- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Laser Optoacoustic Method for Quantitative Porosity Assessment of Carbon Fiber Reinforced Plastic Composites Based on Acoustic Impedance Measurement
摘要： A method for measuring the acoustic impedance for the assessment of the porosity of carbon fiber reinforced plastic composites using laser thermo-optical excitation of longitudinal acoustic waves is proposed and experimentally realized. The acoustic impedance of the test sample is measured from the magnitude of the antiderivative ultrasonic pulse reflected from the immersion liquid–sample interface. A method for calculating the porosity of carbon fiber plastic composites based on the measured acoustic impedance is presented. Composite samples with three different carbon fiber layers stacking schemes were investigated. It is shown that in the studied composites, the local porosity distribution is nonuniform along the fiber stacking plane. The porosity value, averaged from optoacoustic measurement results, actually coincides with X-ray tomography data within the error limits. The presented method for determining porosity does not require determining the volume and mass of the studied object and can be used for investigation of composite structures with complex shapes.
关键词： porosity,laser optoacoustic method,polymer composites,longitudinal acoustic waves
更新于2025-09-23 15:19:57
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High resonance frequency in a coupled cavity DFB-LD with two phase-shifts
摘要： To realize a single-longitudinal-mode laser diode (LD) with high speed direct-modulation, a coupled cavity DFB-LD with two phase-shifts is proposed. From simulated results, it is expected that the resonance frequency of 71.3 GHz and the 3-dB down bandwidth of 95.9 GHz are obtained when the injected current is 3.075 times the threshold current. The resonance frequency for a main-mode is enhanced by an interaction between the main-mode and sub-mode. This interaction is called photon–photon resonance. The proposed coupled cavity DFB-LD is composed of two regions which are connected in series. Both regions have phase-shifted gratings. The phase-shift of the first region is ? π; the phase-shift of the second region is ? 0.9π. A phase-shift is not introduced at the interface of the two regions. The corrugation pitch of the second region is shorter than that of the first region by 1.6 nm; the grating coupling coefficient is 40 cm?1; each region length is 300 μm. These parameters are modest to fabricate DFB-LDs.
关键词： Longitudinal mode,Coupled cavity,Direct modulation,Semiconductor laser,Diffraction grating
更新于2025-09-23 15:19:57
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An Easily Fabricated Linear Piezoelectric Actuator Using Sandwich Longitudinal Vibrators With Four Driving Feet
摘要： A piezoelectric actuator using three sandwich longitudinal vibrators is proposed and tested. The two horizontal vibrators are parallel to each other and orthogonal to the vertical vibrator. The ends of the two horizontal vibrators serve as the four driving feet. The actuator has a simple fabricating process, which will shorten the period of fabrication. Two modes of the actuator are used to get the elliptical trajectories on the driving feet. The frequencies of the two modes are tuned to be about 21.60 kHz with modal analysis by the finite element method (FEM). The operating principle is also examined with transient analysis by FEM. A prototype is fabricated and its vibration characteristics are verified by using a scanning laser Doppler vibrometer. The prototype shows the best mechanical performance with the optimum working frequency and phase difference of 18.50 kHz and 60°, respectively. The typical output of the prototype is a no-load speed of 439.41 mm/s, a maximum thrust of 40 N, and a maximum power of 5.01 W at the voltage of 200 VP?P. The mechanical characteristics of the prototype show that the exciting voltages can be used for the speed control due to the approximately linear relationship between them.
关键词： resonant state,vibration test.,Linear piezoelectric actuator,sandwich longitudinal vibrators
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) - Theoretical Analysis and Design of Longitudinal Leaky SAW Device Consisting of ScA1N Film / Piezoelectric Single Crystal Substrate
摘要： Theoretical Analysis and Design of Longitudinally Pumped Erbium-Doped Fiber Amplifiers for High-Power Operation
关键词： Fiber optics,Optical amplification,Erbium-doped fiber amplifier,Longitudinal pumping,High-power operation
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Combinatorial study of MZO emitters for CdTe-based solar cells
摘要： Loneliness is a common condition in older adults and is associated with increased morbidity and mortality, decreased sleep quality, and increased risk of cognitive decline. Assessing loneliness in older adults is challenging due to the negative desirability biases associated with being lonely. Thus, it is necessary to develop more objective techniques to assess loneliness in older adults. In this paper, we describe a system to measure loneliness by assessing in-home behavior using wireless motion and contact sensors, phone monitors, and computer software as well as algorithms developed to assess key behaviors of interest. We then present results showing the accuracy of the system in detecting loneliness in a longitudinal study of 16 older adults who agreed to have the sensor platform installed in their own homes for up to 8 months. We show that loneliness is significantly associated with both time out-of-home (β = ?0.88 and p < 0.01) and number of computer sessions (β = 0.78 and p < 0.05). R2 for the model was 0.35. We also show the model’s ability to predict out-of-sample loneliness, demonstrating that the correlation between true loneliness and predicted out-of-sample loneliness is 0.48. When compared with the University of California at Los Angeles loneliness score, the normalized mean absolute error of the predicted loneliness scores was 0.81 and the normalized root mean squared error was 0.91. These results represent first steps toward an unobtrusive, objective method for the prediction of loneliness among older adults, and mark the first time multiple objective behavioral measures that have been related to this key health outcome.
关键词： longitudinal models,loneliness,In-home monitoring,ambient assessment,older adults
更新于2025-09-19 17:13:59
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[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Optical Properties of A Silicon-Rich Nitride Ridge Waveguide at $2\ \boldsymbol{\mu}\mathbf{m}$ Wavelengths
摘要： Loneliness is a common condition in older adults and is associated with increased morbidity and mortality, decreased sleep quality, and increased risk of cognitive decline. Assessing loneliness in older adults is challenging due to the negative desirability biases associated with being lonely. Thus, it is necessary to develop more objective techniques to assess loneliness in older adults. In this paper, we describe a system to measure loneliness by assessing in-home behavior using wireless motion and contact sensors, phone monitors, and computer software as well as algorithms developed to assess key behaviors of interest. We then present results showing the accuracy of the system in detecting loneliness in a longitudinal study of 16 older adults who agreed to have the sensor platform installed in their own homes for up to 8 months. We show that loneliness is significantly associated with both time out-of-home (β = ?0.88 and p < 0.01) and number of computer sessions (β = 0.78 and p < 0.05). R2 for the model was 0.35. We also show the model’s ability to predict out-of-sample loneliness, demonstrating that the correlation between true loneliness and predicted out-of-sample loneliness is 0.48. When compared with the University of California at Los Angeles loneliness score, the normalized mean absolute error of the predicted loneliness scores was 0.81 and the normalized root mean squared error was 0.91. These results represent first steps toward an unobtrusive, objective method for the prediction of loneliness among older adults, and mark the first time multiple objective behavioral measures that have been related to this key health outcome.
关键词： longitudinal models,ambient assessment,loneliness,In-home monitoring,older adults
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - A widely tunable single longitudinal mode erbium-doped fiber laser based on a microfiber knot resonator
摘要： A widely tunable single longitudinal mode erbium-doped fiber laser based on a microfiber knot resonator is proposed. The laser is tuned from 1545 ~ 1565 nm with a high side-mode suppression ratio of 55 dB.
关键词： Fiber laser,Microfiber knot resonator,Single longitudinal mode
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Generation of MV/cm longitudinal terahertz electric fields from relativistic laser-solid interactions
摘要： We report on the generation and detection of longitudinal terahertz (THz) transient, with field strength of 1.5 MV/cm [1], at the focus of a radially polarized high-power terahertz beam generated at the rear surface of a thin metal foil irradiated by multi-terawatt laser pulse [2]. An f/1.5 off-axis parabolic mirror was used to focus the collimated THz beam. In addition to the longitudinal field, a transverse field, albeit off-axis, with amplitude in excess of 3 MV/cm was also measured.
关键词： multi-terawatt laser pulse,field strength,high-power terahertz beam,off-axis parabolic mirror,longitudinal terahertz
更新于2025-09-16 10:30:52
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[Laser Institute of America ICALEO? 2017: 36th International Congress on Applications of Lasers & Electro-Optics - Atlanta, Georgia, USA (October 22–26, 2017)] International Congress on Applications of Lasers & Electro-Optics - Adaptive optics for intra-volume engraving of glass with ultra-short laser pulses
摘要： Within the frame of high precision ultrafast laser processing of transparent materials, we report here on the use of adaptive optics as a tool for intra-volume laser engraving of glass. With the active monitoring of the laser beam wavefront, the repartition of the above-threshold energy in the focal volume is actively detected. Therefore, the elongation of the laser-induced modification due to longitudinal spherical aberration can be minimized or emphasized on demand. Indeed, the industrial adaptive optics set up, made of a wavefront sensor and a deformable mirror, permits the management of each wavefront aberration as RMS values of chosen Zernike polynomials coefficients. This technique allows the control of the processing of transparent dielectrics, whatever the index of refraction and the depth are. This study addresses the precise correlation between wavefront distortions and intra-volume modifications in borosilicate glass obtained with a 300 fs Yb-doped fiber laser running at 1030 nm. The effects of the 3rd and 5th orders of longitudinal spherical aberrations on the laser-induced marking of the bulk are investigated with the purpose of precisely controlling the length of the interaction volume in the illuminated dielectric material. We show here a minimization of the total length of the marking by 65% at 600 μm in depth, from the natural wavefront to the optimized one, close to the diffraction limit.
关键词： wavefront distortions,ultra-short laser pulses,intra-volume engraving,adaptive optics,glass,longitudinal spherical aberrations
更新于2025-09-16 10:30:52
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Method of Reducing Residual Stress Generated by Laser Cutting by Light Indentation of Sheet Metal Edge
摘要： The aim of the present research is to propose a new method for the reduction of the residual stress which was generated by laser cutting. Laser cutting has been expected to be used as an effective and potent method for cutting out blanks from rolled sheet metals because of its high flexibility of the cutting line and high productivity. However, residual stresses, which are inevitably generated by laser cutting, have been the greatest obstacle to the prevalence of laser cutting. One of the problems is the warping that occurs in the sheet metal subjected to bending processes following laser cutting. The authors present a new method for reducing residual stress generated by laser cutting. The method involves applying is to give light indentation on the sheet metal edge. The FEM analyses were carried out to study the feasibility of this method, to determine the method of applying indentation, and to optimize the conditions. Experiments were conducted for verification. As a result, the warp generated by the residual stress was significantly reduced to one-tenth of that without the new treatment, and the magnitude was satisfactorily small for industrial usage.
关键词： laser cutting,longitudinal camber,V bending,blank sheet metal,residual stress
更新于2025-09-16 10:30:52