Sinusoidal Function Research Articles

Linear photogalvanic effects in monolayer ternary metallic compound Na2MgSn.

The linear photogalvanic effect (LPGE) is investigated by using the non-equilibrium Green's function (NEGF) technique combined with density functional theory (DFT) in monolayer Na2MgSn. We consider the cases of three different central regions, which are pure Na2MgSn, Na-vacancy, and Pb-substituted. It is found that both pure and defective Na2MgSn monolayers induce photoresponse under linearly polarized light. The photoresponse varies periodically as a form of either sinusoidal or cosinoidal function of the polarization angle. In the near-infrared and visible ranges, the photoresponse is more sensitive to the long wave range of visible light. In the case of single-atom defects, the photoresponse with Na-vacancy is larger than that of pb-substitution defects. Compared with the other two central regions, the maximum extinction ratio (ER) of Na-vacancy is larger, so it has higher polarization sensitivity. When the location of Na-vacancy is adjusted, the photoresponse changes obviously, and the Na 1*- vacancy has the largest photoresponse. With the increase of the Na-vacancy concentration, the photoresponse changes nonlinearly but is smaller than that of a single vacancy. A small bias voltage can greatly improve the photoresponse. Our results suggest an effective method to enhance the photoresponse and show the promise of Na2MgSn monolayers in optical detection.

Enhancing thermal stability and filtration control for water-based drilling fluid using viscosifier polymers and potassium chloride additives

Drilling operations conducted under high-pressure and high-temperature conditions present significant challenges for modern drilling advancements. Downhole temperatures can significantly impact the stability of water-based mud (WBM) properties, leading to costly issues and non-productive time resulting from drilling instabilities. To mitigate these issues, it is crucial to employ high-temperature-resistant additives in such operations. This study aimed to examine the influence of temperature on the stability of commonly used polymer types in water-based mud drilling operations. A series of laboratory experiments were conducted to investigate changes in normal mud properties following exposure to temperatures ranging from 79 to 350 °F. Two different mud polymers were used, including two viscosifier polymers (Flowzan - type A and Xanthan gum - type B), with varying concentrations of potassium chloride (KCl). Rheological analysis revealed that Polymer A exhibited superior performance as most mud properties, including viscosity, yield point, and gel strength, were significantly affected at different temperatures. However, plastic viscosities fell below the minimum recommended range of 8 cP for both polymers. At 250 °F, Polymer A's apparent viscosity of WBM was enhanced by 87%, 100%, and 120% with 3%, 5%, and 7% concentrations of KCl, respectively. For Polymer B, at 200 °F, it was improved by 118%, 112%, and 106%. The addition of KCl to the viscosifier polymers enhanced the thermal stability of the drilling fluid within the operating temperature range of 250–350 °F. Gel Point (10-min) remained below the recommended 35 lb/100 ft2 for all KCl concentrations of both polymers, while Gel Point (10-s) remained below the recommended 15 lb/100 ft2 for temperatures above 200 °F. Three other polymers were studied for filtration control without any KCl concentration, namely Bio Pac (type C), Mil Pac Xlo (type D), and Perma Loss (type E). Although API fluid loss remained below the recommended 15 cm3 for all the polymers, filtration control, and cake analysis demonstrated that Polymer C exhibited superior performance compared to the others. It also displayed thermal stability and cake thickness below the recommended 0.1 in up to temperatures below 250 °F. A novel sinusoidal correlation function is fit to experimental data, which can be used for training machine learning approaches.

Investigation of aerodynamic performance of Clark-Y airfoil with more realistic tubercle model and internal slots

An experimental study is conducted to research the combined effect of leading-edge (LE) tubercles and internal slots on the Clark-Y airfoil at Reynolds numbers (Re) of 5.0×104, 7.5×104, and 1.0×105 for angles of attack ranging from 0° to 30°. The Clark-Y is a cambered airfoil that performs well at low and medium Reynolds numbers, having a maximum thickness of 11.7% at 28% of the chord. Five different test models are the subjects of experiments, one of which is the baseline. The other test models are the Wavy model, which has LE tubercles, and the Wavy with three different slot positions: the Wavy-LES (leading-edge slot), the Wavy-MS (middle slot), and the Wavy-TES (trailing-edge slot). The LE tubercle geometry is formed by the sum of two sinusoidal wave functions with a realistic approach. In the present work, experimental studies are performed through force measurements, and detailed information on a 3-dimensional flow field is obtained by a surface-oil flow visualization technique. Force measurements indicate that the Wavy model delays stall and exhibits smoother stall behavior compared to the baseline. Moreover, the findings show that the lift coefficient (CL) of the Wavy model deteriorates in the pre-stall region with the inclusion of the internal slots but improves significantly in the post-stall region. Maximum improvement in CL in the post-stall region was achieved by 60% in Wavy-LES at Re of 5.0×104 as compared to the baseline. At Re of 5.0×104, Wavy and Wavy-MS present a better lift-to-drag ratio (CL/CD) than the other models in the pre-stall region, whereas the baseline is the best at Re of 1.0×105. The best CL/CD is achieved by Wavy-LES in the post-stall region, regardless of the Reynolds numbers. The variation of flow characteristics relevant to aerodynamic performance is revealed by surface oil flow visualization for all tested models.

Spontaneous periodic polarization wave in helielectric fluids.

By analogy with spin waves in ferromagnetic systems, the polarization (or dipole) wave is the electric counterpart that remains elusive. Here, we discover that the helielectricity, i.e. a polarization field with helicoidal helices that corresponds to a quasi-layered chiral nematic environment, causes a spontaneous formation of large-scale polarization waves in the form of the sinusoidal function. Both experimental and theoretical analyses reveal that the polarization ordering over a threshold polarization strength violates the inherent periodicity of the polarization helices, thus penalizing the compression energy. It drives a second-order structural transition to a periodically modulated polarization wave state. The roles of chirality and confinement condition are discussed.

An investigation of complex fuzzy sets for large-scale learning

Complex fuzzy sets are an extension of type-1 fuzzy sets with complex-valued membership functions. Over the last 20 years, time-series forecasting has emerged as the most important application of complex fuzzy sets, with neuro-fuzzy systems employing them shown to be accurate and compact forecasting models. In the complex fuzzy sets literature, two dominant approaches to designing forecasters can be observed: sinusoidal membership functions versus complex-valued Gaussian membership functions. To date, however, there has never been a systematic investigation that compares the performance of these two membership types (or their combination) within a common architecture.We propose a new neuro-fuzzy architecture using complex fuzzy sets that has been designed for large-scale learning problems. This architecture employs randomized learning to speed up network training. In designing this architecture, we empirically compared sinusoidal complex fuzzy sets and complex Gaussian fuzzy sets. Across multiple variations of the architecture, we find that the complex Gaussian fuzzy sets lead to significantly more accurate forecasts on moderate-to-large time series datasets, while still keeping the overall size of the network compact.

A candidate of binary black hole system in AGN with broad Balmer emission lines having quite different line widths

ABSTRACT In this paper, a candidate of sub-pc binary black hole (BBH) system is reported in SDSS J1257+2023 through different properties of broad Balmer emission lines. After subtractions of host galaxy contributions, Gaussian functions are applied to measure emission lines in SDSS J1257+2023, leading line width (second moment) 760 km s−1 of broad H β to be 0.69 times of line width 1100 km s−1 of broad H α, quite different from normal line width ratio 1.1 of broad H β to broad H α in quasars. The quite broader component in broad H α in SDSS J1257+2023 can be confirmed with confidence level higher than 5σ through F-test technique, through different model functions applied to measure emission lines. The broad Balmer emission lines having different line widths can be naturally explained by a BBH system with different obscurations on central two independent broad emission line regions. Meanwhile, through Zwicky Transient Facility (ZTF) light curves and corresponding phase folded light curves well described by sinusoidal function, BBH system expected optical quasi-periodic oscillations (QPOs) can be detected with periodicity about 1000 d, confirmed with confidence level higher than 3σ by generalized Lomb–Scargle periodogram. And through Continuous AutoRegressive process simulated light curves, confidence level higher than 2σ can be determined to support the optical QPOs in SDSS J1257+2023 not from intrinsic AGN activities, although the ZTF light curves have short time durations. Moreover, through oversimplified BBH system simulated results, studying different broad Balmer lines as signs of BBH systems in normal quasars with flux ratios around 4 of broad H α to broad H β could be done in near future.

Memristor initial-offset boosting and its bifurcation mechanism in a memristive FitzHugh-Nagumo neuron model with hidden dynamics

Electromagnetic induction plays a vital role in impacting the neuron dynamics, since the electromagnetic induction is triggered alongside with the complex interaction of membrane potential and various ions transport. In other words, the electromagnetic induction is reversely subjected to the membrane potential fluctuation and ions distribution. Flux-controlled memristor described by flux and voltage has been employed to restrict the electromagnetic induction effect. This paper presents a flux-controlled memristor with sinusoidal mem-conductance function and hyperbolic tangent function modulated input. The memristor can availably reflect the non-uniform ions distribution inside and outside neuron membrane. Then, an improved memristive FitzHugh-Nagumo (mFHN) neuron model is built to explore the dynamical effect of the memristive electromagnetic induction. Numerical simulations and theoretical analysis are performed, which reveal that the mFHN neuron model possesses no equilibrium point and can generate abundant hidden dynamics. Interestingly, hidden coexisting behavior is triggered by memristor initial-offset boosting, which evokes the emergence of infinitely hidden coexisting firing patterns. Besides, bifurcation mechanism of the memristor initial-offset boosting behavior is theoretically analyzed. Furthermore, PowerSIM-based (PSIM-based) analog circuit simulations and microcontroller unit based (MCU-based) digital experiments are executed, the captured results perfectly verify the correctness of numerical results and the feasibility of analog/digital hardware experiments.

Methods to Estimate the Channel Delay Profile and Doppler Spectrum of Shallow Underwater Acoustic Channels

In this paper, we present the methods to detect the channel delay profile and the Doppler spectrum of shallow underwater acoustic channels (SUAC). In our channel sounding methods, a short impulse in form of a sinusoid function is successively sent out from the transmitter to estimated the channel impulse response (CIR). A bandpass filter is applied to eliminate the interference from out-of-band (OOB). A threshould is utilized to obtain the maximum time delay of the CIR. Multipath components of the SUAC are specified by correlating the received signals with the transmitted sounding pulse with its shifted phases from 0 to 2Π. We show the measured channel parameters, which have been carried out in some lakes in Hanoi. The measured results illustrate that the channel is frequency selective for a narrow band transmission. The Doppler spectrum can be obtained by taking the Fourier transform of the time correlation of the measured channel transfer function. We have shown that, the theoretical maximum Doppler frequency fits well to that one obtained from measurement results.

A general method for generating multi-scroll and multi-wing chaotic systems and its implementation of attractor reproduction

Abstract In comparison to traditional chaotic systems, the multi-scroll and multi-wing chaotic systems are more complicated. The design and execution of sophisticated multi-scroll or multi-wing chaotic attractors attract a lot of attention. However, these constructed nonlinear functions cannot be applied to extended multi-scroll and multi-wing attractors at the same time. To this end, this paper proposes a new function which can be used to generate multi-scroll and multi-wing chaotic attractors in both double-scroll and double-wing chaotic systems. Using this function, multi-scroll and multi-wing chaotic systems can be constructed directly without relying on whether the chaotic system has some symmetry (odd symmetry or even symmetry). The construction method presented is generally applicable to chaotic systems with multi-scroll and multi-wing self-excited attractors.The main point of this method is as follows: firstly, the piecewise linear (PWL) saturation function is nested within the cosine nonlinearity function , and the resulting nested COS-PWL function. Secondly, to enable the expansion of multi-wing and multi-scroll, the nested COS-PWL function is incorporated into the double-wing and double-scroll systems in different manners. The maximum Lyapunov exponent (MLE) and the bifurcation diagram route for increasing the number of wings and scrolls confirm the feasibility and effectiveness of the method. Finally, the three-element method is used to determine a Sinusoidal function, which can generate attractor self-reproduction in the corresponding dimension by replacing the state variables of the multi-scroll and multi-wing systems, so that an infinite number of coexisting attractors can be obtained by simply changing the initial values of the variables, i.e., multiple stability can be generated.

Dynamics of two-level laser models with cavity loss modulation and delayed feedback

In 1982, Arecchi et al. [Phys. Rev. Lett. 49, 1217 (1982)PRLTAO0031-900710.1103/PhysRevLett.49.1217] proposed a simple two-level laser model to interpret the first evidence of chaos and generalized multistability in a Q-switched CO2 laser. In this framework, laser dynamics is described by means of a set of two ordinary differential equations for the photon number and the population inversion between the two resonant levels. A sinusoidal function accounts for cavity loss modulation. In this work, we first prove the existence of a periodic orbit for the original two-level non-autonomous laser. Then, we transform this model into a four-dimensional autonomous dynamical system to provide a mathematical analysis that confirms the seminal results already obtained. Finally, by replacing the sinusoidal loss modulation with a delayed function of photon number, we confirm the occurrence of chaos and multistability for such a delayed model with delay times of the order of the reciprocal of the modulation frequencies.

An automatic quadrature method for semi-infinite integrals of exponentially decaying functions and its Matlab code

For the integral of a function f over a semi-infinite interval [0,∞) with f(x) decaying exponentially as x→∞, an automatic quadrature scheme is constructed and implemented in Matlab. Three limit formulae of Clenshaw–Curtis-type rules in our recent work (Numerical Algorithms, vol.90, 2022, pp.3–30) are exploited that converge fast for analytic functions. Each formula is expressed by a weighted infinite sum of function values at nodes and so its truncated finite sum is used. The best of the three formulae in accuracy is used as an approximation whose error is estimated with other two formulae and no additional function evaluations, since nodes of the other formulae are included in those of the best one. Numerical results indicate that our automatic scheme is better in performance than the QUADPACK routine for several types of test integrals. Particularly, it copes quite well with oscillatory integrals including the sinusoidal function and/or the Bessel function that are known to be difficult to approximate.

Distributed prescribed‐time leader‐following formation control for second‐order multi‐agent systems with mismatched disturbances

AbstractThis article investigates the distributed prescribed‐time formation control problem for the second‐order multi‐agent systems (MASs) subject to matched and mismatched disturbances in time‐varying formation case. As a stepping stone, novel distributed estimators are first proposed to accurately estimate the position and velocity information of the leader within prescribed time. Subsequently, the nominal control protocol is presented for the MAS in the absence of the disturbances to deal with the time‐varying formation control problem, and the prescribed‐time stability of the system is guaranteed. For system subject to matched and mismatched disturbances, the observer‐based integral sliding mode formation control protocol is then presented such that the desired trajectories can be tracked and the desired patterns can be achieved within the prescribed settling time. By adopting the sinusoidal function to the control scheme, the singularity‐like problem is solved if there exist measurement errors in the agents. Finally, a numerical simulation example utilizing unmanned aerial vehicles modeled by Simscape and Solidworks is presented to show the efficiency of the proposed scheme.

Novel robust approach–based dynamic global terminal synergetic tracking control for uncertain second-order systems: Wind turbine system and power converter applications

This article provides a systematic approach for synthesizing a novel robust synergetic control mechanism. This controller employs a dynamic global terminal synergetic surface with additional sinusoidal function. The overall macrovariable gives the system a rapid approaching rate, maintains the finite time stability, and provides a chattering-free control law. The stability analysis is validated for any uncertain second-order system via indirect approach of Lyapunov theorems. Furthermore, a hyperbolic tangent nonlinear disturbance observer is designed in order to estimate any lumped disturbance. The feasibility and the effectiveness of the proposed composite control law is tested and evaluated through simulations for simple model, wind turbine system and DC-DC buck converter. Finally, the simulation results show that the presented dynamic global terminal synergetic control–based hyperbolic tangent nonlinear disturbance observer can effectively reject the disturbances, enhance the robustness, and guarantee the tracking accuracy and rapidity.

Polar Codes and a M-ary Modulation-Based OFDM-PLC System

Power Line Communication (PLC) serves as a medium for communication over power lines, utilizing the existing power grid for information transmission. It offers a low-cost, highly scalable signal transmission method and has the potential to become the preferred technology for providing broadband in smart homes, offices, and smart grids. However, noise in the power line channel, especially impulse noise, seriously affects the communication quality of PLC. In this paper, we establish an OFDM-PLC system with higher-order modulation and polar codes. The higher-order QAM or APSK modulation technique is employed to increase the signal transmission rate and the system performance is analyzed. To combat the impulse noise in the PLC channel, we first model it using a superposition of multi-damping sinusoidal functions and then introduce the polar coding scheme to suppress the impulse noise in the system, thereby improving the transmission reliability. Simulation results verify that the proposed polar coding scheme based on the OFDM-PLC system can improve the Bit Error Rate (BER) performance of PLC channel transmission under impulse interference.

Nonlinear swing-down control of the Acrobot: Analysis and optimal gain design

In this paper, we address the swing-down control of the Acrobot, a two-link planar robot operating in a vertical plane with only the second joint being actuated. The control objective is to rapidly stabilize the Acrobot around the downward equilibrium point, with both links in the downward position, from almost all initial states. Under the conditions of no friction and measurability of only the angle and angular velocity of the actuated joint, we present a sinusoidal-derivative (SD) controller. This controller consists of a linear feedback of the sinusoidal function of the angle of the actuated joint and a linear feedback of its angular velocity. We prove that the control objective is achieved if the sinusoidal gain is greater than a negative constant and the derivative gain is positive. We establish crucial relationships between the relative stability of the Acrobot under the SD controller and its physical parameters, presenting analytically all optimal control gains. These gains minimize the real parts of the dominant poles of the linearized model of the resulting closed-loop system around the downward equilibrium point. We demonstrate that the resulting dominant closed-loop poles can be double complex conjugate poles, or a quadruple real pole, or a triple real pole, depending on the Acrobot’s physical parameters. Simulation studies indicate that the proposed SD controller outperforms the derivative (D) controller in rapidly stabilizing the Acrobot at the downward equilibrium point.

Enhanced performance in proton exchange membrane fuel cell with the twisted parallel micro-channel for flow field

The mass transfer efficiency of reaction gas in proton exchange membrane fuel cells (PEMFC) has a great impact on its performance, and the flow field is another important factor affecting the mass transfer performance. A kind of twisted parallel flow field (TPFF) with parallelogram equal cross-sectional area and gradually changing shape along the gas flow direction is presented in this paper. The position of each vertex of a parallelogram changes as a sinusoidal function along the flow direction. The output power density, oxygen concentration, current density, gas flow velocity, and water saturation were compared between TPFF and conventional parallel flow field (CPFF). According to the research results, the gas flow velocity of TPFF is greater than that of CPFF at Channel-GDL interface, the channel is higher than that of the CPFF, which can effectively alleviate flooding. Oxygen is more easily diffused from the bulk phase to the membrane electrode due to the decrease of the mass transfer impedance of oxygen in the TPFF. The oxygen content in membrane electrode is higher than CPFF when the fuel cell operates in the diffusion-polarized zone. Compared with the CPFF, the TPFF fuel cell has better output performance, and the maximum output power is increased by 8%. In addition, due to increasing oxygen transmission efficiency, the uniformity of the reaction is enhanced, so that the low current density region is controlled and the uniformity is improved.

MTR-SAM: Visual Multimodal Text Recognition and Sentiment Analysis in Public Opinion Analysis on the Internet

Existing methods for monitoring internet public opinion rely primarily on regular crawling of textual information on web pages but cannot quickly and accurately acquire and identify textual information in images and videos and discriminate sentiment. The problems make this a challenging research point for multimodal information detection in an internet public opinion scenario. In this paper, we look at how to dynamically monitor the internet opinion information (mostly images and videos) that different websites post. Based on the most recent advancements in text recognition, this paper proposes a new method of visual multimodal text recognition and sentiment analysis (MTR-SAM) for internet public opinion analysis scenarios. In the detection module, a LK-PAN network with large sensory fields is proposed to enhance the CML distillation strategy, and an RSE-FPN with a residual attention mechanism is used to improve feature map representation. Second, it proposes that the original CTC decoder be replaced with a GTC method to solve earlier problems with text detection at arbitrary rotation angles. Additionally, the performance of scene text detection for arbitrary rotation angles is improved using a sinusoidal loss function for rotation recognition. Finally, the improved sentiment analysis model is used to predict the sentiment polarity of the text recognition results. The experimental results show that the new method proposed in this paper improves recognition speed by 31.77%, recognition accuracy by 10.78% on the video dataset, and the F1 score of the multimodal sentiment analysis model by 4.42% on the self-built internet public opinion dataset (lab dataset). The method proposed provides significant technical support for internet public opinion analysis in multimodal domains.

An analytical approach to model transverse inter-fibre fracture evolution in cross-ply carbon fibre reinforced polymers laminates under a three-point bending test

The prerequisite to equip structures with in situ electrical health monitoring systems in a meaningful manner is to estimate potential damage locations. In this context, an analytical approach to model the spatial and temporal evolution of transverse inter-fibre fractures (IFF) is exemplified for [Formula: see text] cross-ply laminates under three-point bending. The model is based on the tensile load in the bottom 90°-layer. The effective stress is computed directly from the specimen displacement, whereas the strength is considered to be periodically distributed due to material inhomogeneities along the specimen. The continuous comparison between the sinusoidal strength function and the effective stress allows modelling progressive damage in form of IFF. A modified Hann window is used to consider their effect to the bottom 90°-layer. Experiments with the same configuration are performed and the observed IFF evolution is used to tune the model parameters in an optimisation procedure, e.g., the peak separation of the sinusoid and the length of the Hann window. The comparison between model and experiment shows a high level of agreement. The model is thus capable to reproduce experiments with minimal computational effort. This makes it highly suitable as input for electrical monitoring models that rely on the continuous damage evolution of the investigated structure. In its current form, the model is limited to the specified configuration. However, the simple analytical approach allows it to be easily adapted. It is furthermore shown that progressive composite damage in terms of spatial and temporal evolution can be accurately described using an analytical approach.

Improved calibration of rf cavities for relativistic electron beams: Effects of secondary corrections and experimental verification

In the aspect of longitudinal beam bunching, the bunching strength can be controlled by the rf cavity phase and voltage. However, these machine parameters are different from those that interact with the beam itself. In order to gain control of the beam-cavity interaction, cavity calibration must be performed. Furthermore, it relies on fitting the beam energy gain versus cavity phase to a calibration function. Under the conventional assumption of relativistic beam conditions, the calibration function is a first harmonic sinusoidal function (a sinusoidal function with a period of $2\ensuremath{\pi}$). However, this expression is insufficient for a high-voltage bunching cavity. Due to beam acceleration inside the cavity, an energy bias and a second harmonic function should be included to modify the conventional calibration function, even for a relativistic electron beam. In this paper, we will derive this modification and provide a comparison to both the Coherent Electron Cooling Experiment and the impact-t simulation, respectively.

Scattering from an electric–magnetic anisotropic rough interface

Scattering from a rough interface between a simple isotropic medium and a uniaxial lossy medium is analyzed using the first-order perturbation theory (PT) and the small slope approximation (SSA). We consider a more generic uniaxial lossy medium exhibiting electric and magnetic anisotropy and an arbitrarily oriented optic axis. Scattering from the rough interface of such a medium is analyzed by assuming both deterministic sinusoidal function and a Gaussian distribution for the surface roughness. We also study the coherent and incoherent intensities employing both the PT and the SSA. The impact of surface roughness, anisotropy and material losses on scattering characteristics is examined. We show that the parameters describing the surface roughness, i.e., height, period, and slope may add significant contribution to the electromagnetic scattering from the anisotropic interface.