Parameter F0 Research Articles

Strength characteristics and damage constitutive model of sandstone under hydro-mechanical coupling

Abstract To study the mechanical properties of saturated sandstone, experiments were conducted under hydro-mechanical coupling on saturated sandstone. A damage constitutive model was established to describe the response of saturated sandstone under pore pressure, and its validity was verified using the results of the triaxial tests. The results indicate that the peak strength (σ p), effective peak strength (σ p′), residual strength (σ r), effective normal stress (σ n′), effective shear strength (τ n′), elasticity modulus (E), and rupture angle (θ) of sandstone are positively correlated with the confining pressure (σ 3) and negatively correlated with the pore pressure (P). Conversely, Poisson’s ratio (μ) exhibits an opposite relationship. The model parameters exhibit non-linear relationships with the confining pressure (σ 3), with the parameter m decreasing gradually as the confining pressure increases, and the parameter F 0 increasing with higher confining pressure (σ 3). Moreover, the pore pressure (P) and the confining pressure (σ 3) significantly affect the damage variables (D), with the stress value at the damage initiation point increasing with increasing confining pressure (σ 3), while the strain value at the damage initiation point decreasing with increasing pore pressure (P), indicating that pore pressure induces damage development in rocks.

Nano-silicone and Ascophyllum nodosum-based biostimulant down-regulates the negative effect of in vitro induced-salinity in Rosa damascena

BackgroundRosa damascena is extensively cultivated in various regions of Iran due to its aesthetic attributes, medicinal qualities, and essential oil production. This study investigated the efficacy of Ascophyllum nodosum extract (AnE) at concentrations of 0, 2, and 3 g L− 1 and Nano-silicon (nSiO2) at concentrations of 0, 50, and 100 mg L− 1 in ameliorating the impact of salinity on two genotypes of Damask rose (‘Chaharfasl’ and ‘Kashan’) under in vitro culture conditions. Additionally, various physio-chemical characteristics of R. damascena explants were assessed.ResultsThe findings revealed that exposure to 100 mM NaCl resulted in a substantial reduction in the Relative Water Content (RWC), Membrane Stability Index (MSI), leaf pigments (Chlorophyll b, Chlorophyll a, total Chlorophyll, and carotenoids), chlorophyll fluorescence parameters, and protein content in both genotypes when compared to control conditions. Salinity induced a significant increase in the parameter F0 and a decrease in the parameter Fv/Fm compared to the control conditions in both genotypes. Nonetheless, the genotype Kashan treated with 3 g L− 1 AnE + 100 mg L− 1 nSiO2 exhibited the maximum Fm value under control conditions, with a significant difference compared to other treatments. Furthermore, salinity caused a considerable reduction in Fm in both ‘Kashan’ and ‘Chaharfasl’ by 22% and 17%, respectively, when compared to the control condition. ‘Kashan’ displayed the maximum Fv/Fm compared to the other genotype. The maximum levels of Malondialdehyde (MAD) and hydrogen peroxide (H2O2) were also observed in explants affected by salinity. The combination of 3 g L− 1 AnE + 100 mg L− 1 nSiO2, followed by 2 g L− 1 AnE + 100 mg L− 1 nSiO2, exhibited substantial positive effects. Salinity also led to an increase in proline content and the activity of peroxidase (POD), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and catalase (CAT) in both genotypes. The activity of these enzymes was further enhanced when AnE was applied at concentrations of 2 and 3 g L− 1 in combination with 100 mg L− 1 nSiO2.ConclusionsThe ‘Kashan’ genotype displayed greater tolerance to salinity by enhancing water balance, maintaining membrane integrity, and augmenting the activity of antioxidant enzymes compared to ‘Chaharfasl’. The utilization of nSiO2 and AnE biostimulants demonstrated potential benefits for R. damascena, both under salinity and control conditions. These findings hold substantial importance for researchers, policymakers, and farmers, offering valuable insights into the development of salinity-tolerant crop varieties.

Numerical simulation of an electromagnetic squeezing hybrid nanofluid flow through permeable plates with sensor monitoring system

The primary aim of this study is to examine the effect of squeezing hybrid nanofluids copper and magnetite with water flow across a horizontal surface under the impact of magnetic and radiative effects, which has extensive applications in the field of biomedical engineering and nanotechnology. Additionally, a microcantilever sensor is placed between the horizontal surfaces to surveil the flow behaviors. The equations pertaining to momentum and energy are reconstructed into a set of ordinary differential equations (ODEs). These ODEs are subsequently solved through a numerical approach, wherein the bvp4c solver from MATLAB is utilized. This solver employs a collocation technique for the numerical solution. As a result, the solutions acquired for velocity and temperature are graphically displayed for different parameters, including volume fraction of nanoparticles, squeezing flow index parameter (b), magnetic parameter (M), permeable velocity parameter (f0), radiation parameter R, and Prandtl number (Pr). It has been observed that increasing the magnetic effect as well as the volume fraction of nanoparticles strengthens the flow effect. In contrast, increasing the squeezing and permeable velocity parameter impedes the flow. When there is an increase in a permeable velocity parameter, the temperature shoots up, and the cooling effect is spotted in the temperature profile, when the Prandtl number and magnetic and squeezing parameters are raised. This investigation upholds the significance of drag reduction, flow instabilities, fluid structure interactions, and heat transfer effectiveness by virtue of wall shear stress, squeezing flow index parameter, various hybrid nanofluids, and Nusselt number, respectively. A considerable comparative study has been made for the validation of current results.

Study on the source parameters of the micro-earthquakes in Laohutai coal mine based on double difference relocation

Seismicity related to industrial mining activities needs to be understood and quantified in order to ensure safe mining operations. It is of great important to determine if the sources of such events follow the common models and theories, and determine the source rupture property and scale of such events. Moreover, the location of the source is very important to obtain the source parameters. For this purpose, we analyze 103 events recorded in the Laohutai coal mine that are related to fault structure and mining activities to determine their source properties based on relocation. Firstly, the 103 micro-earthquakes were relocated based on double difference algorithm. Then, the source parameters of seismic moment M0, source radius R, corner frequency f0, seismic attenuation Q, energy E, stress drop △σ and apparent stress σa are computed based on relocation, Brune model and grid-search method. The relationship between the other source parameters and seismic moment, the relationship between ML and Mw, and the influence of location on source parameters and magnitude are further analyzed. Finally, the difference of the source parameters between Laohutai coal mine, Qianqiu coal mine and natural earthquakes are analyzed. We find that the source location can be effectively corrected based on double difference algorithm; ω2 model is well suited to estimate source parameters of micro-earthquakes in the Laohutai coal mine. The source spectra show strong directivity effects. Stations in the rupture direction have higher corner frequencies, while stations away from rupture direction have lower corner frequencies. With the increase of M0, the source parameters of R, E and △σ basically show a linear increase, the source parameter f0 basically show a linear decrease and the apparent stress fluctuate up and down around a certain value as a whole. After relocation, the location of the source has a significant effect on the quality attenuation factor Q and has no obvious effect on other source parameters. The influence of relocation on moment magnitude and local magnitude is not obvious. The moment magnitude is linear with the local magnitude. Considering Mw, ML1 can relatively well be used to evaluate the magnitude of the earthquakes in Laohutai coal mine; For the micro-earthquakes with the same magnitude, the values of corner frequency, stress drop, apparent stress and energy in Qianqiu coal mine are greater than those in Laohutai coal mine, the value of source radius in Laohutai coal mine is greater than those in Qianqiu coal mine. For the events with the same magnitude, the corner frequency and the stress drop value of micro-earthquakes are smaller than those of natural earthquake. These indicate that the rupture properties and scales of micro-earthquakes in Laohutai coal mine are different from those of the micro-earthquakes in Qianqiu coal mine and natural earthquakes. The results help us to effectively evaluate the property and magnitude of microseismic source, and better understand causes and consequences of microseismicity in coal mine.

Response of Kostiakov-Lewis Infiltration Parameters to Soil Physical-Chemical Properties in the Loess Plateau of China

In order to know the main factors influence the infiltration parameters, based on the 344 sets of double-ring infiltration experiments in 101 different experimental sites in the Loess Plateau, obtained a large sample of Kostiakov-Lewis infiltration model parameters, analyzed the relationship between infiltration parameters and soil properties, established a multiple linear model, a nonlinear model and a BP neural network model to predict the infiltration parameters. The results showed that through Pearson correlation analysis, the main factors for parameter k was bulk density, soil water content of 0-10 cm, sand content, silt content and organic matter of 0-20 cm, the main factors influence parameter α was water content, sand content, silt content of 0-40 cm, and bulk density of 20-40 cm, and the main factors for parameter f0 was water content, sand content, silt content, of 0-40 cm, bulk density of 10-40 cm, and organic matter of 0-20 cm. Compared with previous studies, this paper added soil organic matter content as an independent variable to study the effect of soil chemical properties on soil infiltration capacity, which makes the model more reasonable, higher accuracy, and better prediction effect. Based on the effective test, result error analysis and comprehensive analysis, it was feasible to obtain the infiltration parameters in the Kostiakov-Lewis model using three Pedo-transfer functions. Under the condition of comprehensive consideration of forecast accuracy and stability applicability, it was recommended to use the nonlinear model as the prediction model of soil water infiltration parameters in the Loess Plateau.

A new damage model accounting the effect of joint orientation for the jointed rock mass

Damage accumulation in the rock mass leading to failure is influenced by the properties of pre-existing discontinuities. In order to simulate rock mass behaviour realistically, many damage models have been proposed. Amongst them, limited damage models consider joint orientation, one of the significant properties of discontinuities impacting the rock mass failure, in the strongly anisotropic rock masses. In this study, we propose a statistical damage model using the Weibull distribution which takes into account joint orientation by incorporating the Jaeger’s and modified Hoek-Brown failure criteria for jointed rock masses. The proposed statistical damage model is validated using experimental results. Furthermore, verification of the proposed model is conducted by distinct element method using Particle Flow Code (PFC). To investigate the influence of the shape parameter (m) and scale parameter (F0) of the Weibull distribution on the statistical damage model predictions, a sensitivity analysis is carried out. It is found that the parameter m only depends on strain parameter k. On the other hand, the parameter F0 is indirectly related to the failure strength of the jointed rock mass in the proposed damage model. Considerable influence of joint stiffness on the damage variable D, damage evolution rate Dr and rock mass responses are also identified.

Zero-sound condensate in a Fermi liquid

We consider a normal Fermi liquid with a local scalar interaction given by the Landau parameter f0. The system becomes unstable for f0 < −1 against a growth of scalar-mode excitations (Pomeranchuk instability). We show that the instability may be tamed by the formation of a static Bose condensate of the scalar modes. We study a possible reconstruction of the isospin-symmetric nuclear matter owing to the appearance of the condensate. Possibility of a novel metastable state at subnuclear densities is demonstrated.

A Similarity Solution for Mixed-Convection Boundary Layer Nanofluid Flow on an Inclined Permeable Surface

This paper concerns with calculation of heat transfer and pressure drop in a mixed-convection nanofluid flow on a permeable inclined flat plate. Solution of governing boundary layer equations is presented for some values of injection/suction parameter (f0), surface angle (γ), Galileo number (Ga), mixed-convection parameter (λ), volume fraction (φ), and type of nanoparticles. The numerical outcomes are presented in terms of average skin friction coefficient (Cf) and Nusselt number (Nu). The results indicate that adding nanoparticles to the base fluid enhances both average friction factor and Nusselt number for a wide range of other effective parameters. We found that for a nanofluid with φ = 0.6, injection from the wall (f0 = −0.2) offers an enhancement of 30% in Cf than the base fluid, while this growth is about 35% for the same case with wall suction (f0 = 0.2). However, increasing the wall suction will linearly raise the heat transfer rate from the surface, similar for all range of nanoparticles volume fraction. The computations also showed that by changing the surface angle from horizontal state to 60 deg, the friction factor becomes 2.4 times by average for all φ's, while 25% increase yields in Nusselt number for the same case. For assisting flow, there is a favorable pressure gradient due to the buoyancy forces, which results in larger Cf and Nu than in opposing flows. We can also see that for all φ values, enhancing Ga/Re2 parameter from 0 to 0.005 makes the friction factor 4.5 times, while causes 50% increase in heat transfer coefficient. Finally, we realized that among the studied nanoparticles, the maximum influence on the friction and heat transfer belongs to copper nanoparticles.

Variable fluid properties analysis with water based CNT nanofluid over a sensor sheet: Numerical solution

Present study is dedicated to analyze the magnetohydrodynamics (MHD) squeezed flow of nanofluid over a sensor shell under the influence temperature dependent viscosity. This is the first article on the squeezed flow of water based CNTs over a sensor surface with variable viscosity. A well known Reynolds model of viscosity is used. Modeling of the problem is based on the geometry and the interaction of nanoparticles namely single wall and multi-wall carbon nanotubes with the consistent mixture of base fluid (water). The self-similar numerical solutions are presented for the reduced form of the system of coupled ordinary differential equations. The effects of nanoparticles volume friction, permeable velocity and squeezing parameter for the flow and heat transfer within the boundary layer are presented through graphs. Comparison among the solvent are constructed for both skin friction and Nusselt number. Flow behavior of the working nanofluid according to the present geometry has analyzed through stream lines. It is seen that when we increase Hartmann number M, viscosity parameter α and random constant b decreases temperature profile and thermal boundary layer thickness also decreases and increasing permeable velocity parameter f0 increases temperature profile and thermal boundary layer thickness also increases.

Analytical Solutions of Heat Problems for Efficient Heat Transfer in a Nanofluid

To find the approximate solutions of heat equations in a boundary layer flow, beneath a uniform free stream permeable continuous moving surface in a nanofluid is the main purpose of this paper. First, we will propose a neural network coupled with the Chebyshev polynomials. We will then study the heat transfer and heat flow equations by using the presented Chebyshev neural network. As it turns out, this method can obtain the approximate solutions for any kind heat transfer and heat flow equations. Approximate answers can be more helpful to study the behavior of heat transfer heat flow, and it can ensure a more efficient heat transfer with a lower operational cost. The missing slopes f rr(0) and gr(0), for some values of the governing parameters, namely the nano-particle volume fraction φ, the mov- ing parameter λ and the suction/injection parameter f0 are determined using the proposed method. The obtained results of this method have been compared with other papers results of different methods.

On the induction of injury in tomato under continuous light: circadian asynchrony as the main triggering factor.

Unlike other species, when tomato plants (Solanum lycopersicum L.) are deprived of at least 8h of darkness per day, they develop a potentially lethal injury. In an effort to understand why continuous light (CL) is injurious to tomato, we tested five factors, which potentially could be responsible for triggering the injury in CL-grown tomato: (i) differences in the light spectral distribution between sunlight and artificial light, (ii) continuous light signalling, (iii) continuous supply of light for photosynthesis, (iv) continuous photo-oxidative pressure and (v) circadian asynchrony - a mismatch between the internal circadian clock frequency and the external light/dark cycles. Our results strongly suggest that continuous-light-induced injury does not result from the unnatural spectral distribution of artificial light nor from the continuity of light per se. Instead, circadian asynchrony seems to be the main factor inducing the CL-induced injury, but the mechanism is not by the earlier hypothesised circadian pattern in sensitivity for photoinhibition. Here, however, we show for the first time diurnal fluctuations in sensitivity to photoinhibition during normal photoperiods. Similarly, we also report for the first time diurnal and circadian rhythms in the maximum quantum efficiency of PSII (Fv/Fm) and the parameter F0.

Heat transfer squeezed flow of Carreau fluid over a sensor surface with variable thermal conductivity: A numerical study

Present phenomenon is dedicated to investigate the heat transfer and squeezed flow of Carreau fluid over a sensor surface. The thermal conductivity of the fluid is assumed to be temperature dependent. After assimilating these assumptions, the appropriate transformations are used to formulate the partial differential equations into non-dimensional system of ordinary differential equations. Solutions for the boundary layer momentum and heat equations are accomplished by a well-known numerical technique namely shooting method. The related essential physical parameters are visualized through graphs and tables. It is found that the velocity profile increases by increasing squeezed flow parameter b, permeable velocity parameter f0, power law index n and Weissenberg number We Similarly, temperature profile increases by increasing small parameter ∊.

Modified MK model combined with ductile fracture criterion and its application in warm hydroforming

A modified MK model combined with ductile fracture criterion (DFC-MK model) is proposed to compute the forming limit diagrams (FLDs) of 5A06-O aluminum alloy sheet at different temperatures. The material constant (C) of ductile fracture criterion and initial thickness imperfection parameter (f0) at various temperatures are determined by using a new computing method based on wide sheet bending test. The FLDs at 20 and 200 °C are calculated through the DFC-MK model. The DFC-MK model, which includes the influence of through-thickness normal stress, is written into the subroutine VUMAT embedded in Abaqus/Explicit. The cylindrical cup hydroforming tests are carried out to verify the model. The results show that compared with experimental observations, the predicted FLDs based on DFC-MK model are more accurate than the conventional MK model; the errors between the simulations and experiments in warm hydroforming are 8.23% at 20 °C and 9.24% at 200 °C, which verify the effectiveness of the proposed model.

Unsteady Heat and Mass Transfer Near the Stagnation-point on a Vertical Permeable Surface: a Comprehensive Report of Dual Solutions

In this paper, the problem of unsteady mixed convection boundary layer flow of a viscous incompressible fluid near the stagnation-point on a vertical permeable plate with both cases of prescribed wall temperature and prescribed wall heat flux is investigated numerically. Here, both assisting and opposing buoyancy forces are considered and studied. The non-linear coupled partial differential equations governing the flow, thermal and concentration fields are first transformed into a set of non-linear coupled ordinary differential equations by a set of suitable similarity transformations. The resulting system of coupled non-linear ordinary differential equations is solved numerically by using the Runge–Kutta scheme coupled with a conventional shooting procedure. Numerical results are obtained for the skin-friction coefficient, Nusselt number and Sherwood number as well as for the velocity, temperature and concentration profiles for some values of the governing parameters, namely, the unsteadiness parameter A, permeability parameter f0 and mixed convection parameter λ. It is found that dual solutions exist for both assisting and opposing flows, and the range of the mixed convection parameter for which the solution exists, increases with suction and unsteadiness parameters.

Perceptual and acoustic parameters of vocal nodules in children

Vocal nodules constitute the major cause of dysphonia during childhood. Auditory-perceptual and acoustic vocal analyses have been used to differentiate vocal nodules from normal voice in children. PurposeTo study the value of auditory-perceptual and acoustic vocal analyses in assessments of children with nodules. DesignDiagnostic test study. Patients and interventionsA comparative study was carried out including 100 children with videolaryngoscopic diagnosis of vocal nodules (nodule group-NG); and 100 children without vocal symptoms and with normal videolaryngoscopic exams (control group-CG). The age range of both groups was between 4 and 11 years. All children underwent auditory-perceptual vocal analyses (GRBASI scale); maximum phonation time and s/z ratio were calculated, and acoustic vocal analysis (MDVP software) were carried out. ResultsThere was no difference in the values of maximum phonation time and s/z ratio between groups. Auditory-perceptual analysis indicated greater compromising of voice parameters for NG, compared to CG: G (79 versus 24), R (53 versus 3), B (67 versus 23) and S (35 versus 1). The values of acoustic parameters jitter, PPQ, shimmer, APQ, NHR and SPI were higher for NG for CG. The parameter f0 did not differ between groups. ConclusionCompromising of auditory-perceptual (G, R, B and S) and acoustic vocal parameters (jitter, PPQ, shimmer, APQ, NHR and SPI) was greater for children with nodules than for those of the control group, which makes them important methods for assessing child dysphonia.

Frequency Balance Influence to Signal-to-Noise Ratio of Bistable Stochastic Resonance in Signal Smart Regression Recognition Procedure

Systematic frequency holds great influence to bistable stochastic resonance (BSR) model. In this paper, frequency parameter f0 was investigated to explore the parameter-induced bistable stochastic resonance characteristic according to the former research results. Within a variable frequency parameter f0 range (from 0.01 to 10), a systematic output stochastic resonance emerged with the value change of frequency parameter f0. Systematic output signal-to-noise ratio (SNR) curve shows that the variable frequency parameter f0 could induce stochastic resonance in real-time signal analysis field

Mixed convection boundary layer flow past a wedge with permeable walls

The effects of suction/injection on steady laminar mixed convection boundary layer flow over a permeable horizontal surface of a wedge in a viscous and incompressible fluid is considered in this paper. The similarity solutions of the governing boundary layer equations are obtained for some values of the suction/injection parameter f0, the constant exponent m of the wall temperature as well as the mixed convection parameter λ. The resulting system of nonlinear ordinary differential equations is solved numerically for both assisting and opposing flow regimes using an implicit finite-difference scheme known as the Keller-box method. Numerical results for the reduced skin friction coefficient, the local Nusselt number, and the velocity and temperature profiles are obtained for various values of parameters considered. Dual solutions are found to exist for the case of opposing flow.

Worst cases for an one-hop high frequency link

The characterisation of a HF channel by means of monthly electron density profiles can be complemented with a detailed study of radio propagation «worst cases» on situations with extremes conditions of radiopropagation for a given period. These «worst cases» correspond to conditions that can be identified by means of cumulative distributions of the key parameter f0 F2. This paper analyses the main parameters of the HF channel: time delay, apogee, elevation angle and transmission frequency with mean and extreme conditions. The method used to characterise the ionospheric channel is based on ray-tracing techniques.

Falkner-Skan equation for flow past a moving wedge with suction or injection

The characteristics of steady two-dimensional laminar boundary layer flow of a viscous and incompressible fluid past a moving wedge with suction or injection are theoretically investigated. The transformed boundary layer equations are solved numerically using an implicit finite-difference scheme known as the Keller-box method. The effects of Falkner-Skan power-law parameter (m), suction/injection parameter (f0) and the ratio of free stream velocity to boundary velocity parameter (λ) are discussed in detail. The numerical results for velocity distribution and skin friction coefficient are given for several values of these parameters. Comparisons with the existing results obtained by other researchers under certain conditions are made. The critical values off 0,m and λ are obtained numerically and their significance on the skin friction and velocity profiles is discussed. The numerical evidence would seem to indicate the onset of reverse flow as it has been found by Riley and Weidman in 1989 for the Falkner-Skan equation for flow past an impermeable stretching boundary.

Turbulent sand jets in water

This Technical Note presents photographic observations of turbulent sand jets in water. Four sands, with mean diameters ranging from 0.17 to 1.47 mm. were used in combination with three nozzles of 8, 12.7 and 25.4 mm diameter. It was found that the linear growth rate of these sand jets increases with the parameter F0 which is proportional to the ratio of the momentum flux of the sand jet at the nozzle to buoyant force on the sand particles. For the largest value of F0 equal to about 15, the growth rate of the sand jet was 0.19 which is about 20% larger than that of turbulent water jets with Reynolds number larger than about 10,000.