Directional modulation is one of the hot topics in data security researches.To fulfill the requirements of communication security in wireless environment with multiple paths,this study takes into account the factors o...Directional modulation is one of the hot topics in data security researches.To fulfill the requirements of communication security in wireless environment with multiple paths,this study takes into account the factors of reflections and antenna radiation pattern for directional modulation.Unlike other previous works,a novel multiple-reflection model,which is more realistic and complex than simplified two-ray reflection models,is proposed based on two reflectors.Another focus is a quantum genetic algorithm applied to optimize antenna excitation in a phased directional modulation antenna array.The quantum approach has strengths in convergence speed and the globe searching ability for the complicated model with the large-size antenna array and multiple paths.From this,a phased directional modulation transmission system can be optimized as regards communication safety and improve performance based on the constraint of the pattern of the antenna array.Our work can spur applications of the quantum evolutionary algorithm in directional modulation technology,which is also studied.展开更多
In this work,we carried out both theoretical calculation and experimental studies to reveal the contribution of hollow geometry to the light utilization efficiency of the TiO_2 photocatalysts in diluted aqueous soluti...In this work,we carried out both theoretical calculation and experimental studies to reveal the contribution of hollow geometry to the light utilization efficiency of the TiO_2 photocatalysts in diluted aqueous solution.It is found that the single or multi-shelled hollow structures do not induce significant multiple reflections within the shells as widely believed in previous reports,and therefore the geometric factor has minimal contribution to the improvement of the light utilization efficiency of the photocatalyst.To design TiO_2 photocatalysts with higher activity,it is more appropriate to focus on the improvement of the crystallinity,diffusion,surface area,and dispersity of the catalysts,rather than their geometric shapes.展开更多
In this paper we discuss the inverse scattering algorithm for predicting internal multiple reflections(reverberation artefacts),focusing our attention on the construction mechanisms.Roughly speaking,the algorithm comb...In this paper we discuss the inverse scattering algorithm for predicting internal multiple reflections(reverberation artefacts),focusing our attention on the construction mechanisms.Roughly speaking,the algorithm combines amplitude and phase information of three different arrivals(sub-events)in the data set to predict one multiple reflection.The three events are conditioned by a certain relation which requires that their pseudo-depths,defined as the depths of their turning points relative to the constant background velocity,satisfy a lower-higher-lower relationship.This implicitly assumes a pseudo-depth monotonicity condition,i.e.,the relation between the actual depths and the pseudo-depths of any two sub-events is the same.We study this relation in pseudo-depth and show that it is directly connected with a similar relation between the vertical or intercept times of the sub-events.The paper also provides the first multidimensional analysis of the algorithm(for a vertically varying acoustic model)with analytical data.We show that the construction of internal multiples is performed in the plane waves domain and,as a consequence,the internal multiples with headwaves sub-events are also predicted by the algorithm.Furthermore we analyze the differences between the time monotonicity condition in vertical or intercept time and total travel time and show a 2D example which satisfies the former but not the latter.Finally we discuss one case in which the monotonicity condition is not satisfied by the sub-events of an internal multiple and discuss ways of lowering these restrictions and of expanding the algorithm to address these types of multiples.展开更多
We investigate the boundary effect of quark–gluon plasma(QGP)droplets and the self-similarity effect of hadrons on QGP–hadron phase transition.In intermediate-or low-energy collisions,when the transverse momentum is...We investigate the boundary effect of quark–gluon plasma(QGP)droplets and the self-similarity effect of hadrons on QGP–hadron phase transition.In intermediate-or low-energy collisions,when the transverse momentum is below quantum chromodynamics(QCD)scale,QGP cannot be produced.However,if the transverse momentum changes to a relatively large value,a smallscale QGP droplet is produced.The modified MIT bag model with the multiple reflection expansion method is employed to study the QGP droplet with the curved boundary effect.It is found that the energy density,entropy density and pressure of QGP with the influence are smaller than those without the influence.In the hadron phase,we propose the two-body fractal model(TBFM)to study the self-similarity structure,arising from resonance,quantum correlation and interaction effects.It is observed that the energy density,entropy density and pressure increase due to the self-similarity structure.We calculate the transverse momentum spectra of pions with the self-similarity structure influence,which show good agreement with experimental data.Considering both boundary effect and self-similarity structure influence,our model predicts an increase in the transition temperature compared to the scenarios without these two effects in the High Intensity heavy-ion Accelerator Facility(HIAF)energy region,2.2 GeV to approximately 4.5 GeV.展开更多
The reflection and transmission of elastic waves through a couple-stress elastic slab that is sandwiched between two couple-stress elastic half-spaces are studied in this paper. Because of the couple-stress effects, t...The reflection and transmission of elastic waves through a couple-stress elastic slab that is sandwiched between two couple-stress elastic half-spaces are studied in this paper. Because of the couple-stress effects, there are three types of elastic waves in the couple-stress elastic solid, two of which are dispersive. The interface conditions between two couple-stress solids involve the surface couple and rotation apart from the surface traction and displacement. The nontraditional interface conditions between the slab and two solid half-spaces are used to obtain the linear algebraic equation sets from which the amplitude ratios of reflection and transmission waves to the incident wave can be determined. Then,the energy fluxes carried by the various reflection and transmission waves are calculated numerically and the normal energy flux conservation is used to validate the numerical results. The special case, couple-stress elastic slab sandwiched by the classical elastic half-spaces, is also studied and compared with the situation that the classical elastic slab sandwiched by the classical elastic half-spaces. Incident longitudinal wave(P wave) and incident transverse wave(SV wave) are both considered. The influences of the couplestress are mainly discussed based on the numerical results.It is found that the couple-stress mainly influences the transverse modes of elastic waves.展开更多
The North China Craton(NCC)is a key region to study the destruction of the ancient craton.Two groups of phases(denoted as"Pw1"and"Pw2"),which are parallel to the PmP phase reflected from the Moho d...The North China Craton(NCC)is a key region to study the destruction of the ancient craton.Two groups of phases(denoted as"Pw1"and"Pw2"),which are parallel to the PmP phase reflected from the Moho discontinuity and the PLP phase reflected from the Lithosphere and Asthenosphere Boundary(LAB)respectively,are found on the record section of the Rongcheng-XinzhouAlxa long-range deep seismic sounding profile.The nature of the two phases is still unclear,although they are clearly observable and reverberant.In this paper,we use travel time inversion and amplitude forward modelling to fit the reflected and refracted phases in the lithosphere.The results show:(1)the Pw1 is a multiple reflected phase which is successively reflected by the crystalline basement,the surface,the Moho and then finally received on the surface;(2)the Pw2 phase is also a multiple reflected phase successively reflected by the crystalline basement,the surface,the LAB interface and then received on the surface.We conclude that the significant velocity difference between the thick sedimentary cover and the crystalline basement in the North China rifted basin may be the main reason for generating the multiple reflections.Furthermore,the two multiple reflections provide potent constraints on the lithospheric velocity model,and constitute seismological evidence for the lithospheric thinning in the eastern NCC.展开更多
Due to the fact that traditional ray field tracking approaches require a large number of geometrical optical（GO） ray tubes,they are very inefficient in many practical applications.An improved ray model scheme for a ...Due to the fact that traditional ray field tracking approaches require a large number of geometrical optical（GO） ray tubes,they are very inefficient in many practical applications.An improved ray model scheme for a complex source beam（CSB） tracking technique is proposed in this paper.The source field can be expressed by a superposition of CSBs,then every CSB basis function has a Gaussian-type amplitude distribution and is suitable for replacing a GO ray tube in the ray tracing approach.The complex phase matching technique is adopted to find the reflected beam in the reflection point where local approximation is used to represent the curved surface in its neighborhood.A new solution to multiple reflections using the conventional right-handed reflected system is used to track the field easily.Numerical results show the accuracy of the proposed method.展开更多
Purpose We are building an MRTOF-MS(multi-reflection time-of-flight mass spectrometer)for isobaric separation for the Lanzhou Penning Trap.The potentials applied on the electrodes of our MRTOF mass analyzer operating ...Purpose We are building an MRTOF-MS(multi-reflection time-of-flight mass spectrometer)for isobaric separation for the Lanzhou Penning Trap.The potentials applied on the electrodes of our MRTOF mass analyzer operating in in-trap-lift mode have to be optimized to achieve a very high mass resolving power.Methods Our method to design and optimize an MRTOF mass analyzer has been updated to introduce constraints on the potentials,and this method now can be used to optimize the parameters of MRTOF-MS both operating in mirror-switching mode and in in-trap-lift mode.By using this method,the optimal potential parameters of the electrodes have been obtained for our MRTOF mass analyzer operating in the in-trap-lift mode.Results and conclusion With a beam size of 2.8 mm diameter and an initial average ion kinetic energy of 1500 eV,the maximal mass resolving power has been achieved to be 3.2×10^(4) with a total TOF of 7.0 ms for an ion species of ^(40)Ar^(1+).It can reach up to 5.6×10^(4) for a beam size of 0.3 mm diameter.The simulation shows that the inaccuracy of the potentials applied on the outermost mirror electrodes M1–M2 must be less than 50 ppm or preferably 20 ppm.展开更多
基金This work was supported by the NSFC(Grant Nos.61671087,61962009 and 61003287)the Fok Ying Tong Education Foundation(Grant No.131067)+3 种基金the Major Scientific and Technological Special Project of Guizhou Province(Grant No.20183001)the Foundation of State Key Laboratory of Public Big Data(Grant No.2018BDKFJJ018)the High-quality and Cutting-edge Disciplines Construction Project for Universities in Beijing(Internet Information,Communication University of China)the Fundamental Research Funds for the Central Universities(Nos.2019XD-A02,328201915,328201917 and 328201916).
文摘Directional modulation is one of the hot topics in data security researches.To fulfill the requirements of communication security in wireless environment with multiple paths,this study takes into account the factors of reflections and antenna radiation pattern for directional modulation.Unlike other previous works,a novel multiple-reflection model,which is more realistic and complex than simplified two-ray reflection models,is proposed based on two reflectors.Another focus is a quantum genetic algorithm applied to optimize antenna excitation in a phased directional modulation antenna array.The quantum approach has strengths in convergence speed and the globe searching ability for the complicated model with the large-size antenna array and multiple paths.From this,a phased directional modulation transmission system can be optimized as regards communication safety and improve performance based on the constraint of the pattern of the antenna array.Our work can spur applications of the quantum evolutionary algorithm in directional modulation technology,which is also studied.
基金support from the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Chemical Sciences,Geosciences,&Biosciences(CSGB)Division(DE-SC0002247)support from the National Natural Science Foundation of China(21501081,21571089,and 21401091)the Fundamental Research Funds for the Central Universities(SWU116010 and lzujbky-2015-19)
文摘In this work,we carried out both theoretical calculation and experimental studies to reveal the contribution of hollow geometry to the light utilization efficiency of the TiO_2 photocatalysts in diluted aqueous solution.It is found that the single or multi-shelled hollow structures do not induce significant multiple reflections within the shells as widely believed in previous reports,and therefore the geometric factor has minimal contribution to the improvement of the light utilization efficiency of the photocatalyst.To design TiO_2 photocatalysts with higher activity,it is more appropriate to focus on the improvement of the crystallinity,diffusion,surface area,and dispersity of the catalysts,rather than their geometric shapes.
基金This work was partially supported by NSF-CMG award number DMS-0327778the DOE Basic Energy Sciences award DE-FG02-05ER15697The support of M-OSRP spon-sors is also gratefully acknowledged.Adriana C.Ramirez is thanked for providing the model in Fig.6.Jon Sheiman,Einar Otnes and Fons ten Kroode are acknowledged for their useful comments and insights on this work.
文摘In this paper we discuss the inverse scattering algorithm for predicting internal multiple reflections(reverberation artefacts),focusing our attention on the construction mechanisms.Roughly speaking,the algorithm combines amplitude and phase information of three different arrivals(sub-events)in the data set to predict one multiple reflection.The three events are conditioned by a certain relation which requires that their pseudo-depths,defined as the depths of their turning points relative to the constant background velocity,satisfy a lower-higher-lower relationship.This implicitly assumes a pseudo-depth monotonicity condition,i.e.,the relation between the actual depths and the pseudo-depths of any two sub-events is the same.We study this relation in pseudo-depth and show that it is directly connected with a similar relation between the vertical or intercept times of the sub-events.The paper also provides the first multidimensional analysis of the algorithm(for a vertically varying acoustic model)with analytical data.We show that the construction of internal multiples is performed in the plane waves domain and,as a consequence,the internal multiples with headwaves sub-events are also predicted by the algorithm.Furthermore we analyze the differences between the time monotonicity condition in vertical or intercept time and total travel time and show a 2D example which satisfies the former but not the latter.Finally we discuss one case in which the monotonicity condition is not satisfied by the sub-events of an internal multiple and discuss ways of lowering these restrictions and of expanding the algorithm to address these types of multiples.
基金supported by the National Natural Science Foundation of China under Grant No.12175031Guangdong Provincial Key Laboratory of Nuclear Science under Grant No.2019B121203010。
文摘We investigate the boundary effect of quark–gluon plasma(QGP)droplets and the self-similarity effect of hadrons on QGP–hadron phase transition.In intermediate-or low-energy collisions,when the transverse momentum is below quantum chromodynamics(QCD)scale,QGP cannot be produced.However,if the transverse momentum changes to a relatively large value,a smallscale QGP droplet is produced.The modified MIT bag model with the multiple reflection expansion method is employed to study the QGP droplet with the curved boundary effect.It is found that the energy density,entropy density and pressure of QGP with the influence are smaller than those without the influence.In the hadron phase,we propose the two-body fractal model(TBFM)to study the self-similarity structure,arising from resonance,quantum correlation and interaction effects.It is observed that the energy density,entropy density and pressure increase due to the self-similarity structure.We calculate the transverse momentum spectra of pions with the self-similarity structure influence,which show good agreement with experimental data.Considering both boundary effect and self-similarity structure influence,our model predicts an increase in the transition temperature compared to the scenarios without these two effects in the High Intensity heavy-ion Accelerator Facility(HIAF)energy region,2.2 GeV to approximately 4.5 GeV.
基金supported by the Fundamental Research Funds for the Central Universities (Grant FRF-BR-15026A)the National Natural Science Foundation of China (Grant 10972029)
文摘The reflection and transmission of elastic waves through a couple-stress elastic slab that is sandwiched between two couple-stress elastic half-spaces are studied in this paper. Because of the couple-stress effects, there are three types of elastic waves in the couple-stress elastic solid, two of which are dispersive. The interface conditions between two couple-stress solids involve the surface couple and rotation apart from the surface traction and displacement. The nontraditional interface conditions between the slab and two solid half-spaces are used to obtain the linear algebraic equation sets from which the amplitude ratios of reflection and transmission waves to the incident wave can be determined. Then,the energy fluxes carried by the various reflection and transmission waves are calculated numerically and the normal energy flux conservation is used to validate the numerical results. The special case, couple-stress elastic slab sandwiched by the classical elastic half-spaces, is also studied and compared with the situation that the classical elastic slab sandwiched by the classical elastic half-spaces. Incident longitudinal wave(P wave) and incident transverse wave(SV wave) are both considered. The influences of the couplestress are mainly discussed based on the numerical results.It is found that the couple-stress mainly influences the transverse modes of elastic waves.
基金This research is financially supported by the National Key Research and Development Program of China(No.2016YFC0600101)National Natural Science Foundation of China(Nos.90814012,41874065 and 41774097)the Doctor fund of Binzhou University(No.2018Y15)。
文摘The North China Craton(NCC)is a key region to study the destruction of the ancient craton.Two groups of phases(denoted as"Pw1"and"Pw2"),which are parallel to the PmP phase reflected from the Moho discontinuity and the PLP phase reflected from the Lithosphere and Asthenosphere Boundary(LAB)respectively,are found on the record section of the Rongcheng-XinzhouAlxa long-range deep seismic sounding profile.The nature of the two phases is still unclear,although they are clearly observable and reverberant.In this paper,we use travel time inversion and amplitude forward modelling to fit the reflected and refracted phases in the lithosphere.The results show:(1)the Pw1 is a multiple reflected phase which is successively reflected by the crystalline basement,the surface,the Moho and then finally received on the surface;(2)the Pw2 phase is also a multiple reflected phase successively reflected by the crystalline basement,the surface,the LAB interface and then received on the surface.We conclude that the significant velocity difference between the thick sedimentary cover and the crystalline basement in the North China rifted basin may be the main reason for generating the multiple reflections.Furthermore,the two multiple reflections provide potent constraints on the lithospheric velocity model,and constitute seismological evidence for the lithospheric thinning in the eastern NCC.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61301056 and 61231001)the Fundamental Research Funds for the Central Universities,China(Grant No.ZYGX2014J012)+2 种基金the Fok Ying Tung Education Foundation,China(Grant No.141062)the Aero-Science Fund,China(Grant No.20142580012)the"111"Project(Grant No.B07046)
文摘Due to the fact that traditional ray field tracking approaches require a large number of geometrical optical（GO） ray tubes,they are very inefficient in many practical applications.An improved ray model scheme for a complex source beam（CSB） tracking technique is proposed in this paper.The source field can be expressed by a superposition of CSBs,then every CSB basis function has a Gaussian-type amplitude distribution and is suitable for replacing a GO ray tube in the ray tracing approach.The complex phase matching technique is adopted to find the reflected beam in the reflection point where local approximation is used to represent the curved surface in its neighborhood.A new solution to multiple reflections using the conventional right-handed reflected system is used to track the field easily.Numerical results show the accuracy of the proposed method.
基金Supported by the National Natural Science Foundation of China(Grant Nos:11675224,11405243,11605268,11735017)the Chinese Academy of Sciences(No.113462KYSB20150026,QYZDJ-SSW-SLH041)the National Basic Research Program of China(973 Program)(No.2013CB834400).
文摘Purpose We are building an MRTOF-MS(multi-reflection time-of-flight mass spectrometer)for isobaric separation for the Lanzhou Penning Trap.The potentials applied on the electrodes of our MRTOF mass analyzer operating in in-trap-lift mode have to be optimized to achieve a very high mass resolving power.Methods Our method to design and optimize an MRTOF mass analyzer has been updated to introduce constraints on the potentials,and this method now can be used to optimize the parameters of MRTOF-MS both operating in mirror-switching mode and in in-trap-lift mode.By using this method,the optimal potential parameters of the electrodes have been obtained for our MRTOF mass analyzer operating in the in-trap-lift mode.Results and conclusion With a beam size of 2.8 mm diameter and an initial average ion kinetic energy of 1500 eV,the maximal mass resolving power has been achieved to be 3.2×10^(4) with a total TOF of 7.0 ms for an ion species of ^(40)Ar^(1+).It can reach up to 5.6×10^(4) for a beam size of 0.3 mm diameter.The simulation shows that the inaccuracy of the potentials applied on the outermost mirror electrodes M1–M2 must be less than 50 ppm or preferably 20 ppm.
