- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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The Application of Least-Squares Finite Element Method to Simulate Wave Propagation in Bianisotropic Media
摘要： The finite element method (FEM) has been one of the major numerical techniques for electromagnetics (EM) ever since the introduction of the spurious-free edge element. On the other hand, a so-called least-squares finite element method (LSFEM) is becoming increasingly popular due to its unique properties. For instance, the generated stiffness matrix is positive definite. Effort has been made to apply this node-element-based LSFEM to model EM problems, mostly in the theoretical aspect. In this paper, we will use normalized Maxwell’s equations incorporated with the constitutive relations of bianisotropic media, which represents the most general cases in the linear regime. Subsequently, the corresponding variational formulation is derived, followed by the generation of matrix systems. We then implement and validate various boundary conditions. Further we apply this scheme to simulate wave scattering in the presence of bianisotropic media that are categorized into 3 types. A good convergence rate and agreement between the LSFEM results and the referenced solutions has been achieved, which proves the Lagrange-element-based LSFEM as a feasible alternative to the edge-element-based FEM currently used in EM modeling.
关键词： Electromagnetic metamaterials,Electromagnetic propagation,Finite element analysis
更新于2025-09-19 17:15:36
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Design of terahertz photoconductive antenna arrays based on defective photonic crystal substrates
摘要： In this paper, arrays of two different terahertz (THz) antennas based on defective photonic crystal (DPC) substrates are proposed and their radiation characteristics are investigated by using full-wave simulation. We show that employing DPC substrates in THz photoconductive antenna (PCA) arrays reduces the amount of power coupled to the substrate surface waves and, as a result, decreases the mutual coupling between the elements of the antenna array and increases the directivity in the boresight direction. By studying 1 × 2 arrays of bowtie and four-leaf-clover-shaped antennas, we show that either the improvement of directivity in a broad bandwidth or the enhancement of photomixer antenna impedance at a resonant frequency can be considered in the design of the DPC substrate. Therefore, the proposed approach can significantly improve the efficiency and radiation performance of THz photomixer antennas resulting in an improved effective THz radiated power in the desirable direction. The proposed DPC substrate can be considered as a way to realize sub-millimeter-sized dielectric resonator antennas at terahertz frequencies. In addition, this cost-effective technique can reduce the necessity of exploiting hyper-hemispherical Si lenses by overcoming the adverse effects of the thick substrate which is of prime importance in PCA arrays from a practical viewpoint.
关键词： Arrays,Defective photonic crystal substrate,Propagation waves,Terahertz antennas
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - Suppression of Propagation Losses in TC SAW Resonators Using Thin Plates of LiTaO3 Bonded to Quartz Substrates
摘要： Suppression of Propagation Losses in Thin-Film Lithium Niobate Optical Waveguides
关键词： Lithium Niobate,Thin-Film,Optical Waveguides,Quasi-Phase Matching,Propagation Losses
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE Conference on Virtual Reality and 3D User Interfaces (VR) - Tuebingen/Reutlingen, Germany (2018.3.18-2018.3.22)] 2018 IEEE Conference on Virtual Reality and 3D User Interfaces (VR) - AR in a Large Area Through Instance Recognition with Hybrid Sensors
摘要： This paper presents the concept of instant recognition with access points and vision for realizing time in a large indoor environment. The proposed method consists of constructing a database from data of various viewpoints and angles while taking images of the same object, and instant recognition through vision by comparing the input image with the database. The proposed method was evaluated through experiments, and the results show that recognition accuracy and computational time are less than our previous work using only vision.
关键词： INS,Affinity Propagation,Access Point,Image Retrieval
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM) - Nagoya (2018.8.29-2018.8.31)] 2018 IEEE International Workshop on Electromagnetics:Applications and Student Innovation Competition (iWEM) - A Computational Study of Indoor-to-Outdoor Propagation in Office Environment at 2.4 GHz and 5.2 GHz Bands
摘要： In this paper we predict indoor-to-outdoor radio wave propagation characteristics at frequencies of 2442 MHz and 5200 MHz using a large-scale computer simulation. A wireless LAN access point is assumed to be installed in office buildings. We discuss path loss and shadow fading in an observation plane outside the office building which faces an exterior concrete wall with windows. It is clarified from computation results that the path loss at 5200 MHz is smaller than that at 2442 MHz, and that the shadow fading distribution is expressed by a superposition of components passing through the windows and the concrete walls.
关键词： indoor-to-outdoor propagation,path loss,FDTD method,wireless LAN,shadowing
更新于2025-09-19 17:15:36
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Terahertz and Visible Probing of Particles Suspended in Air
摘要： The attenuation of air suspended particles is measured with a terahertz time-domain spectrometer (THz-TDS). Simultaneously, the attenuation at a wavelength of 650 nm is probed with a laser diode. On the one hand, this dual measurement allows a direct assessment of the visibility evolution in the THz range compared to the visible range. On the other hand, this setup provides an estimation of the scattering strength and the density of particles. Using the Mie theory, the method is successfully applied to experimentally characterize the refractive index of sand grains and glass beads. The refractive indices of sand grains and glass beads, average over the acquisitions, are 1.67 and 2.54, respectively. The estimation of the scattering properties of sand grains are crucial to evaluate the performance of THz systems to image through brownout clouds that are created by helicopter rotors when landing in arid areas.
关键词： THz scattering,propagation,refractive index,THz time-domain spectroscopy
更新于2025-09-19 17:15:36
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On dispersion relations in smart laminated fiber-reinforced composite membranes considering different piezoelectric coupling effects
摘要： Wave propagation characteristics are determined for smart laminated fiber-reinforced composite cylindrical membrane shells with different piezoelectric coupling effects. Wave motion equations are derived using the membrane shell model. By solving an eigenvalue problem, dispersion curves of the wave motion are obtained for different axial and circumferential wave numbers. The effects of piezoelectric coupling, fiber orientation, stacking sequence, and material properties of the host shell on wave behaviors are investigated. The results of this paper can be used for studies on dynamic stability of piezoelectric coupled laminated fiber-reinforced composite shell structures and in design of smart structures with the piezoelectric materials for the applications of damage detection and structural health monitoring.
关键词： dispersion,piezoelectric,Composite,wave propagation,membrane shell
更新于2025-09-19 17:15:36
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[Communications in Computer and Information Science] VLSI Design and Test Volume 892 (22nd International Symposium, VDAT 2018, Madurai, India, June 28-30, 2018, Revised Selected Papers) || Performance Analysis of Graphene Based Optical Interconnect at Nanoscale Technology
摘要： In the modern technology era, interconnect is the key element for designing integrated circuits that provides on-chip and off-chip communication path for various systems. The primary challenges for modeling interconnect are reduced propagation delay, power dissipation, and its power delay product at advanced technology. This paper critically addresses the performance of optical interconnects using equivalent electrical model that comprises of different composite materials. Using industry standard HSPICE, the propagation delay and power dissipation characteristics of graphene nanoribbon have been compared with other composite materials. It has been observed that the propagation delay for graphene nanoribbon can be improved by 99.91% as compared to other composite materials. The power delay product of the proposed graphene based interconnect model is 59.73% lesser compared to other composite materials at 22 nm technology node.
关键词： Power delay product (PDP),Graphene nanoribbons,Propagation delay,Optical interconnect,Power dissipation
更新于2025-09-19 17:15:36
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Analysis of vulnerability propagation for the all-optical network based on Bio-PEPA
摘要： Aiming at the vulnerability propagation of all-optical networks, combining with the characteristics of the all-optical network, a formal modeling and analysis method for vulnerability propagation based on Bio-PEPA is proposed in this paper. First of all, the main characteristics that influence the vulnerability propagation are analyzed. Then, the optical fibers, optical amplifiers and optical switches are abstract into three different clusters, and the propagation behavior of vulnerability in intra-cluster and inter-cluster are described accurately. In addition, Ordinary Differential Equations is used for model parsing. Finally, through testing the main factors of vulnerability propagation, such as the number of nodes with potential vulnerability, system detection and repair rate, it is shown that the model constructed in this paper can reflect the vulnerability propagation trend of all-optical networks reasonably. At the same time, the proposed method can avoid the state space explosion problem of traditional modeling methods.
关键词： Bio-PEPA,Formal modeling,All-optical network,Vulnerability propagation
更新于2025-09-19 17:15:36
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Use of steady-state imaging setup for assessing the internal optical properties of non-spherical apple samples
摘要： The aim of this paper was to retrieve the absorption (μa) and reduced scattering (μ's) coefficients of whole apples which exhibit a complex shape. The effect of the local boundary curvature on the retrieved optical properties was investigated by means of numerical simulations and measurements carried out at the wavelength of 633 nm. A first attempt was made by performing Monte Carlo simulations on an apple-like spheroid model covered with a thin skin layer of thickness 80 μm. Monte Carlo data were then analyzed to depict the changes of photon densities, diffusively reflected images and optical properties as a function of the light source location over the surface of such target. Second, spatially-resolved backscattered images were acquired from 207 ‘Royal Gala’, and the values of μa and μ's were retrieved using an inverse algorithm to fit the scattering profiles with a diffusion theory model, in a selected fitting range of 2.8–10 mm. The results confirm the theoretical prediction and show that the absorption coefficient μa may be overestimated, while the reduced scattering coefficient μ's is slowly changed when the measurements are performed on these apple species. Finally, experiments carried out on 200 apples still show that μ's is negatively correlated to the fruit firmness with a correlation coefficient (r) of 0.63. The spatially-resolved technique provides an efficient means for measuring the optical properties of fruits, and may be also useful for assessing the apple firmness.
关键词： Diffusion theory,Optical properties,Light propagation,Imaging system,Apple firmness
更新于2025-09-19 17:15:36