This article introduces the design theory of ceramic waveguide filter and proposes a new type of negative coupling structure with a conical throughhole,which has fine-adjustment of negative coupling without significan...This article introduces the design theory of ceramic waveguide filter and proposes a new type of negative coupling structure with a conical throughhole,which has fine-adjustment of negative coupling without significantly increasing the insertion loss of the filter.Based on this,the article proposes an eightcavity ceramic waveguide filter design for 5G base stations.It also presents a detailed discussion on the influence of the cross-coupling slot lengths L2 and L4 on the transmission zeros positions during the filter optimization process and the relevant change rules.For the proposed optimized filter,the observed performance indicators include the center frequency of 3.5 GHz,working bandwidth of 200 MHz,an insertion loss of≤2.0 dB,return loss of≥19 dB,and out-of-band nearend suppression and out-of-band far-end suppression of≥39 dB and≥63 dB,respectively.The test performance results obtained for the sample,with structural parameters as per the simulation model,were in good agreement with the simulation results.展开更多
In this paper,we propose the decoupling technique of patch antenna array by suppressing near-field magnetic coupling(NFMC) using magnetic metamaterials.To this end,a highly-integrated magnetic metamaterials,the subs...In this paper,we propose the decoupling technique of patch antenna array by suppressing near-field magnetic coupling(NFMC) using magnetic metamaterials.To this end,a highly-integrated magnetic metamaterials,the substrate-integrated split-ring resonator(SI-SRR),is firstly proposed to achieve negative permeability at the antenna operating frequency.By integrating SI-SRR in between two closely spaced antennas,magnetic fields are blocked in the shared substrate due to negative permeability of SI-SRR,reducing NFMC between the two antennas.To verify the technique,a prototype was fabricated and measured.The measured results demonstrated that the isolation can be enhanced by more than 17 dB even when the gap between the two patch antennas is only about 0.067 A.Due to high integration,this technique provides an effective alternative to high-isolation antenna array.展开更多
A series of model experiments of bucket foundations concerning suction installation and negative pressure consolidation in saturated silt were carried out in a cube steel bin at Tianjin University. The experimental re...A series of model experiments of bucket foundations concerning suction installation and negative pressure consolidation in saturated silt were carried out in a cube steel bin at Tianjin University. The experimental results show that the silt inside the bucket has been strengthened by negative pressure, and the strengthening effect decreases with the increase of the distance from the bucket. A three-dimensional numerical model of the experiments was built by means of finite element software ABAQUS with fluid-solid coupling method. The results show that the bearing capacity of the silt inside the bucket foundation increases significantly at the former stage of negative pressure consolidation, while the increasing trend slows down over time. The rotation centers of the bucket foundation and the inner soil region tend to be closer to each other based on the consolidation. The bearing capacity of the bucket foundation is improved effectively with the increase of soil strength. The effects of negative pressure consolidation on the bearing capacity of bucket foundation were also illustrated by an actual offshore wind power project case.展开更多
A three-dimensional fluid model is developed to investigate the radio-frequency inductively coupled H2 plasma in a reactor with a rectangular expansion chamber and a cylindrical driver chamber,for neutral beam injecti...A three-dimensional fluid model is developed to investigate the radio-frequency inductively coupled H2 plasma in a reactor with a rectangular expansion chamber and a cylindrical driver chamber,for neutral beam injection system in CFETR.In this model,the electron effective collision frequency and the ion mobility at high E-fields are employed,for accurate simulation of discharges at low pressures(0.3 Pa-2 Pa)and high powers(40 kW-100 kW).The results indicate that when the high E-field ion mobility is taken into account,the electron density is about four times higher than the value in the low E-field case.In addition,the influences of the magnetic field,pressure and power on the electron density and electron temperature are demonstrated.It is found that the electron density and electron temperature in the xz-plane along permanent magnet side become much more asymmetric when magnetic field enhances.However,the plasma parameters in the yz-plane without permanent magnet side are symmetric no matter the magnetic field is applied or not.Besides,the maximum of the electron density first increases and then decreases with magnetic field,while the electron temperature at the bottom of the expansion region first decreases and then almost keeps constant.As the pressure increases from 0.3 Pa to 2 Pa,the electron density becomes higher,with the maximum moving upwards to the driver region,and the symmetry of the electron temperature in the xz-plane becomes much better.As power increases,the electron density rises,whereas the spatial distribution is similar.It can be summarized that the magnetic field and gas pressure have great influence on the symmetry of the plasma parameters,while the power only has little effect.展开更多
Six massive ores in the Jinchuan deposit were dated by Re-Os technique. The Os concentrations and isotopic ratios were determined by N-TIMS, while Re and Pt concentrations were determined by ICP-MS. The samples gave a...Six massive ores in the Jinchuan deposit were dated by Re-Os technique. The Os concentrations and isotopic ratios were determined by N-TIMS, while Re and Pt concentrations were determined by ICP-MS. The samples gave an isochron age of (852±25) Ma with an initial 187Os/188Os ratio of 0.255 ± 0.014. A 7-point Pt-Os isochrone gives an age of (870±38) Ma with an initial 186Os/188Os ratio of 0.119 84±0.000 27.展开更多
The concentrating efficiency of a thermal concentrator can be reflected in the ratio of its interior to exterior temperature gradients,which, however, has an upper limit in existing schemes. Here, we manage to break t...The concentrating efficiency of a thermal concentrator can be reflected in the ratio of its interior to exterior temperature gradients,which, however, has an upper limit in existing schemes. Here, we manage to break this upper limit by considering the couplings of thermal conductivities and improve the concentrating efficiency of thermal concentrators. For this purpose, we first discuss a monolayer scheme with an isotropic thermal conductivity, which can break the upper limit but is still restricted by its geometric configuration. To go further, we explore another degree of freedom by considering the monolayer scheme with an anisotropic thermal conductivity or by adding the second shell with an isotropic thermal conductivity, thereby making the concentrating efficiency completely free from the geometric configuration. Nevertheless, apparent negative thermal conductivities are required, and we resort to external heat sources realizing the same effect without violating the second law of thermodynamics. Finite-element simulations are performed to confirm the theoretical predictions, and experimental suggestions are also provided to improve feasibility. These results may have potential applications for thermal camouflage and provide guidance to other diffusive systems such as static magnetic fields and dc current fields for achieving similar behaviors.展开更多
This paper investigates the synchronization problem for two different complex dynamical Lurie networks, The first one is with constant coupling and the second one is with constant coupling and discrete-delay coupling....This paper investigates the synchronization problem for two different complex dynamical Lurie networks, The first one is with constant coupling and the second one is with constant coupling and discrete-delay coupling. Based on contraction theory and matrix measure properties, some new delay-independent synchronization conditions depending on coupling strength and network topology are proposed. Finally, simulation results are presented to support the theoretical results.展开更多
A planar magnetoinductive (MI) waveguide loaded rectangular microstrip patch antenna is presented and discussed. The MI waveguide consists of two planar metamaterial split squared ring resonators (SSRRs) placed in bet...A planar magnetoinductive (MI) waveguide loaded rectangular microstrip patch antenna is presented and discussed. The MI waveguide consists of two planar metamaterial split squared ring resonators (SSRRs) placed in between two microstrip lines. The backward wave propagation takes place through this structure. The rectangular microstrip patch antenna is magnetically coupled to the MI waveguide. The unloaded rectangular microstrip patch antenna resonates at 37.10 GHz. When loaded with planar MI waveguide, its resonant frequency is reduced to 9.38 GHz with the bandwidth and gain of 44% and 4.16 dBi respectively. In loaded condition, the dimension of antenna is 12.50 mm × 3.70 mm (0.390 λ × 0.115 λ). The appreciable bandwidth is achieved in such a small size antenna. The pass band frequency of MI waveguide is predicted by using the theoretical model of dispersion equation. The effective medium theory is used to verify the metamaterial characteristics of SSRR. The simulated results and theoretical calculations are also presented. The results show that the proposed method can be used to design compact and high bandwidth microstrip patch antennas.展开更多
A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc.After validating the model with the experim...A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc.After validating the model with the experimental results,the influence of the landing gear structure and braking system parameters on gear walk is further investigated.Among the above factors,the slope of the graph for the friction coefficient of the brake disc and the relative velocity of brake stators and rotors is the most influential factor on gear walk instability.Phase trajectory analysis verifies that gear walk occurs when the coupling of multiple factors causes the system to exhibit an equivalent negative damping trend.To consider a more realistic braking case,a back propagation neural network method is employed to describe the nonlinear behavior of the friction coefficient of the brake disc.With the realistic nonlinear model of the friction coefficient,the maximum error in predicting the braking torque is less than 10%and the effect of the brake disc temperature on gear walk is performed.The results reveal that a more negative friction slope may contribute to a more severe unstable gear walk,and reducing the braking pressure is an effective approach to avoid gear walk,which provides help for future braking system design.展开更多
G-protein coupled receptors(GPCRs)are the largest family of druggable targets.In recent years,GPCR structural biology has made great advances,revealing the three-dimensional structures of many GPCRs and their interact...G-protein coupled receptors(GPCRs)are the largest family of druggable targets.In recent years,GPCR structural biology has made great advances,revealing the three-dimensional structures of many GPCRs and their interactions with ligands,proteins,and membrane components,which also have inspired a surge of structure-based drug discovery campaigns.This article provides a comprehensive summary of the currently available structural insights into the allosteric pockets of GPCRs and their regulatory mechanisms governing GPCR conformational changes.Furthermore,this article also presents several structure-inspired studies that utilize both orthosteric and allosteric modulation to discover small molecular modulators targeting GPCRs.The article emphasizes the promising potential of drug discovery targeting GPCR allosteric sites,while acknowledging the challenges arising from the limited structural information regarding the lipids and cholesterols in the membrane.Finally,the article discusses the future prospects of using large-scale or focused compound libraries to discover novel chemotypes,as well as the application of artificial intelligence(AI)in structure-based virtual screening(SBVS)against GPCRs.展开更多
This paper focuses on eliminating the unphysical negative susceptibility which ap- pears when magnetic field is at unsaturated excitation level and reduces from extremity of the hysteresis loop in one-dimension couple...This paper focuses on eliminating the unphysical negative susceptibility which ap- pears when magnetic field is at unsaturated excitation level and reduces from extremity of the hysteresis loop in one-dimension coupled hysteresis model. The domain flexing function c (H) is used to replace the domain flexing constant c in one-dimension coupled hysteresis model. The fea- sibility and rationality of proposed modification are convinced by comparing the magnetization and magnetostriction curves with experimental data and another typical modification results. The effects of pre-stress and temperature on magnetic-elastic-thermal coupling property and hysteresis behavior are investigated.展开更多
Surface modification is a fascinating way to improve the compounding effect between inorganic fillers and polymers.In this study,zirconium tungsten phosphate(ZWP) with negative thermal expansion was surface modified b...Surface modification is a fascinating way to improve the compounding effect between inorganic fillers and polymers.In this study,zirconium tungsten phosphate(ZWP) with negative thermal expansion was surface modified by silane coupling agent 3-(Trimethoxysilyl)propyl methacrylate.The effects of surface modification and the modification mechanism were analyzed in detail by X-ray diffractometer,scanning electron microscopy,Fourier transform infrared spectroscopy and thermal mechanical analysis.The surface modification could effectively reduce the thermal expansion properties of the composite.When the added amount of 3-methacryloxypropyl trimethoxysilaneSilane(trade name:KH570) is 0.50 wt%,the thermal expansion coefficient of ZWP/Aromatic polyimide composite decreased by 9.76%.The surface modification also can effectively improve the dielectric performance of aromatic polyimides.The present work provides one new way to improve the thermal expansion behavior of composites.展开更多
In this paper, we study the count of head runs up to a fixed time in a two-state stationary Markov chain. We prove that in total variance distance, the negative binomial, Poisson and binomial distributions are appropr...In this paper, we study the count of head runs up to a fixed time in a two-state stationary Markov chain. We prove that in total variance distance, the negative binomial, Poisson and binomial distributions are appropriate approximations according to the relation of the variance and mean of the count, generalizing earlier results in previous literatures. The proof is based on Stein's method and coupling.展开更多
We propose the generation of photonic EPR state from quadratic waveguide array. Both the propagation constant and the nonlinearity in the array are designed to possess a periodical modulation along the propagation dir...We propose the generation of photonic EPR state from quadratic waveguide array. Both the propagation constant and the nonlinearity in the array are designed to possess a periodical modulation along the propagation direction.This ensures that the photon pairs can be generated efficiently through the quasi-phase-matching spontaneous parametric down conversion by holding the spatial EPR entanglement in the fashion of correlated position and anticorrelated momentum. The Schmidt number which denotes the degree of EPR entanglement is calculated and it can approach a high value when the number of illuminated waveguide channels and the length of the waveguide array are properly chosen. These results suggest the quadratic waveguide array as a compact platform for engineering photonic quantum states in a high-dimensional Hilbert space.展开更多
基金supported by the National Natural Science Fund Joint Fund Project(No.U21B2068)the Major Science and Technology Innovation Project of WenZhou(No.ZG2021014).
文摘This article introduces the design theory of ceramic waveguide filter and proposes a new type of negative coupling structure with a conical throughhole,which has fine-adjustment of negative coupling without significantly increasing the insertion loss of the filter.Based on this,the article proposes an eightcavity ceramic waveguide filter design for 5G base stations.It also presents a detailed discussion on the influence of the cross-coupling slot lengths L2 and L4 on the transmission zeros positions during the filter optimization process and the relevant change rules.For the proposed optimized filter,the observed performance indicators include the center frequency of 3.5 GHz,working bandwidth of 200 MHz,an insertion loss of≤2.0 dB,return loss of≥19 dB,and out-of-band nearend suppression and out-of-band far-end suppression of≥39 dB and≥63 dB,respectively.The test performance results obtained for the sample,with structural parameters as per the simulation model,were in good agreement with the simulation results.
基金Project supported in part by the National Natural Science Foundation of China(Grant Nos.61331005,61471388,61501503,61501502,61501497,51575524,61302023,and 11304393)the Natural Science Foundation of Shaanxi Province,China(Grant Nos.2015JM6300 and 2015JM6277)
文摘In this paper,we propose the decoupling technique of patch antenna array by suppressing near-field magnetic coupling(NFMC) using magnetic metamaterials.To this end,a highly-integrated magnetic metamaterials,the substrate-integrated split-ring resonator(SI-SRR),is firstly proposed to achieve negative permeability at the antenna operating frequency.By integrating SI-SRR in between two closely spaced antennas,magnetic fields are blocked in the shared substrate due to negative permeability of SI-SRR,reducing NFMC between the two antennas.To verify the technique,a prototype was fabricated and measured.The measured results demonstrated that the isolation can be enhanced by more than 17 dB even when the gap between the two patch antennas is only about 0.067 A.Due to high integration,this technique provides an effective alternative to high-isolation antenna array.
基金Supported by the National Natural Science Foundation of China(No.51379142)International S&T Cooperation Program of China(No.2012DFA70490)Tianjin Municipal Natural Science Foundation(No.13JCYBJC19100 and No.13JCQNJC06900)
文摘A series of model experiments of bucket foundations concerning suction installation and negative pressure consolidation in saturated silt were carried out in a cube steel bin at Tianjin University. The experimental results show that the silt inside the bucket has been strengthened by negative pressure, and the strengthening effect decreases with the increase of the distance from the bucket. A three-dimensional numerical model of the experiments was built by means of finite element software ABAQUS with fluid-solid coupling method. The results show that the bearing capacity of the silt inside the bucket foundation increases significantly at the former stage of negative pressure consolidation, while the increasing trend slows down over time. The rotation centers of the bucket foundation and the inner soil region tend to be closer to each other based on the consolidation. The bearing capacity of the bucket foundation is improved effectively with the increase of soil strength. The effects of negative pressure consolidation on the bearing capacity of bucket foundation were also illustrated by an actual offshore wind power project case.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFE0300106)the National Natural Science Foundation of China(Grant No.12075049)the Fundamental Research Funds for the Central Universities,China(Grant Nos.DUT20LAB201 and DUT21LAB110).
文摘A three-dimensional fluid model is developed to investigate the radio-frequency inductively coupled H2 plasma in a reactor with a rectangular expansion chamber and a cylindrical driver chamber,for neutral beam injection system in CFETR.In this model,the electron effective collision frequency and the ion mobility at high E-fields are employed,for accurate simulation of discharges at low pressures(0.3 Pa-2 Pa)and high powers(40 kW-100 kW).The results indicate that when the high E-field ion mobility is taken into account,the electron density is about four times higher than the value in the low E-field case.In addition,the influences of the magnetic field,pressure and power on the electron density and electron temperature are demonstrated.It is found that the electron density and electron temperature in the xz-plane along permanent magnet side become much more asymmetric when magnetic field enhances.However,the plasma parameters in the yz-plane without permanent magnet side are symmetric no matter the magnetic field is applied or not.Besides,the maximum of the electron density first increases and then decreases with magnetic field,while the electron temperature at the bottom of the expansion region first decreases and then almost keeps constant.As the pressure increases from 0.3 Pa to 2 Pa,the electron density becomes higher,with the maximum moving upwards to the driver region,and the symmetry of the electron temperature in the xz-plane becomes much better.As power increases,the electron density rises,whereas the spatial distribution is similar.It can be summarized that the magnetic field and gas pressure have great influence on the symmetry of the plasma parameters,while the power only has little effect.
文摘Six massive ores in the Jinchuan deposit were dated by Re-Os technique. The Os concentrations and isotopic ratios were determined by N-TIMS, while Re and Pt concentrations were determined by ICP-MS. The samples gave an isochron age of (852±25) Ma with an initial 187Os/188Os ratio of 0.255 ± 0.014. A 7-point Pt-Os isochrone gives an age of (870±38) Ma with an initial 186Os/188Os ratio of 0.119 84±0.000 27.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11725521, and 12035004)the Science and Technology Commission of Shanghai Municipality (Grant No. 20JC1414700)。
文摘The concentrating efficiency of a thermal concentrator can be reflected in the ratio of its interior to exterior temperature gradients,which, however, has an upper limit in existing schemes. Here, we manage to break this upper limit by considering the couplings of thermal conductivities and improve the concentrating efficiency of thermal concentrators. For this purpose, we first discuss a monolayer scheme with an isotropic thermal conductivity, which can break the upper limit but is still restricted by its geometric configuration. To go further, we explore another degree of freedom by considering the monolayer scheme with an anisotropic thermal conductivity or by adding the second shell with an isotropic thermal conductivity, thereby making the concentrating efficiency completely free from the geometric configuration. Nevertheless, apparent negative thermal conductivities are required, and we resort to external heat sources realizing the same effect without violating the second law of thermodynamics. Finite-element simulations are performed to confirm the theoretical predictions, and experimental suggestions are also provided to improve feasibility. These results may have potential applications for thermal camouflage and provide guidance to other diffusive systems such as static magnetic fields and dc current fields for achieving similar behaviors.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.61174021 and 61104155)the Fundamental Research Funds for the Central Universities (Grant No.JUDCF12033)+3 种基金the Jiangsu Innovation Program for Graduates (Grant No.CXZZ12 0742)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)the Fundamental Research Funds for the Central Universities (Grant No.JUSRP51322B)the 111 Project (Grant No.B12018)
文摘This paper investigates the synchronization problem for two different complex dynamical Lurie networks, The first one is with constant coupling and the second one is with constant coupling and discrete-delay coupling. Based on contraction theory and matrix measure properties, some new delay-independent synchronization conditions depending on coupling strength and network topology are proposed. Finally, simulation results are presented to support the theoretical results.
文摘A planar magnetoinductive (MI) waveguide loaded rectangular microstrip patch antenna is presented and discussed. The MI waveguide consists of two planar metamaterial split squared ring resonators (SSRRs) placed in between two microstrip lines. The backward wave propagation takes place through this structure. The rectangular microstrip patch antenna is magnetically coupled to the MI waveguide. The unloaded rectangular microstrip patch antenna resonates at 37.10 GHz. When loaded with planar MI waveguide, its resonant frequency is reduced to 9.38 GHz with the bandwidth and gain of 44% and 4.16 dBi respectively. In loaded condition, the dimension of antenna is 12.50 mm × 3.70 mm (0.390 λ × 0.115 λ). The appreciable bandwidth is achieved in such a small size antenna. The pass band frequency of MI waveguide is predicted by using the theoretical model of dispersion equation. The effective medium theory is used to verify the metamaterial characteristics of SSRR. The simulated results and theoretical calculations are also presented. The results show that the proposed method can be used to design compact and high bandwidth microstrip patch antennas.
基金the National Natural Science Foundation of China(No.11872312)the Program of Introducing Talents of Discipline to Universities,China(No.BP0719007)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2022002)。
文摘A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc.After validating the model with the experimental results,the influence of the landing gear structure and braking system parameters on gear walk is further investigated.Among the above factors,the slope of the graph for the friction coefficient of the brake disc and the relative velocity of brake stators and rotors is the most influential factor on gear walk instability.Phase trajectory analysis verifies that gear walk occurs when the coupling of multiple factors causes the system to exhibit an equivalent negative damping trend.To consider a more realistic braking case,a back propagation neural network method is employed to describe the nonlinear behavior of the friction coefficient of the brake disc.With the realistic nonlinear model of the friction coefficient,the maximum error in predicting the braking torque is less than 10%and the effect of the brake disc temperature on gear walk is performed.The results reveal that a more negative friction slope may contribute to a more severe unstable gear walk,and reducing the braking pressure is an effective approach to avoid gear walk,which provides help for future braking system design.
基金This work is supported by Beijing Municipal Science&Technology Commission(Z201100005320012 to N.H.)and Tsinghua University.
文摘G-protein coupled receptors(GPCRs)are the largest family of druggable targets.In recent years,GPCR structural biology has made great advances,revealing the three-dimensional structures of many GPCRs and their interactions with ligands,proteins,and membrane components,which also have inspired a surge of structure-based drug discovery campaigns.This article provides a comprehensive summary of the currently available structural insights into the allosteric pockets of GPCRs and their regulatory mechanisms governing GPCR conformational changes.Furthermore,this article also presents several structure-inspired studies that utilize both orthosteric and allosteric modulation to discover small molecular modulators targeting GPCRs.The article emphasizes the promising potential of drug discovery targeting GPCR allosteric sites,while acknowledging the challenges arising from the limited structural information regarding the lipids and cholesterols in the membrane.Finally,the article discusses the future prospects of using large-scale or focused compound libraries to discover novel chemotypes,as well as the application of artificial intelligence(AI)in structure-based virtual screening(SBVS)against GPCRs.
基金supported by the Fund of Natural Science Foundation of China(Nos.10972094,11032006,11121202 and 11202087)the Fundamental Research Funds for the Central Universities(No.lzujbky-2011-6)Specialized Research Fund for the Doctoral Program of Higher Education(No.20110211120027)
文摘This paper focuses on eliminating the unphysical negative susceptibility which ap- pears when magnetic field is at unsaturated excitation level and reduces from extremity of the hysteresis loop in one-dimension coupled hysteresis model. The domain flexing function c (H) is used to replace the domain flexing constant c in one-dimension coupled hysteresis model. The fea- sibility and rationality of proposed modification are convinced by comparing the magnetization and magnetostriction curves with experimental data and another typical modification results. The effects of pre-stress and temperature on magnetic-elastic-thermal coupling property and hysteresis behavior are investigated.
基金supported by the national science foundation of china (Nos. 22071221, 21905252)the natural science foundation of Henan province (Nos. 182300410192, 212300410086)。
文摘Surface modification is a fascinating way to improve the compounding effect between inorganic fillers and polymers.In this study,zirconium tungsten phosphate(ZWP) with negative thermal expansion was surface modified by silane coupling agent 3-(Trimethoxysilyl)propyl methacrylate.The effects of surface modification and the modification mechanism were analyzed in detail by X-ray diffractometer,scanning electron microscopy,Fourier transform infrared spectroscopy and thermal mechanical analysis.The surface modification could effectively reduce the thermal expansion properties of the composite.When the added amount of 3-methacryloxypropyl trimethoxysilaneSilane(trade name:KH570) is 0.50 wt%,the thermal expansion coefficient of ZWP/Aromatic polyimide composite decreased by 9.76%.The surface modification also can effectively improve the dielectric performance of aromatic polyimides.The present work provides one new way to improve the thermal expansion behavior of composites.
基金supported by National Natural Science Foundation of China (Grant No. 11071021)
文摘In this paper, we study the count of head runs up to a fixed time in a two-state stationary Markov chain. We prove that in total variance distance, the negative binomial, Poisson and binomial distributions are appropriate approximations according to the relation of the variance and mean of the count, generalizing earlier results in previous literatures. The proof is based on Stein's method and coupling.
基金Supported by the State Key Program for Basic Research in China under Grant No.2012CB921802 the National Natural Science Foundations of China under Grant Nos.91321312,11321063 and 11422438
文摘We propose the generation of photonic EPR state from quadratic waveguide array. Both the propagation constant and the nonlinearity in the array are designed to possess a periodical modulation along the propagation direction.This ensures that the photon pairs can be generated efficiently through the quasi-phase-matching spontaneous parametric down conversion by holding the spatial EPR entanglement in the fashion of correlated position and anticorrelated momentum. The Schmidt number which denotes the degree of EPR entanglement is calculated and it can approach a high value when the number of illuminated waveguide channels and the length of the waveguide array are properly chosen. These results suggest the quadratic waveguide array as a compact platform for engineering photonic quantum states in a high-dimensional Hilbert space.