The effective extracting Cr(Ⅵ) from chromite ore processing residue(COPR) is the key to achieve COPR detoxification and recovery.We developed an effective method to extract Cr(Ⅵ) from COPR via controlling the phase ...The effective extracting Cr(Ⅵ) from chromite ore processing residue(COPR) is the key to achieve COPR detoxification and recovery.We developed an effective method to extract Cr(Ⅵ) from COPR via controlling the phase transformation of Cr(Ⅵ)-containing minerals.Characteristic analysis showed that Cr(Ⅵ) was mainly incorporated in the hydrocalumite(NaCa4Al2O6(SO4/CrO4)1.5-15H2O) in COPR,which was a layered-double hydroxide(LDH) with multilayer structure.In the hydrothermal treatment experiments,the Na2CO3 solution showed significant extraction effect of Cr(Ⅵ) and detoxification effect of COPR.After treatment,95% of Cr(Ⅵ) was removed and the Cr(Ⅵ) concentration in the leachate was decreased to 1.6 mg/L by the toxicity characteristic leaching procedure(TCLP),within the regulatory limit disposal standard(HJ/T 301-2007,3 mg/L).Further study revealed that,during the treatment,hydrocalumite transformed into calcite(CaCO3) under the effect of mineralizer,therefore,the layered structure collapsed and the incorporated Cr(Ⅵ) was released to the supernatant.Meanwhile,the Cr(Ⅵ)desorbed from calcite with the calcite particles grew into large size with smooth surface.Stir-flow experiment revealed that the amount of chromium released from CORP to the environment was significantly reduced after treatment,and it is safer for landfill disposal.This work will provide an instructive guidance for the detoxification and recovery of COPR.展开更多
Complex networked systems,which range from biological systems in the natural world to infrastructure systems in the human-made world,can exhibit spontaneous recovery after a failure;for example,a brain may spontaneous...Complex networked systems,which range from biological systems in the natural world to infrastructure systems in the human-made world,can exhibit spontaneous recovery after a failure;for example,a brain may spontaneously return to normal after a seizure,and traffic flow can become smooth again after a jam.Previous studies on the spontaneous recovery of dynamical networks have been limited to undirected networks.However,most real-world networks are directed.To fill this gap,we build a model in which nodes may alternately fail and recover,and we develop a theoretical tool to analyze the recovery properties of directed dynamical networks.We find that the tool can accurately predict the final fraction of active nodes,and the prediction accuracy decreases as the fraction of bidirectional links in the network increases,which emphasizes the importance of directionality in network dynamics.Due to different initial states,directed dynamical networks may show alternative stable states under the same control parameter,exhibiting hysteresis behavior.In addition,for networks with finite sizes,the fraction of active nodes may jump back and forth between high and low states,mimicking repetitive failure-recovery processes.These findings could help clarify the system recovery mechanism and enable better design of networked systems with high resilience.展开更多
Nowadays,crowded environment and high-speed life pace are likely to bring mental stress and fatigue to citizens.How to apply achievements of the restorative environment into urban planning and environmental design has...Nowadays,crowded environment and high-speed life pace are likely to bring mental stress and fatigue to citizens.How to apply achievements of the restorative environment into urban planning and environmental design has received more attention in recent years.Earlier research does not provide detailed information about the specific components of the physical environment that support restoration.This study explores which characteristics of the street environment and psychological factors of the street environment have an impact on subjective restoration.The streets were sampled from Shenzhen.Each street was represented by a single photo.The photo was quantified in terms of the different objective street components and also rated on psychological variables related to restoration.The rating on the psychological variables,being away,fascination,coherence,scope,the likelihood of restoration,and preference were provided by people of various ages and occupations.The results show that:1)the proportion of natural elements have the greatest impact on street restoration benefits and preference,and its impact is robust;2)the two characteristics of street safety and quiet are important to street restoration benefits and preferences;3)fascination and being away have a greater impact on restorative benefits of streets,followed by coherence,and the scope of the street has no significant effect on restorative benefits.The study could provide evidence for policy-makers and urban design and planning interventions.展开更多
Ecosystems are undergoing unprecedented persistent deterioration due to unsustainable anthropogenic human activities,such as overfishing and deforestation,and the effects of such damage on ecological stability are unc...Ecosystems are undergoing unprecedented persistent deterioration due to unsustainable anthropogenic human activities,such as overfishing and deforestation,and the effects of such damage on ecological stability are uncertain.Despite recent advances in experimental and theoretical studies on regime shifts and tipping points,theoretical tools for understanding the extinction chain,which is the sequence of species extinctions resulting from overexploitation,are still lacking,especially for large-scale nonlinear networked systems.In this study,we developed a mathematical tool to predict regime shifts and extinction chains in ecosystems under multiple exploitation situations and verified it in 26 real-world mutualistic networks of various sizes and densities.We discovered five phases during the exploitation process:safe,partial extinction,bistable,tristable,and collapse,which enabled the optimal design of restoration strategies for degraded or collapsed systems.We validated our approach using a 20-year dataset from an eelgrass restoration project.Counterintuitively,we also found a specific region in the diagram spanning exploitation rates and competition intensities,where exploiting more species helps increase biodiversity.Our computational tool provides insights into harvesting,fishing,exploitation,or deforestation plans while conserving or restoring the biodiversity of mutualistic ecosystems.展开更多
In target-based drug design,the manual creation of a poor initial compound library,the time-consuming wetlaboratory experimental screening method,and the weak explainability of their activity against compounds signifi...In target-based drug design,the manual creation of a poor initial compound library,the time-consuming wetlaboratory experimental screening method,and the weak explainability of their activity against compounds significantly limit the efficiency of discovering novel therapeutics.Here we propose an image-guided,interpretability deep learning workflow,named LeadDisFlow,to enable rapid,accurate target drug discovery.Using LeadDisFlow,we identified four potent antagonists with single-nanomolar antagonistic activity against PGE2 receptor subtype 4(EP4),a promising target for tumor im-munotherapy.Remarkably,the most potent EP4 antagonist,ZY001,demonstrated an IC50 value of(0.51±0.02)nM,along with high selectivity.Furthermore,ZY001 effectively impaired the PGE2-induced gene expression of a panel of immunosuppressive molecules in macrophages.The workflow facilitates the discovery of potent EP4 antagonists that enhance anti-tumor immune response,and provides a convenient and quick approach to discover promising therapeutics for a specific drug target.展开更多
The dispersive Fourier transform(DFT) technique opens a fascinating pathway to explore ultrafast non-repetitive events and has been employed to study the build-up process of mode-locked lasers. However, the shutting p...The dispersive Fourier transform(DFT) technique opens a fascinating pathway to explore ultrafast non-repetitive events and has been employed to study the build-up process of mode-locked lasers. However, the shutting process for the mode-locked fiber laser seems to be beyond the scope of researchers, and the starting dynamics under nearzero dispersion remains unclear. Here, the complete evolution dynamics(from birth to extinction) of the conventional soliton(CS), stretched pulse(SP), and dissipative soliton(DS) are investigated by using the DFT technique.CS, SP, and DS fiber lasers mode locked by single-walled carbon nanotubes(SWNTs) are implemented via engineering the intracavity dispersion map. The relaxation oscillation can always be observed before the formation of stable pulse operation due to the inherent advantage of SWNT, but it exhibits distinct evolution dynamics in the starting and shutting processes. The shutting processes are dependent on the dispersion condition and turn-off time, which is against common sense. Some critical phenomena are also observed, including transient complex spectrum broadening and frequency-shift interaction of SPs and picosecond pulses. These results will further deepen understanding of the mode-locked fiber laser from a real-time point of view and are helpful for laser design and applications.展开更多
Converting carbon dioxide(CO_(2))to diverse value-added products through photocatalysis can validly alleviate the critical issues of greenhouse effect and energy shortages simultaneously.In particular,based on practic...Converting carbon dioxide(CO_(2))to diverse value-added products through photocatalysis can validly alleviate the critical issues of greenhouse effect and energy shortages simultaneously.In particular,based on practical considerations,exploring novel catalysts to achieve efficient photoreduction of diluted CO_(2) is necessary and urgent.However,this process is extremely challenging owing to the disturbance of competitive adsorption at low CO_(2) concentration.Herein,we delicately synthesize oxygen vacancy-laden NiO nanoplatelets(r-NiO)via calcination under Ar protection to reduce diluted CO_(2) through visible light irradiation(>400 nm)assisted by a Ru-based photosensitizer.Benefitting from the strongly CO_(2) adsorption energy of oxygen vacancies,which was confirmed by density functional calculations,the r-NiO catalysts exhibit higher activity and selectivity(6.28×10^(3)µmol·h^(−1)·g^(−1);82.11%)for diluted CO_(2)-to-CO conversion than that of the normal NiO(3.94×10^(3)µmol·h^(−1)·g^(−1);65.26%).Besides,the presence of oxygen vacancies can also promote the separation of electron-hole pairs.Our research demonstrates that oxygen vacancies could act as promising candidates for photocatalytic CO_(2) reduction,offering fundamental guidance for the actual photoreduction of diluted CO_(2) in the future.展开更多
Real-time spectroscopy based on an emerging time-stretch technique can map the spectral information of optical waves into the time domain,opening several fascinating explorations of nonlinear dynamics in mode-locked l...Real-time spectroscopy based on an emerging time-stretch technique can map the spectral information of optical waves into the time domain,opening several fascinating explorations of nonlinear dynamics in mode-locked lasers.However,the self-starting process of mode-locked lasers is quite sensitive to environmental perturbation,which causes the transient behaviors of lasers to deviate from the true buildup process of solitons.We optimize the laser system to improve its stability,which suppresses the Q-switched lasing induced by environmental perturbation.We,therefore,demonstrate the first observation of the entire buildup process of solitons in a mode-locked laser,revealing two possible pathways to generate the temporal solitons.One pathway includes the dynamics of raised relaxation oscillation,quasimode-locking stage,spectral beating behavior,and finally the stable single-soliton mode-locking.The other pathway contains,however,an extra transient bound-state stage before the final single-pulse modelocking operation.Moreover,we propose a theoretical model to predict the buildup time of solitons,which agrees well with the experimental results.Our findings can bring real-time insights into ultrafast fiber laser design and optimization,as well as promote the application of fiber laser.展开更多
We investigate the properties of spatial solitons in the fractional Schr?dinger equation(FSE) with parity-time(PT)-symmetric lattice potential supported by the focusing of Kerr nonlinearity. Both one-and two-dimension...We investigate the properties of spatial solitons in the fractional Schr?dinger equation(FSE) with parity-time(PT)-symmetric lattice potential supported by the focusing of Kerr nonlinearity. Both one-and two-dimensional solitons can stably propagate in PT-symmetric lattices under noise perturbations. The domains of stability for both one-and two-dimensional solitons strongly depend on the gain/loss strength of the lattice. In the spatial domain, the solitons are rigidly modulated by the lattice potential for the weak diffraction in FSE systems. In the inverse space, due to the periodicity of lattices, the spectra of solitons experience sharp peaks when the values of wavenumbers are even. The transverse power flows induced by the imaginary part of the lattice are also investigated, which can preserve the internal energy balances within the solitons.展开更多
The ultrafast fiber laser has attracted a great deal of research interest due to its low cost, high efficiency, and simple maintenance. Optical passive devices are vital parts of a fiber laser. In order to obtain a fi...The ultrafast fiber laser has attracted a great deal of research interest due to its low cost, high efficiency, and simple maintenance. Optical passive devices are vital parts of a fiber laser. In order to obtain a fiber laser with high quality, optical passive devices with high performance are required. Here, we demonstrate a highly integrated optical device with the combination of a saturable absorber(SA), coupler, isolator, wavelength division multiplexer, and erbium-doped fiber. The built-in SA has a modulation depth of 7% and can withstand high pump power due to the unique structure of the proposed device. The proposed device is applied to an ultracompact fiber laser, which greatly simplifies the laser structure and reduces the size of the proposed laser. The central wavelength, pulse duration, repetition rate, and signal-to-noise ratio of the output soliton are 1560 nm, 1.06 ps,25.8 MHz, and 50 dB, respectively. The proposed device has great potential for application in high-power and high-frequency fiber lasers. The proposed ultracompact fiber laser has important applications in optical communication, optical sensing, optical frequency combs, and micromachining.展开更多
Reflective fiber optic sensors have advantages for surface roughness measurements of some special workpieces,but their measuring precision and efficiency need to be improved further. A least-squares support vector mac...Reflective fiber optic sensors have advantages for surface roughness measurements of some special workpieces,but their measuring precision and efficiency need to be improved further. A least-squares support vector machine（LS-SVM）-based surface roughness prediction model is proposed to estimate the surface roughness, Ra, and the coupled simulated annealing（CSA） and standard simplex（SS） methods are combined for the parameter optimization of the mode. Experiments are conducted to test the performance of the proposed model, and the results show that the range of average relative errors is-4.232%–2.5709%. In comparison with the existing models, the LS-SVM-based model has the best performance in prediction precision, stability, and timesaving.展开更多
Photocatalytic reduction of CO_(2) holds tremendous promise for alleviating the energy crisis.Despite the progress that has been,made,there are still some challenges to overcome,such as the realization under real sunl...Photocatalytic reduction of CO_(2) holds tremendous promise for alleviating the energy crisis.Despite the progress that has been,made,there are still some challenges to overcome,such as the realization under real sunlight rather than the simulation condition.In this work,ultrathin Ni_(2)(OH)(PO_(4))nanotubes(NTs)prepared through hydrothermal route are applied as a novel catalyst for photocatalytic reduction of CO_(2) under real sunlight.The prepared Ni_(2)(OH)(PO_(4))NTs exhibit a 11.3 μmol·h^(-1) CO production rate with,96.1% CO selectivity.Interestingly,Ni_(2)(OH)(PO_(4))NTs have a positive impact on the facilitation of photoreduction in diluted CO_(2).Notably,when the system is performed under real sunlight,Ni_(2)(OH)(PO_(4))NTs afford an accumulated CO of ca.26.8 nmol with,96.9% CO selectivity,exceeding most previous inorganic catalysts under simulated irradiation in the laboratory.Our experimental results demonstrate that the multisynergetic effects induced by surface-OH and the lattice strain serve as highly active sites for CO_(2) molecular adsorption and activation as well as electron transfer,hence enhancing photoreduction activity.Therefore,this work provides experimental basis that CO_(2) photocatalysis can be put into practical use.展开更多
Drastic reduction in biodiversity has been a severe threat to ecosystems,which is exacerbated when losing few species leads to disastrous and even irreparable consequences.Therefore,revealing the mechanism underlying ...Drastic reduction in biodiversity has been a severe threat to ecosystems,which is exacerbated when losing few species leads to disastrous and even irreparable consequences.Therefore,revealing the mechanism underlying biodiversity loss is of uttermost importance.In this study,we show that abundant indirect interactions among mutualistic ecosystems are critical in determining species’status.Combining topological and ecological characteristics,we propose an indicator derived from a dynamic model to identify keystone species and quantify their influence,which outperforms widely-used indicators like degree in realistic and simulated networks.Furthermore,we demonstrate that networks with high modularity,heterogeneity,biodiversity,and less intimate interactions tend to have larger indirect effects,which are more amenable in predicting decline of biodiversity with the proposed indicator.These findings shed some light onto the influence of apposite biodiversities,paving the way from complex network theory to ecosystem protection and restoration.展开更多
Drastic reduction in biodiversity has been a severe threat to ecosystems,which is exacerbated when losing few species leads to disastrous and even irreparable consequences.Therefore,revealing the mechanism underlying ...Drastic reduction in biodiversity has been a severe threat to ecosystems,which is exacerbated when losing few species leads to disastrous and even irreparable consequences.Therefore,revealing the mechanism underlying biodiversity loss is of uttermost importance.In this study,we show that abundant indirect interactions among mutualistic ecosystems are critical in determining species’status.Combining topological and ecological characteristics,we propose an indicator derived from a dynamic model to identify keystone species and quantify their influence,which outperforms widely-used indicators like degree in realistic and simulated networks.Furthermore,we demonstrate that networks with high modularity,heterogeneity,biodiversity,and less intimate interactions tend to have larger indirect effects,which are more amenable in predicting decline of biodiversity with the proposed indicator.These findings shed some light onto the influence of apposite biodiversities,paving the way from complex network theory to ecosystem protection and restoration.展开更多
基金the National Natural Science Foundation of China(No.21836002)the Young Innovative Talents Project in Higher Education of Guangdong(No.2018KQNCX002)+3 种基金Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06N569)the Fundamental Research Funds for the Central Universities(No.D2192000)the Shaoguan Special Fund for Soil Pollution Prevention and Control(No.2017sgtyfz103)the Youth Talent Promotion Project of Guangzhou Science and Technology Association(No.X20200301029)。
文摘The effective extracting Cr(Ⅵ) from chromite ore processing residue(COPR) is the key to achieve COPR detoxification and recovery.We developed an effective method to extract Cr(Ⅵ) from COPR via controlling the phase transformation of Cr(Ⅵ)-containing minerals.Characteristic analysis showed that Cr(Ⅵ) was mainly incorporated in the hydrocalumite(NaCa4Al2O6(SO4/CrO4)1.5-15H2O) in COPR,which was a layered-double hydroxide(LDH) with multilayer structure.In the hydrothermal treatment experiments,the Na2CO3 solution showed significant extraction effect of Cr(Ⅵ) and detoxification effect of COPR.After treatment,95% of Cr(Ⅵ) was removed and the Cr(Ⅵ) concentration in the leachate was decreased to 1.6 mg/L by the toxicity characteristic leaching procedure(TCLP),within the regulatory limit disposal standard(HJ/T 301-2007,3 mg/L).Further study revealed that,during the treatment,hydrocalumite transformed into calcite(CaCO3) under the effect of mineralizer,therefore,the layered structure collapsed and the incorporated Cr(Ⅵ) was released to the supernatant.Meanwhile,the Cr(Ⅵ)desorbed from calcite with the calcite particles grew into large size with smooth surface.Stir-flow experiment revealed that the amount of chromium released from CORP to the environment was significantly reduced after treatment,and it is safer for landfill disposal.This work will provide an instructive guidance for the detoxification and recovery of COPR.
基金supported by the National Natural Science Foundation of China(62172170)the Science and Technology Project of the State Grid Corporation of China(5100-202199557A-0-5-ZN).
文摘Complex networked systems,which range from biological systems in the natural world to infrastructure systems in the human-made world,can exhibit spontaneous recovery after a failure;for example,a brain may spontaneously return to normal after a seizure,and traffic flow can become smooth again after a jam.Previous studies on the spontaneous recovery of dynamical networks have been limited to undirected networks.However,most real-world networks are directed.To fill this gap,we build a model in which nodes may alternately fail and recover,and we develop a theoretical tool to analyze the recovery properties of directed dynamical networks.We find that the tool can accurately predict the final fraction of active nodes,and the prediction accuracy decreases as the fraction of bidirectional links in the network increases,which emphasizes the importance of directionality in network dynamics.Due to different initial states,directed dynamical networks may show alternative stable states under the same control parameter,exhibiting hysteresis behavior.In addition,for networks with finite sizes,the fraction of active nodes may jump back and forth between high and low states,mimicking repetitive failure-recovery processes.These findings could help clarify the system recovery mechanism and enable better design of networked systems with high resilience.
文摘Nowadays,crowded environment and high-speed life pace are likely to bring mental stress and fatigue to citizens.How to apply achievements of the restorative environment into urban planning and environmental design has received more attention in recent years.Earlier research does not provide detailed information about the specific components of the physical environment that support restoration.This study explores which characteristics of the street environment and psychological factors of the street environment have an impact on subjective restoration.The streets were sampled from Shenzhen.Each street was represented by a single photo.The photo was quantified in terms of the different objective street components and also rated on psychological variables related to restoration.The rating on the psychological variables,being away,fascination,coherence,scope,the likelihood of restoration,and preference were provided by people of various ages and occupations.The results show that:1)the proportion of natural elements have the greatest impact on street restoration benefits and preference,and its impact is robust;2)the two characteristics of street safety and quiet are important to street restoration benefits and preferences;3)fascination and being away have a greater impact on restorative benefits of streets,followed by coherence,and the scope of the street has no significant effect on restorative benefits.The study could provide evidence for policy-makers and urban design and planning interventions.
基金supported by the National Key Research and Development Program of China(2022ZD0119601)the National Natural Science Foundation of China(62225306 and U2141235)+3 种基金the Guangdong Basic and Applied Research Foundation(2022B1515120069)the support of the US National Science Foundation(2047488)the Rensselaer–IBM Artificial Intelligence Research Collaborationthe support of China Scholarship Council(202206160043)。
文摘Ecosystems are undergoing unprecedented persistent deterioration due to unsustainable anthropogenic human activities,such as overfishing and deforestation,and the effects of such damage on ecological stability are uncertain.Despite recent advances in experimental and theoretical studies on regime shifts and tipping points,theoretical tools for understanding the extinction chain,which is the sequence of species extinctions resulting from overexploitation,are still lacking,especially for large-scale nonlinear networked systems.In this study,we developed a mathematical tool to predict regime shifts and extinction chains in ecosystems under multiple exploitation situations and verified it in 26 real-world mutualistic networks of various sizes and densities.We discovered five phases during the exploitation process:safe,partial extinction,bistable,tristable,and collapse,which enabled the optimal design of restoration strategies for degraded or collapsed systems.We validated our approach using a 20-year dataset from an eelgrass restoration project.Counterintuitively,we also found a specific region in the diagram spanning exploitation rates and competition intensities,where exploiting more species helps increase biodiversity.Our computational tool provides insights into harvesting,fishing,exploitation,or deforestation plans while conserving or restoring the biodiversity of mutualistic ecosystems.
基金supported by the National Natural Science Foundation of China (62425204, 62122025, U22A2037, 62450002,62432011, 62250028, 81972828, 82172644, and 81830083)Hunan Provincial Natural Science Foundation of China(2021JJ10020)+1 种基金National Key Scientific Infrastructure for Translational Medicine (Shanghai)(TMSK-2021-120)ECNU Multifunctional Platform for Innovation (011)
文摘In target-based drug design,the manual creation of a poor initial compound library,the time-consuming wetlaboratory experimental screening method,and the weak explainability of their activity against compounds significantly limit the efficiency of discovering novel therapeutics.Here we propose an image-guided,interpretability deep learning workflow,named LeadDisFlow,to enable rapid,accurate target drug discovery.Using LeadDisFlow,we identified four potent antagonists with single-nanomolar antagonistic activity against PGE2 receptor subtype 4(EP4),a promising target for tumor im-munotherapy.Remarkably,the most potent EP4 antagonist,ZY001,demonstrated an IC50 value of(0.51±0.02)nM,along with high selectivity.Furthermore,ZY001 effectively impaired the PGE2-induced gene expression of a panel of immunosuppressive molecules in macrophages.The workflow facilitates the discovery of potent EP4 antagonists that enhance anti-tumor immune response,and provides a convenient and quick approach to discover promising therapeutics for a specific drug target.
基金National Natural Science Foundation of China(NSFC)(11774310,61525505,61705193)China Postdoctoral Science Foundation(2017M610367)
文摘The dispersive Fourier transform(DFT) technique opens a fascinating pathway to explore ultrafast non-repetitive events and has been employed to study the build-up process of mode-locked lasers. However, the shutting process for the mode-locked fiber laser seems to be beyond the scope of researchers, and the starting dynamics under nearzero dispersion remains unclear. Here, the complete evolution dynamics(from birth to extinction) of the conventional soliton(CS), stretched pulse(SP), and dissipative soliton(DS) are investigated by using the DFT technique.CS, SP, and DS fiber lasers mode locked by single-walled carbon nanotubes(SWNTs) are implemented via engineering the intracavity dispersion map. The relaxation oscillation can always be observed before the formation of stable pulse operation due to the inherent advantage of SWNT, but it exhibits distinct evolution dynamics in the starting and shutting processes. The shutting processes are dependent on the dispersion condition and turn-off time, which is against common sense. Some critical phenomena are also observed, including transient complex spectrum broadening and frequency-shift interaction of SPs and picosecond pulses. These results will further deepen understanding of the mode-locked fiber laser from a real-time point of view and are helpful for laser design and applications.
基金This work was supported by the National Natural Science Foundation of China(Nos.21777046 and 21836002)the National Key Research and Development Program of China(No.2019YFA0210400)+2 种基金the Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06N569)Guangdong Science and Technology Program(No.2020B121201003)the Science and Technology Project of Guangzhou(No.201803030002).
文摘Converting carbon dioxide(CO_(2))to diverse value-added products through photocatalysis can validly alleviate the critical issues of greenhouse effect and energy shortages simultaneously.In particular,based on practical considerations,exploring novel catalysts to achieve efficient photoreduction of diluted CO_(2) is necessary and urgent.However,this process is extremely challenging owing to the disturbance of competitive adsorption at low CO_(2) concentration.Herein,we delicately synthesize oxygen vacancy-laden NiO nanoplatelets(r-NiO)via calcination under Ar protection to reduce diluted CO_(2) through visible light irradiation(>400 nm)assisted by a Ru-based photosensitizer.Benefitting from the strongly CO_(2) adsorption energy of oxygen vacancies,which was confirmed by density functional calculations,the r-NiO catalysts exhibit higher activity and selectivity(6.28×10^(3)µmol·h^(−1)·g^(−1);82.11%)for diluted CO_(2)-to-CO conversion than that of the normal NiO(3.94×10^(3)µmol·h^(−1)·g^(−1);65.26%).Besides,the presence of oxygen vacancies can also promote the separation of electron-hole pairs.Our research demonstrates that oxygen vacancies could act as promising candidates for photocatalytic CO_(2) reduction,offering fundamental guidance for the actual photoreduction of diluted CO_(2) in the future.
基金We thank X.Yao,X.Han,G.Chen,W.Li,G.Wang,and Y.Zhang for fruitful discussions.The work was supported by the National Natural Science Foundation of China under Grant Nos.61525505,11774310, 61705193by the Key Scientific and Technological Innovation Team Project in Shaanxi Province(2015KCT-06)and by China Postdoctoral Science Foundation(2017M610367).
文摘Real-time spectroscopy based on an emerging time-stretch technique can map the spectral information of optical waves into the time domain,opening several fascinating explorations of nonlinear dynamics in mode-locked lasers.However,the self-starting process of mode-locked lasers is quite sensitive to environmental perturbation,which causes the transient behaviors of lasers to deviate from the true buildup process of solitons.We optimize the laser system to improve its stability,which suppresses the Q-switched lasing induced by environmental perturbation.We,therefore,demonstrate the first observation of the entire buildup process of solitons in a mode-locked laser,revealing two possible pathways to generate the temporal solitons.One pathway includes the dynamics of raised relaxation oscillation,quasimode-locking stage,spectral beating behavior,and finally the stable single-soliton mode-locking.The other pathway contains,however,an extra transient bound-state stage before the final single-pulse modelocking operation.Moreover,we propose a theoretical model to predict the buildup time of solitons,which agrees well with the experimental results.Our findings can bring real-time insights into ultrafast fiber laser design and optimization,as well as promote the application of fiber laser.
基金National Natural Science Foundation of China(NSFC)(61525505,11774310)Natural Science Foundation of Shaanxi Province(2015KCT-06)
文摘We investigate the properties of spatial solitons in the fractional Schr?dinger equation(FSE) with parity-time(PT)-symmetric lattice potential supported by the focusing of Kerr nonlinearity. Both one-and two-dimensional solitons can stably propagate in PT-symmetric lattices under noise perturbations. The domains of stability for both one-and two-dimensional solitons strongly depend on the gain/loss strength of the lattice. In the spatial domain, the solitons are rigidly modulated by the lattice potential for the weak diffraction in FSE systems. In the inverse space, due to the periodicity of lattices, the spectra of solitons experience sharp peaks when the values of wavenumbers are even. The transverse power flows induced by the imaginary part of the lattice are also investigated, which can preserve the internal energy balances within the solitons.
基金National Natural Science Foundation of China(NSFC)(61525505,11774310,61805212)China Postdoctoral Science Foundation(2017M621918)Key Scientific and Technological Innovation Team Project in Shaanxi Province(2015KCT-06)
文摘The ultrafast fiber laser has attracted a great deal of research interest due to its low cost, high efficiency, and simple maintenance. Optical passive devices are vital parts of a fiber laser. In order to obtain a fiber laser with high quality, optical passive devices with high performance are required. Here, we demonstrate a highly integrated optical device with the combination of a saturable absorber(SA), coupler, isolator, wavelength division multiplexer, and erbium-doped fiber. The built-in SA has a modulation depth of 7% and can withstand high pump power due to the unique structure of the proposed device. The proposed device is applied to an ultracompact fiber laser, which greatly simplifies the laser structure and reduces the size of the proposed laser. The central wavelength, pulse duration, repetition rate, and signal-to-noise ratio of the output soliton are 1560 nm, 1.06 ps,25.8 MHz, and 50 dB, respectively. The proposed device has great potential for application in high-power and high-frequency fiber lasers. The proposed ultracompact fiber laser has important applications in optical communication, optical sensing, optical frequency combs, and micromachining.
文摘Reflective fiber optic sensors have advantages for surface roughness measurements of some special workpieces,but their measuring precision and efficiency need to be improved further. A least-squares support vector machine（LS-SVM）-based surface roughness prediction model is proposed to estimate the surface roughness, Ra, and the coupled simulated annealing（CSA） and standard simplex（SS） methods are combined for the parameter optimization of the mode. Experiments are conducted to test the performance of the proposed model, and the results show that the range of average relative errors is-4.232%–2.5709%. In comparison with the existing models, the LS-SVM-based model has the best performance in prediction precision, stability, and timesaving.
基金supported by the National Natural Science Foundation of China(Nos.21777046 and 21836002)the National Key Research and Development Program of China(No.2019YFA0210400)+2 种基金the Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06N569)the Guangdong Science and Technology Program(No.2020B121201003)the Science Technology Project of Guangzhou(No.201803030002).
文摘Photocatalytic reduction of CO_(2) holds tremendous promise for alleviating the energy crisis.Despite the progress that has been,made,there are still some challenges to overcome,such as the realization under real sunlight rather than the simulation condition.In this work,ultrathin Ni_(2)(OH)(PO_(4))nanotubes(NTs)prepared through hydrothermal route are applied as a novel catalyst for photocatalytic reduction of CO_(2) under real sunlight.The prepared Ni_(2)(OH)(PO_(4))NTs exhibit a 11.3 μmol·h^(-1) CO production rate with,96.1% CO selectivity.Interestingly,Ni_(2)(OH)(PO_(4))NTs have a positive impact on the facilitation of photoreduction in diluted CO_(2).Notably,when the system is performed under real sunlight,Ni_(2)(OH)(PO_(4))NTs afford an accumulated CO of ca.26.8 nmol with,96.9% CO selectivity,exceeding most previous inorganic catalysts under simulated irradiation in the laboratory.Our experimental results demonstrate that the multisynergetic effects induced by surface-OH and the lattice strain serve as highly active sites for CO_(2) molecular adsorption and activation as well as electron transfer,hence enhancing photoreduction activity.Therefore,this work provides experimental basis that CO_(2) photocatalysis can be put into practical use.
基金supported in part by the National Natural Science Foundation of China(U2141235 and 61803166)National Natural Science Foundation of Hubei Province(2019CFA005)。
文摘Drastic reduction in biodiversity has been a severe threat to ecosystems,which is exacerbated when losing few species leads to disastrous and even irreparable consequences.Therefore,revealing the mechanism underlying biodiversity loss is of uttermost importance.In this study,we show that abundant indirect interactions among mutualistic ecosystems are critical in determining species’status.Combining topological and ecological characteristics,we propose an indicator derived from a dynamic model to identify keystone species and quantify their influence,which outperforms widely-used indicators like degree in realistic and simulated networks.Furthermore,we demonstrate that networks with high modularity,heterogeneity,biodiversity,and less intimate interactions tend to have larger indirect effects,which are more amenable in predicting decline of biodiversity with the proposed indicator.These findings shed some light onto the influence of apposite biodiversities,paving the way from complex network theory to ecosystem protection and restoration.
基金supported in part by the National Natural Science Foundation of China(U2141235 and 61803166)National Natural Science Foundation of Hubei Province(2019CFA005).
文摘Drastic reduction in biodiversity has been a severe threat to ecosystems,which is exacerbated when losing few species leads to disastrous and even irreparable consequences.Therefore,revealing the mechanism underlying biodiversity loss is of uttermost importance.In this study,we show that abundant indirect interactions among mutualistic ecosystems are critical in determining species’status.Combining topological and ecological characteristics,we propose an indicator derived from a dynamic model to identify keystone species and quantify their influence,which outperforms widely-used indicators like degree in realistic and simulated networks.Furthermore,we demonstrate that networks with high modularity,heterogeneity,biodiversity,and less intimate interactions tend to have larger indirect effects,which are more amenable in predicting decline of biodiversity with the proposed indicator.These findings shed some light onto the influence of apposite biodiversities,paving the way from complex network theory to ecosystem protection and restoration.
