Innovative rapid liquid concentration measurement based on thermal lens effect and machine learning.

This study addresses the critical need for rapid and online measurement of liquid concentrations in industrial applications. Although the thermal lens effect (TLE) is extensively explored in laser systems for determining thermal lens focal lengths, its application in quantifying solution concentrations remains underexplored. This research explores the relationship between various liquid concentrations and the interference fringes induced by the TLE. A novel approach is introduced, utilizing TLE to measure solution concentrations, with integration of image processing and discrete Fourier transform (DFT) techniques for feature extraction from interference rings. Further, machine learning, specifically backpropagation artificial neural network (BP-ANN), is employed to model concentration measurement. The model demonstrates high accuracy, evidenced by low root mean square error (RMSE) values of 3.055 and 5.396 for the training and test sets, respectively. This enables precise, real-time determination of soy sauce concentration, offering significant implications for industrial testing, environmental monitoring, and other related fields.

Real-time in-situ optical detection of fluid viscosity based on the Beer-Lambert law and machine learning.

As an important physical quantity to describe the resistance of fluid to flow, viscosity is an essential property of fluids in fluid mechanics, chemistry, medicine, as well as hydraulic engineering. While traditional measurement methods, including the rotating-cylinder method, capillary tube method and falling sphere method, have significant drawbacks especially in terms of accuracy, response time and the sample must be made to move. In this work, a novel Beer-Lambert law-based method was proposed for the viscosity measurement. Specifically, this work demonstrates that viscosity can be quantitatively reflected by spectral line intensity, and castor oil was selected due to its viscous temperature properties (viscosity has been accurately measured under different temperature), and its transmission spectrum at different temperatures ranging from 10 to 50°C was detected firstly. Then, the principal component analysis (PCA) was employed to obtain the intrinsic features of the transmission spectrum. Finally, the processed data was utilized to train and verify the radial basis function (RBF) neural network. As a result, the accuracy of the predictions conducted by means of the RBF reached 98.45%, which indicates the complicated and non-linear relationships between spectra formation and viscosity can be depicted well by RBF. The results show that the real-time in-situ optical detection method adopted in this work represents a great leap forward in the viscosity measurement, which fundamentally reforms the traditional viscosity measurement methods.

Lateral shifts of linearly- and radially-polarized Bessel beams scattered by a nanosphere.

We report the investigation on the lateral shifts that linearly-polarized (LP) and radially-polarized (RP) Bessel beams experience during the Mie scattering by a nanosphere. A numerical procedure based on the angular spectrum theory is developed to solve the scattered electromagnetic field and subsequent lateral shifts with a high computational efficiency, which can be easily applied to an arbitrary shaped polarized beam. The influences of different factors, including conical angle, nanosphere radius and position, on the lateral shifts are systematically investigated. The results demonstrate that for on-axis scattering, a LP Bessel beam can be regarded as a plane wave with the same polarization state but an equivalent longer wavelength, while a RP Bessel beam can be regarded as a plane wave with a polarization state along the propagation direction exhibiting independence on the conical angle. The findings help deepen our understandings of lateral shifts in light scattering of vectorial non-diffractive beams.

Dynamically Switchable Polarization-Independent Triple-Band Perfect Metamaterial Absorber Using a Phase-Change Material in the Mid-Infrared (MIR) Region.

A tunable metamaterial absorber (MMA) by reversible phase transitions in a mid-infrared regime is theoretically investigated. The absorber is composed of a molybdenum (Mo)-germanium-antimony-tellurium (Ge2Sb2Te5, GST)-Mo nanodisk structure superimposed on the GST-Al2O3 (aluminum oxide)-Mo film. Studies have shown that the combination of the inlaid metal-medium dielectric waveguide mode and the resonant cavity mode and the excitation of the propagating surface plasmon mode are the main reasons for the formation of the triple-band high absorption. Additionally, through the reversible phase change, the transition from high absorption to high reflection in the mid-infrared region is realized. The symmetry of the absorber eliminates the polarization dependence, and the near unity absorption efficiency can be maintained by incidence angles up to 60°. The presented method will enhance the functionality of the absorber and has the potential for the applications that require active control over light absorption.

Machine-learning-based computationally efficient particle size distribution retrieval from bulk optical properties.

Retrieval of particle size distribution from bulk optical properties based on evolutionary algorithms is usually computationally expensive. In this paper, we report an efficient numerical approach to solving the inverse scattering problem by accelerating the calculation of bulk optical properties based on machine learning. With the assumption of spherical particles, the forward scattering by particles is first solved by Mie scattering theory and then approximated by machine learning. The particle swarm optimization algorithm is finally employed to optimize the particle size distribution parameters by minimizing the deviation between the target and simulated bulk optical properties. The accuracies of machine learning and particle swarm optimization are separately investigated. Meanwhile, both monomodal and bimodal size distributions are tested, considering the influences of random noise. Results show that machine learning is capable of accurately predicting the scattering efficiency for a specific size distribution in approximately 0.5 µs on a standalone computer. Therefore, the proposed method has the potential to serve as a powerful tool in real-time particle size measurement due to its advantages of simplicity and high efficiency.

Geometrical optics approximation for plane-wave scattering by a rectangular groove on a surface.

Rigorous solution of plane-wave scattering by a groove based on electromagnetic theory will be time-consuming if the groove width is much larger than the illumination wavelength. To accelerate the computation, an approach based on geometrical optics approximation is developed here. The incident beam is split into several parts during reflection and refraction. Contribution of every part is superposed to obtain the electric field at the interface between the groove and air, with which diffraction theory is utilized to calculate the far-field scattered light. Results demonstrate that the approach is capable of accurately calculating plane-wave scattering by rectangular grooves with large widths in a time-efficient manner, which can be beneficial for further inverse scattering problems.

Scattering of an Airy light sheet by a chiral sphere.

Scattering of a 1D Airy beam light sheet by a chiral sphere is numerically studied within Mie theory and the plane-wave spectrum method. To testify to the validity of our code and method, the results of scattering intensity of a chiral sphere by an Airy beam light sheet reducing to a homogeneous isotropic sphere are compared with those in existing literature, which shows that these results are in good agreement. Influences of different parameters on differential scattering cross sections in the far field are investigated in detail, including the chiral parameters, sphere radius, and beam position. It is found in the scattering intensity of an Airy beam by a chiral sphere that the chiral sphere, which is compared with a homogeneous isotropic sphere, can decrease the scattering intensity in a region, and the scattering intensity distribution is sensitive to the x0 position of the Airy beam.

Propagation of a Bessel-Gaussian beam in a gradient-index medium.

Based on the ABCD matrix method and Collins diffraction integral formula, analytical expression for Bessel-Gaussian beam propagation in a gradient-index medium is derived. The propagation trajectory, intensity, and phase distributions of the zeroth-order, second-order, and superposition cases are numerically investigated. The effect of beam waist radius w0 on the properties of beam propagation in a gradient-index medium is discussed in detail. The result shows that the beam is focused at z/L=N/2 (N=0,1,2,…) and propagates periodically in the medium. Evolution of the vortical structure of the superposed Bessel-Gaussian beam is investigated, showing that the superposed beam forms new singularities, and the rotation of the beam occurs mainly near the singularities.

Vision system with high dynamic range for optical surface defect inspection.

We report a machine vision system with high dynamic range designed for optical surface defect inspection. The system consists of two motorized linear stages and one motorized rotation stage for automatically scanning the surface. As the intensity of long scratches and digs differ a lot under dark-field illumination, gains of red, green, and blue channels are set to be different values to extend the dynamic range of an ordinary colored detector in a single snapshot, which greatly improves the efficiency compared with multiexposure-based approaches. Image stitching is then employed to get a high-resolution image of the entire optical surface for further processing to quantitatively evaluate surface quality based on the standards of MIL-PRF-13830B and ISO 10110-7:2008. The system can be widely applied in the optical industry, as it provides a low-cost solution for optical surface quality checks.

[Aerosol Optical Properties in the Northern Suburb of Nanjing During Haze Days in January 2013].

In January 2013 large-scale, continuous and severe haze occurred in Nanjing. Three-wavelength photoacoustic soot spectrometer (PASS-3) was used for real-time, online and situ measurements of aerosol absorption and scattering coefficients in the northern suburb of Nanjing during January 2013. The results indicated that the average aerosol absorption and scattering coefficients were (83.20 ± 35.24) Mm⁻¹ and (670.16 ± 136.44) Mm⁻¹ during haze days, which were 3.85 and 3.45 times higher than those on clean days, respectively. The diurnal variation of absorption and scattering coefficients showed a bimodal distribution. The mean single scattering albedo and scattering Angstrom exponent were (0.89 ± 0.04) and (1.30 ± 0.27) respectively, indicating the predominance of scattering fine particles during haze days in Nanjing. Aerosols could be significantly removed by precipitation. The absorption and scattering coefficients showed negative correlations with surface wind speed, and the single scattering albedo and Angstrom exponent showed positive correlations with wind speed. Aerosol scattering coefficient was highest under southeasterly wind, whereas the absorption coefficient was highest under the southwesterly wind. In the three haze pollution events, Haze 1 and Haze 2 were mainly affected by long-range transportation of pollutants. Haze 1 was mainly affected by aging air mass from north Nanjing, Haze 2 was mainly affected by biomass burning air mass from southwest Nanjing, while Haze 3 was mainly caused by the high sulfate.

An intensive study on aerosol optical properties and affecting factors in Nanjing, China.

The optical properties of aerosol as well as their impacting factors were investigated at a suburb site in Nanjing during autumn from 14 to 28 November 2012. More severe pollution was found together with lower visibility. The average scattering and absorption coefficients (Bsca and Babs) were 375.7 ± 209.5 and 41.6 ± 18.7 Mm(-1), respectively. Higher Ångström absorption and scattering exponents were attributed to the presence of more aged aerosol with smaller particles. Relative humidity (RH) was a key factor affecting aerosol extinction. High RH resulted in the impairment of visibility, with hygroscopic growth being independent of the dry extinction coefficient. The hygroscopic growth factor was 1.8 ± 1.2 with RH from 19% to 85%. Light absorption was enhanced by organic carbon (OC), elemental carbon (EC) and EC coatings, with contributions of 26%, 44% and 75% (532 nm), respectively. The Bsca and Babs increased with increasing N100 (number concentration of PM2.5 with diameter above 100 nm), PM1 surface concentration and PM2.5 mass concentration with good correlation.

[Pollution Characteristics and Light Extinction Effects of Water-soluble Ions in PM2.5 During Winter Hazy Days at North Suburban Nanjing].

To investigate the characteristics of water-soluble ions in PM2.5 and their contribution to light extinction in haze days, on-line monitoring of PM2.5. was conducted at North Suburban Nanjing from 25 January through 3 February, 2013. Water-soluble components were collected with a particle-into-liquid sampler (PILS), and analyzed by ion chromatography (IC) for the contents of SO4(2-), NO3-, NH4+, Cl-, Na+, K+, Mg2+ and Ca2+ Simultaneously particle size distributions were measured using scanning mobility particle sizer (SMPS) and Aerodynamic Particle Sizer (APS). The absorption and scattering coefficients were measured by three-wavelength photoacoustic soot spectrometer (PASS-3). Trace gases (SO2, NO2 etc.) were also monitored. The results showed that the average concentrations of total water-soluble ions were 70.3 and 22.9 microg x m(-3) in haze and normal days, respectively. Secondary hygroscopic components including SO4(2-), NO3- and NH4+ were the major ionic pollutants. Hazy days favored the conversion of SO2 and NOx, to SO4(2-) and NO3-, respectively, and in particular the oxidation of NOx. Using multiple linear regression statistical method, the empirical relationship between the dry aerosol extinction coefficient and the chemical composition was established. NH4NO3 was found to be the largest contributor to aerosol extinction in winter in Nanjing, followed by (NH4)2SO4, OC and EC. In two heavy pollution events, the increase of ion concentrations was influenced by the increase of primary emissions and secondary transformation.

[Two-photon ionization spectroscopy of methyl iodide in the region of 76 500-81 120 cm(-1)].

Using the device for ion velocity imaging, the laser frequency is doubling with the wavelength in the region of 492-523 nm, and the laser after frequency doubling was used as the light source. The ion spectrum of methyl iodide parent molecular (CH3 I+) in the range of 76 500-81 120 cm(-1) was obtained by the way of two-photon ionization, with a very high-resolution. The mechanisms of the methyl iodide molecule two-photon ionization were also described, the CH3 I+ spectrum obtained in the experiment was marked based on Rydberg formula and the quantum defect, the split arising from p series, d series and f series levels was also explained, and the spectral assignment showed that the two-photon ionization of methyl iodide molecule can not only be used to observe the reported characteristics of single photon ionization, but also can find some transitions which is forbidden in the single photon ionization, such as f series transitions.

High-speed mass analysis of whole erythrocytes by charge-detection quadrupole ion trap mass spectrometry.

Herein, we report an application of charge-detection quadrupole ion trap mass spectrometry to the measurement of total dry masses of mammalian and poultry erythrocytes evaporated/ionized by laser-induced acoustic desorption. The method is rapid and widely applicable. Eight different types of red blood cells (RBCs) have been successfully analyzed, including those of human, goat, cow, mouse, pig, and chicken. The measured mean masses (weights per corpuscle) range from 0.58 x 10(13) Da (9.6 pg) of goat RBCs to 2.80 x 10(13) Da (46.5 pg) of chicken RBCs. The total dry weights determined for human RBCs from a healthy male adult, a patient with iron-deficiency anemia, and a patient with thalassemia are 34.8, 28.8, and 20.6 pg, respectively. These weights, except that of thalassemia, are all approximately 10% higher than their corresponding mean corpuscular hemoglobin values determined by a commercial automated hematology analyzer. The mass distribution profiles of the cells are all near-Gaussian, with a standard deviation of 15% for the normal human RBCs. The deviation increases significantly to 20% for RBCs with thalassemia characteristics and 27% for RBCs with iron-deficiency anemia characteristics. All the observations are in accord with their corresponding mean corpuscular volume measurements, indicating an increase in anisocytosis (variation in RBC size) in the anemic samples. Our results suggest a broad and promising application of this new technology to high-speed mass analysis of RBCs and other biological whole cells as well.

[The study of CO2 cavity enhanced absorption and highly sensitive absorption spectroscopy].

Cavity enhanced absorption spectroscopy (CEAS) is a new spectral technology that is based on the cavity ring down absorption spectroscopy. In the present paper, a DFB encapsulation narrow line width tunable diode laser (TDL) was used as the light source. At the center output, the TDL radiation wavelength was 1.573 microm, and an optical cavity, which consisted of two high reflectivity mirrors (near 1.573 microm, the mirror reflectivity was about 0.994%), was used as a sample cell. A wavemeter was used to record the accurate frequency of the laser radiation. In the experiment, the method of scanning the optical cavity to change the cavity mode was used, when the laser frequency was coincident with one of the cavity mode; the laser radiation was coupled into the optical cavity and the detector could receive the light signals that escaped the optical cavity. As a result, the absorption spectrum of carbon dioxide weak absorption at low pressure was obtained with an absorption intensity of 1.816 x 10(-23) cm(-1) x (molecule x cm(-2)(-1) in a sample cell with a length of only 33.5 cm. An absorption sensitivity of about 3.62 x 10(-7) cm(-1) has been achieved. The experiment result indicated that the cavity enhanced absorption spectroscopy has the advantage of high sensivity, simple experimental setup, and easy operation.