Cutting Experiment of Fraxinus mandshurica UsingWaterjet-Assisted CO_(2)Laser

High-quality wood products and valuable wood crafts receive everyone’s favor with the rapid development of the economy.In order to improve the cutting surface quality of wood forming parts,the cutting experiment of renewable Fraxinus mandshurica was conducted by waterjet-assisted CO_(2)laser(WACL)technology.A quadratic mathematical model for describing the relationship between surface roughness changes and cutting parameters was established.The effects of cutting speed,flow pressure and laser power on the kerf surface roughness of Fraxinus mandshurica when cutting transversally were discussed by response surface method.The experimental results showed that kerf surface roughness decreased under a lower laser power,higher cutting speed and higher flow pressure.When the cutting speed was 30 mm/s,flow pressure was 1.58 MPa and laser power was 45 W,the actual surface roughness of the optimized Fraxinus mandshurica was 2.41μm,and it was in accord with the theoretically predicted surface roughness value of 2.54μm,so the model fitted the actual situation well.Through the analysis of 3D profile morphology and micromorphology,it was concluded that the optimized kerf surface of Fraxinus mandshurica was smoother,the cell wall was not destroyed and the tracheid was clear.It provides the theoretical basis for wood micromachining.

The Characteristics of Glued Tensile Shear Strength Constituted of Wood Cut by CO_(2) Laser

The performance of engineered wood products is highly associated with proper bonding and an efficient cutting method.This paper investigates the influence of CO_(2) laser cutting on the wetting properties,the modified che-mical component of the laser-cut surface,and the strength and adhesive penetration near the bondline.Beech-wood is cut by the laser with varying processing parameters,cutting speeds,gas pressures,and focal point positions.The laser-cut samples were divided into two groups,sanded and non-sanded samples.Polyvinyl acetate adhesive(PVAc)was used to bond the groups of laser-cut samples.After assembly with cold pressing,the tensile shear test was carried out.Numerical modelling was carried out to determine the partial elongation and shear strain of the glue line.Based on this,the shear modulus and linear elasticity of the glue line were estimated.Scan-ning electron microscopy was used to assess the adhesive penetration into the porosity structure of the laser-cut samples,and the depth of the heat-affected zone.The laser-cut surface was analysed by Fourier transform infrared spectroscopy.The wetting properties of the laser-cut surface were investigated by using a contact angle goni-ometer.The numerical model of the strain-stress curve confirmed the experimental model.The highest modulus of the linear elasticity of the glue in the numerical calculation belongs to the joint containing laser-cut samples at a gas pressure of 21(bar).The penetration depth of PVAc adhesive into the porosity structure of the laser-cut sam-ples was similar to that of sawn samples.The deepest heat-affected zone in the laser-cut samples was 150µm.A PVAc drop disappeared immediately on the laser-cut surface without sanding,but gradually on the sanded surface.In contrast,the drop on the sawn surface remained with an angle of 32°–48°.The degradation of hemi-cellulose and lignin was proven by the lower intensity of the C=O and C-O Bonds,compared to the sawn surface.

Diagnostics of laser-induced plasma on carbon-based polymer material using atomic and molecular emission spectra

Time-integrated optical emission analysis of laser-induced plasma on Teflon is presented.Plasma was induced under atmospheric pressure air using transversely excited atmospheric CO_(2) laser pulses.Teflon is a C-based polymer that is,among other things,interesting as a substrate for laser-induced breakdown spectroscopy analysis of liquid samples.This study aimed to determine the optimal experimental conditions for obtaining neutral and ionized C spectral lines and C2 and CN molecular band emission suitable for spectrochemical purposes.Evaluation of plasma parameters was done using several spectroscopic techniques.Stark profiles of appropriate C ionic lines were used to determine electron number density.The ratio of the integral intensity of ionic-to-atomic C spectral lines was used to determine the ionization temperature.A spectral emission of C2 Swan and CN violet bands system was used to determine the temperature of the colder,peripheral parts of plasma.We critically analyzed the use of molecular emission bands as a tool for plasma diagnostics and suggested methods for possible improvements.

Effect of laser characteristics on the weld shape and properties of penetration laser weld of BT20 titanium alloy

The laser beam welding of BT20 titanium alloy was conducted to investigate the weld shape, microstructures and properties. The full penetration weld characteristics produced by CO_2 laser and by YAG laser were compared. The results show that the full penetration weld of YAG laser welding closes to “X” shape, and weld of CO_2 laser welding is “nail-head” shape. Those result from special heating mode of laser deep penetration welding. The tension strength of CO_2 laser and YAG laser joints equal to that of the base metal, but the former has better ductility. All welds consist mainly of the acicular α phase and a few β phase in microstructure. The dendritic crystal of CO_2 laser weld is a little finer than YAG laser weld. According the research CO_2 laser is better than YAG laser for welding of BT20 titanium alloy.

Influence of secondary treatment with CO_2 laser irradiation for mitigation site on fused silica surface

The ablation debris and raised rim, as well as residual stress and deep crater will be formed during the mitigation of damage site with a CO2 laser irradiation on fused silica surface, which greatly affects the laser damage resistance of optics. In this study, the experimental study combined with numerical simulation is utilized to investigate the effect of the secondary treatment on a mitigated site by CO2laser irradiation. The results indicate that the ablation debris and the raised rim can be completely eliminated and the depth of crater can be reduced. Notable results show that the residual stress of the mitigation site after treatment will reduce two-thirds of the original stress. Finally, the elimination and the controlling mechanism of secondary treatment on the debris and raised rim, as well as the reasons for changing the profile and stress are analyzed. The results can provide a reference for the optimization treatment of mitigation sites by CO2laser secondary treatment.

A Case of Refractory Childhood Glaucoma Secondary to Weill-Marchesani Syndrome:Management with Combined CO_(2) Laser-Assisted Sclerectomy Surgery and Trabeculectomy

A 2-year-old girl was diagnosed as Weill-Marchesani syndrome with typical systemic features of short stature,short and stubby hands and feet,language disorders and mental retardation.He developed bilateral angle closure glaucoma,ectopia lentis and suffered visual loss from the ocular features of Weill-Marchesani syndrome.The child was successfully treated by combined CO_(2) laser-assisted sclerectomy surgery and trabeculectomy.

STUDY ON Na_2O-GeO_2-SiO_2-PbO GLASSES USED AS THE CLADDING MATERIALS OF HOLLOW WAVEGUIDES FOR TRANSMITTING CO_2 LASER

In this paper a new kind of mid - infrared fiber material is reported. The reflective coefficients (R) of glasses in the system Na2O - ZnO - GeO2-SiO2-PbO have been measured-the refractive index becomes less than unity at 1180 - 900cm-1 range because of the existence of anomalous dispersion. The optical losses of hollow waveguides were calculated,the predicted losses at 940cm-1are 0. 65 and 0. 081B/ m as the inner diameter of fiber is 0. 5 and 1. 0mm respectively. The glasses can be used as the cladding materials of hol-low waveguides for transmitting CO2 laser from the measurements of characteristic temperatures, coefficient of expansion and chemical durability.

Combined Treatment with Electrocauterization,Carbon Dioxide Laser,and Microneedle Fractional Radiofrequency for Facial Angiofibromas in Tuberous Sclerosis Complex:A Case Report and Literature Review

Tuberous sclerosis complex is a type of genetic multisystem disease that causes hamartomas in various organs.Facial angiofibromas commonly occur in 80%of patients and are prominently distributed over the cheek,chin,and nasolabial folds with severe disfigurement and emotional distress.Recently,photoelectric devices have been identified for the treatment of angiofibromas with great efficacy and fewer side effects.We report a case of a 42-year-old man with facial angiofibromas,who was treated with a combination of high-frequency electrocauterization,Ultrapulse CO_(2) laser,and microneedle fractional radiofrequency with 7 sessions and a 6-month follow-up.The patient showed great improvement in relation to the elevated lesions and nodules.A low recurrence rate was observed.This is the first study to investigate the efficacy of high-frequency electrocauterization and microneedle fractional radiofrequency in angiofibromas.It may provide an optimal approach for clinicians wherein a combined treatment of various lasers and electric devices is effective for complicated,protuberant,and firm angiofibromas of specific patients.

CO_(2)LASER PLUS PHOTODYNAMIC THERAPY VERSUS CO_(2)LASER IN THE TREATMENT OF CONDYLOMA ACUMINATUM:A RANDOMIZED COMPARATIVE STUDY

To compare the efficacy and safety of CO_(2)laser plus 5-aminolevulinic acid(ALA)photodynamic therapy(PDT)with CO_(2)laser for the treatment of multiple condyloma acuminatum(CA),120 patients with multiple CA were allocated into two groups—combined group(CO_(2)laser plus ALA-PDT,n=60)and CO_(2)laser group(CO_(2)laser plus placebo-PDT,n=60).After CO_(2)laser,a 20%ALA or a placebo solution was applied to the CA area 3 h before illumination with red light(635 nm,100mW/cm^(2),80 J/cm^(2)).The treatment was repeated seven days after the first treatment if the lesions were not completely resolved.The complete response rate,recurrence rate and adverse effects in the two groups were analyzed.After two treatments,the complete response rates in the CO_(2)laser group and combined group were 100%(509/509)and 100%(507/507)in the CA(p>0:05),respectively.The recurrence rates in the CO_(2)laser group and combined group were 44.9%(229/509)and 10.6%(54/507)in the CA(p<0:05),respectively.The adverse effects in CO_(2)laser group was more than that in combined group.The combined group is a more effective treatment for multiple CA compared with CO_(2)laser group.T/S.Style the highlighted text as abstract.

Three-dimensional transient simulation of CO_(2) laser tissue vaporization and experimental evaluation with a hydrogel phantom

A quantitative analysis method of CO_(2) laser treatments promotes laser treatment performance and rapid clinical application of novel treatment devices.The in silico clinical trial approach,which is based on computational simulation of light-tissue interactions using the mathematical model,can provide quantitative data.Although several simulation methods of laser tissue vaporization with CO_(2) laser treatments have been proposed,validations of the CO_(2) laser wavelength have been insuffcient.In this study,we demonstrated a tissue vaporization simulation using a CO_(2) laser and performed the experimental validation using a hydrogel phantom with constant physical parameters to evaluate the simulation accuracy of the vaporization process.The laser tissue vaporization simulation consists of the calculation of light transport,photothermal conversion,thermal diffusion,and phase change in the tissue.The vaporization width,depth,and area with CO_(2) laser irradiation to a tissue model were simulated.The simulated results differed from the actual vaporization width and depth by approximately 20%and 30%,respectively,because of the solubilization of the hydrogel phantom.Alternatively,the simulation vaporization area for all light irradiation parameters,which is related to the vaporization amount,agreed well with the actual vaporization values.These results suggest that the computational simulation can be used to evaluate the amount of tissue vaporization in the safety and effectiveness analysis of CO_(2) laser treatments.

Prediction and Analysis of Surface Quality of Northeast China Ash Wood during Water-Jet Assisted CO_(2) Laser Cutting

As a natural and environmentally friendly renewable material,Northeast China ash wood(NCAW)(Fraxinus mandshurica Rupr.)was cut by water-jet assisted CO_(2) laser(WACL),the surface quality was evaluated by surface roughness of cut section.The surface roughness was measured by three-dimensional(3D)profilometry.Furthermore,the micromorphology of machined surface was observed by scanning electronic microscopy(SEM).Carbon content changes of machined surface were measured by energy dispersive spectrometer(EDS).A relationship between surface roughness and cutting parameters was established using response surface methodology(RSM).It is concluded that the cutting speed,laser power and water pressure played an important role in surface roughness of cut section.The surface roughness increased as an increase in laser power.It decreased caused by increasing of cutting speed and water pressure.Measurements revealed that the surface quality of NCAW part was improved using the optimized combination of cutting parameters.The established quadratic mathematical model of a good prediction is helpful for matching suitable cutting parameters to obtain expected surface quality.

Corrosion Resistance of AZ91 Magnesium Alloy after Laser Remelting Treatment

The main objective of the study was the modification of the surface layer of magnesium alloy by the COlaser. The studied material was the commercial AZ91 magnesium alloy. The effectiveness of the alternations caused by the remelting process was verified on the basis of microscopic observation and corrosion investigations, i e, recording of potentiodynamic polarization curves, electrochemical noise measurements and hydrogen evolution rate measurements. For the adopted range of the treatment parameters, favourable changes were observed in the surface layer such as the refinement of structure and more uniform arrangement of individual phases. As a consequence of those favourable structural changes the improvement of the corrosion resistance of the alloy was achieved in comparison to its non-remelted equivalent. For the treated material corrosion rates expressed as corrosion current densities were at least three times lower than the appropriate values for the untreated alloy comparing them for the same period of samples immersion in the test solution. The obtained results have confirmed the effectiveness of the applied surface treatment resulting in favourable changes in the structure and corrosion properties of the AZ91 magnesium alloy.

NH_(3)laser THz emission under optical pumping by“long”(~100μs)CO_(2)laser pulses

Terahertz(THz)NH_(3) lasing with optical pumping by electron-beam-sustained discharge“long”(~100μs)CO_(2) laser pulses was obtained.The NH3laser emission pulses and the“long”pulses of the CO_(2) pump laser were simultaneously measured with nanosecond response time.The NH3 lasing duration and its delay with respect to the pump pulse were measured for various CO_(2) laser pulse energies.For the CO_(2) laser pump line 9R(30),three wavelengths of 67.2,83.8,and 88.9μm were recorded.For the CO_(2) laser pump line 9R(16),only a single NH3 laser line with a wavelength of 90.4μm was detected.

Flexible omnidirectional reflective film for CO_(2)laser protection

In this Letter,we presented a flexible omnidirectional reflective film made of polymer substrates and multiple alternating layers of two chalcogenide glasses for full-angle CO_(2) laser protection.The structure parameters of the device were simulated for theoretical prediction of best device structure.The reflector was fabricated by alternate thermal evaporation of two chalcogenide glasses with large refractive index contrast.The reflectivity was greater than 78%at 10.6μm.The flexible reflective film can provide an effective solution for full-angle CO_(2) laser protection of the moving targets,such as laser operators and mobile optical components,with potential applications for wearable laser protective clothing.

Endoscopic stapedotomy:A comparison between the conventional approach versus CO_(2)laser‐assisted surgery

Background:Although the utility of laser fiber in microscopic stapes surgery has been documented in the past,their role can be highly emphasized in endoscopic stapes surgery,especially in difficult anatomical situations.Methods:This is a retrospective analysis of cases where a total of 46 patients(22 in conventional stapedotomy and 24 in CO_(2) laser‐assisted stapedotomy)were included in the study.The clinical parameters were assessed both in the preoperative and postoperative periods in the respective groups and later compared 12 weeks after stapedotomy.Results:A total of 90.90%(20/22)of the patients in the conventional stapedotomy and 95.83%(23/24)of patients in laser‐assisted stapedotomy had<20 dB of AB gap in the postoperative period(P=0.71).Canaloplasty was required in six patients in the conventional stapedotomy and none of the patients in the laser group needed the same(P=0.01).Chorda tympani nerve was manipulated in 59.09%(13/22)and 25.00%(6/24)of cases in the conventional group and in the CO_(2) laser group,respectively(P=0.01).Conclusion:Although the audiological outcomes with fiber‐enabled CO_(2) laser in endoscopic stapedotomy are comparable to conventional surgery,it is a better tool in a narrow auditory canal,requiring minimal manipulation of the chorda tympani nerve.

Ablative fractional CO_(2)laser surgery improving sleep quality,pain and pruritus in adult hypertrophic scar patients:a prospective cohort study

Background:Poor sleep quality is associated with a decrease in quality of life in patients with major burn scars,combined with pruritus and pain.Few interventions have been reported to improve the sleep quality of patients with scars.In the current prospective cohort study,we investigated the efficacy of CO_(2)-ablative fractional laser(AFL)surgery vs conventional surgery in post-burn patients with hypertrophic scars with sleep quality as the primary study outcome.Methods:In total 68 consecutive patients undergoing scar surgical treatment were recruited,including a CO_(2)-AFL surgery cohort(n=35)and a conventional surgery cohort(n=33).A subgroup from the AFL cohort was selected.Sleep quality,pain and pruritus were evaluated.Multiple linear regression analyses were performed to reveal the effect of CO_(2)-AFL surgery.Results:The CO_(2)-AFL surgery cohort had significantly lower Pittsburgh sleep quality index(PSQI)global scores than the conventional surgery cohort after the last surgical treatment.In the subgroup of patients receiving hardware sleep monitoring,CO_(2)-AFL markedly increased deep sleep time,deep sleep efficiency and reduced initial sleep latency.Compared to the conventional surgery cohort,the CO_(2)-AFL cohort presented significantly lower pain and pruritus scores.Correlation analysis showed pain and pruritus were significantly associated with PSQI scores,and there were also significant correlations between pain and pruritus scores.Multiple linear regression analysis showed that surgery method was negatively linearly correlated with visual analog scale(VAS)pain score,brief pain inventory(BPI)total,VAS pruritus score,5-D itch scale total,four-item itch questionnaire(FIIQ)total and PSQI total.Conclusions:CO_(2)-AFL surgery significantly improved sleep quality and reduced pain and pruritus of hypertrophic scar patients.The alleviation of sleep disorder was associated with improvement of deep sleep quality including deep sleep time and deep sleep deficiency.Trial registration:The Chinese Clinical Trial Registry(ChiCTR200035268)approved retrospectively registration on 5 Aug 2020.

Highly sensitive torsion sensor based on triangular-prism-shaped long-period fiber gratings

We propose and investigate a compact optical fiber sensor that aims to measure the torsion in both amount and direction with high sensitivity.This sensor is configured by a triangular-prism-shaped long-period fiber grating,which is fabricated by the high frequency CO_(2) laser polished method.The unique design of the triangular-shaped structure breaks the rotational symmetry of the optical fiber and provides high sensitivity for torsion measurement.In preliminary experiments,the torsion response of the sensor achieves a good stability and linearity.The torsion sensitivity is 0.54 nm/(rad/m),which renders the proposed structure a highly sensitive torsion sensor.

Effects of laser processing parameters on properties of laserinduced graphene by irradiating CO_(2) laser on polyimide

The emerging technique of carbonization of polyimide(PI)by direct laser writing receives great attention for its flexibility,versatility,and ease-of-patterning capability in creating a variety of functional laser-induced graphene(LIG)sensors and devices.LIG prepared by CO_(2) laser irradiating of the PI film is characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),transmission electron microscope(TEM),specific surface area analyzer,synchronous thermal analysis,and Raman spectroscopy with the focus on investigating the effects of laser parameters(e.g.,power,scanning speed)on the microstructure,thickness,and sheet resistance of LIG.Both TEM and XRD indicate that LIG is composed of many graphene layers with a layer spacing of 0.34 nm.The specific surface area of LIG decreases with the increase of laser power.The ratio of the thickness of LIG over the depth of the carbonized PI film as the expansion ratio characterizes the expansibility of LIG.The influence of image resolution and off-focus value on the sheet resistance of LIG is explained by the superposition mechanism of laser scanning spots.

Combined studies of surface evolution and crack healing for the suppression of negative factors during CO_(2) laser repairing of fused silica

In order to reveal the evolution mechanism of repaired morphology and the material's migration mechanism on the crack surface in the process of CO_(2) laser repairing surface damage of fused silica optics, two multi-physics coupling mathematical models with different scales are developed, respectively. The physical problems, such as heat and mass transfer,material phase transition, melt flow, evaporation removal, and crack healing, are analyzed. Studies show that material ablation and the gasification recoil pressure accompanying the material splash are the leading factors in forming the Gaussian crater with a raised rim feature. The use of low-power lasers for a long time can fully melt the material around the crack before healing, which can greatly reduce the size of the residual air layer. Combined with the experimental research, the methods to suppress the negative factors(e.g., raised rim, deposited debris, air bubbles) in the CO_(2) laser repairing process are proposed.

CO_(2)fractional laser-assisted transdermal delivery of silk nanofiber carriers in a rabbit ear hypertrophic scar model

Background:Hypertrophic scars are skin fibrotic diseases,characterized by fibroblast hyperprolif-eration and excessive accumulation of extracellular matrix.However,topical drug application for hypertrophic scars are unsatisfactory.The purpose of this study was to explore the permeability of silk nanofiber hydrogels(SNFs)loaded with rhodamine 6G(R6G)and rhodamine 110(R110)mediated by CO_(2)fractional laser irradiation into hypertrophic scar tissues.Methods:In this work,R6G and R110 were chosen as hydrophilic and hydrophobic model molecules.They were loaded inside SNFs.In vivo rabbit ear hypertrophic scars were treated with CO_(2)fractional laser irradiation and then R6G/R110-laden SNFs were applied to the scars to evaluate their synergetic effect on drug penetration efficiency.Their permeability was quantified by fluorescence intensity and measured by confocal laser scanning microscopy on days 1,3,5 and 7.More specifically,the thermal coagulation zone(CZ)and its surrounding area(peri-CZ)caused by the thermal coagulation of the laser were discussed separately.Results:Our data indicated that the SNFs promoted the penetration of R6G but not that of R110 in the peri-CZ on day 1 when combined with laser irradiation.Interestingly,both R6G and R110 were abundant in the CZ and remained stable on days 1,3 and 5.Moreover,rapid re-epithelialization hindered the long-term permeability of both drugs.Conclusion:Combining CO_(2)fractional laser irradiation with SNF drug delivery could improve the efficiency of hydrophilic drug delivery within 24 h before total re-epithelialization.