Laser-CMT hybrid welding-brazing experiments were carried out on Al/steel dissimilar metals using AlCu filler wire in this work. The effects of welding parameters on the weld formation were systematically studied, and the hardness distribution, microstructure and tensile properties of the joints were also researched. The results indicated that increasing laser power, increasing wire feeding speed or reducing welding speed could improve the wetting and spreading of aluminum on the steel side, and the optimized welding parameters were obtained: laser power 2 100 W, wire feeding speed 4.0 m/min, and welding speed 1.0 m/min. The intermetallic compounds showed a double-layered structure, with lath-shaped near the steel side and needle-tip-shaped near the aluminum side. The thickness of the intermetallic compounds layer was about 2.1 μm under the optimized welding parameters, and the phase compositions of the intermetallic compounds were Fe4Al13, Fe2Al5, FeAl3, and Al2Cu. The average tensile strength of the joints was 164.9 MPa, which was 67.3% of the aluminum alloy, and the fracture mode was transgranular and intergranular mixed fracture.

To improve the erosion resistance of the Hydraulic pillar 27SiMn steel in the underground coal mine, a semiconductor fiber coupled laser was adopted to perform multi-pass lap cladding of iron-based alloy powder on the 27SiMn steel substrate, and the transverse of the obtained ferrous alloy study on cladding layer and analysis of macro-profile, microscopic structure, micro hardness, erosion resistance grade and mechanism of erosion. Results show that the dilution rate is the main consideration index. Under the process parameters of 2 000 W laser power, 15 g/min powder feeding rate, 6 mm/s scanning speed and 50% overlap rate, the best dilution rate and cladding layer with good macro morphology can be obtained. The dendrites grown in the upper part of the cladding layer will have obvious directionality. The erosion resistance level of the cladding layer is improved by 2 levels compared to the base material. The Heavily corroded area is intergranular erosion. Erosion resistance is obviously improved compared to the matrix material. This research has important guiding significance for the hydraulic column repair and strengthening engineering practice.

In order to improve the microstructure, properties and overall quality of traditional laser cladding coating, the coating was prepared by no-load ultrasonic vibration auxiliary equipment. 304L+La2O3 coating was prepared on 45 steel. The microstructure, phase composition, microhardness and friction and wear properties of the coating were analyzed. The results show that the cavitation effect of ultrasonic vibration and acoustic flow can make the grain of coating finer and improve the microstructure and properties. The average hardness of the cladding layer is 758.2 HV, which is 7.4% higher than that of the non ultrasonic process. The friction coefficient and wear loss are reduced by 6.5% and 12.9%, respectively.

This paper explores the optimal process parameters of laser cladding nickel-based WC alloy on the surface of gray cast iron to improve the surface cladding quality of gray cast iron and avoid defects due to poor selection. Single-pass coatings were prepared by using high-power semiconductor fiber-coupled laser, and the geometric characteristics of the cladding layer were measured by using Leica optical microscope. The range results were obtained by analyzing experimental data using orthogonal range method, and the influence mechanism of the process parameters on the geometric characteristics was analyzed according to the factor effect diagram. The contour diagram of the dilution rate and the aspect ratio optimizes the range of the better process parameters according to the actual needs and finally optimizes the optimal process parameters based on the actual engineering cost. The results show that three factors have a significant impact on the geometric characteristics of the cladding layer, and laser power is the main influencing factor. The optimal process parameters are that laser power is 1 400 W, scanning speed is 5.8 mm/s, powder feeding rate is 15.5 g/min. Under the optimal process parameters, the height of the cladding layer is 1 540.5 μm, the melting width is 4 680.5 μm, the penetration depth is 88.9 μm, the dilution rate is 5.46%, and the aspect ratio is 3.04, which all meet the actual needs. This research provides a theoretical basis and reference basis for engineering practice.

The SiC toughened and reinforced molybdenum silicide composite coating on the surface of nickel-based alloys was prepared by laser cladding. The effect of SiC content on the formation of cracks and pores, structural characteristics, phase composition and hardness, high temperature friction and wear, and high temperature oxidation resistance of the composite coating were studied. Results show that with the increasing of SiC content, the microhardness value increases. The high temperature friction and wear performance and high temperature oxidation performance were enhanced. When the SiC content is up to 15%, the coating has no obvious forming defects. The laser cladding layer is mainly composed of Mo2Ni3Si, MoSi2, SiC and γ-Ni phases. Its microhardness value is up to 814 HV, which is 5.4 times that of the substrate.

In order to solve the problem of failure of 45 steel parts such as bearings, gears, connecting rods, etc. under the action of alternating loads in a high temperature and high pressure environment, Ti+SiC composite coating were fabricated by laser cladding Ti and SiC powder on the surface of 45 steel. By changing the laser power, scanning speed and other process parameters during the laser cladding process, this paper investigates the general law of the influence of technological parameters on the structural evolution, microstructure and surface properties of the anticorrosive coating. Results indicated that the coatings were comprised of Ti5Si3, TiC, TiSi, Fe2C, Fe2SiTi, Fe, and Ti phases. The complex in situ formed phases were found beneficial to the improvement of the coating property, especially the surface wear resistance of TiC relative deposited coating improved significantly. Compared with 45 steel, the wear resistance of the composite coating surface of sample 3 increased to more than 36.64 times and the microhardness also showed significant improvement (5.54 times). Therefore, it can be known that with the increasing of laser specifific energy (from 4.5 kJ/cm2 to 5.8 kJ/cm2), the TiC phase was easier to be formed, and the comprehensive properties of Ti-based composite coatings have been improved. While too high laser specific energy will inhibit the formation of TiC phase and thus decrease the wear resistance, laser specific energy should be limited to a certain range.

In order to obtain dense CuCrZr alloy parts, the main forming parameters of SLM process, such as laser power, scanning speed, scanning distance, and powder spreading, were explored in the present study. At the same time, the microstructures, phases and mechanical properties of CuCrZr alloy samples were investigated. The research results showed that the laser power was the most important influence factor. Increasing the laser power could significantly increase the density of the SLMed parts. The highest density of 96.8% can be obtained under the process combination of powder layer thickness of 0.02 mm, laser power of 170 W, scanning speed of 300 mm/s, and hatching space of 0.04 mm. The yield strength of the sample was (176.7±2.1) MPa, the tensile strength was (244.7±1.2) MPa, and the elongation was 29.4%±0.9%.

The effect of simplified heat treatment regime on the microstructure and mechanical properties of point-forged laser-deposited (PF-LF) GH4169 alloy was investigated. The reduction of the aging time from 18 h to 3 h not only saved the test time significantly, but also played an important role in enhancing the material properties. Results show that after solid solution aging at 1 010 ℃, most of the Laves phase in the alloy is dissolved and the alloy recrystallizes. The recrystallized grains are small and uniformly distributed, and the average grain size is about 6.8 μm, realizing the ultra-fine crystal organization. Moreover, the strength and plasticity of the alloy also far exceed the standard of forgings. Laves phase basically disappears completely solid solution, compared with 1 010 ℃ heat treatment, the strength of the alloy has decreased and plasticity has improved, both exceed the forging standards. At 1 050 ℃ solid solution aging, recrystallization is completed. The grain size grows slightly, which is about 15 μm, and the Laves phase is almost completely dissolved. Compared with the heat treatment at 1 010 ℃, the strength of the alloy decreases and the plasticity improves, which all exceed the forging standard. When double solid solution aging was performed at 1 010 ℃ and 1 050 ℃, it was found that a large number of annealed twins appeared in the alloy, and the annealed twins had an effect on the strength and plasticity of the alloy. Although the properties of the alloy exceeded the forging standard, they were slightly lower than the properties of the alloy in the single solid solution aging condition.

Aiming at the plasma shock wave effect produced by the surface gear material 18Cr2Ni4WA in the femtosecond laser micromachining process, the pressure equation of the plasma shock wave propagation and the wavefront temperature model of the micromachining material are established. Using pulse width, energy and defocus as the changing parameters, the law of shock wave propagation radius with temperature and pressure is obtained. Experiments have verified that when the femtosecond laser pulse width is 300, 500, 800 fs, the single-pulse laser energy is maintained at 15-25 μJ. Meanwhile, the molten layer is smooth and flat, which has a good ablation effect. Under the same pulse width, excessively high energy will cause too much melted material, and the depth of the pit will deepen. As a result, the discharge effect will be reduced, and uneven wave crests will be formed on the pit wall. When using higher energy parameters to ablate the material with variable defocus amount, as the positive defocus amount increases, the edge heat-affected area increases. At the same time, the discharge effect of the plasma shock wave on the liquid material is reduced due to the defocusing change. The plasma shock wave effect model was verified, and the actual ablation effect was achieved.

One of the main problems in the development of laser cutting system was the air moves planning containing multi-layered contour lines. In order to meet the requirements of laser cutting process from inside to outside, heuristic sorting and grid sorting algorithms were proposed to achieve optimal sorting. Firstly, the position relationship of multiple nested contours was judged by ray method. Secondly, the best fitness first heuristic sorting algorithm was used. The empty distance and contour area were used as evaluation indexes, and the weight was assigned respectively to get the overall fitness. The contour with high fitness was selected as the next cutting figure. Finally, in order to meet different application scenarios, another grid sorting method was proposed. According to the density of contour control points, the grid was divided based on hierarchical clustering algorithm, and the grid was traversed according to the regular route to get the contour lines in each grid in turn. Simulation and experimental results showed that, compared with the intelligent optimization sorting algorithm, heuristic sorting and grid sorting could not only effectively shorten the air moves, but also greatly reduce the calculation time, and significantly improve the efficiency and quality of laser cutting.

Graphite/Cu composite coatings were prepared by laser-assisted low pressure cold spraying at different laser power. The cross-sectional morphology, surface morphology, microstructure, graphite content and element distribution of the composite coatings were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and image analysis software ImageJ. Results show that the continuous coating cannot be formed by single low pressure cold spraying, and the effective deposition of graphite/Cu composite coating can be achieved by laser-assisted low pressure cold spraying. With the increase of laser power, the thickness and width of the composite coating are improved to a certain extent, and the surface undulation and interfacial bonding between the coating and substrate are improved. In the composite coating prepared by laser-assisted low-pressure cold spraying, the bonding between reinforcement phase graphite and bonding phase Cu is intimate, but too high laser power can easily lead to the problems of ablation of reinforcement phase graphite and oxidation of bonding phase Cu.

LIFT (Laser Induced Forward Transfer) is a widely used micromachining technology. At present, it has gradually become one of the research hotspots of micromachining. In this paper, the level set method is used to establish the numerical model of droplet impacting solid wall in the process of laser forward transfer, and the effects of wall wettability and droplet initial velocity on the spreading morphology of molten metal droplets after impacting the wall are explored. Results show that the larger the contact angle is, the more likely the droplets are to retract and break when they hit the wall, and the greater the possibility of droplet rebound is. With the increase of initial velocity, the maximum spreading area of droplets gradually increases, and the spreading time of droplets gradually increases. In the experiment, droplets with different initial velocities are obtained by applying different intensities of laser energy. The droplet deposition point size is compared with the simulated result, and it is found that they have good consistency. Therefore, the deposition size of laser transfer droplets can be predicted by the developed simulation model.

For the backward of forest resources investigation and monitoring in China, a mechanical electronic forest box compass was developed to measure sample plot perimeter, tree height and tree coordinates. Comparing with mechanical electronic forest box compass, Blume-less hypsometer, forest compass and handheld laser rangefinder, the results demonstrated that the accuracy of mechanical electronic forest box compass in measuring azimuth, height and horizontal distance was 0.30°, 0.03 m and 0.06 m, the precision of mechanical electronic forest box compass in measuring azimuth, height and horizontal distance was 0.30°, 0.94 m and 3.53 m. The variance of mechanical electronic forest box compass in measuring azimuth, height and horizontal distance was 313.60, 1.12 and 17.97, the standard deviation of mechanical electronic forest box compass in measuring azimuth, height and horizontal distance was 17.71, 1.06 and 4.24, and the S value of mechanical electronic forest box compass in measuring azimuth, height and horizontal distance was 310.50, 1.12 and 18.05, respectively. The measurement results of mechanical electronic forest box compass were the best. The development of mechanical electronic forest box compass would explore a new way for the three-dimensional monitoring system of forest resources, especially the updating of ground investigation instruments.

The ZT1 amorphous alloy film with a thickness of 80 μm was ablated and cut in different laser (100 ns、3 ps) to study the adaptability of laser processing amorphous alloy. Results show that the thermal effect of nanosecond laser processing was obvious, typical thermal defects such as recast, crack and spatter existed, and a large range of crystallization area with special textures and colors was formed on the outside. The effect of "cold" processing was obtained by picosecond laser, and no recast, crack, spatter and crystallization were found. Under the conditions of atmosphere, multi-pulse, high laser energy density, oxidation occurred to some extent in the processing area of nanosecond and picosecond laser. The former occurred on the surface of the whole heat affected zone, while the latter only occurred in the laser irradiated zone.

Laser cleaning provides an optimal solution for industrial cleaning. However, the laser cleaning mechanism is a highly nonlinear physical process, which makes the detection of laser cleaning difficult. Through the process analysis and visual image analysis of laser paint removal process, a complete and standardized laser paint removal image data set is established. Convolution neural network framework is used to optimize the depth residual network, which is suitable for multi class paint removal detection tasks. The accuracy of 98.75% is achieved in the identification of test samples. It is proved that the deep residual network is widely used in the task of paint removal, and it has potential research significance and practical value.

In order to clean the oxide layer on the surface of the wire clamp of pure aluminum equipment, the technology of nanosecond pulsed laser cleaning the oxide layer on the surface of the wire clip of pure aluminum was studied. The influence of different power and spot overlap rate on cleaning effect and efficiency was studied by comparing experiments under different process parameters. Under the premise of high-efficiency laser cleaning, the laser cleaning process of oxide layer on the surface of wire clamp of pure aluminum was optimized by studying the influence of different repetition frequency and scanning times on the laser cleaning. Results show that: with the process setting of high power and 50% spot overlap rate, it has better and efficient cleaning effect. In the pre-foundation process, the surface would have more obvious cleaning effect if it is cleaned with the appropriate repetition frequency and scanning times. When the power is too high, spot overlap rate and scanning times will cause over surface cleaning.

Aiming at the problems of large calculation amount and low efficiency in the detection of hidden obstacles in the current UAV patrol inspection of transmission lines, a method for power line reconstruction and rapid detection and analysis of hidden obstacles based on laser point cloud data is designed. Firstly, the method extracts the power line point cloud according to the characteristics of elevation distribution, point cloud density and tilt angle, separates each power line and vectorizes it. Secondly, the method extracts the vegetation point cloud to generate a three-dimensional convex hull. Finally, by calculating the distance between the convex hull point of the vegetation and the power line vector, the efficiency of the tree barrier detection is improved, and the hidden danger information of the tree barrier in the line is quickly detected. Results show that the power line extraction results are complete and accurate, and the power line 3D reconstruction accuracy and the detection efficiency of hidden obstacles are high. This method is robust to transmission line topography, line direction, point cloud density and other factors, which greatly improves the quality and efficiency of transmission line tree barrier hidden trouble detection and provides applications for transmission line tree barrier hidden trouble detection in large-scale complex environments for reference.

Non-line-of-sight imaging technology is a new technique to detect hidden objects, which cannot be observed directly. The 3D reconstruction algorithm in non-line-of-sight imaging is mainly the back projection method. Because the back projection algorithm needs to cover the data in the Angle range of 180° to obtain a good reconstruction result, while non-line-of-sight imaging technology can only obtain partial (sparse) angle data, the back projection algorithm cannot obtain an ideal reconstruction result. To solve the sparse data problem, the system adopts the APD array to acquire data quickly, and the simultaneous algebraic reconstruction technique (SART) is proposed to reconstruct 3D image of non-line-of-sight objects. Experimental results show that the proposed approach can remove the artifacts and noise better than in the back projection algorithm on spare angle data. By calculating the peak signal-to-noise ratio (PSNR) and structural similarity SSIM, in the second and third iterations, 1.3928, 2.4663 and 0.1198, 0.2312 are improved respectively, it is shown that this method can effectively improve the image reconstruction accuracy of non-line-of-sight objects.

The appearance design of precision parts has strict requirements on the dimensional accuracy. In order to reduce the scale deviation and meet the performance index, the appearance design of complex surface precision parts based on multi laser sensor detection is proposed. The tilt angle between the sensor and the imaging axis is determined, and the internal information of the part is collected; The fuzzy set theory and membership function are introduced to smooth the collected data and reduce the noise. The coupling relationship among geometric, physical and performance parameters is established, and the geometric parameters are compensated by linear sensitivity model. Three kinds of surfaces and four frame systems are defined to express the pose relationship between constraint conditions, which are transformed into matrix form to obtain deeper pose expression, so as to detect whether the appearance of precision parts is reasonable and whether the parts are more practical. Experimental results show that this method can obtain the information of the parts comprehensively and reduce the data noise. Detection can meet the requirements of the appearance design of precision parts and make the appearance of the designed parts more accurate, which is conducive to the actual use of precision parts.

One-time matching technology is usually used in laser scanning modeling. However, when outdoor 3D landscape is in 3D environment, one-time matching will lead to the loss of a large number of laser point cloud data features, resulting in poor 3D modeling effect of outdoor landscape. A three-dimensional laser modeling method of outdoor landscape based on secondary matching technology is proposed. Firstly, SFM method is introduced into 3D laser scanning technology to obtain complete point cloud data. Control points are selected for initial registration, and two kinds of point cloud data are accurately registered by ICP algorithm. In order to improve the fusion of point cloud data, secondary matching is carried out for data color and other characteristics, and point cloud data fusion is realized. Finally, all the point cloud data are in the same coordinate, the fused point cloud data is preprocessed by denoising, filtering and point cloud splicing, and the two kinds of surfaces in the data are fitted and imported into 3D software to realize outdoor landscape modeling. Experimental results show that the three-dimensional landscape modeling with the proposed method has high stereo level, clear modeling effect and high precision.

Airborne lidar has allowed the rapid generation of high-resolution digital terrain models of large areas, but it is still difficult to automatically identify ground points and non-ground points in areas covered by dense buildings or dense vegetation. This paper proposes a mobile curve fitting least squares iterative algorithm automatically and quickly filters Lidar data. This method uses moving window weighted iterative least squares method to select seed points, and based on adaptive thresholds, it gradually filters and classifies non-ground points and ground points. Experiments in four study areas show that the new filtering method can separate the urban area and the ground and non-ground points covered by dense vegetation. For type Ⅰ errors, the error range of the new algorithm is 4.08% to 9.40%, for type Ⅱ errors, the error range is 2.48% to 7.63%, and for total errors, the error range is 5.01% to 7.40%.

In this paper, we characterize the nonlinear optical properties of copper chlorophyllin sodium salt solution and and mixed solution with sodium chloride, which provides some reference value for underwater laser communication, high intensity laser underwater detection, and other applications of intense light. In this study, the optical nonlinear effects of pure water and copper chlorophyll-sodium salt solution mixed with sodium chloride at 532 nm were measured by z-scanning technique. It is found that the optical nonlinear effect of copper chlorophyllin sodium salts increases with increaseing the concentration. However, when mixed with sodium chloridesolution, there is a distinct nonlinear anti-saturation absorption. Therefore, this hybrid material is a very good optical limiting material.

The M2-factor of partially coherent twisted vortex beam(PCTVB)in anisotropic atmospheric turbulence have been studied and numerically simulated. Results indicate that the influence of turbulence on beam propagation quality can be reduced effectively by controlling the twisted factor and vortex factor of PCTVB. The larger the twisted factor and topological charge are, the more effectively the PCTVB can suppress the influence of turbulence on beam propagation quality. Moreover, the anti-turbulence ability of PCTVB can be enhanced when twisted factor and topological charge are same sign. The M2-factor of traditional Gaussian-Schell model beam (GSMB) and PCTVB were compared, and results show that the anti-turbulence ability of PCTVB is obviously stronger than that of traditional GSMB. In addition, it is found that the influence of turbulence on beam propagation quality can be weaken by the anisotropic factor, and the influence decreases with the increase of anisotropic factor.

Sensors form the basis for the distribution Internet of Things in electricity, especially the distributed optical fiber sensors based on Brillouin scattering are widely used in this field. To improve the measurement speed of distributed optical fiber sensing based on Brillouin scattering and to lay the foundation for the condition sensing of electrical equipment based on temperature, the adaptability of the optical fiber temperature measurement method based on the slope-assisted technique is investigated. The computer programs of the spectral fitting method and the slope-assisted technique based on the pseudo-Voigt model are written. The temperature along the optical fiber for the Brillouin spectra with different signal-to-noise ratios (SNRs) are estimated by the above spectral fitting method and the slope-assisted technique. Results reveal that within a certain signal-to-noise ratio and BFS fluctuation range along the optical fiber, the accuracy of the slope-assisted technique is close to that of the spectral fitting method. However, the spectrum measurement time of the former can be shortened to a few tenth of the latter, and the corresponding computation time is only 1/758 of the latter. The influence of SNR and BFS on the error is studied. Results show that the temperature error decreases rapidly with SNR (in dB), and then it gradually tends to a stable value. The temperature error increases with the difference between the Brillouin frequency shift and the working point, and the accelerated speed also increases with the difference. The temperature error increases with the linewidth error.

To investigate the clinical efficacy of 5-aminolaevulinic acid-photodynamic therapy (ALA-PDT) combined with liquid nitrogen cryotherapy in the treatment of recurrent condyloma acuminatum and its impact on local HPV6/11 viral load. 30 patients with recurrent condyloma acuminatum were treated by ALA-PDT combined with cryotherapy once every 7-14 days for 4 times. At the end of treatment, the patients were followed up every 2 weeks and the clinical efficacy was evaluated at 3 months after the last treatment. The real-time quantitative PCR was conducted to estimate the DNA loads of HPV6,11 in the specimens collected before the combined treatment and 2 weeks after the last treatment. HPV negative rate and the changes of viral load in patients with HPV persistent positive after combined treatment were analyzed. Of the 27 patients who completed the combined treatment, six patients (22.22%) recurred within 3 months after the last treatment. Among the 27 patients, 25 cases were HPV6/11DNA positive before the combined treatment, of which 16 cases (64.00%) turned negative 2 weeks after the last treatment. The changes of viral load in the other 9 cases of patients with HPV persistent positive before and after combined treatment were analyzed by 2-ΔΔCt relative quantitative method, which showed that the viral load of HPV6/11DNA in the primary site after combined treatment was significantly lower than that before treatment (S=-22.5，P<0.01). ALA-PDT combined with cryotherapy can effectively reduce the viral load of HPV6/11DNA in patients with recurrent CA, improve HPV negative conversion rate and reduce recurrence.