Empirical Coefficients Research Articles

Comparative study of solar flux using different empirical models at low land urban industrial zone of Biratnagar Nepal


 
 
 
 Nepal is a developing country where sufficient clean energy is not available in our daily needs for cooking, lighting and other developmental activities. So, it is high time to promote clean and green energy, which is freely available in every corner of the country. In this regard, the present study helps to estimate the global solar radiation at the lowland region Biratnagar (lat. 26◦28′53′′N, long. 87◦15′50′′E and Alt. 72 m) using measured global solar radiation (GSR) and sunshine hours on empirical models. This paper uses the regression technique on two different empirical models Angstrom-Prescott(A-P) and Tiwari and Sangeeta, to estimate solar radiation. After analyzing the data on empirical models, the empirical constants 0.25 and 0.23 and 0.13 and 0.24 are found in A-P and Tiwari and Sangeeta models, respectively. The performance of the models was carried out by employing mean bias error (MBE), mean percentage error (MPE), root mean square error (RMSE) and adjusted coefficient of determination (R2). These statistical tools reveal that all these models are statistically significant. Such a study is relevant when reliable data for solar radiation is not adequately available. The findings of empirical coefficients can be utilized for predicting solar radiation and solar energy at similar geographical locations in Nepal.
 
 
 

Estimating Paleointensities From Chemical Remanent Magnetizations of Magnetite Using Non‐Heating Methods

AbstractMany meteorites experienced aqueous alteration on their parent body. During this process, magnetite usually forms and acquires a chemical remanent magnetization (CRM) if growing in the presence of a magnetic field. The epoch of aqueous alteration on planetesimals encompasses the lifetime of the solar nebula. Therefore, magnetite‐bearing meteorites are potential sources of invaluable data regarding the intensity of the solar nebula magnetic field and its influence on planetary accretion. The major limitation encountered in meteorite paleomagnetic studies is the lack of an empirical law relating a CRM characterized using non‐heating methods and the magnetizing field intensity. This issue is usually bypassed using the empirical law for non‐heating methods calibrated for thermoremanent magnetizations (TRM), resulting in poorly constrained paleointensities. Here, we determine such an empirical law through a series of CRM acquisition experiments. Magnetite is grown in weakly magnetic sedimentary rocks and synthetic samples in a magnetic field while heated at 350°C for 5 hr in an argon atmosphere. All samples exhibit a high‐coercivity magnetization parallel and proportional to the field applied, identified as a CRM carried by magnetite. We determine the CRM empirical law by retrieving the applied field intensity using non‐heating methods. The empirical coefficients differ from the TRM ones by a factor of 1.9–3.2 depending on the method. We use these coefficients to revisit the paleointensities published for the CM chondrite Murchison and the C2 ungrouped Tagish Lake. This empirical law opens the door to the study of numerous magnetite‐bearing meteorites potentially carrying a CRM.

Wavelet shrinkage in nonparametric regression models with positive noise

ABSTRACT Wavelet shrinkage estimators are widely applied to analyse datasets in wavelet domain from several fields of science. They typically act by reducing magnitudes of empirical coefficients in a discrete wavelet transformation to estimate wavelet coefficients. In nonparametric regression problems, most of the shrinkage rules are derived from models composed of an unknown function with additive Gaussian noise. Although Gaussian noise assumption is reasonable in several real data analysis, mainly for large sample sizes, it is not general. Contaminated data with positive noise can occur in practice and nonparametric regression models with positive noise bring challenges in wavelet shrinkage point of view. In this sense, this work proposes bayesian shrinkage rules to estimate wavelet coefficients from a nonparametric regression framework with additive and strictly positive noise under exponential and lognormal distributions. Computational aspects are discussed and simulation studies to analyse the performances of the proposed shrinkage rules and compare them with standard techniques are done. An application for winning times Boston Marathon dataset is also provided.

Role of the Convective Factor in the Corrosion of Low-Carbon Steel in Solutions of Sulfuric Acid Containing Iron(III) Sulfate

The authors study the corrosion of low-carbon steel in solutions of H2SO4 containing Fe2(SO4)3 with and without additives of individual and mixed corrosion inhibitors. It is established that the oxidizing capacity of the given system (in which the reactions between iron, an acid solution, and Fe(III) salts are thermodynamically allowed), characterized by the redox potential of an Fe(III)/Fe(II) pair, is largely determined by its anionic composition: sulfate anions of a corrosive medium bind Fe(III) cations into complex compounds, reducing their oxidizing ability. Partial reactions of the anodic ionization of iron and the cathodic reduction of H+ and Fe(III) cations are revealed in analyzing the effect convection of the medium has on the electrode reactions of low-carbon steel. The first two reactions are characterized by kinetic control; the third, by diffusion. It is shown that the accelerating effect Fe2(SO4)3 has on the corrosion of steel in a solution with H2SO4 is mainly due to the reduction of Fe(III). In contrast, the accelerating action of Fe(III) cations affects all partial reactions of steel in an inhibited acid. There is a large drop in the apparent coefficient of diffusion of Fe(III) cations (DFe(III)) in inhibited solutions, relative to an uninhibited medium. Data on the corrosion of low-carbon steel in the given media, obtained from the mass loss of metal samples, are in full agreement with results from studying partial electrode reactions. Consideration is given to the accelerating effect Fe2(SO4)3 has on the corrosion of steel in solutions of H2SO4 with and without inhibitors. In these environments, the corrosion of steel is determined by the convective factor, which is typical of processes with diffusion control. The empirical dependence of the rate of steel corrosion on the intensity of the medium’s flow is described by linear dependence k = kst + λw1/2, where kst is the rate of the corrosion of steel in a static environment, w is the rotational speed of the propeller agitator creating the flow of the medium, and λ is an empirical coefficient.

Development of an empirical model for the prediction of the noise reduction coefficient for thin and low-density fibrous materials

This paper presents the development of an empirical noise reduction coefficient model for the prediction of low-density, less than 50 kg/m3, thin, less than 20 mm thick, fibrous materials using multiple linear regression. The purpose of this empirical model is to assist design engineers, working with thin and low-density materials, efficiently and effectively select the most appropriate material for the design. Therefore, several models were developed using software such as Statistical Analysis System. Thereafter, the models were compared using an internal and external data set. A selection metric was developed to assist in the objective selection of the best model. It was found that the log model performed the best overall and thus was selected as the model of choice.

Расчет и корректировка значений упругих свойств топливных смесей

The paper substantiates the use of a simple and convenient Cole equation form of state making it possible to quickly and with sufficient accuracy determine density, compressibility coefficient and speed of sound of the fuel mixtures at high and ultrahigh injection pressures. A method is described for calculating these elastic properties of the fuel mixtures using the constants of the state equation selected in the form of expressions that determine dependence of the constants on the temperature. Expediency of introducing the universal correction factors is shown, which allows refining calculated values of the fuel mixture elastic properties. Processed experimental data from the literature sources and conducted studies formed the basis to obtain empirical coefficients to determine the correction factors that are refining values of the arbitrary composition mixture properties. The described method and the found coefficients make it possible to hydrodynamically calculate the fuel supply process using modern mathematical models and to design new fuel systems with the higher injection parameters.

Determination of bromine, iodine, and other components in northern Hainan island soil

The emergence of the integrated wavelength-dispersive and energy-dispersive Zetium X-ray fluorescence spectrometer technique offered new chances to analyze elemental distribution with minimal sample preparation in complex matrix geological samples-northern Hainan island soils. Wavelength-dispersive X-ray fluorescence was applied for the measurement of bromine in the northern Hainan island soil. To reduce the fluctuations of the low-bromine-content measurement results, a two-channel measurement of bromine was designed, and the average value of the two-channel measurements was used as the final result. The soil samples in northern Hainan Island were rich in iodine, with a content range of a few µg/g to more than 100 µg/g, and these were particularly suitable to be analyzed by energy-dispersive X-ray fluorescence spectrometer. The geological samples in northern Hainan Island were brown, purple, and brown-red soil containing kaolinite, ilmenite, rutile, anatase, and goethite. These soil samples were rich in titanium, aluminum, and iron. The titanium concentration in the northern Hainan Island soil was anomalously high (up to 15.05%), far exceeding the content range of the calibration curve. Owing to the empirical coefficient matrix correction method, unreliable or even unreasonable results were obtained for some elements. By systematically mitigating matrix effects through the development of custom reference materials and building matrix-matched measurement and calibration routines, the quantification of Vanadium, Barium, and major components in northern Hainan Island soil samples was optimized. The efficacy of the X-ray fluorescence spectrometer method was confirmed by comparison with inductively coupled plasma–optical emission spectroscopy analysis. This work demonstrates the capability of the integrated wavelength-dispersive and energy-dispersive Zetium X-ray fluorescence spectrometer technique for reliable quantitative elemental analysis of complex matrix geological samples.

Numerical Analysis of Local Scour of the Offshore Wind Turbines in Taiwan

Rapid expansions of the offshore wind industry have stimulated a renewed interest in the behavior of offshore wind turbines. Monopile, tripod, and jack-up wind turbines support most offshore wind turbines. These foundations are sensitive to scour, reducing their ultimate capacity and altering their dynamic response. However, the existing approaches ignore the seabed’s rheological properties in the scour process. This study focuses on the scour development around the wind turbine foundation in the Changhua wind farm in Taiwan. The simulation results explain the influence of different hydrodynamic mechanisms on the local scours in a cohesive fluid, such as regular waves, random waves, and constant currents. A newly non-Newtonian fluid model, the Discontinuous Bi-viscous Model (DBM), reproduces closet mud material nature without many empirical coefficients and an empirical formula. This new rheology model is integrated and coupled into the Splash3D model, which resolves the Navier–Stokes equations with a PLIC-VOF surface-tracking algorithm. The deformation of the scour hole, the backfilling, and the maximum scour depth are exhibited around the wind turbines. Waves, including regular and irregular waves, do not increase the scour depth compared with currents only. In the case of random wave–current coupling, the results present a signal of scour evolution. However, the scour depth is shallow at 0.033≤S/D≤0.046.

Prediction of nonlinear pumping pressure loss of concrete induced by rheological property changes

The pumping pressure loss of fresh concrete has traditionally been modeled as a linear function of the pumping distance. However, previous studies have suggested that this relationship is nonlinear in nature. This research has identified that the nonlinearity is due to changes in the rheological properties of fresh concrete during pumping. In this study, a new prediction equation has been proposed for the loss of pumping pressure for concrete mixtures with w/c ratios between 0.17 and 0.46, and an equivalent horizontal pipe length between 328 and 912 m. The equation provides a linear approximation of the nonlinear relationship of pumping pressure loss. To account for the effect of rheological changes during pumping, an empirical coefficient related to the initial slump flow of the concrete has been incorporated. The new function can improve the prediction accuracy of pressure loss by 25 % and 4.2 % for horizontal and vertical pumping, respectively.

The Bias Dynamics Model: Correcting for Meta-biases in Therapeutic Prediction

AbstractInferences from clinical research results to estimates of therapeutic effectiveness suffer due to various biases. I argue that predictions of medical effectiveness are prone to failure because current medical research overlooks the impacts of a particularly detrimental set of biases: meta-biases. Meta-biases are linked to higher-level characteristics of medical research and their effects are only observed when comparing sets of studies that share certain meta-level properties. I offer a model for correcting research results based on meta-research evidence, the bias dynamics model, which employs regularly updated empirical bias coefficients to attenuate estimates of therapeutic effectiveness.

Modeling shear thinning polymer flooding using a dynamic viscosity model

Two distinct effects that polymers exhibit are shear thinning and viscoelasticity. The shear thinning effect is important as the polymers used in chemical enhanced oil recovery usually have this property. We propose a novel approach to incorporate shear thinning effect through effective dynamic viscosity of the shear thinning polysolution. The procedure of viscosity calculation of the polysolution, although based on a very basic power law model, is based on empirical coefficients that depend on a spatio-temporally evolving variable, namely, concentration of polymer. Since viscosity calculation is performed in space and time, the results obey correct physics and are more accurate than what exists in the literature. This method has been integrated with an existing method for a Newtonian physics based model of porous media flows. The solver uses a hybrid numerical method developed by Daripa and Dutta [“DFEM-MMOC based EOR code in MATLAB” (2020); P. Daripa and S. Dutta, “Modeling and simulation of surfactant–polymer flooding using a new hybrid method,” J. Comput. Phys. 335, 249–282 (2017); and P. Daripa and S. Dutta, “On the convergence analysis of a hybrid numerical method for multicomponent transport in porous media,” Appl. Numer. Math. 146, 199–220 (2019)]. The above method solves a system of coupled elliptic and transport equations modeling Darcy's law based polymer flooding process using a discontinuous finite element method and a modified method of characteristics. Simulations show (i) competing effects of shear thinning and mobility ratio; (ii) injection conditions, such as injection rate and injected polymer concentration, influence the choice of polymers to optimize cumulative oil recovery; (iii) permeability affects the choice of polymer; (iv) dynamically evolving traveling viscosity waves; and (v) shallow mixing regions of small scale viscous fingers in homogeneous porous media. The overall goal of this study is to develop an effective yet easy approach to make design choices of polymers in any given flooding condition, which has been shown here.

Transverse flow distributions in ice‐covered channels

AbstractTraditional discharge measurements in ice‐covered river channels are time‐consuming and costly, thus limiting the elucidation of flow patterns during winter. This study proposes an analytical model for quantifying the transverse distributions of the unit‐width discharge and the depth‐averaged streamwise velocity in ice‐covered channels by extending an existing stream‐tube method to include the effects of cover and bed roughness and cross‐sectional geometry. A new set of equations are obtained for this extended method. An empirical coefficient α is included to lump the effects of the shape and friction factors of the ice cover and the channel bed. The model is compared with flume experiments and field data for fully and partially ice‐covered flows to examine the variation of the coefficient α.

Target Lipid Model and Empirical Organic Carbon Partition Coefficients Predict Sediment Toxicity of Polychlorinated Biphenyls to Benthic Invertebrates.

Quantifying causal exposure-response relationships for polychlorinated biphenyl (PCB) toxicity to benthic invertebrates can be an important component of contaminated sediment assessments, informing cleanup decisions and natural resource injury determinations. Building on prior analyses, we demonstrate that the target lipid model accurately predicts aquatic toxicity of PCBs to invertebrates, providing a means to account for effects of PCB mixture composition on the toxicity of bioavailable PCBs. We also incorporate updated data on PCB partitioning between particles and interstitial water in field-collected sediments, to better account for effects of PCB mixture composition on PCB bioavailability. To validate the resulting model, we compare its predictions with sediment toxicity data from spiked sediment toxicity tests and a variety of recent case studies from sites where PCBs are the primary sediment contaminant. The updated model should provide a useful tool for both screening-level and in-depth risk analyses for PCBs in sediment, and it should aid in diagnosing potential contributing factors at sites where sediment toxicity and benthic community impairment are observed. Environ Toxicol Chem 2023;42:1134-1151. © 2023 SETAC.

DESIGN SCENARIO AND ANALYSIS FOR PRELIMINARY SPECIFICATION OF STEAM GENERATOR IN THE PELUIT-40

The helical steam generator is connected to an HTGR-type nuclear reactor called PeLUIt-40 for steam production. Steam is used to generate electricity and hydrogen. A once-through helical tube bundle was employed because of its ability to endure mechanical stress due to thermal expansion, high resistance to flow-induced vibrations, and better thermal performance compared to a straight tube one. To produce the targeted steam, a design analysis of the once-through helical steam generator needs to be conducted. A quick evaluation method was used to predict the preliminary specifications required for steam production. Simple thermodynamic calculations combined with empirical heat transfer coefficients covering convective and boiling processes at constant pressure were used to carry out the analysis. Two scenarios were conducted to evaluate the design choice based on the previous design of RDE-10.

Principles of designing electromagnetic screens of the resonant type based on liquid protective compositions

The work explores the possibilities of creating resonance-type electromagnetic shields to protect workers and the population from man-made electromagnetic fields. It is shown that traditional resonant screens are not technological enough to cover large surfaces and are tuned to monochrome or narrow-band electromagnetic fields. Based on the analysis of the experience of using liquid shielding mixtures, the possibility of creating a multilayer structure without fixed layer thicknesses, which will allow protection against the influence of the frequency band, has been proven. At the same time, the wave resistance of the outer layer allows you to minimize the reflection coefficients of electromagnetic waves, which makes the material practically absorbent. A calculator for the preliminary calculation of the electrophysical properties of each layer is presented, which allows rationalizing the required coefficients. For calculations, the formulas of Odelevsky and Debye for the dielectric constant of mixtures are adapted. Experimentally obtained empirical coefficients are presented, which are a component of the ratio for obtaining acceptable screen parameters. To determine the exact concentration of the shielding filler in the matrix, a correction factor is provided. This is associated with errors when determining the volume content of the filler of low dispersion and differences in the morphology of the filler particles, which does not allow for an accurate calculation of the depolarization coefficient of the filler particles. Given the lack of reference data on the electrophysical parameters of the compositions due to their diversity, it is advisable to conduct thorough laboratory studies with different compositions of the compositions. This will make it possible to form a reference database that will speed up the execution of electromagnetic safety work and reduce their cost.

Nondestructive detection of delamination in painted concrete structures through square pulse thermography

Active infrared thermography (IRT) is effective for detecting and characterizing subsurface defects in concrete structures. Even though painted concrete (PCo) structures have been applied worldwide (especially for buildings) and subsurface defects, such as delaminations, can develop in their core, active IRT-based defect detection in previous studies focused on normal concrete (NCo) structures rather than PCo structures. Hence, the detectability of delaminations in NCo and PCo structures is investigated in the present study by applying square pulse thermography (SPT), a common approach for active IRT. The results demonstrated that delaminations in PCo, under the same parameters, are more detectable in IR images than in NCo structures. In addition, the effect of the width-to-depth ratio of a defect in PCo structures on the detectability during SPT inspections is presented. Interestingly, overheating is evaluated to determine an effective heating regime for SPT surveys on PCo structures. Finally, the empirical thermal diffusivity coefficient of PCo structures is estimated, which has not been previously determined.

Численное исследование сверхзвуковой ступени осевого компрессора. Влияние втулочного отношения на ее параметры

Countless combinations of sizes and shapes of the flow path could ensure the specified flow rate and pressure ratio of the axial compressor stage. Programs based on the mathematical models are an effective tool in initial design and preliminary selection of the optimal option. The RROK-GPD-22 software program is briefly being described, it solves the problem on the basis of the pressure loss model and deflection capacity of the A. Komarov lattice, theoretic rigorous calculation of oblique and direct shocks, as well as empirical equations and coefficients. Models were checked by comparison with data on the Rotor 37 NASA test stage. Stages were calculated with different ratio of the cross-sectional area at the outlet of the impeller to that at its inlet and stages with the hub-tip ratios of 0.400 ... 0.728 with different swirl at the impeller inlet. Results are provided in determining the hub-tip ratio influence on the efficiency, pressure ratio and specific stage performance.

Improved Iron Loss Prediction Models for Interior PMSMs Considering Coupling Effects of Multiphysics Factors

This article presents improved iron loss analytical prediction models for interior permanent magnet synchronous motors (IPMSMs) used in electric vehicles. The effects of slotting harmonics, pulsewidth modulation (PWM) carrier harmonics, temperature rise, and mechanical stress are considered in the proposed models. Specifically, by investigating the stator flux density as piecewise linear with trapezoidal waveform, the iron losses in the teeth and yoke regions are calculated separately, considering the different magnetic field distributions and waveforms. To deliberate the PWM harmonic influence, a correction coefficient is added to the hysteresis loss models, while the eddy current loss models are updated by summing all the eddy current losses caused by the power supplying current harmonics. Moreover, the coupling interaction effects of magnetic, thermal, and stress fields on the empirical coefficients of hysteresis and eddy current losses are analyzed in detail and also implemented in the iron loss prediction process. The feasibility and superiority of the proposed models are verified by numerical and experimental case studies on an IPMSM prototype.

Total mechanical energy budget in open-channel transitions with turbulent flows

Abstract The issue of mechanical energy budget has received a lot of attention in open-channel flows which are frequently turbulent. Turbulent motions play a major role in the total mechanical energy of the flow field. It is difficult to evaluate total mechanical energy balance and energy loss for 3-D turbulent flows in irregular open channels due to the formation of vortices and the presence of secondary currents. In 3-D turbulent flows, the effect of these phenomena has often been considered as the empirical coefficient of energy loss. In this study, these details in the total mechanical energy budget are investigated through theoretical analysis and numerical simulation, a new form of the total mechanical energy equation and a relationship for the energy loss in 3-D turbulent flows are derived, and their applications are examined in open-channel transitions. For this purpose, the Navier-Stokes equations are solved numerically, and the results are used to obtain the various terms in the total mechanical energy balance equation and analyze the details. The relationships derived in this study generally support the concept of the total mechanical energy budget to comprehend the turbulence parameters affecting the mechanical energy balance in various open-channel flows.

Photovoltaic Module Degradation Forecast Models for Onshore and Offshore Floating Systems

The degradation trend of photovoltaic modules depends on the technology, manufacturing techniques and climatic conditions of the site where they are installed. Longer useful life of the PV modules means that they will be able to produce much more energy than was used to build them; thus, extending the useful life of the modules is beneficial for the environment and increases the cost effectiveness of PVs. The problem of land use has prompted the development of agrivoltaic systems to exploit the same land both for the production of energy and for agriculture, and on water surfaces such as lakes and dams (floating PV). The exploitation of floating PV systems in onshore and offshore areas is currently under study. This constitutes an opportunity for which many factors must be taken into account; a fundamental aspect is the environmental impact, on which some recent studies have focused. Another aspect is the impact of the marine environment on PV system reliability and durability, due to the stress on operating conditions. The aim of this preliminary study is to evaluate the influence of the marine environment on the degradation trend of photovoltaic modules, based on existing models whose inputs are meteorological data from offshore locations. The results obtained from the application of a cumulative exposure model unexpectedly showed a lower degradation value in the offshore environment than on the mainland: −0.95% and −3% values of power decay, respectively. The absolute value of power decay in the onshore case is higher than the typical values because the used model has to be revised, as the empirical coefficients of the model have to be calculated according to the installation environment. The empirical coefficients used in the model were obtained in environmental conditions different from those under study. In the offshore case, the degradation estimated by the model does not take into account some environmental factors typical of the marine environment. Model adaptations calibrated with datasets of plants in environmental conditions similar to those analyzed would allow for greater accuracy in the results.