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A STUDY ON COGNITIVE RESPONSE TENDENCY AND DAMAGE THRESHOLD OF ABSORBING MEDIUM BY LASER-INDUCED INDIRECT STIMULATION
摘要： Laser-based research can be used in biology, medicine, engineering and many other industries. The use of pulsed laser can induce thermoelastic effect in a short time and give mechanical stimulation to the human body. When the elastic medium is attached to the human body and the laser is irradiated, the mechanical stimulus induced in the elastic medium can be transferred to the human body, which may cause tactile sensation. In this study, we investigated the effects of laser-induced indirect stimulation on cognitive response and damage to absorbing medium. Through the human body experiment, we studied the laser parameter condition that most subjects feel touch. In addition, thermal analysis simulations were performed to predict the condition of the laser pulse energy, the laser frequency and the temperature at the damage threshold of the absorption medium. The results of this study are expected to be useful for conducting non-contact tactile sensation using laser, and this technique can be widely used in laser biomedical stimulation, haptic technology, and other biological and medical fields.
关键词： laser-induced thermoelastic effect,cognitive response,damage threshold,Laser indirect stimulation
更新于2025-09-16 10:30:52
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Damage Diagnosis of Reactive Powder Concrete under Fatigue Loading Using 3D Laser Scanning Technology
摘要： Damage mechanisms of Reactive Powder Concrete (RPC) under fatigue loading are investigated using the 3D laser scanning technology. An independently configured 3D laser scanning system is used to monitor the damaging procedure. Texture analysis technique is also applied to enhance the understanding of the damage mechanisms of RPC under fatigue loading. In order to obtain the characteristic parameters of point cloud data, a point clouds projection algorithm is proposed. Damage evolution is described by the change of point cloud data of the damage in the 2D plane and 3D space during fatigue loading. The Gray Level Co-occurrence Matrix (GLCM) method is used to extract the characteristic parameters to evaluate the statue of the structural. Angular Second Moment and Cluster Shadow of typical sensitive characteristic indexes is screened by using the Digital Feature Screening. The reliability of the damage index was verified by image texture analysis and data expansion. Indexes extracted in this paper can be used as a new structural health monitoring indicator to assess health condition.
关键词： damage monitoring,texture analysis,feature extraction,gray level co-occurrence matrix,image processing,3D laser scanning
更新于2025-09-16 10:30:52
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Study on laser-stricken damage to alumina ceramic layer of different surface roughness
摘要： This study examines the laser-stricken damage to different alumina ceramic surfaces of different roughness through multi-physical field coupling simulations and laser-striking experiments. The surfaces of different morphologies can be described by waves of different frequencies and amplitudes, and the waves which are discretized can be described by rectangular microstructures of different heights. In this paper, we found that the reaction of roughness surfaces to gauss lasers stricken on them could be simulated by the reaction of rectangular microstructures of different heights to laser strike. The simulation was carried out through the multi-physical field coupling method. The distribution of temperature and stress on rectangular microstructure were examined after being treated by high energy laser. It was found that overhigh temperature and stress were the main causes of laser-stricken damage, but there existed a critical rectangular column height value. The microstructure became increasingly prone to damage and fall-off with the increase of the rectangular column’s height, but it became decreasingly prone to damage after the rectangular column reached the critical value. In the experiments, seven roughness zones of alumina ceramic layer were chosen as sample surfaces for laser-striking experiment. The results showed that there was a critical roughness value at a fixed laser energy density. As a result, the amount of particles falling off the surfaces caused by laser strike was rising when the roughness was increasing. However, the amount of particles falling off the surfaces was decreasing after roughness reached the critical value. The critical rectangular column height value in the simulation corresponded to the critical roughness value in the experiment. Therefore, an appropriate selection of roughness is an important factor for obtaining high laser-stricken damage threshold.
关键词： simulation and experiment,surface roughness,rectangular microstructure,laser-stricken damage,alumina ceramic layer
更新于2025-09-16 10:30:52
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Subsurface damage and phase transformation in laser-assisted nanometric cutting of single crystal silicon
摘要： Single crystal Si subsurface damage and phase transformation caused by laser-assisted nanometric cutting were investigated in this paper through the ultraprecision cutting experiments and molecular dynamics simulation. Post-cutting examination of a crystal’s subsurface revealed a distorted Si-I layer and an amorphous Si with embedded nanocrystalline Si-III and Si-XII. As a result of insufficient contact pressure during laser-assisted cutting, the amorphous Si was directly generated from the Si-I through the collapse of the crystal lattice rather than from the intermediate high-pressure phase Si-II. The newly-formed amorphous Si crystallized partially during the laser-assisted cutting and transformed into metastable Si-III and Si-XII phases caused by the laser annealing effect. In comparison to machining without laser assistance, it was found that dislocation activity was increased by a factor of ~8×1014 when laser assistance was applied. This gave rise to enhancement of plastic deformability of the material, with the critical ductile-brittle transition depth of cut increasing from 150 nm to 395 nm and the thickness and extent of stress in the distorted Si-I subsurface layer being reduced.
关键词： single crystal silicon,laser assisted,phase transformation,nanometric cutting,subsurface damage
更新于2025-09-16 10:30:52
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Influences of nanosecond pulse pre-irradiation on femtosecond laser damage resistance of gold pulse compression grating
摘要： The gold pulse compression gratings (PCG) used in the Bidirectional Grating Compressor (BGC) suffers a nano- and femtosecond dual pulses irradiation. In the case that the ns pre-pulse comes 10 nanoseconds early before the fs pulse, experiments were conducted to investigate damage behaviors under the dual pulse irradiation. 1-on-1 laser induced damage threshold (LIDT) of the ns–fs dual pulses and fs single pulse were tested and compared. Scanning Electron Microscope (SEM) was employed to capture damage onset and exam the damage macro- and micro-morphologies. The mono-shot method, comparison between the damage zone and spatial distribution of laser pulses, was employed to analyze the difference of the damage onset fluences for the two cases thoroughly. It was found that there is no degradation of laser damage resistance due to the ns pre-pulse. Instead, a slightly increase (～10%) of fs LIDT caused by the ns pre-pulse was found.
关键词： Femtosecond laser damage,Nano- and femtosecond dual beam processing,Nanosecond pre-pulse,Gold-coated pulse compression gratings,Bidirectional grating compressor
更新于2025-09-16 10:30:52
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Studying Stability of CFRP Composites to Low-Energy Impact Damage by Laser Vibrometry
摘要： Nondestructive quality control of small-thickness composites is an important scientific and technical problem due to significant damage inflicted on materials even with minor impact loads. The stability of a 1-mm–thick CFRP composite to impact damage with an energy of up to 10 J has been investigated. Special attention has been paid to the analysis of the “visible” area of defects formed as a result of successive striking with increasing and decreasing energy in the range from 1 to 5 J. The area of defect indications was estimated by analyzing the images of vibrations at the surface of the composite produced by its acoustic stimulation and laser vibroscanning.
关键词： scanning laser vibrometry,nondestructive testing,impact damage,CFRP composite materials
更新于2025-09-12 10:27:22
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Numerical analysis of the thermally induced damage in remote laser cut carbon fibre reinforced polymers
摘要： Remote laser cutting in carbon fibre reinforced polymers is a promising machining technology which can reduce the main drawback in laser cutting, the heat affected zone. This contribution presents a two-step modelling approach for the simulation of remote laser cut carbon fibre reinforced polymers, consisting of a damage model for the initially intact material and a model for the thermally damaged material. The static damage behaviour was modelled with the Pinho material model [1], which stands out due to its physically based failure criteria. Initial thermal damages caused by the heat input were modelled with the damage parameters of the Pinho model. The dimensions of the heat affected zone are taken from polished microsections of the material around the cutting edge. As a numerical example, comparative tensile tests of milled and laser cut open hole specimens were simulated. The advantage of these specimens is the notch effect around the holes in the heat affected zone, which amplifies the differences between the two cutting technologies.
关键词： remote laser cutting,heat affected zone,damage model,Pinho material model,carbon fibre reinforced polymers
更新于2025-09-12 10:27:22
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Near-Field-Induced Femtosecond Breakdown of Plasmonic Nanoparticles
摘要： We studied the evolution of femtosecond breakdown in lithographically produced plasmonic nanoparticles with increasing laser intensity. Localized plasmons were generated with 40-fs laser pulses with up to 1.4 × 1012 W/cm2 peak intensity. The damage morphology shows substantial variation with intensity, starting with the detachment of hot spots and stochastic nanoparticle removal. For higher intensities, we observe precise nanolithographic mapping of near-field distributions via ablation. The common feature of these phenomena is the central role played by the single plasmonic hot spot of the triangular nanoparticles used. We also derive a damage threshold value from stochastic damage trends on the arrays fostering the optimization of novel nanoarchitectures for nonlinear plasmonics.
关键词： Laser-induced damage threshold,Plasmonic nanoparticles,Plasmonics,Field enhancement mapping
更新于2025-09-12 10:27:22
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Irradiation and dosimetry arrangement for a radiobiological experiment employing laser-accelerated protons
摘要： The Bragg Peak is a unique characteristic of ion beams which makes their use beneficial in cancer treatment as it allows the majority of dose deposition to be localised in a precise volume. The use of a laser system for particle acceleration is currently investigated as a potential alternative to the conventional RF accelerators currently used for hadrontherapy. The biological response of cells irradiated by high dose-rate laser-driven ions is currently being explored in this context. The experiment reported here was carried out as part of the A-SAIL project, a UK-wide collaboration aiming to develop innovative techniques for accelerating ions for future clinical applications. In this contest, a radiobiological experiment was carried out on the pico2000 laser beamline at LULI-école Polytechnique using an energetically spread, laser-accelerated proton beam. This paper will discuss the arrangement used in the experiment, and the techniques employed for an accurate estimation of the dose deposited, supported by Monte Carlo simulations of the particle propagation through the irradiation system.
关键词： Ion sources,Lasers,Radiation damage evaluation methods
更新于2025-09-12 10:27:22
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Response of Waveguide-Integrated Germanium-on-Silicon p-i-n Photodiodes to Neutron Displacement Damage
摘要： The effects of 14-MeV neutron displacement damage (DD) on waveguide-integrated germanium-on-silicon p-i-n photodiodes (PDs) for silicon photonics have been investigated up to fluences of 7.5×1012 n/cm2 (14 MeV), or 1.4×1013 n1-MeVeq /cm2(Si). The study includes measurements of dark current-voltage characteristics across temperature from 150-375 K, measurements of PD junction capacitance, spectral response measurements from 1260 nm to 1360 nm, and frequency response measurements. The devices are found to be susceptible to DD-induced carrier removal effects; however, they also continue to operate without meaningful impact to performance for the DD dose levels examined. Since the PD test chips include silicon photonic integrated grating couplers and waveguides which carry the optical signal to the PD, some assessment of the impact of DD on these passive devices can also be inferred. This work does not examine the short-term annealing or transient behavior of the DD, and instead has only considered the lasting damage that remains after any initial period of room temperature annealing.
关键词： displacement damage,photonics,Radiation effects,neutron radiation,photodiodes,optoelectronic devices
更新于2025-09-12 10:27:22