Monotonic Variation Research Articles

A novel method for detecting tropopause structures based on the bi-Gaussian function

Abstract. The tropopause is an important transition layer and can be a diagnostic of upper-tropospheric and lower-stratospheric structures, exhibiting unique atmospheric thermal and dynamic characteristics. A comprehensive understanding of the evolution of fine tropopause structures is necessary and primary for the further study of complex multi-scale atmospheric physical–chemical coupling processes in the upper troposphere and lower stratosphere. A novel method utilizing the bi-Gaussian function is capable of identifying the characteristic parameters of vertical tropopause structures and providing information on double-tropopause (DT) structures. The new method improves the definition of the cold-point tropopause and detects one (or two) of the most significant local cold points by fitting the temperature profiles to the bi-Gaussian function, which defines the point(s) as the tropopause height(s). The bi-Gaussian function exhibits excellent potential for explicating the variation trends of temperature profiles. The results of the bi-Gaussian method and lapse rate tropopause, as defined by the World Meteorological Organization, are compared in detail for different cases. Results indicate that the bi-Gaussian method is able to more stably and obviously identify the spatial and temporal distribution characteristics of the thermal tropopauses, even in the presence of multiple temperature inversion layers at higher elevations. Moreover, 5 years of historical radiosonde data from China (from 2012 to 2016) revealed that the occurrence frequency and thickness of the DT, as well as the single-tropopause height and the first and second DT heights, displayed significant meridional monotonic variations. The occurrence frequency (thickness) of the DT increased from 1.07 % (1.96 km) to 47.19 % (5.42 km) in the latitude range of 16–50° N. The meridional gradients of tropopause height were relatively large in the latitude range of 30–40° N, essentially corresponding to the climatological locations of the subtropical jet and the Tibetan Plateau.

Nonideal mixing effect based on Cholette’s model on Van de Vusse reaction selectivity dynamics in an isothermal continuous stirred-tank reactor

Abstract The nonideal mixing effect on the Van de Vusse reaction dynamic in a continuous stirred-tank reactor (CSTR) has rarely been studied in literature. This work presents the mixing operation condition and kinetic reaction constant effects on the Van de Vusse reaction selectivity dynamic in an isothermal CSTR based on Cholette’s model. The mixing condition effect is defined using the parameter μ = n/m, where n is the flow fraction to the reactor and m is the dead space fraction in the reactor. In Cholette’s model, μ = 1 and μ ≠ 1 represent, respectively, the ideal and nonideal mixing operations. Herein, the final desired product yield steady state in the phase plane is first constructed under reaction constant and mixing condition combinations, indicating that the larger the μ values, the higher the desired product steady-state yield. In the selectivity dynamic simulations, the phase plane is divided into transient extreme yield region and region of monotonic variation in yield. It is found for the first time that a higher μ value leads to a decrease in the transient maximum selectivity region area and an increase in the transient minimum selectivity region area in the phase plane. Moreover, the trajectory from the start up to the final steady state will be changed due to nonideal mixing. These results have not been published and have direct applications in real reactor design and operation. Since a CSTR with ideal mixing is hardly attainable in practice, our results benefit the real reactor design and startup policy development in the desired product transient maximum yield.

Comparative Analysis of 50 MeV Li3+ and 100 MeV O7+ Ion Beam Induced Electrical Modifications in Silicon Photodetectors

This article investigates the impact of 100 MeV O7+ and 50 MeV Li3+ ions on Silicon Photodetectors, focusing on their electrical characteristics with similar Sn/Se ratios. Elevated ion fluences led to a significant rise in the ideality factor “n”, indicating the presence of Generation-Recombination (G-R) current due to introduced defects, especially those with deep energy levels in the forbidden gap acting as G-R centers. While Ideality factor (n) values decreased for oxygen ions at maximum fluence, they increased for lithium ions, reflecting consistent patterns in series resistance (Rs) and reverse leakage current (IR), attributed to ion-induced defects. Oxygen ions showed a monotonic variation in Rs, whereas lithium ions exhibited a slight reduction at maximum fluence, possibly due to defect annihilation. Despite differing Se values, 50 MeV Li3+ ions demonstrated improved device characteristics, suggesting potential defect annihilation. The ratio of Sn to Se indicated comparable damage contributions from nuclear and electronic energy. Additionally, TRIM computations revealed non-uniform damage distributions, with ions penetrating deep into the substrate, away from the n+/p junction.

Conical bodies with star-shaped transverse contour having the minimum wave drag

The problem of constructing the transverse contour of a conical body having the minimum wave drag in the range of supersonic velocities provided that the length and the volume are preserved is considered. A cone is taken as the initial body, an assumption about locality of the relation between variations in the geometric parameters and the pressure on the surface is made, and the quadratic approximation of this relation is used. The found solution is compared with the results obtained within the framework of the Newton model. These solutions are proposed to combine being based on the assumption of the power-law relation between the radius and the derivative of radius with respect to the angular coordinate. In this case, a class of contours in which half of the cycle consists of the element with monotonic variation in the radius and arc of the circle is distinguished. These contours can be described by specifying a single geometric parameter, namely, the exponent. Using the inviscid perfect gas model, direct numerical optimization of the shape of transverse contour is carried out and the possibility of reducing the wave drag as compared to the star-shaped bodies with plane faces is demonstrated.

Numerical investigation of optical characterization of polycarbonate panels

Polycarbonate panels (PC panels) are state-of-the-art transparent insulating materials widely used in the construction industry due to their cavity structure, which provides exceptional thermal insulation and optimal optical performance. However, the inherent anisotropy of the three-dimensional cavity structure complicates radiative transfer and requires consideration of both azimuth and zenith angles in optical performance evaluation. This aspect has received limited attention in existing research. This study aims to accurately characterize the optical performance of PC panels through numerical simulations. A three-dimensional radiative transfer model based on the discrete ordinate radiation model is developed to solve the radiation transfer equation. The model's independency regarding mesh division, angular discretization, and accuracy is validated. The effects of incidence angle, geometric parameters, and optical properties of PC panels on optical performance are analyzed. The findings reveal a strong correlation between transmittance and absorption with variations in incident zenith and azimuth angles. The transmittance exhibits a consistent monotonic variation expressible as a rational bifunction. Notably, absorption peaks occur within specific solid angle ranges, with increased structural complexity resulting in heightened absorption and greater uncertainty. For conventional PC materials, maximum transmittance ranges from 46.9 % to 73 %, while maximum absorption ranges from 2.3 % to 13.5 %. Increasing absorption coefficients, refractive index, and surface scattering coefficients nonlinearly decrease transmittance while increasing absorption. Additionally, deviations in transmittance and absorption with azimuth angle amplify with an increase in non-horizontal structures. Sensitivity analysis indicates a significant influence of zenith angle on transmittance, and absorption coefficient predominantly affects absorption.

Rough set model of incomplete interval rough number decision systems

The rough set model has been extended to interval rough number decision systems, but the existing studies do not consider interval rough number decision systems with missing values. To this end, a rough set model of incomplete interval rough number decision systems (IIRNDSs) is proposed, and its uncertainty measures are investigated. Firstly, the similarity of two incomplete interval rough numbers (IIRNs) are defined by calculating their optimistic and pessimistic distances of the lower and upper approximation intervals of IIRNs. Then, the rough sets in IIRNDSs are constructed by the induced similarity relation. Next, four uncertainty measures, including approximation accuracy, approximation roughness, conditional entropy, and decision rough entropy are given, which exhibit a monotonic variation with changes in the size of attribute sets, α, and θ. Finally, the experimental results demonstrate the proposed rough set model of IIRNDSs is feasible and effective.

Adiabat-to-Diabat Angle in Seam Space: Renner-Teller-Type and Pseudo-Jahn-Teller-Type Problems.

In this study, we examine the adiabat-to-diabat (ATD) angles for trajectories in 2-dimensional vibrational subspace of the seam space of two degenerate states. In circulating around the tangential touching degeneracy center, the ATD angle is changed by or 0, similar to the Renner-Teller problem and the pseudo-Jahn-Teller problem, respectively. These ATD angle profiles may be indistinguishable from those of circulating multiple conical intersections or a pseudo-Jahn-Teller center. Methods to discern those seemingly indistinguishable cases are proposed. A sharp zigzag variation of the ATD angle is seen as a feature for trajectories that graze a pseudo-Jahn-Teller-type tangential touching center, in contrast to the monotonic steep variation for grazing a conical intersection or a Renner-Teller-type tangential touching center.

New constraints on Triton’s atmosphere from the 6 October 2022 stellar occultation

The atmosphere of Triton was probed directly by observing a ground-based stellar occultation on 6 October 2022. This rare event yielded 23 positive light curves collected from 13 separate observation stations contributing to our campaign. The significance of this event lies in its potential to directly validate the modest pressure fluctuation on Triton, a phenomenon not definitively verified by previous observations, including only five stellar occultations, and the Voyager 2 radio occultation in 1989. Using an approach consistent with a comparable study, we precisely determined a surface pressure of 14.07−0.13+0.21 μbar in 2022. This new pressure rules out any significant monotonic variation in pressure between 2017 and 2022 through direct observations, as it is in alignment with the 2017 value. Additionally, both the pressures in 2017 and 2022 align with the 1989 value. This provides further support for the conclusion drawn from the previous volatile transport model simulation, which is consistent with the observed alignment between the pressures in 1989 and 2017; that is to say, the pressure fluctuation is modest. Moreover, this conclusion suggests the existence of a northern polar cap extended down to at least 45°N–60°N and the presence of nitrogen between 30°S and 0°.

Tunable anomalous Hall effect in Pt/ferrimagnetic insulator bilayer

Ferrimagnetic insulators (FMIs) are regarded as promising candidates for magnonic devices. Nevertheless, unraveling the origin of anomalous Hall effect (AHE) and tuning AHE in heavy metal (HM)/FMI prove challenging as charges exclusively traverse within the HM. Here, we investigate AHE in a Pt/Gd3Fe5O12 (GdIG) bilayer at various temperatures and observe a signal inversion at 180 K. By varying the thickness of GdIG and Pt, we note that AHE signal inversion occurs in all instances except when the Pt thickness is below 3 nm. Moreover, the monotonic variation in the temperature dependence of the coercive field (Hc) indicates that the inversion of the AHE signal is not correlated with the compensation temperature (Tc). Instead, it is attributed to the competition between spin Hall magnetoresistance (SMR) and the magnetic proximity effect (MPE). Furthermore, the precise control over the AHE inversion has achieved through the application of extra in-plane magnetic fields (Hx). Our study clarifies the origins of the AHE in Pt/FMI bilayers, where the interaction between the SMR and MPE governs the direction and magnitude of the AHE. Furthermore, we showcase the ability to control the inversion of the AHE signal by manipulating the extra Hx.

Periodic wave solutions for a KP-MEW equation under delay perturbation

In this paper we investigate the uniqueness of periodic wave solutions for a 4-parametric perturbed KP-MEW equation with local strong delay convolution kernel. Applying the geometric singular perturbation theory, a locally invariant manifold is established in a small neighborhood of the critical manifold to transform the singular perturbed system into a regular one. We prove the monotonicity of the ratio of two Abelian integrals and give all conditions for the uniqueness of periodic wave solutions. Moreover, we find that the amplitude and wavelength of this periodic wave change monotonously following monotonous variation of some parameters included in the perturbed KP-MEW equation as shown as in numerical simulations.

Data sonification of film capacitors

AbstractFilm capacitors are playing an increasingly important role in power‐related fields, driven by the continuous development of dielectric materials and practical needs. Long‐term accumulation has also led to an increasing wealth of data related to film capacitors. Sonification opens up a new way for people to make good use of data from film capacitors. A framework for sonifying film capacitors data based on TwoTone is presented. Based on the analysis and discussion, it is clear that the sonification results can easily represent the monotonic variation pattern of film capacitors data. What's more, the sonification results increase the possibility that people pay attention to the changing trend of film capacitors data when there is no significant difference in the visual perception of the data. In addition to providing a new way of music generation of electrical equipment, the method proposed is expected to contribute to theory reference in typical scenarios, such as factory calibration of film capacitors, monitoring of film capacitor operation status, and presentation of statistical data of film capacitors' dielectric materials, which will help us to better understand the distribution characteristics of polymer films.

Mathematical model for the plastic flow and ductile fracture of polycrystalline solids

It is mathematically shown that ductile fracture after finite plastic strain is a necessary consequence of the polycrystalline nature of the materials. A closed–form equation for the plastic strain to fracture of a fine–grained polycrystal with no voids is derived. The mathematical model for the plastic deformation is grounded on the physical hypothesis that adjacent grains slide with a relative velocity proportional to the local shear stress resolved in the plane of the shared grain boundary, when exceeds a finite threshold. Hence plastic flow is governed predominantly by the in–plane shear forces making grain boundaries to slide, and the induced local forces responsible for the continuous grain reshaping are much weaker. The process is shown to produce a monotonic hydrostatic pressure variation with strain that precludes a stationary flow. The hydrostatic pressure dependence on strain has two solutions. One of them leads to superplasticity, the other one is shown to diverge logarithmically at a finite fracture strain and then represents ductile behaviour. Emphasis is done in the mathematical aspects of the deformation of the polycrystal up to the initiation of fracture. Although theoretical predictions agree well with mechanical tests of commercial alloys, technical issues like the effects of the presence and evolution of porosity and other imperfections, or how fracture evolves after initiation are left for a more specific communication.

Experimental study on a parallel optical fiber Sagnac loops-based sensor with the advantages of both high sensitivity and ultra-wide measurement range

The Vernier effect (VE) in optical interferometers has been used to improve the sensitivity in the measurements of strain, temperature, refractive index, etc. However, as the wavelength shifts beyond a free spectral range (FSR), it is difficult to determine the magnitude of the physical quantity and the measurement range is usually narrow. To overcome this problem, we constructed a fiber optic sensor combining two parallel Sagnac interferometers (PSIs) with a fiber Bragg grating (FBG). The sensitivity of temperature and strain measurements were enhanced about 5 times due to the VE effect in PSIs. FBG spectrum, which showed a monotonic and linear variation trend along with the variation of strain and temperature, was used to estimate the magnitude of the physical quantity beyond the FSR. Finally, an average strain sensitivity of −104.4 pm/µε was obtained in a wide measuring range of 0–5440 µε, while an average temperature sensitivity of 6.12 nm/°C was obtained in the temperature range of 2–58 °C. The measurement range has been extended 6 times and 4 times respectively compared to a single FSR. The integration of PSIs and FBG sensors offers not only high sensitivity, but also a wide measuring range. It can be used in many areas including medical equipment, automotive, and aerospace to make accurate strain and temperature measurements.

Effects of low ambient pressure on the flame characteristics of ethanol−gasoline blended pool fire

The flame characteristics of Ethanol−Gasoline pool fire with different blend ratios were experimentally studied in a large−scale pressure−controlled compartment with ambient pressure of 40 kPa, 61 kPa, 80 kPa, and 101 kPa. The flame height, centerline temperature, and radiant heat flux were measured. The flame height increases notably with decreasing ambient pressure, but the flame temperature (intermittent and plume regions) slightly increases. With increasing ethanol ratio, the flame height and temperature decrease monotonously under large ambient pressure, but show a non−monotonic variation with a peak value at low ambient pressure and ethanol ratio of 10 %∼20 %. Heskestad’s flame height and temperature correlations were not suitable for blends pool fire under low ambient pressure. The new modified model for flame height correlation with ambient pressure and combustion heat of blends, and flame temperature correlation with flame height, fuel property parameter, and ambient pressure were developed with a better prediction. The addition of ethanol and decrease of ambient pressure led to the reduction of radiation loss from flame, and the non−monotonic variation with a peak value also occurs with increasing ethanol ratio at relatively large ambient pressure and ethanol ratio of 20 %. A new modified model based on the classical solid flame model was also developed to predict the radiative fraction, considering the ambient pressure, stoichiometric ratio, and the ratio of the combustion heat to the vaporization heat.

A method for fault location using the phase difference of current in the protective layer at both ends of a cable section

This paper is based on the distribution characteristics of the protective layer current under the fault state of high-voltage cables, and discovers the monotonic variation law between the fault point position and the power frequency phase difference of the protective layer current at both ends of the cable fault section. A method for fault location using the phase difference of the protective layer current at both ends of the cable section is proposed. For a long cable line composed of multiple complete cross-connected sections, the cross-connected section can be located through the current power frequency phase difference P (section) at both ends of the metal sheath section, just like the section positioning within the complete cross-connected section. If P (section) ∈ (90°, 270°), then the section is a fault section; otherwise, it is a non-fault section. Finally, the relationship curve between the power frequency phase difference of the protective layer current at both ends of the fault section and the distance from the fault point is used to determine the fault location.

Lattice‐mediated room temperature magnetoelectric effect in (1‐y)BiFe1‐xCrxO3‐yBaTi1‐xMnxO3 solid solutions

AbstractElectric field (E) control of magnetism is a persistent challenge in low‐power consumption spintronic devices. A promising way to realize this control is to use the converse magnetoelectric (ME) effect in insulating multiferroics. Here, we report considerable and repeatable E‐modulated magnetization (M) at room temperature and even at 350 K via the significantly enhanced converse ME effect near the morphotropic phase boundary (MPB) of the Cr‐Mn co‐doped (1‐y)BiFe1‐xCrxO3‐yBaTi1‐xMnxO3 (0.15 ≤ y ≤ 0.33, 0 ≤ x ≤ 0.03) solid solutions. In situ X‐ray diffraction and Raman scattering experiments at different applied E for the sample near the MPB (i.e., y = 0.27, x = 0.03) show E‐induced shift, broadening, and splitting in the {002}PC reflection, as well as a nearly monotonous variation in intensity of several phonon modes with E, reminiscent of the E‐dependent M behavior. These results indicate that both E‐induced lattice distortion and phase transformation dominate the converse ME effects in these samples. Our demonstration of the E‐regulation of magnetism via the E‐sensitive crystal structures in designed insulating multiferroics near MPB may suggest a potential route to obtain efficient low‐power spintronic devices.

Parabolic Viscosity Behavior of NaCl-Thickened Surfactant Systems upon Temperature Change.

The viscosity of household care products plays an important role in pleasant delivery using consumer experience at home. A novel solution to mitigate the sharp rising of viscosities at low temperatures of detergents was proposed. By designing the formulation of the surfactant blend, formulators can achieve acceptable viscosity profiles in the temperature range encountered in daily life. The verification and modulation of formulas bearing parabolic viscosity-temperature behavior were systematically studied, including in single, binary, and ternary systems, based on the modulation of sodium ethoxylated alkyl sulfate (AES) by other anions, zwitterions, and nonions. The R ratio theory was used to have a better understanding of the molecular assembly of surfactants behind the parabolic behavior exhibited in rheology analyses. One of the key findings is that the parabolic viscosity-temperature phenomenon could be easily observed in the highly hydrated ethoxylated anionic systems like AES-based systems. For those anions lacking ethoxylation, especially sodium linear alkylbenzene sulfonate (LAS), the monotonic variation of hydration affinity with temperature led to the disappearance of parabola in the observed temperature window (>0 °C). Moreover, salinity played an important role in the hydration affinity of the polar group and the interaction between the hydrophilic headgroups. A balanced salinity should be optimized to modulate the hydration affinity in a desired range so that the parabola could be easily tuned within the target temperature region. These findings provide opportunities for the formulators in the household care industry to design products with better pourability through carefully selecting a combination of surfactants and fine-tuning their ratios to improve consumer use experience, especially in winter.

Mechanical behaviour of steel-concrete joint in hybrid girder cable-stayed bridge

A steel-concrete joint section test model was constructed based on a mixed-scale ratio of the Lancang River hybrid girder cable-stayed bridge in Jinghong City, Yunnan Province. The internal forces and test loading values during normal operations were determined using finite element analysis. The performance was analysed by determining the mechanical indicators at key positions during the loading process. A finite element model of the test girder section was established to analyse the force transmission mechanism of the studied steel-concrete joint section. The test results showed that the centroid of the section moved upward during force transfer from the concrete to the steel girder. The relative slippage at the steel-concrete interface resulted in local unloading and an uneven distribution of longitudinal stresses in the crosswise direction. In addition, the cooperative bearing of the steel-concrete joint girder was transformed to a single bearing of the concrete girder, leading to a monotonic variation of stresses in the web plate. The simulation results showed that the surface plate force-sharing ratio of the composite bridge was the highest. In addition, the force-sharing ratios under the axial force and bending moment scenarios were 57.65% and 78.91%, respectively, indicating that the investigated steel-concrete joint demonstrated good stiffness transition stability. Furthermore, four force transfer types were identified in the steel-concrete joints. The research outcomes provide a fundamental basis for the rational design of joint components applied in hybrid girder cable-stayed bridges.

Chaotic dynamics of an extended Duffing-van der Pol system with a non-smooth perturbation and parametric excitation

Abstract Chaotic dynamics of a fifth-order extended Duffing-van der Pol system with a non-smooth periodic perturbation and parametric excitation are investigated both analytically and numerically in this paper. With the Fourier series, the system is expanded to the equivalent smooth system. The Melnikov perturbation method is used to derive the horseshoe chaos condition in the cases of homoclinic and heteroclinic intersections. The chaotic features for different system parameters are investigated in detail. The monotonic variation of the coefficients of parametric excitation and non-smooth periodic disturbance is found. With numerical methods, we validate the analytical results obtained by Melnikov’s method. The impact of initial conditions is carefully analyzed by basins of attraction and the effect of non-smooth periodic disturbance on the basin of attraction is also investigated. Besides, the effect of different parameters on the bifurcation pathway into chaotic attractors is examined.

Python programs to apply regularized derivatives in the magnetic tilt derivative and gradient intensity data processing: A graphical procedure to choose the regularization parameter

The Tikhonov regularization parameter is a key parameter controlling the smoothness degree and oscillations of a regularized unknown solution. Usual methods to determine a proper parameter (L-curve or the discrepancy principle, for example) are not readily applicable to the evaluation of regularized derivatives, since this formulation does not make explicit a set of model parameters that are necessary to implement these methods. We develop a procedure for the determination of the regularization parameter based on the graphical construction of a characteristic “staircase” function associated with the L2-norm of the regularized derivatives for a set of trial regularization parameters. This function is independent of model parameters and presents a smooth and monotonic variation. The regularization parameters at the upper step (low values) of the ''staircase'' function provide equivalent results to the non-regularized derivative, the parameters at the lower step (high values) leading to over-smoothed derivatives. For the evaluated data sets, the proper regularization parameter is located in the slope connecting these two flat end-members of the staircase curve, thus balancing noise amplification against the amplitude loss in the transformed fields. A set of Python programs are presented to evaluate the regularization procedure in a well-known synthetic model composed of multiple (bulk and elongated) magnetic sources. This numerical approach also is applied in gridded aeromagnetic data covering high-grade metamorphic terrains of the Anápolis-Itauçu Complex in the Brasília Fold Belt central portion of Tocantins Province, central Brazil, characterized by multiple magnetic lineaments with different directions and intersections which are associated with shear zones, geologic faults, and intrusive bodies. The results obtained from the regularization procedure show efficiency in improving the maps of filtered fields, better tracking the continuity of magnetic lineaments and general geological trends. The results from the application in the Brasília Fold Belt enhance the importance and broader coverage of the Pirineus Zone of High Strain.