This paper stuides numerically the model equation in a one dimensional defective photonic lattice by modifying the potential function to a periodic function. It is found that defect modes （DMs） can be regarded as Bl...This paper stuides numerically the model equation in a one dimensional defective photonic lattice by modifying the potential function to a periodic function. It is found that defect modes （DMs） can be regarded as Bloch modes which are excited from the extended photonie band-gap structure at Bloch wave-numbers with kx = 0. The DMs for both positive and negative defects are considered in this method.展开更多
We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedde...We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedded in the two-dimensional optical lattice gives rise to some unique properties. It is interestingly found that for the negative defect, stable surface defect gap solitons can exist both in the semi-infinite gap and in the first gap. The deeper the negative defect, the narrower the stable region in the semi-infinite gap will be. For a positive defect, the surface defect gap solitons exist only in the semi-infinite gap and the stable region localizes in a low power region.展开更多
We study the surface defect gap solitons in an interface between a defect of one-dimensional dual-frequency lattices and the uniform media. Some unique properties are revealed that such lattices can broaden the region...We study the surface defect gap solitons in an interface between a defect of one-dimensional dual-frequency lattices and the uniform media. Some unique properties are revealed that such lattices can broaden the region of semi-finite gap, and the semi-finite gap exists not only in the positive and zero defects but also in the negative defect; unlike in the regular lattices, the semi-finite gap exists in the positive and zero defects but does not exist in the negative defect. In particular, stable solitons exist almost in the whole semi-finite gap for the positive and zero defects. These properties are different from other lattices with defects. In addition, it is found that the existence of surface dual-frequency lattice solitons does not need a threshold power.展开更多
A one dimensional model is developed for defective gap mode（DGM）with two types of boundary conditions：conducting mesh and conducting sleeve.For a periodically modulated system without defect,the normalized width of...A one dimensional model is developed for defective gap mode（DGM）with two types of boundary conditions：conducting mesh and conducting sleeve.For a periodically modulated system without defect,the normalized width of spectral gaps equals to the modulation factor,which is consistent with previous studies.For a periodic system with local defects introduced by the boundary conditions,it shows that the conducting-mesh-induced DGM is always well confined by spectral gaps while the conducting-sleeve-induced DGM is not.The defect location can be a useful tool to dynamically control the frequency and spatial periodicity of DGM inside spectral gaps.This controllability can be potentially applied to the interaction between gap eigenmodes and energetic particles in fusion plasmas,and optical microcavities and waveguides in photonic crystals.展开更多
During peripheral nerve transposition repair, if the diameter difference between transposed nerves is large or multiple distal nerves must be repaired at the same time, traditional epineurial neurorrhaphy has the prob...During peripheral nerve transposition repair, if the diameter difference between transposed nerves is large or multiple distal nerves must be repaired at the same time, traditional epineurial neurorrhaphy has the problem of high tension at the suture site, which may even lead to the failure of nerve suture. We investigated whether a small gap bio-sleeve suture with different inner diameters at both ends can be used to repair a 2-mm tibial nerve defect by proximal transposition of the common peroneal nerve in rats and compared the results with the repair seen after epineurial neurorrhaphy. Three months after surgery, neurological function, nerve regeneration, and recovery of nerve innervation muscle were assessed using the tibial nerve function index, neuroelectrophysiological testing, muscle biomechanics and wet weight measurement, osmic acid staining, and hematoxylin-eosin staining. There was no obvious inflammatory reaction and neuroma formation in the tibial nerve after repair by the small gap bio-sleeve suture with different inner diameters at both ends. The conduction velocity, muscle strength, wet muscle weight, cross-sectional area of muscle fibers, and the number of new myelinated nerve fibers in the biosleeve suture group were similar to those in the epineurial neurorrhaphy group. Our findings indicate that small gap bio-sleeve suture with different inner diameters at both ends can achieve surgical suture between nerves of different diameters and promote regeneration and functional recovery of injured peripheral nerves.展开更多
The band structures of a new two-dimensional triangle-shaped array geometry of 4340 steel cylinders of square cross section in an epoxy resin were studied by the plane-wave expansion and supercell calculation method. ...The band structures of a new two-dimensional triangle-shaped array geometry of 4340 steel cylinders of square cross section in an epoxy resin were studied by the plane-wave expansion and supercell calculation method. The band gaps of this type of phononic crystals with different defects were calculated such as defect-free, 60° crystal linear defect states, 120° crystal linear defect states, and 180° crystal linear defect states. It was found that the band gap will emerge in different linear defects of the phononic crystals and the bandwidth of linear defect states is larger than that of the free-defect crystal by about 2.14 times within the filling fraction F = 0.1-0.85. In addition, the influence of the filling fraction on the relative width of the minimum band gap is discussed.展开更多
In this manuscript, we used the SCAPS-1D software to perform numerical simulations on a perovskite solar cell. These simulations were used to study the influence of certain parameters on the electrical behavior of the...In this manuscript, we used the SCAPS-1D software to perform numerical simulations on a perovskite solar cell. These simulations were used to study the influence of certain parameters on the electrical behavior of the cell. We have shown in this study that electron mobility is strongly influenced by the thickness of the absorber, since electron velocity is reduced by thickness. The influence of the defect density shows that above 10<sup>16</sup> cm<sup>-3</sup> all the electrical parameters are affected by the defects. The band discontinuity at the interface generally plays a crucial role in the charge transport phenomenon. The importance of this study is to enable the development of good quality perovskite solar cells, while taking into account the parameters that limit solar cell performance.展开更多
Graphene has attracted immense investigation since its discovery.Lattice imperfections are introduced into graphene unavoidably during graphene growth or processing.These structural defects are known to significantly ...Graphene has attracted immense investigation since its discovery.Lattice imperfections are introduced into graphene unavoidably during graphene growth or processing.These structural defects are known to significantly affect electronic and chemical properties of graphene.A comprehensive understanding of graphene defect is thus of critical importance.Here we review the major progresses made in defectrelated engineering of graphene.Firstly,we give a brief introduction on the types of defects in graphene.Secondly,the generation and healing of the graphene defects are summarized.Then,the effects of defects on the chemical,electronic,magnetic,and mechanical properties of graphene are discussed.Finally,we address the associated challenges and prospects on the future study of defects in graphene and other nanocarbon materials.展开更多
Two kinds of compact electromagnetic band gap （EBG） structures are designed. A two layer compact EBG structure configured with cross spiral shape line inductors and interdigital capacitors is first presented. Becaus...Two kinds of compact electromagnetic band gap （EBG） structures are designed. A two layer compact EBG structure configured with cross spiral shape line inductors and interdigital capacitors is first presented. Because of its significantly enlarged equivalent inductor and capacitance, the period of the lattice is approximately 4.5% of the free space wavelength. By insetting several narrow slits in the ground plane, the bandwidth of the main bandgap is enhanced by nearly 19%. Further effort has been made for designing a three layer compact EBG structure. Simulation results show that its period is reduced by about 26% compared to that of proposed two layer EBG structure, and the bandwidth of the main bandgap is about 3 times as that of the proposed two layer EBG structure. The detailed designs including a two layer compact 3×7 EBG array with and without defect ground plane and the three layer EBG array are given and simulation results are presented.展开更多
Different feeding techniques of microstrip patch antennas with different spiral defected ground structures are presented in this paper. The investigated structures illustrate some merits in designing multi-electromagn...Different feeding techniques of microstrip patch antennas with different spiral defected ground structures are presented in this paper. The investigated structures illustrate some merits in designing multi-electromagnetic band-gap structures by adjusting the capacitance and changing the inductance through varying the width and length of spiral defected ground structure. Then by applying the three different spirals shapes (one, two and four arms) as the ground plane of microstrip patch antenna with different feeding techniques to create multi or ultra wide-band, improve the antenna gain and reduce the antenna size, it is found that the four arms spiral defected ground structure of microstrip patch antenna with offset feed gives good performance, electrical size reduction to about 75% as compared to the original patch size and ultra-wide bandwidth extends from 2 GHz up to 12 GHz with ?8 dB impedance bandwidth.展开更多
Optical features of a semiconductor–dielectric photonic crystal are studied theoretically. Alternating layers of micrometer sized SiO2/In Sb slabs are considered as building blocks of the proposed ideal crystal. By i...Optical features of a semiconductor–dielectric photonic crystal are studied theoretically. Alternating layers of micrometer sized SiO2/In Sb slabs are considered as building blocks of the proposed ideal crystal. By inserting additional layers and disrupting the regularity, two more defective crystals are also proposed. Photonic band structure of the ideal crystal and its dependence on the structural parameters are explored at the first step. Transmittance of the defective crystals and its changes with the thicknesses of the layers are studied. After extracting the optimum values for the thicknesses of the unit cells of the crystals, the optical response of the proposed structures at different temperatures and incident angles are investigated. Changes of the defect layers’ induced mode(s) are discussed by taking into consideration of the temperature dependence of the In Sb layer permittivity. The results clearly reflect the high potential of the proposed crystals to be used at high temperature terahertz technology as a promising alternative to their electronic counterparts.展开更多
In this paper, we investigate the optical transmission properties of perfect and defective two-segment-connected tri- angular waveguide networks （2SCTWNs） and find that after introducing defects in networks, many gr...In this paper, we investigate the optical transmission properties of perfect and defective two-segment-connected tri- angular waveguide networks （2SCTWNs） and find that after introducing defects in networks, many groups of transparent extreme narrow photonic passbands （ENPPs） will be created in the middle of the transmission spectra, the number for each group and the group number of ENPPs can he adjusted by the matching ratios of waveguide length （MRWLs）, the number of defects, and the number of unit cells of 2SCTWNs. The influences of MRWL, number of defects, and number of unit cells on the number, width, and position of these ENPPs are researched and a series of quantitative rules and prop- erties are obtained. It may be useful for the designing of high-sensitive optical switches, wavelength division multiplexers, extreme-narrowband filters, and other correlative waveguide network devices.展开更多
We present a detailed theoretical study of the behavior of mono-vacancy and B-doped defects in carbon heterojunction nanodevices. We have introduced a complete set of formation energy and surface reactivity calculatio...We present a detailed theoretical study of the behavior of mono-vacancy and B-doped defects in carbon heterojunction nanodevices. We have introduced a complete set of formation energy and surface reactivity calculations, considering a range of different diameters and chiralities of combined carbon nanotubes. We have investigated three distinct combinations of carbon heterojunctions using density functional theory (DFT) and applying B3LYP/3-21g: armchair-armchair herteojunctions, zigzag-zigzag heterojunctions, and zigzag-armchair heterojunctions. We have shown for first time a detailed study of formation energy of mono-vacancy and B-doped defects of carbon heterojunction nanodevices. Our calculations show that the highest surface reactivity is found for the B-doped zigzag-armchair heterojunctions and it is easier to remove the carbon atom from the network of heterojunction armchair-armchair CNTs than the heterojunction zigzag-armchair and zigzag-zigzag CNTs.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10674038 and 10604042)the National Basic Research Program of China (Grant No. 2006CB302901)
文摘This paper stuides numerically the model equation in a one dimensional defective photonic lattice by modifying the potential function to a periodic function. It is found that defect modes （DMs） can be regarded as Bloch modes which are excited from the extended photonie band-gap structure at Bloch wave-numbers with kx = 0. The DMs for both positive and negative defects are considered in this method.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11174147)the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2009366)
文摘We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedded in the two-dimensional optical lattice gives rise to some unique properties. It is interestingly found that for the negative defect, stable surface defect gap solitons can exist both in the semi-infinite gap and in the first gap. The deeper the negative defect, the narrower the stable region in the semi-infinite gap will be. For a positive defect, the surface defect gap solitons exist only in the semi-infinite gap and the stable region localizes in a low power region.
基金Project supported by the National Natural Science Foundation of China (Grant No 10774031)Natural Science Foundation of Guangdong Province of China (Grant No 07001790)
文摘We study the surface defect gap solitons in an interface between a defect of one-dimensional dual-frequency lattices and the uniform media. Some unique properties are revealed that such lattices can broaden the region of semi-finite gap, and the semi-finite gap exists not only in the positive and zero defects but also in the negative defect; unlike in the regular lattices, the semi-finite gap exists in the positive and zero defects but does not exist in the negative defect. In particular, stable solitons exist almost in the whole semi-finite gap for the positive and zero defects. These properties are different from other lattices with defects. In addition, it is found that the existence of surface dual-frequency lattice solitons does not need a threshold power.
基金supported by National Natural Science Foundation of China(No.11405271)
文摘A one dimensional model is developed for defective gap mode（DGM）with two types of boundary conditions：conducting mesh and conducting sleeve.For a periodically modulated system without defect,the normalized width of spectral gaps equals to the modulation factor,which is consistent with previous studies.For a periodic system with local defects introduced by the boundary conditions,it shows that the conducting-mesh-induced DGM is always well confined by spectral gaps while the conducting-sleeve-induced DGM is not.The defect location can be a useful tool to dynamically control the frequency and spatial periodicity of DGM inside spectral gaps.This controllability can be potentially applied to the interaction between gap eigenmodes and energetic particles in fusion plasmas,and optical microcavities and waveguides in photonic crystals.
基金funded by the National Natural Science Foundation of China,No.31571236,31571235(to YHK and PXZ)National Key Research and Development Program of China,No.2016YFC1101604(to DYZ)+2 种基金National Key Basic Research Program of China(973 Program),No.2014CB542200(to BGJ)Ministry of Education Innovation Program of China,No.IRT_16R01(to BGJ)Beijing Science and Technology New Star Cross Program of China,No.2018019(to PXZ)
文摘During peripheral nerve transposition repair, if the diameter difference between transposed nerves is large or multiple distal nerves must be repaired at the same time, traditional epineurial neurorrhaphy has the problem of high tension at the suture site, which may even lead to the failure of nerve suture. We investigated whether a small gap bio-sleeve suture with different inner diameters at both ends can be used to repair a 2-mm tibial nerve defect by proximal transposition of the common peroneal nerve in rats and compared the results with the repair seen after epineurial neurorrhaphy. Three months after surgery, neurological function, nerve regeneration, and recovery of nerve innervation muscle were assessed using the tibial nerve function index, neuroelectrophysiological testing, muscle biomechanics and wet weight measurement, osmic acid staining, and hematoxylin-eosin staining. There was no obvious inflammatory reaction and neuroma formation in the tibial nerve after repair by the small gap bio-sleeve suture with different inner diameters at both ends. The conduction velocity, muscle strength, wet muscle weight, cross-sectional area of muscle fibers, and the number of new myelinated nerve fibers in the biosleeve suture group were similar to those in the epineurial neurorrhaphy group. Our findings indicate that small gap bio-sleeve suture with different inner diameters at both ends can achieve surgical suture between nerves of different diameters and promote regeneration and functional recovery of injured peripheral nerves.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10764005 and 11164034)the New Century Training Program Foundation for Talents from the Ministry of Education of China (Grant No. NCET-08-0926)
文摘The band structures of a new two-dimensional triangle-shaped array geometry of 4340 steel cylinders of square cross section in an epoxy resin were studied by the plane-wave expansion and supercell calculation method. The band gaps of this type of phononic crystals with different defects were calculated such as defect-free, 60° crystal linear defect states, 120° crystal linear defect states, and 180° crystal linear defect states. It was found that the band gap will emerge in different linear defects of the phononic crystals and the bandwidth of linear defect states is larger than that of the free-defect crystal by about 2.14 times within the filling fraction F = 0.1-0.85. In addition, the influence of the filling fraction on the relative width of the minimum band gap is discussed.
文摘In this manuscript, we used the SCAPS-1D software to perform numerical simulations on a perovskite solar cell. These simulations were used to study the influence of certain parameters on the electrical behavior of the cell. We have shown in this study that electron mobility is strongly influenced by the thickness of the absorber, since electron velocity is reduced by thickness. The influence of the defect density shows that above 10<sup>16</sup> cm<sup>-3</sup> all the electrical parameters are affected by the defects. The band discontinuity at the interface generally plays a crucial role in the charge transport phenomenon. The importance of this study is to enable the development of good quality perovskite solar cells, while taking into account the parameters that limit solar cell performance.
基金supported by the National Natural Science Foundation of China(Nos.21276257 and 2110600)the Research Foundation for Youth Scholars of Beijing Technology and Business University(No.QNJJ2014-14)
文摘Graphene has attracted immense investigation since its discovery.Lattice imperfections are introduced into graphene unavoidably during graphene growth or processing.These structural defects are known to significantly affect electronic and chemical properties of graphene.A comprehensive understanding of graphene defect is thus of critical importance.Here we review the major progresses made in defectrelated engineering of graphene.Firstly,we give a brief introduction on the types of defects in graphene.Secondly,the generation and healing of the graphene defects are summarized.Then,the effects of defects on the chemical,electronic,magnetic,and mechanical properties of graphene are discussed.Finally,we address the associated challenges and prospects on the future study of defects in graphene and other nanocarbon materials.
基金supported by the National Natural Science Foundation of China under Grant No. 60588502
文摘Two kinds of compact electromagnetic band gap （EBG） structures are designed. A two layer compact EBG structure configured with cross spiral shape line inductors and interdigital capacitors is first presented. Because of its significantly enlarged equivalent inductor and capacitance, the period of the lattice is approximately 4.5% of the free space wavelength. By insetting several narrow slits in the ground plane, the bandwidth of the main bandgap is enhanced by nearly 19%. Further effort has been made for designing a three layer compact EBG structure. Simulation results show that its period is reduced by about 26% compared to that of proposed two layer EBG structure, and the bandwidth of the main bandgap is about 3 times as that of the proposed two layer EBG structure. The detailed designs including a two layer compact 3×7 EBG array with and without defect ground plane and the three layer EBG array are given and simulation results are presented.
文摘Different feeding techniques of microstrip patch antennas with different spiral defected ground structures are presented in this paper. The investigated structures illustrate some merits in designing multi-electromagnetic band-gap structures by adjusting the capacitance and changing the inductance through varying the width and length of spiral defected ground structure. Then by applying the three different spirals shapes (one, two and four arms) as the ground plane of microstrip patch antenna with different feeding techniques to create multi or ultra wide-band, improve the antenna gain and reduce the antenna size, it is found that the four arms spiral defected ground structure of microstrip patch antenna with offset feed gives good performance, electrical size reduction to about 75% as compared to the original patch size and ultra-wide bandwidth extends from 2 GHz up to 12 GHz with ?8 dB impedance bandwidth.
文摘Optical features of a semiconductor–dielectric photonic crystal are studied theoretically. Alternating layers of micrometer sized SiO2/In Sb slabs are considered as building blocks of the proposed ideal crystal. By inserting additional layers and disrupting the regularity, two more defective crystals are also proposed. Photonic band structure of the ideal crystal and its dependence on the structural parameters are explored at the first step. Transmittance of the defective crystals and its changes with the thicknesses of the layers are studied. After extracting the optimum values for the thicknesses of the unit cells of the crystals, the optical response of the proposed structures at different temperatures and incident angles are investigated. Changes of the defect layers’ induced mode(s) are discussed by taking into consideration of the temperature dependence of the In Sb layer permittivity. The results clearly reflect the high potential of the proposed crystals to be used at high temperature terahertz technology as a promising alternative to their electronic counterparts.
基金Project supported by the National Natural Science Foundations of China(Grant Nos.11374107 and 10974061)
文摘In this paper, we investigate the optical transmission properties of perfect and defective two-segment-connected tri- angular waveguide networks （2SCTWNs） and find that after introducing defects in networks, many groups of transparent extreme narrow photonic passbands （ENPPs） will be created in the middle of the transmission spectra, the number for each group and the group number of ENPPs can he adjusted by the matching ratios of waveguide length （MRWLs）, the number of defects, and the number of unit cells of 2SCTWNs. The influences of MRWL, number of defects, and number of unit cells on the number, width, and position of these ENPPs are researched and a series of quantitative rules and prop- erties are obtained. It may be useful for the designing of high-sensitive optical switches, wavelength division multiplexers, extreme-narrowband filters, and other correlative waveguide network devices.
文摘We present a detailed theoretical study of the behavior of mono-vacancy and B-doped defects in carbon heterojunction nanodevices. We have introduced a complete set of formation energy and surface reactivity calculations, considering a range of different diameters and chiralities of combined carbon nanotubes. We have investigated three distinct combinations of carbon heterojunctions using density functional theory (DFT) and applying B3LYP/3-21g: armchair-armchair herteojunctions, zigzag-zigzag heterojunctions, and zigzag-armchair heterojunctions. We have shown for first time a detailed study of formation energy of mono-vacancy and B-doped defects of carbon heterojunction nanodevices. Our calculations show that the highest surface reactivity is found for the B-doped zigzag-armchair heterojunctions and it is easier to remove the carbon atom from the network of heterojunction armchair-armchair CNTs than the heterojunction zigzag-armchair and zigzag-zigzag CNTs.
