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- 实验方案
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[IEEE 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Athens, Greece (2018.7.4-2018.7.6)] 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Depth Estimation and Ray Tracing Model Selection of Buried Utilities on Ground Penetrating Radar Data
摘要： When assessing a target depth from a Ground Penetrating Radar (GPR) image, one typically assumes a certain wave propagation model as well as the model parameters (typically the dielectric of the medium). While much work has been conducted on the automatic inference of the model parameters, not much work has been performed testing the validity of the model itself. The work presented here closes this gap for a low-frequency GPR system (350 MHz center frequency). It compares the measurement, taken from known targets at known depths, with different ray propagation models. It also presents a novel method for efficiently estimating the depth of a target without using any knowledge of the medium's wave propagation speed, or even the time of the signal's emission from the transmitter (time zero). Experiments on 26 targets of varying depths showed an averaged estimation error of less than 0.5%, with a standard deviation of 3% using this robust and efficient method.
关键词： GPR,Wave Propagation,Ray Tracing Models,Target Depth Estimation
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 5G World Forum (5GWF) - Silicon Valley, CA, USA (2018.7.9-2018.7.11)] 2018 IEEE 5G World Forum (5GWF) - A Hexagonal Grid Based Human Blockage Model for the 5G Low Terahertz Band Communications
摘要： Users continuously demand higher connection speeds and data traffic from wireless communication networks. The newly required network capacity should be provided by higher frequency bands, because legacy sub-6 GHz bands are already operating using advanced communication techniques that provide very high spectral efficiencies. Consequently, millimeter wave communication standards are either complete or ongoing, and general submillimeter wave applications are next in line. Accordingly, this paper proposes a motion model in hexagonal grid of a person carrying a user equipment. Electromagnetic wave blockage analyses by utilizing channel characteristics of the low-THz band are presented. Lastly, the communication and blockage probabilities of an exemplary system are both theoretically examined and numerically simulated.
关键词： Markov processes,submillimeter wave propagation,numerical simulation,mathematical model,submillimeter wave communication,5G mobile communication
更新于2025-09-23 15:21:01
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Highly accurate space-time coupled least-squares finite element framework in studying wave propagation
摘要： Simulation of stress wave propagation through solid medium is commonly carried using Galerkin weak-form cast over decoupled space and time domains. In this paper, accuracy of this commonly utilized framework is compared to that of the variationally-consistent least-squares form of the wave equation cast over space-time domain. The two formulations are tested for numerical dispersion and numerical diffusion, through two test cases. The first case studies the dispersion in harmonic shear wave propagation through a soil column over a wide range of forcing frequencies. The second test case investigates numerical diffusion in an axial wave propagation generated by constant force; which is removed after a certain time to allow free vibration to take place. Low numerical dispersion and numerical diffusion as well as high rates of convergence are the main advantages of the coupled least-squares (CLS) computational framework; when compared to the decoupled Galerkin (DG) framework. Based on studies presented here, CLS has low dispersion; yielding errors with one to two orders of magnitude less than that of DG. Also, the numerical diffusion present in DG framework causes a %40 error in DG’s prediction of the stress-wave intensity. Furthermore, accumulative error during evolution is virtually nonexistent for CLS, whereas, the error steadily increases as the solution evolves in DG framework. It is also demonstrated that CLS feature of temporal meshing allows for faster computations.
关键词： Shear wave propagation,Variational-consistency,Higher continuity hierarchical finite elements,Numerical diffusion,Least squares,Impact wave propagation,Space-time coupled,Numerical dispersion,Wave equation
更新于2025-09-23 15:19:57
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Measurement of shallow defects using noncontact broadband leaky Lamb wave produced by pulsed laser with ultrasound microphone
摘要： In this study, we propose a convenient noncontact laser ultrasonic system to detect small cracks and estimate the wall-thinning defects of thin plates. The system uses an ultrasound microphone to detect the energy leaked from the broadband Lamb-wave propagation. The broadband characteristics of this wave, produced by a pulsed laser, are used to measure the wavenumber. The cumulative standing-wave energy (CSWE) method that uses a traveling wave is implemented to verify the feasibility of the ultrasound microphone. The excitation energy of the pulsed laser was insufficient compared with that of the continuous-wave contact actuator. Therefore, a modified local wavenumber estimation (LWE) method is proposed, which reconstructs several LWE images at various frequencies. These images are averaged to calculate thicknesses of the plate and defects, by using the wavenumber–thickness relationship. The method has an error of 2.84% and 7.7% for the thickness of the plate and defect area, respectively.
关键词： cumulative standing-wave energy (CSWE),ultrasound microphone,local wavenumber estimation (LWE),wall-thinning defects,noncontact laser ultrasonic system,broadband Lamb-wave propagation,small cracks
更新于2025-09-23 15:19:57
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Direct Chip-to-Waveguide Transition Realized with Wire Bonding for 140 GHz to 220 GHz G-Band
摘要： This work presents a method to realize a direct chip-to-waveguide transition by means of commercial wire-bonding tools. A straight E-field probe is formed by a freely suspended bondwire and mounted to a standard RF pad on-chip. In contrast to conventional approaches, no additional dedicated substrate or large integrated radiating structure are necessary. A preliminary analysis is performed to illustrate the basic feasibility and a WR-05 prototype module, with dedicated test chip, is designed and optimized for a frequency range of 140 GHz to 220 GHz (G-Band). The measured return loss of a back-to-back configuration is above 10 dB, while the deembedded absolute loss of a single transition is between 0.4 dB and 1 dB, both within the complete waveguide bandwidth of 80 GHz. The demonstrated performance is very well suited to ultra-wideband communication systems or general-purpose mm-wave components.
关键词： WR-5,transition,bondwire,packaging,mm-wave,propagation,matching,waveguide,G band
更新于2025-09-23 15:19:57
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Laser array beam propagation through liver tissue
摘要： Laser array beam propagating through mouse liver tissue is investigated. The turbulence power spectrum of the liver tissue is employed in the extended Huygens–Fresnel method to obtain an optical intensity pro?le and beam broadening at the observation point in biological liver tissue. Variations of the beam pro?le and the beam broadening are simulated based on the number of beamlets, source size, wavelength and the ring radius of the array. A biological tissue, illuminated by the laser array beam, exhibits different beam pro?les and beam spot radius variations when the number of beamlets, source size, wavelength and the ring radius of the laser array beam are varied. Examining these variations observed in the propagated optical beam and comparing them with the test cases, abnormalities such as cancer and tumor in a biological liver tissue can be diagnosed.
关键词： Optical wave propagation,Tissue turbulence,Effective beam spot radius,Optical intensity,Optical imaging
更新于2025-09-23 15:19:57
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[IEEE 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Miramar Beach, FL (2018.8.22-2018.8.24)] 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Implementing Photonic Crystals, Instead of Metamaterials, in the Media of Transformation Optics-based Devices
摘要： Extending Transformation Optics in optical range is challenging because of losses in metamaterials. We propose, instead, to use dielectric photonic crystals capable of supporting superluminal wave propagation and realizing spatial dispersion of refractive index values. Implementing these materials in cylindrical invisibility cloaks is demonstrated.
关键词： spatial dispersion of indices,superluminal wave propagation,anisotropic photonic crystals
更新于2025-09-23 15:19:57
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All-optical and dynamic manipulation of surface plasmon polaritons by tailoring the polarization state of incident light
摘要： A hybridly polarized vector beam comprising linear, elliptical, and circular polarizations at the beam cross-section is investigated for the manipulation of surface plasmon polaritons (SPPs). Unlike the well-known radially- or azimuthally-polarized beam that only includes linear polarization, this hybridly polarized beam provides increased optical degrees of freedom, which assist in controlling the excitation, orientation, and distribution of the focused SPPs excited in a high-numerical-aperture microscopic configuration. Many fascinating SPP patterns can be easily obtained, such as sharp peaks, multi-foci, donuts, and dark polygons. Those novel properties might be of great value in applications such as plasmonic tweezers.
关键词： electromagnetic wave propagation,polarization,interference,optical properties of surfaces
更新于2025-09-23 15:19:57
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Understanding strong knocking mechanism through high-strength optical rapid compression machines
摘要： Strong knocking combustion has become the greatest challenge for advanced internal combustion engines to pursue thermal efficiency limits at high power density conditions. Arising from enclosed space and extreme combustion situations, the fundamental mechanism for strong knocking combustion has still not been fully understood. In this study, synchronization measurement was performed through simultaneous pressure acquisition and high-speed direct photography, and knocking experiments were comparatively conducted under spark-ignition (SI) and compression-ignition (CI) conditions in a high-strength optical rapid compression machine (RCM) with flat piston design. Strong knocking phenomena were reproduced through varying initial thermodynamic conditions, and localized autoignition (AI) initiation and reaction wave evolutions were visualized, companied by synchronous pressure and temperature trajectories. The results show that compared with initial temperature, initial pressure and equivalence ratio exhibit greater influence on the variations of knocking severity. The weighting of different contributors can be further quantified by an effective energy density that shows positive but nonlinear correlations with knocking severity. However, the distinctions between CI and SI knocking characteristics at identical effective energy density also reflect the essential role of the interplay between primary flame propagation and end-gas AI progress. Visualized combustion images show that through improving end-gas thermodynamic state and reactivity sensitivity, the primary flame propagation can enhance localized AI initiation and secondary intensive AI evolutions, facilitating combustion mode transitions into developing detonation. The significant influence of primary flame propagation is diminished until ignition delay time becomes sufficiently short. Finally, with estimated thermal heterogeneities in flat-piston RCM configurations, the ignition modes of strong knocking cycles are quantified by a non-dimensional ignition regime diagram, and favorable scaling agreements with strong and mixed ignition regimes are observed.
关键词： Rapid compression machine,Effective energy density,Reaction wave propagation,Strong knocking combustion,Ignition regime
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