In order to explore the influence of process parameters, scanning method and groove shape on the thin-walled parts manufactured by laser additive manufacturing, based on the ANSYS finite element analysis software, the temperature field and stress field of the thin-walled 316L stainless steel thin-walled parts manufactured by laser additive manufacturing were analyzed by numerical simulation. The results show that a certain component of residual stress will increase if the laser power and scanning speed are too large or too small; the use of vertical cross-scanning method can reduce the residual stress, but it may cause excessive stress in the bonding area between the repaired area and the substrate. This leads to the initiation of cracks. Comparing the stress distribution of the two groove shapes, the edgeless groove shape can reduce the stress concentration in the bonding area and effectively reduce the deformation of the substrate, revealing that the substrate is deformed during the remanufacturing process. Deformation mechanism, and finally designed experiments to verify the influence of different groove shapes on the quality of laser additive remanufactured samples. The experimental results show that a good metallurgical bond is formed between the base material and the repaired area in the shape of the arc groove, which verifies the correctness of the simulation.

The microstructure, friction, and wear behavior of Fe-based and Co-based alloy laser cladding layers in a seawater environment were studied and designed to solve the surface protection and repair problems of subway ER9 wheel steel. Fe-based alloy coating and Co-based alloy coating were prepared on the surface of ER9 wheel steel by laser cladding technology, and the microstructure, phase, and chemical element composition of the two cladding layers were compared and analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS)， and X-ray diffraction (XRD). The tribological properties of the two coatings in a seawater environment were investigated by reciprocating friction testers. The results show that in the sliding friction in a seawater environment, the surface of the wheel steel substrate is covered with a large area of corrosion products and presents a large number of grooves parallel to the sliding direction. In the two cladding coatings, the iron-based alloy coating is mainly composed of solid solutions such as α-Fe, (Fe, Ni) and Cr7C3, and the average hardness (about 638.8 HV) is equivalent to that of the matrix (284.8~293.2 HV) 2.21 times, the friction coefficient is about 0.270, the wear rate is 9.64×10-5 mm3/(N·m), the wear mechanism is mainly slight abrasive wear, accompanied by corrosion wear. The crystal phases of the cobalt-based alloy coating are mainly the FeNi3 phase, γ-Co phase, and Cr23C6 phase, the average hardness (about 467.9 HV) is about 1.62 times that of the matrix, the friction coefficient is about 0.225, and the wear rate is 3.06×10-5 mm3/(N·m). The wear mechanism is mainly slight oxidative wear.

Fe60 and WC composite powders with different mass fractions were preset on the surface of 304 stainless steel, and the metal ceramic composite cladding layer was prepared by optical fiber laser processing system. The microstructure and properties of the coating were studied from the perspectives of macro morphology, microstructure, phase analysis, and hardness distribution. The results show that the metallurgical bonding of the composite cladding layer is good, and hard phases such as CrC and WCx are formed in the transition zone and heat affected zone, which improves the hardness of the cladding layer and significantly affects the mechanical properties of the composite coating. When the mass fraction of WC is 3%, the average hardness of the cladding coating is 995 HV, which is about 5 times that of 304 stainless steel substrate, and higher than that of the composite cladding coating with other mass fractions.

In order to further improve the microhardness of 316L substrate and improve its application fields, different weight ratios of Fe60-WC cladding layers were prepared on the surface of 316L substrate by laser cladding. Then the morphology，microhardness, and crystal phase composition of laser cladding layers with different ratios of WC were explored. According to the experimental analysis, when the weight ratio of WC is 3%, the laser cladding reveals eutectic structure with Fe60, and its microhardness is obviously increased. Furthermore, when the weight ratio of WC increased to 5%, the microstructure of the cladding layer reduces distinctly. The result shows that when the weight ratio of WC is 3%, the microhardness of the cladding layer is obviously higher than other simples.

The laser forming repaired (LFR) and GH4169 superalloy powder were used to prepare laser-formed repair parts on GH738 superalloy substrate specimens, which were subjected to solution + double aging heat treatment. The specimens were subjected to high-temperature endurance and high-temperature low circumference fatigue performance tests, the fracture morphology of the specimens was observed and the fracture mechanism was analyzed. When the persistent test was conducted at 650 ℃ and 690 MPa, the Laves phase was precipitated at the grain boundaries of the repaired specimens, leading to the crack sprouting. This will be separated from the grain boundary to form microscopic cavities, while the gas porosities promote the crack expansion, as a mixed ductile fracture mode of penetration and along with the crystal. Low cycle fatigue test at 455 ℃, the fatigue cracks originated from the surface and gas porosities and spread to the center in a river-like pattern, and there were fatigue glow lines in the expansion area, which were two fracture modes of transgranular and cleavage fracture. The GH4169 superalloy powder repair can meet the conventional casting and forging of GH738 alloy.

By studying the microstructure, phase composition, and atomic weight of grain boundaries and dendrite elements of the high-entropy alloy cladding layer under different parameters, the effects of process parameters on the preparation of high-entropy alloys by laser cladding were revealed. The results show that under the constant laser power, the phase structure of AlCoCrCuFeNi high-entropy alloy gradually changes from bcc phase to bcc phase +fcc phase with the increase of scanning speed. Compared with the melting and casting method, the laser cladding aluminum alloy has an additional fcc solid solution phase mainly composed of Al element. The high-entropy alloys mainly develop from dendrites at the bottom to equiaxed crystals at the top. Through EDS analysis, it is found that Al element segregates seriously, and Cu element has a small amount of segregation at the grain boundary. The scanning speed has a significant effect on the alloy quality.

The TiAlSiN coating was fabricated by laser cladding with circular and square spots on high-speed steel bit W6Mo5Cr4V2. The microstructure and mechanical properties of the coating were analyzed. The results show that BCC phase and some MC phase exist in the coating, and (Fe, Cr) solid solution is formed after laser cladding. Obvious cellular grains and many dispersed fine particles are formed in the coating, and irregular dendritic grains and carbides with granular are formed in the square spot coating, which improves the uniformity of the coating. The hardness of both the round and square light spot coatings is greater than that of the matrix. By comparison, the hardness of the square light spot coating is greater than that of the round light spot, which makes the overall distribution of the square light spot coating is more uniform. The average friction factor of circular and square spot coatings is 0.72 and 0.56 respectively. The circular light spot coating shows obvious adhesive wear characteristics, while the square light spot coating mainly shows abrasive wear characteristics.

The laser rapid repair test for 0Cr1Ni6 alloy was carried out and optical microscope and scanning electron microscope were used to observe and analyze the microstructure of the joint. The joint hardness was tested by micro-hardness test. Studies showed that the joint of Laser rapid repairing 0Cr1Ni6 alloy was divided into matrix, heat affected zone and cladding zone. The morphology of the heat affected zone has little change with the increasing of laser heat input. Similar to the matrix, it is composed of massive ferrite, austenite, carbides precipitated on that and a small amount of lath martensite. There is an obvious boundary in the cladding zone. The microstructures are mainly dendrites at the top of the cladding area is evenly distributed.I In the middle of the cladding zone, dendrite transition to columnar dendrite is observed. The lower part of the cladding zone is columnar crystal. Dendrite size increases with the increasing of laser heat input. The cladding zone is mainly composed of matrix γ phase, enhanced γ'and γ"phases, and white irregular phases δ and MC precipitated along the dendrite boundary. With the laser heat input increases, the width (D) and depth (H) of the heat affected zone have little change, only have small fluctuation within ±0.05 mm, melting width d, and melting height h gradually increase. The average hardness of cladding zone increases with the heat input per unit time, showing a trend of first increasing and then decreasing. The order of micro-hardness is cladding zone > matrix > heat affected zone.

The deposited Ti600 titanium alloy for internal combustion engine was prepared by laser rapid prototyping. The microstructure of titanium alloy in several orientations (laser scanning direction 45°, scanning direction, and deposition direction) was characterized by relevant instruments, and its static compression characteristics at room temperature were tested by MTS universal tensile machine. The results show the β phase grows epitaxially with high temperature gradient in the deposition direction, and isometric structure is produced with size approaching 400 μm. The crystal structure of dense hexagonal type is formed in all samples. At the 45° angle direction, samples present (101) preferred orientation. Many dimples and tearing edges are formed at the fracture of each orientation specimen, which show ductile fracture. According to the dimple size, the largest one is at deposition direction, follows by scanning direction and 45°. The 45° oriented samples show a higher strength with yield strength close to 890 MPa, and fracture strength being 980 MPa. The strength of samples at deposition direction and the scanning direction are basically the same. The samples (101) at 45°orientation reduce the grain coordination ability during the deformation stage and inhibit the deformation process so as to produce the highest grain strength and low plasticity.

The internal conductive pathway distribution of conductive composites prepared for traditional molding processes is uncontrollable, and it is difficult to match the electrical and mechanical properties of composites. In this paper, the selective laser sintering technology was used to rapidly prepare the diamond-like graphite skeleton blank, and the electrical and mechanical properties of the graphite skeleton were improved by secondary curing, vacuum pressure impregnation of phenolic resin solution and high temperature carbonization. The epoxy resin was "composited" with it, and graphite-epoxy composite conductive materials were prepared. Through orthogonal experiments, the effects of structural parameters of graphite skeleton on the conductivity and bending strength of conductive composites were studied. Results show that the bond radius R is the main factor determining the conductivity of the composite material, but it is a secondary factor for its bending strength. Bond length L is the main factor for the conductivity and bending strength of composite materials. When the bond length is 6 mm, the bond radius is 1.4 mm, and the bond angles is 120°, a new type of conductive composite material with mechanical properties and conductivity synergistic properties is obtained.

Based on numerical simulation tools, the radial pulse laser welding process of a pressure sensor core is simulated. The model describes the equivalent heat source formed by the laser, heat transfer and phase transformation of 316L, the transient stress field formed by heat affected zone, and residual stress formed after welding. At the same time, according to the measured depth of the molten pool formed by various laser welding process parameters, calibration of the equivalent heat source model is finished, and the deviation values are within 8%. The comparative analysis between the calculated value of residual stress and measured residual stress value by X-ray diffraction method shows that the two results are consistent, and the deviation values are within 15%. It is verified that the engineering needs of study for influence law of process parameters and parameter optimization are met by the accuracy of laser welding model.

In order to improve the binding force between the paint layer and the aluminum alloy matrix, it is often necessary to carry out hairization pretreatment. Laser microwoven processing technology has the advantages of environmental protection, high efficiency, uniform and controllable hairing surface, etc., while the laser output of the continuous laser is more stable and faster. Therefore, it is necessary to study the influence of continuous laser microwoven on the adhesion of the paint layer. By controlling the laser power, the two main parameters of the lap rate are laser microwoven processing. The three-dimensional morphology of microwoven structure was observed and characterized by laser confocal microscopy, the surface roughness Ra and contour height Rz were measured by the surface contour comprehensive measuring instrument, the abrasion and wear testing machine was used to test the coating adhesion force by scratch method, and the connection between the microwoven morphology, surface roughness and coating adhesion force was finally established. The results show that the influence of laser power on the morphological size of the microwoven fabric is obvious, the microwoven morphology of the crater and the coronal morphology which is staggered and distributed effectively improves the adhesion of the paint layer, the adhesion force is higher at 0%~20%, the average can reach 36.41 N, which is about 54%. In the scratch experiment, the contour height Rz is closely related to the adhesion force of the paint layer; and the special undulating structure effectively inhibits the large-area peeling process of the paint layer.

Laser shock peening is a surface strengthening technology that uses laser beams to modify the surface of metal materials. It has the characteristics of non-contact, strong controllability, and outstanding strengthening effects, and which is widely used in metal surface strengthening. In order to better understand the development status of laser shock peening technology, and promote scientific and technological research and innovative applications development in this field in China, This paper analyzed from multiple dimensions such as the application trends, regional layout, innovation subjects, research topics of global laser shock strengthening patents based on the Incopat patent database. The study found that laser shock peening technology is in an upward cycle of development, with the United States and Japan being important innovation subjects in this field. China has developed rapidly although started relatively late, especially in recent years. The number of patents has gradually dominated, showing strong innovation vitality. However, it is also found that the research subjects are concentrated in universities and research institutes, and the overseas layout is weak, etc. In view of this, this paper proposed development suggestions for laser shock strengthening technology in China.

This paper explores the feasibility of non-destructive extraction of urine footprints on rough paper by visible laser and quantitatively comparing the effects of footprint development. Three kinds of visible lasers and 11 kinds of visible band filters were used to take visible laser fluorescence photography of urine footprints on 4 categories of 20 kinds of common types of paper to observe the effect of footprints. The Matlab program was created, and gray-scale fluorescence luminance standard deviation index was introduced to compare the degree of footprint visualization. The study found that the band combinations of the 20 samples with the best development effect were almost different, but the 445 nm blue laser was used as the excitation light, and the 570 nm receiving filter was used to develop the urine footprints of all samples to the maximum extent, the detection rate of urine footprints was 100%. In addition to the urine footprint samples on black printer paper and newspaper with complex color background, the effective visualization rate of urine footprint samples was 90%. The results show that visible laser fluorescence photography can be used to visualize urine footprints on rough paper, and the standard deviation of gray-scale fluorescence luminance can be used to measure the degree of urine footprints development.

To address the problems that the Iterative Closest Point (ICP) registration algorithm tends to fall into local optimum and slow convergence of iterations, this paper proposes an improved ICP point cloud registration algorithm based on Intrinsic Shape Signatures (ISS) feature point combination, which firstly down samples the reference point cloud and the point cloud to be aligned with voxel grid. Then extracts the feature points by ISS algorithm and uses Fast Point Feature Histogram (FPFH) to characterize the feature points. After that, this paper finds the corresponding point pairs of the two sets of point cloud feature points, and then uses Random Sample Consensus (RANSAC) to remove the wrong corresponding point pairs. Finally, the two sets of point clouds with good initial poses are accurately aligned by the point-to-plane ICP algorithm based on Nanoflann acceleration, which further improves the registration accuracy and registration efficiency. The experimental results show that the algorithm reduces the number of iterations compared with the traditional ICP algorithm, and has a significant improvement in accuracy and speed; compared with the Scale Invariant Feature (SIFT) ICP algorithm, the Euclidean fitness score and registration time are reduced on average respectively 64.4% and 73.75%.

Aiming at the limitations of dynamic graph convolutional neural network (DGCNN) on aggregating neighbor point information, a dynamic graph convolutional neural network based on enhanced feature fusion (EFF-DGCNN) model is proposed and is used for airborne LiDAR point cloud classification. The model presents the feature enhancement module and the feature fusion module based on DGCNN, which can be applied to the classification of original 3D point clouds. Firstly, the local and global features of the original point clouds are obtained by edge convolution based on DGCNN. Then, the global features are integrated into the local features of each layer to enhance the local features, so as to highlight the importance of different features of point clouds and make the network pay more attention to the features conducive to classification. Finally, different enhanced local features are fused to obtain deep features. The fused enhanced local features are used for classification of airborne LiDAR point clouds. In order to verify the classification performance of the proposed model, experiments are conducted on the GML~~DataSetA dataset and ISPRS dataset. It is demonstrated that compared with DGCNN, the proposed EFF-DGCNN model has better classification ability and can better distinguish point clouds with similar structures.

A terahertz optical comb spectral data acquisition system based on high-speed optical asynchronous sampling (ASOPS) method is described. Two femtosecond pulse lasers with a repetition frequency difference of 50 Hz are used as the pump light and the probe light respectively. LT-InGaAs/InAlAs optical antenna is used to generate and receive terahertz signals, and a RF data acquisition system with adjustable sampling rate and optional sampling mode is used to collect time-domain signals and analyze spectral transformation. The spectral width is 0.06~4 THz and the SNR is greater than 60 dB. At the sampling rate of 301.6 MSa/s and the scanning frequency of 50 Hz, the frequency of absorption lines in the experimentally measured water vapor absorption spectrum is very close to that published in the HITRAN database, with a maximum error of 12 GHz.

Objective: Investigating the clinical effect of intravascular laser irradiation (ILIB) on subacute CCD after stroke. Methods: From June 2019 to December 2021, 48 patients who suffered from acute stroke and received brain SPECT in our hospital were selected as the study subjects, and were matched into ILIB treatment group (n=24) and conventional treatment group (n=24) according to stroke laterality, gender, infarction, hemorrhage, and other factors. Brain SPECT was performed with 99mTc-hexamethylpropioxime (99mTc-HMPAO) to detect CCD. The functional results were evaluated at 2 time points by the simple mental state examination (MMSE), functional walking category (FAC) and modified Barthel index (MBI). The functional recovery was analyzed to reveal the functional gain of each clinical score (MMSE, FAC, MBI) between the initial and subsequent evaluations. Results: According to independent T-test, there were no significant differences in MMSE, FAC, MBI, MMSE, FAC, and MBI scores in the conventional treatment group at the initial assessment (P values were 0.122, 0.106, 0.125, 0.123, 0.091, and 0.136, respectively). The recovery of FAC was worse in the conventional treatment group (P=0.001), and the mean functional recovery of MMSE and MBI in the conventional treatment group was lower than that in the ILIB treatment group, but there was no statistically significant difference in the recovery of MMSE and MBI between the two groups (P= 0.032 and 0.036, respectively). Conclusion: Intravascular laser irradiation can improve CCD and facilitate functional recovery. ILIB has a good clinical effect on CCD in the subacute stage after stroke.