Polarization manipulation is a significant issue for artificial modulation of the electromagnetic(EM) wave, but general mechanisms all suffer the restriction of inherent symmetric properties between opposite handednes...Polarization manipulation is a significant issue for artificial modulation of the electromagnetic(EM) wave, but general mechanisms all suffer the restriction of inherent symmetric properties between opposite handedness.Herein, a strategy to independently and arbitrarily manipulate the EM wave with orthogonal circular polarizations based on a metasurface is proposed, which effectually breaks through traditional symmetrical characteristics between orthogonal handedness. By synthesizing the propagation phase and geometric phase, the appropriate Jones matrix is calculated to obtain independent wavefront manipulation of EM waves with opposite circular polarizations. Two transmissive ultra-thin meta-deflectors are proposed to demonstrate the asymmetrical refraction of transmitted circularly polarized waves in the microwave region. Simulated transmitted phase front and measured far-field intensity distributions are in excellent agreement, indicating that the transmitted wave with different polarizations can be refracted into arbitrary and independent directions within a wide frequency band(relative bandwidth of 25%). The results presented in this paper provide more freedom for the manipulation of EM waves, and motivate the realizations of various polarization-independent properties for all frequency spectra.展开更多
In asymmetric rolling(ASR) the circumferential velocities of the working rolls are different. This yields a complex deformation mode with shear, compression and rigid body rotation components. The main microstructural...In asymmetric rolling(ASR) the circumferential velocities of the working rolls are different. This yields a complex deformation mode with shear, compression and rigid body rotation components. The main microstructural modification is on crystallographic texture, and, for aluminium alloys, this may improve the deformability after recrystallization. This work correlated the process variables, thickness reduction per pass(TRP) and velocity ratio between the upper and bottom rolls, with the texture development and the plastic properties after annealing. Finite element(FE) simulations were performed to quantify the influence of the strain components. Experimental data on texture, and plastic anisotropy were analyzed. In the sheet centre a crystallographic rotation of the compression components about the TD(transverse direction) axis was obtained, which yielded the development of {111}//ND(normal direction) texture components. On the surfaces the local variation of the velocity gradients caused an extra rotation component about ND. This yielded the increment of rotated cube components. After annealing the main texture components at the sheet centre were maintained and the texture intensity decreased. The planar anisotropy(△r) was reduced but the normal anisotropy and deep drawability obtained by the Erichsen test were similar for all conditions. The most favourable reduction of △r was obtained at a velocity ratio of 1.5 and TRP of 10%.展开更多
A version of the geoelectrochemical prospecting technique developed in China was demonstrated in China and Australia to test its suitability under both Chinese and Australian conditions.This paper briefly describes th...A version of the geoelectrochemical prospecting technique developed in China was demonstrated in China and Australia to test its suitability under both Chinese and Australian conditions.This paper briefly describes the mechanism and effectiveness of the technique applied to search of concealed mineralisation through regolith cover,based on both experimental and field tests.This paer deals with three main aspects of the method: a) how metallic ions are released from orebodies by electrochemical dissolution;b)how these ions migrate to the collector and are deposited as elements by electrochemical extraction in the presence of an electric field; and c) the effectiveness of the method illustrated by some case studies.展开更多
In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a me...In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a metasurface and plasma.A metasurface with three absorption peaks is designed by means of an equivalent circuit based on an electromagnetic resonance type metamaterial absorber.The reflection and absorption of the composite structure are numerically and experimentally verified.The finite integration method was used to simulate a composite structure of finite size to obtain the RCS.The experimental measurements of electromagnetic wave reflection were conducted by a vector network analyzer(Keysight N5234A)and horn antennas,etc.The research showed that the absorption capacity of this composite structure was substantially improved compared to either the plasma or the metasurface,and it is more convenient for application due to its low plasma thickness requirement and easy fabrication.展开更多
The fatigue life of numerous aerospace,locomotive,automotive and biomedical structures may go beyond 10~8 cycles.Determination of long life fatigue behavior becomes extremely important for better understanding and des...The fatigue life of numerous aerospace,locomotive,automotive and biomedical structures may go beyond 10~8 cycles.Determination of long life fatigue behavior becomes extremely important for better understanding and design of the components and structures.Initially,before the invention of ultrasonic fatigue testing,most of the engineering materials were supposed to exhibit fatigue life up to 10~7 cycles or less.This paper reviews current understanding of some fundamental aspects on the development of accelerated fatigue testing method and its application in ultra-high cycle fatigue,crack initiation and growth mechanisms of internal fracture,S-N diagram,fatigue limit and life prediction, etc.展开更多
Background:Patterns of rarity can be explained by reproductive rates,levels of endemism,and habitat specificity,and knowledge on these parameters is important to understand the levels of vulnerability of each species ...Background:Patterns of rarity can be explained by reproductive rates,levels of endemism,and habitat specificity,and knowledge on these parameters is important to understand the levels of vulnerability of each species and to formulate conservation strategies.Here,we studied nest-site selection and breeding biology of the Atlantic Royal Flycatcher(Onychorhynchus swainsoni),a poorly known vulnerable bird endemic to the Brazilian Atlantic Forest.Methods:We addressed nest site selection in three different levels:first,we searched for nests near and far from water to investigate whether birds could select water proximities to construct nests;second,we examined if they could select certain streams in detriment of others,and we analyzed the characteristics of used and non-used streams,and third,in streams in which nests were found,we addressed nest site selectivity by comparing a number of parameters between nest sites and random sites.Further,we provide information on breeding biology parameters related to annual fecundity.Results:During five breeding seasons,we found 23 nests in a well-preserved forest continuum.All of the nests were constructed above water,and they were found in streams that were about 4 m in width,instead of smaller streams with about 1.5 m in width.Modeling analyses revealed that within the used streams,nests were constructed in sites with lower vegetation density in relation to random points,while stream width,water speed,and canopy cover presented no significant correlation.Atlantic Royal Flycatchers in our study had a 22-day incubation period and 24 to 27-day nestling period.Overall nest survival was comparatively high(62%),but clutch size was small(N=2 eggs)and Along the nesting streams,we found an average of 1.62±0.07 breeding pairs/km.Conclusions:These data suggest that nesting habitat specificity and low annual fecundity are among the factors contributing to the rarity of the Atlantic Royal Flycatcher in large forest continuums and to its absence in fragmented environments.It reinforces the importance of large well-preserved forest continuums for the conservation of habitat specialist Atlantic Forest bird species.展开更多
Carbon-manganese steel is often applied in components of pipes in nuclear plant. Ultrasonic fatigue tests following low cycle fatigue （LCF） cycles damaged are used to study the strength of very high cycle fatigure ...Carbon-manganese steel is often applied in components of pipes in nuclear plant. Ultrasonic fatigue tests following low cycle fatigue （LCF） cycles damaged are used to study the strength of very high cycle fatigure （VHCF）. The comparison of test results of simple VHCF and cumulative fatigue （LCF plus VHCF） shows that LCF load influences the following VHCF strength. Continuum damage mechanics model is extended to VHCF region.展开更多
The electron kinetic model for investigating the transport and ionization rate coefficients of argon glow discharge dusty plasma is developed from the Boltzmann equation.Both of the electron-neutral and electron-dust ...The electron kinetic model for investigating the transport and ionization rate coefficients of argon glow discharge dusty plasma is developed from the Boltzmann equation.Both of the electron-neutral and electron-dust collisions are considered as collision terms in the kinetic equation.The kinetic equation is simplified by employing the local approximation and nonlocal approach under the same discharge conditions,and the corresponding simplified kinetic equations are known as local and nonlocal kinetic equations respectively.Then the electron energy distribution function(EEDF)is obtained by numerically solving the local and nonlocal kinetic equations and the dust charging equations simultaneously.Based on the obtained EEDFs,the effective electron temperature,electron mobility,electron diffusion coefficient and ionization rate coefficient are calculated for different discharge conditions.It is shown that the EEDFs calculated from the local kinetic model clearly differ from the nonlocal EEDFs and both the local and nonlocal EEDFs are also clearly different with Maxwellian distributions.The appearance of dust particles results in an obvious decrease of high energy electrons and increase of low energy electrons when axial electric field is low.With the increase of axial electric field,the influence of dust particles on the EEDFs becomes smaller.The electron mobility and diffusion coefficients calculated on the basis of local and nonlocal EEDFs do not differ greatly to the dust-free ones.While,when dust density nd=10^6 cm^?3,the electron mobility increases obviously compared with the dust-free results at low axial electric field and decreases with the increasing axial electric field until they are close to the dust-free ones.Meanwhile,electron diffusion coefficients for dusty case become smaller and decrease with the increasing axial electric field.The ionization rate coefficients decrease when dust particles are introduced and they approach the dust-free results gradually with the increasing axial electric field.展开更多
A self-consistent fluid model is developed to investigate the radial distributions of dusty plasma parameters in a DC glow discharge,in which the extended fluid approach of plasma particles and the transport equations...A self-consistent fluid model is developed to investigate the radial distributions of dusty plasma parameters in a DC glow discharge,in which the extended fluid approach of plasma particles and the transport equations of dust particles are coupled.The electrical interaction between charged dust particles is considered in the model.The time evolution of radial distributions of dust density,plasma density,the radial component of electric field and the forces acting on dust particles when dust density tends to be stable,are obtained and analyzed under different discharge currents and dust particle radii.It is shown that the dust density structure is determined mainly by the radial electrostatic force,thermophoretic force and ion drag force in the discharge tube,and both discharge current and dust particle radius have an obvious effect on the transport processes of dust particles.The dust particles gather in the central region of the discharge tube for low discharge current and small dust radius,then dust voids are formed and become wider when the discharge current and dust radius increase.The plasma parameters in the dust gathering region are obviously affected by the dust particles due to the charging processes of electrons and ions to the dust surface.展开更多
The electromagnetic pulse excited by the collision between a hypervelocity meteoroid and a spacecraft is studied both numerically and theoretically.It is found that there are two kinds of electromagnetic pulse.The hig...The electromagnetic pulse excited by the collision between a hypervelocity meteoroid and a spacecraft is studied both numerically and theoretically.It is found that there are two kinds of electromagnetic pulse.The high-frequency electromagnetic pulse may be excited by the sum of all the electric dipoles.Each electron can be considered as an electric dipole.The low-frequency electromagnetic pulse is produced by the Langmuir oscillation of electrons.The energy flux density and the duration time of the excited low-frequency electromagnetic pulse by the meteoroid are also studied in the present paper.It is shown that the energy flux density increases as either the impact speed or the mass of the meteoroid increases.It is also shown that the duration time decreases as both the impact speed and the mass of the meteoroid increase.By measuring the strength and the duration time of the electromagnetic pulse excited by the collision between the hypervelocity meteoroid and spacecraft,we can estimate the speed and the mass of the hypervelocity meteoroid,which will be helpful in space flight and space exploration.展开更多
This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust char...This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust charging process and magnetic field.We discuss the dielectric permittivity of dusty plasma in several cases,such as high frequency approximation,parallel propagation in MF/HF band,and effects of plasma movement.Finally,the expressions are employed to study the phenomenon of radar echoes from the polar summer mesosphere.We report that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω–4 and produces a number density of charged dust that agrees with measurements of mesopheric radar echoes.展开更多
The case describes the situation of a Brazilian accounting courses in undergraduate programmes middle-class family, as an alternative to teach introductory In its solution, it was used an accounting system, adapted to...The case describes the situation of a Brazilian accounting courses in undergraduate programmes middle-class family, as an alternative to teach introductory In its solution, it was used an accounting system, adapted to the needs of register, control, and information of the family equity, through the application of the content of introductory accounting. The authors aim to offer a didactic and playful alternative for the teaching of introductory accounting in undergraduation courses, such as business management, accountancy, economy, and others in which this course is offered. The aim is to show the integration of accounting contents offered in the course, applied to the most common and nearest experience of freshmen in their first year during the undergraduate program： the family. The case can be solved in two phases： In the first, during a class of up to 100 minutes, the professor develops six activities, culminating in the students answering up to four suggested questions; in the second, whose application is left to the professor, in another class further ahead, is numerical.展开更多
This report describes a 58 -year -old patient with a giant unruptured asympt omatic aneurysmof right valsava sinus, as well as the significant contribution o f magnetic resonance imaging in diagnosis of this cardiovas...This report describes a 58 -year -old patient with a giant unruptured asympt omatic aneurysmof right valsava sinus, as well as the significant contribution o f magnetic resonance imaging in diagnosis of this cardiovascular disorder and id entification of its relationship with surrounding thoracic organs.展开更多
Crosslinking is one of the most commonly reactions used to improve the physical properties of cellulose derivatives. Cellulose Acetate Propionate (CAP) is a commercial ester obtained as a cellulose derivative and it c...Crosslinking is one of the most commonly reactions used to improve the physical properties of cellulose derivatives. Cellulose Acetate Propionate (CAP) is a commercial ester obtained as a cellulose derivative and it can be used as basis for the synthesis of crosslinked chains as described in this work. Typical used crosslinkers are di-functional compounds, such as dianhydrides or diisocyanate. The formation of polymeric 3D structures as described in this work occurs typically by the reaction of the linear chains bearing free OH groups with crosslinking agents such as dianhydrides. These reactions are used to make a very absorbent material, typically a gel. The syntheses were performed in homogeneous medium with acetate propionate in a very dry atmosphere by employing PMDA (Pyromellitic Dianhydride) and BTDA (3,3’, 4,4’ Benzophenone Tetracarboxylated Dianhydride) as crosslinking agents in a reflux system. TGA analysis has shown the different thermal stability of the gels when compared with CAP. Typical TGA curves have demonstrated the lower stability of the crosslinked chains when compared to CAP as consequence of esther linkages formed in the gels structures. The Mc, which is the value for the molar mass between crosslinkings points in 3D structure, was determined according to Flory-Rehner theory. This important parameter has demonstrated greater reactivity of PMDA in comparison with the BTDA in the reactions conditions’ employed in this work.展开更多
Spin-orbital interaction characterizes the momentum coupling between polarization and spatial behaviors of electromagnetic waves.The corresponding transition phenomena have been recently manifested by geometric phase ...Spin-orbital interaction characterizes the momentum coupling between polarization and spatial behaviors of electromagnetic waves.The corresponding transition phenomena have been recently manifested by geometric phase metasurfaces,which provide compact and intuitive platforms to replace traditional optical waveplate cascading systems.Nevertheless,metasurfaces based on geometric phase can only impose two opposite modes of orbital angular momentum(OAM)in conjugate spin channels.Although cross-talks among adjacent channels can be exhaustedly minimized,the purity and efficiency of spin-orbital transitions would still be impacted by the coexisting conjugate coupling.Here,we exploit a metasurface with non-orthogonal eigen formalism to achieve the channel-locked spin-orbital transitions,where the output spin state can be constantly fixed while at the same time imposed with versatile modes of OAM with high purity and efficiency.Besides,the robustness of the channel-locked spin-orbital transition is also demonstrated under full polarization illuminations.Such results provide a scheme for full-Stokes beam generation and high-performance meta-polarizer design,which shows the potential of reconfigurable polarization control in wireless communication systems.展开更多
In recent years,important progress has been made in the field of biosensing and wireless communications by using metamaterials and metasurfaces.These technologies enable efficient manipulation of electromagnetic waves...In recent years,important progress has been made in the field of biosensing and wireless communications by using metamaterials and metasurfaces.These technologies enable efficient manipulation of electromagnetic waves through judiciously designed subwavelength structural units.This review begins by focusing on the design and optimization of terahertz metasurface sensors,emphasizing their unique advantages in biomedical diagnostics.It explores key technical challenges,such as material selection,device integration,and development of robust sensor for surface-specific modifications.Furthermore,the review discusses how metasurfaces,particularly as reconfigurable intelligent surfaces,dynamically modulate electromagnetic wave propagation in the microwave communications domain to enhance signal quality,improve communication efficiency,and showcase their potential in 5G and future 6G technologies.Finally,a comprehensive overview is provided regarding the challenges and future research directions for metamaterial and metasurface technologies in both biosensing and wireless communications,with the ultimate goal of promoting their applications in point-of-care devices and efficient communication systems.展开更多
A general method to realize arbitrary dual-band independent phase control is proposed and demonstrated in this paper.A double-layered C-shape reflective meta-atom is designed to realize independent phase control with ...A general method to realize arbitrary dual-band independent phase control is proposed and demonstrated in this paper.A double-layered C-shape reflective meta-atom is designed to realize independent phase control with high efficiency.As a proof of concept,we propose two functional metasurfaces in the microwave region;the first metasurface performs beam steering in different directions,and the second metasurface generates achromatic beam steering at two distinct frequencies.Both simulation and measurement results agree well with the theoretical pre-setting.The maximum measured efficiency is 88.7%and 92.3%at 6.8 GHz and 8.0 GHz,respectively,for one metasurface,and 91.0%and 89.8%at 6.9 GHz and8.6 GHz,respectively,for the other.展开更多
Fourier transform, mapping the information in one domain to its reciprocal space, isof fundamental significance in real-time and parallel processing of massive data forsound and image manipulation. As a powerful platf...Fourier transform, mapping the information in one domain to its reciprocal space, isof fundamental significance in real-time and parallel processing of massive data forsound and image manipulation. As a powerful platform of high-efficiency wavecontrol, Huygens’ metasurface may offer to bridge the electromagnetic signalprocessing and analog Fourier transform at the hardware level and with remarkablyimproved performance. We here demonstrate a Huygens’ metasurface hologram,where the image pattern can be self-rotated or projected in free space bymodulating the phase distribution based on the rotational invariance, time-shiftingand scaling properties of Fourier transform. Our proof-of-concept experiment showshigh-efficiency imaging operation in accordance with theoretical predictions,validating the proposed scheme as an ideal way to perform largely parallel spatialdomainmathematical operations in the analog domain using electromagnetic fields.展开更多
In this paper, a novel strategy based on a metasurface composed of simple and compactunit cells to achieve ultra-high-speed trigonometric operations under specificinput values is theoretically and experimentally demon...In this paper, a novel strategy based on a metasurface composed of simple and compactunit cells to achieve ultra-high-speed trigonometric operations under specificinput values is theoretically and experimentally demonstrated. An electromagneticwave (EM)-based optical diffractive neural network with only one hidden layer isphysically built to perform four trigonometric operations (sine, cosine, tangent, andcotangent functions). Under the unique composite input mode strategy, the designedoptical trigonometric operator responds to incident light source modes that representdifferent trigonometric operations and input values (within one period), and generatescorrect and clear calculated results in the output layer. Such a wave-based operationis implemented with specific input values, and the proposed concept work may offerbreakthrough inspiration to achieve integrable optical computing devices and photonicsignal processors with ultra-fast running speeds.展开更多
基金National Natural Science Foundation of China(NSFC)(61771172,61571155,61401122)Open Project of State Key Laboratory of Millimeter Waves(K201828)
文摘Polarization manipulation is a significant issue for artificial modulation of the electromagnetic(EM) wave, but general mechanisms all suffer the restriction of inherent symmetric properties between opposite handedness.Herein, a strategy to independently and arbitrarily manipulate the EM wave with orthogonal circular polarizations based on a metasurface is proposed, which effectually breaks through traditional symmetrical characteristics between orthogonal handedness. By synthesizing the propagation phase and geometric phase, the appropriate Jones matrix is calculated to obtain independent wavefront manipulation of EM waves with opposite circular polarizations. Two transmissive ultra-thin meta-deflectors are proposed to demonstrate the asymmetrical refraction of transmitted circularly polarized waves in the microwave region. Simulated transmitted phase front and measured far-field intensity distributions are in excellent agreement, indicating that the transmitted wave with different polarizations can be refracted into arbitrary and independent directions within a wide frequency band(relative bandwidth of 25%). The results presented in this paper provide more freedom for the manipulation of EM waves, and motivate the realizations of various polarization-independent properties for all frequency spectra.
基金supported by Sao Paulo State Research Foundation (FAPESP 2016/10997-0)by CAPES–Brazil
文摘In asymmetric rolling(ASR) the circumferential velocities of the working rolls are different. This yields a complex deformation mode with shear, compression and rigid body rotation components. The main microstructural modification is on crystallographic texture, and, for aluminium alloys, this may improve the deformability after recrystallization. This work correlated the process variables, thickness reduction per pass(TRP) and velocity ratio between the upper and bottom rolls, with the texture development and the plastic properties after annealing. Finite element(FE) simulations were performed to quantify the influence of the strain components. Experimental data on texture, and plastic anisotropy were analyzed. In the sheet centre a crystallographic rotation of the compression components about the TD(transverse direction) axis was obtained, which yielded the development of {111}//ND(normal direction) texture components. On the surfaces the local variation of the velocity gradients caused an extra rotation component about ND. This yielded the increment of rotated cube components. After annealing the main texture components at the sheet centre were maintained and the texture intensity decreased. The planar anisotropy(△r) was reduced but the normal anisotropy and deep drawability obtained by the Erichsen test were similar for all conditions. The most favourable reduction of △r was obtained at a velocity ratio of 1.5 and TRP of 10%.
文摘A version of the geoelectrochemical prospecting technique developed in China was demonstrated in China and Australia to test its suitability under both Chinese and Australian conditions.This paper briefly describes the mechanism and effectiveness of the technique applied to search of concealed mineralisation through regolith cover,based on both experimental and field tests.This paer deals with three main aspects of the method: a) how metallic ions are released from orebodies by electrochemical dissolution;b)how these ions migrate to the collector and are deposited as elements by electrochemical extraction in the presence of an electric field; and c) the effectiveness of the method illustrated by some case studies.
基金financially supported by National Natural Science Foundation of China(No.12175050)the Foundation of National Key Laboratory of Electromagnetic Environment of China(No.202101003)。
文摘In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a metasurface and plasma.A metasurface with three absorption peaks is designed by means of an equivalent circuit based on an electromagnetic resonance type metamaterial absorber.The reflection and absorption of the composite structure are numerically and experimentally verified.The finite integration method was used to simulate a composite structure of finite size to obtain the RCS.The experimental measurements of electromagnetic wave reflection were conducted by a vector network analyzer(Keysight N5234A)and horn antennas,etc.The research showed that the absorption capacity of this composite structure was substantially improved compared to either the plasma or the metasurface,and it is more convenient for application due to its low plasma thickness requirement and easy fabrication.
基金supported by the National Natural Science Foundation of China(10925211)the Program for Changjiang Scholars and Innovative Research Team (IRT1027)
文摘The fatigue life of numerous aerospace,locomotive,automotive and biomedical structures may go beyond 10~8 cycles.Determination of long life fatigue behavior becomes extremely important for better understanding and design of the components and structures.Initially,before the invention of ultrasonic fatigue testing,most of the engineering materials were supposed to exhibit fatigue life up to 10~7 cycles or less.This paper reviews current understanding of some fundamental aspects on the development of accelerated fatigue testing method and its application in ultra-high cycle fatigue,crack initiation and growth mechanisms of internal fracture,S-N diagram,fatigue limit and life prediction, etc.
基金funded by the Brazilian agencies Fundacao de AmparoàPesquisa do Estado de Sao Paulo–FAPESP(Project SISBIOTA network-Top predators 2010/52315–7)fellowships from Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)productivity research fellowship from CNPq(Proc#308702/2019–0)。
文摘Background:Patterns of rarity can be explained by reproductive rates,levels of endemism,and habitat specificity,and knowledge on these parameters is important to understand the levels of vulnerability of each species and to formulate conservation strategies.Here,we studied nest-site selection and breeding biology of the Atlantic Royal Flycatcher(Onychorhynchus swainsoni),a poorly known vulnerable bird endemic to the Brazilian Atlantic Forest.Methods:We addressed nest site selection in three different levels:first,we searched for nests near and far from water to investigate whether birds could select water proximities to construct nests;second,we examined if they could select certain streams in detriment of others,and we analyzed the characteristics of used and non-used streams,and third,in streams in which nests were found,we addressed nest site selectivity by comparing a number of parameters between nest sites and random sites.Further,we provide information on breeding biology parameters related to annual fecundity.Results:During five breeding seasons,we found 23 nests in a well-preserved forest continuum.All of the nests were constructed above water,and they were found in streams that were about 4 m in width,instead of smaller streams with about 1.5 m in width.Modeling analyses revealed that within the used streams,nests were constructed in sites with lower vegetation density in relation to random points,while stream width,water speed,and canopy cover presented no significant correlation.Atlantic Royal Flycatchers in our study had a 22-day incubation period and 24 to 27-day nestling period.Overall nest survival was comparatively high(62%),but clutch size was small(N=2 eggs)and Along the nesting streams,we found an average of 1.62±0.07 breeding pairs/km.Conclusions:These data suggest that nesting habitat specificity and low annual fecundity are among the factors contributing to the rarity of the Atlantic Royal Flycatcher in large forest continuums and to its absence in fragmented environments.It reinforces the importance of large well-preserved forest continuums for the conservation of habitat specialist Atlantic Forest bird species.
基金supported by AREVA(France)the National Natural Science Foundation of China(51101107)
文摘Carbon-manganese steel is often applied in components of pipes in nuclear plant. Ultrasonic fatigue tests following low cycle fatigue （LCF） cycles damaged are used to study the strength of very high cycle fatigure （VHCF）. The comparison of test results of simple VHCF and cumulative fatigue （LCF plus VHCF） shows that LCF load influences the following VHCF strength. Continuum damage mechanics model is extended to VHCF region.
基金National Natural Science Foundation of China(Nos.11775062 and 61601419)the Key Laboratory Foundation of National Key Laboratory of Electromagnetic Environment(No.614240319010303).
文摘The electron kinetic model for investigating the transport and ionization rate coefficients of argon glow discharge dusty plasma is developed from the Boltzmann equation.Both of the electron-neutral and electron-dust collisions are considered as collision terms in the kinetic equation.The kinetic equation is simplified by employing the local approximation and nonlocal approach under the same discharge conditions,and the corresponding simplified kinetic equations are known as local and nonlocal kinetic equations respectively.Then the electron energy distribution function(EEDF)is obtained by numerically solving the local and nonlocal kinetic equations and the dust charging equations simultaneously.Based on the obtained EEDFs,the effective electron temperature,electron mobility,electron diffusion coefficient and ionization rate coefficient are calculated for different discharge conditions.It is shown that the EEDFs calculated from the local kinetic model clearly differ from the nonlocal EEDFs and both the local and nonlocal EEDFs are also clearly different with Maxwellian distributions.The appearance of dust particles results in an obvious decrease of high energy electrons and increase of low energy electrons when axial electric field is low.With the increase of axial electric field,the influence of dust particles on the EEDFs becomes smaller.The electron mobility and diffusion coefficients calculated on the basis of local and nonlocal EEDFs do not differ greatly to the dust-free ones.While,when dust density nd=10^6 cm^?3,the electron mobility increases obviously compared with the dust-free results at low axial electric field and decreases with the increasing axial electric field until they are close to the dust-free ones.Meanwhile,electron diffusion coefficients for dusty case become smaller and decrease with the increasing axial electric field.The ionization rate coefficients decrease when dust particles are introduced and they approach the dust-free results gradually with the increasing axial electric field.
基金supported by the Stable-Support Scientific Project of China Research Institute of Radiowave Propagation(No.132101W07)National Natural Science Foundation of China(No.12105251)National Key Laboratory Foundation Electromagnetic Environment(Nos.A382101001,A382101002 and A152101731-C02).
文摘A self-consistent fluid model is developed to investigate the radial distributions of dusty plasma parameters in a DC glow discharge,in which the extended fluid approach of plasma particles and the transport equations of dust particles are coupled.The electrical interaction between charged dust particles is considered in the model.The time evolution of radial distributions of dust density,plasma density,the radial component of electric field and the forces acting on dust particles when dust density tends to be stable,are obtained and analyzed under different discharge currents and dust particle radii.It is shown that the dust density structure is determined mainly by the radial electrostatic force,thermophoretic force and ion drag force in the discharge tube,and both discharge current and dust particle radius have an obvious effect on the transport processes of dust particles.The dust particles gather in the central region of the discharge tube for low discharge current and small dust radius,then dust voids are formed and become wider when the discharge current and dust radius increase.The plasma parameters in the dust gathering region are obviously affected by the dust particles due to the charging processes of electrons and ions to the dust surface.
基金supported by National Natural Science Foundation of China(Nos.11965019,42004131 and 42065005).
文摘The electromagnetic pulse excited by the collision between a hypervelocity meteoroid and a spacecraft is studied both numerically and theoretically.It is found that there are two kinds of electromagnetic pulse.The high-frequency electromagnetic pulse may be excited by the sum of all the electric dipoles.Each electron can be considered as an electric dipole.The low-frequency electromagnetic pulse is produced by the Langmuir oscillation of electrons.The energy flux density and the duration time of the excited low-frequency electromagnetic pulse by the meteoroid are also studied in the present paper.It is shown that the energy flux density increases as either the impact speed or the mass of the meteoroid increases.It is also shown that the duration time decreases as both the impact speed and the mass of the meteoroid increase.By measuring the strength and the duration time of the electromagnetic pulse excited by the collision between the hypervelocity meteoroid and spacecraft,we can estimate the speed and the mass of the hypervelocity meteoroid,which will be helpful in space flight and space exploration.
基金the National Natural Science Foundation of China(NSFC)with grant No.61601419.
文摘This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust charging process and magnetic field.We discuss the dielectric permittivity of dusty plasma in several cases,such as high frequency approximation,parallel propagation in MF/HF band,and effects of plasma movement.Finally,the expressions are employed to study the phenomenon of radar echoes from the polar summer mesosphere.We report that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω–4 and produces a number density of charged dust that agrees with measurements of mesopheric radar echoes.
文摘The case describes the situation of a Brazilian accounting courses in undergraduate programmes middle-class family, as an alternative to teach introductory In its solution, it was used an accounting system, adapted to the needs of register, control, and information of the family equity, through the application of the content of introductory accounting. The authors aim to offer a didactic and playful alternative for the teaching of introductory accounting in undergraduation courses, such as business management, accountancy, economy, and others in which this course is offered. The aim is to show the integration of accounting contents offered in the course, applied to the most common and nearest experience of freshmen in their first year during the undergraduate program： the family. The case can be solved in two phases： In the first, during a class of up to 100 minutes, the professor develops six activities, culminating in the students answering up to four suggested questions; in the second, whose application is left to the professor, in another class further ahead, is numerical.
文摘This report describes a 58 -year -old patient with a giant unruptured asympt omatic aneurysmof right valsava sinus, as well as the significant contribution o f magnetic resonance imaging in diagnosis of this cardiovascular disorder and id entification of its relationship with surrounding thoracic organs.
基金The authors are extremely grateful to FAPESP-project JP 2009/00855-0,CAPES and PPGCM-UFSCar Program.
文摘Crosslinking is one of the most commonly reactions used to improve the physical properties of cellulose derivatives. Cellulose Acetate Propionate (CAP) is a commercial ester obtained as a cellulose derivative and it can be used as basis for the synthesis of crosslinked chains as described in this work. Typical used crosslinkers are di-functional compounds, such as dianhydrides or diisocyanate. The formation of polymeric 3D structures as described in this work occurs typically by the reaction of the linear chains bearing free OH groups with crosslinking agents such as dianhydrides. These reactions are used to make a very absorbent material, typically a gel. The syntheses were performed in homogeneous medium with acetate propionate in a very dry atmosphere by employing PMDA (Pyromellitic Dianhydride) and BTDA (3,3’, 4,4’ Benzophenone Tetracarboxylated Dianhydride) as crosslinking agents in a reflux system. TGA analysis has shown the different thermal stability of the gels when compared with CAP. Typical TGA curves have demonstrated the lower stability of the crosslinked chains when compared to CAP as consequence of esther linkages formed in the gels structures. The Mc, which is the value for the molar mass between crosslinkings points in 3D structure, was determined according to Flory-Rehner theory. This important parameter has demonstrated greater reactivity of PMDA in comparison with the BTDA in the reactions conditions’ employed in this work.
基金supported by the National Natural Science Foundation of China(Grant Nos.62301193,62401178,62171165,and U23B2014)the China Postdoctoral Science Foundation(Grant No.2022M710944)+3 种基金postdoctoral fellowships in Heilongjiang Province(Grant No.LBH-Z22017)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2023QNRC001)the Open Foundation of State Key Laboratory of Millimeter Waves(Grant No.K202505)the National Key Laboratory of Laser Spatial Information Foundation(Grant No.LSI2025ZZKY05).
文摘Spin-orbital interaction characterizes the momentum coupling between polarization and spatial behaviors of electromagnetic waves.The corresponding transition phenomena have been recently manifested by geometric phase metasurfaces,which provide compact and intuitive platforms to replace traditional optical waveplate cascading systems.Nevertheless,metasurfaces based on geometric phase can only impose two opposite modes of orbital angular momentum(OAM)in conjugate spin channels.Although cross-talks among adjacent channels can be exhaustedly minimized,the purity and efficiency of spin-orbital transitions would still be impacted by the coexisting conjugate coupling.Here,we exploit a metasurface with non-orthogonal eigen formalism to achieve the channel-locked spin-orbital transitions,where the output spin state can be constantly fixed while at the same time imposed with versatile modes of OAM with high purity and efficiency.Besides,the robustness of the channel-locked spin-orbital transition is also demonstrated under full polarization illuminations.Such results provide a scheme for full-Stokes beam generation and high-performance meta-polarizer design,which shows the potential of reconfigurable polarization control in wireless communication systems.
基金supported by the National Natural Science Foundation of China(nos.61975163,62275215,62435015,62171165,U23B2014,and U21A6003)Key Core Technology Research Project for Strategic Industry Chains of Xi’an Science and Technology Bureau(23LLRH0057)+2 种基金Key Research and Development Program of Shaanxi Province(2023GXLH-038)Youth Innovation Team of Shaanxi Universities(21JP084)the Doctoral Dissertation Innovation Fund of Xi’an University of Technology(109-252072301).
文摘In recent years,important progress has been made in the field of biosensing and wireless communications by using metamaterials and metasurfaces.These technologies enable efficient manipulation of electromagnetic waves through judiciously designed subwavelength structural units.This review begins by focusing on the design and optimization of terahertz metasurface sensors,emphasizing their unique advantages in biomedical diagnostics.It explores key technical challenges,such as material selection,device integration,and development of robust sensor for surface-specific modifications.Furthermore,the review discusses how metasurfaces,particularly as reconfigurable intelligent surfaces,dynamically modulate electromagnetic wave propagation in the microwave communications domain to enhance signal quality,improve communication efficiency,and showcase their potential in 5G and future 6G technologies.Finally,a comprehensive overview is provided regarding the challenges and future research directions for metamaterial and metasurface technologies in both biosensing and wireless communications,with the ultimate goal of promoting their applications in point-of-care devices and efficient communication systems.
基金the support from National Natural Science Foundation of China(No.61771172)Open Project of Guangxi Key Laboratory of Wireless Wideband Communication and Signal ProcessingNatural Science Foundation of Heilongjiang Province(No.YQ2020F002)。
文摘A general method to realize arbitrary dual-band independent phase control is proposed and demonstrated in this paper.A double-layered C-shape reflective meta-atom is designed to realize independent phase control with high efficiency.As a proof of concept,we propose two functional metasurfaces in the microwave region;the first metasurface performs beam steering in different directions,and the second metasurface generates achromatic beam steering at two distinct frequencies.Both simulation and measurement results agree well with the theoretical pre-setting.The maximum measured efficiency is 88.7%and 92.3%at 6.8 GHz and 8.0 GHz,respectively,for one metasurface,and 91.0%and 89.8%at 6.9 GHz and8.6 GHz,respectively,for the other.
基金National Natural Science Foundation of China(No.61701141,61731010)National Research Foundation,Prime Minister’s Office,Singapore(CRP award NRFCRP15–2015-03).
文摘Fourier transform, mapping the information in one domain to its reciprocal space, isof fundamental significance in real-time and parallel processing of massive data forsound and image manipulation. As a powerful platform of high-efficiency wavecontrol, Huygens’ metasurface may offer to bridge the electromagnetic signalprocessing and analog Fourier transform at the hardware level and with remarkablyimproved performance. We here demonstrate a Huygens’ metasurface hologram,where the image pattern can be self-rotated or projected in free space bymodulating the phase distribution based on the rotational invariance, time-shiftingand scaling properties of Fourier transform. Our proof-of-concept experiment showshigh-efficiency imaging operation in accordance with theoretical predictions,validating the proposed scheme as an ideal way to perform largely parallel spatialdomainmathematical operations in the analog domain using electromagnetic fields.
基金supported by Natural Science Foundation of Heilongjiang Province(YQ2021F004)National Natural Science Foundation of China(Nos.61871152 and 62171153).
文摘In this paper, a novel strategy based on a metasurface composed of simple and compactunit cells to achieve ultra-high-speed trigonometric operations under specificinput values is theoretically and experimentally demonstrated. An electromagneticwave (EM)-based optical diffractive neural network with only one hidden layer isphysically built to perform four trigonometric operations (sine, cosine, tangent, andcotangent functions). Under the unique composite input mode strategy, the designedoptical trigonometric operator responds to incident light source modes that representdifferent trigonometric operations and input values (within one period), and generatescorrect and clear calculated results in the output layer. Such a wave-based operationis implemented with specific input values, and the proposed concept work may offerbreakthrough inspiration to achieve integrable optical computing devices and photonicsignal processors with ultra-fast running speeds.
