Most of the current computing methods used to determine the magnetic field of a uniformly magnetized cuboid assume that the observation point is located in the upper half space without a source. However, such methods ...Most of the current computing methods used to determine the magnetic field of a uniformly magnetized cuboid assume that the observation point is located in the upper half space without a source. However, such methods may generate analytical singularities for conditions of undulating terrain. Based on basic geomagnetic field theories, in this study an improved magnetic field expression is derived using an integration method of variable substitution, and all singularity problems for the entire space without a source are discussed and solved. This integration process is simpler than that of previous methods, and final integral results with a more uniform form. AT at all points in the source-flee space can be calculated without requiring coordinate transformation; thus forward modeling is also simplified. Corresponding model tests indicate that the new magnetic field expression is more correct because there is no analytical singularity and can be used with undulating terrain.展开更多
A simplified method is proposed for analyzing the overpressure history of an optional point on the walls of a closed cuboid due to its internal optional point-explosion. Firstly, the overpressure histories of all node...A simplified method is proposed for analyzing the overpressure history of an optional point on the walls of a closed cuboid due to its internal optional point-explosion. Firstly, the overpressure histories of all nodes on the walls of a cube with a side-length of 2 m are computed under a reference-charge explosion at each node of its inner space using the LS-DYNA software, and then are collected to form a reference database. Next, with the thought of the isoparametric finite element, an interpolating algori...展开更多
Cuboid fractures due to the particular bone anatomy and its protected location in the midfoot are rare, and they are usually associated with complex injuries of the foot. Clinical examination to diagnose these fractur...Cuboid fractures due to the particular bone anatomy and its protected location in the midfoot are rare, and they are usually associated with complex injuries of the foot. Clinical examination to diagnose these fractures should be detailed and the differential diagnosis, especially in the case of vague symptoms, should include the exclusion of all lateral foot pain causes. Conventional radiographs do not always reveal occult fractures, which can be under diagnosed especially in children. In this case, further investigation including magnetic resonance imaging or scintigraphy may be required. The treatment of these injuries depends on the particular fracture characteristics. Non-displaced isolated fractures of the cuboid bone can be effectively treated conservatively by immobilization and by avoiding weight bearing on the injured leg. In the case of shortening of the lateral column> 3 mm or articular displacement > 1 mm, surgical management of the fracture is mandatory in order to avoid negative biomechanical and functional consequences for the foot and adverse effects such as arthritis and stiffness as well as painful gait. In this review, an update on diagnosis and management of cuboid fractures is presented.展开更多
Vertical orthogonal joints are a common feature in shallow crustal rocks.There are several competing theories for their formation despite the ubiquity.We examined the exceptional exposures of orthogonal joints in flat...Vertical orthogonal joints are a common feature in shallow crustal rocks.There are several competing theories for their formation despite the ubiquity.We examined the exceptional exposures of orthogonal joints in flat-lying Ordovician limestone beds from the Havre-Saint-Pierre Region in Quebec,Canada(north shore of Saint-Lawrence River)to test conceptual models of joint formation in a natural setting.In the region,the spacing of cross-joints is consistently larger than the spacing of systematic joints by a factor of 1.5 approximately.The joint-spacing-to-bed-thickness ratios(s/t)are much larger in these beds(s/t=4.3 for systematic joints,and 6.4 for cross-joints)than those in higher strained strata along the south shore of the Saint-Lawrence River(s/t=1),highlighting the effect of tectonic strain in decreasing fracture spacing and block size.The high values of s/t indicate that cross-joint formation was unlikely caused by a switch from compression to tension once a critical s/t ratio for systematic joints was reached(as hypothesized in previous studies).We proposed a new model for the formation of orthogonal joint systems where the principal stress axes locally switch during the formation of systematic fractures.The presence of ladder-shaped orthogonal joints suggests a state of effective stress withσ_(1)^(∗)≫0>σ_(2)^(∗)>σ_(3)^(∗)and whereσ_(2)^(∗)-σ_(3)^(∗)is within the range of fracture strength variability at the time of fracture.This research provides a new mechanical model for the formation of orthogonal joint systems and cuboidal blocks.展开更多
Traveling Salesman Problem (TSP) is one of the most widely studied real world problems of finding the shortest (minimum cost) possible route that visits each node in a given set of nodes (cities) once and then returns...Traveling Salesman Problem (TSP) is one of the most widely studied real world problems of finding the shortest (minimum cost) possible route that visits each node in a given set of nodes (cities) once and then returns to origin city. The optimization of cuboid areas has potential samples that can be adapted to real world. Cuboid surfaces of buildings, rooms, furniture etc. can be given as examples. Many optimization algorithms have been used in solution of optimization problems at present. Among them, meta-heuristic algorithms come first. In this study, ant colony optimization, one of meta-heuristic methods, is applied to solve Euclidian TSP consisting of nine different sized sets of nodes randomly placed on a cuboid surface. The performance of this method is shown in tests.展开更多
This paper investigates the flux-pinning-induced stress behaviors in a long superconducting slab with a central cuboid hole.The distribution of flux density is analytically derived for the critical current density of ...This paper investigates the flux-pinning-induced stress behaviors in a long superconducting slab with a central cuboid hole.The distribution of flux density is analytically derived for the critical current density of Kim model by considering the effects of the hole.The concentration of stress for both of the zero-field cooling(ZFC)and the field cooling(FC)magnetization processes are investigated through numerical simulation by using finite element method.The results indicate the potential failure mode varies with the height-width ratio and the dimensions of the hole.Different to the case of infinite hole height,the stress concentration behavior for the FC process is more critical when the dimensions of the hole are similar.The findings in this paper are useful for understanding of the degrade mechanism of superconductor in service and the design of new system.展开更多
Two novel Co-based clusters with the 2-(hydroxylmethyl)pyridine(hmpH)ligand,formulated as[Co_(3)(hmp)_(6)(hmpH)]×2NO_(3)×3H_(2)O(ZTU-3)and[Co_(4)(hmp)_(4)(CH3CO_(2))2(H_(2)O)_(4)]×2NO_(3)(ZTU-4),have be...Two novel Co-based clusters with the 2-(hydroxylmethyl)pyridine(hmpH)ligand,formulated as[Co_(3)(hmp)_(6)(hmpH)]×2NO_(3)×3H_(2)O(ZTU-3)and[Co_(4)(hmp)_(4)(CH3CO_(2))2(H_(2)O)_(4)]×2NO_(3)(ZTU-4),have been successfully synthesized and structurally characterized.ZTU-3 features a triangular core geometry,while ZTU-4 exhibits a cuboidal core geometry.In addition,the magnetic properties of ZTU-3 and ZTU-4 are also all investigated.展开更多
Auxetic materials have been extensively studied for their design,fabrication and mechanical properties.These material systems exhibit unique mechanical characteristics such as high impact resistance,shear strength,and...Auxetic materials have been extensively studied for their design,fabrication and mechanical properties.These material systems exhibit unique mechanical characteristics such as high impact resistance,shear strength,and energy absorption capacity.Most existing auxetic materials are two-dimensional(2D)and demonstrate half-auxetic behavior,characterized by a negative Poisson's ratio when subjected to either tensile or compressive forces.Here,we present novel three-dimensional(3D)auxetic mechanical metamaterials,termed coupling chiral cuboids,capable of achieving negative Poisson's ratio under both tension and compression.We perform experiments,theoretical analysis,and numerical simulations to validate the wholly auxetic response of the proposed coupling chiral cuboids.Parametric studies are carried out to investigate the effects of structural parameters on the elastic modulus and Poisson's ratio of the coupling chiral cuboids.The results imply that the Poisson's ratio sign-switching from negative to positive can be implemented by manipulating the thickness of Z-shaped ligaments.Finally,the potential application of the coupling chiral cuboids as inner cores for impact-resistant sandwich panels is envisioned and validated.Test results demonstrate a remarkable 49.3%enhancement in energy absorption compared to conventional solidmaterials.展开更多
To enhance the efficiency of wind energy harvesters,aerodynamic modifications to bluff bodies prove highly effective.This study introduces two innovative galloping piezoelectric energy harvesters(GPEHs)equipped with t...To enhance the efficiency of wind energy harvesters,aerodynamic modifications to bluff bodies prove highly effective.This study introduces two innovative galloping piezoelectric energy harvesters(GPEHs)equipped with two symmetrical splitters on a cuboid bluff body:GPEH with upstream splitters(GPEH-US)and GPEH with downstream splitters(GPEH-DS).Wind tunnel experiments evaluated the impact of splitter angle and length on energy harvesting performance across varying wind speeds.The results indicate that larger splitter angles and shorter lengths are more favorable for energy harvesting in GPEH-US.The optimal configuration,determined as GPEH-US with α=90°,L=0.4D,reduces the threshold wind speed,expands the effective wind speed range for energy harvesting,and increases maximum voltage and power output by over 99%,301%,respectively,compared with conventional GPEH.Conversely,GPEH-DS are less effective for energy harvesting but demonstrate potential in vibration control applications.Computational fluid dynamics(CFD)simulations using the OpenFOAM toolbox qualitatively elucidate the physical mechanisms driving these results.A larger splitter angle enables secondary small-scale vortices(SV)to absorb more energy,accelerates boundary layer separation,intensifies and disorderly vortex shedding,enhances aerodynamic instability,and improves energy harvesting performance.展开更多
As a direct bandgap semiconductor, organic-inorganic lead halide perovskite (MAPbX3, MA = CH3NH3, X =Cl, Br, I) have been considered as promising materials for laser due to their excellent optoelectronic properties. T...As a direct bandgap semiconductor, organic-inorganic lead halide perovskite (MAPbX3, MA = CH3NH3, X =Cl, Br, I) have been considered as promising materials for laser due to their excellent optoelectronic properties. The perovskite materials with ID and 2D shapes were widely prepared and studied for Fabry-Perot mode and whispering-gallery-mode (WGM) microcavities, but cuboid-shape is rarely reported. In this work, we successfully fabricated single crystal cuboid-shaped MAPbBr3 perovskite w让h different morphologies, named microcuboid-MAPbBr3 (M-MAPbBr3) and multi-step-MAPbBr3 (MSMAPbBr3), via solvothermal method. Furthermore, the as-prepared *crystals excitonic recombination lifetime under different pumping energy density was studied by time-resolved photoiuminescence (TRPL). Based on controllable morphology and remarkable lasing properties, these cuboid shaped single crystal perovskite could be a promising candidate for small laser, and other optoelectronic devices.展开更多
The drag on non-spherical particles is an important basic parameter for multi-phase flows such as in biomass combustion, chemical blending, and mineral processing. Though there is much experimental research on such pa...The drag on non-spherical particles is an important basic parameter for multi-phase flows such as in biomass combustion, chemical blending, and mineral processing. Though there is much experimental research on such particles, there are few results for cuboids. This paper presents data for cuboids with a square base in static glycerin-water solutions of various volume concentrations. Complex motions were observed and characterized. A dimensionless expression is given for terminal velocity ut as a function of Archimedes number Ar which is used to develop an accurate correlation for friction factor CD. The accuracy of the correlation is 7.9% compared to experimental data in the literature. For both square plates and square rods, the terminal velocity per unit mass, ut/mp, was used to characterize the influence of narticle geometry on velocity, which was shown to be linear.展开更多
In this paper,we investigate the possibility of using the heterogeneous materials,with cuboid metallic inclusions inside a dielectric substrate(host)to control the effective permittivity.We find that in the gigahertz ...In this paper,we investigate the possibility of using the heterogeneous materials,with cuboid metallic inclusions inside a dielectric substrate(host)to control the effective permittivity.We find that in the gigahertz range,such a material demonstrates a significantly larger permittivity compared to the pure dielectric substrate.Three principal orientations of microscale cuboid inclusions have been taken into account in this study.The highest permittivity is observed when the orientation provides the largest polarization(electric dipole moment).The detrimental side effect of the metallic inclusion,which leads to the decrease of the effective magnetic permeability,can be suppressed by the proper choice of shape and orientation of the inclusions.This choice can in fact reduce the induced current and hence maximize the permeability.The dissipative losses are shown to be negligible in the relevant range of frequencies and cuboid dimensions.展开更多
In this work,a quadruple-band dielectric metamaterial absorber(MMA)was proposed and studied,which is composed of eight cuboid dielectric particles and a metallic ground plate.When electromagnetic wave is incident on t...In this work,a quadruple-band dielectric metamaterial absorber(MMA)was proposed and studied,which is composed of eight cuboid dielectric particles and a metallic ground plate.When electromagnetic wave is incident on the dielectric particles,dielectric particles act as resonators and produce abundant resonant modes,which can result in perfect absorption.In simulation,four absorption peaks are observed at 9.13,9.62,10.0 and 10.46 GHz with 88%,89%,100%and 96%,respectively.By adjusting geometry parameters of the dielectric particles,dielectric MMAs with different bands can be obtained.Further investigation shows that the absorption peaks can be changed by increasing the permittivity of the dielectric.Based on the designing technique of using simple cuboid dielectric particles directly acting as resonator,this work provides a simple method to construct multiband alldielectric MMA.展开更多
The nonlocal effect on the spontaneous emission of a silver cuboid dimer is investigated using a local analog model. Magnetic as well as electric dipole excitations are introduced to excite different gap modes. The no...The nonlocal effect on the spontaneous emission of a silver cuboid dimer is investigated using a local analog model. Magnetic as well as electric dipole excitations are introduced to excite different gap modes. The nonlocal response of electric and magnetic modes on various parameters of gap （width and refractive index） are investigated. Unidirectional radiation is achieved by the interaction between electric and magnetic modes in both local and nonlocal models. Compared to local simulations, the resonant wavelength is blue shifted and the spontaneous emission enhancement is weakened in the nonlocal model. The relative shifts of the resonant wavelengths get larger in smaller gaps with a higher refractive index.展开更多
基金supported by China Geological Survey Northeastern Tarim Aeromagnetic and Aerogravity comprehensive survey project(No.12120115039401)
文摘Most of the current computing methods used to determine the magnetic field of a uniformly magnetized cuboid assume that the observation point is located in the upper half space without a source. However, such methods may generate analytical singularities for conditions of undulating terrain. Based on basic geomagnetic field theories, in this study an improved magnetic field expression is derived using an integration method of variable substitution, and all singularity problems for the entire space without a source are discussed and solved. This integration process is simpler than that of previous methods, and final integral results with a more uniform form. AT at all points in the source-flee space can be calculated without requiring coordinate transformation; thus forward modeling is also simplified. Corresponding model tests indicate that the new magnetic field expression is more correct because there is no analytical singularity and can be used with undulating terrain.
基金Supported by National Natural Science Foundation of China (No. 50678116)National Key Technology R&D Program of China (No. 2006BAJ13B02)Tianjin Municipal Major Project of Application Foundation and Frontal Technology Research (No. 08JCZDJC19500)
文摘A simplified method is proposed for analyzing the overpressure history of an optional point on the walls of a closed cuboid due to its internal optional point-explosion. Firstly, the overpressure histories of all nodes on the walls of a cube with a side-length of 2 m are computed under a reference-charge explosion at each node of its inner space using the LS-DYNA software, and then are collected to form a reference database. Next, with the thought of the isoparametric finite element, an interpolating algori...
文摘Cuboid fractures due to the particular bone anatomy and its protected location in the midfoot are rare, and they are usually associated with complex injuries of the foot. Clinical examination to diagnose these fractures should be detailed and the differential diagnosis, especially in the case of vague symptoms, should include the exclusion of all lateral foot pain causes. Conventional radiographs do not always reveal occult fractures, which can be under diagnosed especially in children. In this case, further investigation including magnetic resonance imaging or scintigraphy may be required. The treatment of these injuries depends on the particular fracture characteristics. Non-displaced isolated fractures of the cuboid bone can be effectively treated conservatively by immobilization and by avoiding weight bearing on the injured leg. In the case of shortening of the lateral column> 3 mm or articular displacement > 1 mm, surgical management of the fracture is mandatory in order to avoid negative biomechanical and functional consequences for the foot and adverse effects such as arthritis and stiffness as well as painful gait. In this review, an update on diagnosis and management of cuboid fractures is presented.
基金The authors express their gratitude to the Natural Sciences and Engineering Research Council of Canada for financial support through a Discovery Grant(Grant No.06408).
文摘Vertical orthogonal joints are a common feature in shallow crustal rocks.There are several competing theories for their formation despite the ubiquity.We examined the exceptional exposures of orthogonal joints in flat-lying Ordovician limestone beds from the Havre-Saint-Pierre Region in Quebec,Canada(north shore of Saint-Lawrence River)to test conceptual models of joint formation in a natural setting.In the region,the spacing of cross-joints is consistently larger than the spacing of systematic joints by a factor of 1.5 approximately.The joint-spacing-to-bed-thickness ratios(s/t)are much larger in these beds(s/t=4.3 for systematic joints,and 6.4 for cross-joints)than those in higher strained strata along the south shore of the Saint-Lawrence River(s/t=1),highlighting the effect of tectonic strain in decreasing fracture spacing and block size.The high values of s/t indicate that cross-joint formation was unlikely caused by a switch from compression to tension once a critical s/t ratio for systematic joints was reached(as hypothesized in previous studies).We proposed a new model for the formation of orthogonal joint systems where the principal stress axes locally switch during the formation of systematic fractures.The presence of ladder-shaped orthogonal joints suggests a state of effective stress withσ_(1)^(∗)≫0>σ_(2)^(∗)>σ_(3)^(∗)and whereσ_(2)^(∗)-σ_(3)^(∗)is within the range of fracture strength variability at the time of fracture.This research provides a new mechanical model for the formation of orthogonal joint systems and cuboidal blocks.
文摘Traveling Salesman Problem (TSP) is one of the most widely studied real world problems of finding the shortest (minimum cost) possible route that visits each node in a given set of nodes (cities) once and then returns to origin city. The optimization of cuboid areas has potential samples that can be adapted to real world. Cuboid surfaces of buildings, rooms, furniture etc. can be given as examples. Many optimization algorithms have been used in solution of optimization problems at present. Among them, meta-heuristic algorithms come first. In this study, ant colony optimization, one of meta-heuristic methods, is applied to solve Euclidian TSP consisting of nine different sized sets of nodes randomly placed on a cuboid surface. The performance of this method is shown in tests.
基金supported by the National Natural Science Foundation of China(Grants 11872257,11572358).
文摘This paper investigates the flux-pinning-induced stress behaviors in a long superconducting slab with a central cuboid hole.The distribution of flux density is analytically derived for the critical current density of Kim model by considering the effects of the hole.The concentration of stress for both of the zero-field cooling(ZFC)and the field cooling(FC)magnetization processes are investigated through numerical simulation by using finite element method.The results indicate the potential failure mode varies with the height-width ratio and the dimensions of the hole.Different to the case of infinite hole height,the stress concentration behavior for the FC process is more critical when the dimensions of the hole are similar.The findings in this paper are useful for understanding of the degrade mechanism of superconductor in service and the design of new system.
基金Supported by the National Natural Science Foundation of China(21861044 and 21601137)the Project funded by China Postdoctoral Science Foundation(2018M633426)the Project funded by Yunnan Province Postdoctoral Science Foundation
文摘Two novel Co-based clusters with the 2-(hydroxylmethyl)pyridine(hmpH)ligand,formulated as[Co_(3)(hmp)_(6)(hmpH)]×2NO_(3)×3H_(2)O(ZTU-3)and[Co_(4)(hmp)_(4)(CH3CO_(2))2(H_(2)O)_(4)]×2NO_(3)(ZTU-4),have been successfully synthesized and structurally characterized.ZTU-3 features a triangular core geometry,while ZTU-4 exhibits a cuboidal core geometry.In addition,the magnetic properties of ZTU-3 and ZTU-4 are also all investigated.
基金support of the National Key R&D Program of China(2023YFC3008100)the Startup Fund of the One-Hundred Talent Program at the Zhejiang University.A.H.A.acknowledges the support of the National Science Foundation(NSF)CAREER award(CMMI-2235494).
文摘Auxetic materials have been extensively studied for their design,fabrication and mechanical properties.These material systems exhibit unique mechanical characteristics such as high impact resistance,shear strength,and energy absorption capacity.Most existing auxetic materials are two-dimensional(2D)and demonstrate half-auxetic behavior,characterized by a negative Poisson's ratio when subjected to either tensile or compressive forces.Here,we present novel three-dimensional(3D)auxetic mechanical metamaterials,termed coupling chiral cuboids,capable of achieving negative Poisson's ratio under both tension and compression.We perform experiments,theoretical analysis,and numerical simulations to validate the wholly auxetic response of the proposed coupling chiral cuboids.Parametric studies are carried out to investigate the effects of structural parameters on the elastic modulus and Poisson's ratio of the coupling chiral cuboids.The results imply that the Poisson's ratio sign-switching from negative to positive can be implemented by manipulating the thickness of Z-shaped ligaments.Finally,the potential application of the coupling chiral cuboids as inner cores for impact-resistant sandwich panels is envisioned and validated.Test results demonstrate a remarkable 49.3%enhancement in energy absorption compared to conventional solidmaterials.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52271282,51909189 and 52277227)supported by the Open fund of Key Laboratory of Low-grade Energy Utilization Technologies and Systems,Ministry of Education of China,Chongqing University,(Grant No.LLEUTS-202410)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515010846)the Shenzhen Science and Technology Programme(Grant Nos.RCYX20231211090210018,WDZC20231125203917001)the Tsinghua Shenzhen International Graduate School via the Scientific Research Start-Up Funds(Grant No.QD2021023C).
文摘To enhance the efficiency of wind energy harvesters,aerodynamic modifications to bluff bodies prove highly effective.This study introduces two innovative galloping piezoelectric energy harvesters(GPEHs)equipped with two symmetrical splitters on a cuboid bluff body:GPEH with upstream splitters(GPEH-US)and GPEH with downstream splitters(GPEH-DS).Wind tunnel experiments evaluated the impact of splitter angle and length on energy harvesting performance across varying wind speeds.The results indicate that larger splitter angles and shorter lengths are more favorable for energy harvesting in GPEH-US.The optimal configuration,determined as GPEH-US with α=90°,L=0.4D,reduces the threshold wind speed,expands the effective wind speed range for energy harvesting,and increases maximum voltage and power output by over 99%,301%,respectively,compared with conventional GPEH.Conversely,GPEH-DS are less effective for energy harvesting but demonstrate potential in vibration control applications.Computational fluid dynamics(CFD)simulations using the OpenFOAM toolbox qualitatively elucidate the physical mechanisms driving these results.A larger splitter angle enables secondary small-scale vortices(SV)to absorb more energy,accelerates boundary layer separation,intensifies and disorderly vortex shedding,enhances aerodynamic instability,and improves energy harvesting performance.
基金supported by the National Natural Science Foundation of China(11674023,51331002,51622205,61675027,61505010,51502018,51525202 and 51432005)111 Project(B170003)+2 种基金the National Key Research and Development Program of China(2016YFA0202703)Beijing Natural Science Foundation(4181004 and 4182080)the ‘‘Thousand Talents” Program of China for Pioneering Researchers and Innovative Teams(U1404619)
文摘As a direct bandgap semiconductor, organic-inorganic lead halide perovskite (MAPbX3, MA = CH3NH3, X =Cl, Br, I) have been considered as promising materials for laser due to their excellent optoelectronic properties. The perovskite materials with ID and 2D shapes were widely prepared and studied for Fabry-Perot mode and whispering-gallery-mode (WGM) microcavities, but cuboid-shape is rarely reported. In this work, we successfully fabricated single crystal cuboid-shaped MAPbBr3 perovskite w让h different morphologies, named microcuboid-MAPbBr3 (M-MAPbBr3) and multi-step-MAPbBr3 (MSMAPbBr3), via solvothermal method. Furthermore, the as-prepared *crystals excitonic recombination lifetime under different pumping energy density was studied by time-resolved photoiuminescence (TRPL). Based on controllable morphology and remarkable lasing properties, these cuboid shaped single crystal perovskite could be a promising candidate for small laser, and other optoelectronic devices.
基金supported by the Major Program of the National Natural Science Foundation of China with Grant No. 10632070
文摘The drag on non-spherical particles is an important basic parameter for multi-phase flows such as in biomass combustion, chemical blending, and mineral processing. Though there is much experimental research on such particles, there are few results for cuboids. This paper presents data for cuboids with a square base in static glycerin-water solutions of various volume concentrations. Complex motions were observed and characterized. A dimensionless expression is given for terminal velocity ut as a function of Archimedes number Ar which is used to develop an accurate correlation for friction factor CD. The accuracy of the correlation is 7.9% compared to experimental data in the literature. For both square plates and square rods, the terminal velocity per unit mass, ut/mp, was used to characterize the influence of narticle geometry on velocity, which was shown to be linear.
基金The project was funded by the EPSRC Grant(EP/101490X/1)on synthetic materials and metamaterials studies.
文摘In this paper,we investigate the possibility of using the heterogeneous materials,with cuboid metallic inclusions inside a dielectric substrate(host)to control the effective permittivity.We find that in the gigahertz range,such a material demonstrates a significantly larger permittivity compared to the pure dielectric substrate.Three principal orientations of microscale cuboid inclusions have been taken into account in this study.The highest permittivity is observed when the orientation provides the largest polarization(electric dipole moment).The detrimental side effect of the metallic inclusion,which leads to the decrease of the effective magnetic permeability,can be suppressed by the proper choice of shape and orientation of the inclusions.This choice can in fact reduce the induced current and hence maximize the permeability.The dissipative losses are shown to be negligible in the relevant range of frequencies and cuboid dimensions.
基金the Natural Science Foun-dation of China(NSFC)through the Grant Nos.11504428,61671466 and 11274389the Natural Science Foundation of Shaanxi Province under Grant 2016JM6026the Inno-vative Team of Shaanxi Province(No.2014KCT-05).
文摘In this work,a quadruple-band dielectric metamaterial absorber(MMA)was proposed and studied,which is composed of eight cuboid dielectric particles and a metallic ground plate.When electromagnetic wave is incident on the dielectric particles,dielectric particles act as resonators and produce abundant resonant modes,which can result in perfect absorption.In simulation,four absorption peaks are observed at 9.13,9.62,10.0 and 10.46 GHz with 88%,89%,100%and 96%,respectively.By adjusting geometry parameters of the dielectric particles,dielectric MMAs with different bands can be obtained.Further investigation shows that the absorption peaks can be changed by increasing the permittivity of the dielectric.Based on the designing technique of using simple cuboid dielectric particles directly acting as resonator,this work provides a simple method to construct multiband alldielectric MMA.
基金supported by the National Natural Science Foundation of China under Grant Nos.11574293,11274293,and 61377053
文摘The nonlocal effect on the spontaneous emission of a silver cuboid dimer is investigated using a local analog model. Magnetic as well as electric dipole excitations are introduced to excite different gap modes. The nonlocal response of electric and magnetic modes on various parameters of gap （width and refractive index） are investigated. Unidirectional radiation is achieved by the interaction between electric and magnetic modes in both local and nonlocal models. Compared to local simulations, the resonant wavelength is blue shifted and the spontaneous emission enhancement is weakened in the nonlocal model. The relative shifts of the resonant wavelengths get larger in smaller gaps with a higher refractive index.
