Relative Spectral Intensities Research Articles

A preliminary study of polymer optical fiber’s knittability for smart wear applications

PurposeThe purpose of this research is to ascertain the feasibility of fabricating polymer optical fibers (POFs) based textile structures by knitting with Polymethylmethacrylate (PMMA) based optical fibers for textile sensor application. It has long been established that by using the principles of physics, POFs have the capability to function as sensors, detecting strain, temperature and other variables. However, POF applications such as strain and pressure sensing using knitting techniques has since not been very successful due to a number of reasons. Commercially available PMMA-based optical fibers tend to be fragile and susceptible to breakages when subjected to stress during the knitting processes. Also light transmitted within these fibers is prone to leakage due to the curvature that results when optical fibers are interlaced or interlooped within fabric structures.Design/methodology/approachUsing Stoll’s multi-gauge CMS 350 HP knitting machine, five fabric structures namely, 1 × 4 float knit structure, tunnel inlay knit structure, 3:1 fleece fabric and 2:1 fleece fabric structure respectively were used to knit sensor samples. The samples were subsequently tested for length of illumination and sensitivity relative to applied pressure.FindingsThe results of this preliminary study establish that embedding plastic optical fibers into a knitted structure during the fabric formation process for soft strain sensor application possible. The best illumination performance was recorded for tunnel inlay structure which had an average of 94 cm course length of POF being illuminated. Sensor sensitivity experiments also establish that the relative spectral intensity of the fiber is sensitive to both light and pressure. Problems encountered and recommendations for further research have also been discussed and proffered.Research limitations/implicationsDue to resource limitations, an innovative technique (use of precision weight set) was used to apply pressure to the sensors. Consequently, information regarding the extent of corresponding sensor deformation has not been used in this initial analysis.Practical implicationsBecause the fundamental step toward finding a solution to any engineering problem is the acquisition of reliable data, and considering the fact that most of the popular technologies used for soft textile sensors are still bedeviled with the problem of signal instability and noise, the success of this application thus has the tendency to promote the wide spread adoption of POF sensors for smart apparel applications.Originality/valueAs far as research on soft strain sensors is concerned, to the best of the authors’ knowledge, this is the first study to have attempted to knit deformable sensors using commercially available POFs.

Spectral analysis and kinetic modeling of radioluminescence in air and nitrogen.

In this article we present a quantitative analysis of the second positive system of molecular nitrogen and the first negative system of the molecular nitrogen cation excited in the presence of ionizing radiation. Optical emission spectra of atmospheric air and nitrogen surrounding 210Po sources were measured from 250 to 400 nm. Multi-Boltzmann and non-Boltzmann vibrational distribution spectral models were used to determine the vibrational temperature and vibrational distribution function of the emitting N2(C3Πu) and N2+(B2Σ+u) states. A zero-dimensional kinetic model, based on the electron energy distribution function (EEDF) and steady-state excitation and de-excitation of N2(X1Σ+g), N2+(B2Σ+u), N2+(X2Σ+g), N4+, O2+, and N2(C3Πu, v), was developed for the prediction of the relative spectral intensity of both the N2+(B2Σ+u → X2Σ+g) emission band and the vibrational bands of N2(C3Πu → B3Πg) for comparison with the experimental data.

Detection of melanin influence on skin samples based on Raman spectroscopy and optical coherence tomography dual-modal approach.

Melanoma is responsible for more than half of the deaths related to skin cancer in the last few decades. A dual-modality optical biopsy system with Raman spectroscopy and optical coherence tomography approach was built with the goal of achieving noninvasive skin measurement. To mimic melanoma and evaluate the effect of melanin on skin, models have been created by dissolving synthetic melanin in dimethyl sulfoxide and adding it to fresh skin samples. Compared to the untreated samples, morphological images showed that the imaging depth on melanin-treated skin has been increased from 250 μm to 350 μm due to the optical clearing effect of the DMSO solvent, and Raman analysis revealed that relative spectral intensities of melanin-treated samples were lower in the amide-I and CH2 -deformation bands, and higher in the CH2 -twist and C-C stretch bands. Using machine learning for skin type classification, an accuracy of 89% is achieved.

Flame propagation characteristics of premixed hydrogen–air deflagration with low concentration in a pipeline

This study used a visualized explosion propagation experimental system to investigate the flame propagation and hydroxyl (OH·) spectral radiation characteristics of hydrogen deflagration at the hydrogen concentration range of 7–17 vol%. The experimental results indicated that maximum flame propagation velocity, maximum explosion pressure, maximum flame temperature, and maximum relative spectral intensity of OH· gradually increased with hydrogen concentration. When concentration increased from 13 vol% to 17 vol%, the time to reach the maximum flame propagation velocity, the formation time of tulip flame, and the duration of the spectral radiation signal of OH· decreased by 52.9%, 55.6%, and 48.2%, respectively. In addition, flame propagation velocity oscillated when the tulip flame appeared, and maximum explosion pressure appeared later than the maximum temperature. Maximum flame propagation velocity, maximum explosion pressure, and maximum flame temperature positively correlated with maximum relative spectral intensity in the reaction system. These findings may serve as an essential reference for the safe and effective use of hydrogen and the research and development of radical targeted explosion suppressants.

Electron energy loss spectra of sulfur in HgX2S4 (X = Al, Ga, In): A comparative theoretical study

By means of density functional theory based electronic structure calculations and energy loss near edge structure (ELNES) analysis, the present study calculates and describes the sulfur K and L2,3 edge spectra of mercury-based defective chalcopyrites (HgAl2S4 and HgGa2S4) and of its spinel structure (HgIn2S4), and compares with those of cadmium thiogallate (CdGa2S4) and the existing experimental spectra. The substitution of gallium by aluminium changes the sulfur K and L2,3 edge ELNES, decreasing the relative spectral intensities and shifting the main peaks to higher energies. The covalency power and the bond length play the considerable roles in the overall dispersions of the edge spectra.

Satellite-Dominated Sulfur L2,3 X-ray Emission of Alkaline Earth Metal Sulfides.

The sulfur L2,3 X-ray emission spectra of the alkaline earth metal sulfides BeS, MgS, CaS, SrS, and BaS are investigated and compared with spectra calculations based on density functional theory. Very distinct spectral shapes are found for the different compounds. With decreasing electronegativity of the cation, that is, increasing ionic bonding character, the upper valence band width and its relative spectral intensity decrease. These general trends are qualitatively reproduced by the spectra calculations, which give quite an accurate description of the spectral shapes in the upper valence band region. On the low energy side of the sulfur 3s → 2p transition dominating the spectra, we find strong satellites caused by "semi-Auger" decays involving configuration interaction. These satellites, previously believed to be energetically forbidden for sulfur L2,3 emission and only observed for the L2,3 emission of Cl to Cr, increase in intensity as the bonding character becomes more ionic and dominate the spectra for SrS and BaS. The intensities, energies, and widths of the satellites vary strongly between the investigated compounds, giving a very specific spectral fingerprint that can be used for speciation analysis.

Vibrational spectra of human tissues: Experimental data and density functional theory calculations comparison

Biophotonics techniques enabling molecular sensing of tissues and biological samples of had been widely applied to biomedical problems. Vibrational spectroscopy technologies like Fourier-Transform Infrared (FTIR) spectroscopy is a well-reported example. However, the correct interpretation of measured vibrational spectra of macromolecules and tissues emerging from the complexity of structures is a challenge. Computer simulations can be used as a strategic method to understand interactions between specific parts of a macromolecule. Here we present two implementations of vibrational calculations based on diagonalization of Hessian matrix obtained via Density Functional Theory calculations using Car-Parrinello Molecular Dynamics (CPMD package), Born-Oppenheimer Molecular Dynamics quickstep GPW (CP2K package), and a molecular dynamics calculations based on tight binding (CP2K-TB) was also employed to obtain FTIR spectra via electric dipole correlation function. These calculations were proposed to capture vibrational pieces of information related to FTIR of the human oral mucosa. Eleven models of peptide which represents collagen type I macromolecule including confined water molecules (ranging from 0 to 8 waters), were tested. CPMD and CP2K methods presented an excellent agreement of vibrational bands positions and maximum intensity to experimental data (goodness-of-fit R2 ∼ 0.90). On the other hand, this agreement was very poor for the CP2K-TB case in spite of the correct overall relative spectral intensity with respect to experimental data. We found that the peptide model enclosing eight waters (labeled C8) in CPMD calculations presented the highest value of R2 = 0.99. The CPMD method, despite some limitations, outperformed the CP2K calculation in our case. Here we only used a collagen cutout and confined water, but it is possible to add other molecules such as proteoglycans to investigate and characterize a tissue. The short collagen mimetic peptide has implications for the conformational behavior of native collagen. The method itself can be used for other macromolecules. Furthermore, we assignment of vibrational modes in the high-wavenumber region ( > 2, 000▒cm−1) is also presented.

Structural, spectroscopic and electron collisional studies of isoxazole (C3H3NO)

• Comprehensive structural, spectroscopic and electron collision data of Isoxazole. • DFT calculations of ground state geometry and vibrational frequencies. • Comparison with earlier data; confirmation/revision of vibronic assignments. • Vertical excitation energies for singlet and triplet states using TDDFT. • Low energy electron scattering data for Isoxazole from 0.1-20 eV. The structural, spectroscopic, and electron collision data of Isoxazole (C 3 H 3 NO) were subjected to extensive computational studies. Spectroscopic calculations were performed on ground and excited states using the density functional theory (DFT) and the time dependent density functional theory (TDDFT) respectively. Ground state geometry and vibrational frequencies agree well with earlier works and lead to re-assignment of a few vibrational bands. Theoretically predicted singlet and triplet excitation energies are in good agreement with earlier experimental data, while predicted oscillator strengths of singlet states correlate well with the observed relative spectral intensities. The electron collision data for isoxazole molecule were calculated using Quantemol-N, which employs the UK Molecular R-matrix codes. These calculations were performed for the total elastic cross-sections along with their symmetrical components, differential and momentum transfer cross-sections, inelastic scattering cross-sections comprising of discrete electronic excitation, ionization and dissociative electron attachment processes. We employed the two most popular theoretical approaches to calculate the electron impact ionization cross-sections viz. Complex scattering potential-ionization contribution (CSP-ic) and the Binary encounter Bethe (BEB) model. The rate coefficients for elastic and inelastic processes were estimated over a wide electron temperature range. In addition to scattering calculations, the other motivation was to obtain resonances which are signatures of many significant low energy phenomena. The first two peak correspond to π* shape resonances which are observed at 2.1 eV and 4.69 eV and are in accordance with the earlier reported data. The third peak is observed at 10.96 eV which may be attributed to the σ* shape resonance.

Highly Sensitive and Specific Mass Spectrometric Platform for miRNA Detection Based on the Multiple-Metal-Nanoparticle Tagging Strategy.

The multiple-metal-nanoparticle tagging strategy has generally been applied to the multiplexed detection of multiple analytes of interest such as microRNAs (miRNAs). Herein, it was used for the first time to improve both the specificity and sensitivity of a novel mass spectroscopic platform for miRNA detection. The mass spectroscopic platform was developed through the integration of the ligation reaction, hybridization chain reaction amplification, multiple-metal-nanoparticle tagging, and inductively coupled plasma mass spectrometry. The high specificity resulted from the adoption of the ligation reaction is further enhanced by the multiple-metal-nanoparticle tagging strategy. The combination of hybridization chain reaction amplification and metal nanoparticle tagging endows the proposed platform with the feature of high sensitivity. The proposed mass spectrometric platform achieved quite satisfactory quantitative results for Let-7a in real-world cell line samples with accuracy comparable to that of the real-time quantitative reverse-transcriptase polymerase chain reaction method. Its limit of detection and limit of quantification for Let-7a were experimentally determined to be about 0.5 and 10 fM, respectively. Furthermore, due to the unique way of utilizing the multiple-metal-nanoparticle tagging strategy, the proposed platform can unambiguously discriminate between the target miRNA and nontarget ones with single-nucleotide polymorphisms based on their response patterns defined by the relative mass spectral intensities among the multiple tagged metal elements and can also provide location information of the mismatched bases. Its unique advantages over conventional miRNA detection methods make the proposed platform a promising and alternative tool in the fields of clinical diagnosis and biomedical research.

Characteristics of discharge and beyond extreme ultraviolet spectra of laser induced discharge gadolinium plasma

The gadolinium (Gd) plasma is a potential beyond-EUV (BEUV) source for the extension of extreme ultraviolet lithography at 13.5 nm. A laser induced discharge plasma (LDP) is an effective way to excite the target material into high temperature plasma. A pulsed CO2 laser ablates a Gd plate cathode and produces an initial plasma, triggers a discharge between a Gd plate cathode and a stainless-steel cone anode, the current produces high temperature discharge plasma and creates an environment for BEUV radiation. A RLC model is used to estimate the equivalent circuit resistance and inductance, the resistance is about 0.70–0.75 Ω and the inductance is about 2.3–2.4 μH. A grazing incident ultraviolet spectrometer is established to study the Gd plasma’s BEUV radiation. With the laser energy above 120 mJ and voltage above 6.7 kV, Gd plasma spectra near the 6.7 nm is obtained. It is found that the relative spectral intensity increases and the peak of emission moves to a shorter wavelength corresponding to a higher voltage and laser energy. An atomic code combined with a simplified collisional-radiative model is used to calculate the theoretical spectra and estimate the electron temperature and density range of the LDP plasma.

Electromyographic traces of motor unit synchronization of fatigued lower limb muscles during gait.

The study of the signal in the frequency domain has shown to be a good tool to identify muscular fatigue. Previous research has shown that the low frequency band and 40Hz frequency band increase their relative intensity with the onset of fatigue. These findings were obtained in rectus femoris, but the behaviours of other muscles of the lower limb are unknown. In this article we explored the changes in the low frequency and 40Hz frequency band of lower limb muscles with respect to fatigue. Thirty healthy subjects were recruited to analyse the electromyography (EMG) of biceps femoris, tibialis anterior and gastrocnemius medialis and lateralis of both legs during gait. Four two-minutes walks at a self-selected speed were recorded, the first two walks with a normal muscular function and the last two walks after a fatigue protocol. All the signals were decomposed using wavelet transformations. The signals were normalized in time and spectral intensities normalized to the sum of intensities in the frequency domain. Two frequency bands were studied in each walk: the 40-Hz (34-53Hz) and the low frequency (< 25Hz) bands. A ratio of the spectral intensities of those frequency bands at each walk was obtained by dividing the 40-Hz frequency band spectral intensity by the low frequency band spectral intensity. Statistical parametric mapping techniques were used to compare the ratios of the prefatigue walks against the postfatigue walks. The results of the Statistical Non-Parametric Mapping (SnPM) analysis of all muscles depict a higher relative spectral intensity in the low frequency band in the comparison of fatigue versus prefatigue recordings except for the right gastrocnemius lateralis. The critical thresholds F* were exceeded by multiple suprathreshold clusters with p values <0.05, showing that the low frequency band increased its relative spectral intensity in the case of fatigue. The obtained results suggest that the low frequency band increases its relative spectral intensity in all the studied muscles when fatigue onsets. This increase in relative spectral intensity may be linked to an increase in motor unit synchronization promoted by the central nervous system to ensure good motor control.

Ultra-high quality graphene perfect absorbers for high performance switching manipulation.

Wavelength-selective light absorption and the related switching operations are highly desired in optical devices. Herein, we report the approach for ultra-high quality (Q) graphene perfect optical absorption, which possesses impressive performance in switching manipulation. A record-breaking Q-factor (up to 105) is observed, suggesting one or two orders of magnitude larger than that of the conventional graphene absorbers. The ultra-low external leakage loss rate of quasi-bound states in the continuum (BIC) resonator and the ultra-low intrinsic absorption loss rate in the resonant mode volume are the main contributions for the ultra-high Q perfect absorption. By introducing a Kerr nonlinear medium, spectral relative intensity can be changed from 0 to 100% when an ultra-low pump light with the intensity of only 5 kW cm-2 is used. After a rather slight tuning of the refractive index (Δn = 5×10-4) for the resonators, the absorption contrast ratio reaches 31 dB. The switching related spectral wavelength shift sensitivity is up to 915 nm/RIU and the figure of merit (FOM) is 50 833. These features confirm the ultra-high tunability and switching manipulation. It is believed that the ultra-high Q-factor absorption offered by all-dielectric configuration provides plentiful potential applications for graphene-based devices in the all-optical switch, modulator, notch filter, etc.

Highly reproducible SERS sensor based on self-assembled Au nanocubic monolayer film for sensitive and quantitative detection of glutathione

The detection of glutathione (GSH) in human serum is significant for the clinical diagnosis of various diseases, such as Alzheimer's disease and cancer. A sensitive surface enhanced Raman scattering (SERS) sensor is proposed to detect low-concentration biomolecule GSH. The sensor is built based on a dense monolayer film of self-assembly Au Nano cubes. The film has an excellent enhancement effect on the probe molecule DTNB. After the GSH molecule is continuously added, the disulfide bond in DTNB breaks into TNB molecule. In a neutral or alkaline environment, TNB will be hydrolyzed into anions, and bind to the surface of the positively charged Au NCs film through electrostatic interaction, thereby enhancing the Raman spectroscopy of TNB. As a result, the proposed sensor can detect low concentrations GSH. The detection limit is 50 nM, and the relative spectral intensity of TNB characteristic peak existed good linear relationship with the concentration of GSH between 50 and 750 nM. The SERS substrate used in the sensor is easy to prepare, with high uniformity and reproducibility, the sample does not require complicated pre-processing and preparation. The SERS sensor provides a novel strategy for sensitive and quantitative detection of the trace analytes and has potential for clinical applications.

Analysis of Salt Mixture Contamination on Insulators via Laser-Induced Breakdown Spectroscopy

The composition of contamination deposited on transmission line insulators can affect their surface flashover voltage. Currently, there is no rapid on-line method to detect this contamination composition in power grids. In this paper, we applied laser-induced breakdown spectroscopy (LIBS) to analyze contamination on insulator surfaces. Usually, Na and Ca salts are found in contamination along with various sulfate, carbonate, and chloride compounds. As an element’s detection method, LIBS can only measure a certain element content, for example, Ca. The mixture of various compounds with the same cations can influence the LIBS signal. The influence of mixing ratios on the calibration curves and relative spectral intensity was studied via LIBS. Na2CO3, NaHCO3, CaSO4, and CaCO3 samples containing different proportions of Na and Ca were prepared. The linear correlation coefficients (R2) for the Na and Ca calibration curves generated using various mixing ratios were analyzed. The results showed that the mixture ratio did not dramatically affect the linear calibration curves for mixtures containing the same cations. This finding may significantly reduce the difficulty of applying LIBS analysis for complex contamination on insulators. The laser energy density had effects on the spectral characteristics of the measured elements. The partial least-square regression (PLSR) model can improve the accuracy of Na and Ca prediction.

Analysis of Pollution in High Voltage Insulators via Laser-Induced Breakdown Spectroscopy.

Surface pollution deposition in a high voltage surface can reduce the surface flashover voltage, which is considered to be a serious accident in the transmission of electric power for the high conductivity of pollution in wet weather, such as rain or fog. Accordingly, a rapid and accurate online pollution detection method is of great importance for monitoring the safe status of transmission lines. Usually, to detect the equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD), the pollution should be collected when power cut off and bring back to lab, time-consuming, low accuracy and unable to meet the online detection. Laser-induced breakdown spectroscopy (LIBS) shows the highest potential for achieving online pollution detection, but its application in high voltage electrical engineering has only just begun to be examined. In this study, a LIBS method for quantitatively detecting the compositions of pollutions on the insulators was investigated, and the spectral characteristics of a natural pollution sample were examined. The energy spectra and LIBS analysis results were compared. LIBS was shown to detect pollution elements that were not detected by conventional energy spectroscopy and had an improved capacity to determine pollution composition. Furthermore, the effects of parameters, such as laser energy intensity and delay time, were investigated for artificial pollutions. Increasing the laser energy intensity and selecting a suitable delay time could enhance the precision and relative spectral intensities of the elements. Additionally, reducing the particle size and increasing the density achieved the same results.

Filamentation and supercontinuum emission generated from flattened femtosecond laser beam by use of axicon in fused silica

It is important to control the femtosecond laser filamentation and the supercontinuum (SC) for their potential applications. The use of axicon is beneficial to the filamentation elongation and SC enhancement, because the axicon can convert the incident laser into a Bessel beam and forms a unique longer depth of focus region. On the other hand, the flattened laser beam which has a uniform distribution of the beam intensity, can propagate in condense media with a higher incident energy than that of Gaussian laser beam. It has unique advantages in forming a SC with high energy and high conversion efficiency. In this paper, we combine the use of axicon and the flattened laser beam to form filament and SC in fused silica. First, we study the filamentation generated by the Gaussian beam and the flattened beam, respectively, with the same incident pulse energy (672 μJ). The results show that the flattened beam can generate filament with relative uniform intensity distribution in the focal depth of the axicon and the intensity is relatively smaller than that of the Gaussian beam. It suggests that the flattened laser beam can propagate in fused silica with a higher energy than Gaussian beam. Second, we study the filamentation of the flattened beam of 1.319 mJ. In this case, the filament intensity is close to that of the Gaussian beam with 672 μJ. Moreover, the filamentation of the flattened beam with 1.319 mJ is longer and the intensity distribution is more uniform than that of the Gaussian beam with 672 μJ. Therefore, a flattened laser beam can generate the SC with a higher energy than that of the Gaussian beam in fused silica. The comparison of the spectra shows that the relative spectral intensity of flattened beam with 1.319 mJ in the range of 550–700 nm is much higher than that of the Gaussian beam with 672 μJ. The conversion efficiency of the Gaussian beam and the flattened beam is 32.58% and 39.59%, respectively. It can be seen that the flattened laser beam has advantages not only in generating long and uniform filament, but also in generating the intense SC. This approach is helpful to many applications, such as white light LIDAR and micro-nano processing.

PH-Responsive mixed-thiol-modified surface of roughened GaN: A wettability and SERS study

Chemical etching of gallium nitride (GaN) crystals produces various morphological patterns such as ‘nanowhiskers’. Due to the microscopic roughness etched GaN surfaces may be converted via further chemical functionalization into superhydrophobic materials or substrates for surface-enhanced Raman scattering (SERS). Here, properties of Au-sputtered GaN nanowhiskers functionalized with two mixed thiols: aliphatic non-polar 1-butanethiol (C4SH) and aromatic ionizable 4-mercaptobenzoic acid (4-MBA) are characterized. Changing the ratio of two thiols results in large variations of water droplet contact angle. Coinciding sigmoidal pH-dependencies of the contact angle and relative spectral SERS intensities assigned to ionized 4-MBA species are observed for surfaces with approximately 1:2 M 4-MBA:C4SH ratio. Stability of 4-MBA + C4SH layers was probed through thiol-exchange with a non-ionizable aromatic thiol: 2-naphthalenethiol (2NT). While the SERS characteristics of (4-MBA + C4SH)-Au/GaN platform exposed to 2NT acquires new spectral features the layer maintains pH-responsive wettability indicating the presence of 4-MBA possibly conserved through the π-stacking interaction with 2NT. Our results demonstrate that deposition of multicomponent thiol layers on nanowhiskers could facilitate development of pH-responsive self-cleaning sensors based on GaN. The results are discussed in light of mechanisms underlying superhydrophobicity and SERS.

Simple Defocused Fiber Optic Volume Probe for Subsurface Raman Spectroscopy in Turbid Media.

We investigated the ability to perform deep subsurface Raman spectroscopy in turbid media using a simple fiber optic volume probe. Being able to collect Raman signals from regions deep within a biological sample provides the ability to noninvasively study underlying living tissue and tissue engineered constructs with high chemical specificity. Spatially offset Raman spectroscopy has shown great potential for obtaining subsurface Raman signals in biological samples. The applicability of the method for invivo studies depends on the system complexity and small size probes are often desirable. Most real-time studies on human patients utilizing Raman spectroscopy have been performed with easy-to-handle miniaturized probes. Here we show both experimentally and theoretically that the sampling depth from a simple volume probe can be controlled by changing the probe to sample distance effectively suppressing Raman and fluorescence contributions from shallow sample layers while favoring the collection of signals from deeper layers. Relative spectral intensities as function of probe to sample distance were investigated for layered phantoms of poly(methyl methacrylate) and trans-stilbene and compared with theory. The volume probe was then utilized for the collection of spectra from phantoms mimicking invivo transcutaneous measurement configurations of bone and engineered scaffold as well as from an ex vivo sample of bone and soft tissue. Together the results show that Raman fiber optic volume probes can be utilized for subsurface Raman spectroscopy in turbid media, providing a simple alternative to spatially offset Raman systems for, e.g., noninvasive monitoring and studying mineralized tissue and implanted scaffolds invivo.

Towards a Database for the Relative Spectral Lines' Intensities of Laser-Induced Breakdown spectra

The relative intensity is one of the parameters of the spectral lines that indicate the emission strength of such lines. The spectral lines relative intensity database for most elements has been recorded a long time ago through spectroscopic data obtained by arc, spark, and vacuum tube. The problem is that relative line intensity is source dependent and the current database cannot be used for Laser-Induced Breakdown Spectroscopy (LIBS). Since LIBS is dealing with transient plasma, then a lot of parameters should be studied in order to find suitable conditions and a suitable way to record this database. In this work, we are trying to find a way to construct a database for relative lines intensities that can be used properly in LIBS analysis. The LIBS spectral lines have been recorded for different delay times for different copper alloy samples. Then, some chosen copper’ spectral lines were compared. An empirical formula has been proposed to calculate the spectral line intensity for each delay time. It was found that for delay times between 1000 ns and 2000 ns the spectral lines were related together in a way that the copper concentration doesn’t affect the spectral line relative intensity but it only affects the value of the spectral line intensity.

The influences of welding parameters on the metal vapor plume in fiber laser welding based on 3D reconstruction

Fiber laser has significant advantages in the welding of moderately thick stainless steel plates. However, the influences of welding parameters on interaction behavior are still not fully understood. The metal vapor, as process product of fiber laser welding, carries abundant information of interaction behavior. A novel three-dimensional reconstruction technique was used to establish spatial structure of metal vapor during fiber laser welding. The spatial field of temperature and electron density were computed based on the 3D distribution of radiation intensity, as well as the relative spectral intensity method. Experimental results showed that the temperature of the metal vapor was generally at about 4000–5500 K. Defocusing amount had a significant influence on metal vapor and its energy interaction process in fiber laser welding.