Research of the acoustic local effect of metamaterial is widely used in the fields of environmental science,military industry and biomedicine.In this paper,the metamaterial is designed by annular columnar structures.T...Research of the acoustic local effect of metamaterial is widely used in the fields of environmental science,military industry and biomedicine.In this paper,the metamaterial is designed by annular columnar structures.The acoustic local effect in slender columnar structure with two layers of rings in air is investigated.Results prove that when the plane acoustic wave is incident into the model,complex interference and diffraction occur.And at different frequencies,multipolar acoustic local effect existes and cycle distribution phenomenon is observed.It is noteworthy that this phenomenon has very weak relatedness with the materials and acoustic parameters of the model.The research of this metamaterial design in this paper has definite reference significance in the acoustic communication and amplification of the acoustic signal detection.展开更多
In this paper, traveling wavefront solutions are established for two cooperative systems with time delay and non-local effects. The results are an extension of the existing results for delayed logistic scale equations...In this paper, traveling wavefront solutions are established for two cooperative systems with time delay and non-local effects. The results are an extension of the existing results for delayed logistic scale equations and diffusive Nicholson equations with non-local effects to systems. The approach used is the upper-lower solution technique and Schauder fixed point Theorem developed by Ma（J Differential Equations,2001,171：294-314. ）.展开更多
In this paper,we consider the reaction diffusion equations with strong generic delay kernel and non-local effect,which models the microbial growth in a flow reactor.The existence of traveling waves is established for ...In this paper,we consider the reaction diffusion equations with strong generic delay kernel and non-local effect,which models the microbial growth in a flow reactor.The existence of traveling waves is established for this model.More precisely,using the geometric singular perturbation theory,we show that traveling wave solutions exist provided that the delay is sufficiently small with the strong generic delay kernel.展开更多
By utilizing wave velocity imaging technology,the uniaxial multi-stage loading test was conducted on siltstone to attain wave velocity imagings during rock fracture.Based on the time series parameters of acoustic emis...By utilizing wave velocity imaging technology,the uniaxial multi-stage loading test was conducted on siltstone to attain wave velocity imagings during rock fracture.Based on the time series parameters of acoustic emissions(AE),joint response characteristics of the velocity field and AE during rock fracture were analyzed.Moreover,the localization effect of damage during rock fracture was explored by applying wave velocity imagings.The experimental result showed that the wave velocity imagings enable three-dimensional(3-D)visualization of the extent and spatial position of damage to the rock.A damaged zone has a low wave velocity and a zone where the low wave velocity is concentrated tends to correspond to a severely damaged zone.AE parameters and wave velocity imagings depict the changes in activity of cracks during rock fracture from temporal and spatial perspectives,respectively:the activity of cracks is strengthened,and the rate of AE events increases during rock fracture;correspondingly,the low-velocity zones are gradually aggregated and their area gradually increases.From the wave velocity imagings,the damaged zones in rock were divided into an initially damaged zone,a progressively damaged zone,and a fractured zone.During rock fracture,the progressively damaged zone and the fractured zone both develop around the initially damaged zone,showing a typical localization effect of the damage.By capturing the spatial development trends of the progressively damaged zone and fractured zone in wave velocity imagings,the development of microfractures can be predicted,exerting practical significance for determining the position of the main fracture.展开更多
Zhangjiakou is an important wind power base in Hebei Province,China.The impact of its wind farms on the local climate is controversial.Based on long-term meteorological data from 1981 to 2018,we investigated the effec...Zhangjiakou is an important wind power base in Hebei Province,China.The impact of its wind farms on the local climate is controversial.Based on long-term meteorological data from 1981 to 2018,we investigated the effects of the Shangyi Wind Farm(SWF)in Zhangjiakou on air temperature,wind speed,relative humidity,and precipitation using the anomaly or ratio method between the impacted weather station and the non-impacted background weather station.The influence of the SWF on land surface temperature(LST)and evapotranspiration(ET)using MODIS satellite data from 2003 to 2018 was also explored.The results showed that the SWF had an atmospheric warming effect at night especially in summer and autumn(up to 0.95℃).The daytime air temperature changes were marginal,and their signs were varying depending on the season.The annual mean wind speed decreased by 6%,mainly noted in spring and winter(up to 14%).The precipitation and relative humidity were not affected by the SWF.There was no increase in LST in the SWF perhaps due to the increased vegetation coverage unrelated to the wind farms,which canceled out the wind farm-induced land surface warming and also resulted in an increase in ET.The results showed that the impact of wind farms on the local climate was significant,while their impact on the regional climate was slight.展开更多
Today,with the rapid development of the internet,a large amount of information often accompanies the rapid transmission of disease outbreaks,and increasing numbers of scholars are studying the relationship between inf...Today,with the rapid development of the internet,a large amount of information often accompanies the rapid transmission of disease outbreaks,and increasing numbers of scholars are studying the relationship between information and the disease transmission process using complex networks.In fact,the disease transmission process is very complex.Besides this information,there will often be individual behavioral measures and other factors to consider.Most of the previous research has aimed to establish a two-layer network model to consider the impact of information on the transmission process of disease,rarely divided into information and behavior,respectively.To carry out a more in-depth analysis of the disease transmission process and the intrinsic influencing mechanism,this paper divides information and behavior into two layers and proposes the establishment of a complex network to study the dynamic co-evolution of information diffusion,vaccination behavior,and disease transmission.This is achieved by considering four influential relationships between adjacent layers in multilayer networks.In the information layer,the diffusion process of negative information is described,and the feedback effects of local and global vaccination are considered.In the behavioral layer,an individual's vaccination behavior is described,and the probability of an individual receiving a vaccination is influenced by two factors:the influence of negative information,and the influence of local and global disease severity.In the disease layer,individual susceptibility is considered to be influenced by vaccination behavior.The state transition equations are derived using the micro Markov chain approach(MMCA),and disease prevalence thresholds are obtained.It is demonstrated through simulation experiments that the negative information diffusion is less influenced by local vaccination behavior,and is mainly influenced by global vaccination behavior;vaccination behavior is mainly influenced by local disease conditions,and is less influenced by global disease conditions;the disease transmission threshold increases with the increasing vaccination rate;and the scale of disease transmission increases with the increasing negative information diffusion rate and decreases with the increasing vaccination rate.Finally,it is found that when individual vaccination behavior considers both the influence of negative information and disease,it can increase the disease transmission threshold and reduce the scale of disease transmission.Therefore,we should resist the diffusion of negative information,increase vaccination proportions,and take appropriate protective measures in time.展开更多
A non-local solution for a functionally graded piezoelectric nano-rod is pre- sented by accounting the surface effect. This solution is used to evaluate the charac- teristics of the wave propagation in the rod structu...A non-local solution for a functionally graded piezoelectric nano-rod is pre- sented by accounting the surface effect. This solution is used to evaluate the charac- teristics of the wave propagation in the rod structure. The model is loaded under a two-dimensional （2D） electric potential and an initially applied voltage at the top of the rod. The mechanical and electrical properties are assumed to be variable along the thick- ness direction of the rod according to the power law. The Hamilton principle is used to derive the governing differential equations of the electromechanical system. The effects of some important parameters such as the applied voltage and gradation of the material properties on the wave characteristics of the rod are studied.展开更多
Four blue-violet light emitting InGaN/GaN multiple quantum well（MQW） structures with different well widths are grown by metal–organic chemical vapor deposition. The carrier localization effect in these samples is i...Four blue-violet light emitting InGaN/GaN multiple quantum well（MQW） structures with different well widths are grown by metal–organic chemical vapor deposition. The carrier localization effect in these samples is investigated mainly by temperature-dependent photoluminescence measurements. It is found that the localization effect is enhanced as the well width increases from 1.8 nm to 3.6 nm in our experiments. The temperature induced PL peak blueshift and linewidth variation increase with increasing well width, implying that a greater amplitude of potential fluctuation as well as more localization states exist in wider wells. In addition, it is noted that the broadening of the PL spectra always occurs mainly on the low-energy side of the PL spectra due to the temperature-induced band-gap shrinkage, while in the case of the widest well, a large extension of the spectral curve also occurs in the high energy sides due to the existence of more shallow localized centers.展开更多
Local thermal effect influencing the fluorescence of triply ionized rare earth ions doped in nanocrystals is studied with laser spectroscopy and theory of thermal transportation for transparent oxyfluoride glass ceram...Local thermal effect influencing the fluorescence of triply ionized rare earth ions doped in nanocrystals is studied with laser spectroscopy and theory of thermal transportation for transparent oxyfluoride glass ceramics containing nanocrystals. The result shows that the local temperature of the nanocrystals embedded in glass matrices is much higher than the environmental temperature of the sample. It is suggested that the tempera,ture-dependent thermal energy induced by the light absorption must be considered when the theory of thermal transportation is applied to the study of local thermal effect.展开更多
Recent studies have shown that the size of microvoids has a significant effect on the void growth rate.The purpose of this paper is to explore whether the void size effect can influence the plastic flow localization i...Recent studies have shown that the size of microvoids has a significant effect on the void growth rate.The purpose of this paper is to explore whether the void size effect can influence the plastic flow localization in ductile materials.We have used the extended Gurson's dilatational plasticity theory,which accounts for the void size effect,to study the plastic flow localization in porous solids with long cylindrical voids.The localization model of Rice is adopted,in which the material inside the band may display a different response from that outside the band at the incipient plastic flow localization.The present study shows that it has little effect on the shear band angle.展开更多
Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibratio...Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.展开更多
The localized effect of light diffracted by a capillary wave is discovered by changing the wave amplitude. The localized range is related to the wave number and the amplitude. The dependence of the half maximum locali...The localized effect of light diffracted by a capillary wave is discovered by changing the wave amplitude. The localized range is related to the wave number and the amplitude. The dependence of the half maximum localized angle on the wave number and amplitude is analytically derived. Meanwhile, the analytic angular distribution of the diffraction light in the localized range is obtained. Experiments are carried out to achieve diffraction patterns to confirm the localized effect and to measure the angular distribution of the diffraction light intensity as well as to determine the localized range scales corresponding to different wave amplitudes. Theoretical curves of the light intensity angular distribution and localized interval widths related to surface acoustic wave amplitudes are compared with the experimental data. The experimental results agree well with the theoretical prediction.展开更多
An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are relate...An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are related to the CoFeB thickness.When the film is thicker than 3 nm,the side jump mechanism dominates and the weak locaUzation to AHC vanishes.For very thin CoFeB films,both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect,and the weak localization correction to AHC is observed.展开更多
The precedence effect is a prerequisite for faithful sound localization in a complex auditory environment, and is a physiological phenomenon in which the auditory system selectively suppresses the directional informat...The precedence effect is a prerequisite for faithful sound localization in a complex auditory environment, and is a physiological phenomenon in which the auditory system selectively suppresses the directional information from echoes. Here we investigated how neurons in the inferior colliculus respond to the paired sounds that produce precedence-effect illusions, and whether their firing behavior can be modulated through inhibition with gamma-aminobutyric acid （GABA）. We recorded extracellularly from 36 neurons in rat inferior colliculus under three conditions： no injection, injection with saline, and injection with gamma-aminobutyric acid. The paired sounds that produced precedence effects were two identical 4-ms noise bursts, which were delivered contralaterally or ipsilaterally to the recording site. The normalized neural responses were measured as a function of different inter-stimulus delays and half-maximal interstimulus delays were acquired. Neuronal responses to the lagging sounds were weak when the inter-stimulus delay was short, but increased gradually as the delay was lengthened. Saline injection produced no changes in neural responses, but after local gamma-arninobutyric acid application, responses to the lagging stimulus were suppressed. Application of gamma-aminobutyric acid affected the normalized response to lagging sounds, independently of whether they or the paired sounds were contralateral or ipsilateral to the recording site. These observations suggest that local inhibition by gamma-aminobutyric acid in the rat inferior colliculus shapes the neural responses to lagging sounds, and modulates the precedence effect.展开更多
In this paper,a unified diagnostic method for the nonlinear models with random effects based upon the joint likelihood given by Robinson in 1991 is presented.It is shown that the case deletion model is equivalent to t...In this paper,a unified diagnostic method for the nonlinear models with random effects based upon the joint likelihood given by Robinson in 1991 is presented.It is shown that the case deletion model is equivalent to the mean shift outlier model.From this point of view,several diagnostic measures,such as Cook distance,score statistics are derived.The local influence measure of Cook is also presented. A numerical example illustrates that the method is available.展开更多
The paper concerns the issue of size law,localized deformation and dilation or compaction due to shear localization. It is assumed that the shear localization initiates at the peak shear stress in the form of single s...The paper concerns the issue of size law,localized deformation and dilation or compaction due to shear localization. It is assumed that the shear localization initiates at the peak shear stress in the form of single shear band,and based on gradient-dependent plasticity,an analytical solution on size effect or snap-back is obtained. The results show that the post peak response becomes steeper and even exhibits snap-back with increasing of length. For small specimen,the relative shear displacement when specimen failure occurs is lower than that of larger specimen and the shear stress-relative displacement curve becomes steeper. The theoretical solution on non-uniformity of strains in shear band is obtained and evolution of the relative shear displacement is represented. By resorting to the linear relation between local plastic shear strain and local plastic volumetric strain,the dilation and compaction within shear band are analyzed. Relation between apparent shear strain and apparent normal strain and relation between shear displacement and vertical displacement are established.展开更多
This paper presents a unified diagnostic method for exponential nonlinear models with random effects based upon the joint likelihood given by Robinson in 1991. The authors show that the case deletion model is equivale...This paper presents a unified diagnostic method for exponential nonlinear models with random effects based upon the joint likelihood given by Robinson in 1991. The authors show that the case deletion model is equivalent to mean shift outlier model. From this point of view, several diagnostic measures, such as Cook distance, score statistics are derived. The local influence measure of Cook is also presented. Numerical example illustrates that our method is available.展开更多
Mechanical properties of TC17 titanium alloy undergo a significant reduction after linear friction welding(LFW),of which the strength and ductility are hard to be improved simultaneously by traditional aging heat trea...Mechanical properties of TC17 titanium alloy undergo a significant reduction after linear friction welding(LFW),of which the strength and ductility are hard to be improved simultaneously by traditional aging heat treatment(AHT),seriously limiting the application of LFW in the manufacturing of TC17 titanium alloy blisks.To this end,the present work proposes to use electric pulse treatment(EPT)to enhance the strength and ductility of TC17 LFW joints simultaneously by improving its microstructure.The results show that,in comparison to the uneven distribution ofαphases in the welding zone(WZ),heat-affected zone(HAZ),and base metal(BM)zone after AHT,EPT can selectively homogenize theαphase distribution of WZ and HAZ without impacting the BM.The selective effect of EPT is reflected as the synergistic influence of the local Joule heating effect and the electron wind effect,which promotes the diffusion ofβphase stabilizing element Mo and leads to a competitive precipitation ofβphase andαphase in theαphase transition temperature range.The ratio ofαphase toβphase in the WZ and HAZ finally approaches an equilibrium point which is similar to that of BM,leading to a uniform distribution ofαphase and realizing the synergy of strength-ductility of LFW joint:the maximum strength increase observed is 12.9%,accompanied by a corresponding elongation increase of 122%(by AHT&EPT),and the maximum plasticity improvement is 185%,accompanied by a corresponding strength increase of 4.3%(by EPT for 1 h).This study provides essential insights for improving the strength and ductility of LFW TC17 titanium alloy blisks and enhancing the applications of LFW in aeroengine components.展开更多
In this work, we focus on assessing the group effect of localized corrosion on the ultimate strength of the marine structural plates and study the load-deformation behaviors of plates of various slenderness and uniaxi...In this work, we focus on assessing the group effect of localized corrosion on the ultimate strength of the marine structural plates and study the load-deformation behaviors of plates of various slenderness and uniaxial compression.Meanwhile, we investigate different corroded patterns from a single circular pit to 25 circular pits distributed over the plate and carry out hundreds of nonlinear finite element simulations by combining the number, depth, distribution of pits with imperfections and slenderness of plate. The distribution of multiple pits causes scattering of stress concentration on the plate, then the plastic section of plate changes with wider distribution of damage simultaneously. The ultimate strength arises when un-loading zone comprised of the yielding strips and holes extends across the plate. It can be concluded that the corroded condition defined as group effect of pits manipulates the deformation state and the loading capacity of plate at the ultimate strength mode that coincides with the proportion of effective loading area and section in the process of post-buckling. To validate the effect of pits group, we perform the numerical experiments of the post-buckling of steel plates containing pits in a row with different orientation.展开更多
Through the Three Gorges well network, we examine different coseismic changes in water temperature caused by local earthquakes since 2008, and offer a mechanistic explanation.The relations between the coseismic change...Through the Three Gorges well network, we examine different coseismic changes in water temperature caused by local earthquakes since 2008, and offer a mechanistic explanation.The relations between the coseismic changes in water temperature and the parameters of distant and local earthquakes are deduced.展开更多
基金National Natural Science Foundation of China(No.61671414)Natural Science Foundation for Young Scientists of Shanxi Province,China(No.201601D202035)
文摘Research of the acoustic local effect of metamaterial is widely used in the fields of environmental science,military industry and biomedicine.In this paper,the metamaterial is designed by annular columnar structures.The acoustic local effect in slender columnar structure with two layers of rings in air is investigated.Results prove that when the plane acoustic wave is incident into the model,complex interference and diffraction occur.And at different frequencies,multipolar acoustic local effect existes and cycle distribution phenomenon is observed.It is noteworthy that this phenomenon has very weak relatedness with the materials and acoustic parameters of the model.The research of this metamaterial design in this paper has definite reference significance in the acoustic communication and amplification of the acoustic signal detection.
文摘In this paper, traveling wavefront solutions are established for two cooperative systems with time delay and non-local effects. The results are an extension of the existing results for delayed logistic scale equations and diffusive Nicholson equations with non-local effects to systems. The approach used is the upper-lower solution technique and Schauder fixed point Theorem developed by Ma（J Differential Equations,2001,171：294-314. ）.
基金Supported by NNSF of China(11026099)NSF of Shandong Province(ZR2010AQ006)
文摘In this paper,we consider the reaction diffusion equations with strong generic delay kernel and non-local effect,which models the microbial growth in a flow reactor.The existence of traveling waves is established for this model.More precisely,using the geometric singular perturbation theory,we show that traveling wave solutions exist provided that the delay is sufficiently small with the strong generic delay kernel.
基金Projects(51774138,51804122,51904105)supported by the National Natural Science Foundation of ChinaProjects(E2021209148,E2021209052)supported by the Natural Science Foundation of Hebei Province,China。
文摘By utilizing wave velocity imaging technology,the uniaxial multi-stage loading test was conducted on siltstone to attain wave velocity imagings during rock fracture.Based on the time series parameters of acoustic emissions(AE),joint response characteristics of the velocity field and AE during rock fracture were analyzed.Moreover,the localization effect of damage during rock fracture was explored by applying wave velocity imagings.The experimental result showed that the wave velocity imagings enable three-dimensional(3-D)visualization of the extent and spatial position of damage to the rock.A damaged zone has a low wave velocity and a zone where the low wave velocity is concentrated tends to correspond to a severely damaged zone.AE parameters and wave velocity imagings depict the changes in activity of cracks during rock fracture from temporal and spatial perspectives,respectively:the activity of cracks is strengthened,and the rate of AE events increases during rock fracture;correspondingly,the low-velocity zones are gradually aggregated and their area gradually increases.From the wave velocity imagings,the damaged zones in rock were divided into an initially damaged zone,a progressively damaged zone,and a fractured zone.During rock fracture,the progressively damaged zone and the fractured zone both develop around the initially damaged zone,showing a typical localization effect of the damage.By capturing the spatial development trends of the progressively damaged zone and fractured zone in wave velocity imagings,the development of microfractures can be predicted,exerting practical significance for determining the position of the main fracture.
基金This research was supported by the National Key R&D Program of China(2018YFB1502801).
文摘Zhangjiakou is an important wind power base in Hebei Province,China.The impact of its wind farms on the local climate is controversial.Based on long-term meteorological data from 1981 to 2018,we investigated the effects of the Shangyi Wind Farm(SWF)in Zhangjiakou on air temperature,wind speed,relative humidity,and precipitation using the anomaly or ratio method between the impacted weather station and the non-impacted background weather station.The influence of the SWF on land surface temperature(LST)and evapotranspiration(ET)using MODIS satellite data from 2003 to 2018 was also explored.The results showed that the SWF had an atmospheric warming effect at night especially in summer and autumn(up to 0.95℃).The daytime air temperature changes were marginal,and their signs were varying depending on the season.The annual mean wind speed decreased by 6%,mainly noted in spring and winter(up to 14%).The precipitation and relative humidity were not affected by the SWF.There was no increase in LST in the SWF perhaps due to the increased vegetation coverage unrelated to the wind farms,which canceled out the wind farm-induced land surface warming and also resulted in an increase in ET.The results showed that the impact of wind farms on the local climate was significant,while their impact on the regional climate was slight.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 72174121 and 71774111)the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learningthe Natural Science Foundation of Shanghai (Grant No. 21ZR1444100)
文摘Today,with the rapid development of the internet,a large amount of information often accompanies the rapid transmission of disease outbreaks,and increasing numbers of scholars are studying the relationship between information and the disease transmission process using complex networks.In fact,the disease transmission process is very complex.Besides this information,there will often be individual behavioral measures and other factors to consider.Most of the previous research has aimed to establish a two-layer network model to consider the impact of information on the transmission process of disease,rarely divided into information and behavior,respectively.To carry out a more in-depth analysis of the disease transmission process and the intrinsic influencing mechanism,this paper divides information and behavior into two layers and proposes the establishment of a complex network to study the dynamic co-evolution of information diffusion,vaccination behavior,and disease transmission.This is achieved by considering four influential relationships between adjacent layers in multilayer networks.In the information layer,the diffusion process of negative information is described,and the feedback effects of local and global vaccination are considered.In the behavioral layer,an individual's vaccination behavior is described,and the probability of an individual receiving a vaccination is influenced by two factors:the influence of negative information,and the influence of local and global disease severity.In the disease layer,individual susceptibility is considered to be influenced by vaccination behavior.The state transition equations are derived using the micro Markov chain approach(MMCA),and disease prevalence thresholds are obtained.It is demonstrated through simulation experiments that the negative information diffusion is less influenced by local vaccination behavior,and is mainly influenced by global vaccination behavior;vaccination behavior is mainly influenced by local disease conditions,and is less influenced by global disease conditions;the disease transmission threshold increases with the increasing vaccination rate;and the scale of disease transmission increases with the increasing negative information diffusion rate and decreases with the increasing vaccination rate.Finally,it is found that when individual vaccination behavior considers both the influence of negative information and disease,it can increase the disease transmission threshold and reduce the scale of disease transmission.Therefore,we should resist the diffusion of negative information,increase vaccination proportions,and take appropriate protective measures in time.
基金supported by the University of Kashan(No.463865/13)the Iranian Nanotechnology Development Committee
文摘A non-local solution for a functionally graded piezoelectric nano-rod is pre- sented by accounting the surface effect. This solution is used to evaluate the charac- teristics of the wave propagation in the rod structure. The model is loaded under a two-dimensional （2D） electric potential and an initially applied voltage at the top of the rod. The mechanical and electrical properties are assumed to be variable along the thick- ness direction of the rod according to the power law. The Hamilton principle is used to derive the governing differential equations of the electromechanical system. The effects of some important parameters such as the applied voltage and gradation of the material properties on the wave characteristics of the rod are studied.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFB0401801)the National Natural Science Foundation of China(Grant Nos.61674138,61674139,61604145,61574135,61574134,61474142,61474110,61377020,and 61376089)+1 种基金Science Challenge Project,China(Grant No.JCKY2016212A503)One Hundred Person Project of the Chinese Academy of Sciences
文摘Four blue-violet light emitting InGaN/GaN multiple quantum well（MQW） structures with different well widths are grown by metal–organic chemical vapor deposition. The carrier localization effect in these samples is investigated mainly by temperature-dependent photoluminescence measurements. It is found that the localization effect is enhanced as the well width increases from 1.8 nm to 3.6 nm in our experiments. The temperature induced PL peak blueshift and linewidth variation increase with increasing well width, implying that a greater amplitude of potential fluctuation as well as more localization states exist in wider wells. In addition, it is noted that the broadening of the PL spectra always occurs mainly on the low-energy side of the PL spectra due to the temperature-induced band-gap shrinkage, while in the case of the widest well, a large extension of the spectral curve also occurs in the high energy sides due to the existence of more shallow localized centers.
文摘Local thermal effect influencing the fluorescence of triply ionized rare earth ions doped in nanocrystals is studied with laser spectroscopy and theory of thermal transportation for transparent oxyfluoride glass ceramics containing nanocrystals. The result shows that the local temperature of the nanocrystals embedded in glass matrices is much higher than the environmental temperature of the sample. It is suggested that the tempera,ture-dependent thermal energy induced by the light absorption must be considered when the theory of thermal transportation is applied to the study of local thermal effect.
基金The project supported by the National Natural Science Foundation of China (10121202) and Ministry of Education,China (20020003023 and Key Grant Project 0306)
文摘Recent studies have shown that the size of microvoids has a significant effect on the void growth rate.The purpose of this paper is to explore whether the void size effect can influence the plastic flow localization in ductile materials.We have used the extended Gurson's dilatational plasticity theory,which accounts for the void size effect,to study the plastic flow localization in porous solids with long cylindrical voids.The localization model of Rice is adopted,in which the material inside the band may display a different response from that outside the band at the incipient plastic flow localization.The present study shows that it has little effect on the shear band angle.
基金Project(No.20100481432)supported by the China Postdoctoral Science Foundation
文摘Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.
文摘The localized effect of light diffracted by a capillary wave is discovered by changing the wave amplitude. The localized range is related to the wave number and the amplitude. The dependence of the half maximum localized angle on the wave number and amplitude is analytically derived. Meanwhile, the analytic angular distribution of the diffraction light in the localized range is obtained. Experiments are carried out to achieve diffraction patterns to confirm the localized effect and to measure the angular distribution of the diffraction light intensity as well as to determine the localized range scales corresponding to different wave amplitudes. Theoretical curves of the light intensity angular distribution and localized interval widths related to surface acoustic wave amplitudes are compared with the experimental data. The experimental results agree well with the theoretical prediction.
基金supported by the National Basic Research Program of China(Grant No.2012CB933102)the National Natural Science Foundation of China(Grant Nos.11079052,11174354,and 51172080)
文摘An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are related to the CoFeB thickness.When the film is thicker than 3 nm,the side jump mechanism dominates and the weak locaUzation to AHC vanishes.For very thin CoFeB films,both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect,and the weak localization correction to AHC is observed.
基金supported by the National Natural Science Foundation of China,No.81271090 and the Beijing Natural Science Foundation,No.7112055
文摘The precedence effect is a prerequisite for faithful sound localization in a complex auditory environment, and is a physiological phenomenon in which the auditory system selectively suppresses the directional information from echoes. Here we investigated how neurons in the inferior colliculus respond to the paired sounds that produce precedence-effect illusions, and whether their firing behavior can be modulated through inhibition with gamma-aminobutyric acid （GABA）. We recorded extracellularly from 36 neurons in rat inferior colliculus under three conditions： no injection, injection with saline, and injection with gamma-aminobutyric acid. The paired sounds that produced precedence effects were two identical 4-ms noise bursts, which were delivered contralaterally or ipsilaterally to the recording site. The normalized neural responses were measured as a function of different inter-stimulus delays and half-maximal interstimulus delays were acquired. Neuronal responses to the lagging sounds were weak when the inter-stimulus delay was short, but increased gradually as the delay was lengthened. Saline injection produced no changes in neural responses, but after local gamma-arninobutyric acid application, responses to the lagging stimulus were suppressed. Application of gamma-aminobutyric acid affected the normalized response to lagging sounds, independently of whether they or the paired sounds were contralateral or ipsilateral to the recording site. These observations suggest that local inhibition by gamma-aminobutyric acid in the rat inferior colliculus shapes the neural responses to lagging sounds, and modulates the precedence effect.
基金The research project supported by NSFC(1 9631 0 4 0 ) and NSFJ
文摘In this paper,a unified diagnostic method for the nonlinear models with random effects based upon the joint likelihood given by Robinson in 1991 is presented.It is shown that the case deletion model is equivalent to the mean shift outlier model.From this point of view,several diagnostic measures,such as Cook distance,score statistics are derived.The local influence measure of Cook is also presented. A numerical example illustrates that the method is available.
基金Supported by the National Natural Science Foundation of China(50309004)。
文摘The paper concerns the issue of size law,localized deformation and dilation or compaction due to shear localization. It is assumed that the shear localization initiates at the peak shear stress in the form of single shear band,and based on gradient-dependent plasticity,an analytical solution on size effect or snap-back is obtained. The results show that the post peak response becomes steeper and even exhibits snap-back with increasing of length. For small specimen,the relative shear displacement when specimen failure occurs is lower than that of larger specimen and the shear stress-relative displacement curve becomes steeper. The theoretical solution on non-uniformity of strains in shear band is obtained and evolution of the relative shear displacement is represented. By resorting to the linear relation between local plastic shear strain and local plastic volumetric strain,the dilation and compaction within shear band are analyzed. Relation between apparent shear strain and apparent normal strain and relation between shear displacement and vertical displacement are established.
文摘This paper presents a unified diagnostic method for exponential nonlinear models with random effects based upon the joint likelihood given by Robinson in 1991. The authors show that the case deletion model is equivalent to mean shift outlier model. From this point of view, several diagnostic measures, such as Cook distance, score statistics are derived. The local influence measure of Cook is also presented. Numerical example illustrates that our method is available.
基金the National Science Fund for Distinguished Young Scholars(No.52225505)the National Sci-ence and Technology Major Project(No.J2019-VII-0014-0154)+1 种基金the National Natural Science Foundation of China(No.52005412)the Open Research Fund of State Key Laboratory of Precision Man-ufacturing for Extreme Service Performance(No.Kfkt2023-12)for financial supports given to this research.
文摘Mechanical properties of TC17 titanium alloy undergo a significant reduction after linear friction welding(LFW),of which the strength and ductility are hard to be improved simultaneously by traditional aging heat treatment(AHT),seriously limiting the application of LFW in the manufacturing of TC17 titanium alloy blisks.To this end,the present work proposes to use electric pulse treatment(EPT)to enhance the strength and ductility of TC17 LFW joints simultaneously by improving its microstructure.The results show that,in comparison to the uneven distribution ofαphases in the welding zone(WZ),heat-affected zone(HAZ),and base metal(BM)zone after AHT,EPT can selectively homogenize theαphase distribution of WZ and HAZ without impacting the BM.The selective effect of EPT is reflected as the synergistic influence of the local Joule heating effect and the electron wind effect,which promotes the diffusion ofβphase stabilizing element Mo and leads to a competitive precipitation ofβphase andαphase in theαphase transition temperature range.The ratio ofαphase toβphase in the WZ and HAZ finally approaches an equilibrium point which is similar to that of BM,leading to a uniform distribution ofαphase and realizing the synergy of strength-ductility of LFW joint:the maximum strength increase observed is 12.9%,accompanied by a corresponding elongation increase of 122%(by AHT&EPT),and the maximum plasticity improvement is 185%,accompanied by a corresponding strength increase of 4.3%(by EPT for 1 h).This study provides essential insights for improving the strength and ductility of LFW TC17 titanium alloy blisks and enhancing the applications of LFW in aeroengine components.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51490670 and 11572300)R&D Plan(Grant No.2017GHY15120)Fundamental Research Fund for Central Universities(Ocean University of China)
文摘In this work, we focus on assessing the group effect of localized corrosion on the ultimate strength of the marine structural plates and study the load-deformation behaviors of plates of various slenderness and uniaxial compression.Meanwhile, we investigate different corroded patterns from a single circular pit to 25 circular pits distributed over the plate and carry out hundreds of nonlinear finite element simulations by combining the number, depth, distribution of pits with imperfections and slenderness of plate. The distribution of multiple pits causes scattering of stress concentration on the plate, then the plastic section of plate changes with wider distribution of damage simultaneously. The ultimate strength arises when un-loading zone comprised of the yielding strips and holes extends across the plate. It can be concluded that the corroded condition defined as group effect of pits manipulates the deformation state and the loading capacity of plate at the ultimate strength mode that coincides with the proportion of effective loading area and section in the process of post-buckling. To validate the effect of pits group, we perform the numerical experiments of the post-buckling of steel plates containing pits in a row with different orientation.
基金supported by the China Three Gorges Corporation Research Fund (SXSN/3354)
文摘Through the Three Gorges well network, we examine different coseismic changes in water temperature caused by local earthquakes since 2008, and offer a mechanistic explanation.The relations between the coseismic changes in water temperature and the parameters of distant and local earthquakes are deduced.
