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Laser ultrasonic SAFT can be applied for noncontact testing and imaging of defects in structures. However, due to the large demand for signal data by laser scanning, the time consumption of this method would be relatively long. To address this problem, this paper proposes a fast LU-SAFT method with sparse scanning data and F-K based interpolation. It aims to reduce the inspection time but without decreasing the imaging resolution. First, the method determines the minimum number of scanning sparse points using simulation. Then the F-K interpolation method is utilised to recover the full-field unscanned point signal from the sparse scan data. Finally, the reconstructed signal is used for SAFT image reconstruction of the defect. The experimental results show that, for the same scanning area, the proposed method in this paper reduces the number of scanning points by 87.5% and shortens the scanning time by 86.0% compared to conventional LU-SAFT point-by-point scanning. Additionally, the signal-to-noise ratio of the defective SAFT imaging decreases by only about 7.9%. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) presents promising prospects for the production of laser ceramics, particularly those with composite structures. However, achieving uniform density within these ceramics is a formidable challenge, primarily due to the intrinsic limitations of uneven forces within the mold. This paper introduces the Density Spatiotemporal Evolution (DSE) model, a novel predictive tool designed to map the density distribution in laser ceramics throughout the AM process. The DSE model elucidates that ceramic density increases in proximity to the indenter and mold wall and reveals an oscillatory pattern in particle density during pressing. These insights have been corroborated through experimental measurements and simulation analyses. Leveraging the DSE model and a Simulated Annealing (SA) algorithm, an innovative AM process is proposed. The pressure exerted to each layer of ceramics is gradient distributed, i.e. 18, 18.36, 19.31, 22.08, 33.02 MPa. Preliminary experimental results indicate a significant enhancement in density uniformity, with an improvement of up to 45% in the optimized ceramics. The advancement promises to yield more homogeneous ceramic materials, potentially accelerating the progress of high-energy laser technology. [ABSTRACT FROM AUTHOR]

The article invites papers on the development and potential of next generation free-electron lasers to be published in the journal.

The goal of this paper is to determine whether laser-induced surface melting can generate adhesive debonding. Commercial cyanoacrylate and acrylic adhesives are used to attach an aluminum (Al) cylinder to a transparent polymethyl(methacrylate) (PMMA) plate, and then a variable force is applied to create an axially loaded butt joint. High energy nanosecond laser pulses at 1064 and 532 nm are directed through the transparent PMMA to be absorbed at the Al surface, causing transient localized heating that leads to joint failure. The dependence of this debonding on both laser fluence (energy per area) and applied force are investigated. Single shot debonding occurs at fluences on the order of 0.47 J/cm2 for 1064 nm and 0.29 J/cm2 for 532 nm pulses with an applied pressure of 0.22 MPa. Characterization of the Al surface before and after laser impact confirms that the debonding arises from surface melting and causes only slight changes to the Al surface. A simple model of the debonding process is developed to explain the dependence of the debonding on the applied load. Single laser pulses can generate instantaneous, relatively clean separation of bonded joints, suggesting that laser debonding may be a promising strategy to initiate deadhesion. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) is increasingly prominent in essential fields such as aerospace. However, due to the characteristics of the manufacturing process and the high test cost, the performance of fabricated structures is inherently uncertain, leading to a challenging characterisation of their performance. This paper proposes a non-probabilistic convex modelling framework involving confirming uncertainties, processing data, and establishing a nonprobabilistic convex model, to quantitatively describe the uncertainties concerning the physical properties of structures fabricated by LPBF. Firstly, the non-probabilistic convex modelling framework is proposed and an efficient uncertainty quantification method is developed utilising the non-probabilistic convex model. Then, criteria are set up for evaluating the performance of the developed method, and computational efficiency and accuracy are illustrated via benchmark numerical examples. Last but not least, two types of representative structures, solid and lattice structures, are fabricated via the LPBF method. The physical properties are tested through tensile and compression experiments. By confirming the necessity of accounting for uncertainties with limited data, we employing the proposed framework to the real representative specimens fabricated via the LPBF method, demonstrating that the structures fabricated by LPBF have substantial uncertainty and the proposed framework is practical. [ABSTRACT FROM AUTHOR]

Carbon fibre reinforced polymer (CFRP) plays an increasingly important role in many fields, and the non-destructive testing (NDT) for its defects is drawing more and more attention. In this paper, a finite element model is established and the surface temperature difference between the defective and non-defective areas is selected as the characteristic quantity to systematically study the impact of three parameters, such as scanning direction, laser power and scanning speed, on the detection effect in the line laser scanning thermography NDT system. Qualitatively, the scanning direction is consistent with the carbon fibre orientation, the higher the laser power, and the slower the scanning speed is, the more favourable the defect detection. Further, the data obtained from the simulation are fitted, and the results show that the scanning speed and laser power have exponential and linear relationships with the maximum temperature difference, respectively. A related experimental system was established, the laser power was set to 7-, 10-, 13- and 15 W as well as the scanning speed to 10-,20-, 40- and 50 mm/s, to investigate the temperature variation of CFRP specimens containing artificial defects. The experimental results show that a greater laser power or lower scanning speed can obtain better defect detection compared with a smaller power or higher scanning speed. [ABSTRACT FROM AUTHOR]

Traditional Light Detection and Rangings (LiDARs) can quickly collect high-accuracy of three-dimensional (3D) point cloud data at a designated wavelength (i.e., cannot obtain hyperspectral data), while the passive hyperspectral imager can collect rich spectral data of ground objects, but are lack of 3D spatial data. This paper presents one innovative study on the design of airborne-oriented supercontinuum laser hyperspectral (SCLaHS) LiDAR with 50 bands covering 400 nm to 900 nm at a spectral resolution of 10 nm and ground sampling distance (GSD) of 0.5 m. The major innovations include (1) development of the high-power narrow-pulse supercontinuum laser source covering 400 nm to 900 nm with 50 bands using multi-core microstructure fibre, all-polarization maintaining fibre and ultra-long cavity structure, (2) a miniaturized aberration correction holographic concave grating spectroscopic and streak tube technique are developed for 50 bands laser echoes detection at high spectral-spatial-temporal resolution and dynamic airborne platform, and (3) the algorithm theoretic basis for SCLaHS LiDAR point cloud data 3D geodetic coordination calculation, including in-flight airborne calibration algorithm. The initial experimental results demonstrated that the designed SCLaHS LiDAR is doable, and a prototype of the (SCLaHS) LiDAR intends to be implemented. [ABSTRACT FROM AUTHOR]

This paper explores the potential for conservators to use their unique combination of materials and heritage experience to tackle the challenges of recovery in fire-affected areas, helping to minimise the waste and greenhouse gas emissions associated with traditional processes of post-disaster building remediation by facilitating cleaning and repair rather than replacement and disposal of fire-affected materials. The focus is not on saving 'special' items, but on remediating the broader fabric of homes and possessions that embody a sense of place and identity that sustains wellbeing and aids recovery after disaster. The samples used are painted plasterboard affected by smoke from the 2019 bushfires on the south-eastern coast of Australia. The method being trialled is the use of lasers to remove ash (soot) deposited by the smoke, to achieve a reduction in visual reminders of the fire and a surface that is ready for processes such as sanding, plastering or repainting to prepare a home for quick post-disaster re-occupation. Lasers have been extensively used for cleaning buildings. They use light energy to clean, so do not require abrasives or other chemicals, or touching of the surface. Nanosecond and femtosecond pulse lasers are trialled, and the effectiveness of the laser cleaning is analysed using visual assessment, optical microscopy, spectrophotometry and Fourier transform infrared (FTIR) spectroscopy. [ABSTRACT FROM AUTHOR]

The paper analyzes the spatial distribution of the average air density in a supersonic jet based on the results of laser transillumination. The algorithm to retrieve the average air density from transverse (to the jet axis) deviations of the transilluminating wavefront was tested in experiments on the Vertical jet setup of ITAM SB RAS. The results of retrieval are compared with the known literature data of contact measurements and with results of numerical simulation. The good sensitivity of local wavefront tilts to oscillations in the air density at frequencies of discrete acoustic tones has been demonstrated. This opens up the possibility of experimental study of the spatial structure of air density inhomogeneities in the jet channel. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically studied a 3D structure of GaAs/Al0.3Ga0.7As triple concentric quantum rings submitted to the combined action of a non-resonant intense laser and a static electric field. The 3D model was built using the cross-sectional profile of the structure that corresponds to a realistic experimental case of triple rings with different heights and widths. The electric field and the laser field have opposite influence on the energy levels, decreasing or increasing all studied levels, respectively. Linear or quadratic Stark effect can be seen in specific ranges of electric field values, depending on the anisotropy induced by the intense laser field, for given fields orientations. The observed anti-crossings are explained by wave-functions delocalisation from one ring to another or by symmetry exchange between the wave-functions of the inner ring. For the most deformed potential created by perpendicular orientation of electric field and intense laser polarisation, very large absorption peaks, blue-shifts, red-shifts or an oscillatory behaviour in peaks energy and amplitude are obtained in a controllable way by proper manipulation of the fields. This can be helpful for the tunability and optical features improvement of THz detectors or solar cells. [ABSTRACT FROM AUTHOR]

With the increasing demand of quality assurance and reliability of additive manufacturing (AM), the demand of development of advanced in-situ monitoring systems is increased to monitor the process behavior. Optical-based camera monitoring systems are proved as the effective ways to observe part surface layer wise. For certain camera-based monitoring system, the coverage of the build platform and the resolution of the images are always a trade-off. In the low-resolution images, detailed features (e.g. scan vector) are often lost. Super resolution (SR) algorithms are often discussed in the literature, but there are no specific applications in AM area. In this paper, the authors present a U-Net-based super-resolution (SR) algorithm to enhance details of monitoring image of the optical camera for the LPBF process. A test setup was built in the laboratory to generate high-resolution images for training. To have precise original images for the validation, low-resolution images were downscaled and blurred from high-resolution images. SR results were evaluated by peak signal to noise ratio (PSNR) and plausibility of details. The SR algorithm shows the ability to reconstruct detailed features from low-resolution images for LPBF process. [ABSTRACT FROM AUTHOR]

In most Mobile Laser Scanning (MLS) applications, filtering is a necessary step. In this paper, a segmentation-based filtering method is proposed for MLS point cloud, where a segment rather than an individual point is the basic processing unit. In particular, the MLS point clouds in some blocks are clustered into segments by a surface growing algorithm, and then the object segments are detected and removed. A segment-based filtering method is employed to detect the ground segments. The experiment in this paper uses two MLS point cloud datasets to evaluate the proposed method. Experiments indicate that, compared with the classic progressive TIN (Triangulated Irregular Network) densification algorithm, the proposed method is capable of reducing the omission error, the commission error and total error by 3.62%, 7.87% and 5.54% on average, respectively. [ABSTRACT FROM AUTHOR]

Micro-cutting edges are often used for the die cutting of functional films and paper containers. A hardening process is needed here because the ridgelines of micro-cutting edges require not only wear resistance but also sharpness and shape accuracy. A method of laser hardening after machining for the micro-cutting edge fabrication has previously been developed. This process uses laser hardening after shape fabrication of a micro-cutting edge in a pre-hardened steel workpiece. However, since the edge's heat capacity is limited, edge melting can occur because of overheating during laser irradiation, and a method to overcome this issue is thus needed. Thus, we propose a novel method of micro-cutting edge shape formation after laser hardening with demonstrable effects for micro-cutting edges with a straight ridgeline. Various trials were conducted to evaluate the applicability of this method for curve-shaped micro-cutting edges. As a result, useful knowledge for the creation of high-precision micro-cutting edges using the proposed method was obtained. [ABSTRACT FROM AUTHOR]

In this paper, a study of surface plasma wave excitation from a magnetized metallic surface using two co-propagating lasers is conducted. Two lasers propagating in the same direction with frequency difference of plasmon frequency of the metal excite plasma oscillations on the metallic surface, which generate surface plasma waves. The transverse components of the field associated with these surface plasma wave lead to excite transverse current at terahertz frequency. We report a systematic theoretical model for this study and subsequent numerical results are presented for THz field estimation. [ABSTRACT FROM AUTHOR]

The surface microstructure is one of the most important factors affecting the mechanical performance of adhesive bonding joint of CFRP materials. The aim of this paper mainly focused on the influence of laser generated microgrooves geometric parameters (groove depth, distances, and patterns) on the shearing strength of CFRP/aluminium alloy adhesive joints. An IR laser with a wavelength of 1064 nm was applied to pretreat the CFRP surface. Scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM) were used to observe and measure the surface morphology, cross-sectional shape, groove parameters (depth, width) and surface roughness. The single-lap shear experiments were also conducted to exam the quality of the adhesive joint. Meanwhile, failure modes under different groove parameters were examined using a digital camera. The main parameters of the grooves and their interaction effects on the final joint strength were quantitatively analyzed by an interactive orthogonal experimental design. It was concluded that the interaction of groove pattern and groove distance was the most significant factor affecting shear strength, followed by groove pattern and groove distance. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) is an additive manufacturing technology for metals. Ti-6Al-4V (Ti64) is a frequently used material for LPBF, but as-built LPBF-Ti64 has poor ductility that limits its usage. Herein, we study how the Al content will affect the microstructure and mechanical properties of LPBF Ti-xAL-4 V alloys (x = 4, 6, 8, wt.%). The materials' strength increases with Al%. Both Ti-4Al-4V (Ti44) and Ti-8Al-4V (Ti84) alloys exhibit higher work hardening and uniform elongation values than Ti64. This outcome is attributed to activation of multiple slip modes in Ti44 and a more heterogeneous microstructure in Ti84. This paper reports that work hardening and uniform elongation values of LPBF Ti-xAl-4 V alloys do not monotonically change with the Al content. Instead, the conventional Ti-6Al-4V exhibits the least values. [ABSTRACT FROM AUTHOR]

Designed to increase safety of people and property during their different stages of life (storage, transportation, handling), low-vulnerability ammunitions (LOVA) can lead to ignition issues during their use. Ignition and combustion characteristics of two LOVA RDX-based gun propellants are experimentally investigated in this paper. The ignition is performed by a laser diode, and combustion is studied in a closed-volume reactor for different initial pressures (10–70 bar) and laser powers (1.39 to 10.13 W). The present study especially focuses on the influence of atmosphere nature: new results under synthetic air are compared to results previously obtained under argon and nitrogen. Air appears to have a different effect on combustion properties following the nature of the propellant. For P1, composed of RDX and HTPB, the highest overpressures and propagation rates are obtained under air. On the contrary, similar performances have been encountered under air and argon for the RDX/NC propellant P2. Ignition delays and probabilities, as for them, seem to be more sensitive to laser power than to atmosphere nature. [ABSTRACT FROM AUTHOR]

Freeform parameterizations to reproduce structure deformation are increasingly important topics in laser-scanner-based deformation analyses. High-accuracy assurance of free-form surface approximation is extremely critical for reliable deformation analysis. One main challenge in this field is the model selection. Improper model complexity could result in under-fitting the real object shape or overfitting data noises, and thus a failure of deformation analysis. A multi-sensor system could integrate advantages of different sensors and improve the quality of mission completed. This paper combines terrestrial laser scanning (TLS) and laser tracker (LT) technologies, to enhance high-accuracy surface modeling in deformation analysis. A surface-based B-spline approximation and a multi-sensor system are investigated, the latter of which focuses mainly on the combination of TLS and LT technologies. The innovation of this paper is that the surface-based B-spline approximation is validated and optimized with LT corner cube reflectors. Hypothesis testing is adopted to select the best parameter setting by judging most consistency of TLS and LT in various epochs. In the B-spline surface modeling, both instrumental and numerical uncertainties are considered. We use the instrumental uncertainty model based on intensity value, as well as numerical uncertainty based on adjustment theories. A sampling strategy is proposed to avoid data gaps and obtain even distributed data points. [ABSTRACT FROM AUTHOR]

Titanium alloys have high hardness and low plasticity, there will be large cutting force and serious tool wear during machining. Laser-assisted grinding can significantly improve its machinability, but the wear mechanism of abrasive tools and its influence on material removal during machining have not been well revealed. In this paper, the variation of cutting force under different laser power, laser scanning speed and feed speed were studied. In addition, the influences of different laser powers on material removal was also investigated. At the same time, the abrasive belt wear in laser-assisted grinding and conventional grinding was compared. The results indicated that increasing the laser power can reduce the cutting force. When the laser power increased from 7.2W to 9.6W, the cutting force showed the maximum change trend, which decreased by 46%. Enhanced material removal and increased plastic flow with increasing laser power. Increasing the laser scanning speed and workpiece feeding rate will also increase the cutting force. In addition, laser-assisted grinding can reduce belt wear compared with conventional grinding under the same grinding parameters. Therefore, laser-assisted grinding has an important potential role in the field of grinding. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to demonstrate the easy manufacturing and quick characterization of several microtextured functional surfaces on two transparent thermoplastics of general interest for several industrial sectors. Microtextured polymeric surfaces with special optical, tribological and easy-cleaning properties were manufactured via isothermal injection-molding using laser-microtextured steel mold inserts. For that purpose, conventional injection molding of two chosen amorphous transparent polymers (polycarbonate, PC, and polymethyl methacrylate, PMMA) utilizing laser-microtextured steel inserts was carried out, and a detailed morphological and functional characterization of the injected specimens was conducted later on. We also report on the suitable process conditions for the injection molding of these specimens using design of experiment (DOE) techniques. The analysis of the degree of replication (DR%) on the injected samples shows that mold temperature and injection speed are the most relevant parameters to obtain a successful replication and confirm the viability of conventional injection molding as a processing technique to obtain microtextured functional surfaces in amorphous transparent thermoplastics. The success of the procedure is further checked by the confirmation of the obtained surface functionalities by various standard and self-developed methods. [ABSTRACT FROM AUTHOR]

In many applications of joining and reinforcing timber elements with self-tapping fully threaded screws, the exact positioning of the screws becomes difficult as the screws tend to "stray" from their designated axis during insertion in wood and wooden semi-products. Experimental investigations show that besides natural local discontinuities like knots or resin inclusions, the screw-to-grain angle and the screws stiffness have an influence on the insertion process and thus can be identified as factors to a deviation of fully threaded screws. Mechanical predrilling cannot solve this problem, as the drills also stray during the predrilling process. As an alternative, a pyrolytic method of predrilling based on laser radiation proved suitable for obtaining guide holes with adequate straightness. This paper includes a description of the developed drilling processes using different lasers beam sources. The resulted borehole geometries of a QCW fiber laser, as well as an ultrashort pulsed laser, show satisfying results. Furthermore, the short- and long-term bond behavior of fully-threaded screws in a glued-laminated timber matrix, installed in laser predrilled guide holes, was tested and evaluated. The results show that with the new innovative wood processing method an exact positioning of fully-threaded screws is possible, almost without loss of withdrawal resistance of the screws. [ABSTRACT FROM AUTHOR]

An optimal bucking strategy that allocates cutting patterns to forest stands based on the individual characteristics of each stem is critical for maximizing value recovery. However, cutting patterns are usually excluded from bucking algorithms due to the difficulties associated with capturing tree quality features when collecting forest inventory data (e.g. branchiness and tree shape). This paper presents a non-destructive and fully automated methodology for the optimal bucking of stems based on terrestrial laser scanning (TLS) point clouds that aims to maximize the economic value of trees in a forest stand. It is based on the three-dimensional modelling of stems and includes the diameter and curvature of each log. The bucking algorithm also considers several timber products and calculates the most valuable log combination for each tree. The methodology was tested in a Pinus radiata plot with 120 trees, and the results were compared with those obtained with input data that do not take curvature into account: i.e. only diameters from TLS and taper equations. The analysis of the results suggests that not including curvature in the algorithm for optimal bucking results in an overestimation of the commercial value of timber products. [ABSTRACT FROM AUTHOR]

The operation of laser marking occurs due to oxidation on the metallic surface at a high temperature, which finds applications in many organisations due to its cleanness and high handling speed with the negligible human association. The generated marked objects are permanent in nature, generally utilised for product identity. From the perspective of laser marking, the general requirement of laser marking is mark clarity or marking quality with minimal effect on the workpiece surface. The paper deals with producing good-quality laser-marked surface by the utilisation of process parameters such as transverse feed, average laser power and scanning speed, which seem to have a significant effect on the surface of designed materials for the development of laser marking qualities. The diode-pumped pulsed fibre laser was utilised for the purpose of marking on the surface in a single pass within the minimum possible time. Experimental studies revealed that decrease in transverse feed from 8 μm to 2 μm/laser stroke had a projection towards the increase in mark intensity which could be reached up to 0.95 on the application of the lower value of transverse feed, i.e., 2 μm/laser stroke upon using a proper set of process parameters.. [ABSTRACT FROM AUTHOR]

In this paper, 20Mn2SiCrMo bainitic crossing noses were repaired by depositing 420SS, Stellite 6, 17-4PH and 18Ni300 alloys on the rail surfaces to form functionally graded materials (FGM) using laser directed energy deposition (L-DED) technology. As a result, only 18Ni300 deposit achieves an excellent strength-toughness combination, which possesses a yield strength of ~1120 MPa together with an impact energy of ~85.05 J, better than those of substrates (~1071 MPa, ~71.34 J). Besides, the wear and rolling contact fatigue (RCF) resistance of 20Mn2SiCrMo/18Ni300 FGM is enhanced to 2.7 and 23.6 times as much as those of substrates. Massive ultrafine nanoprecipitates and a small amount of austenite make 18Ni300 deposit strong enough as well as a certain work-hardenability, ensuring good wear resistance therein; the significant RCF resistance originates from the improved shakedown limit. Therefore, all findings reveal that 18Ni300 is the most promising depositing material for repairing bainitic crossing noses by L-DED. [ABSTRACT FROM AUTHOR]

Chimneys are architectural elements of difficult access and analysis in heritage buildings. This paper presents a method for automatic modelling of round brick chimneys and analysing their inclination, straightness and surface. The method uses as input data point clouds acquired with a Terrestrial Laser Scanner. Four chimneys have been surveyed on the north face of Bragança Dukes' Palace in Guimarães, Portugal. The method consists of two main processes. First, the point cloud of each chimney is segmented into circumferential sections and adjusted to cylinders by applying Maximum Likelihood Sample Consensus. From the set of centroids, the inclination and the straightness of the chimney is estimated. Second, the point cloud chimney is segmented longitudinally and adjusted to finite planes. The distance estimation between the input point cloud and the modelled planes allows detecting the lack of bricks or mortar erosions. The proposed method allows estimating characteristics in chimneys even if the chimneys have not been completely acquired. [ABSTRACT FROM AUTHOR]

The basic requirement in this type of micro-drilling process is to achieve high product quality with the minimum machining cost, which can be realised through parameter design. In this paper, we propose a new economic parameter design under the framework of Bayesian modelling and optimisation. First of all, the Bayesian seemingly unrelated regression (SUR) models are utilised to develop the relationship models between input factors and output responses in the laser micro-drilling process. After that, simulated response values which reflect the real laser micro-drilling process are obtained by using the Gibbs sampling procedure. Moreover, a novel rejection cost function and a quality loss function are constructed based on the simulated responses. Finally, an optimisation scheme integrating the rejection cost (i.e. rework cost and scrap cost) function and the quality loss function is implemented by using multi-objective genetic algorithm to find feasible economic parameter settings for laser micro-drilling process. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for automatically generating 3D models of individual shrubs from point clouds acquired by Terrestrial Laser Scanning (TLS) devices. The creation of accurate 3D models for shrubs holds significant value for ecological studies. The shrub modelling is more challenging compared to other tree modelling tasks, due to the presence of substantial noise and fuzzy branch structures. To address these challenges, our approach first partitions the input point cloud into two categories: branches and others. This point segmentation process effectively eliminates interference of leaves and noise, thereby enhancing the visibility of branch skeletons. Then, we construct a triangulation network using the branch points and establish a minimum spanning tree (MST) based on this network. Serving as the initial skeleton representation of the plant, the MST preserves the essential topological structures of the branches. Within the extracted MST, we implement a recursive trimming technique to eliminate redundant branches by merging adjacent points and edges, ultimately consolidating the skeleton structure. Finally, we employ an adaptive cylinder fitting algorithm that relies on robust principal component analysis (RPCA) to generate the model. The effectiveness and robustness of the proposed method are demonstrated via experiments on different datasets, with an average fitting error of 1.13 cm, indicating that our approach can achieve high accuracy in modelling individual shrubs. [ABSTRACT FROM AUTHOR]

This paper proposed a new piezoelectric transformer structure based on shear vibration modes. The difficulty in the preparation of shear vibration piezoelectric transformer was minimised using the integrated structure design. The transformer working mode was determined using a finite element simulation and laser vibrometer. A transformer preparation methodology was designed, and the transformer samples were fabricated. The test results showed that by optimising the area ratio between the input and output of the piezoelectric transformer, its voltage ratio, operating frequency, efficiency, and other parameters can be adjusted. The piezoelectric transformer samples were tested at 110 kHz. The maximum variable voltage ratio and efficiency can reach 34.1 and 91%, respectively. [ABSTRACT FROM AUTHOR]

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This paper describes the use of laser vibrometry and thermal non-destructive testing for detecting defects in GFRP composite by applying a single test procedure. The laser vibrometry involves the averaging of vibration amplitudes over an entire frequency spectrum accompanied by the frequency-phase analysis. Such procedure may lead to suppression of low signals, produced by smaller and deeper defects, by higher signals conditioned by larger and shallower defects. The fusion of results obtained with both laser vibrometry and thermal NDT was used to enhance defect detectability. The corresponding experimental techniques were applied to detecting four types of defects (air gaps, foam, blank grooves, resin) in GFRP composite, as well as evaluating defect size and depth. Also, laser vibrometry was used to characterise barely visible impact damage in CFRP composite, and test data was compared with C-scan ultrasonic inspection results. It has been shown that the results supplied by three inspection techniques have been reasonably consistent in characterisation of defect lateral area and depth. When analysing the complex structure of impact damage in composites, the detection of both shallow and deep defects can also be enhanced by performing fusion of test results supplied by laser vibrometry and active thermal NDT. [ABSTRACT FROM AUTHOR]

This paper proposes a multiple-input multiple-output (MIMO) terrestrial-satellite laser communication uplink system based on optical spatial modulation with medium-based modulation (OSM-MBM) joint modulation. The Málaga(M) distribution is used to describe the combined effects of near-ground turbulent light intensity scintillation, beam wander and angle of arrival fluctuation. The closed expression of the bit error rate (BER) of the OSM-MBM joint modulation MIMO terrestrial-satellite laser communication uplink is derived. The simulation analyzes the influence of transmitting radius, receiving aperture, beam divergence, zenith angle and signal-to-noise ratio on the system error performance, and compares it with traditional modulation, media-based modulation and optical space modulation. Finally, the experiment is verified by Monte Carlo. This research provides a theoretical reference for the engineering realization of the modulation technology for the MIMO terrestrial-satellite laser communication uplink system. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has recently become more popular for the chemical analysis of several types of materials of forensic interest. The Raman technique allows the measurement of the inelastic scattering of light due to the vibrational modes of a molecule when irradiated by an intense monochromatic source such as a laser. Forensic laboratories must often work with small samples in order to determine the type of material and its possible manufacturer for investigatory and evidence purposes. This paper describes the analysis of a color photocopied document for the identification of the particular type of toner used in the generation of the document. [ABSTRACT FROM AUTHOR]

Airborne laser scanning (ALS) has recently been identified as a potential tool in topographic mapping for archaeological prospection. However, most existing applications in this field refers to manned ALS systems, for which the high operation and maintenance costs limits its application in small-scale archaeological investigation. In this paper, we conducted an exploratory study on the application of the unmanned aerial vehicle (UAV) laser scanning (ULS) system in ancient micro-topography detection over wooded areas. Compared with manned ALS technology, we analyzed the advantages and potentials of ULS technology for archaeological applications. Then we outlined existing mainstream survey-grade UAV-based laser scanners, data processing and visualization approaches. Furthermore, we performed case studies in three cultural heritage sites in Zhejiang Province, China using two representative mainstream survey-grade ULS systems. Results were then verified by an in-site investigation. Finally, the correct selection of ULS devices, the planning of data acquisition missions and the use of appropriate data processing methods specifically for archaeological prospection were discussed. This paper provides a cost-effective and flexible solution for micro-topography detection in wooded areas. ULS technology, as demonstrated here, can be an important supplement to existing archaeological investigation methods, particularly for small-scale areas, and has promising prospects in archaeological applications. [ABSTRACT FROM AUTHOR]

Recent years have seen a considerable research interest in multiferroic materials for their potential application as sensors and actuators. However, the scarcity of these materials in a single phase and the weak coupling of their ferroic components have directed research toward multiferroic heterostructures. These systems operate by coupling the magnetic and electric properties of two materials, generally ferromagnetic and ferroelectric, via strain. In this paper, thin films have been grown by chemical solution deposition (CSD) using spin coating technique using rotations peed of 4500 rpm and time of 50 s and dried at 120○C for 20 min. The optical, dielectric, magnetic, ferroelectric, ferromagnetic, and piezoelectric properties of thin films have been investigated by Uv- Visible spectrophotometer (300-2500) nm, X-Ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM), Transmission Electron Microscope (TEM), and Scanning Electron Microscope (SEM) respectively. PZT/CFO thin films deposited at different temperatures from 400 °C, 500 °C and 600 °C. The as-deposited PZT/CFO show week piezoelectricity and the effective piezoelectric coefficient d33 because the materials deposited on the films not only the PZT layer but also the CFO layer, which decreases the piezoelectricity of these films. PZT/CFO Films were then recorded to enhance all physical properties (dielectric, optical, structural, surface morphology, and magnetic properties) as the sintering temperature increased. The images of a thin film before and after treatment with Nd-YAG, which have Power from 10 mw to 5300 mw, Pulse width: 7 ns pulsed laser, Repetition Rate: 10 HZ, and wavelength spectrum in (IR, Vis) laser beam indicate that sample prepared before treated has a lot of porous and agglomeration which decreases after treatment. [ABSTRACT FROM AUTHOR]

The successful implantation depends on the favorable biocompatibility of the implant. In this paper,microgrooves on the surface of Ti-6Al-4V titanium alloy implants were made by laser processing technology,scanning electron microscopy and surface profilometer were used to observe the laser textured titanium samples,firstly. Then, the liquid-solid contact angle-measuring instrument was used to characterize the wettability of titanium samples. Finally,using a microplate reader and laser confocal microscope, the cytological behavior of cell proliferation, adhesion, differentiation, and cell morphology on the surface of different samples were studied.It showed that laser microgrooved surfaces had reduced liquid-solid contact angles,increased surface roughness,and better proliferation and differentiation of osteoblasts, while most cells grew along the microgrooves. These results indicate that the increased wettability provides a better growth environment for cell growth. Microgrooves are crucial in cell contact guidance, while their parameters control cell behavior and deserve an in-depth study. [ABSTRACT FROM AUTHOR]

To avoid and eliminate cracks on the surface of a workpiece, it is very important to quantitatively analyse the temperature field, stress field, and flow field during the laser cladding process. This paper uses the finite element method to establish a multiphysics coupling model based on the laser cladding process of a disc laser. The thermophysical parameters of the base material ASTM 1045 and the powder material Fe60 are calculated by the CALPHAD method. In the modelling, the mutual influence between the light powder is considered but also the influence of the surface tension and buoyancy of the liquid metal in the molten pool on the flow of the molten pool and the dynamic change of the cladding layer morphology are considered. In the laser cladding process, the distribution and change law of the temperature field, flow field, and stress field are obtained. An infrared thermometer was used to measure the temperature during the cladding process, and a Zeiss-ƩIGMA HD scanning electron microscope was used to observe the outline of the cladding layer, which verified the accuracy of the mathematical model. The response surface model was established by the CCD method, and the influence law of the process parameters on the cladding layer was determined. The influence of laser power, beam radius, and scanning speed process parameters on the changes of temperature field, flow field, and stress field in the cladding process was analysed, providing an effective way to reduce residual stress. [ABSTRACT FROM AUTHOR]

In recent years, product sizes have decreased and products have become more multifunctional; process integration has been increasingly important for this purpose. Typically, laser hardening leaves an oxidised scale on the machined surface. This study aims to remove this oxide scale. Herein, we propose a laser hardening–forming process that combines laser hardening and laser forming. To successfully remove the oxide scale, we conducted a polishing process using nanofibers, which was compatible with numerical control (NC) and applicable to magnetic materials. This paper demonstrates the potential of integrating heat treatment, forming, and finishing by deploying an NC machine to construct origami engineering for thin plates. [ABSTRACT FROM AUTHOR]

Flexible electronics are attractive because of flexibility and portability. The circuits are printed on flexible substrates, which are delicate and heat-sensitive. Traditional photolithography, which uses high temperatures and corrosive chemicals, easily causes damages in flexible substrates. Here, we develop a low-cost nanoparticle based laser patterning process for fabrication of flexible electronics. Nanoparticles are sintered using a low-power laser as they are selectively deposited. Copper and silver particles were successfully deposited on paper and polyethylene terephthalate substrates. The effects of process parameters on deposition performance were studied to understand the process-structure–property relationship. The thermal effects of the laser on film morphology were observed. The sensitivities of the electrical properties with respect to the porosities at different laser power densities were analysed. With different laser energy levels, the process allows for selective deposition, properties control of printed patterns, and flexible substrate cutting. The fabrications of strain sensor and kirigami electronics were demonstrated. [ABSTRACT FROM AUTHOR]

Recently, the super-resolution network PT-SRGAN was developed for faster pavement texture measurement using 3D laser technology at 0.1 mm resolution from only six predetermined faster speeds. This paper further introduces an extended application of PT-SRGAN in combination with bicubic interpolation to enhance the low-resolution 3D pavement data collected at any speeds for more flexible practices. The research team collected two datasets on ten field pavement sections: (1) Dataset-1 was the true 0.1 mm 3D texture data collected at very low speeds (<1.5 mph); and (2) Dataset-2 was the low-resolution 3D texture data collected at three faster speeds (7.5, 15, and 30 mph). The efficacy of the extended PT-SRGAN was validated by reconstructing 0.1 mm data from manually downsized low-resolution Dataset-1 and real low-resolution Dataset-2. First, the superior performance of the proposed method was demonstrated by examining two evaluation metrics calculated between ground truth and reconstructed images at different speeds using Dataset-1. Further, seven 3D areal texture parameters were calculated and averaged for reconstructed Dataset-2, and compared with those of Dataset-1 to demonstrate that the proposed method shows promising performance to enhance real low-resolution 3D texture images to 0.1 mm data for any faster pavement texture evaluation. [ABSTRACT FROM AUTHOR]

Flotation has been used to treat coal over the last century. However, the conventional flotation condition can hardly be applied to ultrafine coal slime (UCS). An alternative combined method, which has the potential to improve UCS separation efficiency, is using high-shear pretreatment (HSP) and polymer regulator. Presented in this paper are the findings from an investigation into the flotation performance and aggregate characteristics of UCS with the assistance of HSP and polyvinylpyrrolidone (PVP). Electrokinetic, laser particle size, and rheology experiments were employed to analyze the influence of HSP and PVP on ultrafine particles. The UCS studied has a high ash content of 53.62%. The flotation results were analyzed through flotation efficiency and selectivity indexes. The results show that the flotation concentrate has less gangue entrainment and high combustible recovery, low ash content (12.74%) and higher flotation efficiency (66.26%) were obtained. Moreover, the results of flotation kinetics illustrate the advantage of using PVP, which improves the cumulative combustible recovery and flotation rate. The introduction of HSP was conducive to the improvement of separation selectivity. These findings provide fundamental insights into the effect of HSP and PVP on ultrafine particles and offer an effective technique for the enhancement of UCS flotation. [ABSTRACT FROM AUTHOR]

3D digitization methods have become essential tools in cultural heritage practice. Methods like laser scanning and photogrammetry are being widely applied for the conservation of priceless objects and for enabling audience engagement with history. Such data have value as a new wave of multisensory museum practice ripples through the sector and could provide a perfect use for the enormous corpus of 3D data in cultural heritage. This paper documents such an application, where laser scanning has been used in conjunction with 3D printing to re-present the Chichester Roman tablet, an object of key importance in early Romano-British history, to new audiences. It details the process used to digitize the tablet and recreate different versions of its missing text and its state of preservation. It describes how such data can play a role beyond just documentation. Discussed is how such approaches enrich families' engagement in cultural heritage and how such material can used as didactic material in higher education. [ABSTRACT FROM AUTHOR]

In the present work, a fully coupled thermo-mechanical analysis is presented to obtain the desired bend angle in the sheet made of AM30 magnesium alloy. The finite element method (FEM) based software ABAQUS 6.10 is employed to estimate the temperature, stress and strain distribution with time for different laser bending process parameters. An FEM proposed model is validated with the experimental results. Some parametric study has been performed to see the influence of laser process parameters on AM30 alloy. Single and multi-passes laser line heating is employed, and observed that the bend angle achieved in multi-passes is approximately 430% higher than the single pass. Hence, the results presented in this paper can be used to assess the applicability of AM30 magnesium alloy in laser-based forming industries. [ABSTRACT FROM AUTHOR]

In this paper, the shaft parts of failed machine tools were treated by laser cladding, and the shaft surface of 45# steel matrix was repaired. The microstructure, hardness and corrosion resistance of the cladding layer and quenched phase transformation zone were analyzed by metallographic microscope, Vickers microhardness tester, and friction and wear tester. The laser cladding layer was tested by friction and wear tester. The results showed that the friction coefficient of laser cladding layer was only 0.58, and it fluctuated slightly. The corrosion resistance of laser cladding layer was obviously increased. [ABSTRACT FROM AUTHOR]

Specific forms of the travelling and trapped vector mode functions for a three-dimensional Fabry-Perot cavity are developed from the general results of the preceding paper, with parameters describing the output cavity mirror chosen for a typical high Q cavity case. Cavity and external quasi-mode functions associated with the quasi-mode theory of macroscopic canonical quantization are then obtained via an idealized choice of output mirror parameters. The coupling constants describing photon exchange processes between the single cavity quasi-mode associated with each Fabry-Perot resonance and various external quasi-modes are calculated, and their slow dependence on the external quasi-mode frequency shows that the conditions for irreversible Markovian damping of the cavity quasi-mode are satisfied. For radiative atoms placed in the cavity the coupling constants for energy exchange processes with sideways travelling external quasi-modes also vary slowely, so that Markovian spontaneous emission damping occurs for the radiative atoms. However, their coupling with the isolated cavity quasi-modes is associated with reversible photon exchanges as represented via one photon Rabi frequencies. The standard model in cavity quantum electrodynamics, in which the basic processes are described by a cavity damping rate, a radiative atom spontaneous decay rate and an atom-cavity mode coupling constant has now been justified in terms of the quasi-mode theory of macroscopic canonical quantization. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the bond strength of a universal adhesive system to dentin prepared with SiC paper or an Er,Cr:YSGG laser using different bonding strategies (etch-and-rinse versus self-etch mode). Ninety-six extracted caries-free, sound human molars were used. The teeth were longitudinally sectioned in the mesiodistal direction and were wet polished with 600-grit SiC paper to obtain a standardized flat dentin surface. All prepared teeth were randomly divided into two groups, according to the surface preparation method: GroupI:an erbium, chromium:yttrium,scandium, gallium, garnet laser; Group II: silicon carbide paper[SiC] (n = 48). Each group was then assigned into three subgroups according to the universal adhesive’s (Single Bond Universal) bonding strategies: (a) etch-and-rinse mode with phosphoric acid, (b) etch-and-rinse mode with a laser, (c) self-etch mode (n = 16). For surface preparation, the Er,Cr:YSGG laser was used at 3 W, 30 Hz with 140 μs pulse duration for 25 s. For etching mode, the laser was used at 1.5 W (60% air, 70% water). Cylinders of composite were fabricated on the bonding area and shear bond strength was determined using a universal testing machine. Failure modes were evaluated using a stereomicroscope. The data were analyzed using two-way ANOVA followed by the Bonferroni test (p < 0.05). Bonding strategies showed statistically significant differences in both the SiC-and laser-prepared groups (p < 0.05).Universal adhesive used in etch-and-rinse mode with acid showed significantly higher bond strength values than in self-etch mode (p < 0.05). The bond strength values did not differ according to the surface preparation method (p > 0.05). Irrespective of preparation method, using universal adhesive in etch-and-rinse mode with acid might improve dentin bond strength. Laser preparation did not affect the bond strength of the universal adhesive tested. [ABSTRACT FROM AUTHOR]

This paper presents a real-time position control solution for the targets used in the high-repetition rate laser operations of high-power laser facilities. The control system is designed based on an Abbe-compliant, in-process position measurement system of targets, employing a plane mirror interferometer and a five degree-of-freedom hybrid mechanism. An error model is developed to characterise the position feedback information of target for a high-repetition rate process to determine the effects of the non-collocation of the sensor's measurement point and target on the control system's performance – a challenge for the real-time position control of targets. Behaviour of the control system is investigated with the error model and experimental data. It is found that a controller's position compensation scheme can be ineffective due to the erroneous position feedback as a result of the non-linear position information associated with the non-collocated measurement point and the actual target. To solve the problem, an angular compensation technique is proposed. [ABSTRACT FROM AUTHOR]

Additive manufacturing is being increasingly focused on the production of end-use parts. Compared to the prototyping application, the production of end-use parts demands a higher level of repeatability and process quality. To achieve this, increased knowledge is required about the influence of various process parameters on the part characteristics and the parameter interrelations. Design of Experiment methods can be applied to gain knowledge on the process behavior, but the applicability of different DoE methods for AM processes has to be validated. This paper describes the application of a definitive screening design for the identification of influencing parameters in Laser Powder Bed Fusion of CoCrW alloy. The impact of various hatch parameters on the part porosity is analyzed. The experimental setup and results are described. The results are validated in an additional test series, comparing the part quality achieved by parameter-sets obtained by different optimization approaches. Furthermore, the correlation of the porosity towards mechanical properties is investigated. Finally, the opportunities and limitations of the method are discussed. [ABSTRACT FROM AUTHOR]

Structural inspection often requires slowing down the traffic during the operation by limiting the number of passing vehicles or deviating the traffic. One of the possible inspection techniques is by laser scanning. Because of the high cost of use and data treatment, the laser technique is mainly applied either in specific structures or structures with a specific behaviour. The fact that all the huge number of measurements collected by laser would not be needed, can also discourage structure owners to invest in this measurement technique for the common inspection. This paper presents an easy-to-use method for structural inspection to monitor its behaviour during the service life. A data processing method is hence suggested by adjusting a reference plane to the structure area, meshing the structure with a grid depending on the model accuracy and creating an interpolation surface applying the Kriging procedure. Two case studies were presented to illustrate the accuracy of the method and its feasibility on large structures. [ABSTRACT FROM AUTHOR]

Domestic robots are often required to understand spoken commands in noisy environments, including service appliances' operating sounds. Most conventional domestic robots use electret condenser microphones (ECMs) to record the sound. However, the ECMs are known to be sensitive to the noise in the direction of sound arrival. The laser Doppler vibrometer (LDV), which has been widely used in the research field of measurement, has the potential to work as a new speech-input device to solve this problem. The aim of this paper is to investigate the effectiveness of using the LDV as an optical laser microphone for human-robot interaction in extremely noisy service environments. Our robot irradiates an object near a speaker with a laser and measures the vibration of the object to record the sound. We conducted three experiments to assess the performance of speech recognition using the optical laser microphone in various settings and showed stable performance in extremely noisy conditions compared with a conventional ECM. [ABSTRACT FROM AUTHOR]

Laser hardening process attracted attention because of its ability for a local heat treatment method without cooling solution. The local heat treatment with small power density can result in small deformation of the workpiece, which can perform without post-process for the finish. However, such superior features can be demonstrated in the case of a workpiece with large volume and heat capacity for self-cooling. Small and thin parts might not have enough volume and heat capacity for showing the features. Therefore, we proposed a novel process to complete heat treatment and deformation-less process only using a laser. The process has a laser irradiation for hardening and another laser irradiation for deformation correction. In the present paper, a fundamental study on hardening and deformation was carried out. Experimental results showed that the deformation phenomenon was complicated and quenching was difficult in laser hardening for small thin parts. Therefore, by considering factors, a method to improve was suggested. From these results, deformation and hardening phenomena occurring during laser irradiation of small thin parts were examined, and the adaptability of the proposed dummy irradiation method was shown. [ABSTRACT FROM AUTHOR]