Field Point Research Articles

Metamagnetic anomalies in the kinetic Ashkin–Teller model

This study investigates the metamagnetic anomaly in the Ashkin–Teller spin-1/2 model in a ferromagnetic state, utilizing dynamic mean-field theory on a cubic lattice from a stochastic theory. We analyze instantaneous magnetizations over time, dynamic order parameters, and magnetic susceptibilities concerning the constant bias field, as well as examining dynamic phase diagrams. Our observations reveal that dynamic phase transitions occur at specific points of the constant bias field, where instantaneous magnetization transitions from oscillating between negative and positive states to a strictly positive state. We also observe a narrow region in the dynamic phase diagram between phase transitions of different order parameters of the model, for some conditions among the couplings of these order parameters. These results contribute to an understanding of the dynamic behavior of the spin-1/2 AT model under ferromagnetic conditions, providing interesting insights into phase transitions and the metamagnetic anomaly.

Uni/multi variate polynomial embeddings for zkSNARKs

AbstractA zero-knowledge proof is a cryptographic primitive that enables a prover to convince a verifier the validity of a mathematical statement (an NP statement) without revealing any secret inputs to the verifier. A special case, called zero-knowledge Succinct Non-interactive ARgument of Knowledge (zkSNARK) is particularly designed for arithmetic circuit proof systems which have important applications in blockchain privacy. The major computations in this type of zkSNARK proofs with post-quantum security are polynomial evaluations and Lagrange interpolations over finite fields. Given a sequence over a finite field, in the field of coding and sequences research, we understand that there are two representations of the sequence, one is a univariate polynomial and the other, a multivariate polynomial. This is exactly what is done in those zero-knowledge proof systems to transform the proof of a R1CS relation to evaluate uni/multi variate polynomials at some random points in the finite field. In this paper, we present a comparative analysis on how to convert a rank 1 constrained satisfiability (R1CS) system (more general than a circuit system) into a polynomial equality and provide analysis on the concrete complexities of provers, proof sizes and verifiers. We use two concrete zkSNARK schemes, i.e., Polaris, univariate polynomial encodings and Spartan, multivariate polynomial encodings, as examples to show our analysis. Secondly, we propose to select interpolating sets as subfields instead of affine spaces of a large field for Lagrange interpolation. This new method has improved the performance of R1CS encodings largely. We comment that post-quantum secure zkSNARKs yield post-quantum digital signatures with security only depending on symmetric-key schemes. Some open problems are proposed at the end of the paper.

CNN-based prediction of microstructure-derived random property fields of composite materials

The simulation of random spatial variation in the mechanical properties of composite materials using random fields derived from their microstructure can be computationally demanding, since it often requires numerical homogenization of a large number of stochastic volume elements (SVEs). These SVEs are usually extracted from an initial image of the composite microstructure by using a moving window technique and their homogenized properties constitute the discrete data points of the random field at the centroid of each SVE. By replacing the expensive and highly repetitive homogenization procedure with a convolutional neural network (CNN), it is possible to perform nearly instant computations of random property fields. In this work, a CNN is proposed, that takes as input an SVE image and returns its apparent mechanical properties, and can therefore be applied along with the moving window technique. Training is performed on randomly generated SVEs with varying volume fractions and inclusion positions, which are representative of the SVEs obtained during processing of the initial large composite image. It is shown that the proposed CNN can accurately predict the mechanical properties of SVEs and it is subsequently applied for the prediction of random property fields derived from computer simulated and real microstructure images. Results show that, with the proposed methodology, it is possible to make accurate predictions of random fields within a few seconds, a procedure which could potentially require hours of computation time with the finite element based approach.

Hemi-diaphragm detection of chest X-ray images based on convolutional neural network and graphics.

Chest X-rays (CXR) are widely used to facilitate the diagnosis and treatment of critically ill and emergency patients in clinical practice. Accurate hemi-diaphragm detection based on postero-anterior (P-A) CXR images is crucial for the diaphragm function assessment of critically ill and emergency patients to provide precision healthcare for these vulnerable populations. Therefore, an effective and accurate hemi-diaphragm detection method for P-A CXR images is urgently developed to assess these vulnerable populations' diaphragm function. Based on the above, this paper proposes an effective hemi-diaphragm detection method for P-A CXR images based on the convolutional neural network (CNN) and graphics. First, we develop a robust and standard CNN model of pathological lungs trained by human P-A CXR images of normal and abnormal cases with multiple lung diseases to extract lung fields from P-A CXR images. Second, we propose a novel localization method of the cardiophrenic angle based on the two-dimensional projection morphology of the left and right lungs by graphics for detecting the hemi-diaphragm. The mean errors of the four key hemi-diaphragm points in the lung field mask images abstracted from static P-A CXR images based on five different segmentation models are 9.05, 7.19, 7.92, 7.27, and 6.73 pixels, respectively. Besides, the results also show that the mean errors of these four key hemi-diaphragm points in the lung field mask images abstracted from dynamic P-A CXR images based on these segmentation models are 5.50, 7.07, 4.43, 4.74, and 6.24 pixels,respectively. Our proposed hemi-diaphragm detection method can effectively perform hemi-diaphragm detection and may become an effective tool to assess these vulnerable populations' diaphragm function for precision healthcare.

Description of the local hemodynamic environment in intracranial aneurysm wall subdivisions.

Intracranial aneurysms (IAs) pose severe health risks influenced by hemodynamics. This study focuses on the intricate characterization of hemodynamic conditions within the IA walls and their influence on bleb development, aiming to enhance understanding of aneurysm stability and the risk of rupture. The methods emphasized utilizing a comprehensive dataset of 359 IAs and 213 IA blebs from 268 patients to reconstruct patient-specific vascular models, analyzing blood flow using finite element methods to solve the unsteady Navier-Stokes equations, the segmentation of aneurysm wall subregions and the hemodynamic metrics wall shear stress (WSS), its metrics, and the critical points in WSS fields were computed and analyzed across different aneurysm subregions defined by saccular, streamwise, and topographical divisions. The results revealed significant variations in these metrics, correlating distinct hemodynamic environments with wall features on the aneurysm walls, such as bleb formation. Critical findings indicated that regions with low WSS and high OSI, particularly in the body and central regions of aneurysms, are prone to conditions that promote bleb formation. Conversely, areas exposed to high WSS and positive divergence, like the aneurysm neck, inflow, and outflow regions, exhibited a different but substantial risk profile for bleb development, influenced by flow impingements and convergences. These insights highlight the complexity of aneurysm behavior, suggesting that both high and low-shear environments can contribute to aneurysm pathology through distinct mechanisms.

Performance Analysis and Design Considerations of the Near-Field-Focused Rotman Lens Antennas

This study investigates the application of Rotman lens antennas in the near field. The design equations of these antennas have been derived in the near field and demonstrated to be highly effective. By considering specific examples, the shapes of the inner surfaces of these lens antennas have been analyzed and discussed, revealing how practically realizable lens surfaces can be designed. As these Rotman lenses are perfect at only three points in the near field, they exhibit phase errors at other points along a line connecting the three near-field focal points, resulting in deterioration of the near-field patterns. It has been shown that by selecting the lens parameters appropriately, these phase errors can be kept to a minimum, causing only minimal beam deterioration. Compared to far-field-focused Rotman lens antennas, near-field-focused Rotman lens antennas achieve significantly higher power levels, having 3.8 to 6.3 dB improvement for different beams of a 17-element array. The study has demonstrated the potential of Rotman lenses as multiple beamforming antennas for near-field applications.

Conical indentation over a transversely isotropic and layered elastic half-space

We propose a novel method for solving the static response of a conical indenter on a transversely isotropic and layered elastic half-space. The newly developed Fourier-Bessel series (FBS) system of vector functions, along with the unconditionally stable dual-variable and position method, is employed to derive the Green's function in the transversely isotropic and layered elastic half-space under a vertical ring load on the surface. To calculate the response at different field points on the surface, we apply discrete love numbers within the FBS vector system. The load densities in the discretized rings within the contact radius of the conical indenter are determined using the integral least-square method, along with a self-adaptive algorithm developed in this study. Finally, the relationship between the indentation depth (vertical displacement) and the applied load is obtained through force balance between the external load and the summed contact traction. The developed scheme is validated using existing exact solutions for the reduced homogeneous half-space case. Selected numerical results clearly demonstrate the effect of anisotropic material and layering on the indentation response. It is observed that, regardless of whether the structure is a stratified half-space or a layered structure with a rigid substrate, the material properties in the top layer have the most significant influence on the indentation behavior. In the case of a layered structure with an underlying elastic half-space, the material properties in the interlayer and bottom layer could also affect the indentation behaviors.

Rare and Complicated Granulomatous Lobular Mastitis (2000-2023): A Bibliometrics Study and Visualization Analysis.

Granulomatous mastitis (GLM) is a rare and complex chronic inflammatory disease of the breast with an unknown cause and a tendency to recur. As medical science advances, the cause, treatment strategies, and comprehensive management of GLM have increasingly attracted widespread attention. The aim of this study is to assess the development trends and research focal points in the GLM field over the past 24 years using bibliometric analysis. Using GLM, Granulomatous mastitis (GM), Idiopathic granulomatous lobular mastitis (IGLM), and Idiopathic granulomatous mastitis (IGM) as keywords, we retrieved publications related to GLM from 2000 to 2023 from the Web of Science, excluding articles irrelevant to this study. Citespace and VOSviewer were employed for data analysis and visualization. A total of 347 publications were included in this analysis. Over the past 24 years, the number of publications has steadily increased, with Turkey being the leading contributor in terms of publications and citations. The University of Health Sciences, Istanbul University, and Istanbul University Cerrahpasa were the most influential institutions. The Breast Journal, Breast Care, and Journal of Investigative Surgery were the journals that published the most on this topic. The research primarily focused on the cause, differential diagnosis, treatment, and comprehensive management of GLM. Issues related to recurrence, hyperprolactinemia, and Corynebacterium emerged as current research hotspots. Our bibliometric study outlines the historical development of the GLM field and identifies recent research focuses and trends, which may aid researchers in identifying research hotspots and directions, thereby advancing the study of GLM.

Heat Transfer of Casson Nanofluid Flow Between Double Disks: Using Buongiorno Model

Purpose: Fluid thermal efficiency is crucial in major industrial sectors. Traditional fluids often lack the heat transmission needed for various operations. To address this, researchers introduced metallic and non-metallic nano additives, creating a new type of fluid called Nanofluid. This article explores the squeezing flow of Casson nanofluid between parallel disks, considering suction/injection, thermophysical impacts, thermal radiation, and chemical reaction. Methodology: The study uses the Buongiorno nanofluid theory to analyze thermophoresis and Brownian motion, reducing partial differential equations to ordinary differential equations. Numerical technique (shooting approach) is employed to solve these equations, and the results are presented graphically. Conclusions: The study reveals that axial velocity decreases as the Casson fluid parameter increases. Near the intersection point of the velocity field with varying magnitudes of the linear thermal convection parameter, radial velocity increases. It is observed that the thermal field intensifies with a higher linear thermal convection parameter. Additionally, elevated values of the thermal radiation parameter lead to an increase in temperature distribution estimates. Applications of Current Model: Casson fluid, classified as a non-Newtonian fluid, exhibits characteristics of both an elastic solid at low shear strain and a Newtonian fluid at high stress. It is characterized by infinite viscosity at zero shear rate and infinite viscosity at infinite shear rate. Examples of Casson fluids in everyday life include tomato juice, human blood, soup, and orange juice.

Numerical simulation analysis and experimental verification of air flow measurement in large-diameter S-shaped pipe

Abstract The ventilation systems in nuclear power plants, hydropower plants, and other large-scale projects involve the transportation of fluids through large-scale pipelines. To achieve a more stable flow velocity distribution, the fluid needs to pass through a straight pipe section of sufficient length upon entering the pipe. Typically, this straight pipe section should be at least 15 times the inner diameter of the pipe. However, for large-diameter irregular square pipes with a diameter exceeding 1m, where the curved section is short and there are no long straight pipe sections before and after it, the flow field inside the pipe becomes complex, requiring accurate measurement of the flow rate.In this regard, a numerical simulation analysis is conducted to address this challenge. A mean velocity evaluation method based on the coefficient of variation is proposed. This method identifies multiple points within the pipe that best represent the average flow velocity, determining the insertion depth of sensors and the weight coefficients of these multiple measuring points. A calculation formula is derived, utilizing the cross-sectional average velocity as a function with the velocity values at multiple points in the flow field as independent variables. To validate the accuracy of the proposed method, flow measurement experiments are performed on a wind tunnel test bench. The calculated values obtained from the derived formula through numerical analysis are compared with the experimental results. The relative error within the full range is found to be less than 0.54%, confirming the accuracy of the formula. The research findings present a novel measurement method for airflow in large-diameter irregular square pipes and offer valuable practical insights for engineering applications.

Field‐Aligned Currents Associated With Pulsating Auroral Patches: Observation With Magneto‐Impedance Magnetometer (MIM) Onboard Loss Through Auroral Microburst Pulsations (LAMP) Sounding Rocket

AbstractWe made observations of magnetic field variations in association with pulsating auroras with the magneto‐impedance sensor magnetometer (MIM) carried by the Loss through Auroral Microburst Pulsations (LAMP) sounding rocket that was launched at 11:27:30 UT on 5 March 2022 from Poker Flat Research Range, Alaska. At an altitude of 200–250 km, MIM detected clear enhancements of the magnetic field by 15–25 nT in both the northward and westward components. From simultaneous observations with the ground all‐sky camera, we found that the footprint of LAMP at the 100 km altitude was located near the center of a pulsating auroral patch. The auroral patch had a dimension of ∼90 km in latitude and ∼25 km in longitude, and its major axis was inclined toward northwest. These observations were compared with results of a simple model calculation, in which local electron precipitation into the thin‐layer ionosphere causes an elliptical auroral patch. The conductivity within the patch is enhanced in the background electric field and as a result, the magnetic field variations are induced around the auroral patch. The model calculation results can explain the MIM observations if the electric field points toward southeast and one of the model parameters is adjusted. We conclude that the pulsating auroral patch in this event was associated with a one‐pair field‐aligned current that consists of downward (upward) currents at the poleward (equatorward) edge of the patch. This current structure is maintained even if the auroral patch is latitudinally elongated.

Sustainable Development of Platform Enterprises: A Synthesis Framework

Enterprises are the most important core organizations of the country and modern society, and their growth has always been a focal point in the theoretical field. This paper aims to focus on the sustainable development of platform enterprises by exploring the mechanism of platform growth. Thus, this paper reviews the literature and analyzes the challenges faced by platform enterprises during the four stages of birth, expansion, leadership, and self-renewal, as well as the strategies they have adopted. The main aims of this paper are to help understand the growth process of platform enterprises and identify three key points that need to be addressed for sustainable growth, including the disadvantages of resource externalities, the importance of the restructuration of business models, and the urgency of fulfilling social responsibility. To address the exogenous nature of resources, platform enterprises should pay attention to the initiative of complementors, the distribution of benefits, and ecological orchestration. The impact of technology, especially artificial intelligence, on business models and the application of technology to restructure business models should be given attention. It is also necessary to pay attention to how platform enterprises undertake their social responsibilities. A synthesis framework with seven propositions for future research has been proposed.

Imaginary past of a quantum particle moving on imaginary time

The analytical continuation of classical equations of motion to complex times suggests that a tunneling particle spends in the barrier an imaginary duration i|T|. Does this mean that it takes a finite time to tunnel, or should tunneling be seen as an instantaneous process? It is well known that examination of the adiabatic limit in a small additional AC field points towards |T| being the time it takes to traverse the barrier. However, this is only half the story. We probe the transmitted particle's history, and find that it very little of the field's past behavior, as if the transit time were close to zero. The ensuing contradiction suggests that the question is ill posed, and we explain why. Published by the American Physical Society 2024

Efficient method for calculating sound radiation from a circular source in an infinite baffle

The numerically efficient solution describing the sound radiation from a circular source located in a flat, rigid baffle is obtained. For this purpose, a half-space was divided into two subregions coupled through continuity equations. The Helmholtz equation was solved in both subregions. The proposed method can be used for circular baffled sources in the case when fluid–structure interactions are included, as well as for an input from a waveguide or cavity. The validity and numerical efficiency of the presented solution were tested assuming that a clamped circular plate is a source. The numerical simulations show that the results given by the proposed method agree with those given by the known integral solution. The exceptions are the field points at which the integral formulas fail and provide incorrect values of the sound pressure. Hence, the presented formulas can be the only method to perform accurate calculations at troublesome field points. The numerical efficiencies of the obtained formulas and integral ones were compared by estimating the value of the appropriate time ratios. The numerical analysis shows that the proposed method can be used to significantly improve calculations of the sound power and the sound pressure.

Calculation of Plates of Different Shapes Using Generalized Equations of the Finite Difference Method

Statement of the problem. The article reviewed nonaxisymmetric tasks for calculating slabs in shape of a circle sector, wedge and a slab formed by a connection of rectangular and circular areas. The solution is based on generalized equations of the finite differences method. The algorithm allows us to take into account finite discontinuities of the desired function, the right side of the original differential equations, as well as discontinuities of derivatives of these functions without accumulation of the grid and using points outside the contour. It resolves oneself into a system of differential algebraic equations generated for field and contour points. In this paper the initial differential equations and their numerical approximation are provided. Results. Calculations of a semicircle and a wedge under different boundary conditions are presented, as well as an uncut slab in the form of a semicircle with an annular support and a composite slab are consi-dered. The solution of the above problems has been carried out on the minimum possible computational grid, comparison with the available solutions has been provided, and static checks of the calculation have been carried out. Conclusions. Along with the most common numerical method for calculating buildings and structures, it is possible and quite effective to use these equations. It is proved by means of some examples that such an approximation has a number of advantages: the results allow us to talk about the sufficient accuracy of the solution with a small number of partitions; fundamental simplicity and universality of the method.

Vibration and underwater noise simulation of a river-crossing tunnel based on a 2.5D structural-acoustic finite element method

To protect the underwater ecosystem and species, the vehicle-induced vibration and underwater radiated noise of river-crossing tunnels need to be calculated efficiently and accurately. For this purpose, this study proposed a 2.5-dimensional (2.5D) structural-acoustic finite element method which combines 2.5D finite element vibration algorithm and 2.5D infinite element acoustic algorithm. The proposed method utilizes the spatial wave number transformation theory and the acoustic transfer vector (ATV) method. Based on a river-crossing tunnel, a 2.5D numerical simulation model was established in this study to analyze the vehicle-induced tunnel-soil vibration as well as the underwater radiated noise during operation. The results showed that the tunnel vibration and the associated radiated noise mainly distributed in the range of 10 to 40 Hz, with two peaks at 15.6 Hz and 31.5 Hz, respectively. The total sound pressure level (SPL) of the predicted noise at each field point reached a maximum value of 126 dB. The 2.5D algorithm proposed in this study achieves higher computational efficiency compared to traditional 3D vibration and noise analysis methods, which can provide theoretical and technical supports for the protection of underwater ecological diversity.

INVESTIGATION OF THE CYLINDRICAL RESONATING CAVITY EFFECT ON A JET’S NEAR ACOUSTIC FIELD IN THE TWO-CHANNEL SYSTEM

Numerical gas flow modeling in the two-channel resonance system path of ITAM SB RAS is carried out. Numerical simulation of a nonstationary acoustic-convective flow was carried out using the Ansys Fluent software package in a three-dimensional formulation. As a result of the simulation, the gas-dynamic characteristics of the flow in the system central part, where a supersonic under-expanded jet is formed, are obtained. The analysis of pressure distributions in the first barrel of the jet near field, as well as inside its structure under the conditions of a two-channel system, is carried out. Six points in the near field of the jet were selected for the study. Taking into account the unsteadiness of the flow in the resonant system path, the studied points record the fluctuations of the formed flow and the change in the jet structure. The spectral composition is estimated near and inside the jet undisturbed by the resonator and a comparison with the spectrum of the resonant system is presented. The possibility of influencing the jet structure and acoustic characteristics near the jet using a resonator is shown.

Mapping-based design method for high-quality integral projection system

A general method for designing an integral projection system is proposed, including optical design and digital preprocessing based on the mapping within the projection system. The per-pixel mapping between the sub-images and the integral projection image is generated by incorporating an integral projection imaging model as well as the ray data of all sub-channels. By tracing rays for sparsely sampled field points of the central sub-channel and constructing the mapping between the central sub-channel and other sub-channels, the efficient acquisition of ray data for all sub-channels is achieved. The sub-image preprocessing pipeline is presented to effectively address issues such as overlapping misalignment, optical aberrations, inhomogeneous illumination, and their collective contribution. An integral projection optical system with a field of view (FOV) of 80°, an F-number of 2, and uniform image performance is given as a design example. The ray tracing simulation results and quantitative analysis demonstrate that the proposed system yields distortion-free, uniformly illuminated, and high-quality integral projection images.

Fluid simulations of resistive drift-wave turbulence with diamagnetic flow in ZPED experiments

We derive a diamagnetic resistive fluid model (DRF) and develop an associated two-dimensional fluid simulation code (DRF-2D) to explore the dynamics of resistive drift modes within the plasmas of the Zheda Plasma Experiment Device (ZPED). The validation of the linear dispersion relation for the DRF-2D code revealed a harmonious agreement between analytical theory and linear numerical simulations. Leveraging plasma parameters obtained from the ZPED experiments, we conducted a comprehensive series of nonlinear simulations using the DRF-2D code. Our simulations successfully replicate the nonlinear trends in turbulent fluctuations and transport observed in the ZPED experiments, particularly demonstrating a remarkably accurate alignment of the turning point in the magnetic field. Notably, the DRF model sheds light on the observed frequency sign reversal from the electron diamagnetic direction to the ion diamagnetic direction in the ZPED experiments. This is demonstrated through well-matched turning points in the confining magnetic field between the nonlinear simulations and ZPED experiments. The fidelity of our model in capturing these phenomena underscores its efficacy in providing valuable insights and predictive capabilities for the intricate dynamics observed in the ZPED plasmas.

Reconstruction of measurement data with multiple outliers using novel domain-based RBF

Due to the high accuracy of computation, radial basis function (RBF) is widely recognized as a versatile and effective method for interpolating and approximating discrete points in various fields. However, RBF is quite sensitive to outliers, which can easily lead to distorted results. In this article, a novel overlapped domain-based RBF (ODRBF) method is proposed, in which the concept of effective domain is introduced to build a moving model, and Student’s t-regression and Gaussian mixture model (GMM) clustering are used for dealing with local anomalies. By introducing the effective domain, the estimated points and domain radius are constructed and the global model can be transformed into local estimation models. In each effective domain, a series of estimation models are iteratively generated through Student’s t-regression, and based on the distances between the estimation model and discrete points, GMM clustering is used to subsequently select the data as the input of the next regression. This iterative strategy in each effective domain ensures the removal of multiple outliers. Then, the preserved points in the processed effective domain are used to obtain local estimated value by RBF. The proposed method demonstrates strong robustness to highly contaminated dataset in the reconstruction of the simulation and experimental datasets.