Constant Time Research Articles

An explicit improved meshless numerical manifold method for dynamic crack propagation

Accurately simulating the dynamic propagation of cracks is critical to investigating the mechanisms of rock fracture under dynamic loading. The meshless numerical manifold method, characterized by its node-based interpolation approximation akin to the meshless method and the dual-cover of numerical manifold method, is particularly suitable for crack analysis and has been successfully applied to quasi-static crack propagation. This paper aims to extend its application to the simulation of dynamic crack propagation. Initially, the meshless numerical manifold method's nodal arrangement and numerical integration scheme are enhanced to address dynamic problems more effectively, referred to as the Improved Meshless Numerical Manifold Method (iMNMM). Subsequently, we introduce a novel mass lumping method grounded in rigorous mathematical principles, an energy-conserving extended degrees of freedom inheritance strategy and a crack propagation criterion based on dynamic stress intensity factors. Additionally, the viscous artificial boundaries and the “large mass” acceleration method are incorporated to impose the acceleration and zero-displacement boundary conditions. Further, the improved explicit meshless numerical manifold method based on the central difference method is established for dynamic crack propagation. Finally, for verification, iMNMM is tested on several numerical examples. Numerical results manifest that iMNMM can enable the simulation of dynamic crack propagation with larger, constant time steps.

Determination of the tracking system's trajectory considering the electric drive losses

This paper deals with optimal sun-tracking of a photovoltaic system considering the electric drive losses. The Sun tracking photovoltaic system assures that the highest possible share of the available solar radiation reaches the surface of the photovoltaic modules. The electric drive which enables tracking is considered as the loss of the energy produced in the photovoltaic system. The maximum of the energy produced in the photovoltaic system is achieved by the continuous tracking of the photovoltaic system. Since the electric drives are determined by constant speed and time, and angle quantization the maximum of the energy produced can only approximate. The results presented in this paper show, that the optimal trajectories can help to increase the electrical energy production within photovoltaic systems by sun tracking.

Predecessor on the Ultra-Wide Word RAM

We consider the predecessor problem on the ultra-wide word RAM model of computation, which extends the word RAM model with ultrawords consisting of w2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$w^2$$\\end{document} bits (TAMC, 2015). The model supports arithmetic and boolean operations on ultrawords, in addition to scattered memory operations that access or modify w (potentially non-contiguous) memory addresses simultaneously. The ultra-wide word RAM model captures (and idealizes) modern vector processor architectures. Our main result is a simple, linear space data structure that supports predecessor in constant time and updates in amortized, expected constant time. This improves the space of the previous constant time solution that uses space in the order of the size of the universe. Our result holds even in a weaker model where ultrawords consist of w1+ϵ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$w^{1+\\epsilon }$$\\end{document} bits for any ϵ>0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon > 0 $$\\end{document}. It is based on a new implementation of the classic x-fast trie data structure of Willard (Inform Process Lett 17(2):81–84, https://doi.org/10.1016/0020-0190(83)90075-3, 1983) combined with a new dictionary data structure that supports fast parallel lookups.

Thermodynamics Properties of Amino Acid with Water Mixture using Time Domain Reflectometry Technique

In this paper we have reported the thermodynamics properties of the amino acids (L-alanine) in water solution were carried out using time domain reflectometry at 250C to -50C in the frequency range between 10 MHz to 30 GHz. The dielectric parameters i.e. static dielectric constant and relaxation time, were obtained from the complex permittivity spectra using a nonlinear least square fit method. From the values of the relaxation time, the thermodynamic parameters are determined. The dielectric relaxation parameters increase with an increase in concentration (mM) of amino acid due to the structure of hydrogen bond groups by the amino acid molecules in the aqueous solution. The relaxation peak shifted to lower frequency with an increase in molar concentration of amino acid.

Efficient first-principles electronic transport approach to complex band structure materials: the case of n-type Mg3Sb2

We present an efficient method for accurately computing electronic scattering rates and transport properties in materials with complex band structures. Using ab initio simulations, we calculate a limited number of electron–phonon matrix elements, and extract scattering rates for acoustic and optical processes based on deformation potential theory. Polar optical phonon scattering rates are determined using the Fröhlich model, and ionized impurity scattering rates are derived from the Brooks-Herring theory. Subsequently, electronic transport coefficients are computed within the Boltzmann transport theory. We exemplify our approach with n-type Mg3Sb2, a promising thermoelectric material with a challenging large unit cell and low symmetry. Notably, our method attains competitive accuracy, requiring less than 10% of the computational cost compared to state-of-the-art ab initio methods, dropping to 1% for simpler materials. Additionally, our approach provides explicit information on individual scattering processes, offering an alternative that combines efficiency, robustness, and flexibility beyond the commonly employed constant relaxation time approximation with the accuracy of fully first-principles calculations.

Decolorisation of textile wastewater using biosynthesised iron oxide nanomaterials and Optimisation by Response Surface Methodology

AbstractIn this study, the bacteria (Pseudomonas sp.) was isolated and cultured for biogenic fabrication of Fe3O4 (synthesised using bacterial cell mass) and Fe3O4@ME (synthesised using bacterial extracts) nanoparticles. The biomolecules of the bacterial extract function as a reducing and capping agent, giving the nanoparticle surface negative charges, according to the FTIR and Z potential analysis. The parameters were optimised and screened for indigo blue (IB) dye adsorption onto Fe3O4 and Fe3O4@ME nanoparticles. This work used the Design of the Experimental (DoE) method rather than the conventional one‐variable‐at‐a‐time method. The central composite design (CCD) experiment consisted of 13 experimental runs, and an analysis of variance (ANOVA) was performed to analyse the results. The models for IB dye removal using Fe3O4 and Fe3O4@ME nanomaterials showed adjusted R2 values of 0.99 and 0.99 and predicted R2 values of 0.97 and 0.99, respectively, indicating good model fit. The optimum conditions required for 70 and 64 % colour removal for Fe3O4 and Fe3O4@ME nanomaterials, respectively, are observed at 0.050 gm sorbent doses at the constant room temperature and contact time of 100 min.

Signal Processing from the Radiation Detector of the Radiometric Density Meter Using the Low-Pass Infinite Impulse Response Filter in the Measurement Path in the Coal Enrichment Process Control System

One of the most common coal preparations is enrichment in a jig using a float regulation system. The latest solutions propose to compensate for significant measurement errors of the float by introducing a radiometric density meter operating on the principle of gamma radiation absorption into the bottom product discharge zone of the jig. The signal from the radiometric density meter detector is in the form of a sequence of pulses with a Poisson time distribution, which are counted by a counter, as a form of digital low-pass filter. The requirement to maintain accuracy at an appropriate level forces the measurement time to be extended, which worsens the dynamic properties. Changes in the density of the coal–water medium have an unsteady, cyclical course, resulting from the principle of operation of the jig. The research goal was to develop an algorithm for processing the signal from the radiation detector using an IIR filter in the measurement path in a way that ensures optimization of the dynamic properties of the radiometric density meter operating in the control system of the coal enrichment process in the jig. For this purpose, a low-pass IIR filter was introduced into the measurement path to process the signal from the pulse counter. The identified course of the medium density for one cycle (the first) served as a reference signal. A first-order IIR filter was proposed, with a constant parameter selected on the basis of the reference signal and a parameter depending on the time derivative of the identified density of the medium. The mean squared error MSE was adopted as an indicator for assessing the dynamic properties of the radiometric density meter. The results of simulation tests showed that introducing an IIR filter into the measurement path gives better results in terms of the adopted criterion than using a counter with a constant measurement time. The best results (MSE = 2.05 × 10−4) were obtained using an IIR filter with a parameter that is a linear function of the derivative of the medium density over time, determined for one air pulsation cycle and applied in four subsequent cycles. These results were obtained for an adaptive first-order filter with a variable parameter a from the designated range from 0.833 to 0.999, for a measurement time of 2 ms.

Variable time steps in the numerical implementation of viscoelastic fractional models for laminated glass

Abstract We elaborate numerical approaches to calculate the rheological response of laminated glass beams, whose viscoelastic interlayer is modelled via fractional calculus. This mathematical description is very effective when the relaxation function of the polymer can be expressed by continuously connected branches of power-laws, as is the case for most materials used to laminate glass. The classical approach uses the Grünwald-Letnikov approximation of fractional derivatives, but it requires constant time steps, which would become very large to reasonably cover the entire observation time, thus losing accuracy. We propose to use the L1 algorithm with increasing time steps, which is well suited to the power law character of the relaxation function. This allows to follow the long-term creep response, providing a better approximation when needed. The method is implemented for beams laminated with viscolastic interlayers whose relaxation is described by four branches of power laws, to cover most practical cases. Numerical experiments shows its advantages over the Grünwald-Letnikov approach for characterizing the long-term structural response.

Aftershock forecasts based on incomplete earthquake catalogues: ETASI model application to the 2023 SE Türkiye earthquake sequence

SUMMARY The epidemic-type aftershock sequence (ETAS) model is the state-of-the-art approach for modelling short-term earthquake clustering and is preferable for short-term aftershock forecasting. However, due to the large variability of different earthquake sequences, the model parameters must be adjusted to the local seismicity for accurate forecasting. Such an adjustment based on the first aftershocks is hampered by the incompleteness of earthquake catalogues after a mainshock, which can be explained by a blind period of the seismic networks after each earthquake, during which smaller events with lower magnitudes cannot be detected. Assuming a constant blind time, direct relationships based only on this additional parameter can be established between the actual seismicity rate and magnitude distributions and those that can be detected. The ETAS-incomplete (ETASI) model uses these relationships to estimate the true ETAS parameters and the catalogue incompleteness jointly. In this study, we apply the ETASI model to the SE Türkiye earthquake sequence, consisting of a doublet of M 7.7 and M 7.6 earthquakes that occurred within less than half a day of each other on 6 February 2023. We show that the ETASI model can explain the catalogue incompleteness and fits the observed earthquake numbers and magnitudes well. A pseudo-prospective forecasting experiment shows that the daily number of detectable m ≥ 2 can be well predicted based on minimal and incomplete information from early aftershocks. However, the maximum magnitude (Mmax ) of the next day’s aftershocks would have been overestimated due to the highly variable b value within the sequence. Instead, using the regional b value estimated for 2000–2022 would have well predicted the observed Mmax values.

Reconstruction of self-oscillating systems with delay time modulation

The aim of our research is to study the possibility of reconstruction from time series the self-oscillating systems with variable time delay, demonstrating regimes of turbulent and laminar chaos. Methods. The object of study is self-oscillating systems described by delay-differential equations, in which the delay time is modulated by an external periodic signal. The possibility of estimating the parameters of systems with delay time modulation from their time series is considered using the known method for reconstructing systems with constant delay time, which is based on statistical analysis of time intervals between all possible pairs of extrema in time series. A new method for estimating the parameters of systems with variable delay time is proposed, based on statistical analysis of time intervals between two successive extrema in time series. Results. It is shown that in some cases the known methods for reconstructing systems with constant delay time are also effective for reconstructing systems with varying delay time. With their help, one can estimate the mean delay time and recove the nonlinear function of the system. The proposed method, aimed at application to time-delay systems with delay time modulation, allows one to estimate the frequency and amplitude of delay time modulation. Conclusion. The obtained results are of interest to various scientific disciplines that study systems with variable delay times based on their time series.

An Energy-Efficient Wireless Power Receiver With One-Step Adiabatic-Bipolar-Supply Generating for Implantable Electrical Stimulation Applications.

This paper presents an energy-efficient wireless power receiver for implantable electrical stimulation applications, which can achieve one-step adiabatic bipolar-supply that is generated by a hybrid single-stage dual-output regulating (SSDOR) rectifiers. The structure using only four switches overcomes the disadvantages that the two output voltage values in the traditional dual-output rectifiers are close to each other. A constant-current (CC) controlled adiabatic dynamic voltage scaling (DVS) technique is proposed to minimize the voltage headroom of the stimulating drivers and improve the stimulation efficiency significantly. In addition, the receiver adopts only one general constant on-time (COT) low-frequency control to adjust the stimulation current, reducing both the power consumption and the complexity of the control circuits. The proposed receiver has been fabricated in a 0.18 μm BCD process with ±6 V voltage compliance and 2.5 mA maximum stimulating current. With a current range from ±1.5 mA to ±2.5 mA, the measured maximum average headroom voltage is only 80 mV and the peak total efficiency of the receiver is 85.6 %. The functionalities of the proposed receiver have been successfully verified through in vitro experiments.

Principle of predicting the reduction of insulation properties of electric motor windings

The simplicity of the design of the asynchronous electric motors (AM) allows them to be widely used in industry. The AM fleet sometimes reaches 80% of the total load of the enterprise. According to statistics, more than 60% of AM failures are observed due to damage to the insulation of the AM stator winding. The reason is premature dynamic and thermal aging of the insulation, which leads to the failure of the conductive and grooved parts of the AM winding. As a result of a decrease in the dielectric properties of the insulation, damage occurs in the stator windings of AM, such as turn, phase-to-phase short circuits, which tend to develop into a short circuit. Short circuits in the stator windings of the AM are emergency and lead to a sudden disconnection of the AM from the power supply network by existing relay protection means, for example, current cut-off or thermal protection. Sudden, non-sanctioned disconnection of the electric motor from the power supply leads to the shutdown of technological equipment, damage to equipment, raw materials and economic losses. The aim of the work is to develop the principles of timely monitoring and prediction of the state of housing and interphrase insulation of stator windings of AM using the energy of capacitors with local compensation of reactive power. To achieve this goal, research was carried out at a laboratory institution with AM, in which branches of turns were made. The transient processes of capacitor discharge are considered and new methods for monitoring and predicting the residual insulation life are proposed. The new method is based on monitoring the condition of the insulation after each disconnection of the AM from the power supply, while using the energy that remains in the capacitors. The use of a change in the velocity characteristic of the constant discharge time of the capacitor made it possible to predict the residual service life of the AM. The personality of the study is that under the conditions of local compensation of reactive power, it is possible to use the energy remaining in the capacitors to diagnose and predict the state of insulation, as well as the change in the velocity characteristic of the capacitor discharge time constant, which is a criterion parameter for predicting the residual service life of the AM. The carried out studies confirmed the development of test diagnostics in conditions of reactive voltage compensation, which is a new direction in systems non-poisonous diagnostics, which requires continued research and applications in industry.

Relevance of Sulfate Functionalization and Porous Structure of TiO2 Ceramic Foams in Photocatalytic Degradation of Dye Molecules

A one-step route was developed for sulfate functionalization of titania foam, consisting of integrating the sol-gel process with an emulsion template. The resulting material was used to evaluate the relevance of the porous structure and surface sulfate groups in the photocatalytic degradation of Rhodamine B molecules in water under UV irradiation. X-ray diffraction (XRD) analysis showed that the anatase crystalline phase was metastabilized by functionalization of the surface with sulfate species, which caused the crystallite size to decrease from 21 to 10 nm, while the specific surface area increased from 4 to 42 cm2 g-1. Small-angle X-ray scattering (SAXS) measurements during heating of the non-sulfated (E-TiO2) and sulfated (E-TiO2/SO42-) sols emulsified with sodium dodecyl sulfate (SDS) as surfactant and isopropyl myristate as the nonpolar phase, revealed formation of the liquid crystalline structure. Elimination of this mesophase template allowed the preparation of ceramic foams with hierarchical structure formed by meso- and macropore families. The kinetics of photodegradation reaction of Rhodamine B followed a pseudofirst order mechanism. The most efficient photocatalytic activity (higher rate constant and shorter half-life time) was obtained for the foam templated using 20% of SDS (E-TiO2/SO42- 20SDS), which exhibited the highest values for porosity (93%) and specific surface area (80 m3 g-1).

Natural water thermal radiation at a gigahertz frequency

The radiation-temperature dependence for natural water in the temperature range of 50-90 degrees Celsius was experimentally investigated. Experimental studies were carried out using radiometer with central frequency 37.5 GHz. The fluctuation threshold of sensitivity of radiometer was equal 0.2 K, with a constant relaxation time of the order of one second. The thermodynamic water temperature was measured by a contact thermometer immersed in the water column. The measurements were carried out outdoors at an ambient temperature of about 24 degrees Celsius. A noticeable increase of radio brightness temperature (about 25 K) was detected in 50-90 degrees Celsius temperature range. The qualitative coincidence of the experimental data with the theoretical ones calculated using the Stogrin model is demonstrated. The obtained coincidence of experimental data with theoretical data makes it possible to use heated and cooled water to create thermal standards and use them for millimeter wavelengths antenna calibrations under field conditions. The radio contrast value of the radiation-temperature dependence in the temperature range under study makes it possible to detect thermal variations of the hydro objects surfaces. A significant contrast of the water thermal radiation in the range of gigahertz frequency can be used for water monitoring and achievement of the environmental sustainability of cities and settlements.

Characterization of Yttria-Stabilized Zirconia (YSZ) following high temperature hydrogen exposures of molybdenum-YSZ composites

Molybdenum matrix ceramic-metal (cermet) composites containing 40–70 vol% yttria stabilized zirconia (YSZ) particles (as a surrogate for ceramic fuel particles) were produced via spark plasma sintering (SPS) and exposed to flowing hydrogen at high temperature (2000–2630 K). Both steady state and thermally cycled (4 cycles with intermediate cooling to room temperature) conditions were examined for a constant total hot testing time of 80 min. Due to the high hydrogen permeability in Mo at these temperatures, pronounced microstructural degradation was observed in YSZ particles located many millimeters below the sample surface. Observed changes to the YSZ particles from the hot hydrogen testing include partial matrix debonding, thermal expansion, redeposition of material, phase changes to a monoclinic phase and cracking/bubble formation on the YSZ grain boundaries. Overall, the YSZ particles exhibited acceptable tolerance to this extreme operating environment.

A tractable methodology for assessing the pressure scaling of sooting processes in a counterflow diffusion flame from 1 to 6 bar

A parametric study using ethylene as fuel was undertaken which examines the efficacy of concentration based and soot production rate (SPR) based parameters for assessing the pressure scaling of sooting processes in a counterflow diffusion flame. Two experimental designs pertaining to constant flow residence times (Case A), and constant carbon mass flux (Case B) were respectively implemented for pressures between 1 to 6 bars and across peak temperatures ranging from ∼2300−2600 K for Yf=Yox=0.35, ∼2100−2400 K for Yf=Yox=0.30, and ∼1800−2100 K for Yf=Yox=0.25 flames. A diffuse line-of-sight based extinction imaging diagnostic was employed for the measurement of soot concentrations. The evaluation of SPR follow a transport based coupling of inferred gaseous precursors, temperatures and velocity fields from detailed 1D OpenSMOKE++ simulations and soot concentrations from extinction measurements. The use of concentration based parameters, namely peak (∼p2.5−4.5) and integrated soot volume fractions (∼p2.1−3.9), is noted to be dependent on the Case A or B with little information discernible about the pressure effects in an experimental setting. The use of production rate based parameters, namely mean SPR (∼p2.2−3.4) removes the disparity of pressure scaling exponents across cases A and B but inherits the dependency to peak flame temperature, and gaseous precursor concentrations. An empirical fit of local SPR to acetylene and pyrene concentrations reveals a universal Arrhenius activation energy parameter in the high-temperature region (1300–2000 K) of the studied flames. The global activation energy is noted to remain roughly constant across varying peak flame temperatures, fuel flux, flow residence times and pressure. Consequently, we propose a soot yield parameter (Ω), calculated as the mean soot production rate normalized to acetylene and pyrene mass fractions which is noted to universally scale with pressure as Ω∼p1.7.

A Novel Describing Function Small-Signal Modeling Approach for Passive Ripple Constant On-Time Controlled Converter with Exponentially Varying Slope

A Novel Describing Function Small-Signal Modeling Approach for Passive Ripple Constant On-Time Controlled Converter with Exponentially Varying Slope

Comparative analysis of solvent extraction of rice bran oil from various sources

This study investigated oil extraction from rice bran a by-product of rice gotten from different sources (Afikpo, Abakaliki, and Emene). The oil was extracted from different particle sizes (150 µm, 300 µm, and 420 µm) of the rice bran using three different solvents namely chloroform, petroleum ether, and n-hexane at constant time of 120 minutes via soxhlet extractor. The physiochemical properties of the extracted oil were boiling point, the saponification values and refractive index were 77 <sup>o</sup>C, 185.130, and 1.334, respectively. Also the acid value, surface tension, iodine value, and relative density were found to 15.040 g, 6.966×10<sup>2 </sup>N/M, 99.480, and 0.779, respectively. The obtained result based on source revealed that the maximum oil yield of 35.05 g was achieved from Abakaliki rice bran using chloroform solvent and particle size of 420 mm, whereas Emene and Afikpo gave 32.62 g and 14.18 g of oil, respectively from same solvent and particle size. Again, the highest volume of oil obtained in terms of solvent used were chloroform, petroleum ether, and n-hexane, in descending order. The physicochemical properties investigated, showed that the extracted rice bran oil (RBO) from the above three sources in Nigeria confirms RBO to be of good quality and can be utilized in many food industries after refining in form of additives/or industrial purposes as well as in generation of energy.

RESEARCH AND DEVELOPMENT OF THE DRYING TECHNOLOGY

Static and dynamic characteristics of the drying process as an object of automation are experimentally determined in the work. It was established that the drying object can be represented as two linked "air" – "drying object" and has interconnected input and output parameters. A mathematical description of the static and dynamic characteristics of the drying process as an object of automatic regulation has been researched and carried out. With the help of mathematical processing of experimental data, mathematical dependences on the studied regulation channels were obtained as the transfer functions, differential equations, and acceleration curve equations. The obtained experimental time characteristics of the drying object on different control channels are approximated with an error of less than 3% by differential equations of the 1st order with a delay. The object is characterized by variable constant time and delay time values for different drying phases.

A Novel Numerical Modeling Chinese Population Evolution

In this paper, we build a very accurate mortality model with a constant time decay function and the optimal goal of minimizing the total number of deaths, then solve it by a numerical approach. China’s vast territory, large population, complex flow of people, and the concept of returning to the hometown greatly affect the accuracy of survey population mortality. Furthermore, the instability of the solution of the Lee-Carter mortality model makes it difficult to predict the future population mortality in China. Based on the population data published in China from 1990 to 2000 with corrections, the mortality results from 2001 to 2019 are predicted by using the new model. Compared with the population and deaths in the National Statistical Bulletin, the average death rate error is less than 0.64%, the maximum annual error is less than 6.11%. According to this result, the total population and mortality results from 2001 to 2020 are predicted. Most of the prediction error rates of annual total population is 1 ‰, and the maximum error rate is less than 3.4 ‰. The accuracy of the model for Chinese population prediction is around 10 times higher than any other current models.