An implementation of high-precision time transfer over a 1839-km field fiber loop back link between two provincial capitals of China,Xi’an and Taiyuan,is reported.Time transfer stabilities of 6.5 ps at averaging time...An implementation of high-precision time transfer over a 1839-km field fiber loop back link between two provincial capitals of China,Xi’an and Taiyuan,is reported.Time transfer stabilities of 6.5 ps at averaging time of 1 s and 4.6 ps at 40000 s were achieved.The uncertainty for the time transfer system was evaluated,showing a budget of 56.2 ps.These results stand for a significant milestone in achieving high-precision time transfer over a field fiber link spanning thousands of kilometers,signifying a record-breaking achievement for the real-field time transfer in both stability and distance,which paves the way for constructing the nationwide high-precision time service via fiber network.展开更多
We establish the Stinespring dilation theorem of the link product of quantum channels in two different ways,discuss the discrimination of quantum channels,and show that the distinguishability can be improved by self-l...We establish the Stinespring dilation theorem of the link product of quantum channels in two different ways,discuss the discrimination of quantum channels,and show that the distinguishability can be improved by self-linking each quantum channel n times as n grows.We also find that the maximum value of Uhlmann's theorem can be achieved for diagonal channels.展开更多
We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase lockin...We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase locking loop in the conventional active phase control scheme,the passive phase noise cancellation is realized by feeding double-trip beat-note frequency to the driver of the acoustic optical modulator at the local site.This passive scheme exhibits fine robustness and reliability,making it suitable for long-distance and noisy fiber links.An optical regeneration station is used in the link for signal amplification and cascaded transmission.The phase noise cancellation and transfer instability of the 972-km link is investigated,and transfer instability of 1.1×10^(-19)at 10^(4)s is achieved.This work provides a promising method for realizing optical frequency distribution over thousands of kilometers by using fiber links.展开更多
Fiber cladding surface plasmon resonance(SPR)sensors have few structures,and a clad SPR sensor based on S-type fiber is proposed in this paper.This new type of fiber cladding SPR sensor was formed by electrofusing an ...Fiber cladding surface plasmon resonance(SPR)sensors have few structures,and a clad SPR sensor based on S-type fiber is proposed in this paper.This new type of fiber cladding SPR sensor was formed by electrofusing an S-shaped structure on the fiber to couple the light in the fiber core to the cladding.In this paper,the effects of fiber parameters on the performance of the sensor were studied by simulation and experiment.Based on the conclusion that the smaller the core diameter is,the closer the working band of the SPR resonance is to long wavelengths,and that the geometric characteristics mean that a multimode fiber can receive the fiber cladding light from a small core diameter few-mode fiber,a dual channel SPR sensor with a double S-type fiber cascade was proposed.In the refractive index detection range of 1.333–1.385refractive index units(RIU),the resonant working band of channel I is 627.66 nm–759.78 nm,with an average sensitivity of 2540.77 nm/RIU,and the resonant working band of channel II is 518.24 nm–658.2 nm,with an average sensitivity of2691.54 nm/RIU.The processing method for the S-type fiber cladding SPR sensor is simple,effectively solving the problem of this type of SPR sensor structure and the difficult realization of a dual channel.The sensor is expected to be used in the fields of medical treatment and biological analysis.展开更多
Ad hoc on-demand distance vector( AODV) routing is one of the typical reactive routing protocols of vehicular ad hoc networks( VANET). Considering link stability and channel switching can greatly improve the QoS of pr...Ad hoc on-demand distance vector( AODV) routing is one of the typical reactive routing protocols of vehicular ad hoc networks( VANET). Considering link stability and channel switching can greatly improve the QoS of protocols,in this paper,we propose a novel routing protocol: optimized cross-layer AODV( CL_ AODV) designed for VANET. It utilizes the frame transmission efficiency( FTE),path bandwidth in media access control( MAC) layer and signal-to-noise ratio( SNIR) in physical( PHY) layer to improve the link stability. In other words,it can increase packet delivery ratio effectively. In addition,end-to-end delay will be decreased based on the channel switching. According to the simulation,it is shown that the packet delivery ratio of CL_AODV is almost up to 99% and the highest compared to AODV and muti-constrained QoS AODV( MQ_ AODV). The delay of CL_AODV is almost half of MQ_ AODV's and 1 /3 of AODV's.Meanwhile,CL_AODV has the highest routing overhead or energy consuming. Because of the feature of VANET,the disadvantage can be ignored.展开更多
Three different kinds of closure model of fiber orientation tensors were applied to simulate numerically the hydrodynamic stability of fiber suspensions in a channel flow. The effects of closure models and three_dimen...Three different kinds of closure model of fiber orientation tensors were applied to simulate numerically the hydrodynamic stability of fiber suspensions in a channel flow. The effects of closure models and three_dimensional (3_D) orientation distribution of fibers on the results of stability analysis were examined. It is found that the relationship of the behavior in hydrodynamic stability and the parameter of the fiber given by all the three models are the same. However, the attenuation of flow instability is most distinct using 3_D hybrid model because the orientation of the fiber departures from the flow direction, and least apparent using its 2_D counterpart for that the fibers show a tendency towards alignment with the flow direction in this case.展开更多
Different from previous temporal evolution assumption, the spatially growing mode was employed to analyze the linear stability for the channel flow of fiber suspensions. The stability equation applicable to fiber susp...Different from previous temporal evolution assumption, the spatially growing mode was employed to analyze the linear stability for the channel flow of fiber suspensions. The stability equation applicable to fiber suspensions was established and solutions for a wide range of Reynolds number and angular frequency were given numerically . The results show that, the flow instability is governed by a parameter H which represents a ratio between the axial stretching resistance of fiber and the inertial force of the fluid. An increase of H leads to a raise of the critical Reynolds number, a decrease of corresponding wave number, a slowdown of the decreasing of phase velocity , a growth of the spatial attenuation rate and a diminishment of the peak value of disturbance velocity. Although the unstable region is reduced on the whole, long wave disturbances are susceptible to fibers.展开更多
We demonstrate a 300-km+200-km cascaded coherent phase transfer via fiber link.The transfer is divided into a 300-km span and a 200-km span with independent phase locking loops,aiming to extend the phase control bandw...We demonstrate a 300-km+200-km cascaded coherent phase transfer via fiber link.The transfer is divided into a 300-km span and a 200-km span with independent phase locking loops,aiming to extend the phase control bandwidth of the whole link.The phase noise and transfer instability of the cascaded transmission are investigated and compared with those in the case of a single-span 500-km transfer.We achieve the transfer instabilities of 1.8×10^-14 at 1 s,8.9×10^-20 at 104 s for the 300-km+200-km cascaded transmission,and 2.7×10^-14 at 1 s for the 500-km single-span transfer.展开更多
The structural features of fiber suspensions are dependent on the fiber alignment in the flows. In this work the orientation distribution function and orientation tensors for semi-concentrated fiber suspensions in ...The structural features of fiber suspensions are dependent on the fiber alignment in the flows. In this work the orientation distribution function and orientation tensors for semi-concentrated fiber suspensions in converging channel flow were calculated, and the evolutions of the fiber alignment and the bulk effective vis-cosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of therate-of-strain tensor and the fiber orientation state ; and that the fiber suspensions evolved to steady alignment and tended to concentrate to some preferred directions close to but not same as the directions of local stream-lines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of ef-fective viscosity near the boundary benefited the increase of the rate of flow. Finally when the fiber alignment went into steady state, the structural features of fiber suspensions were not dependent on the Reynolds numberbut on the converging channel angle.展开更多
The concentration and orientation of fiber in a turbulent T-shaped branching channel flow are investi-gated numerically. The Reynolds averaged Navier-Stokes equations together with the Reynolds stress turbulent model ...The concentration and orientation of fiber in a turbulent T-shaped branching channel flow are investi-gated numerically. The Reynolds averaged Navier-Stokes equations together with the Reynolds stress turbulent model are solved for the mean flow field and the turbulent kinetic energy. The fluctuating velocities of the fluid are assumed as a random variable with Gaussian distribution whose variance is related to the turbulent kinetic energy. The slender-body theory is used to simulate the fiber motion based on the known mean and fluctuating velocities of the fluid. The results show that at low Reynolds number, fiber concentration is high in the flow separation regions, and fiber orientation throughout the channel is widely distributed with a slight preference of aligning along the horizontal axis. With increasing of Re, the high concentration region disappears, and fiber orientation becomes ho-mogeneous without any preferred direction. At high Reynolds number, fiber concentration increases gradually along the flow direction. The differences in the distribution of concentration and orientation between different fiber aspect ratio are evident only at low Re. Both Re and fiber aspect ratio have small effect on the variance of orientation angle.展开更多
This paper presents a link allocation and rate assignment algorithm for multi-channel wireless networks.The objective is to reduce network conflicts and guarantee the fairness among links.We first design a new network...This paper presents a link allocation and rate assignment algorithm for multi-channel wireless networks.The objective is to reduce network conflicts and guarantee the fairness among links.We first design a new network model.With this network model,the multi-channel wireless network is divided into several subnets according to the number of channels.Based on this,we present a link allocation algorithm with time complexity O(l2) to allocate all links to subnets.This link allocation algorithm adopts conflict matrix to minimize the network contention factor.After all links are allocated to subnets,the rate assignment algorithm to maximize a fairness utility in each subnet is presented.The rate assignment algorithm adopts a near-optimal algorithm based on dual decomposition and realizes in a distributed way.Simulation results demonstrate that,compared with IEEE 802.11b and slotted seeded channel hopping algorithm,our algorithm decreases network conflicts and improves the network throughput significantly.展开更多
Improvement strength is beneficial to the popularization of hollow fiber nanofiltration(NF) membrane.The tri-channel hollow fiber NF membrane was prepared by interfacial polymerization(IP).The high strength tri-channe...Improvement strength is beneficial to the popularization of hollow fiber nanofiltration(NF) membrane.The tri-channel hollow fiber NF membrane was prepared by interfacial polymerization(IP).The high strength tri-channel hollow fiber ultrafiltration(UF) membrane were used as the support membrane,m-phenylenedianline(m-PDA),and polyethylenimine(PEI) were used as aqueous phase monomer,and trimesoyl chloride(TMC) was used as organic phase monomer.Fourier transform infrared spectroscopy(FTIR),scanning electron microscope(SEM),and gas sorption analyzer(GSA) were applied in structural analysis of NF membrane.Polymer FTIR illustrates the IP occurrence between aqueous phase monomer and organic phase monomer.The SEM images of NF membrane show the formation of a thin dense layer on surface of support membrane after IP.The flux(J) of optimal NF membrane is 11.2 L·m-2· h-1 at the 0.35 MPa operating pressure.Its retention(R) for NaCl,Na2SO4,MgCl2,Xylenol orange,and Neutral red is 17.4%,30.2%,16.1%,94.3%,and 51.0%,respectively.The NF membrane is on negative charge and its pore radius distributes between 0.3-2.0 nm.展开更多
This paper investigates the cross-correlation characteristics of large-scale parameters(LSPs) and small-scale fading(SSF) for high-speed railway(HSR) multilink propagation scenarios, based on realistic measurements co...This paper investigates the cross-correlation characteristics of large-scale parameters(LSPs) and small-scale fading(SSF) for high-speed railway(HSR) multilink propagation scenarios, based on realistic measurements conducted on Beijing to Tianjin HSR line in China. A long-term evolution-based channel sounding system is utilized in the measurements to obtain the channel data. By applying a proposed time-delay based dynamic partition method, multi-link channel impulse responses are extracted from the raw channel data. Then, the statistical results of LSPs, including shadow fading, K-factor, and root-mean-square delay spread are derived and the cross-correlation coefficients of these LPSs are calculated. Moreover, the SSF spatial correlation and cross-correlation of SSF are analyzed. These results can be used to exploit multi-link channel model and to optimize the next-generation HSR communication system.展开更多
Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene (CLPS) as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysila...Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene (CLPS) as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysilane (VTES), vinyl trimethoxysilane (VTMS) and γ-methacryloylpropyl trimethoxysilane (MPS). The treated glass fibers were analyzed by fourier transform infrared spectroscopy (FTIR). Dynamic mechanical thermal analysis (DMTA) and thermo-gravimetric analysis (TGA) were employed to investigate the effect of glass fibers surface modification on viscoelastic behavior and thermal properties. The morphology of fracture surfaces of various composites was observed by scanning electron microscopy (SEM). The results revealed that these coupling agents were connected to the surfaces of the fibers by chemical bonding. Dynamic mechanical properties as well as thermal stability of the composites were improved considerablely, but to varying degrees depending on the fiber modification. The diversities of improvement of properties were attributed to the different interfacial adhesion between CLPS matrix and the glass fibers.展开更多
基金supported by the National Major Science and Technology Infrastructure Project of China,for“High Precision Ground-based Time Service System”(Grant No.2017-000052-73-01-002401)the National Natural Science Foundation of China(Grant No.12033007)。
文摘An implementation of high-precision time transfer over a 1839-km field fiber loop back link between two provincial capitals of China,Xi’an and Taiyuan,is reported.Time transfer stabilities of 6.5 ps at averaging time of 1 s and 4.6 ps at 40000 s were achieved.The uncertainty for the time transfer system was evaluated,showing a budget of 56.2 ps.These results stand for a significant milestone in achieving high-precision time transfer over a field fiber link spanning thousands of kilometers,signifying a record-breaking achievement for the real-field time transfer in both stability and distance,which paves the way for constructing the nationwide high-precision time service via fiber network.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61877054,12031004,and 12271474).
文摘We establish the Stinespring dilation theorem of the link product of quantum channels in two different ways,discuss the discrimination of quantum channels,and show that the distinguishability can be improved by self-linking each quantum channel n times as n grows.We also find that the maximum value of Uhlmann's theorem can be achieved for diagonal channels.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12103059,12033007,12303077,and 12303076)the Fund from the Xi’an Science and Technology Bureau,China(Grant No.E019XK1S04)the Fund from the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.1188000XGJ).
文摘We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase locking loop in the conventional active phase control scheme,the passive phase noise cancellation is realized by feeding double-trip beat-note frequency to the driver of the acoustic optical modulator at the local site.This passive scheme exhibits fine robustness and reliability,making it suitable for long-distance and noisy fiber links.An optical regeneration station is used in the link for signal amplification and cascaded transmission.The phase noise cancellation and transfer instability of the 972-km link is investigated,and transfer instability of 1.1×10^(-19)at 10^(4)s is achieved.This work provides a promising method for realizing optical frequency distribution over thousands of kilometers by using fiber links.
基金the National Natural Science Foundation of China(Grant No.61705025)Chongqing Natural Science Foundation(Grant Nos.cstc2019jcyjmsxmX0431 and cstc2018jcyjAX0817)+2 种基金the Science and Technology Project Affiliated to the Education Department of Chongqing Municipality(Grant Nos.KJQN201801217,KJQN201901226,KJQN202001214,and KJ1710247)Chongqing Key Laboratory of Geological Environment Monitoring and Disaster Early-Warning in Three Gorges Reservoir Area(Grant Nos.ZD2020A0103 and ZD2020A0102)Fundamental Research Funds for Chongqing Three Gorges University of China(Grant No.19ZDPY08).
文摘Fiber cladding surface plasmon resonance(SPR)sensors have few structures,and a clad SPR sensor based on S-type fiber is proposed in this paper.This new type of fiber cladding SPR sensor was formed by electrofusing an S-shaped structure on the fiber to couple the light in the fiber core to the cladding.In this paper,the effects of fiber parameters on the performance of the sensor were studied by simulation and experiment.Based on the conclusion that the smaller the core diameter is,the closer the working band of the SPR resonance is to long wavelengths,and that the geometric characteristics mean that a multimode fiber can receive the fiber cladding light from a small core diameter few-mode fiber,a dual channel SPR sensor with a double S-type fiber cascade was proposed.In the refractive index detection range of 1.333–1.385refractive index units(RIU),the resonant working band of channel I is 627.66 nm–759.78 nm,with an average sensitivity of 2540.77 nm/RIU,and the resonant working band of channel II is 518.24 nm–658.2 nm,with an average sensitivity of2691.54 nm/RIU.The processing method for the S-type fiber cladding SPR sensor is simple,effectively solving the problem of this type of SPR sensor structure and the difficult realization of a dual channel.The sensor is expected to be used in the fields of medical treatment and biological analysis.
基金National Natural Science Foundation of China(No.71171045)
文摘Ad hoc on-demand distance vector( AODV) routing is one of the typical reactive routing protocols of vehicular ad hoc networks( VANET). Considering link stability and channel switching can greatly improve the QoS of protocols,in this paper,we propose a novel routing protocol: optimized cross-layer AODV( CL_ AODV) designed for VANET. It utilizes the frame transmission efficiency( FTE),path bandwidth in media access control( MAC) layer and signal-to-noise ratio( SNIR) in physical( PHY) layer to improve the link stability. In other words,it can increase packet delivery ratio effectively. In addition,end-to-end delay will be decreased based on the channel switching. According to the simulation,it is shown that the packet delivery ratio of CL_AODV is almost up to 99% and the highest compared to AODV and muti-constrained QoS AODV( MQ_ AODV). The delay of CL_AODV is almost half of MQ_ AODV's and 1 /3 of AODV's.Meanwhile,CL_AODV has the highest routing overhead or energy consuming. Because of the feature of VANET,the disadvantage can be ignored.
基金ProjectsupportedbytheNationalNaturalScienceFoundationofChina (No .1 0 3 72 0 90 )
文摘Three different kinds of closure model of fiber orientation tensors were applied to simulate numerically the hydrodynamic stability of fiber suspensions in a channel flow. The effects of closure models and three_dimensional (3_D) orientation distribution of fibers on the results of stability analysis were examined. It is found that the relationship of the behavior in hydrodynamic stability and the parameter of the fiber given by all the three models are the same. However, the attenuation of flow instability is most distinct using 3_D hybrid model because the orientation of the fiber departures from the flow direction, and least apparent using its 2_D counterpart for that the fibers show a tendency towards alignment with the flow direction in this case.
基金Foundation item: the National Natural Science Foundation of China for Outstanding Young Sci-entists (19925210)
文摘Different from previous temporal evolution assumption, the spatially growing mode was employed to analyze the linear stability for the channel flow of fiber suspensions. The stability equation applicable to fiber suspensions was established and solutions for a wide range of Reynolds number and angular frequency were given numerically . The results show that, the flow instability is governed by a parameter H which represents a ratio between the axial stretching resistance of fiber and the inertial force of the fluid. An increase of H leads to a raise of the critical Reynolds number, a decrease of corresponding wave number, a slowdown of the decreasing of phase velocity , a growth of the spatial attenuation rate and a diminishment of the peak value of disturbance velocity. Although the unstable region is reduced on the whole, long wave disturbances are susceptible to fibers.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFF0200200)the National Natural Science Foundation of China(Grant Nos.91636101,91836301,and 11803041)+1 种基金the West Light Foundation of the Chinese Academy of Sciences(Grant No.XAB2016B47)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21000000)。
文摘We demonstrate a 300-km+200-km cascaded coherent phase transfer via fiber link.The transfer is divided into a 300-km span and a 200-km span with independent phase locking loops,aiming to extend the phase control bandwidth of the whole link.The phase noise and transfer instability of the cascaded transmission are investigated and compared with those in the case of a single-span 500-km transfer.We achieve the transfer instabilities of 1.8×10^-14 at 1 s,8.9×10^-20 at 104 s for the 300-km+200-km cascaded transmission,and 2.7×10^-14 at 1 s for the 500-km single-span transfer.
文摘The structural features of fiber suspensions are dependent on the fiber alignment in the flows. In this work the orientation distribution function and orientation tensors for semi-concentrated fiber suspensions in converging channel flow were calculated, and the evolutions of the fiber alignment and the bulk effective vis-cosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of therate-of-strain tensor and the fiber orientation state ; and that the fiber suspensions evolved to steady alignment and tended to concentrate to some preferred directions close to but not same as the directions of local stream-lines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of ef-fective viscosity near the boundary benefited the increase of the rate of flow. Finally when the fiber alignment went into steady state, the structural features of fiber suspensions were not dependent on the Reynolds numberbut on the converging channel angle.
基金Supported by the Major Program of the National Natural Science Foundation of China (No.10632070).
文摘The concentration and orientation of fiber in a turbulent T-shaped branching channel flow are investi-gated numerically. The Reynolds averaged Navier-Stokes equations together with the Reynolds stress turbulent model are solved for the mean flow field and the turbulent kinetic energy. The fluctuating velocities of the fluid are assumed as a random variable with Gaussian distribution whose variance is related to the turbulent kinetic energy. The slender-body theory is used to simulate the fiber motion based on the known mean and fluctuating velocities of the fluid. The results show that at low Reynolds number, fiber concentration is high in the flow separation regions, and fiber orientation throughout the channel is widely distributed with a slight preference of aligning along the horizontal axis. With increasing of Re, the high concentration region disappears, and fiber orientation becomes ho-mogeneous without any preferred direction. At high Reynolds number, fiber concentration increases gradually along the flow direction. The differences in the distribution of concentration and orientation between different fiber aspect ratio are evident only at low Re. Both Re and fiber aspect ratio have small effect on the variance of orientation angle.
基金This work was supported by the National Natural Science Foundation of China under Cxant No. 60902010 the Research Fund of State Key Laboratory of Mobile Communications un-der Crant No. 2012A03.
文摘This paper presents a link allocation and rate assignment algorithm for multi-channel wireless networks.The objective is to reduce network conflicts and guarantee the fairness among links.We first design a new network model.With this network model,the multi-channel wireless network is divided into several subnets according to the number of channels.Based on this,we present a link allocation algorithm with time complexity O(l2) to allocate all links to subnets.This link allocation algorithm adopts conflict matrix to minimize the network contention factor.After all links are allocated to subnets,the rate assignment algorithm to maximize a fairness utility in each subnet is presented.The rate assignment algorithm adopts a near-optimal algorithm based on dual decomposition and realizes in a distributed way.Simulation results demonstrate that,compared with IEEE 802.11b and slotted seeded channel hopping algorithm,our algorithm decreases network conflicts and improves the network throughput significantly.
基金National High Technology Research and Development Program of China (863 program) (No. 2008AA06Z330)National Technician Service Enterprise Action Program,China (No. 2009GJD00048)
文摘Improvement strength is beneficial to the popularization of hollow fiber nanofiltration(NF) membrane.The tri-channel hollow fiber NF membrane was prepared by interfacial polymerization(IP).The high strength tri-channel hollow fiber ultrafiltration(UF) membrane were used as the support membrane,m-phenylenedianline(m-PDA),and polyethylenimine(PEI) were used as aqueous phase monomer,and trimesoyl chloride(TMC) was used as organic phase monomer.Fourier transform infrared spectroscopy(FTIR),scanning electron microscope(SEM),and gas sorption analyzer(GSA) were applied in structural analysis of NF membrane.Polymer FTIR illustrates the IP occurrence between aqueous phase monomer and organic phase monomer.The SEM images of NF membrane show the formation of a thin dense layer on surface of support membrane after IP.The flux(J) of optimal NF membrane is 11.2 L·m-2· h-1 at the 0.35 MPa operating pressure.Its retention(R) for NaCl,Na2SO4,MgCl2,Xylenol orange,and Neutral red is 17.4%,30.2%,16.1%,94.3%,and 51.0%,respectively.The NF membrane is on negative charge and its pore radius distributes between 0.3-2.0 nm.
基金supported by the Beijing Municipal Natural Science Foundation under Grant 4174102the National Natural Science Foundation of China under Grant 61701017+1 种基金the Open Research Fund through the National Mobile Communications Research Laboratory, Southeast University, under Grant 2018D11the Fundamental Research Funds for the Central Universities under Grant 2018JBM003
文摘This paper investigates the cross-correlation characteristics of large-scale parameters(LSPs) and small-scale fading(SSF) for high-speed railway(HSR) multilink propagation scenarios, based on realistic measurements conducted on Beijing to Tianjin HSR line in China. A long-term evolution-based channel sounding system is utilized in the measurements to obtain the channel data. By applying a proposed time-delay based dynamic partition method, multi-link channel impulse responses are extracted from the raw channel data. Then, the statistical results of LSPs, including shadow fading, K-factor, and root-mean-square delay spread are derived and the cross-correlation coefficients of these LPSs are calculated. Moreover, the SSF spatial correlation and cross-correlation of SSF are analyzed. These results can be used to exploit multi-link channel model and to optimize the next-generation HSR communication system.
基金Supported by National Natural Science Foundation of China (No.50872101,A3 Foresight Program-50821140308)National Basic Research Program of China (No.2009CB939704)a joint project of National Nature Science Foundation of China and Russian Foundation for Basic Research(No.NSFC-RFBR 51011120252)
文摘Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene (CLPS) as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysilane (VTES), vinyl trimethoxysilane (VTMS) and γ-methacryloylpropyl trimethoxysilane (MPS). The treated glass fibers were analyzed by fourier transform infrared spectroscopy (FTIR). Dynamic mechanical thermal analysis (DMTA) and thermo-gravimetric analysis (TGA) were employed to investigate the effect of glass fibers surface modification on viscoelastic behavior and thermal properties. The morphology of fracture surfaces of various composites was observed by scanning electron microscopy (SEM). The results revealed that these coupling agents were connected to the surfaces of the fibers by chemical bonding. Dynamic mechanical properties as well as thermal stability of the composites were improved considerablely, but to varying degrees depending on the fiber modification. The diversities of improvement of properties were attributed to the different interfacial adhesion between CLPS matrix and the glass fibers.