Invisible orthodontic treatment is an effective form of malocclusion treatment favored in recent years.The magnitude of its orthodontic force has a crucial impact on the outcome of the treatment and has gained a high ...Invisible orthodontic treatment is an effective form of malocclusion treatment favored in recent years.The magnitude of its orthodontic force has a crucial impact on the outcome of the treatment and has gained a high level of clinical interest.However,there are very few explorations of in vivo measurements of orthodontic force,and existing studies are limited to a large number of couplings,which are inconvenient for clinical use.In this work,we developed a wireless flexible measurement system that allows quantitative measurement of the orthodontic force of an invisible aligner on a dental model.The system is wireless,tiny,flexible,fast responding,and has a range suitable for the range of orthodontic forces.We show the difference in the orthodontic force applied to different tooth positions and the difference in the orthodontic force applied to different positions of the same tooth.In addition,the system can evaluate the mechanical differences between aligners of different brands and materials as well as the deviation of fabrication results.This system provides a test tool and evaluation method for future real-time assessment of clinical orthodontic forces.展开更多
High resolution of post-stack seismic data assists in better interpretation of subsurface structures as well as high accuracy of impedance inversion. Therefore, geophysicists consistently strive to acquire higher reso...High resolution of post-stack seismic data assists in better interpretation of subsurface structures as well as high accuracy of impedance inversion. Therefore, geophysicists consistently strive to acquire higher resolution seismic images in petroleum exploration. Although there have been successful applications of conventional signal processing and machine learning for post-stack seismic resolution enhancement,there is limited reference to the seismic applications of the recent emergence and rapid development of generative artificial intelligence. Hence, we propose to apply diffusion models, among the most popular generative models, to enhance seismic resolution. Specifically, we apply the classic diffusion model—denoising diffusion probabilistic model(DDPM), conditioned on the seismic data in low resolution, to reconstruct corresponding high-resolution images. Herein the entire scheme is referred to as SeisResoDiff. To provide a comprehensive and clear understanding of SeisResoDiff, we introduce the basic theories of diffusion models and detail the optimization objective's derivation with the aid of diagrams and algorithms. For implementation, we first propose a practical workflow to acquire abundant training data based on the generated pseudo-wells. Subsequently, we apply the trained model to both synthetic and field datasets, evaluating the results in three aspects: the appearance of seismic sections and slices in the time domain, frequency spectra, and comparisons with the synthetic data using real well-logging data at the well locations. The results demonstrate not only effective seismic resolution enhancement,but also additional denoising by the diffusion model. Experimental comparisons indicate that training the model on noisy data, which are more realistic, outperforms training on clean data. The proposed scheme demonstrates superiority over some conventional methods in high-resolution reconstruction and denoising ability, yielding more competitive results compared to our previous research.展开更多
Triptolide (TP), a major active component of Triptelygium wilfordii Hook.F. (TWHF), is used to treat rheumatoid arthritis (RA). However, it has a narrow therapeutic window due to its serious toxicities. To increase th...Triptolide (TP), a major active component of Triptelygium wilfordii Hook.F. (TWHF), is used to treat rheumatoid arthritis (RA). However, it has a narrow therapeutic window due to its serious toxicities. To increase the therapeutic index, a new triptolide-loaded transdermal delivery system, named triptolide-loaded liposome hydrogel patch (TP-LHP), has been developed. In this paper, we used a micro-needle array to deliver TP-LHP to promote transdermal absorption and evaluated this treatment on the pharmacokinetics and pharmacodynamics of TP-LHP in a rat model of collagen-induced arthritis (CIA). The pharmacokinetic results showed that transdermal delivery of microneedle TP-LHP yielded plasma drug levels which fit a one compartment open model. The relationship equation between plasma concentration and time was C=303.59 x (e(-0.064t)-e(-0.287t)). The results of pharmacodynamic study demonstrated that TP-LHP treatment mitigated the degree of joint swelling and suppressed the expressions of fetal liver kinase-1, fetal liver tyrosine kinase-4 and hypoxia-inducible factor-1a in synovium. Other indicators were also reduced by TP-LHP, including hyperfunction of immune, interleukin-1/3 and interleukin-6 levels in serum. The therapeutic mechanism of TP-LHP might be regulation of the balance between Thl and Th2, as well as inhibition of the expression and biological effects of vascular endothelial growth factor. (C) 2015 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.展开更多
InAs is a direct, narrow band gap （0.354 eV） material with ultrahigh electron mobility, and is potentially a good optoelectronic device candidate in the wide UV-visible-near-infrared region. In this work we report t...InAs is a direct, narrow band gap （0.354 eV） material with ultrahigh electron mobility, and is potentially a good optoelectronic device candidate in the wide UV-visible-near-infrared region. In this work we report the fabrication of InAs nanowire-based photodetectors, which showed a very high photoresponse over a broad spectral range from 300 to 1,100 nm. The responsivity, external quantum efficiency and detectivity of the device were respectively measured to be 4.4 × 103 AW , 1.03 × 106%, and 2.6 × 1011 Jones to visible incident light. Time dependent measurements at different wavelengths and under different light intensities also demonstrated the fast, reversible, and stable photoresponse of our device. Theoretical calculations of the optical absorption and the electric field component distribution were also performed to elucidate the mechanism of the enhanced photoresponse. Our results demonstrate that the single-crystalline InAs NWs are very promising candidates for the design of high sensitivity and high stability nanoscale photodetectors with a broad band photoresponse.展开更多
The size of metal nanoparticles is a key factor to enhance the photocatalytic activity of photocatalysts.However,the mechanism of this factor to the improvement of photocatalytic CO_(2) reduction performance is still ...The size of metal nanoparticles is a key factor to enhance the photocatalytic activity of photocatalysts.However,the mechanism of this factor to the improvement of photocatalytic CO_(2) reduction performance is still unclear.Here,Au cluster/TiO_(2)/Ti_(3)C_(2) and Au nanoparticle/TiO_(2)/Ti_(3)C_(2) were successfully prepared by deposition-precipitation method.The experimental results show that the photocatalytic CO_(2) reduction performance of Au cluster/TiO_(2)/Ti_(3)C_(2) with quantum size effect is stronger than that of Au nanoparticle/TiO_(2)/Ti_(3)C_(2) with surface plasmon resonance.The enhanced photocatalytic CO_(2) reduction activity is assigned to the establishment of an overlapping orbital between the lowest unoccupied molecular orbital(LUMO)of the Au cluster and the anti-bonding orbital of CO_(2),which greatly promotes the activation efficiency of CO_(2).The existence of Au cluster and the mechanism of photocatalytic CO_(2) reduction performance were certified by high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)and in situ Fourier transform infrared spectroscopy(ISFTIR).This work may open new opportunities for the establishment of stable and active metal nanocatalysts.展开更多
Transparent metal oxide nanowires （NWs） have attracted intense research interest in recent years. We report here the synthesis of interesting ladder-like metal oxide NWs, including In2O3, SnO2, ZnO, and Ga2O3, via a...Transparent metal oxide nanowires （NWs） have attracted intense research interest in recent years. We report here the synthesis of interesting ladder-like metal oxide NWs, including In2O3, SnO2, ZnO, and Ga2O3, via a facile chemical vapor deposition （CVD） method. Their structural features and growth mechanism are demonstrated in detail by using the ladder-like In2O3 NWs as an example. Single ladder-like NW-based field-effect transistors （FETs） and photodetectors （PDs） of SnO2 were fabricated in order to investigate their electrical transport and light absorption properties. Compared with straight NW-based FETs which operate in an enhancement mode （E-mode）, FETs build on ladder-like NWs operate in a depletion mode （D-mode）. The ladder-like NWs also give higher carrier concentrations than conventional single nanowires. Finite-difference time-domain （FDTD） simulations have been performed on the ladder-like NWs and the results reveal a great enhancement of light absorption with both transverse-electric （TE） and transverse-magnetic （TM） polarization modes, which is in good agreement with the experimental results.展开更多
The radical suppression of the photodarkening effect and laser performance deterioration via H2 loading were demonstrated in high-power Yb-doped fiber(YDF)amplifiers.The photodarkening loss at equilibrium was114.4 d B...The radical suppression of the photodarkening effect and laser performance deterioration via H2 loading were demonstrated in high-power Yb-doped fiber(YDF)amplifiers.The photodarkening loss at equilibrium was114.4 d B/m at 702 nm in the pristine fiber,while it vanished in the H2-loaded fiber.To obtain a deeper understanding of the impact of photodarkening on laser properties,the evolution of the mode instability threshold and output power in fiber amplifiers was investigated.After pumping for 300 min,the mode instability threshold of the pristine fiber dropped from 770 to 612 W,and the periodic fluctuation of the output power became intense,finally reaching 100 W.To address the detrimental effects originating from photodarkening,H2 loading was applied in contrast experiments.The output power remained stable,and no sign of mode instability was observed in the H2-loaded fiber.Moreover,the transmittance at 638 nm confirmed the absence of the photodarkening effect.The results pave the way for the further development of high-power fiber lasers.展开更多
Considering that hydrogen peroxide(H2O2)plays significant roles in oxidative stress,the cellular signal transduction and essential biological process regulation,the detection and imaging of H2O2 in living systems unde...Considering that hydrogen peroxide(H2O2)plays significant roles in oxidative stress,the cellular signal transduction and essential biological process regulation,the detection and imaging of H2O2 in living systems undertakes critical responsibility.Herein,we have developed a novel two-photon fluorescence turn on probe,named as Pyp-B for mitochondria H2O2 detection in living systems.Selectivity studies show that probe Pyp-B exhibit highly sensitive response toward H2O2 than other reactive oxygen species(ROS)and reactive nitrogen species(RNS)as well as biologically relevant species.The fluorescence colocalization studies demonstrate that the probe can localize in the mitochondria solely.Furthermore,as a bio-compatibility molecule,the highly selective and sensitive of fluorescence probe Pyp-B have been confirmed by its cell imaging application of H2O2 in living A549 cells and zebrafishes under the physiological conditions.展开更多
Ytterbium-doped fibers have become the optimum gain media of high-power fiber lasers thanks to a simple energy structure, which strongly reduces the excited state absorption, and a low quantum defect and a high optic...Ytterbium-doped fibers have become the optimum gain media of high-power fiber lasers thanks to a simple energy structure, which strongly reduces the excited state absorption, and a low quantum defect and a high optic–optic conversion efficiency, which means the low thermal load. In this paper, we take a review of the current state of the art in terms of Yb^(3+)doped fibers for high-power fiber lasers, including the development of the fabrication techniques. The research work to overcome the challenges for Yb3+doped fibers, which affect the stability of output power and beam quality, will be demonstrated. Direction of further research is presented and the goal is to look for a fiber design, to boost single fiber output power, stabilize the laser power and support robust single-mode operation.展开更多
In this work, non-isothermal bleaching of Yb–Li co-doped fiber was investigated. The Yb–Li co-doped fiber was beneficial to reduce the photodarkening-induced excess loss and had no bad effect on the temperature of t...In this work, non-isothermal bleaching of Yb–Li co-doped fiber was investigated. The Yb–Li co-doped fiber was beneficial to reduce the photodarkening-induced excess loss and had no bad effect on the temperature of thermal bleaching(TB). Photodarkened fibers were bleached with different temperature ramp rates. The higher the ramp rate, the higher the complete bleaching temperature. The activation energy of the bleaching of Yb/Al/Li fiber was calculated by fitting, which was similar to that of an Yb-doped fiber. These observations are helpful in revealing the relationship between the mechanism of Li ion co-doping and TB.展开更多
An urgent demand for lowering bonding temperature has been put forward by advanced flip-chip integration such as micro-LED packaging and heterogeneous integration of semiconductor devices.Indium microbump with low-mel...An urgent demand for lowering bonding temperature has been put forward by advanced flip-chip integration such as micro-LED packaging and heterogeneous integration of semiconductor devices.Indium microbump with low-melting point has attracted attention for its potential use as the interconnection intermediate,and the development of its fabrication process is therefore of great attraction.To reveal the critical process factors for successfully fabricating a high-density In microbump array,this paper investigated a simple process flow of In patterning and reflow and detailed the flux-assisted wet reflow process.Critical process conditions,including the patterned In volume,alignment accuracy,reflow reagent liquidity,and temperature profile,were described,with a particular emphasis on the role of surface tension of molten indium film during the formation of spherical microbumps.A high-density indium ball array with an overall yield greater than 99.7%can be obtained,which suggests that the In patterning and wet-reflow processes are robust and that a high-quality microbump array could be readily formed with low equipment requirements.Furthermore,the interfacial reaction characteristics between In microbump and Au adhesion layer were investigated under thermal aging conditions,which revealed lateral intermetallic growth of AuIn2 compound and well-retained interfacial strength even after prolonged aging.展开更多
The designed synthesis of chiral covalent organic frameworks(COFs) featuring intriguing properties is fairly scant and remains a daunting synthetic challenge.Here we develop a de novo synthesis of an enantiomeric pair...The designed synthesis of chiral covalent organic frameworks(COFs) featuring intriguing properties is fairly scant and remains a daunting synthetic challenge.Here we develop a de novo synthesis of an enantiomeric pair of 2 D hydroxyl-functionalized hydrazone-linked chiral COFs,(S)-and(R)-HthBta-OH COFs,using enantiopure 2,5-bis(2-hydroxypropoxy)terephthalohydrazide(Hth) as monomers.The fo rmation process of hydroxyl-functionalized chiral COFs was monitored using rigorous time-dependent PXRD,vibrational circular dichroism(VCD),and electronic circular dichroism(ECD) studies.Remarkably,VCD spectra indicated a unique chiral signal inversion from the positive Cotton effect of(S)-Hth monomer to the negative Cotton effect of(S)-HthBta-OH COF,which has never been reported in chiral COFs.Moreover,two unprecedented carboxyl-functionalized chiral COFs,(S)-and(R)-HthBta-COOH,were constructed by a post-synthetic modification of the corresponding hydroxyl chiral COFs with succinic anhydride.Notably,carboxyl-functionalized COFs retained homochirality and crystallinity without linker racemization and structural collapse after the chemical modification due to the chemically robust nature of pristine hydrazone-linked chiral COFs.展开更多
基金Beijing Natural Science Foundation(L232109)National Natural Science Foundation of China(No.12202274 and No.52171234)+1 种基金Fundamental Research Funds for the Central Universities(YWF-22-K-101)National Key Research and Development Project(Nos.2021YFC2400703 and 2019YFE0101100).
文摘Invisible orthodontic treatment is an effective form of malocclusion treatment favored in recent years.The magnitude of its orthodontic force has a crucial impact on the outcome of the treatment and has gained a high level of clinical interest.However,there are very few explorations of in vivo measurements of orthodontic force,and existing studies are limited to a large number of couplings,which are inconvenient for clinical use.In this work,we developed a wireless flexible measurement system that allows quantitative measurement of the orthodontic force of an invisible aligner on a dental model.The system is wireless,tiny,flexible,fast responding,and has a range suitable for the range of orthodontic forces.We show the difference in the orthodontic force applied to different tooth positions and the difference in the orthodontic force applied to different positions of the same tooth.In addition,the system can evaluate the mechanical differences between aligners of different brands and materials as well as the deviation of fabrication results.This system provides a test tool and evaluation method for future real-time assessment of clinical orthodontic forces.
基金supported by the National Natural Science Foundation of China (NSFC): Grant number 42274147。
文摘High resolution of post-stack seismic data assists in better interpretation of subsurface structures as well as high accuracy of impedance inversion. Therefore, geophysicists consistently strive to acquire higher resolution seismic images in petroleum exploration. Although there have been successful applications of conventional signal processing and machine learning for post-stack seismic resolution enhancement,there is limited reference to the seismic applications of the recent emergence and rapid development of generative artificial intelligence. Hence, we propose to apply diffusion models, among the most popular generative models, to enhance seismic resolution. Specifically, we apply the classic diffusion model—denoising diffusion probabilistic model(DDPM), conditioned on the seismic data in low resolution, to reconstruct corresponding high-resolution images. Herein the entire scheme is referred to as SeisResoDiff. To provide a comprehensive and clear understanding of SeisResoDiff, we introduce the basic theories of diffusion models and detail the optimization objective's derivation with the aid of diagrams and algorithms. For implementation, we first propose a practical workflow to acquire abundant training data based on the generated pseudo-wells. Subsequently, we apply the trained model to both synthetic and field datasets, evaluating the results in three aspects: the appearance of seismic sections and slices in the time domain, frequency spectra, and comparisons with the synthetic data using real well-logging data at the well locations. The results demonstrate not only effective seismic resolution enhancement,but also additional denoising by the diffusion model. Experimental comparisons indicate that training the model on noisy data, which are more realistic, outperforms training on clean data. The proposed scheme demonstrates superiority over some conventional methods in high-resolution reconstruction and denoising ability, yielding more competitive results compared to our previous research.
基金supported by National Science and Technology Major Project on Significant Creation of New Drugs of China(2009ZX09502-019)
文摘Triptolide (TP), a major active component of Triptelygium wilfordii Hook.F. (TWHF), is used to treat rheumatoid arthritis (RA). However, it has a narrow therapeutic window due to its serious toxicities. To increase the therapeutic index, a new triptolide-loaded transdermal delivery system, named triptolide-loaded liposome hydrogel patch (TP-LHP), has been developed. In this paper, we used a micro-needle array to deliver TP-LHP to promote transdermal absorption and evaluated this treatment on the pharmacokinetics and pharmacodynamics of TP-LHP in a rat model of collagen-induced arthritis (CIA). The pharmacokinetic results showed that transdermal delivery of microneedle TP-LHP yielded plasma drug levels which fit a one compartment open model. The relationship equation between plasma concentration and time was C=303.59 x (e(-0.064t)-e(-0.287t)). The results of pharmacodynamic study demonstrated that TP-LHP treatment mitigated the degree of joint swelling and suppressed the expressions of fetal liver kinase-1, fetal liver tyrosine kinase-4 and hypoxia-inducible factor-1a in synovium. Other indicators were also reduced by TP-LHP, including hyperfunction of immune, interleukin-1/3 and interleukin-6 levels in serum. The therapeutic mechanism of TP-LHP might be regulation of the balance between Thl and Th2, as well as inhibition of the expression and biological effects of vascular endothelial growth factor. (C) 2015 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.
基金Acknowledgements This work was supported by the National Natural Science Foundation （Nos. 91123008, 51002059, 21001046）, the 973 Program of China （No. 2011CB933300）, and the Program for New Century Excellent Talents of the Universities in China （grant No. NCET-11-0179）. We thank the Analytical and Testing Center of Huazhong University of Science and Technology for measurements.
文摘InAs is a direct, narrow band gap （0.354 eV） material with ultrahigh electron mobility, and is potentially a good optoelectronic device candidate in the wide UV-visible-near-infrared region. In this work we report the fabrication of InAs nanowire-based photodetectors, which showed a very high photoresponse over a broad spectral range from 300 to 1,100 nm. The responsivity, external quantum efficiency and detectivity of the device were respectively measured to be 4.4 × 103 AW , 1.03 × 106%, and 2.6 × 1011 Jones to visible incident light. Time dependent measurements at different wavelengths and under different light intensities also demonstrated the fast, reversible, and stable photoresponse of our device. Theoretical calculations of the optical absorption and the electric field component distribution were also performed to elucidate the mechanism of the enhanced photoresponse. Our results demonstrate that the single-crystalline InAs NWs are very promising candidates for the design of high sensitivity and high stability nanoscale photodetectors with a broad band photoresponse.
基金financially supported by the National Natural Science Foundation of China(Nos.51672099 and 52073263)Sichuan Science and Technology Program(No.2021JDTD0026)+1 种基金the Fundamental Research Funds for the Central Universities(No.2017-QR-25)the Research Team Project of Dongguan University of Technology(Nos.TDYB2019014 and TDQN2019011)。
文摘The size of metal nanoparticles is a key factor to enhance the photocatalytic activity of photocatalysts.However,the mechanism of this factor to the improvement of photocatalytic CO_(2) reduction performance is still unclear.Here,Au cluster/TiO_(2)/Ti_(3)C_(2) and Au nanoparticle/TiO_(2)/Ti_(3)C_(2) were successfully prepared by deposition-precipitation method.The experimental results show that the photocatalytic CO_(2) reduction performance of Au cluster/TiO_(2)/Ti_(3)C_(2) with quantum size effect is stronger than that of Au nanoparticle/TiO_(2)/Ti_(3)C_(2) with surface plasmon resonance.The enhanced photocatalytic CO_(2) reduction activity is assigned to the establishment of an overlapping orbital between the lowest unoccupied molecular orbital(LUMO)of the Au cluster and the anti-bonding orbital of CO_(2),which greatly promotes the activation efficiency of CO_(2).The existence of Au cluster and the mechanism of photocatalytic CO_(2) reduction performance were certified by high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)and in situ Fourier transform infrared spectroscopy(ISFTIR).This work may open new opportunities for the establishment of stable and active metal nanocatalysts.
基金This work was supported by the National Natural Science Foundation of China （Nos. 61377033 and 91123008）, the 973 Program of China （No. 2011CB933300）, and the Program for New Century Excellent Talents of the University in China （Grant No. NCET-11-0179）.
文摘Transparent metal oxide nanowires （NWs） have attracted intense research interest in recent years. We report here the synthesis of interesting ladder-like metal oxide NWs, including In2O3, SnO2, ZnO, and Ga2O3, via a facile chemical vapor deposition （CVD） method. Their structural features and growth mechanism are demonstrated in detail by using the ladder-like In2O3 NWs as an example. Single ladder-like NW-based field-effect transistors （FETs） and photodetectors （PDs） of SnO2 were fabricated in order to investigate their electrical transport and light absorption properties. Compared with straight NW-based FETs which operate in an enhancement mode （E-mode）, FETs build on ladder-like NWs operate in a depletion mode （D-mode）. The ladder-like NWs also give higher carrier concentrations than conventional single nanowires. Finite-difference time-domain （FDTD） simulations have been performed on the ladder-like NWs and the results reveal a great enhancement of light absorption with both transverse-electric （TE） and transverse-magnetic （TM） polarization modes, which is in good agreement with the experimental results.
基金National Natural Science Foundation of China(61735007)National Key Research and Development Program of China(2017YFB1104400)。
文摘The radical suppression of the photodarkening effect and laser performance deterioration via H2 loading were demonstrated in high-power Yb-doped fiber(YDF)amplifiers.The photodarkening loss at equilibrium was114.4 d B/m at 702 nm in the pristine fiber,while it vanished in the H2-loaded fiber.To obtain a deeper understanding of the impact of photodarkening on laser properties,the evolution of the mode instability threshold and output power in fiber amplifiers was investigated.After pumping for 300 min,the mode instability threshold of the pristine fiber dropped from 770 to 612 W,and the periodic fluctuation of the output power became intense,finally reaching 100 W.To address the detrimental effects originating from photodarkening,H2 loading was applied in contrast experiments.The output power remained stable,and no sign of mode instability was observed in the H2-loaded fiber.Moreover,the transmittance at 638 nm confirmed the absence of the photodarkening effect.The results pave the way for the further development of high-power fiber lasers.
基金the financial support from the National Natural Science Foundation of China(No.81860630)the China Postdoctoral Science Foundation(No.2019M662968)GuangdongBasic and Applied Basic Research Foundation(Nos.2019A1515110356,2019A1515110877)。
文摘Considering that hydrogen peroxide(H2O2)plays significant roles in oxidative stress,the cellular signal transduction and essential biological process regulation,the detection and imaging of H2O2 in living systems undertakes critical responsibility.Herein,we have developed a novel two-photon fluorescence turn on probe,named as Pyp-B for mitochondria H2O2 detection in living systems.Selectivity studies show that probe Pyp-B exhibit highly sensitive response toward H2O2 than other reactive oxygen species(ROS)and reactive nitrogen species(RNS)as well as biologically relevant species.The fluorescence colocalization studies demonstrate that the probe can localize in the mitochondria solely.Furthermore,as a bio-compatibility molecule,the highly selective and sensitive of fluorescence probe Pyp-B have been confirmed by its cell imaging application of H2O2 in living A549 cells and zebrafishes under the physiological conditions.
文摘Ytterbium-doped fibers have become the optimum gain media of high-power fiber lasers thanks to a simple energy structure, which strongly reduces the excited state absorption, and a low quantum defect and a high optic–optic conversion efficiency, which means the low thermal load. In this paper, we take a review of the current state of the art in terms of Yb^(3+)doped fibers for high-power fiber lasers, including the development of the fabrication techniques. The research work to overcome the challenges for Yb3+doped fibers, which affect the stability of output power and beam quality, will be demonstrated. Direction of further research is presented and the goal is to look for a fiber design, to boost single fiber output power, stabilize the laser power and support robust single-mode operation.
基金supported by the National Key Research and Development Program of China(No.2017YFB1104400)the National Natural Science Foundation of China(No.61735007)
文摘In this work, non-isothermal bleaching of Yb–Li co-doped fiber was investigated. The Yb–Li co-doped fiber was beneficial to reduce the photodarkening-induced excess loss and had no bad effect on the temperature of thermal bleaching(TB). Photodarkened fibers were bleached with different temperature ramp rates. The higher the ramp rate, the higher the complete bleaching temperature. The activation energy of the bleaching of Yb/Al/Li fiber was calculated by fitting, which was similar to that of an Yb-doped fiber. These observations are helpful in revealing the relationship between the mechanism of Li ion co-doping and TB.
基金funded by the National Natural Science Foundation of China(Grant No.U20A6004)the Natural Science Foundation of Hunan Province(Grant No.2021JJ40734)+1 种基金the State Key Laboratory of High Performance Complex Manufacturing(Grant No.ZZYJKT2020-08)the Key Project of Science and Technology of Changsha(Grant No.kq2102005).
文摘An urgent demand for lowering bonding temperature has been put forward by advanced flip-chip integration such as micro-LED packaging and heterogeneous integration of semiconductor devices.Indium microbump with low-melting point has attracted attention for its potential use as the interconnection intermediate,and the development of its fabrication process is therefore of great attraction.To reveal the critical process factors for successfully fabricating a high-density In microbump array,this paper investigated a simple process flow of In patterning and reflow and detailed the flux-assisted wet reflow process.Critical process conditions,including the patterned In volume,alignment accuracy,reflow reagent liquidity,and temperature profile,were described,with a particular emphasis on the role of surface tension of molten indium film during the formation of spherical microbumps.A high-density indium ball array with an overall yield greater than 99.7%can be obtained,which suggests that the In patterning and wet-reflow processes are robust and that a high-quality microbump array could be readily formed with low equipment requirements.Furthermore,the interfacial reaction characteristics between In microbump and Au adhesion layer were investigated under thermal aging conditions,which revealed lateral intermetallic growth of AuIn2 compound and well-retained interfacial strength even after prolonged aging.
基金We are grateful for the financial support from the National Natural Science Foundation of China(Nos.21603076 and 21571070)the Natural Science Foundation of Guangdong Province(No.2018A030313193).
文摘The designed synthesis of chiral covalent organic frameworks(COFs) featuring intriguing properties is fairly scant and remains a daunting synthetic challenge.Here we develop a de novo synthesis of an enantiomeric pair of 2 D hydroxyl-functionalized hydrazone-linked chiral COFs,(S)-and(R)-HthBta-OH COFs,using enantiopure 2,5-bis(2-hydroxypropoxy)terephthalohydrazide(Hth) as monomers.The fo rmation process of hydroxyl-functionalized chiral COFs was monitored using rigorous time-dependent PXRD,vibrational circular dichroism(VCD),and electronic circular dichroism(ECD) studies.Remarkably,VCD spectra indicated a unique chiral signal inversion from the positive Cotton effect of(S)-Hth monomer to the negative Cotton effect of(S)-HthBta-OH COF,which has never been reported in chiral COFs.Moreover,two unprecedented carboxyl-functionalized chiral COFs,(S)-and(R)-HthBta-COOH,were constructed by a post-synthetic modification of the corresponding hydroxyl chiral COFs with succinic anhydride.Notably,carboxyl-functionalized COFs retained homochirality and crystallinity without linker racemization and structural collapse after the chemical modification due to the chemically robust nature of pristine hydrazone-linked chiral COFs.
