Laser Profile Research Articles

Reconfigurable topological phases in photoexcited graphene nanoribbon arrays

We introduced here a reconfigurable topological phase using optically pumped graphene nanoribbon arrays with homogeneous spacing at terahertz frequencies. By adjusting the profile of imaginary potential, various topologically non-trivial dimer chains composed of graphene nanoribbons can be selectively produced. These dimer chains support different kinds of midgap states. Moreover, we numerically demonstrated that these midgap states are robust against some perturbations, such as non-Hermitian and lattice disorders, and can be further adjusted by varying the pumping strength on the specific graphene nanoribbon. Consequently, the reconfigurable topological phase can be obtained by only tuning the profile of imaginary potential without altering the geometry of the system. These tunable topological phases may provide a convenient method to tune the spatial profile of graphene-based topological lasers and have potential applications in topologically protected waveguiding in terahertz frequency range.

A novel one-body dual laser profile based vibration compensation in 3D scanning

Recently, the 3D laser profile scanner has often been used for the precise measurement of 3D surface information (object surface) such as height, area, and slope. However, a difficulty encountered with the conventional laser scanning method is that it cannot compensate for the errors resulting from vibration, so the scanned object should be measured in a fixed (immobile) state. In this paper, we propose a novel dual laser profile method and its error compensation algorithm to compensate for vertical vibration, even with a moving object. In order to remove errors caused by vibration, the proposed system projects two laser profiles onto the surface, such that the projected position overlaps the one with the previous position. With the overlapped position, the height difference between the measured objects is used to calculate the vibration errors. To generate two laser profiles simultaneously, we present a novel approach for generating two laser profiles from one laser-emitting source (a one-body dual line laser using a triangular structured blazed grating reflector). By exploiting the one-body dual line laser and error compensation algorithm, the proposed 3D laser profile scanner system achieves an error reduction of about 96.3% in the root mean square error (RMSE), compared to the conventional approach.

Automatic Groove Measurement and Evaluation with High Resolution Laser Profiling Data

Grooving is widely used to improve airport runway pavement skid resistance during wet weather. However, runway grooves deteriorate over time due to the combined effects of traffic loading, climate, and weather, which brings about a potential safety risk at the time of the aircraft takeoff and landing. Accordingly, periodic measurement and evaluation of groove performance are critical for runways to maintain adequate skid resistance. Nevertheless, such evaluation is difficult to implement due to the lack of sufficient technologies to identify shallow or worn grooves and slab joints. This paper proposes a new strategy to automatically identify airport runway grooves and slab joints using high resolution laser profiling data. First, K-means clustering based filter and moving window traversal algorithm are developed to locate the deepest point of the potential dips (including noises, true grooves, and slab joints). Subsequently the improved moving average filter and traversal algorithms are used to determine the left and right endpoint positions of each identified dip. Finally, the modified heuristic method is used to separate out slab joints from the identified dips, and then the polynomial support vector machine is introduced to distinguish out noises from the candidate grooves (including noises and true grooves), so that PCC slab-based runway safety evaluation can be performed. The performance of the proposed strategy is compared with that of the other two methods, and findings indicate that the new method is more powerful in runway groove and joint identification, with the F-measure score of 0.98. This study would be beneficial in airport runway groove safety evaluation and the subsequent maintenance and rehabilitation of airport runway.

Accurate differentiation of novel Staphylococcus argenteus from Staphylococcus aureus using MALDI-TOF MS.

We evaluated a Staphylococcus argenteus-specific diagnostic profile of matrix-assisted laser desorption/ionization time-of-flight mass spectrometer for accurate identification of this novel bacterium. Staphylococcus argenteus was identified based on negative crtM gene and presence of specific sequence types. A classification model was generated by cluster analysis of matrix-assisted laser desorption/ionization time-of-flight mass spectrometer results and ClinProTools software for 25 S. argenteus and 25 methicillin-susceptible S. aureus (MSSA). The performance of the classification model was validated against 72 S. argenteus and 72 MSSA isolates. With cluster analysis and classification model, differentiation of 72 S. argenteus from 72 MSSA had 100.0% accuracy by chemical extraction method and 87.5% sensitivity and 100.0% specificity by direct smear method. The classification model could accurately differentiate S. argenteus from MSSA.

Formulation of oil-in-water emulsions for pesticide applications: impact of surfactant type and concentration on physical stability.

Oil-in-water (O/W) emulsions can be utilized as effective pesticide delivery systems in the agricultural industry. In this study, the effects of hydrophile-lipophile balance (HLB), concentration, and location of surfactants on the formation and physical stability of O/W emulsions suitable for pesticide applications was investigated using dynamic light scattering and vertical laser profiling. A non-polar pesticide (lambda-cyhalothrin) was used as a model. The pesticide emulsion with the highest stability was obtained using a commercial non-ionic surfactant (polyoxyethylene castor oil ether, EL-20) with a required HLB value of 10.5. Emulsion stability increased as the surfactant concentration was increased from 2 to 6%, which was attributed to the formation of smaller oil droplets during emulsification. Emulsions prepared with the surfactant initially in the oil phase were more stable than those prepared with it initially in the aqueous phase. The optimum formulation of the pesticide emulsion was determined as follows: 5% lambda-cyhalothrin (active ingredient) and 6% EL-20 (surfactant) dissolved in 5% S-200 (aromatic hydrocarbon, as oil phase), then deionized water up to 100%, which met the quality indicators set by the FAO standards. The present study is expected to provide useful information to improve the stability of pesticide emulsions for commercial applications.

Can the narrow red bands of dragonflies be used to perceive wing interference patterns?

Despite numerous studies of selection on position and number of spectral vision bands, explanations to the function of narrow spectral bands are lacking. We investigate dragonflies (Odonata), which have the narrowest spectral bands reported, in order to investigate what features these narrow spectral bands may be used to perceive. We address whether it is likely that narrow red bands can be used to identify conspecifics by the optical signature from wing interference patterns (WIPs). We investigate the optical signatures of Odonata wings using hyperspectral imaging, laser profiling, ellipsometry, polarimetric modulation spectroscopy, and laser radar experiments. Based on results, we estimate the prospects for Odonata perception of WIPs to identify conspecifics in the spectral, spatial, intensity, polarization, angular, and temporal domains. We find six lines of evidence consistent with an ability to perceive WIPs. First, the wing membrane thickness of the studied Odonata is 2.3 μm, coinciding with the maximal thickness perceivable by the reported bandwidth. Second, flat wings imply that WIPs persist from whole wings, which can be seen at a distance. Third, WIPs constitute a major brightness in the visual environment only second after the solar disk. Fourth, WIPs exhibit high degree of polarization and polarization vision coincides with frontal narrow red bands in Odonata. Fifth, the angular light incidence on the Odonata composite eye provides all prerequisites for direct assessment of the refractive index which is associated with age. Sixth, WIPs from conspecifics in flight make a significant contribution even to the fundamental wingbeat frequency within the flicker fusion bandwidth of Odonata vision. We conclude that it is likely that WIPs can be perceived by the narrow red bands found in some Odonata species and propose future behavioral and electrophysiological tests of this hypothesis.

Effect of aggregate graining compositions on skid resistance of Exposed Aggregate Concrete pavement

The paper presents the evaluation of skid resistance of EAC (Exposed Aggregate Concrete) pavements which differ in aggregate graining compositions. The tests were carried out on concrete mixes with a maximum aggregate size of 8 mm. Three types of coarse aggregates were selected depending on their resistance to polishing which was determined on the basis of the PSV (Polished Stone Value). Basalt (PSV 48), gabbro (PSV 50) and trachybasalt (PSV 52) aggregates were chosen. For each type of aggregate three graining compositions were designed, which differed in the content of coarse aggregate > 4mm. Their content for each series was as follows: A - 38%, B - 50% and C - 68%. Evaluation of the skid resistance has been performed using the FAP (Friction After Polishing) test equipment also known as the Wehner/Schulze machine. Laboratory method enables to compare the skid resistance of different types of wearing course under specified conditions simulating polishing processes. In addition, macrotexture measurements were made on the surface of each specimen using the Elatexure laser profile. Analysis of variance showed that at significance level α = 0.05, aggregate graining compositions as well as the PSV have a significant influence on the obtained values of the friction coefficient μm of the tested EAC pavements. The highest values of the μm have been obtained for EAC with the lowest amount of coarse aggregates (compositions A). In these cases the resistance to polishing of the aggregate does not significantly affect the friction coefficients. This is related to the large areas of cement mortar between the exposed coarse grains. Based on the analysis of microscope images, it was observed that the coarse aggregates were not sufficiently exposed. It has been proved that PSV significantly affected the coefficient of friction in the case of compositions B and C. This is caused by large areas of exposed coarse aggregate. The best parameters were achieved for the EAC pavements with graining composition B and C and trachybasalt aggregate.

REFINED SIMULATION OF SATELLITE LASER ALTIMETER FULL ECHO WAVEFORM

Abstract. The return waveform of satellite laser altimeter plays vital role in the satellite parameters designation, data processing and application. In this paper, a method of refined full waveform simulation is proposed based on the reflectivity of the ground target, the true emission waveform and the Laser Profile Array (LPA). The ICESat/GLAS data is used as the validation data. Finally, we evaluated the simulation accuracy with the correlation coefficient. It was found that the accuracy of echo simulation could be significantly improved by considering the reflectivity of the ground target and the emission waveform. However, the laser intensity distribution recorded by the LPA has little effect on the echo simulation accuracy when compared with the distribution of the simulated laser energy. At last, we proposed a refinement idea by analyzing the experimental results, in the hope of providing references for the waveform data simulation and processing of GF-7 satellite in the future.

Q Value Based Ablation Profile versus Topography - Guided LASIK : A Contralateral Comparative Study

Background: laser in situkeratomileusis (LASIK) has become the most widely used form of refractive surgery. The objective of this surgical technique was to modify the anterior corneal shape by ablating tissue from the stroma by means of the excimer laser after creating a hinged corneal flap. By this way, we were able to change the refractive status of the patient and provided better unaided vision. Continuous improvements in the original technique made the surgical procedure safer, more accurate and repeatable. These progressions are due to the development of novel technologies that are responsible for new surgical instrumentation, which makes the surgical procedure easier for the surgeon and better excimer laser ablation algorithms, which increase the optical quality of the ablation and thus the safety of the vision correction procedure. Aim of work: the aim of this study was to compare between Q value based ablation and topography-guided LASIK as regards safety, visual acuity, contrast sensitivity and high order aberration HOAs (spherical, coma and trefoil). Patients and methods: this study was conducted on 60 eyes of 30 patients, thirty eyes of them underwent topography guided LASIK and the other 30 underwent Q value based ablation. Preoperative CDVA (corrected distant visual acuity) was done. Postoperative UDVA and CDVA were measured. Postoperative high order aberrations were measured 3 months postoperatively. Results: our results showed that there was no statistically significant difference between both groups as regards UDVA, spherical equivalent, high order aberrations and Strehl ratio point spread function. Conclusion: topographic guided ablation and Q value based groups provided essentially equivalent outcomes after myopic LASIK, with statistically insignificant difference between both profiles, although both laser profiles have been found to be effective, safe and predictable.

Relaxation Dynamics of a Granular Pile on a Vertically Vibrating Plate.

Nonlinear relaxation dynamics of a vertically vibrated granular pile is experimentally studied. In the experiment, the flux and slope on the relaxing pile are measured by using a high-speed laser profiler. The relation of these quantities can be modeled by the nonlinear transport law assuming the uniform vibrofluidization of an entire pile. The fitting parameter in this model is only the relaxation efficiency, which characterizes the energy conversion rate from vertical vibration into horizontal transport. We demonstrate that this value is a constant independent of experimental conditions. The actual relaxation is successfully reproduced by the continuity equation with the proposed model. Finally, its specific applicability toward an astrophysical phenomenon is shown.

Detailed Determination of Mechanical Fracture Parameters of Concrete after Fire Experiments

The aim of this paper is to describe the procedure of determining the mechanical fracture parameters of selected concrete specimens taken from panels after the fire experiments. The records (in form load vs displacement diagrams) of three-point bending fracture tests of these specimens with initial stress concentrators was first advanced corrected and subsequently evaluated using the Effective Crack Model and the work-of-fracture method. The increasing temperatures during the fire experiments ranging between 550 to 1000 °C led to a decrease of modulus of elasticity and fracture toughness values and to the increase of fracture energy value. The 2D laser profile scanner was used to estimate the degree of complexity of fracture surfaces; its statistical dependence on the mechanical fracture parameters proved to be moderate – the absolute value of the correlation coefficient was about 0.5°[–].

Nanosecond Laser Treatment for Age-Related Macular Degeneration Does Not Induce Focal Vision Loss or New Vessel Growth in the Retina.

Subthreshold, nanosecond pulsed laser treatment shows promise as a treatment for age-related macular degeneration (AMD); however, the safety profile needs to be robustly examined. The aim of this study was to investigate the effects of laser treatment in humans and mice. Patients with AMD were treated with nanosecond pulsed laser at subthreshold (no visible retinal effect) energy doses (0.15-0.45 mJ) and retinal sensitivity was assessed with microperimetry. Adult C57BL6J mice were treated at subthreshold (0.065 mJ) and suprathreshold (photoreceptor loss, 0.5 mJ) energy settings. The retinal and vascular responses were analyzed by fundus imaging, histologic assessment, and quantitative PCR. Microperimetry analysis showed laser treatment had no effect on retinal sensitivity under treated areas in patients 6 months to 7 years after treatment. In mice, subthreshold laser treatment induced RPE loss at 5 hours, and by 7 days the RPE had retiled. Fundus imaging showed reduced RPE pigmentation but no change in retinal thickness up to 3 months. Electron microscopy revealed changes in melanosomes in the RPE, but Bruch's membrane was intact across the laser regions. Histologic analysis showed normal vasculature and no neovascularization. Suprathreshold laser treatment did not induce changes in angiogenic genes associated with neovascularization. Instead pigment epithelium-derived factor, an antiangiogenic factor, was upregulated. In humans, low-energy, nanosecond pulsed laser treatment is not damaging to local retinal sensitivity. In mice, treatment does not damage Bruch's membrane or induce neovascularization, highlighting a reduced side effect profile of this nanosecond laser when used in a subthreshold manner.

Functional and structural parameters of a paved road section constructed with mixed recycled aggregates from non-selected construction and demolition waste with excavation soil

This paper evaluates the lab and in situ mechanical properties of non-selected mixed recycled aggregates from construction and demolition waste (CDW) used as base and subbase unbound materials. Excavation materials are mixed with CDW to produce recycled mixed aggregates with soil, as well as a finer material referred to as mixed recycled soil. The research was divided into two different stages: a laboratory study characterizing the properties of recycling aggregates and a road test track evaluating the long-term performance of these materials under real traffic and weather conditions. During construction, several density, plate load, and falling weight deflectometer tests were performed to determine the bearing capacity of all layers. A laser profiler was also used to obtained the international roughness index. After the road was opened to traffic, a follow up of deflections and surface roughness was performed during the following seven years.Two different moduli calculation methods were used: back calculation and forward calculation. Both methods shown acceptable values for these recycled materials. Low quality recycled mixed aggregates can be used as substitutes for natural aggregates as unbound layers. The mechanical performance and surface roughness values obtained from the experimental road shown an acceptable behaviour.

Calibration and using a laser profile scanner for 3D robotic welding

This paper describes first functions of a developed cognitive module for 3D robotic welding using TIG or laser technology. This area is constantly evolving with the needs to solve complex problems of welding automatisation and robotisation, and also thanks to the continuous advances in measurement technology and robotics. Besides, the use of welding robots for serial production with dedicated tightly defined trajectories, systems for automatic welding of a previously undefined path or paths, which the operator cannot manually define because of its complexity, are developed. This paper covers the general description of the cognitive module and its required functions. Then necessary knowledge about a pose representation and transformation is presented. After that, procedures for a calibration of a profile scanner and its using for 3D model construction based on a depth map are described in more detail. The cognitive module prototype is tested in the task of automatic cavity repair.

Calibration and using a laser profile scanner for 3D robotic welding

This paper describes first functions of a developed cognitive module for 3D robotic welding using TIG or laser technology. This area is constantly evolving with the needs to solve complex problems of welding automatisation and robotisation, and also thanks to the continuous advances in measurement technology and robotics. Besides, the use of welding robots for serial production with dedicated tightly defined trajectories, systems for automatic welding of a previously undefined path or paths, which the operator cannot manually define because of its complexity, are developed. This paper covers the general description of the cognitive module and its required functions. Then necessary knowledge about a pose representation and transformation is presented. After that, procedures for a calibration of a profile scanner and its using for 3D model construction based on a depth map are described in more detail. The cognitive module prototype is tested in the task of automatic cavity repair.

Evaluation of Remineralization Potential of Beverages modified with Casein Phosphopeptide-Amorphous Calcium Phosphate on Primary and Permanent Enamel: A Laser Profiler Study.

PurposeTo assess the erosive potential of carbonated beverages and the remineralization potential of beverages with added casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste on primary and permanent enamel.Materials and methodsA total of 32 primary and 32 permanent enamel specimens were immersed for 5, 10, and 30 minutes, respectively, in beverages, i.e., Coke, Sprite, Mirinda, and Mountain Dew, with and without added 0.2% CPP-ACP. Samples were profiled before immersion and after immersion under laser profiler.ResultsCoke was found to be highly erosive at it caused significant enamel erosion at both 10 and 30 minutes of immersion (p < 0.05) for both primary and permanent enamel. The 30-minute immersion caused significant amount of reminerali-zation over primary enamel in all groups, whereas permanent enamel remineralization was significant in Sprite and Mountain Dew at 30 minutes in all the groups (p < 0.05).ConclusionThis study demonstrated that enamel erosion occurred after immersion in carbonated beverages. Remineralization of enamel was observed after immersion in beverages modified with CPP-ACP paste. Primary enamel was susceptible to remineralization compared with permanent enamel. Within the limitations of this in vitro study, the application of CPP-ACP paste may enhance the remineralization after an erosive challenge and thus offer some protection for patients who are at risk for erosion.How to cite this article: Rai N, Sandhu M, Sachdev V, Sharma R. Evaluation of Remineralization Potential of Beverages modified with Casein Phosphopeptide-Amorphous Calcium Phosphate on Primary and Permanent Enamel: A Laser Profiler Study. Int J Clin Pediatr Dent 2018;11(1):7-12.

Tribological behaviors of UHMWPE composites with different counter surface morphologies

The influence of counter surface morphologies on hybrid glass fiber (GF) and carbon fiber (CF) filled ultrahigh molecular weight polyethylene (UHMWPE) were studied under various contact pressure and sliding speed against GCr15 steel in dry condition. The goals were to investigate the tribological behavior of GF/CF/UHMWPE composite as a kind of water lubricated journal bearing material. The friction and wear behavior of composites were examined using a pin-on-disc tribometer. The morphologies of the worn surface were examined by scanning electron microscopy (SEM) and laser 3D micro-imaging and profile measurement. Generally, the wear rate and friction coefficient of composites increase as the increment of counter surface roughness. The friction coefficient increases firstly and then decrease with an increase in sliding speed and contact pressure for counterface with Ra=0.2 and 3.5 μm, while the friction coefficient decreased for counterface with Ra=0.6 μm.

Experimental study on the crack detection with optimized spatial wavelet analysis and windowing

Abstract In this paper, a high sensitive crack detection is experimentally realized and presented on a beam under certain deflection by optimizing spatial wavelet analysis. Due to the crack existence in the beam structure, a perturbation/slop singularity is induced in the deflection profile. Spatial wavelet transformation works as a magnifier to amplify the small perturbation signal at the crack location to detect and localize the damage. The profile of a deflected aluminum cantilever beam is obtained for both intact and cracked beams by a high resolution laser profile sensor. Gabor wavelet transformation is applied on the subtraction of intact and cracked data sets. To improve detection sensitivity, scale factor in spatial wavelet transformation and the transformation repeat times are optimized. Furthermore, to detect the possible crack close to the measurement boundaries, wavelet transformation edge effect, which induces large values of wavelet coefficient around the measurement boundaries, is efficiently reduced by introducing different windowing functions. The result shows that a small crack with depth of less than 10% of the beam height can be localized with a clear perturbation. Moreover, the perturbation caused by a crack at 0.85 mm away from one end of the measurement range, which is covered by wavelet transform edge effect, emerges by applying proper window functions.

Impact of mismatched and misaligned laser light sheet profiles on PIV performance

The effect of mismatched or misaligned laser light sheet profiles on the quality of particle image velocimetry (PIV) results is considered in this study. Light sheet profiles with differing widths, shapes, or alignment can reduce the correlation between PIV images and increase experimental errors. Systematic PIV simulations isolate these behaviours to assess the sensitivity and implications of light sheet mismatch on measurements. The simulations in this work use flow fields from a turbulent boundary layer; however, the behaviours and impacts of laser profile mismatch are highly relevant to any fluid flow or PIV application. Experimental measurements from a turbulent boundary layer facility are incorporated, as well as additional simulations matched to experimental image characteristics, to validate the synthetic image analysis. Experimental laser profiles are captured using a modular laser profiling camera, designed to quantify the distribution of laser light sheet intensities and inform any corrective adjustments to an experimental configuration. Results suggest that an offset of just 1.35 standard deviations in the Gaussian light sheet intensity distributions can cause a 40% reduction in the average correlation coefficient and a 45% increase in spurious vectors. Errors in measured flow statistics are also amplified when two successive laser profiles are no longer well matched in alignment or intensity distribution. Consequently, an awareness of how laser light sheet overlap influences PIV results can guide faster setup of an experiment, as well as achieve superior experimental measurements.

Modeling of first-order photobleaching kinetics using Krylov subspace spectral methods

We solve the first order 2-D reaction–diffusion equations which describe binding-diffusion kinetics using the photobleaching scanning profile of a confocal laser scanning microscope, approximated by a Gaussian laser profile. We show how to solve the first-order photobleaching kinetics partial differential equations (PDEs) using a time-stepping method known as a Krylov subspace spectral (KSS) method. KSS methods are explicit methods for solving time-dependent variable-coefficient partial differential equations. They approximate Fourier coefficients of the solution using Gaussian quadrature rules in the spectral domain. In this paper, we show how a KSS method can be used to obtain not only an approximate numerical solution, but also an approximate analytical solution when using initial conditions that come from pre-bleach steady states and also general initial conditions, to facilitate asymptotic analysis. Analytical and numerical results are presented. It is observed that although KSS methods are explicit, it is possible to use a time step that is far greater than what the CFL condition would indicate.