This study addresses the issue of dispersed fatigue outcomes and anisotropic behavior in fatigue specimens produced by selective laser melting (SLM). The fatigue life (S-N) curves and microstructures of AlSi10Mg alloy, fabricated via SLM and subsequently subjected to Hot Isostatic Pressing (HIP) treatment, were compared and analyzed. The results showed that the fatigue life in X(Y) direction of AlSi10Mg is better than that in Z direction, because of the difference in the distribution direction of defects, attributed to the directional distribution of defects influenced by the SLM forming process. The fatigue strength in the X(Y) direction is 28% to 49% greater than in the Z direction under equivalent fatigue life conditions. After hot isostatic pressing treatment at 490 ℃, the difference of fatigue life in two directions is obviously decreased compared to the SLM specimens, which was due to the large size defects was closed after hot isostatic pressing treatment. Moreover, the microstructure coarsening and Si phase coarsening during hot isostatic pressing process led to the decrease of fatigue strength, especially for fatigue tests at high stress level.

This study focused on the preparation of CoCrW alloy coatings on K417G alloy substrates using laser deposition technology. The influence of laser process parameters on the dilution rate of the coating was investigated, and the parameters were optimized accordingly. Multi-pass multilayer coating preparation tests were then conducted to analyze the microstructure, microhardness, and frictional wear properties of the coating. The experiments results showed that: Laser power and scanning speed have a large impact on the dilution rate of the coating, and reducing the laser power and scanning speed can effectively reduce the dilution rate. The coating prepared by the optimized laser process parameters has good macroscopic morphology and no internal cracks, the microstructure from the bottom to the top of the coating is columnar crystal and equiaxed crystal, respectively. The main phases of the coating are the -Co, M7C3, and M23C6.The average microhardness of the coating is 605.97 HV, which is 1.8 times of the average microhardness of the substrate. Under room temperature friction conditions, the average friction coefficient of the coating is 0.37, and the wear amount is 0.8 mg in 20 min, compared with the matrix, it is reduced by 55% and 37% respectively. The coating′s wear mechanism was slight abrasive wear with adhesive wear, while the substrate′s wear mechanism was severe abrasive wear with adhesive wear.

To enhance the welding quality of vehicle power battery pole ears, a nonlinear transient thermo-structural coupling analysis model was developed for 1050/6061 heterogeneous aluminum alloy sheets using the ANSYS simulation platform. The Gaussian surface heat source was applied using APDL language, and the temperature and stress fields of laser deep penetration welding were simulated under specified process parameters. The simulated molten pool shape and size were compared with experimental results, showing good agreement and reliability. The rapid heating and cooling of the laser beam resulted in a large temperature gradient near the heat source and dense isotherms. Stress concentration at the weld center was identified as the main cause of small cracks and other defects in the welded joint, suggesting the need for annealing treatment to reduce equivalent residual stress after welding.

The effect of process parameters on the filling and contour defects of SLM AlSi12 alloy was studied systematically, and the mechanism of different defects was analyzed, and the controlling method was proposed. The results show that AlSi12 alloy is free from cracks, exhibiting only gas and unfused pores. In the filling area, the pores change from unfused pores to gas pores with the increase of laser power. However, pores changed from gas pores to unfused pores with the increase of the hatch spacing and scanning speed. In the contour area, unfused pores appear when the line energy density is too low(0.10 J/mm), and the contour and filling area can not be well combined. The contour and the filling area are well combined when the line energy density is too high(0.60 J/mm), but the pores appear. The mechanism of unfused pores is: the input energy of powder bed is low, the liquid phase is less and the viscosity is higher, the liquid can not be well spread. The mechanism of gas pores is: the input energy of powder bed is high, the metal is vaporized strongly and the melting pool is stirred violently, and the involved protective gas is difficult to escape under the keyhole mode. By adjusting the process parameters to control the depth and width of melting pool, the good overlap is achieved and bubble escape is guaranteed. Consequently, the filling area and the contour area are densely fabricated, and the density reaches 99.9%. The mechanical properties are excellent：the ultimate tensile strength, yield strength and elongation of AlSi12 fabricated by optimal process parameters are 422.6~446.9 MPa, 280.4~295.4 MPa and 9.8~13.0% respectively, which are significantly superior to those of ZL108 alloy.

This study systematically investigated the effects of groove type and welding parameters on droplet transfer, arc shape, and weld formation during laser-MIG hybrid backing welding of 20 mm thick 6005A-T6 aluminum alloy for rail trains. The results indicated that U-shaped groove with root face height of 10 mm was more conducive to obtaining stable welding process. The arc shape was stable and no spatters when the arc current was 280 A, the main types of droplet transition were spray transfer and jet transfer. The arc was easily attracted by the side wall and welding spatter was large when the arc current was low. The stability of the arc reduced and the droplet affected the weld formation by spherical melt transition. The droplet transition frequency increased slightly as the welding speed increased, and the welding fish scales became more obvious. The laser could compress and stabilize the arc form when the heat resource distance was about 3 mm, and the coupling effect of the heat source reduced if the distance between heat sources was too large or too small.

In order to improve the measuring accuracy of metal wire diameter, this work discusses the experimental scheme of laser diffraction method. Firstly, the theoretical formula for calculating a slit width is derived from the generation conditions of dark stripes in Fraunhofer single slit diffraction. According to Babinet theorem, The filaments and slits that are complementary obstacles produce the same diffraction patterns and therefore the metal wire diameter can be obtained by measuring the slit width.Then the experimental procedure for measuring the intensity distribution of metal wire diffraction is described in detail. Finally, based on the measurement data, the metal wire diameter is deduced using the traditional calculation method and the programming solution method respectively. By comparing the results from the two methods, the programming solution method has a room for further improvement in measuring accuracy. This work not only improves the calculation accuracy of metal wire diameter, but also provides a guidance on the measurement of metal wire diameter.

Digital elevation models (DEMs) are fundamental geospatial data, yet traditional acquisition techniques often fall short in densely vegetated mountainous regions. The advent of unmanned aerial vehicle (UAV) LiDAR technology has enabled novel methods for DEM acquisition in such challenging terrains. This article proposes a method for utilizing UAV LiDAR to acquire laser point clouds and construct DEM through simulated terrain flights. Key technologies such as laser scanning data acquisition, point cloud preprocessing, point cloud filtering, and DEM construction are studied. Taking the pumped storage project in Guangdong Province as an example, the principles and implementation methods of UAV LiDAR simulated terrain flights are thoroughly examined. The laser point clouds are preprocessed, and an incremental and terrain-aware Delaunay triangulation filtering algorithm is proposed to effectively extract the ground points from scattered point clouds. The resulting DEM achieves high precision ranging from 0.07 to 0.31 meters. Experimental results demonstrate that this method can successfully extract ground points and build accurate DEM that meet the requirements of engineering measurement specifications. It provides a new approach and solution for constructing DEM in vegetation-covered mountainous areas, offering practical value and significance for wider application.

The reliance on imported high-precision measurement instruments in nuclear engineering construction has been challenged by the evolving international environment, impacting procurement for some enterprises. Consequently, there is a drive towards the domestic development of autonomous and controllable measurement equipment. This study focuses on the application of such equipment in the main pipeline detection of nuclear power plants, using system research and development as a foundation for on-site implementation. The operational key points are identified through the analysis of implementation concepts, and a main pipeline detection process flow is established based on field application. Comparative testing with a laser tracker assesses measurement accuracy, range, and repeatability. The system, characterized by non-contact measurement and real-time data feedback, can rapidly acquire extensive data through close-range shooting. It achieves a measurement accuracy of 0.14 mm, surpassing the 0.3 mm installation measurement requirement, and thus, better satisfies on-site needs. The findings indicate the feasibility of this system as a domestic alternative to high-precision measurement instruments in the nuclear engineering sector.

In the common-optical-path single-photon laser ranging system, there is a phenomenon that the laser emission moment overlaps the echo photon receiving time, which is called the main wave/echo signal overlapping. Overlap causes the loss of echo signals during a specific ranging period, resulting in a decrease in the probability of target detection. In this paper, the conditions for the occurrence of the main wave/echo signal overlapping phenomenon are studied by analyzing and calculating the structure of the ranging system and time sequence of signals in ranging. The correlation between the flight time of the ranging photon and the overlapping phenomenon is obtained. The mechanism of laser emission adjustment on overlapping is described, and a countermeasure for the main wave/echo signal overlapping based on the periodic adjustment of the laser emission time interval is given. Based on this, the corresponding overall simulation and ranging experiment are carried out, and the results show that the proposed method can avoid the occurrence of main wave/echo signal overlapping to a certain extent and improve the detection probability of the target.

In industrial settings, there is a significant demand for 3D measurement of workpieces with high dynamic range surfaces. However, existing line laser monocular vision measurement methods struggle to meet the challenges of such high dynamic range scenes. In order to ensure the accuracy and reliability of 3D measurement of workpiece with high dynamic range, a high adaptability linear laser monocular vision measurement method is proposed. This method improves the laser fringe region segmentation, multi-scale adaptive laser fringe center extraction algorithm, and presents a reflection interference removal algorithm based on maximum deterministic inference. Finally, point cloud splicing, statistical filter to remove sparse outlier noise, and voxel raster filter to sampling point cloud drop processing are used to achieve reliable measurement of workpiece on high dynamic range surface. The experimental results show that the maximum measurement error is less than ±0.088 mm for the three dimensional measurement of several high dynamic range standard blocks. A representative high dynamic range workpiece lapel shaper was measured and the real 3D shape of the workpiece was accurately measured. The method proposed in this paper has high adaptability to the measurement object, the measurement results have good reliability and accuracy, and meet the general measurement requirements.

Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a prominent analytical technique for developing gas sensing systems. The near infrared absorption spectroscopy of acetylene (C2H2) at 6 523.879 cm-1 was simulated and tested based on TDLAS technology. First of all, acetylene absorption spectroscopy under different pressures is simulated based on LabVIEW software and compared with the standard absorption spectroscopy in HITRAN2020 database. The results show that the absorption spectral line simulated based on LabVIEW is in good agreement with the standard spectrum, which is very suitable for the on-line gas detection system, and has the advantages of convenient operation and strong operability. Secondly, a set of acetylene absorption spectroscopy detection system was successfully established. The relative errors of acetylene absorption line strength and self-broadening coefficient with database parameters are 2.5% and 1.201%, respectively, by measuring and calculating the absorption line of acetylene within 25 mbar gas pressure. Finally, a real-time online detection program based on LabVIEW is established, which can realize accurate real-time and fast inversion of C2H2 concentration.

A compact V-shaped resonator structure was designed, and the 1 064 nm passively Q-switched Nd：YVO4 laser pumped by 808 nm diode laser was studied and stable Q-switched pulse output was obtained by using Cr4+：YAG crystal as a saturable absorber. The maximum continuous output power of 8.35 W was obtained at the pump power of 19 W corresponding to the light-to-light conversion efficiency of 44% and the slope efficiency of 56.4%. After inserting Cr4+：YAG crystal, the pulse output with an average power of 4 W, pulse width of 24.3 ns, repetition rate of 39.6 kHz, single pulse energy of 101 J, and the maximum peak power of 4.15 kW was obtained at the pump power of 19 W.

Laser bird repelling has promising applications in agriculture, power, and aviation safety with its excellent performance. To safely and efficiently expel birds, the mechanism of laser interaction with the internal tissues of the bird′s eye needs to be studied. Firstly, the Pennes biological heat transfer equation and the Beer-Lambert equation are used to establish a three-dimensional dynamic model to simulate the absorption and transmission of laser light in the bird′s eye tissue. Secondly, the steady-state simulation is used to analyze the temperature change of the bird′s eye under different conditions, and the steady-state results are used as the initial value of the transient study to improve the accuracy of the simulation results. Finally, a laser bird-repelling experimental platform was established and experimental studies were conducted. The results showed that the temperature of the anterior part of the bird′s eyeball was greatly affected by the ambient temperature and tear evaporation, while the temperature of the posterior part was relatively stable. During laser irradiation, the highest temperature was observed on the retina, with variations of up to 13 ℃ among different tissue regions. When using a light spot diameter of 3.5 mm, a laser power ranging from 1.5 mW to 2.7 mW, and an irradiation duration of 0.4 s, the maximum temperature could be maintained between 52 ℃ and 60 ℃. Simulation and experimental validation confirmed that the determined laser parameters could effectively disperse birds without causing any harm to their eyes.

Point-to-Plane metric point cloud registration algorithm with sampling consistency initial alignment (SAC-IA) is proposed to address the problems of the current point cloud alignment algorithm relying on initial poses, low convergence speed time and insufficient accuracy. Firstly, the raw point cloud data are uniformly downsampled using voxels to reduce the dataset size and computational overhead. Secondly, feature points are extracted and characterized using Fast Point Feature Histograms (FPFH) with a normal vector angle threshold. Meanwhile, the initial transformation matrix for the point cloud is then determined via SAC-IA. Finally, Point-to-Plane metric point cloud registration algorithm is used to complete the fine alignment based on the initial alignment. The experimental results show that the algorithm significantly improves the alignment accuracy and has higher alignment efficiency than the ICP algorithm based on KD-tree acceleration.

ObjectiveTo investigate the relationship between aqueous humor cytokines and the changes of corneal endothelial cell density (ECD) after femtosecond laser-assisted cataract surgery (FLACS).MethodsThirty cataract patients who underwent FLACS at our ophthalmic clinic between February 2017 and July 2020 were enrolled. Preoperative aqueous humor cytokine concentrations were analyzed using a magnetic bead-based multiplex immunoassay system. ECD was measured using a corneal endothelial cell microscope before surgery and at 1, 6, and 12 months postoperatively.ResultsBCVA improved gradually after cataract surgery, and there were significant differences between preoperative visual acuity and postoperative visual acuity at 1, 6 and 12 months (all P<0.05). ECD decreased gradually after operation (P<0.05), with an average decrease at 1 to 6 months (1M-6M), 1 to 12 months (1M-12M) and 6 to 12 months (6M-12M). There were no significant differences in baseline aqueous humor cytokine levels, preoperative ECD, and changes of ECD at 1, 6, and 12 months after surgery between diabetic group and non-diabetic group (P>0.05). Pearson and Spearman correlation coefficient analysis showed that interleukin (IL)-7, interferon-induced protein-10 (IP-10), macrophage inflammatory protein (MIP)-1a, MIP-1B in aqueous humor were positively correlated with ECD loss from 1M to 6M (EDC1M-6M absolute value) (P<0.05). IL-1b, IL-7, IP-10, and regulated upon activation normal T cell expressed and secreted (RANTES) in aqueous humor were positively correlated with ECD loss at 1M-12M (EDC1M-12M absolute value) (P<0.05), and IP-10, RANTES in aqueous humor were positively correlated with ECD loss at 6M-12M (EDC1M-12M absolute value) (P<0.05). Multivariable stepwise regression analysis showed that IL-7 in aqueous humor was a strong influencing factor of ECD loss at 1M-6M, while IP-10 was a strong influencing factor of ECD loss at 1M-12M (P<0.05).ConclusionIL-7 and inflammatory cytokines in aqueous humor were positively correlated with ECD loss after FLACS, suggesting that these cytokines may promote the progression of ECD injury.