Original Intensity Research Articles

Quantitative evaluation of intensity fidelity of super-resolution reconstruction for structured illumination microscopy

Super-resolution structured illumination microscopy (SR-SIM) relies heavily on post-processing reconstruction to obtain high-quality SR images from raw data. Although many SIM reconstruction algorithms have been developed to recover fine cellular structures with high fidelity even from the noisy data, whether the pixel intensities of reconstructed SR images are still proportional to the original fluorescence intensity has been less explored. The linearity between the intensity before and after reconstruction is defined as the intensity fidelity. Here, we proposed a method to evaluate the reconstructed SR image intensity fidelity at different spatial frequencies. With the proposed metric, we systematically investigated the impact of the key factors on the intensity fidelity in the standard Wiener-SIM reconstructions with simulated data, then evaluated the intensity fidelity of the SR images reconstructed by representative open-source packages. Our work provides a reference for SR-SIM image intensity fidelity improvement.

Stable random laser of perovskite quantum dots based on SiO2-QDs-SiO2 composite nanostructure

In recent years, metal halide perovskite has gradually become a hotspot in the field of optoelectronics. However, the inherent instability of CsPbX3 quantum dots (QDs) seriously affects the amplified spontaneous emission (ASE) or lasing performance. Herein, the highly stable CsPbBr3 random laser is realized in SiO2-QDs-SiO2 (SQS) composite nanostructure doped with Ag nanoislands. The strong scattering generated by SQS composite nanostructure and the localized surface plasmon resonance (LSPR) of metal silver nanoislands provide optical feedback for the formation of random laser. Then a coherent random laser with low threshold (∼2.2 mJ/cm2) is obtained. SiO2 microspheres anchor QDs to avoid photoinduced regeneration and fluorescence quenching caused by QDs clusters. The inner QDs of SQS are effectively protected from water erosion, thus resulting that the samples have higher water resistance. The luminescence intensity still maintains 70 % of the original intensity after 40 days with the addition of pure water. Our research provides an effective method for improving the water stability of perovskite QDs. The highly stable random laser based on perovskite quantum dot film has a wide application prospect in integrated optoelectronics, display imaging and sensing measurement.

Averaging fractional Fourier domains for background noise removal applied to digital lensless holographic microscopy

A background noise removal method based on averaging fractional Fourier domains is presented. The method is applied to Digital Lensless Holographic Microscopy (DLHM) intensity reconstructions, where the background is perturbed by the weak yet detrimental presence of information of the twin image. A set of fractional Fourier domains of a DLHM intensity reconstruction is computed and thereafter averaged leading to a sensible reduction of the background noise and, therefore, an increase in the overall contrast of the resulting image. The maximum reach of the fractional rotations used in the method is determined by measuring the spatial resolution in a regular star test target such that the spatial resolution is kept within the span of interest for a given application. The set of images to be averaged is composed of fractional rotations of the original intensity reconstruction that are smaller than the previously determined maximum reach. The number of fractional rotations that are finally averaged is determined by the sought increase in the contrast of the resulting image. Experimental samples of micrometer-sized objects and an intricate biological specimen have been used to validate the proposal.

Classification method of seabed sonar image substrate based on ELM-AdaBoost

The results of sediment classification are affected by the measurement environment. The water depth has a significant impact on the sound propagation, and the acoustic characteristics will be different under different water depths. In addition, seabed topography, sediment types and their distribution, acoustic frequency, equipment types and settings, and suspended substances in water will all affect the original sonar data. In order to obtain accurate classification results, a seabed sonar image classification method based on Elm AdaBoost is proposed. The original sound intensity data is compensated for gain and the anomaly is eliminated. After preprocessing the multi beam sonar data, the image texture feature is extracted from the gray level co-occurrence matrix as the feature vector for classification, and the elm classifier is constructed. The elm is enhanced by AdaBoost. The calculated feature is input into the elm AdaBoost network for sediment classification, and the result is output. Simulation results show that the proposed method effectively improves the accuracy of sediment classification, and verifies the feasibility of this method.

Crystal field optimization, luminescence enhancement and thermal stability of novel K2NaAl0.4Ga0.6F6:Mn4+ solid solution red phosphor for high-performance warm WLED

Mn4+-doped fluoride phosphors have important application value in the background light and WLED lighting fields. Therefore, the synthesis of efficient and stable Mn4+-doped red phosphor is of great application value. In this study, a series of red-emitting K2NaAl1-yGayF6:xMn4+ (y = 0, 0.2, 0.4, 0.6, 0.8 and 1) (x = 0.01, 0.03, 0.05, 0.07 and 0.09) solid solution phosphors are successfully synthesized by simple coprecipitation method. The synthesis strategy of simple crystal structure optimization is proposed to realize simultaneously the crystal field optimization, luminescence enhancement and thermal stability of red phosphor. The calculation and theoretical analysis of crystal field strength are used to prove that solid solution matrix K2NaAl0.4Ga0.6F6 is the most ideal matrix material. X-ray powder diffraction, energy-dispersive X-ray spectrometer and scanning electron microscope are employed to determine the crystal structure, composition and morphology of all samples. Optical properties are characterized using excitation spectra, emission spectra and fluorescence lifetime curves. Moreover, the CIE coordinates of red-light show that the phosphor has low correlated color temperature and excellent color purity. Intriguingly, the as-prepared K2NaAl0.4Ga0.6F6:Mn4+ phosphor possesses admirable thermal quenching behavior and color stability at high temperature. At a temperature of 423 K, the photoluminescence intensity can be maintained at 52 % of the original intensity (298 K). The activation energy, the chromaticity shift and chromaticity coordinate variation are also systematically calculated. More importantly, A high-performance warm WLED with low correlated color temperature (CCT = 3982 K) and high color rendering index (Ra = 93.7) is achieved by using K2NaAl0.4Ga0.6F6:Mn4+ as a red-emitting material. These results demonstrate that K2NaAl0.4Ga0.6F6:Mn4+ red phosphor provides a novel choice for the warm WLED required for indoor lighting.

Energy transfer and color tunability in high-thermal-stability Dy3+/Tb3+ co-doped K3YF6 transparent oxyfluoride glass ceramics

The production process and comprehensive analysis of the co-doping of Dy3+ and Tb3+ in K3YF6 oxyfluoride glass-ceramics (GCs) are delved. The primary focus is on investigating the luminescent properties and energy transfer (ET) mechanisms within these systems. The embedding of well-formed K3YF6 nanocrystals within the matrix was verified through detailed analyses using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fine-tuning the Tb3+ concentration facilitated the achievement of tunable emission, ranging from a subtle yellow to a yellowish green hue, demonstrating the remarkable flexibility in color manipulation. Fluorescence analysis unmistakably demonstrates the occurrence of energy transfer occurring between Dy3+ and Tb3+ ions, attaining a peak energy transfer efficiency of 51.33 %. Additional analysis applying Dexter's energy transfer formula affirms that the fundamental mechanism of energy transfer between Dy3+ and Tb3+ ions is dipole-dipole interaction. The K3YF6 glass ceramics (GCs) incorporating Dy3+/Tb3+ nanocrystals exhibit a remarkable thermal stability, retaining 89.07 % of their original relative emission intensity at 423 K when stimulated by 350 nm light. These findings indicate that Dy3+/Tb3+ co-doped K3YF6 GCs hold significant potential in solid state lighting, positioning them as a candidate for future lighting.

Evaluation of the use of polyvinyl alcohol in the manufacture of pressed samples for X-ray fluorescence analysis

The reliability of the results of X-ray fluorescence analysis (XRF), which is widely used in determination of the elemental composition of various materials, largely depends on the quality of sample preparation. When producing pressed tablets for X-ray fluorescence analysis of trace elements, a binder is often used in a powder form, which requires significant time for thorough homogenization. We present the results of applicating a polyvinyl alcohol solution as a binder in the manufacture of pressed samples without using a substrate in determination of microelements by XRF. The parameters for obtaining a durable tablet with a homogeneous composition that matches the condition of minimum impact on the intensity of the analytical lines of the elements being determined are presented. It is shown that the optimal sample weight for the proposed method of producing pressed tablets is 7 g with the addition of polyvinyl alcohol in a ratio of 7:1, the optimal drying time for the tablet after pressing is 1 hour. The calculated variation coefficients of the analytical signal (<2%) indicate the homogeneity of the produced tablets. The maximum values of standard deviations of pressed tablets for the selected ranges of elements are much less than acceptable, which confirms the validity of the proposed method of sample preparation. It is also shown that during long-term storage and repeated measurements, pressed tablets with the polyvinyl alcohol solution retain their original structure and intensity of analytical lines of elements. The accuracy of measurements in the subsequent determination of rock-forming elements is consistent with their certified contents. The results obtained can be used to reduce the time spent on getting a representative pressed sample when using polyvinyl alcohol, determining elements without additional support (coating films), microelement and silicate analyzes from one sample.

An Exploratory Study of Alternative Time Frames and Descriptors for EQ-5D-5L in Obstructive Airway Diseases Using Mixed Methods

ObjectivesEQ-5D-5L with its recall time of “today” may limit its ability to capture episodic symptoms and exacerbations in chronic obstructive airway diseases (OAD). We examined whether longer time frames and changing the intensity response scales to frequency scales could improve the measurement properties of EQ-5D-5L. MethodsWe used a mixed-method design starting with in-depth interviews with 20 patients and clinicians to elicit preferred time frames using concept elicitation techniques and content analyses. We then administered the top 4 preferred variants using 1- and 4-weeks’ time frames with the original intensity or an alternative frequency response scale alongside EQ-5D-5L and St George Respiratory Questionnaire to OAD patients during 2 different visits. We compared the ceiling effects and construct validity by testing a priori hypotheses in relation to St George Respiratory Questionnaire and clinical outcomes via correlation and receiver operating characteristic (ROC) analyses, respectively. Follow-up patients were categorized into “better,” “stable,” and “worse” groups to assess reliability using intraclass correlation coefficient (ICC) or Cohen’s Kappa (k) and responsiveness using ROC analysis. ResultsA total of 184 patients (mean [SD] age: 54[18]; female: 37.0%) completed baseline assessments. A total of 120 patients also completed follow-up assessments (mean [SD] interval: 2.8 [1.7] months). The ceilings were lower in the variants compared with EQ-5D-5L (P < .001). Reliability of the variants were comparable to or higher than EQ-5D-5L. The c-statistic values derived from ROC analyses of the variants were consistently higher than EQ-5D-5L. ConclusionsUse of longer time frames with the original intensity or the frequency response scales may improve EQ-5D-5L’s psychometric properties in OAD patients.

Deblurring of Beamformed Images in the Ocean Acoustic Waveguide Using Deep Learning-Based Deconvolution

A horizontal towed linear coherent hydrophone array is often employed to estimate the spatial intensity distribution of incident plane waves scattered from the geological and biological features in an ocean acoustic waveguide using conventional beamforming. However, due to the physical limitations of the array aperture, the spatial resolution after conventional beamforming is often limited by the fat main lobe and the high sidelobes. Here, we propose a method originated from computer vision deblurring based on deep learning to enhance the spatial resolution of beamformed images. The effect of image blurring after conventional beamforming can be considered a convolution of beam pattern, which acts as a point spread function (PSF), and the original spatial intensity distributions of incident plane waves. A modified U-Net-like network is trained on a simulated dataset. The instantaneous acoustic complex amplitude is assumed following circular complex Gaussian random (CCGR) statistics. Both synthetic data and experimental data collected from the South China Sea Experiment in 2021 are used to illustrate the effectiveness of this approach, showing a maximum 700% reduction in a 3 dB width over conventional beamforming. A lower normalized mean square error (NMSE) is provided compared with other deconvolution-based algorithms, such as the Richardson–Lucy algorithm and the approximate likelihood model-based deconvolution algorithm. The method is applicable in various acoustic imaging applications that employ linear coherent hydrophone arrays with one-dimensional conventional beamforming, such as ocean acoustic waveguide remote sensing (OAWRS).

Monolayer graphene oxide-Au loaded compound (GO-Au) as a flexible, stable and sensitive SERS active substrate for detection of stonehouse clam toxin (STX)

Stonehouse clam toxin (STX) is a prevalent neuroparalytic toxin found among shellfish toxins. When consumed by humans, it disrupts neuronal conduction, potentially leading to quadriplegia, headache, shock, and even respiratory failure-induced death. This study introduces a highly sensitive and specific method for detecting shellfish toxins. The approach involves utilizing graphene gold-loaded compounds alongside stone house clam toxin aptamers and their complementary chains. The layered structure of graphene creates numerous hot spots among nanoparticles, while its arched spatial configuration offers an enhanced specific surface area, resulting in improved Surface-Enhanced Raman Scattering (SERS). By combining the signaling molecule Bodipy R6G-modified Apt with GO-Au loading compounds, distinctive Raman characteristic peaks emerge. Due to the strong affinity between Apt and STX, the Apt carrying the signaling molecule migrates away from the SERS aptamer probe's surface, thereby attenuating the original SERS signal intensity and facilitating ultra-sensitive shellfish toxin detection. The detection limit for the toxin was determined to be 5.47 nM, with a recovery rate ranging from 97.60 % to 108.32 %, affirming the applicability of this design for quantitative and specific shellfish toxin detection, signifying its considerable practical significance.

Suppressing random noise in seismic signals using wavelet thresholding based on improved chaotic fruit fly optimization

Suppressing random noise in seismic signals is an important issue in research on processing seismic data. Such data are difficult to interpret because seismic signals usually contain a large amount of random noise. While denoising can be used to reduce noise, most denoising methods require the prior estimation of the threshold of the signals to handle random noise, which makes it difficult to ensure optimal results. In this paper, we propose a wavelet threshold-based method of denoising that uses the improved chaotic fruit fly optimization algorithm. Our method of selects uses generalized cross-validation as the objective function for threshold selection. This objective function is optimized by introducing an adjustment coefficient to the chaotic fruit fly optimization algorithm, and the optimal wavelet threshold can then be obtained without any prior information. We conducted denoising tests by using synthetic seismic records and empirical seismic data acquired from the field. We added three types of noise, with different average signal-to-noise ratios, to synthetic seismograms containing noise with original intensities of − 5, − 1, and 4 dB, respectively. The results showed that after denoising, the signal-to-noise ratios of the three types of noise increased to 7.12, 10.04, and 14.26, while the mean-squared errors in the results of the proposed algorithm decreased to 0.006, 0.0031, and 0.0012, respectively.

Ternary Eu3+ crystalline complexes with photoluminescence and triboluminescence for dynamic stress visualization

Investigation of photoluminescence (PL) and fracture-induced triboluminescence (TL) is necessary for the development of both fundamental theories and practical applications in mechanical energy conversion; however, most known PL/TL-emitting materials are confined to inorganic systems. In this study, a novel lanthanide-based crystalline complex (LnCC), Eu(DBM)3DETA was synthesized via the synergistic coordination of Eu3+ with DBM (Dibenzoylmethane) and DETA (Diethylenetriamine) units, leading to the formation of brighter LnCC with bright red emission, high PL quantum yields (57.19 %) and unique TL characteristics. The key to success in obtaining Eu(DBM)3DETA is the utilization of DETA molecule as synergistic ligand, presenting block crystals with higher coordination number of Eu3+ ions via recrystallization. Due to the dense accumulation of cross-linked three-dimensional frameworks through van der Waals interactions, the fracture-induced piezoelectric effect results in charge separation and excitation through the resultant electric field and discharge, triggering a fast TL response of Eu(DBM)3DETA and expanding the possibilities of the quantitative stress sensing. Importantly, amorphous powders can still recover to their original PL and TL emission intensities after recrystallization in cyclic crystal-to-amorphous phase transitions. The unique PL and TL characteristics of Eu(DBM)3DETA provide promising opportunities to display stress visualization differences of electronic signatures under different forces.

Seismic intensity measures and predictive equations for the evaluation of earthquake—induced crest settlements of earth dams

AbstractIn this paper the results of 2D dynamic finite element analyses of a zoned earth dam are presented and discussed with the aim of detecting proper intensity measures able to describe the variation of the crest permanent settlement with the characteristics of the input ground motion. A large set of horizontal components of earthquake records has been selected and used as input motion considering both upstream and downstream directions. This allowed to explore the activation of plastic mechanisms in the dam embankment and the amplification of the horizontal accelerations. Starting from the analysis results, two original intensity measures, related to the amplitude, energy and frequency content of the input motion, have been detected and original empirical predictive formulas have also been derived to estimate the permanent crest settlement of the dam. The effectiveness of the proposed intensity measures and the reliability of the novel relationships between these intensity measures and earthquake‐induced permanent crest settlements have been checked against (i) numerical results of further dynamic analyses carried out for the same dam using additional sets of input motions, (ii) numerical results available in the literature for two other earth dams and (iii) field data relative to the crest settlements induced in four earth dams by two recent large earthquakes. The whole set of analysis results allowed defining an empirical equation that appears as a promising general predictive tool for the earthquake‐induced crest settlement of earth dams.

Color-tunability and energy transfer of a highly thermal-stable BaZnB4O8:Tb3+/Eu3+ phosphor for single-component w-LEDs

A series of Tb3+ single-doped and Tb3+/Eu3+ co-doped BaZnB4O8 samples with color tuning were efficiently synthesized using the solid-state reaction method. The crystal structure, photoluminescence and the energy transfer process (ET) of the samples were systematically studied. The optimal BaZnB4O8:0.08Tb3+ sample shows efficient green emission, then tunable color was achieved by merely introducing a few of Eu3+ ions owing to the highly efficient ET process from Tb3+ to Eu3+ in the BaZnB4O8:0.08Tb3+/yEu3+ samples. The ET efficiency from Tb3+ to Eu3+ of the BaZnB4O8:0.08Tb3+, yEu3+ samples rose from 32.1 % to 51.6 %, simultaneously the luminescent quantum yield improved from 24.7 % to 36.8 %, as the Eu3+ doping concentration increased from 0.125 % to 2 %. Moreover, the Tb3+/Eu3+ co-doped samples exhibited great thermal stability, keeping about 90.2 % (@150 °C) of their original intensity at room temperature. Finally, white light was achieved by a warm w-LEDs fabricated by coating the BaZnB4O8:0.08Tb3+, 0.0025Eu3+ sample on a 365 nm chip. The w-LEDs showed outstanding performance characteristics, with a CCT of 3869 K and a CRI of 89.3. According to the results, Tb3+/Eu3+ co-doped BaZnB4O8 samples have the potential to serve as single-component multicolor-emitting or white-emitting phosphors upon excitation at near-UV wavelength.

A metal-organic framework and quantum dot-based ratiometric fluorescent probe for the detection of formaldehyde in food.

Agreen and sensitive ratio fluorescence strategy was proposed for the detection of formaldehyde (FA) in food based on a kind of metal-organic frameworks (MOFs), MIL-53(Fe)-NO2, and nitrogen-doped Ti3C2 MXene quantum dots (N-Ti3C2 MQDs) with a blue fluorescence at 450nm. As a type of MOFs with oxidase-like activity, MIL-53(Fe)-NO2 can catalyze o-phenylenediamine (OPD) into yellow fluorescent product 2,3-diaminophenazine (DAP) with a fluorescent emission at 560nm. DAP has the ability to suppress the blue light of N-Ti3C2 MQDs due to inner filter effect (IFE). Nevertheless, Schiff base reaction can occur between FA and OPD, inhibiting DAP production. This results in a weakening of the IFE which reverses the original fluorescence color and intensity of DAP and N-Ti3C2 MQDs. So, the ratio of fluorescence intensity detected at respective 450nm and 560nm was designed as the readout signal to detect FA in food. The linear range of FA detection was 1-200µM, with a limit of detection of 0.49µM. The method developedwas successfully used to detect FA in food with satisfactory results. It indicates that MIL-53(Fe)-NO2, OPD, and N-Ti3C2 MQDs (MON) system constructed by integrating the mimics enzyme, enzyme substrate, and fluorescent quantum dots has potential application for FA detection in practical samples.

Ce3+-Activated SrLu2Al3ScSiO12 Cyan-Green-Emitting Garnet-Structured Inorganic Phosphor Materials toward Application in Blue-Chip-Based Phosphor-Converted Solid-State White Lighting.

Phosphor-converted white-light-emitting diodes (WLEDs) with superhigh color rendering index (CRI) are the ongoing pursuit of next-generation solid-state lighting. One of the most important challenges is the limited improvement in CRI on account of the absence of a cyan component in the typical commercial combination. Here, a bright broad-band cyan-green-emitting phosphor with cubic garnet structure, SrLu2Al3ScSiO12:Ce3+ (SLASSO:Ce3+), was successfully reported, which can compensate for the absence of cyan cavity in the 480-520 nm blue-green emission region. With 439 nm blue-light irradiation, the as-fabricated SLASSO:Ce3+ phosphor yields a broad-band cyan-green emission with the maximum emission peak positioned at 525 nm and an appropriate full width at half-maximum (fwhm) of 111 nm, capable of providing more cyan emission component without sacrificing green emission. Meanwhile, the optimal SLASSO:2%Ce3+ phosphor features CIE color coordinates of (0.3254, 0.5470) with cyan-green hue, along with a high internal quantum efficiency of up to 93%. Additionally, thermal stability measurements at different temperatures reveal that the luminescence emission intensity of the proposed phosphor retains 44% of its original integral emission intensity at 423 K with respect to room temperature, while also demonstrating an excellent color stability (ΔE = 5.4 × 10-3). This work shows that the highly efficient SLASSO:Ce3+ garnet phosphor can be utilized as a potential cyan-green-emitting phosphor for filling the cyan gap, resulting in the construction of a high-quality warm WLED with high CRI for "human-centric" sunlight-like full-spectrum solid-state illumination.

Tunable broadband near-infrared emission from environmentally friendly Fe3+-activated lead-free perovskites for spectral analysis and rapid nighttime recognition

With the increasing role of near-infrared (NIR) light sources in many fields such as food and industry, NIR emitting phosphors have flourished in recent years. In addition to the widely reported Cr3+-activated NIR phosphors, environmentally friendly Fe3+ can also produce tunable broadband NIR spectra, which are expected to enrich the next generation of intelligent NIR light sources. In this work, a series of Fe3+-activated perovskite-type Sr2ScSbO6 (SSSO) NIR phosphors were successfully prepared and an emission wavelength of 900 nm with a full width at half maximum (FWHM) of 110 nm was obtained. Through the crystal field engineering strategy, the lattice site of Sr2+ was completely replaced by Ba2+ and Ca2+ to obtain Ba2ScSbO6 (BSSO) and Ca2ScSbO6 (CSSO), and the emission peak was continuously adjusted from 840 nm to 950 nm. When the temperature increased from 300 K to 400 K, BSSO:Fe3+, SSSO:Fe3+ and CSSO:Fe3+ could maintain 69 %, 82 % and 67 % of the original luminescence intensity, respectively. The opposite crystal field dependence between Fe3+ and Cr3+ was shown in double-layer perovskite-type antimonate materials, which could guide us to develop Fe3+-activated long-wavelength emission NIR phosphors. Benefiting from the long-wavelength emission of BSSO:Fe3+, SSSO:Fe3+, and CSSO:Fe3+, their application potential in the field of spectral analysis and rapid nighttime recognition were successfully demonstrated.

A study of polylactic Acid/K2SiF6:Mn4+ composite luminescent materials: design, preparation, and properties

K2SiF6:Mn4+ (KSF) has been the most representative red emitting fluoride phosphors thanks to its cheap production cost and excellent luminescence properties. Nevertheless, the photoluminescent properties of this phosphor are limited due to intrinsically poor water resistance. In this work, constructing composite luminescent materials by blending KSF with polylactic acid (PLA) polymer was developed using the melt mixing process. The tactic not only makes full use of the photoluminescent properties of KSF, but also enhances the moisture resistance ability by alleviating or suppressing hydrolysis. The photoluminescent spectra, temperature-dependence emitting spectra, scanning electron microscopy, thermogravimetric analysis, and wide-angle x-ray scattering were conducted to study the morphology, thermal stability and photoluminescent properties of the KSF@PLA composite luminescent materials. KSF was evenly distributed in PLA. Furthermore, the influence of the doping amount of KSF on the structure and properties of PLA was systematically studied and the optimal doping amount of KSF in PLA was determined to be 10%, marked as KSF@PLA 3. Finally, KSF@PLA 3 exhibited excellent moisture resistance ability and thermal stability. After soaking in deionized water for 7 days, the emission intensity of KSF@PLA 3 is almost consistent with the original emission intensity.

A Novel Feature Engineering Method Based on Latent Representation Learning for Radiomics: Application in NSCLC Subtype Classification.

Radiomics refers to the high-throughput extraction of quantitative features from medical images, and is widely used to construct machine learning models for the prediction of clinical outcomes, while feature engineering is the most important work in radiomics. However, current feature engineering methods fail to fully and effectively utilize the heterogeneity of features when dealing with different kinds of radiomics features. In this work, latent representation learning is first presented as a novel feature engineering approach to reconstruct a set of latent space features from original shape, intensity and texture features. This proposed method projects features into a subspace called latent space, in which the latent space features are obtained by minimizing a unique hybrid loss function including a clustering-like loss and a reconstruction loss. The former one ensures the separability among each class while the latter one narrows the gap between the original features and latent space features. Experiments were performed on a multi-center non-small cell lung cancer (NSCLC) subtype classification dataset from 8 international open databases. Results showed that compared with four traditional feature engineering methods (baseline, PCA, Lasso and L2,1-norm minimization), latent representation learning could significantly improve the classification performance of various machine learning classifiers on the independent test set (all p<0.001). Further on two additional test sets, latent representation learning also showed a significant improvement in generalization performance. Our research shows that latent representation learning is a more effective feature engineering method, which has the potential to be used as a general technology in a wide range of radiomics researches.

ПОШИРЕННЯ ТЕРАГЕРЦОВИХ ВИХРОВИХ ЛАЗЕРНИХ ПУЧКІВ У ВІЛЬНОМУ ПРОСТОРІ

Subject and Purpose. Currently, numerous ideas and different methods have been in growth for generating vortex beams — areas of the circular motion of the electromagnetic wave energy flow around the so-called phase singularity points caused by a violation of the wave front topological structure. The purpose of this work is to obtain analytical expressions describing the nonparaxial diffraction of wave modes of the waveguide resonator of a terahertz laser during the wave mode interaction with a spiral phase plate. The resulting vortex beams are examined for their physical features in free space propagation. Methods and Methodology. The Rayleigh-Sommerfeld vector theory is adopted to consider the propagation of vortex laser beams generated by wave modes of the quasi-optical waveguide cavity when interacting with a spiral phase plate in different diffraction zones. Results. For the first time, analytical expressions have been obtained to describe the nonparaxial diffraction of wave modes of the waveguide resonator of a terahertz laser, when resonator modes interact with a spiral phase plate at different topological charges, n. The physical features of the resulting vortex beams were studied in their free space propagation. It has been shown that a spiral phase plate modifies the structure of the linearly polarized EH₁₁ mode so that the original (n=0) intensity profile with the maximum energy at the center turns at n=1 and 2 into a ring-like donut shape with an energy hole in the center. The azimuthally polarized TE₀₁ mode has originally (n=0) a ring-shaped intensity. At n=1, this configuration changes to have the maximum intensity in the center. At n=2, it becomes annular again. In the process, the spherical phase front of the beam of the linearly polarized EH₁₁ mode becomes spiral and have one singularity point on the axis, whereas the phase structure of the azimuthally polarized TE₀₁ mode gains a region with two phase singularity points off the axis. Conclusions. The results of the study can effectively facilitate information transfer in high-speed THz communication systems. They can provide a real platform to perform tasks related to tomography, exploring properties of materials, detecting astrophysical sources, which makes them very promising in modern technologies.