxides, NiO and Fe2O3, which were traced by XRD analysis.
文摘The effect of tetra ethyl ammonium bromide （TEAB） as an additive on the structural, morphological characteristics of the cobalt metal produced from aqueous sulphate solutions was investigated. The concentration of TEAB was varied in a range of 1-50 mg/L to evaluate its effect on current efficiency, energy consumption and quality of electrodeposited cobalt metal. Smooth and bright deposits of cobalt were obtained at low concentration of TEAB （10 mg/L） maintaining a current efficiency of 99.6%, with a low energy consumption of 2.38 kW＇h/kg. X-ray diffraction studies reveal that （100） plane is the most preferred plane of crystal growth during cobalt electrodeposition. Scanning electron micrographs indicate that smooth and uniform deposit of cobalt is obtained at 10 mg/L beyond which the deposit quality deteriorates. Cyclic voltammetric studies indicate that the presence of TEAB in the electrolytic bath polarizes the cathode and decreases the cathodic current considerably. XPS results confirm the electrodeposition of high pure cobalt with no sign of chemical bonding with TEAB as evident from the FTIR spectra.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60877037 and 10564005)
文摘A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567-575, 605-614 and 656-666 nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre.
基金Project(50974065)supported by the National Natural Science Foundation of ChinaProject(2009009)supported by the Analysis and Testing Foundation of Kunming University of Science and Technology,China
文摘Effect of added Co2 +(aq)on copper electrowinning was studied using doped polyaniline(Pani)and Pb-Ag(1%)anodes and a stainless steel cathode.The presence of added Co2+ (aq)in the electrolyte solution was found to decrease the anode potentials.The optimum level of Co2 +(aq)concentration in the electrolyte,with respect to the maximum saving of power consumption was established.Linear sweep voltammetry(LSV)was used to study the influence of added Co2 +(aq)on the anodic processes in a copper sulfate-sulfuric acid electrolyte.The oxygen-evolution potential for Pani anode is depolarised at lower current densities(≤0.01 A/cm2)and attains saturation atρ(Co 2+ )o≈0.789 g/L;whilst the oxygen-evolution potential for Pb-Ag(1%)anode is depolarised at higher current densities(≤0.02 A/cm2)and attains saturation atρ(Co 2+ )o≈1.315 g/L.The preferred orientations of the copper deposits change from(220)to(111)with the addition of 0.394?0.789 g/L Co 2+ but higher concentrations favor(220)orientation again.
文摘We report the femtosecond(fs)laser fabrication of biomimetic omnidirectional iridescent metallic surfaces exhibiting efficient diffraction for practically any angle of light incidence.Such diffractive behavior is realized by means of multi-directional low-spatial-frequency,laser-induced periodic surface structures(LSFL)formed upon exploiting the cylindrical symmetry of a cylindrical vector(CV)fs field.We particularly demonstrate that the multi-directional gratings formed on stainless steel surface by a radially polarized fs beam,could mimic the omnidirectional structural coloration properties found in some natural species.Accordingly,the fabricated grating structures can spatially disperse the incident light into individual wavelength with high efficiency,exhibiting structural iridescence at all viewing angles.Analytical calculations using the grating equation reproduced the characteristic variation of the vivid colors observed as a function of incident angle.We envisage that our results will significantly contribute to the development of new photonic and light sensing devices.
文摘The corrosion behaviour of the hard anodic coatings prepared by three different methods viz., conventional hard anodizing （C-HA）, pulse hard anodizing （P-HA） and low voltage room temperature pulse hard anodizing （LVP- HA） on AA 6061 was compared using electrochemical impedance spectroscopy （EIS） and linear polarisation. Scanning electron microscope （SEM） was used to study the surface morphology before and after corrosion. EIS data revealed that no significant difference in corrosion resistance was observed among three types. Rp, Icorr and Ecorr were found to be highly stable over the exposure period up to 72 h which confirms the excellent corrosion resistance. The studies indicate that the corrosion resistance of LVP-HA and P-HA, which are processed at lower voltage and at relatively higher temperatures, are comparable to that of C-HA which is processed at sub-zero temperatures and high operating voltages. The corrosion resistance of all coatings was found to be improved after hydrothermal sealing.
基金supported from the Major Program of Science Foundation of Xi’an University of Arts and Science
文摘This paper presents a theoretical study of wavelength dependence four-wave-mixing （FWM） spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke- narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.
