- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Examination of internal stress by photoelasticity in laser cleaving of glass
摘要： Laser cleaving is a glass-cutting technique in which thermal stress induced by laser heating and cooling produces cracks in the glass. Stress measurement during the laser cleaving process is critical in elucidating the crack-propagation mechanism and solving the problems of the laser cleaving method. In this study, we measured the birefringence retardation using a high-speed polarization camera and evaluated the relevance and accuracy of the measured values by comparing them with the results of a numerical calculation. The birefringence retardation at the crack tip was also observed in the experimental process. For the experiment, a soda lime glass was cleaved using CO2 laser irradiation. Then, the birefringence retardation and azimuthal angle obtained using the polarization camera were compared with the numerical calculation results. The birefringence retardation around the crack tip corresponded with that of the deformation caused by mode I. The crack propagation was arrested when the crack tip approached the edge of the glass. The birefringence retardation observed using the polarization camera confirmed that the mode I deformation decreased as the crack approached the edge.
关键词： Glass,Laser cleaving,Crack propagation,Numerical calculation,Photoelasticity
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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Error Budget for Geolocation of Spectroradiometer Point Observations from an Unmanned Aircraft System
摘要： We investigate footprint geolocation uncertainties of a spectroradiometer mounted on an unmanned aircraft system (UAS). Two microelectromechanical systems-based inertial measurement units (IMUs) and global navigation satellite system (GNSS) receivers were used to determine the footprint location and extent of the spectroradiometer. Errors originating from the on-board GNSS/IMU sensors were propagated through an aerial data georeferencing model, taking into account a range of values for the spectroradiometer field of view (FOV), integration time, UAS flight speed, above ground level (AGL) flying height, and IMU grade. The spectroradiometer under nominal operating conditions (8° FOV, 10 m AGL height, 0.6 s integration time, and 3 m/s flying speed) resulted in footprint extent of 140 cm across-track and 320 cm along-track, and a geolocation uncertainty of 11 cm. Flying height and orientation measurement accuracy had the largest influence on the geolocation uncertainty, whereas the FOV, integration time, and flying speed had the biggest impact on the size of the footprint. Furthermore, with an increase in flying height, the rate of increase in geolocation uncertainty was found highest for a low-grade IMU. To increase the footprint geolocation accuracy, we recommend reducing flying height while increasing the FOV which compensates the footprint area loss and increases the signal strength. The disadvantage of a lower flying height and a larger FOV is a higher sensitivity of the footprint size to changing distance from the target. To assist in matching the footprint size to uncertainty ratio with an appropriate spatial scale, we list the expected ratio for a range of IMU grades, FOVs and AGL heights.
关键词： geolocation,error propagation,UAV,spectroradiometer,footprint,UAS,aerial spectroscopy
更新于2025-09-19 17:15:36
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Turbulence-induced power drops as extreme events
摘要： Free-space optical communication links through the atmosphere are degraded mainly by the action of scintillation and beam wander. Both phenomena are responsible for fiber coupling misalignments at the receiver. Henceforth, the signal is corrupted by random power drops, which can be identified as extreme events, with particular statistical properties. In this work, we performed experiments and simulations to gain insight into understanding these extremes events and their relation with scintillation and wander at a receiver. Particularly, this sequence also inherits the same long term correlations of the original data.
关键词： Atmospheric propagation,Atmospheric optics,Turbulence
更新于2025-09-19 17:15:36
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Design of a High-Gain Millimeter-Wave Antenna Using Characteristic Modes
摘要： This paper proposes the use of the Theory of Characteristic Modes to aid the design of high-gain antennas for mm-wave applications. A new lens antenna operating in the 19 to 22 GHz band is proposed. The lens consists of two metallic rings distributed in two layers and illuminated by a square aperture. The Theory of Characteristic Modes is used to analyze the proposed antenna in order to provide insight into the radiation characteristics of the structure. The proposed antenna has been optimized, obtaining a large bandwidth and a maximum directivity of 11.19 dBi at 22 GHz.
关键词： propagation,characteristic modes,high gain,Lens antenna
更新于2025-09-19 17:15:36
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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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[IEEE 2018 International Conference on Electronics, Control, Optimization and Computer Science (ICECOCS) - Kenitra, Morocco (2018.12.5-2018.12.6)] 2018 International Conference on Electronics, Control, Optimization and Computer Science (ICECOCS) - Agent based simulation of electromagnetic waves propagation using the FDTD method
摘要： In recent years, multi-agent systems have taken an increasingly important place in computer science, whether in the field of artificial intelligence, distributed systems, robotics, or even in the environmental sciences, offering the opportunity to directly represent individuals, their behaviors and their interactions. The objective of this paper is the application of the techniques of the multi-agent approach in the simulation of the propagation of electromagnetic waves by FDTD method using Netlogo.
关键词： Electromagnetic,Propagation,FDTD,Multi-agents
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Singapore (2018.7.16-2018.7.19)] 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Integrating EOP/EOFM as a Complimentary Localization Technique for Open Via/Contact
摘要： The paper describes as integrated technique of Electro Optical Frequency Mapping (EOFM) and Electro Optical Probing (EOP) to localize open failure mode with traditional FA analysis approach. The technique was performed in analog devices on advanced SOI-based circuits. Two case studies were presented to demonstrate on how the newly introduced fault localization techniques work. These techniques can help to isolate or narrow down the suspected failing components.
关键词： Open via,Propagation delay,Optical Beam Induced Resistance Change,Photon Emission Microscopy,Electro Optical Probing,Electro Optical Frequency Mapping
更新于2025-09-19 17:15:36
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Spatial Carrierless Amplitude and Phase Modulation Technique for Visible Light Communication Systems
摘要： Spatial carrierless amplitude and phase modulation (S-CAP) technique is developed in this paper as a physical layer solution to improve the spectral efficiency of the conventional CAP scheme while preserving its low-complexity transceiver design. The S-CAP technique is proposed and investigated for systems employing the visible light communication technology. An analytical expression for the joint detection of the spatial and signal bits for the user equipment experiencing line-of-sight propagation (LOS) is derived and validated via simulation. The effects of the multipath propagation and user mobility on the bit-error-rate (BER) performance of the proposed S-CAP are also investigated. It is found that the BER performance of the S-CAP in LOS is dictated by the minimum of the channel gains hmin, the signal constellation points, and the channel gain dissimilarity, Δ|h|. The power factor imbalance (PFI) and multiple photodetectors (PDs) are then introduced to improve the performance and mitigate the channel impairments. The use of the PFI and PDs in LOS results in the signal-to-noise gain of 33.5 and 43 dB, respectively. The proposed scheme is thus a novel implementation of the CAP in a multiple-input–multiple-output system and demonstrates its potential as a suitable physical layer solution for the VLC technology.
关键词： multiple-input–multiple-output (MIMO),visible light communication (VLC),Carrierless amplitude and phase modulation (CAP),multipath propagation,spatial modulation (SM)
更新于2025-09-19 17:15:36