A set of discoveries are described that complete the structural model and diffraction theory for quasicrystals. The irrational diffraction indices critically oppose Bragg diffraction. We analyze them as partly rationa...A set of discoveries are described that complete the structural model and diffraction theory for quasicrystals. The irrational diffraction indices critically oppose Bragg diffraction. We analyze them as partly rational;while the irrational part determines the metric that is necessary for measurement. The measurement is verified by consistency with the measured lattice parameter, now corrected with the metric and index. There is translational symmetry and it is hierarchic, as is demonstrated by phase-contrast, optimum-defocus imaging. In Bragg’s law, orders are integral, periodic and harmonic;we demonstrate harmonic quasi-Bloch waves despite the diffraction in irrational, geometric series. The harmonicity is both local and long range. A breakthrough in understanding came from a modified structure factor that features independence from scattering angle. Diffraction is found to occur at a given “quasi-Bragg condition” that depends on the special metric. This is now analyzed and measured and verified: the metric function is derived from the irrational part of the index in three dimensions. The inverse of the function is exactly equal to the metric that was first discovered independently by means of “quasi-structure factors”. These are consistent with all structural measurements, including diffraction by the quasicrystal, and with the measured lattice parameter.展开更多
Direct numerical simulation(DNS) of gas–solid flow at high resolution has been carried out by coupling the lattice Boltzmann method(LBM) for gas flow and the discrete element method(DEM) for solid particles. However,...Direct numerical simulation(DNS) of gas–solid flow at high resolution has been carried out by coupling the lattice Boltzmann method(LBM) for gas flow and the discrete element method(DEM) for solid particles. However,the body force periodic boundary condition(FPBC) commonly used to cut down the huge computational cost of such simulation has faced accuracy concerns. In this study, a novel two-region periodic boundary condition(TPBC) is presented to remedy this problem, with the flow driven in the region with body force and freely evolving in the other region. With simulation cases for simple circulating fluidized bed risers, the validity and advantages of TPBC are demonstrated with more reasonable heterogeneity of the particle distribution as compared to the corresponding case with FPBC.展开更多
Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these...Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these materials.Periodic patterns of covalent functionalization can lead to pericxJic potentials in the monolayer;however,creating such superstructures is very challenging.Here,we describe an original approach to the periodic functionalization of graphene induced by substrate patterning using a pulsed laser.Laser-induced periodic surface structures(LIPSS)are produced on silicon wafers with thermally-grown oxide layers.The irradiation conditions for the formation of UPSS confined at the Si02/Si interface have been unravelled.LIPSS imprint their periodicity to the reactivity of the monolayer graphene placed on the substrate via modulation of its local doping level.This method is clean,straightforward and scalable with high spatial resolution.展开更多
As a classical technique for chaos suppression,the time-delayed feedback controlling strategy has been widely developed by stabilizing unstable periodic orbits(UPOs)embedded in chaotic systems.A critical issue for ach...As a classical technique for chaos suppression,the time-delayed feedback controlling strategy has been widely developed by stabilizing unstable periodic orbits(UPOs)embedded in chaotic systems.A critical issue for achieving high controlling precision is to search for an appropriate time delay.This paper proposes a simple yet effective approach,based on incremental harmonic balance method,to determine the optimal time delay in the delayed feedback controller.The time delay is adjusted within the iterative scheme provided by the proposed method,and finally converges to the period of the target UPO.As long as the optimal time delay is fixed,moreover,the attained solution makes it quite convenient to analyze its stability according to the Floquet theory,which further provides the effective interval of the feedback gain.展开更多
In this paper,we make use of stochastic theta method to study the existence of the numerical approximation of random periodic solution.We prove that the error between the exact random periodic solution and the approxi...In this paper,we make use of stochastic theta method to study the existence of the numerical approximation of random periodic solution.We prove that the error between the exact random periodic solution and the approximated one is at the 1/4 order time step in mean sense when the initial time tends to∞.展开更多
The one-dimensional nonlinear dynamical wave interactions in a system of quasineutral two-fluid plasma in a constant magnetic field are investigated.The existence of the travelling wave solutions is discussed.The modu...The one-dimensional nonlinear dynamical wave interactions in a system of quasineutral two-fluid plasma in a constant magnetic field are investigated.The existence of the travelling wave solutions is discussed.The modulation stability of linear waves and the modulation instability of weakly nonlinear waves are presented.Both suggest that the Korteweg-de Vries(KdV)system is modulationally stable.Besides,the wave interactions including the periodic wave interaction and the solitary wave interaction are captured and presented.It is shown that these interacting waves alternately exchange their energy during propagation.The Fourier spectrum analysis is used to depict the energy transformation between the primary and harmonic waves.It is known that the wave interactions in magnetized plasma play an important role in various processes of heating and energy transportation in space and astrophysical plasma.However,few researchers have considered such magnetohydrodynamic(MHD)wave interactions in plasma.It is expected that this work can provide additional insight into understanding of behaviors of MHD wave interactions.展开更多
Several studies have reported the detrimental impacts of hypoxia exposure on sleep.Chinese Kunlun Station(altitude 4087 m)is located at Dome A,the highest point on the Antarctic ice sheet and one of the most extreme e...Several studies have reported the detrimental impacts of hypoxia exposure on sleep.Chinese Kunlun Station(altitude 4087 m)is located at Dome A,the highest point on the Antarctic ice sheet and one of the most extreme environments on Earth.This study investigated alteration of sleep,breathing and mood status in healthy expeditioners at Kunlun Station at Dome A.The study examined 10 male volunteers of the inland transverse party to Kunlun Station during the 31st Chinese National Antarctic Research Expedition,and valid data from eight volunteers were analyzed.Sleep structure,breathing pattern and mood were monitored using portable polysomnography(PSG)and profile of mood state(POMS)at two time points:(1)at Zhongshan Station(10 m)before departure to Kunlun Station;(2)on nights 12–13 of residence at Kunlun Station.Slow-wave sleep(Stage 3 non-rapid eye movement)was markedly reduced at Kunlun Station(P<0.01).Total sleep time,sleep efficiency and sleep latency showed no significant changes.Total respiratory events(P<0.05),apnea/hypopnea index(AHI)(P<0.05)and hypopnea index(P<0.01)substantially increased at Kunlun Station.The most common respiratory disorder was periodic breathing,occurring almost exclusively during non-rapid eye movement sleep.The oxygen desaturation index increased markedly(P<0.05),while nocturnal oxygen saturation dramatically fell at Kunlun Station(P<0.05).Vigor scores decreased at Kunlun Station(P<0.05).Expeditioners exhibited reduced slow wave sleep,induced periodic breathing,decreased oxygen saturation and decreased vigor at Kunlun Station.展开更多
The temporal-headway distribution for Totally Asymmetric Simple Exclusion Process(TASEP) with random-sequential update is investigated.Considering the stationary/steady state of the process,exact formula for the step-...The temporal-headway distribution for Totally Asymmetric Simple Exclusion Process(TASEP) with random-sequential update is investigated.Considering the stationary/steady state of the process,exact formula for the step-headway distribution is derived for conditions when the stationary measure is Bernoulli,Le.,for periodic boundaries and for open boundaries with entering boundary rate α and leaving boundary rate 0 satisfying α+β=1.The step-headway formula for general values of boundary rates is calculated numerically by means of the matrix product ansatz.The formula is applicable mainly for the model defined on finite small lattice representing short segment of complex network.In this case the dependency of the motion of individual particles is noticeable and cannot be neglected.The finite lattice results are compared to continuous time distribution obtained by mans of the large L limit It can be observed that the scaled distribution converges quite fast to continuous time distribution.However,in the case of rather small lattice the distribution significantly differs from the limiting one.Moreover,in the case of Bernoulli stationary measure,the distribution is not dependent on the position of the reference site on the lattice.Considering general values of boundary parameters,the shape of the distribution is influenced by the density profile of the process near boundaries.This influence vanishes with increasing lattice size.展开更多
The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from ...The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from GPS observations at stations of Shenzhen and Guangzhou from 2011 to 2012.This study reported that the ratio of simultaneous occurrences of TEC depletions with strong scintillations was higher than that of TEC depletions with weak scintillations in vernal and autumnal equinoxes of 2011 over South China.The number of the periodic structures of TEC with depletion contained was greater than that with no depletion contained corresponding to strong scintillations.The structure of the slab of plasma irregularities could be responsible for the simultaneous occurrences of TEC depletion with strong scintillations and ROTI.Before and during the occurrences of strong scintillation,there was Large-Scale Wave Structure(LSWS) which provided the seed ionization perturbation to trigger ESF irregularities and contributed to the periodic structure of TEC.展开更多
To the editor,A new type of solid, called quasicrystal (QC) was discovered after Shechtman et al.[1] accidently got in 1982 a five-fold symmetry diffraction image of rapidly cooled Al-Mn alloys.In contrast with crysta...To the editor,A new type of solid, called quasicrystal (QC) was discovered after Shechtman et al.[1] accidently got in 1982 a five-fold symmetry diffraction image of rapidly cooled Al-Mn alloys.In contrast with crystals with periodic atomic arrangement,QCs have perfect long-range order (like mirror symmetry)but no periodic translational symmetry. Due to their intrinsic brittleness at room temperature, QCs cannot be used directly as structural materials. However, QCs as thin films and coatings of metals in industry are applied to surface modified materials and the reinforcing phase in structural materials.展开更多
In this paper,we study a deterministic model with non-autonomous system for mixed cultivars to assess the effect of cultivar susceptibility and seasonal variation on banana Xanthomonas wilt(BXW)disease dynamics.A spec...In this paper,we study a deterministic model with non-autonomous system for mixed cultivars to assess the effect of cultivar susceptibility and seasonal variation on banana Xanthomonas wilt(BXW)disease dynamics.A special case of two cultivars classified as highly susceptible for inflorescence infection(ABB)and less susceptible(AAA)cultivar is considered.The basic reproduction number corresponding to the non-autonomous system is derived and numerically computed to determine disease dynamics.Results showed that the disease dies out whenever the periodic basic reproduction number is less than unity and a periodic solution is obtained when it is greater than one.Results further showed that for both cultivars,the basic reproduction number increases with increasing values of the transmission rates and declines exponentially with increasing values of roguing rates.The critical roguing rate of ABB-genome cultivar was higher than that of AAA-genome cultivars.The peaks in disease prevalence indicate the importance of effective implementation of controls during the rainy season.We conclude that highly susceptible cultivars play an important role in the spread of BXW and control measures should be effectively implemented during the rainy season if BXW is to be eradicated.展开更多
In this paper the authors investigate the boundedness and almost periodicity of solutions of semilinear parabolic equations with boundary degeneracy. The equations may be weakly degenerate or strongly degenerate on th...In this paper the authors investigate the boundedness and almost periodicity of solutions of semilinear parabolic equations with boundary degeneracy. The equations may be weakly degenerate or strongly degenerate on the lateral boundary. The authors prove the existence, uniqueness and global exponential stability of bounded entire solutions, and also establish the existence theorem of almost periodic solutions if the data are almost periodic.展开更多
In 2003,Railsback proposed the Earth Scientist's Periodic Table,which displays a great deal of elemental geology information in accordance with the natural environment of the earth.As an applied science,metallurgy...In 2003,Railsback proposed the Earth Scientist's Periodic Table,which displays a great deal of elemental geology information in accordance with the natural environment of the earth.As an applied science,metallurgy is based on mineral composition and element behavior,that is similar to geochemistry.In this paper,connections and similarities between geology and metallurgy are identified,based on geochemical laws and numerous metallurgical cases.An obvious connection is that simple cations w让h high and low ionic potential are commonly extracted by hydrometallurgy,while those with intermediate ionic potential are extracted by pyrometallurgy.In addition,element affinity in geology is associated with element migration in metallurgic phases.To be specific,in pyrometallurgy,lithophile elements tend to gather in slags,chalcophile elements prefer the matte phase,siderophile elements are easily absorbed into metal melt,and atmophile elements readily enter the gas phase.Furthermore,in hydrometallurgy,the principles of hard/soft acids and bases(HSABs)offer an explanation of how precipitation and dissolution occur in different solutions,especially for fluoride and chloride.This article provides many metallurgical examples based on the principles of geochemistry to verify these similarities and conn ections.展开更多
The formation of controllable size and dripping frequency in electrohydrodynamic(EHD)atomization with electric periodic dripping regime are of much interest and importance because of significant and wide applications,...The formation of controllable size and dripping frequency in electrohydrodynamic(EHD)atomization with electric periodic dripping regime are of much interest and importance because of significant and wide applications,such as micro-encapsulation and ink-printing.In the present study,the experimental and theoretical works were carried out to explore droplet formation in periodic dripping regime in presence of an electric field.The dimensionless electric charge carried by each droplet produced is smaller than the 50%of critical value of the Rayleigh limit,where charge-to-mass ratio of droplets was obtained through the deflection distance in the presence of an electric field.The droplet in electric periodic dripping regime usually undergoes oscillating deformation,and finally forms a spherical droplet below the tip no more than ten times out diameter of tube.The droplet size tens of microns to one hundreds of microns decreases with an increase in applied potential.In the electric dripping mode,droplets size is independent of flow rate and affected by flow rate due to adsorption of surface active species in micro-dripping.The simplified model to predict droplets size was derived from the balance of electric,surface tension and gravity forces.The droplets size calculated in good agreement with the experiments.Meanwhile,the dripping frequency of droplets with rang of a few to several hundred hertz obtained from timeresolved images is highly dependent of liquid flow rate and electric potential.The largest dripping frequency was predicted and in reasonable agreement with the experimental results.In electric periodic dripping regime drop-on-demand droplets in size and dripping frequency further our understanding on the formation of identical droplets and are beneficial to many practical applications.展开更多
Vibrations of a beam can be described as an Euler-Bernoulli beam,or as a Rayleigh beam or as a Timoshenko beam.In this paper,we establish the existence of periodic solutions in time for a damped Rayleigh beam model wi...Vibrations of a beam can be described as an Euler-Bernoulli beam,or as a Rayleigh beam or as a Timoshenko beam.In this paper,we establish the existence of periodic solutions in time for a damped Rayleigh beam model with time delay,which is treated as a bifurcation parameter.The main proof is based on a Lyapunov-Schmidt reduction together with the classical implicit function theorem.Moreover,we give a sufficient condition for a direction of bifurcation.展开更多
We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid(chloroform,CHCl3)with~2 ps laser pulses at an input energy of~350μJ.The synthesized aluminum nanoparticles exhibited a su...We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid(chloroform,CHCl3)with~2 ps laser pulses at an input energy of~350μJ.The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at~340 nm.Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of(27±3.6)nm.The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles.In addition to spherical aluminum nanoparticles,triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution.Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures(LIPSSs),which were the high spatial frequency LIPSSs(HSF-LIPSSs)since their grating period was~280 nm.Additionally,coarse structures with a period of~700 nm were observed.展开更多
文摘A set of discoveries are described that complete the structural model and diffraction theory for quasicrystals. The irrational diffraction indices critically oppose Bragg diffraction. We analyze them as partly rational;while the irrational part determines the metric that is necessary for measurement. The measurement is verified by consistency with the measured lattice parameter, now corrected with the metric and index. There is translational symmetry and it is hierarchic, as is demonstrated by phase-contrast, optimum-defocus imaging. In Bragg’s law, orders are integral, periodic and harmonic;we demonstrate harmonic quasi-Bloch waves despite the diffraction in irrational, geometric series. The harmonicity is both local and long range. A breakthrough in understanding came from a modified structure factor that features independence from scattering angle. Diffraction is found to occur at a given “quasi-Bragg condition” that depends on the special metric. This is now analyzed and measured and verified: the metric function is derived from the irrational part of the index in three dimensions. The inverse of the function is exactly equal to the metric that was first discovered independently by means of “quasi-structure factors”. These are consistent with all structural measurements, including diffraction by the quasicrystal, and with the measured lattice parameter.
基金Supported by the National Natural Science Foundation of China(21821005,91834303)Science Challenge Project(TZ2016001)+1 种基金the Key Research Program of Frontier Science of the Chinese Academy of Sciences(QYZDJ-SSW-JSC029)the Strategic Priority Research Program of the CAS(XDA21030700).
文摘Direct numerical simulation(DNS) of gas–solid flow at high resolution has been carried out by coupling the lattice Boltzmann method(LBM) for gas flow and the discrete element method(DEM) for solid particles. However,the body force periodic boundary condition(FPBC) commonly used to cut down the huge computational cost of such simulation has faced accuracy concerns. In this study, a novel two-region periodic boundary condition(TPBC) is presented to remedy this problem, with the flow driven in the region with body force and freely evolving in the other region. With simulation cases for simple circulating fluidized bed risers, the validity and advantages of TPBC are demonstrated with more reasonable heterogeneity of the particle distribution as compared to the corresponding case with FPBC.
基金The work was supported by project No.18-09055Y and 20-08633X awarded by Czech Science FoundationThe research of I.M.,J.S.,T.J.-Y.D.,and N.M.B.is financed by the European Regional Development Fund and the state budget of the Czech Republic(project BIATRI,No.CZ.02.1.01/0.0/0.0/15_003/0000445,project HiLASE CoE,No.CZ.02.1.01/0.0/0.0/15_006/0000674,programme NPU I,project No.LO1602)+3 种基金The work was further supported by European Regional Development Fund,OP RDE,Project:“Carbon allotropes with rationalized nanointerfaces and nanolinks for environmental and biomedical applications”(No.CZ.02.1.01/0.0/0.0/16_026/0008382)The authors also acknowledge the assistance provided by the Research Infrastructures NanoEnviCz(No.LM2015073)supported by the Ministry of EducationYouth and Sports of the Czech Republic and the project Pro-NanoEnviCz(No.CZ.02.1.01/0.0/0.0/16_013/0001821)supported by the Ministry of EducationYouth and Sports of the Czech Republic and the European Union-European Structural and Investments Funds in the frame of Operational Programme Research Development and Education.
文摘Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these materials.Periodic patterns of covalent functionalization can lead to pericxJic potentials in the monolayer;however,creating such superstructures is very challenging.Here,we describe an original approach to the periodic functionalization of graphene induced by substrate patterning using a pulsed laser.Laser-induced periodic surface structures(LIPSS)are produced on silicon wafers with thermally-grown oxide layers.The irradiation conditions for the formation of UPSS confined at the Si02/Si interface have been unravelled.LIPSS imprint their periodicity to the reactivity of the monolayer graphene placed on the substrate via modulation of its local doping level.This method is clean,straightforward and scalable with high spatial resolution.
基金supported by the National Natural Science Foundation of China(Grants 11702333 and 11672337)Natural Science Foundation of Guangdong Province(Grant 2018B030311001).
文摘As a classical technique for chaos suppression,the time-delayed feedback controlling strategy has been widely developed by stabilizing unstable periodic orbits(UPOs)embedded in chaotic systems.A critical issue for achieving high controlling precision is to search for an appropriate time delay.This paper proposes a simple yet effective approach,based on incremental harmonic balance method,to determine the optimal time delay in the delayed feedback controller.The time delay is adjusted within the iterative scheme provided by the proposed method,and finally converges to the period of the target UPO.As long as the optimal time delay is fixed,moreover,the attained solution makes it quite convenient to analyze its stability according to the Floquet theory,which further provides the effective interval of the feedback gain.
基金supported by the National Natural Science Foundation of China (No.11871184,11701127)by the Natural Science Foundation of Hainan Province(Grant No.117096)
文摘In this paper,we make use of stochastic theta method to study the existence of the numerical approximation of random periodic solution.We prove that the error between the exact random periodic solution and the approximated one is at the 1/4 order time step in mean sense when the initial time tends to∞.
基金supported by the National Natural Science Foundation of China(No.11872241)。
文摘The one-dimensional nonlinear dynamical wave interactions in a system of quasineutral two-fluid plasma in a constant magnetic field are investigated.The existence of the travelling wave solutions is discussed.The modulation stability of linear waves and the modulation instability of weakly nonlinear waves are presented.Both suggest that the Korteweg-de Vries(KdV)system is modulationally stable.Besides,the wave interactions including the periodic wave interaction and the solitary wave interaction are captured and presented.It is shown that these interacting waves alternately exchange their energy during propagation.The Fourier spectrum analysis is used to depict the energy transformation between the primary and harmonic waves.It is known that the wave interactions in magnetized plasma play an important role in various processes of heating and energy transportation in space and astrophysical plasma.However,few researchers have considered such magnetohydrodynamic(MHD)wave interactions in plasma.It is expected that this work can provide additional insight into understanding of behaviors of MHD wave interactions.
基金the Chinese Arctic and Antarctic Administrationthe Polar Research Institute of China,Ministry of Natural Resources(MNR)for their full support+1 种基金supported by the Chinese Academy of Medical Science Innovation Fund for Medical Sciences(Grant no.,2017-I2M-1-009)the fund of Chinese Polar Environment Comprehensive Investigation&Assessment Programmes(Grant no.,CHINARE 02-01)。
文摘Several studies have reported the detrimental impacts of hypoxia exposure on sleep.Chinese Kunlun Station(altitude 4087 m)is located at Dome A,the highest point on the Antarctic ice sheet and one of the most extreme environments on Earth.This study investigated alteration of sleep,breathing and mood status in healthy expeditioners at Kunlun Station at Dome A.The study examined 10 male volunteers of the inland transverse party to Kunlun Station during the 31st Chinese National Antarctic Research Expedition,and valid data from eight volunteers were analyzed.Sleep structure,breathing pattern and mood were monitored using portable polysomnography(PSG)and profile of mood state(POMS)at two time points:(1)at Zhongshan Station(10 m)before departure to Kunlun Station;(2)on nights 12–13 of residence at Kunlun Station.Slow-wave sleep(Stage 3 non-rapid eye movement)was markedly reduced at Kunlun Station(P<0.01).Total sleep time,sleep efficiency and sleep latency showed no significant changes.Total respiratory events(P<0.05),apnea/hypopnea index(AHI)(P<0.05)and hypopnea index(P<0.01)substantially increased at Kunlun Station.The most common respiratory disorder was periodic breathing,occurring almost exclusively during non-rapid eye movement sleep.The oxygen desaturation index increased markedly(P<0.05),while nocturnal oxygen saturation dramatically fell at Kunlun Station(P<0.05).Vigor scores decreased at Kunlun Station(P<0.05).Expeditioners exhibited reduced slow wave sleep,induced periodic breathing,decreased oxygen saturation and decreased vigor at Kunlun Station.
文摘The temporal-headway distribution for Totally Asymmetric Simple Exclusion Process(TASEP) with random-sequential update is investigated.Considering the stationary/steady state of the process,exact formula for the step-headway distribution is derived for conditions when the stationary measure is Bernoulli,Le.,for periodic boundaries and for open boundaries with entering boundary rate α and leaving boundary rate 0 satisfying α+β=1.The step-headway formula for general values of boundary rates is calculated numerically by means of the matrix product ansatz.The formula is applicable mainly for the model defined on finite small lattice representing short segment of complex network.In this case the dependency of the motion of individual particles is noticeable and cannot be neglected.The finite lattice results are compared to continuous time distribution obtained by mans of the large L limit It can be observed that the scaled distribution converges quite fast to continuous time distribution.However,in the case of rather small lattice the distribution significantly differs from the limiting one.Moreover,in the case of Bernoulli stationary measure,the distribution is not dependent on the position of the reference site on the lattice.Considering general values of boundary parameters,the shape of the distribution is influenced by the density profile of the process near boundaries.This influence vanishes with increasing lattice size.
基金Supported by the National Natural Science Young Foundation of China(41704168)。
文摘The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from GPS observations at stations of Shenzhen and Guangzhou from 2011 to 2012.This study reported that the ratio of simultaneous occurrences of TEC depletions with strong scintillations was higher than that of TEC depletions with weak scintillations in vernal and autumnal equinoxes of 2011 over South China.The number of the periodic structures of TEC with depletion contained was greater than that with no depletion contained corresponding to strong scintillations.The structure of the slab of plasma irregularities could be responsible for the simultaneous occurrences of TEC depletion with strong scintillations and ROTI.Before and during the occurrences of strong scintillation,there was Large-Scale Wave Structure(LSWS) which provided the seed ionization perturbation to trigger ESF irregularities and contributed to the periodic structure of TEC.
基金supported by the National Natural Science Foundation of hina (Grant Nos. 11862021, and 11502123)the Program for Young Taents of Science and Technology in Universities of Inner Mongolia Autonmous Region (Grant No. NJYT-19-A06)
文摘To the editor,A new type of solid, called quasicrystal (QC) was discovered after Shechtman et al.[1] accidently got in 1982 a five-fold symmetry diffraction image of rapidly cooled Al-Mn alloys.In contrast with crystals with periodic atomic arrangement,QCs have perfect long-range order (like mirror symmetry)but no periodic translational symmetry. Due to their intrinsic brittleness at room temperature, QCs cannot be used directly as structural materials. However, QCs as thin films and coatings of metals in industry are applied to surface modified materials and the reinforcing phase in structural materials.
基金Mcknight Foundation Grant No.12-508 with additional support from the Roots,Tubers and Banana(RTB)program and Bioversity International.
文摘In this paper,we study a deterministic model with non-autonomous system for mixed cultivars to assess the effect of cultivar susceptibility and seasonal variation on banana Xanthomonas wilt(BXW)disease dynamics.A special case of two cultivars classified as highly susceptible for inflorescence infection(ABB)and less susceptible(AAA)cultivar is considered.The basic reproduction number corresponding to the non-autonomous system is derived and numerically computed to determine disease dynamics.Results showed that the disease dies out whenever the periodic basic reproduction number is less than unity and a periodic solution is obtained when it is greater than one.Results further showed that for both cultivars,the basic reproduction number increases with increasing values of the transmission rates and declines exponentially with increasing values of roguing rates.The critical roguing rate of ABB-genome cultivar was higher than that of AAA-genome cultivars.The peaks in disease prevalence indicate the importance of effective implementation of controls during the rainy season.We conclude that highly susceptible cultivars play an important role in the spread of BXW and control measures should be effectively implemented during the rainy season if BXW is to be eradicated.
基金the Guangdong Provincial Natural Science Foundation of China(No.S2013010015800)the KLSCK of the Ministry of Education of China(No.93K172012K03)。
文摘In this paper the authors investigate the boundedness and almost periodicity of solutions of semilinear parabolic equations with boundary degeneracy. The equations may be weakly degenerate or strongly degenerate on the lateral boundary. The authors prove the existence, uniqueness and global exponential stability of bounded entire solutions, and also establish the existence theorem of almost periodic solutions if the data are almost periodic.
基金This work was financially supported by the Key Program of National Natural Science Foundation of China(51334008).
文摘In 2003,Railsback proposed the Earth Scientist's Periodic Table,which displays a great deal of elemental geology information in accordance with the natural environment of the earth.As an applied science,metallurgy is based on mineral composition and element behavior,that is similar to geochemistry.In this paper,connections and similarities between geology and metallurgy are identified,based on geochemical laws and numerous metallurgical cases.An obvious connection is that simple cations w让h high and low ionic potential are commonly extracted by hydrometallurgy,while those with intermediate ionic potential are extracted by pyrometallurgy.In addition,element affinity in geology is associated with element migration in metallurgic phases.To be specific,in pyrometallurgy,lithophile elements tend to gather in slags,chalcophile elements prefer the matte phase,siderophile elements are easily absorbed into metal melt,and atmophile elements readily enter the gas phase.Furthermore,in hydrometallurgy,the principles of hard/soft acids and bases(HSABs)offer an explanation of how precipitation and dissolution occur in different solutions,especially for fluoride and chloride.This article provides many metallurgical examples based on the principles of geochemistry to verify these similarities and conn ections.
基金National Natural Science Foundation of China(51106064)Natural Science Foundation of Jiangsu Province,China(BK20171301)+1 种基金China Postdoctoral Science Foundation(2018M632245)a project supported by Jiangsu University for NSFC(FCJJ2015001)。
文摘The formation of controllable size and dripping frequency in electrohydrodynamic(EHD)atomization with electric periodic dripping regime are of much interest and importance because of significant and wide applications,such as micro-encapsulation and ink-printing.In the present study,the experimental and theoretical works were carried out to explore droplet formation in periodic dripping regime in presence of an electric field.The dimensionless electric charge carried by each droplet produced is smaller than the 50%of critical value of the Rayleigh limit,where charge-to-mass ratio of droplets was obtained through the deflection distance in the presence of an electric field.The droplet in electric periodic dripping regime usually undergoes oscillating deformation,and finally forms a spherical droplet below the tip no more than ten times out diameter of tube.The droplet size tens of microns to one hundreds of microns decreases with an increase in applied potential.In the electric dripping mode,droplets size is independent of flow rate and affected by flow rate due to adsorption of surface active species in micro-dripping.The simplified model to predict droplets size was derived from the balance of electric,surface tension and gravity forces.The droplets size calculated in good agreement with the experiments.Meanwhile,the dripping frequency of droplets with rang of a few to several hundred hertz obtained from timeresolved images is highly dependent of liquid flow rate and electric potential.The largest dripping frequency was predicted and in reasonable agreement with the experimental results.In electric periodic dripping regime drop-on-demand droplets in size and dripping frequency further our understanding on the formation of identical droplets and are beneficial to many practical applications.
基金the National Natural Science Foundation of China(Grant No.11901232)the China Postdoctoral Science Foundation(Grant No.2019M651191)+2 种基金supported in part by the National Basic Research Program of China(Grant No.2013CB834100)JilinDRC(Grant No.2017C028-1)the National Natural Science Foundation of China(Grant Nos.11571065,11171132)。
文摘Vibrations of a beam can be described as an Euler-Bernoulli beam,or as a Rayleigh beam or as a Timoshenko beam.In this paper,we establish the existence of periodic solutions in time for a damped Rayleigh beam model with time delay,which is treated as a bifurcation parameter.The main proof is based on a Lyapunov-Schmidt reduction together with the classical implicit function theorem.Moreover,we give a sufficient condition for a direction of bifurcation.
文摘We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid(chloroform,CHCl3)with~2 ps laser pulses at an input energy of~350μJ.The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at~340 nm.Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of(27±3.6)nm.The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles.In addition to spherical aluminum nanoparticles,triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution.Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures(LIPSSs),which were the high spatial frequency LIPSSs(HSF-LIPSSs)since their grating period was~280 nm.Additionally,coarse structures with a period of~700 nm were observed.