In view of the shortage of hardness and red hardness of high speed steel tool in high-speed cutting and high-hard material cutting, WC/Co coatings is fabricated on the surface of high speed steel turning tool by using laser cladding technology to improve tool performance. The influence of different pre-processing morphology on the cladding layer is studied, the method to solve the problem of the inconsistency of the turning edge angle in the process of cladding is put forward, and the actual cutting performance of the coated tool is verified. The results show that the pre-laid groove cladding is a reasonable pre-processing morphology, the micro-hardness of the cladding layer is 57% higher than of the turning tool substrate, at 600 ℃ the red hardness of the cladding layer is 0.25 times higher than that of the turning tool substrate, and at 1 000 ℃ the red hardness reaches more than 50HRC. the design of special cladding flip fixture can effectively adjust the angle of tool edge angle. The cladding turning tool shows excellent practical performance in high-hard material cutting and high-speed cutting.

At present, laser cladding forming techniques are generally difficult to realize the formation of an unsupported capping structure. Using the intra-powder powder feeding technology and the oblique stratification method, the lap joint cap forming across multiple straight walls was studied, and the spatial oblique bridging stacking was realized. The distribution of annular laser energy under different oblique angle projections of light-fed powder-fed nozzles was discussed. The influence of tilt deflection angle on the appearance of cladding was investigated. The layer height measurement and control technology is introduced to detect and control the height of the cladding layer in real time to ensure that the stacking morphology is not unstable. The results of the structure inspection of the bridging cap forming structure show that the surface of the space cover overlap is flat, the wall thickness is uniform, and the hardness is generally stable.

In order to improve the comprehensive quality of the laser cladding layer of the remanufactured workpiece, the laser power, the powder feeding amount and the scanning speed are selected as the optimization variables, and the aspect ratio, dilution rate and powder collection rate of the cladding layer are selected as optimization targets, based on the comprehensive weighting method. The analytic hierarchy process is used to transform the three optimization objectives into comprehensive quality objectives, design the whole factor experiment, and use the MATLAB software to establish the BP neural network prediction model based on the experimental results, and determine the combination of the best process parameters by genetic algorithm. The optimal process parameters for re-manufacturing laser cladding of equipment parts are: laser power is 3.0 kW, powder feeding is 47 g/min, and scanning speed is 5.5 mm/s.

In order to obtainhigh-precision, high-gloss and high-quality conformal cooling channels die, achieve good cooling effect.The HANS M160 selective laser melting equipmentwas used to test 1.270 9 die steel powder. On the premise of guaranteeing the quality of the formed parts, the surface roughness of the conformal cooling channels was improved. The influence of repeated scanning times and scanning bias on the forming quality was investigated by single factor test method, and the influence of laser profile parameters on the forming quality was compared. The results show that when the laser power is 150 W, the scanning speed is 1 150 mm/s, the scanning distance is 50 μm, the thickness of powder layer is 30 μm, the number of contour scanning is 1, and the scanning bias is 0 mm, the input energy density is 86.96%. The best result is that the hardness is 367 HV0.1, the side roughness is 5.69 μm, and the density is 98.61%. The experimental results show that the forming quality of the parts can be improved by adding laser profile parameters.

In this paper, the high-speed rotor shaft of the air compressor is repaired by laser cladding and machining. A series of measures to suppress substrate temperature rising are taken during the cladding process. Multiple sets of single-pass and multi-pass lap welding experiments were carried out and tested under the conditions of different laser power and cladding lap ratio, with the scanning speed, powder feeding speed and protecting gas flow rate controlled. The test results show that the cladding effect is optimal with laser power 600w and lap ratio 27.5%. The hardness of the cladding layer is HRC53-56, which is metallurgical bonding with the substrate. The substrate temperature during the cladding process is always maintained below 100 ℃. The cladding layer which is stained by colored penetrant after the repair hasno defects such as cracks and pores. The installation operation requirements are met after the dynamic balance detection and adjustment.

Laser additive manufacturing technology has been applied in many fields, but due to the lack of corresponding monitoring and diagnosis of the manufacturing process, it hinders the development and application of this technology in the highly sophisticated field where the quality of products is strictly required. In this paper, the laser induced plasma method is used to monitor the composition of Cr in the laser additive manufacturing process. Firstly, the spectral data is collected by experiment. Secondly, the spectral characteristics affecting the Cr concentration are found. Finally, the Cr concentration monitoring model is established according to the relevant spectral characteristics. The model used in this paper is the support vector machine model. The experimental results show that the model can accurately predict the Cr concentration in the laser additive manufacturing process. When the Cr concentration is 11.9%, the absolute error of calibration of the whole process is 0.67%, the relative error of calibration is 5.04%, and the relative standard error is 4.23%. When the model was applied to component monitoring, it was found that the predicted value fluctuated around the actual Cr concentration value with a small amplitude.

The inherent problems associated with laser cladding remanufacturing process using NiCrBSi alloy powder is the formation of crack. Ni60A alloy coatings manufactured by laser hybrid process parameters cladding on 45 steel were investigated. A considerable amount of network eutectics locate in a large number of intergranular positions of the primary matrix under SEM (Scanning Electron Microscope).The results of EDS (Energy Dispersive Spectroscopy) and XRD (X-Ray Diffractometer) find that the coating has homogenous and fine microstructure consisting of γ (Ni) solid solution, a considerable amount of network Ni3B, M23C6 (M=Fe, Ni, Cr) and M7C3 eutectics, with boride ceramic phase CrB uniformly distributing in interdendritic eutectics. With the decreasing of molten pool cooling rate, the intergranular eutectic hard phase (M23C6, M7C3) decreases, and the tough phase γ (Ni) increases, meanwhile, the metal compound FeNi3 is formed during the cladding process, thereby the toughness of the cladding layer is enhanced. The crack is eliminated when preheating temperature is up to 300 ℃.

The research on forming of arched structure, especially with closed feature, is of great significance in the field of 3D printing of metal parts. In this paper, an overhanging arched structure was formed by slant forming method with hollow laser beam inside power feeding. The overhang deposition method was proposed to eliminate the defects of the closed part that were the raised top and the recessed downside. The influence of slant angle, loading time, loading power and other parameters on the vertical fluidity of molten pool was analyzed, and the theoretical model of the vertical displacement of molten pool was established. The arched closed structure was successfully obtained by means of the technology of slant laser cladding forming with coaxial inside-beam powder feeding and the overhanging deposition method of molten pool. The test results show that the defects of the closed part that were the raised top and the recessed downside has been eliminated successfully by layered filling with variable angles and parameters and the minimum wall thickness of the closed part was 3.2mm that have met the requirements of design size.

Aiming at the problem that the common fastener anti-corrosion process cannot meet the actual anti-corrosion requirements, this paper proposes a new idea to improve fastener anti-corrosion based on laser cladding technology and the results have been verified by experiment. Ten laser cladding parameters were used to prepare the C22 cladding layer of Hastelloy alloy on chromium-plated and non-chromium-plated 45 steel bars to study the microscopic appearance, dilution rate, microhardness and polarization curve of the cladding layer. The results show that the cladding layer has a good bonding with the matrix, without obvious cracks. The dilution rate of the cladding layer can be effectively reduced by first plating chromium on the surface of the substrate and then laser cladding. The microhardness of the cladding layer’s surface can reach 320 HV0.5, 200 HV0.5 higher than that of the matrix. Since the cladding layer has a higher self-corrosion potential (Ecorr= -0.265 V) and a lower self-corrosion current density (Icorr=4.784×10-7 A/cm-2 ), the base metal can be efficiently protected. Therefore, a conclusion can be drawn that it is feasible to apply laser cladding technology to anti-corrosion of fasteners.

In order to meet the special needs of the environment for the different parts of the same component in the aerospace industry, gradient structural materials have gradually attracted widespread attention from scholars at home and abroad. In this paper, the TA15-Ti2AlNb gradient structure material was prepared by laser solid forming. The microstructure evolution and microhardness of TA15-Ti2AlNb dual alloy materials were studied. The results show that with the increase of Al and Nb content, the transformation of the laser solid formed TA15-Ti2AlNb dual alloy from the TA15 alloy side to the Ti2AlNb-based alloy side phase is α and β phase, α, α2 and β/B2 phases , α2 and β/B2 phases, α2, β/B2 and O phases, and α2 and B2+O phases. And the grain morphology gradually changes from epitaxially grown columnar crystals to isotropic crystals of isotropic growth, and a significant CET transition occurs. The diffusion of elements caused by thermal effect during the deposited process is the main factor for the distribution of elements in the final dilution zone, which ultimately leads to a significant change in the microstructure and phase composition of the deposited samples.

CNTs-SiC-Ni composite cladding coating were fabricated by laser cladding with mechanical alloying modified composite powders. The effects of mechanical alloying on the microhardness and antiwear properties of composite cladding were studied. The results show that with the increasing mechanical alloying speed, the encapulsated area on the nickel particle grows at the exponential rate and keeps constant on the 350r/min mechanical alloying, the nickel powder, SiC particle and CNTs mix evenly. When the mechanical alloying speed is 300r/min, the fine core-shell (CNTs-SiC)/Ni composite particle is obtained, the microhardness of the cladding gets the peak value, the mass wear of the cladding has the minimium value.

Selective laser sintered graphite part have low relative density, and its thermal conductivity is relatively low. In this paper, porous graphite preforms with densities ranging from 18.78% to 24.95% were prepared by selective laser sintering process with varied process parameters. Effective thermal conductivity of the preforms at room temperature was measured by transient plate heat source method. The effect of laser energy density between 0.05 and 1.5 J/mm2 on the thermal conductivity of the preforms was studied.Results showed that there was a positive correlation between laser energy density and thermal conductivity, and the relative density of preform increased with the increment of energy density when the energy density was less than 1.367 J/mm2, while the relative density of preform remained unchanged when the energy density is greater than 1.367 J/mm2. By introducing correlation coefficient between energy density and thermal conductivity, based on the thermal conductivity data of preforms prepared under different energy densities, a theoretical model of thermal conductivity related to laser energy density and thermal conductivity of porous graphite preforms was established, and the validity of the thermal conductivity model was verified by experiments. Results showed that the deviation between the predicted value of the heat conduction model and the measured value of porous SLS graphite preform is less than 1.5%.

Transparent conductive oxides are widely used in photovoltaic devices and flat panel displays. The knowledge of the dielectric function is essential for the application of transparent conducting oxide thin films. The La2/3Sr1/3VO3 (LSVO) thin film was successfully prepared on (LaAlO3)0.3(Sr2AlTaO6)0.35(LSAT) substrate by pulsed laser deposition. The optical properties of the LSVO thin film was measured by spectroscopic ellipsometry. The dielectric function of the LSVO thin film is described by B-spline model and Lorentz+Tauc-Lorentz dispersion model, respectively. The results showed that there are two significant optical transitions located at 3.41 eV and 4.11 eV in the visible region. The red shift of the optical bandgap in the doped LSVO thin film, which is located at 3.41 eV, is about 0.19 eV. The transition (positioned at 4.11 eV) in the high energy region is attribute to the charge transfer excitation involved in O 2p orbital and the upper unoccupied V 4 s orbital.

The quasi continuous wave laser of 150 watt was used to weld stainless steel with 0.2 mm thickness. Through orthogonal experiment of laser welding process parameters, the tensile strength and sealed of welds met the requires. Tensile strength testing, inner structures analysis, hardness test were carried on the welded joint. The test results show that the main parameters on tensile strength are pulse width, followed by peak laser power. The maximal tensile strength reached 434 MPa. No pores and crack appeared in welds, microhardness was HV 254-256, which was bigger than the base metal. The sensor shells were welded and sealed character was tested, the test result showed that the sealed welds met the requires of 5 atmospheres.

Aluminum powder can be used as a laser welding absorbent because of its good thermal physical properties, but the high reflectivity of aluminum needs to be incorporated into carbon black to enhance the absorption performance of the absorbent. In this paper, the laser transmission welding experiment of polycarbonate with aluminum powder absorption layer was carried out by using semiconductor laser. The main factors of different aluminum powder content of absorbent were combined. The welding process parameters were welded by orthogonal level method in combination with laser power and welding speed. The influence of the strength was optimized for the welding process parameters. The optimum process parameters were obtained, and the effects of different aluminum powder content absorbents on the weld morphology and joint strength were analyzed. The experimental results show that the aluminum powder content of the absorbent is 40 wt%, the welding power is 35 W, and the welding speed is 4 mm/s, the breaking force is the largest and the welding strength is the highest.

In order to solve the problem of connection molding between dissimilar materials in aircraft rudder wing components, the laser welding tests was carried out on 3 mm thick GH4169 and 20Cr13 under different welding parameters. X-ray inspection, microstructure observation and tensile test of normal temperature and high temperature were performed on the welds, and the results showed that: when the defocus is +2 mm, the welds with less internal porosity defects can be obtained; when the line energy is less than 100 J/mm, it is beneficial to avoid the occurrence of microscopic hot cracks; when the laser power is 2.2 kW, the welding speed is 30 mm / s and the defocus is +2 mm, the weld with the highest tensile strength at normal temperature can be obtained, moreover, in the larger parameter range, welds with tensile strength of 400 ℃ and 600 ℃ better than 20Cr13 base metals can be obtained.

The droplet transfer behavior and welding stability of 10Ni3CrMoV steel plate with 14mm thickness under single MIG and laser-MIG combined welding were compared and analyzed, and the profile morphology of welded joint was observed. The results show that under the action of low current and high current, the shape of weld profile is semi-circular at the upper end and triangular at the lower end, while the shape of laser-MIG composite weld profile is Y-shaped; there are no defects such as porosity, slag inclusion, cracks, incomplete penetration and incomplete fusion in the welded joint under the same laser-arc spacing. The penetration depth and penetration width under the action of large laser power, small current and large laser power are larger than those under the action of small laser power and small current. Moreover, the penetration depth and penetration width under the action of large laser power, small current and large laser power and large current do not show a linear change with the change of laser-arc spacing. And the influence of melting width is obviously lower than that of large laser power. Under the condition of laser-MIG hybrid welding, the suitable spacing between laser and arc is 1.5~4.5 mm, 3~4.5 mm and 1.5~3 mm respectively under the action of high laser power and small current (11 KW, 260 A), high laser power and large current (11 KW, 420 A) and low laser power and small current (7 KW, 260 A). In this range, the welding process is stable without droplet flying sputtering phenomenon, droplet transition form is a single jet transition.

An online laser-welding monitoring system is performed to monitor the gap of overlap joint in fiber laser welding steel sheet. The results indicated that the gap of overlap joint have a huge impact on welding appearance but nothing to do with welding penetration. Amplitude of optical signal in time domain and frequency distribution in time-frequency domain has a significant change when the defect occurs in the laser welding process. Optical signals are analyzed using signal processing methodologies to reveal intrinsic interaction between optical signals and the gap, it also provide theoretical basis and experimental guidance for analyzing the dynamic behavior of plasma and pool.

Fiber laser brazing diamond grains to substrate using Ni-Cr filler alloy was carried out in an argon atmosphere. The effects of laser power and welding speed on the weld appearance were analyzed. The microstructure and compound of Ni-Cr filler alloy and diamond grains brazed interface were studied. The results show that the laser power and welding speed have a significant effect on the degree of melting of Ni-Cr filler alloy and the thermal damage of diamond. Lower laser power and welding speed made a poor weld appearance of the brazed joint. A good weld appearance was obtained when the laser power and the welding speed were larger, however, the Ni-Cr filler alloy at the bottom of the diamond grains was insufficiently melted, resulting in fall off of the diamond. When the range of the laser power was 700 W~760 W, the welding speed was 0.7 mm/s~1.5 mm/s, and the defocus value was +18 mm, the brazed joints with good weld appearance and high bonding strength were obtained. There was a thin bonding interface between the Ni-Cr filler alloy and the diamond grains, with thickness of ~4 μm. There were slice-like and acicular products on the surface of the brazed diamond grains. The result of XRD analysis indicated that the compound on the brazed diamond grains was Cr3C2.

The parameter θ of parameter space was classified as different resolutions and the θ axis of parameter space was refined to required precision by iteration method. Two different Hough transformations shall be operated: Low-resolution Globe Hough Transformation and High-resolution Regional Hough Transformation. Under different of parameter θ (△θ0) value: 2°, 3°, 4°, 5°, 7.5°, 9° and 10°, analysis results of Multi-resolution Hough Transformation (MHT) Analysis of Welding Image resolution were researched and compared with Standard Hough Transformation (SHT). It demonstrates that the results of MHT coincide with SHT, moreover, the memory requirements decrease and calculating speed increases three times when the value of △θ0 is 6°.

To refine the coarse primary carbides in the high carbon and high chromium alloy hardfacing layer and improve the wear resistance of the surfacing layer. D632A welding rods were selected for hardfacing on Q235 steel plates, and the laser-arc hybrid hardfacing sample and the arc hardfacing sample were compared. Microhardness test and friction and wear test were taken to value the hardness and wear resistance. Their microstructure of the hardfacing layer before wear was observed by Optical microscopy (OM) and their morphologies were studied by SEM. The reasons for the difference in friction and wear properties between laser-arc hybrid hardfacing samples and arc hardfacing samples. Under the action of laser-arc hybrid heat source, the M7C3 primary carbides in the hardfacing layer are refined into fine granular from coarse strip. Theses granular carbides were evenly distributed. Compared with arc hardfacing layer, the average microhardness of the laser-arc hybrid hardfacing layer was increased by about 12.5%, and the maximum microhardness was 1064 HV. The wear resistance of the laser-arc hybrid hardfacing layer was better. The wear quality was 5 mg and the friction coefficient was 0.38 under the same conditions. The wear resistance of the arc hardfacing layer was poor. The wear quality was 7 mg and the friction coefficient was 0.43 under the same conditions. The mainly wear failure mechanism of the two hardfacing layer was fatigue failure. Laser-arc hybrid hardfacing can effectively improve the hardness and wear resistance of the high carbon and high chromium alloy hardfacing layer by refining the primary carbide in the hardfacing layer.

Taking the cooling rate as the cut-in point, the effects of cooling rates, power densities and interaction time on the hardened layer of ductile cast iron were studied in the process of laser heat treatment. Through theoretical calculations, different cooling rate distributions were obtained by using different power densities and interaction times, and laser surface heat treatment was performed on QT600-3 ductile iron. After laser heat treatment , it is found that the surface temperature of each group of parameters is 1 500~2 500 ℃, and the actual cooling rate is about 6% compared with the theoretical calculation above. The melting zone can occur in each group of hardened layers, but the depth, hardness and grain distribution are different. The depth variation of each group is 0.5~0.8 mm, the micro hardness varies from 800 to 1100 HV0.1, and the grains are coarse to fine. The microstructure and hardness of the fused zone are most affected by the cooling rate. Due to the large distance from the surface in other regions, the cooling rates of each group are greatly tend to be consistent, so the hardness change is not obvious.The depth of the hardened layer is proportional to the cooling rate, and gradually increases with the increase of the cooling rate. Under the premise of ensuring the same laser energy density, the power density has a greater influence on the depth than the interaction time.

The existing laser Raman gas detection (LRGD) system is affected by system noise, and the detection accuracy of low concentration gas is poor. In order to improve the detection accuracy of the LRGD system for low concentration gas, a laser Raman gas detection method based on multi-signal superposition and pseudo inverse method (MSSPI) is proposed. Specifically, for low concentration gas, the ability of resisting system noise is enhanced by Raman signal superposition. The signal detection module is used to detect the superimposed Raman signal. The Raman signal of the single gas is reconstructed by the pseudo-inverse method, then the gas concentration is calculated by the corresponding formula. The experimental results show that the LRGD system with the MSSPI method improves detection accuracy of the low concentration gas. The MSSPI method does not change the existing LRGD system, the calculation is simple and efficient, which reduces the detection error to a certain extent. The proposed method can be used as an auxiliary method for gas detection.

The purpose of this paper is to investigate the detection method of composite laminates by using digital shear speckle interferometry, and to establish an experimental and simulation system to verify the test results. The effectiveness of the detection method is verified by comparing to the X-ray inspection technology and ultrasonic C-scan test results. The effectiveness of the proposed method is verified by analyzing the testing results of different curvature laminates. In addition, the concept of relative deformation phase threshold is proposed as a criterion for judging whether a defect can be successfully detected. According to this standard, the defect detection capability under different temperature loading conditions can be inferred, therefore to guide the actual loading parameters of the digital shear speckle technique.

The temperature fluctuation of the laser will cause the change of its output characteristics. In order to achieve the accurate measurement of the detection system, it is necessary to explore the influence of temperature change on the output characteristics. In this paper, the effects of different temperature gradients on the internal parameters of the laser under transient conditions are studied, including the photon density, carrier density, threshold current, photoelectric delay, relaxation phenomenon and output power characteristics.Simulink is used in experimental simulation to build a simulation model. Starting from the rate equation, the gain coefficient related to temperature change and the influence of transparent carrier are introduced to obtain the parameter change under temperature change. The experimental results show that the temperature change has a great impact on the internal performance of the laser, which will weaken the detection accuracy. In order to reduce the error caused by the temperature change, the corresponding temperature control circuit should be used.

The energy utilization rate of excimer lasers has become an important factor restricting its further development in the processing field. In order to solve this problem, this paper carried out research and design of a new type of tapered optical element for excimer laser convergence. Through the extraction and simulation of the outer contour of the taper quartz tube, combined with the variation of the melting zone during the taper process, the curve function of the taper region is obtained, which is corrected and compared with the outer contour data of a large number of taper quartz glass tubes. Get the taper shape function. Based on the shape function to simulate the actual shape of the component, the actual loss and spot shape of the beam are simulated by the tracking of the beam and the calculation of the loss. Finally, a taper optical element is fabricated based on the function curve of the simulation result. After the excimer laser passes through the optical system, a circular spot with an inner ring diameter of 100 μm can be obtained at the light exiting port, and the utilization rate of light energy is about 80%, which solves the problem that the excimer laser spot shape is irregular and the energy distribution is uneven.

This paper introduces the design of optics, constant current source system and protective circuit and constant temperature control unit of a high-power semiconductor laser therapeutic equipment. It uses a fiber coupled 980 nm with maximum power output of 10 W as effective light source, 635 nm semiconductor laser as aiming beam. The functions such as operation mode, output power, pulse width and pulse cycle could be easily set through the LCD touch screen. It has a very good prospect of application in cosmetic dermatology.

In order to improve the accuracy of liquid flow measurement of the open channel,therefore, more accurate flow measurement equipment is needed for industrial and mining enterprises. Based on the analysis of the principle of open channel flow, the design scheme based on DSP28335 is proposed. The flow measurement method of open channel weir is described. The main control chip DSP28335 sends ranging commands to dls-a15 using RS232C serial communication, DLS-A15 receives the ranging command and sends a laser signal to the liquid Surface to be tested. The laser signal reflected back from the liquid level is received by the sensor and converted into a sequence of data information code. It is then returned to the main control chip DSP28335 to receive by RS232C serial communication. The correct data received is the distance from the laser ranging sensor to the liquid level. Experiments show that the device has the characteristics of high measurement accuracy, reliable operation and low price, and provides a reference for online automatic detection of liquid level in the industrial field. The experiment shows that the device has the characteristics of accurate measurement, reliable operation and low price, which provides a reference for online automatic detection of sewage discharge in industrial and mining enterprises.

Objective: to assess the efficacy and safety of tranexamic acid cataplasm combined with large spot low energy Q switch Nd :YAG laser for melasma. Methods: Selected 180 patients with facial melasma as the research object, according to different treatment methods, the included patients were divided into group A and group B, with 90 cases each. Group A was treated by large spot low energy Q switch Nd :YAG laser, and Group B was treated by tranexamic acid cataplasm combined with large spot low energy Q switch Nd :YAG laser. The total melasma score decline index, total effective rate, dermatology life quality index (DLQI), melasma quality of life scale(MELASQOL) and adverse reactions of chloasma were observed and compared between the two groups after treatment. The patients in the two groups were followed up for 6 months to observe and compare the recurrence of patients in the two groups. Results: ①There was no statistically significant difference in total chloasma score before treatment (P>0.05)between the two groups, and decreased after treatment (P0.05), and DLQI and MELASQOL scores were significantly reduced after treatment in the two groups (P0.05).During the 6-month follow-up, the recurrence rate of group B (5.6%) was lower than that of group A (11.1%), and the difference was statistically significant (P<0.05). Conclusion The efficacy of tranexamic acid cataplasm combined with large spot low energy Q switch Nd :YAG laser for melasma is significant, has high patient satisfaction, low recurrence rate and mild adverse reactions, which is worthy of clinical application.

Objective: To discuss the predictive effect of CT value of renal calculi on exible ureteroscopy with holmium laser lithotripsy. Methods: 133 cases of patients with single renal calculi performed by flexible ureteroscopy with holmium laser lithotripsy in our hospital were analyzed retrospectively, according to the measured mean CT value of calculus, the patients were divided into low-value group (CT value0.05). The calculi clearance rates of low-value group and high-value group were 92.86% and 76.19%, respectively. The difference between the two groups was statistically significant (P<0.05).The operative time was (83.23±12.71) min and (119.40±16.35) min, respectively. The difference between the two groups was statistically significant (P<0.05).The incidence of surgical complications was 4.29% and 17.46%, respectively, with statistically significant differences between the two groups (P<0.05).Logistic multivariate regression analysis showed that CT value and operation time of calculus were independent risk factors affecting calculi clearance rate. Conclusion: CT value of calculi has certain predictive value for lithotripsy time, calculi clearance rate of flexible ureteroscopy with holmium laser lithotripsy.

Object: To investigate the effect of photodynamic therapy with TBO as photosensitizer on inhibition of cariogenic bacteria in rat biofilm.Method：A model of dental plaque biofilm was established by using streptococcus mutans, streptococcus haematococcus, lactobacillus acidophilus and actinomyces glutinous as experimental strains. The experiment was divided into five groups. Forty rats were randomly divided into five groups. There were 8 rats in each group. Group A was the negative treatment group treated with normal saline; Group B was the positive control group treated chlorhexidine; Group C was treated with laser radiation only. The parameter was a wavelength of 630 nm, an output intensity of 105mW/cm2, irradiation time of 9 min; Group D was treated with photosensitizer only whose concentration was 100mg/L and incubated in dark for 5min; Group E was named TBO-PDT group. TBO-PDT group was treated with 100 mg/L TBO , incubated in dark for 5min and irradiated with diode laser which parameter was wavelength 630nm and output intensity 105mw/cm2.The oral cavity of each rat was divided into 4 regions. The last two molars in each area were selected as experimental objects. 8 sample teeth were selected for each rat.The activity of dental plaque biofilm was observed by plate colony counting experiment. The effect of PDT on oral soft tissue was observed by histopathological section. Scanning electron microscopy was used to observe the changes of tooth surface morphology before and after PDT treatment.Result: Compared with Group A and Group B, the number (CFU/mL) of viable caries causing bacteria in the dental plaque of Group E was significantly reduced (P<0.05). The bacteriostasis rate was 87.02%. Group C and Group D have no obvious bacteriostatic effect. Scanning electron microscopy showed that the molars of TBO-PDT group had smooth surface and superficial demineralization pore. Pathological section showed no obvious periodontal tissue damage in TBO-PDT group.Conclusion: The experimental results showed that photodynamic therapy had obvious anti-caries effects and had no obvious damage to the dental hard tissue and periodontal tissue.