Polar Transformation Research Articles

Stereo Jones Matrix Holography with Longitudinal Polarization Transformation

AbstractMetasurfaces have exhibited powerful abilities for manipulating multiple fundamental properties of light including amplitude, phase, polarization, and so on. However, these strategies are commonly concentrated on the modulations at a single transverse plane of output light. The spatial evolutions of these properties, especially the polarizations along longitudinal direction, are rarely investigated. Here, a stereo Jones matrix holography method is presented for understanding the spatial evolution including polarization, amplitude, and phase variations along the longitudinal direction. Stereo holographic algorithms in matrix framework are developed to generate multiplane and even continuously varied vectorial holographic images that exhibit distinct polarization states at each transverse plane. This method provides a benchmark of longitudinal polarization transformations as well as beam modulations by simply using a single planar metasurface without extra burdens on optical path. In addition, the obtained propagation‐dependent features can favor the realizing of on‐demand transverse and longitudinal spatial evolution from the perspective of the holographic method. Furthermore, it may also promote the development of related areas including polarization‐switchable devices, optical trapping, microscopy, laser processing, etc.

An intelligent vision recognition method based on deep learning for pointer meters

Nowadays, pointer instruments remain the main state monitoring devices in the power industry, because they have strong mechanical stability to resist electromagnetic interferences compared with digital instruments. Although the object detection algorithms based on deep learning have widely been used in the field of instrument detection, the meter recognition process still relies on threshold segmentation to recognize object points and on Hough transform to extract the meter pointer. An intelligent vision recognition method based on YOLOv5 and U2-Net network (YLU2-Net) is proposed to improve the accuracy and efficiency of meter recognition in a complex environment. Firstly, the pointer meter is located in the instrument images by using the YOLOv5 network as a region of interest (RoI). Then, the instrument RoI is processed by means of perspective transformation and image resizing. Thirdly, an improved U2-Net image segmentation method with the deep separable convolution and the focal loss function is devised to distinguish the pointers and scales from the background in the instrument RoI. Further, a dimension reduction reading method with the polar coordinate transformation is developed to calculate the meter reading accurately and efficiently. Finally, the ablation experiment is conducted to test the performance of each algorithm module in our method, and the competition experiment is completed to compare our method with other state-of-the-art ones. The experimental results verify the accuracy and efficiency of the YLU2-Net recognition method proposed.

Sustainable and cleaner approach for paraffin wax treatment via CO2-induced polarity transformation of switchable solvents

Paraffin wax has caused obvious detrimental consequences to the extraction for fossil fuels, and posed environmental challenge due to the absence of cleaner methods for paraffin wax removal. A cleaner and sustainable approach for paraffin wax removal was developed using the switchable polarity solvents (SPS). Three SPS with low polarity, including dipropylamine (DPA), ethylbutylamine (EBA), and dibutylamine (DNBA) were selected for paraffin wax removal. Compared with bubbling CO2 into SPS straightway, the transformation of the polarity quantified by normalized polarity energy confirms the addition of water is benefit to enlarge the polarity scope. Paraffin wax is removed at the initial state and separated at the final state by CO2-induced polarity transformation of SPS. The dissolution rates for paraffin wax of DPA and EBA reached 0.071 g/min and 0.062 g/min, which surpassed that of traditional solvents, such as o-xylene (0.045 g/min) and Petroleum ether (0.017 g/min), indicating that these selected SPS is suitable for paraffin wax removal. The paraffin wax dissolution behaviors of SPS can be accurately matched using modified Apelblat models with root-mean-square deviation of 1.085%. With the addition of water, more than 99% of paraffin wax is separated from DPA and EBA by introducing CO2 within 10mins, which is a better alternative method for energy-intensive distillation process. The introduction of water is indispensable for improving the separation efficiency, since it enlarged the polarity difference between solvents and paraffin wax. The thermal behavior of separated paraffin wax detected by Differential Scanning Calorimetry remained steady, and there were negligible residual solvents detected indicate the feasible separation of paraffin wax. Both SPS and water are recovered upon N2/80 °C, which retain good recyclability for paraffin wax removal. These findings confirms the applicability of SPS in the sustainable and cleaner removal of paraffin wax. The use of SPS provides an alternative and promising approach for paraffin wax removal for ensuring the demands of low-energy consumption and environment.

Optical character correction of large-curvature annular sector text in polar coordinate system

Optical character recognition (OCR) of complex morphologies represented by large-curvature annular sector text (AST) is a very challenging task. A three-segment text recognition framework consisting of detection, correction and recognition is currently an effective method for dealing with complex morphological OCR. Optical character correction (OCC) is a key component in processing largecurvature AST. This paper proposes an OCC method in the polar coordinate system, which consists of control point preprocessing, polar coordinate transformation, and image remapping. The control point preprocessing is used to normalize the control points of the large curvature AST region; the polar coordinate transformation is to convert the pixels in the rectangular coordinate system to the polar coordinate system; image remapping maps the original image in polar coordinate system to polar coordinate space for re-representation. The method proposed in this paper can be used in conjunction with most detection and recognition modules and is applicable to any language type. Furthermore, the correction process consumes very little computational resources and has little impact on the speed of text detection and recognition. Experimental results show that the proposed method outperforms state-of-the-art algorithms in large curvature AST correction and recognition experiments

Real-time monitoring of polarization state deviations with dielectric metasurfaces

We propose and experimentally demonstrate a dielectric metasurface that allows monitoring of polarization deviations from an arbitrary elliptical input anchor state simply by tracking in real-time the output ratio between the powers of horizontal and vertical components after the metasurface. Importantly, this ratio can be enhanced corresponding to increased responsivity. Such nontrivial functionality is achieved by designing binary metasurfaces that realize tailored nonunitary and chiral polarization transformation. We experimentally demonstrate the operation at telecommunication wavelengths with enhanced responsivity up to 25 for various anchor states, including the strongly elliptical and circular. We also achieve the uncertainty of deviation measurement that is significantly better than the fundamental limit for nonchiral metasurfaces.

Különböző felbontású domborzatmodellek befolyása vulkáni salakkúpok morfometriai paramétereire – összehasonlító tanulmány

Since the early 2000s, rapidly improving resolution digital terrain models (DTMs) have been used increasingly as input data in various geomorphometric studies. They are excellent for studying large areas, clusters, and geomorphological forms, and with their help, it is not difficult to analyse hundreds of forms. A common problem in the statistical evaluation of DTMs is that the results may depend on the resolution of the input data. My aim in this study was to examine one of the simplest volcanic forms, the cinder cones, from a geomorphometric point of view and to show the extent to which the result was affected by the different resolutions of the DTMs. The study areas were the San Francisco Volcanic Field (SRTM DTM resolutions 30 and 10 m) in Arizona (USA) and ChaĒne des Puys (LiDAR DTM resolutions 90 and 0.5 m) in Auvergne (France). Polar coordinate transformation (PCT) was used, descriptive parameters (cone height and average slope) were calculated, and a comparison was carried out (with the help of the Mann-Whitney test) to show statistically significant differences for age groups and values derived from different resolutions. The slope values are the most sensitive to the resolution of the input data: comparing the age groups with themselves, but with values calculated from DTM with different resolutions, the slope shows a statistically significant difference in almost all cases. Based on the tests, an ideal resolution for scoria cone morphometric examination should be at least 10 meters, but if it is an area that contains older, smaller cones, a better resolution is a better choice. On the other hand, the 0.5 meters seems unnecessary for symmetry/parameter tests.

Glioma-derived LRIG3 interacts with NETO2 in tumor-associated macrophages to modulate microenvironment and suppress tumor growth

Tumor-associated macrophages (TAMs) account for 30–50% of glioma microenvironment. The interaction between glioma tumor cells and TAMs can promote tumor progression, but the intrinsic mechanisms remain unclear. Herein, we reported that soluble LRIG3 (sLRIG3) derived from glioma tumor cells can block the M2 polarization of TAMs via interacting with NETO2, thus suppressing GBM malignant progression. The expression or activity of ADAM17 in glioma cells was positively correlated with the expression of sLRIG3 in cell supernatant. Soluble LRIG3 can suppress the M2-like polarity transformation of TAMs and inhibit the growth of tumor. High expression of LRIG3 predicts a good prognosis in patients with glioma. Mass spectrometry and Co-immunoprecipitation showed that sLRIG3 interacts with the CUB1 domain of NETO2 in TAMs. Silencing or knockout of NETO2 could block the effect of sLRIG3, which inhibited the M2-like polarity transformation of TAMs and promoted GBM tumor growth. However, overexpressing His-target NETO2 with CUB1 deletion mutation does not fully recover the suppressive effects of sLRIG3 on the TAM M2-polarization in NETO2-Knockout TAMs. Our study revealed vital molecular crosstalk between GBM tumor cells and TAMs. Glioma cells mediated the M2 polarization of TAM through the sLRIG3-NETO2 pathway and inhibited the progression of GBM, suggesting that sLRIG3-NETO2 may be a potential target for GBM treatment.

Dynamics of Aqueous Electrolyte Solutions: Challenges for Simulations

This Perspective article focuses on recent simulation work on the dynamics of aqueous electrolytes. It is well-established that full-charge, nonpolarizable models for water and ions generally predict solution dynamics that are too slow in comparison to experiments. Models with reduced (scaled) charges do better for solution diffusivities and viscosities but encounter issues describing other dynamic phenomena such as nucleation rates of crystals from solution. Polarizable models show promise, especially when appropriately parametrized, but may still miss important physical effects such as charge transfer. First-principles calculations are starting to emerge for these properties that are in principle able to capture polarization, charge transfer, and chemical transformations in solution. While direct ab initio simulations are still too slow for simulations of large systems over long time scales, machine-learning models trained on appropriate first-principles data show significant promise for accurate and transferable modeling of electrolyte solution dynamics.

Coherent control of polarization transformation of Bloch surface waves

The coherent excitation of optical device through the interference effect of multiple beam provides a practical way to enhance the degree of real-time control of the optical response of device. In this work, the coherent control of polarization transformation of Bloch surface wave supported by dielectric multilayer is studied. The grooves are introduced into the top layer of the dielectric multilayer to achieve the polarization transformations of Bloch surface wave. Two coherent beams of Bloch surface waves are incident on the grooves from the left side and the right side of the structure, respectively. The polarization transformation efficiency of Bloch surface wave can be controlled in real time by designing the phase difference of polarization transformation coefficients and the phase delay of the incident coherent beams. Moreover, the output ports of polarization transformation of Bloch surface waves can be selectively excited. By using the proposed method, the controllable port transmission of Bloch surface wave related polarization component can be achieved. In this work, the design of phase difference from the polarization transformation coefficients is achieved by changing the separation distance of grooves. The predicted polarization transformation phenomena under the excitation of coherent beams are evidenced by the rigorous electromagnetic simulation. The research results have potential applications in on-chip integration of photonic circuitry.

ПОЛЯРИЗАЦІЙНО ТА ЧАСТОТНО СЕЛЕКТИВНІ ХАРАКТЕРИСТИКИ ХІРАЛЬНОЇ ПОВЕРХНІ, ЩО СКЛАДАЄТЬСЯ З ПЕРІОДИЧНО РОЗТАШОВАНИХ ДІЕЛЕКТРИЧНИХ КВАДРАТНИХ СПІРАЛЕЙ

Subject and Purpose. The present study is concerned with the linearly polarized electromagnetic wave transmission through a chiral metasurface composed of periodically assembled square dielectric helices. We expect that the metasurface of the kind has a wider range of functional capabilities to transform a polarized wave into a cross-polarized one when compared to a similar metasurface composed of metal helices. Methods and Methodology. To find the scattering coefficients of the considered structure, the well-established method of integral functionals is followed. A set of volume integral equations in the vectorial form is solved for the equivalent electric and magnetic polarization currents of the analyzed periodic layer. A distinctive feature of the method is that the internal electromagnetic fields of the structure are initially found, whence the fields scattered by this structure are sought. The equations are discretized in terms of integral functionals related to the polarization currents and through the use of the double Floquet–Fourier series expansion technique. Results. It has been found that the metasurface transmission coefficients depend critically on the number of bars making the square helical particle. In the case of an even bar number, the chiral metasurface exhibits the same transmission coefficients for co- polarized field components in the event that linearly x- and y-polarized waves are incident. For cross-polarized field components, the transmission coefficients differ and can reach peak values at different frequencies. Finally, transmission coefficients of these polarizers have been investigated versus dimensions of helice-making bars. Conclusion. A wide variety of transmission properties observed in the metasurfaces make them particularly attractive for use in polarization converting and separating devices. The metasurface can feature dichroic asymmetric transmission and be used as a dichroic filter with polarization transformation. It can be put to use in differential phase sections and, also, as an effective dichroic cross-polarization converter (twist polarizer)

Simulation Design and Characteristic Research of Electromagnetic Metasurface Absorber

Electromagnetic metasurface technology is one of the most promising technologies for electromagnetic energy regulation. It is formed by an artificial periodic structure of discrete subwavelengths at the interface, allowing wavefront control and polarization control at the subwavelength scale, exhibiting a variety of special electromagnetic response capabilities, including abnormal beam bending, polarization transformation, electromagnetic wave absorption, etc. We propose a wide-angle, polarization-insensitive infrared perfect metasurface absorber made of an opaque gold ground layer, a dielectric spacer layer, and a hole-shaped gold patch on the spacer layer. The absorption spectrum of the metasurface absorber is simulated by the finite element method, and the results show that the absorber produces an absorption peak with a maximum absorption rate of 99.91% and a half-height and full width of 0.52um in the visible light band.

Rotation-Invariant Feature Learning via Convolutional Neural Network With Cyclic Polar Coordinates Convolutional Layer

Convolutional neural networks (CNNs) have been demonstrated to be powerful tools to automatically learn effective features from large datasets. Though features learned in CNNs are approximately scale-, translation-, and position-invariant, and their capacity in dealing with image rotations remains limited. In this article, a novel cyclic polar coordinate convolutional layer (CPCCL) is proposed for CNNs to handle the problem of rotation invariance for feature learning. First, the proposed CPCCL converts rotation variation into translation variation using polar coordinates transformation, which can easily be handled by CNNs. Moreover, cyclic convolution is designed to completely handle the translation variation converted from rotation variation by conducting convolution in a cyclic shift mode. Note that the proposed CPCCL is capable of generalization and can be used as a preprocessing layer for classification CNNs to learn the rotation-invariant feature. Extensive experiments over three benchmark datasets demonstrate that the proposed CPCCL can clearly handle the rotation-sensitive problem in traditional CNNs and outperforms several state-of-the-art rotation-invariant feature learning algorithms.

Анализ переходных процессов давления вертикальной скважины в карбонатных коллекторах

In this paper, a new mathematical model of unsteady flow of a naturally fractured porous medium is presented,in which artificial fractures intersecting a vertical well and three different geometries of pore blocks containing plates, cylinders and spheres were considered. A new solution was obtained using the Laplace transform and an integral approach using the point source function. A polar coordinate transformation was used to process the radial distribution of an arbitrary number of cracks and angle. The model was then tested against three published cases.

Robust Watermarking Algorithm for Medical Volume Data Based on Polar Cosine Transform and 3D-DCT

Robust Watermarking Algorithm for Medical Volume Data Based on Polar Cosine Transform and 3D-DCT

A novel numerical method based on a high order polynomial approximation of the fourth order Steklov equation and its eigenvalue problems

<p style='text-indent:20px;'>Based on high order polynomial approximation and dimension reduction technique, we propose a novel numerical method for the fourth order Steklov problems in the circular domain. We first decompose the primal problem into a set of 1D problems via polar coordinate transformation and Fourier basis functions expansion. Then, by introducing a non-uniformly weighed Sobolev space, the variational form and corresponding discrete scheme are derived. Employing the Lax-Milgram lemma and approximation properties of the projection operators, we further prove existence and uniqueness of weak solutions and approximation solutions for each one-dimensional problems, and the error estimation between them, respectively. We also carry out ample numerical experiments which illustrate that the numerical algorithm is efficient and highly accurate.</p>

Trajectory Tracking Performance Transition Analysis from Polar to Cartesian Coordinates

Trajectory tracking of underactuated marine vessels has become an intense research area in the nonlinear control community over the past two decades. In the authors’ previous work, an asymptotic tracking scheme was proposed by introducing two polar coordinate transformations, which can transform two-input-three-output underactuated system model into a certain two-input-two-output one. Therefore, it becomes possible to solve the trajectory tracking problem of these kinds of underactuated system using general backstepping method. However, since the polar coordinate transformation does not satisfy to be a diffeomorphism, the proposed tracking scheme in the polar frame cannot guarantee the same tracking performance in the Cartesian frame. With this consideration, in this paper the authors aim to analyze and establish a generalized condition under which the proposed tracking scheme in the previous work can guarantee the same tracking property in the Cartesian frame. The analysis results are verified through numerical studies as well.

Polarformer: Optic Disc and Cup Segmentation Using a Hybrid CNN-Transformer and Polar Transformation

The segmentation of optic disc (OD) and optic cup (OC) are used in the automatic diagnosis of glaucoma. However, the spatially ambiguous boundary and semantically uncertain region-of-interest area in pictures may lead to the degradation of the performance of precise segmentation of the OC and OD. Unlike most existing methods, including the variants of CNNs (Convolutional Neural Networks) and U-Net, which limit the contributions of rich global features, we instead propose a hybrid CNN-transformer and polar transformation network, dubbed as Polarformer, which aims to extract discriminative and semantic features for robust OD and OC segmentation. Our Polarformer typically exploits contextualized features among all input units and models the correlation of structural relationships under the paradigm of the transformer backbone. More specifically, our learnable polar transformer module optimizes the polar transformations by sampling images in the Cartesian space and then mapping them back to the polar coordinate system for masked-image reconstruction. Extensive experimental results present that our Polarformer achieves superior performance in comparison to most state-of-the-art methods on three publicly available datasets.

Boundary-aware feature and prediction refinement for polyp segmentation

ABSTRACT Polyp segmentation from colonoscopy videos is an essential task in medical image processing for detecting early cancer. However, segmenting a precise boundary is still challenging, even with powerful deep neural networks. We consider the difficulty can be caused by: (1) the ambiguity boundary and (2) some complicated shape makes polyps hard to segment. To address these problems, we propose the Boundary-aware Feature and Prediction Refinement framework (BaFPR) for polyp segmentation. Specifically, we design a segmentation decoder for representation learning with boundary prior and propose a novel consistency loss to learn clues from the polar coordinate. The decoder mainly consists of a boundary prior module (BPM) and a bi-directional fusion module (BiFM). BPM is designed to learn the boundary prior, while BiFM learns to fuse representations of BPM and multi-scale representations from an encoder. To handle these complicated shapes of polyps, we maintain an extra segmentation network that learns with polar transformations of data to provide extra clues for the main segmentation network by our proposed consistency loss. We evaluated BaFPR with five challenging datasets for polyp segmentation and the results showed that our proposal consistently improves the segmentation performance of polyps. Code available at: https://github.com/MoriLabNU/BaFPR.

Chirality-assisted spin Hall effect of light in the vicinity of the quasi-antidual symmetry mode of a chiral sphere

The spin Hall shift (SHS) refers to a transverse shift in the scattering plane during the spin-orbit interaction (SOI). SHS is considerably small when light is scattered by a sphere due to the absence of unidirectional scattering. This work shows that the chiral property of a sphere can offer a platform to optimize the SOI by achieving nearly zero forward scattering with significant backward scattering. As a result, a polarization transformation takes place and the scattered field transfers its maximum spin angular momentum to orbital angular momentum. Consequently, an enhanced transversal shift is observed due to the momentum conservation of the scattered field. The results reveal that the shift strongly depends on the handedness of the chiral sphere and the helicity of the incident beam. Thus, offering an alternative paradigm for the quantitative measurement of chirality parameters of a single chiral nanoparticle. We hope that these results will potentially shed new light on the SOI of various forms that can find potential applications such as optical sensing, chiral resolution of single nanoparticles, precision measurements, and the manipulation of subwavelength nanoparticles.

All-Fiber Waveplate Made of Helically Wound Spun Highly Birefringent Optical Fiber

Waveplates are elements that are widely used in the optical system for polarization transformation. In the fiber optical system, it is highly desired to utilize waveplates in the all-fiber form with minimum insertion loss and stable performance. In this paper, we propose an all-fiber waveplate that is made of the helically wound spun highly birefringent (SHB) optical fiber. To function as waveplates, the torsion of the helix should be equal to the inherent polarization rotation of the SHB fiber so that the geometric rotation can match the inherent polarization rotation. Therefore, the phase difference between two orthogonal components of the incident polarized light can increase almost linearly with the fiber length. Because the SHB fiber is insensitive to external perturbations, the proposed waveplate can provide a definite and stable polarization transformation. We develop a model based on the perturbation theory to characterize the polarization evolution of the helically wound SHB fiber. Simulations and experiments have demonstrated the excellent performance of our all-fiber waveplates.