Points Of Curve Research Articles

Gully Erosion Development in Drainage Basins: A New Morphometric Approach

The formation and evolution of management gullies is a highly intense process of soil erosion often overlooked in policies and river basin strategies. Despite the worldwide spread of the phenomenon, our ability to assess and simulate gullying and its impacts remains limited; therefore, predicting the development and evolution of these river reaches represents a significant challenge, especially in areas where the loss of productive soil or the hazards linked to landslides or floods represent critical factors. Our study demonstrates how an exclusively morphometric approach, based on the construction of the hypsometric curve and applied to small hydrographic basins that are lithologically homogeneous and hierarchized according to the Strahler classification method, is able to predict the triggering height of the gullies; this height corresponds to the mean elevation of the basin and the inflection point of the hypsometric curve itself, confirming the hypothesis that this point coincides with the point at which a sudden change in surface runoff energy occurs, The study also shows that the portion of the basin necessary to trigger these intense erosive processes is always within a small range, regardless of the size and morphology (slope) of the basin itself. Such an approach, which is quick and relatively easy to apply, could help develop hydrogeological hazard mitigation practices in land planning projects.

Cryptosystems based on isomorphic transformations of elliptic curve points.

The article presents research in the field of development and improvement of cryptographic systems based on elliptic curves isomorphic transformations potentially resistant to quantum cryptanalysis. Analysis results of existing asymmetric cryptosystems disadvantages and advantages, including those based on isomorphic transformations, are presented. The approaches to the construction of cryptographic algorithms based on isogenies of elliptic curves, which can become the basis for creating cryptosystems resistant to quantum attacks, are investigated. In the course of the research, program functions were developed to implement operations on elliptic curves isogenies of different orders, which will ensure the security levels specified in the standard: 256, 384, 512. A software implementation of the operations of a curve point scalar multiplication and operations on elliptic curve isogenies has been developed, on the basis of which experimental values of the time to perform the scalar product using parallelization have been obtained. Experiments have been conducted to compare the classical multiplication of a curve point with the representation of the scalar k as a sequence of 4-bit words, which made it possible to speed up the scalar multiplication operation by 30 times, for 8-bit words the speedup was 18.8 times. The direction of further research is the development of methods for the generation and verification of a digital signature, based on transformations over the isogeny points of the elliptic curve using the parallelization of operations of scalar multiplication of the curve point.

Analysis of the influence of damp-heat aging on the shear failure of the adhesive joint of composite materials

Abstract In this study, a comprehensive temperature and humidity environment chamber was used to accelerate the artificial aging of carbon fiber bonded joint specimens in wet and hot environments, and shear tests were conducted on non-aging and wet and hot aging specimens, respectively. At the same time, acoustic emission technology was used to monitor the damage to the specimen, and the influence of wet and heat aging on the shear properties and damage forms of the bonded joint was explored. It is found that under shearing load, the unaged bonded joint specimens first show delamination degumming damage with an energy distribution of about 1000 (mV*mS) and then fiber fracture damage with an energy distribution of more than 4000 (mV*mS). According to the load strain curve, it can be seen that the shear strength of the moisture-heat aging specimen decreases by 30% compared with that of the non-aging specimen, from 33.6 kN to 22.3 kN. According to the load energy curve, it can be seen that the rubber layer of the specimen is damaged at the inflection point of the load curve, the rubber layer of the non-aging specimen is damaged at 15 kN, and the rubber layer of the moisture-heat aging specimen is damaged at 8 kN. The test results show that the wet heat aging reduces the interlayer properties of the specimens. The structural adhesive delamination is serious, which leads to the damage of the aged specimens in advance compared with the non-aged specimens. The overall deformation of the specimens increases.

Dynamical systems for arithmetic schemes

Motivated by work of Kucharczyk and Scholze, we use sheafified rational Witt vector rings to attach a new ringed space Wrat(X) to every scheme X. We also define R-valued points Wrat(X)(R) of Wrat(X) for every commutative ring R. For normal schemes X of finite type over specZ, using Wrat(X)(ℂ) we construct infinite dimensional R-dynamical systems whose periodic orbits are related to the closed points of X. Various aspects of these topological dynamical systems are studied. We also explain how certain p-adic points of Wrat(X) for X the spectrum of a p-adic local number ring are related to the points of the Fargues–Fontaine curve.

Exploring spatiotemporal distribution characteristics of air quality and driving factors: empirical evidence of 288 cities in China.

Excellent air quality is important for China to achieve high quality economic development. The paper analyses the spatial and temporal distribution characteristics of the air quality index (AQI) in 288 Chinese cities, and further investigates the driving factors affecting air quality using the spatial Durbin model (SDM) based on the panel data of 288 Chinese cities from 2014 to 2021. The results of the study show that: (1) China's air quality level has improved in general, but there are large differences in air quality between regions; (2) China's AQI has significant spatial positive autocorrelation, and the Moran's scatter plot shows a high-high and low-low agglomeration; (3) The driving factors of air quality have different effects, and regional heterogeneity is obvious. Some developed regions in China have already crossed the inflexion point of the environmental Kuznets curve (EKC); promoting industrial upgrading and reducing pollutant emissions can significantly improve urban PM2.5 concentrations; and the "Three-Year Strategy for Conquering the Blue Sky War" policy has lowered the AQI in North China and improved PM2.5 concentrations nationwide. Based on the above findings, the paper puts forward corresponding policy recommendations.

Age-related T1 mapping, fat fraction, diffusion and perfusion parameters of the lumbar vertebrae in healthy children under 3.0 T MRI

Compare the T1 mapping, fat fraction, diffusion and perfusion parameters of the lumbar vertebrae of different age groups to establish normal values for healthy children and observe the trends in these parameters with age. A total of 146 healthy children (0-14 years) were included in this prospective study and underwent 3.0 T lumbar MRI examination. The study cohort was divided into five age groups (Group A∼E) according to development milestones in children. T1 mapping, Dixon and IVIM (intravoxel incoherent motion)sequence images were used to measure the parameters of lumbar vertebrae 2-4. The normal values of each parameter were measured and compared across different age groups. The T1 value was negatively correlated with age (r=-0.619, p<0.001). The fat fraction (FF%) was positively correlated with age (r=0.635, p<0.001). There was a negative correlation between the D value and age (r=-0.406, p<0.001). The D∗ value was positively correlated with age (r=0.54, p<0.001). The f value was positively correlated with age (r=0.775, p<0.001). The inflexion points of the T1 value and FF% curves were at approximately 3 years old (36 months).The inflexion points of the IVIM-related parameter curves were approximately 5 years old (60 months). The age-dependent differences in the vertebral body parameters of this pediatric cohort suggest changes in the bone marrow composition and cellular structure of the vertebral body during physiological growth in children. The establishment of normal values of children's lumbar spine can facilitate the clinical study of diseases.

Application of growth models to South African Boer goat castrates and does under feedlot conditions

Mathematical models may aid researchers in describing biological processes, like growth, in animals. This study aimed to collect the body weight data of 18 Boer goat castrates and 20 Boer goat does, from birth until maturity, to model growth and determine growth trends. This is a novel investigation as sufficient information on an age-weight database for these two Boer goat sexes from birth to maturity, is lacking. Using age-weight data, four nonlinear models, namely the Brody, Gompertz, Logistic and Von Bertalanffy growth models, were plotted and evaluated. The model parameters of each growth model were compared for differences between the two sexes. The statistical effectiveness of fit was determined for each model using AIC and RMSE, with R2 also being considered. All models except the Brody model, predicted significantly heavier mature weights for castrates. The Brody model was deemed unfit to describe Boer goat growth as the function severely over-predict weights from birth until maturity for both sexes. The Von Bertalanffy (R2 = 91.3) and Gompertz functions (R2 = 91.3) showed the best fit for Boer goat castrates, while the Gompertz model (R2 = 95.1) showed the best fit for Boer goat does. The Gompertz function is the preferred model to depict Boer goat growth overall, as it accurately characterized growth of both sexes. According to the Gompertz model the age at which the inflection point of the growth curve was reached, did not differ significantly between castrates and does (141.80 days versus 136.31 days). There was also no significant difference in maturation rate between the two sexes.

Optimizing Photometric Light Curve Analysis: Evaluating Scipy's Minimize Function for Eclipse Mapping of Cataclysmic Variables

With a particular focus on Scipy's minimize function—the eclipse mapping method is thoroughly researched and implemented utilizing Python and essential libraries. Many optimization techniques are used, including Sequential Least Squares Programming (SLSQP), Nelder-Mead, and Conjugate Gradient (CG). However, for the purpose of examining photometric light curves—these methods seek to solve the maximum entropy equation under a chi-squared constraint. Therefore, these techniques are first evaluated on two-dimensional Gaussian data without a chi-squared restriction, and then they are used to map the accretion disc and uncover the Gaussian structure of the Cataclysmic Variable KIC 201325107. Critical analysis is performed on the code structure to find possible faults and design problems. Additionally, the analysis shows how several factors impacting computing time and image quality are included—including the variance in Gaussian weighting, disc image resolution, number of data points in the light curve, and degree of constraint.

Radial vibration measurement of rotating shaft using constant density fringe pattern and line scan camera

The radial vibration signals of the rotor can provide abundant information about the health condition of the machine. In this paper, a simple vision-based measurement system is proposed to simultaneously measure two-dimensional displacements in radial directions for the rotating shaft, where the system consists of a constant density fringe pattern (CDFP), a line scan camera (LSC), and a lens. The CDFP should be installed around the surface of the rotating shaft to make the density of the fringe constant along the shaft axis, while the shaft axis is vertical to the optical axis of the LSC but not parallel to the line-array sensor of the LSC. Therefore, the density of the fringe imaged on the LSC is not constant because of the modulation of the circular surface of the shaft, and the distribution of the fringe density on the LSC is a U-shaped curve. Thus, the shaft centreline orbit can be tracked by the lowest point of the density distribution curve (DDC) of the fringe. Then, an efficient and accurate parameterized instantaneous frequency estimation method is employed to estimate the DDC of the fringe, because the variable density fringe can be regarded as an amplitude-modulated and frequency-modulated nonstationary signal whose instantaneous frequency function is equivalent to the DDC. Experimental results verify the feasibility and effectiveness of the proposed method by comparing it to the eddy current sensors.

Experimental evaluation of the short and long fatigue crack growth rate of S355 structural steel offshore monopile weldments in air and synthetic seawater

Welded steel structures used in the offshore wind industry are exposed to harsh marine environments, which can result in corrosion-induced fatigue damage. Of particular concern is the heat affected zone (HAZ) of welded joints, a region known for its altered microstructure and mechanical properties, which can significantly influence the initiation and propagation of fatigue cracks. This study investigates the short and long fatigue crack growth rates, and the effect of seawater exposure, for the HAZ in S355 steel weldments. Single-edge notch bend (SENB) specimens are used, with a shallow notch in the HAZ. A series of specimens is immersed in synthetic seawater that is continuously circulated at a controlled temperature to assess the synergistic effects of corrosion and fatigue. The experimental method integrates a novel application of front face strain compliance for monitoring short cracks, alongside an extended back-face strain compliance approach for monitoring long crack propagation. It is concluded that the short fatigue crack growth rate of the HAZ is 2.7 to 3.5 times higher in seawater as compared to air. As the crack propagates and enters into the long crack regime, the ratio decreases to 2.2 times at the transition point of the two-stage crack growth curve and further decreases to 1.5 times when the notch advances towards fracture. The findings indicate that the fatigue crack growth rates documented in standards tend to be on the conservative side. This study significantly enriches the fatigue crack growth data available in literature, which will contribute to a more accurate lifetime assessment offshore wind turbine structures.

Deterioration micro-mechanism of graded aggregates with different gradations under vibratory compaction using X-CT testing

This study aims to explore the compaction deterioration micro-mechanism of high-speed railway graded aggregate (HRGA) fillers and further improve the compaction quality of HRGA fillers, contributing to improving subgrade service performance. Firstly, based on the vibratory compaction experiments, the compaction deterioration macro-characteristics of HRGA fillers with different gradations were revealed from the mechanical properties (i.e., dynamic stiffness Kd and subgrade reaction modulus K20). Secondly, X-ray Computed Tomography (X-CT) testing was conducted based on the multiple typical compaction stages selected from the Kd curve. The internal microstructure (i.e., particles and voids) characteristics within HRGA fillers with different gradations were measured by high-precision image processing approaches. Finally, the evolution characteristics of Kd, K20, and microstructure were used to reveal the compaction deterioration micro-mechanism of HRGA fillers with different gradations, and further explore the relationship between filler gradation and compaction deterioration. The results indicated that compaction deterioration characteristics of HRGA fillers with different gradations could be characterized by the inflection points of Kd and K20 curves. Besides, during compaction deterioration, particle abrasion crushing and the increase in surface edges and corners of the void reduced the stability of the skeleton structure within HRGA fillers with different gradations, resulting in a gradual decrease of Kd and K20. Furthermore, the relationship between Kd, K20, and microstructure with gradation could be quantitatively characterized by quadratic functions. Hence, based on X-CT measurement, it was feasible to reveal the compaction deterioration mechanism of HRGA fillers from macro- and micro-perspectives. This study contributes to establishing a theoretical framework for revealing the compaction deterioration of high-speed railway subgrade fillers and improving the quality of vibratory compaction for on-site subgrade construction.

Flexural performance of concrete reinforced with ultra-high ductility magnesium phosphate cement-based composites and CFRP

With the aim to develop and assess an effective reinforcement technique for concrete beams, the approach of the combination of ultra-high ductility magnesium phosphate cement-based composites (UHDMC) and carbon fiber reinforced polymer (CFRP) was analyzed and established based on the measured parameters, including failure mode, load-deflection curve and feature points. The results showed that, for specimens reinforced by UHDMC alone or the combination of UHDMC and CFRP, several cracks in the concrete layer and multi-cracks in the UHDMC layer were both shown, presenting a ductile failure and three distinct stages in the load-deflection curve. Moreover, compared with the specimens reinforced by CFRP alone and UHDMC alone, the ultimate load and ultimate deflection both were improved in the specimens reinforced by UHDMC and CFRP. Furthermore, the strain distribution of CFRP was symmetrical along both sides of the test specimen, presenting a general law of large in the middle and small in the two ends, and its more and more obvious phenomenon with the increase of the number of CFRP layer. To some extent, the inclination trend of the overall strain of CFRP can be used to determine the location of the weak surface.

An overlooked source of uncertainty in the mass of the Milky Way

ABSTRACT In the conventional approach to decomposing a rotation curve into a set of contributions from mass model components, the measurements of the rotation curve at different radii are taken to be independent. It is clear, however, that radial correlations are present in such data, for instance (but not only) because the orbital speed depends on the mass distribution at all (or, minimally, inner) radii. We adopt a very simple parametric form for a covariance matrix and constrain its parameters using Gaussian process regression. Applied to the rotation curve of the Milky Way, this suggests the presence of correlations between neighbouring rotation curve points with amplitudes of $\lt 10\, \mathrm{km}\, \mathrm{s}^{-1}$ over length scales of 1.5–$2.5\, \mathrm{kpc}$ regardless of the assumed dark halo component. We show that accounting for such covariance can result in a ∼50 per cent lower total mass estimate for the Milky Way than when it is neglected, and that the uncertainty in model parameters increases such that it seems more representative of the uncertainty in the rotation curve measurement. The statistical uncertainty associated with the covariance is comparable to or exceeds the total systematic uncertainty budget. Our findings motivate including more detailed treatment of rotation curve covariance in future analyses.

Condition monitoring of electric vehicle motor testing machine’s Vital components using bagged trees and quadratic SVM: a comparative study

The future of the automotive industry lies in the utilization of electric vehicles (EVs). A crucial component of these EVs is the drive motor. The verification of critical parameters for the electrical motor is considered to be of utmost importance, and this is achieved through the use of a motor testing machine. The motor testing machine is utilized frequently to determine characteristic curve points and the electromagnetic behavior of electric motors under various conditions. However, it has been observed that the presence of a fault in the helical gear setup of the testing machine leads to frequent breakdowns and suboptimal performance, thereby affecting the efficiency of the assembly line in the production of electric vehicles. In light of these observations, the main objective of this research endeavor is to improve the motor test bench apparatus by altering essential design parameters through the utilization of vibration signal analysis and machine learning techniques. Prior to extracting statistical features, vibration signals are obtained at different gear settings. These signals are subsequently categorized using classifiers such as Bagged Trees and Quadratic SVM. Machine learning techniques are utilized to classify the gathered signals as either normal or faulty, both with and without the inclusion of a 0.25 KW load for each condition. The performance of multiple algorithms is evaluated and scrutinized. The results have demonstrated that the Bagged Trees technique outperforms the other algorithm, achieving an impressive accuracy of 95.3%. Consequently, the proposed method presents an adept solution for augmenting the motor test bench’s capability by modifying crucial design parameters.

Dual-threshold control architecture for improved thermal and power management in open-cathode direct methanol fuel cell

A new dual-threshold cascade control scheme is proposed for water management in direct methanol fuel cells. The control architecture is constructed with the goal of adjusting the liquid-level of a methanol solution in an internal storage tank, where this control structure is based on a set point constrained by upper and lower thresholds. The logic of the algorithm is driven by a noninverting and an inverting Schmitt triggers comprising a switching function that sets the master controller on manual mode for periods of time during which the operating temperature of the electricity-generating fuel cell’s stack can be fixed at an optimal value. Automatic control is implemented when either threshold is reached, triggering a level recovery action where the temperature is manipulated to promote or inhibit cathodic evaporative water losses, depending on the existing perturbations. Manual mode is reinstated when a chosen mid liquid-level target is reached. The strategy seeks to avoid water flooding and dry-out states in the device, while ensuring constant power and current production during periods of manual operation. Simulation studies show that the new control method is immune to severe perturbations, which stands in contrast to a standard cascade control scheme that causes significant degradation and unstable electrical performance in the cell under analogous conditions. Unlike the standard cascade control where the operating temperature is seldom close to the optimal operating point, the improved dual-threshold logic is superior such that the desired temperature of operation can be realized during the entire manual mode, enhancing the performance of the variables that critically depend on temperature. The new method realizes a successful power transition from 30 to 40W, demonstrating its ability to meet changes in load demands, where this transfer is implemented by altering the operational temperature from 45°C to 60°C at a constant voltage. The new strategy can be incorporated into a higher-level optimization control layer, where different temperature operating points can be chosen based on user-defined performance criteria. The study focuses on a case of two different points of the polarization curve corresponding to a power of 40W. While the operating point at a current of 2.51A and temperature of 57.5°C has a higher voltage efficiency of 10%, the second point operating at 2.79A and 50°C shows a boost by 7.6% in fuel efficiency over the first point. Hence, a user can choose the optimal operating condition based on specific performance metrics while simultaneously meeting the load demands. Few recommendations are presented to advance this work in the future.

Pearcey universality at cusps of polygonal lozenge tilings

AbstractWe study uniformly random lozenge tilings of general simply connected polygons. Under a technical assumption that is presumably generic with respect to polygon shapes, we show that the local statistics around a cusp point of the arctic curve converge to the Pearcey process. This verifies the widely predicted universality of edge statistics in the cusp case. Together with the smooth and tangent cases proved by Aggarwal‐Huang and Aggarwal‐Gorin, these are believed to be the three types of edge statistics that can arise in a generic polygon. Our proof is via a local coupling of the random tiling with nonintersecting Bernoulli random walks (NBRW). To leverage this coupling, we establish an optimal concentration estimate for the tiling height function around the cusp. As another step and also a result of potential independent interest, we show that the local statistics of NBRW around a cusp converge to the Pearcey process when the initial configuration consists of two parts with proper density growth, via careful asymptotic analysis of the determinantal formulas.

Uniformity of quadratic points

In this paper, we extend a uniformity result of Dimitrov et al. [Uniformity in Mordell-Lang for curves, Ann. of Math. (2) 194(1) (2021) 237–298] to dimension two and use it to get a uniform bound on the cardinality of the set of all quadratic points for non-hyperelliptic non-bielliptic curves which only depend on the Mordell–Weil rank, the genus of the curve and the degree of the number field.

Application of fluctuations in the sound field in inversion of internal solitary wave phase speed

Internal solitary waves propagation perturbing the sound velocity field, causes fluctuations in the sound field. This paper proposes to process the sound pressure data by the Product of the Slope and the even square of the Difference between two points of the acoustic parameter-time curve (PSD). The PSD processed data are processed to time-frequency analysis to extract the frequencies of the fluctuations in sound field. In this paper, numerical simulations and laboratory experiments are carried out on the process of internal solitary wave propagation in the sound field, and the characteristics of the sound field perturbation by internal solitary waves of different amplitudes are investigated. Results are both showing that the method can extract the dominant frequency of fluctuations in the sound field caused by internal solitary waves in real conditions. The method can be applied to the inversion of internal solitary wave phase speed which related to other parameters such as amplitude and characteristic width by theory. It is anticipated that this method can help realize the monitoring of internal solitary waves using acoustic paths.

Enhancing MPPT in Partially Shaded PV Modules: A Novel Approach using Adaptive Reinforcement Learning with Neural Network Architecture

The occurrence of partial shading in solar power systems presents a substantial challenge with widespread implications, sparking extensive research, notably in the field of Maximum Power Point Tracking (MPPT).This study emphasizes the critical process of accurately tracking the maximum power points with the characteristic curves of Photovoltaic (PV) modules under real-time, diverse partial shading patterns. It explores the various stages of the tracking process and the methodologies employed for optimization. While conventional methods have shown effectiveness, they often fall short in swiftly and accurately tracking maximum power points with minimal errors. To address this limitation, this research introduces a novel machine learning approach known as Adaptive Reinforcement Learning with Neural Network Architecture (ARLNNA) for MPPT. The results obtained from ARL-NNA are compared with existing algorithms using the same experimental data. Furthermore, the outcomes are validated through different factors and processing time measurements. The findings conclusively demonstrate the efficacy and superiority of the proposed algorithm in effectively tracking maximum power points in PV characteristic curves, providing a promising solution for optimizing solar energy generation in partial shading patterns. This study significantly impacts various realms of electrical engineering including power engineering, power electronics, industrial electronics, solid state electronics, energy technology and other related field of Engineering and Technology.

A novel and precise method to determine the upper limit of crystallization temperature of basalt melts for the production of continuous basalt fibers

The upper limit of crystallization temperature (Tc) of basalt melt is crucial for the production of continuous basalt fibers (CBFs). However, the precisely measuring Tc for basalt systems has been a challenging and time-consuming task. As a result, there is often a mismatch between the fiber-drawing temperature (Td) and the Tc of basalt melt during CBF production, which hinders the improvement of the mechanical properties and leads to the fiber fracture. To address these limitations, a new approach has been proposed to determine Tc by analyzing the inflection point of the viscosity-temperature curve, This is achieved by fitting an exponential function (y = y0 + A*exp(R0*x)). The results of this viscosity fitting technique were compared to the microstructure and morphology of basalt melts quenched at different temperatures, which were assessed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The findings indicate that the results from XRD and micro-observations are in agreement with the viscosity fitting method. Furthermore, the variations of Tc and Td in binary basalt systems were quantified, and it was revealed that their behavior follows the linear superposition principle based on the mass percentage Wi (i = 1, 2) of the two end members. Empirical formulas have been developed to describe this relationship, which are given as TcW1 × Tc1 + W2 × T c1 and Td = W1 × Td1 + W2 × Td2. These findings not only contribute to the precise measurement of Tc but also provide new insights for modeling the prediction formula of Tc for binary basalt systems.