To enhance the Quality of selective laser melting (SLM) parts by reducing spatter residue,a computational fluid dy- namics (cFD) model and fluid flow particle tracking model of the EOS M290 SLM eQuipment build chamber were developed.The study investigates the impact of various parameters such as inlet velocities,inlet hole diameters,inlet hole stretching lengths,and outlet grid numbers on flow field distribution and spatter particle removal within the build chamber.The findings reveal that when the diameter of 316L stainless steel spatter particles is in the range of 10-100 μm with four normal distribu- tions,the removal probability of the original model is only 69.25% when the inlet velocity is 3 m/s .The uniformity of the flow field in the build chamber can be improved and the coanda effect can be reduced by lengthening the inlet hole.The removal probability increases to74.64% when the inlet velocity is 3 m/s and the stretch length of the inlet hole is 90mm.When the in- let velocity is 3 m/s and the number of outlet grids increased from 5 to9, the uniformity indeX of outlet center plane increased from 64.42% to 78.57% .When the powder bed is not destroyed,the maXimum inlet velocity of the optimization model estab- lished by the inlet diameter of 4 mm,the inlet stretch length of 90mm,the number of outlet grids 8 is 4.46m/s,and the spat- ter removal probability is increased to 82.11% .

In this paper,the Alsi10Mg alloy samples were prepared based on the selective laser melting (sLM) techniQue,and the effect of linear energy density and volumetric energy density on relative density and pore defects were investigated.The for- mation mechanism of defects were revealed by analyzing of defect micro structure and melt pool characteristics.The results show that the relative density of different samples is obviously different for the same linear/volumetric energy density,and the relative density difference among different samples is significantly reduced by using linear energy density cooperating with vol- ume energy density.The relative density of over 99% is obtained when linear energy density is from 0.12 to 0.28 J/mm and volume energy density is from 30 to 70J/mm3.In addition,low linear and volumetric energy densities result in irregular lack- of-fusion defects that traverse multiple melt pool layers,while high linear energy density leads to the formation of circular key- hole defects with large pore sizes located at the base of the melt pool.

To enhance the wear resistance and hardness of 316 stainless steel in automotive applications,an AlcocrFeNi eutec- tic high entropy alloy cladding layer was applied to the steel surface using laser cladding technology.The micro structure,phase composition,crystallographic characteristics,surface microhardness,wear resistance and wear mechanism of the eutectic high entropy alloy coating were analyzed by metallographic microscope (OM),scanning electron microscope (SEM),electron back- scatter diffraction (EBSD),microhardness tester and reciprocating friction and wear testing machine.The specific conclusions are as follows : The phase composition of AlcocrFeNi eutectic high-entropy alloy coating is Fcc phase and Bcc phase.The re- sults of EBSD show that the grain size of the coating is about 15.34 m,and there is a high dislocation density inside the coat- ing.The surface microhardness of the coating is 311 士10.2 HV, which is about 1.7 times that of 316 stainless steel matriX.The strengthening mechanism is solid solution strengthening and dislocation strengthening.The friction coefficient of the coat- ing is about 0.422, and the specific wear rate is 4.52× 10— 5 mm3/N.m,which is obviously better than 316stainless steel ma- triX.The wear mechanism is mainly abrasive wear,accompanied by slight adhesive wear.

The study investigates the application of a novel laser-resistant composite cladding wire material repair method for addressing column surface damage in mining hydraulic support systems.The effect of cladding speed (ranging from 30mm/s to 80mm/s) on the micro structure,hardness,and wear resistance of the cladding layer was systematically eXamined.Metallo- graphic and scanning electron microscopes were utilized to analyze the micro structure,while a microhardness tester was em- ployed to measure hardness across the cladding layer.Wear resistance was assessed using a reciprocating friction and wear tes - ting machine.EXperiments show that an increase in cladding speed results in a reduction of waviness at the cladding layer-sub- strate interface,stabilization of cladding layer thickness at 1 300 mm,decreased miXing between layers,and a transition in mi- cro structure from columnar to chaotic isometric crystal formations.Furthermore,hardness decreases as friction coefficient ini- tially rises and subseQuently declines.Notably,at a cladding speed of 80 mm/s,the highest friction and fatigue s palling were observed.

Laser cladding technology is an promising development direction of advanced manufacturing.With the rapid develop-ment of technology and industry,the Quality of the cladding layer is becoming more and more demanding.The characteristics ofthe melt pool,as an important test object in the laser cladding process,directly determine the Quality of the cladding layer.currently the eXtraction of melt pool profiles is based on traditional image segmentation,which does not perform well when en-countering melt pools with obscure features.Therefore,this work developed a molten pool morphology eXtraction method based on semantic segmentation network.The semantic segmentation network is used instead of traditional image segmenta-tion,combined with machine language to achieve high-precision eXtraction of melt pool shape and eXperimental verification to prove the feasibility of the method,laying a solid foundation for the subseQuent detection and analysis of the melt pool.

16 sets of parameter cladding eXperiments were conducted using orthogonal eXperiments.The hardness and friction characteristics of specimens with varying process parameters were eXamined using a microhardness tester and a friction wear in- strument.Additionally,the morphology and phase of cross- section joints were analyzed via scanning electron microscopy (SEM).The findings indicate that the powder delivery speed eXerts the most significant influence on the cladding layer I s hard- ness under the specified factors and levels.The microhardness of the optimal cladding sample is 182.9% higher than that of the substrate,resulting in an average friction factor reduction of 86.7% compared to the substrate.Moreover,there is evidence of good metallurgical bonding between the cladding layer and the substrate.

In this paper,a colorimetric pyrometer was used to determine the molten pool thermal history parameters in laser welding of 2205 dupleX stainless steel.The cooling rate of solidification under different welding speed was investigated.The effect of molten pool thermal history on the micro structure and microhardness of the joints was studied.The weld morphologies present a“nail”shape.With an increase in welding speed,the width,depth and section area of the joints were found to de- crease,while the cooling rate increases.As a result,the grains were refined obviously.Further,the grain morphology in the center of the weld evolves from eQuiaXed grains to columnar grains.The solid phase cooling rate increases with the welding speed,resulting in a decreasement of the precipitated phase.All the welds are hardened,and the average microhardness increa- ses with the welding speed.

To enhance the efficiency and capability of lithium foil detection based on the rolling process,a three-dimensional scanning and reconstruction techniQue based on wavelet analysis is proposed.This techniQue employs a laser displacement s en- sor combined with a scanning plate measurement method to achieve rapid and highly accurate data collection of the lithium foil I s shape characteristics.Building upon wavelet analysis,the laser rangefinder scanning measurement data,after removing gross errors,is subjected to wavelet coefficient threshold denoising,accomplishing noise reduction while preserving the integrity of the original measurement data.Finally,the shape is reconstructed using a point-by- point insertion method.Measurements of the same rolled piece using both the three- coordinate measurement method and the laser scanning plate reconstruction detection method proposed in this paper are compared.The results indicate a maXimum difference of 0.004 mm between the two meth- ods.utilizing the detection method proposed in this study,siX repeatability tests were conducted on the same rolled piece,showing a maXimum standard deviation of 0.001 47 mm and a repeatability error less than 士 0.003 mm.The research results validate that the laser scanning plate shape reconstruction detection method proposed in this paper has high precision and consis- tency,meeting the reQuirements for lithium foil detection.

To address challenges related to low registration accuracy and efficiency in multi-source point cloud data registration for buildings,an enhanced Trimmed Iterative Closest Point (TrICP) method incorporating principal component analysis (PCA) is introduced.Firstly,the PCA algorithm is used to calculate the principal aXis direction of the point clouds and create a correc- tion matriX based on the direction reversal problem,so as to obtain the initial good positional transformation of the two groups of point clouds and complete the coarse alignment step of the point clouds;then,the improved Trimmed Iterative Closest Point algorithm is used to complete the fine alignment of the two kinds of point clouds for the problems of searching point pairs and iteration number in Trimmed Iterative Closest Point.The eXperimental data show that the improved alignment algorithm signif- icantly reduces iteration counts,enhances alignment accuracy,preserves point cloud integrity,and boosts alignment efficiency.Comparative analysis shows accuracy improvements of 56.75%,39.6%,and 28.08% over three other algorithms,highlight- ing the effectiveness of the proposed approach.

Introducing laser scanning as a novel non-contact measurement technology known for its rapid speed and high preci- sion,commonly applied in surface damage detection.This paper presents an algorithm for detecting surface cracks on concrete prefabricated boX girders based on laser point cloud scanning.By analyzing height differences along scanning lines, the algo- rithm identifies crack locations and employs wavelet decomposition to enhance detection accuracy of mutation points.connect- ing these points across different scanning lines reveals the crack distribution.EXperimental results demonstrate the algorithm I s capability to accurately identify individual linear cracks on prefabricated boX girder surfaces, with optimal performance achieved using 4-layer wavelet decomposition with coif2 wavelet base for mutation point detection.

This study focuses on enhancing the sensitivity of a gas volume fraction sensor and mitigating fiber intermode inter- ference through the design of a double- channel edge hole structure.using COMSOL software,a gas volume fraction sensing model and loss spectrum are established to investigate the impact of varying structure parameters and fiber birefringence thick- ness.The results show that the sensor achieves high sensitivity,with 0.36nm/% for hydrogen and 2.89nm/% for methane,demonstrating eXcellent linearity.The photonic crystal fiber gas sensor eXhibits superior sensitivity,rapid response time,and the ability to detect multiple gases simultaneously.This research offers insights for developing sensitive films in real-life and in- dustrial applications,as well as single fiber sensors capable of detecting three or more gas volume fractions accurately.

To establish a rapid and precise identification and classification model for material evidence on note paper,44 note paper samples underwent Laser Confocal Micro-Raman (LCM-Raman) analysis.By integrating Principal Component Analysis (PCA),Hier- archical Cluster Analysis (HCA),and Linear Discriminant Analysis (LDA),the samples were identified and classified.Firstly,ac- cording to the different Raman spectrum characteristic peaks of inorganic fillers in the samples,the samples were Qualitatively analyzed and preliminarily divided into19categories.Secondly,for the sake of a more scientific and accurate classification,The principal compo- nent analysis was used to reduce the dimension of the Raman spectrum data of the samples,and the system clustering and linear dis- criminant analysis were used to determine that the best classification of the samples was 4 categories.The samples from the same place of origin had good aggregation,and the classification accuracy and cross validation classification accuracy were both 100%.Finally,The PCA-HCA-LDA classification model was used to predict the ungrouped sample of note paper.As concluded from the results,LCM-Ra- man combined with PCA-HCA-LDA classification model can distinguish note paper samples The generalization accuracy of the model is 100%,and the classification results are scientific and accurate.

This paper introduces a positioning method that utilizes volume kalman Filtering to integrate data from Lidar and visual camera sensors to address the challenges of Lidar robustness in long,straight environments and the impact of illumina- tion conditions on visual camera accuracy.At the same time,an adaptive component is added to the algorithm to improve the positioning accuracy of mobile robots in unknown environments.Firstly,the Lidar and vision are used to observe the sur- rounding objects at the same position simultaneously,and the current robot position information is obtained by using the graph optimization algorithm and pnp algorithm,and then the data collected by the Lidar and vision are continuously updated as the state and measurement values respectively to obtain the filtered fused localization results.The adaptive correction term is added through sage-Husa adaptive filtering theory to solve the problem of data divergence after long-distance observation.The simu- lation results show that the fusion positioning error is reduced by more than 25% compared with laser and vision in the form of an adaptive volume kalman Filter,which effectively improves the positioning accuracy of the mobile robot in the long-distance driving process.

The performance of their driving power will directly affect the output characteristics and service life of semiconductor lasers as a high-efficiency,high-stability opto electronic device.A constant current drive power supply with high efficiency,low ripple,and eXcellent anti-interference ability was created for semiconductor lasers in order to address the issues with stability and robustness of the output power.To begin,this paper proposes a method for designing LCC resonant cavity parameters to reduce component current stress.The freQuency conversion phase shifting compound control strategy and linear active disturb- ance rejection control algorithm are implemented using a mathematical model and eXperimental analysis.The power supply effi- ciency of the semiconductor laser is improved,the device I s current stress is reduced,the switch I s conduction loss is reduced,and it has better anti-interference ability,It has some implications for the design of high-performance semiconductor laser driv- ing power supply systems.In the end,according to simulation and eXperiment results,the power supply may be constantly ad- justed between an output current range of 0 to 40A, with a current ripple of less than 0.8% and a working efficiency of up to 92%.The system combines durability,cost-effectiveness,high efficiency,low ripple,and eXceptional stability.

To enhance the accuracy of Positioning,Navigation,and Timing (PNT) services in underwater environments,a no- vel optical high-precision bidirectional time comparison method is proposed.This paper elucidates the basic principle and system components of this method and describes the construction of an eXperimental system in a glass pool utilizing a laser diode,beam collimator,and mirror.The time comparison results eXhibit a peak-to- peak value of 1.6 ns,with an additional time transfer jit- ter of 1.05e — 11 s/s and 6.30e — 11 s/103 s.The eXperimental results verify the feasibility of the optical bidirectional time compari- son method in underwater space,and the nanosecond time comparison results show that it is valuable for further research.Mo- reover,a detailed analysis of eXperimental challenges provides a foundational understanding for future work and investigations in this area.

This study focuses on investigating the slit width of a single slit in Fraunhofer single slit diffraction.Initially,a theo- retical formula is derived to calculate the slit width based on the conditions for generating dark stripes in Fraunhofer diffraction.subseQuently,the eXperimental method for measuring the intensity distribution of single slit diffraction is outlined.Finally,the slit width is calculated using both traditional and programming methods,with the programming method demonstrating en- hanced accuracy.This research not only improves the calculation precision of the slit width but also provides valuable guidance for measuring the slit width of a single slit

In order to solve the problem that laser feedback has lock-in zone when measuring the phase delay of small birefrin- gent elements, the feedback effect of combined 1/4 wave plates in the feedback eXternal cavity of He-Ne laser is studied.By placing two 1/4 wave plates in the feedback eXternal cavity,rotating one of the wave plates, and changing the included angle between the fast and slow aXes of the two wave plates, polarization jump will occur.It is found that when the angle between the fast and slow aXes of the two wave plates changes, the polarization jump phenomenon always eXists and the position of the jump point changes, that is, the phase delay of the combined wave plate can change continuously.When the included angle be- tween the fast and slow aXes of the two wave plates varies from 0。to90。, the eQuivalent phase delay of the combined wave plate can be changed from 19.79。to 160.06。through five repeated eXperiments, and the maXimum difference of repeated measure- ments is 0.6。, and the maXimum standard deviation is 0.25。.The combined wave plate can be applied to the measurement of micro birefringent elements in laser feedback measurement.As a bias element,it modulates the phase delay of the measurement system that needs to be compensated.

This study systematically evaluates the clinical efficacy of diode laser as an adjuvant treatment for peri-im- plant diseases.Methods : A comprehensive search of literature on diode laser treatment for peri-implant diseases was conducted across various databases.Meta- analysis was carried out using RevMan 5.4 software after independent reviewers screened the literature,assessed study Quality,eXtracted data,and evaluated bias risk in the included studies.Results : 8 papers were finally screened and included.The meta- analysis showed that compared with the mechanical debridement group,probing depth(PD) [MD= —0.28, 95%CI : (—0.46, —0.10),P= 0.002],plaQue indeX(PI)[MD= —0.13, 95%CI : ( — 0.21, — 0.05),P= 0.002],bleeding indeX(BI)[MD=-0.42, 95%CI : (—0.83, —0.01),P= 0.05],and bleeeding on probing(BOP)[MD= — 1.81, 95%CI : (—2.53, — 1.08),P0.05).Conclusion : The current evidence suggests that diode laser-as - sis ted treatment for peri-implant diseases shows effectiveness only in the short term,with significant improvements observed after 3 months of treatment.