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A theoretical and experimental study was conducted to investigate the effect of injection angle on surface waves. Linear stability theory was utilized to obtain the analytical relation. In the experimental study, high-speed photography and shadowgraph techniques were used. Image processing codes were developed to extract information from photos. The results obtained from the theoretical relation were validated with the experimental results at different injection angles. In addition, at the injection angle of 90 ∘ , the theoretical results were evaluated with the experimental results of other researchers. This evaluation showed that the theory results were in good agreement with the experimental data. The proper orthogonal decomposition (POD) and the power spectra density (PSD) analysis were also used to investigate the effect of the injection angle on the flow structures. The results obtained from the linear stability were used to determine the maximum waves' growth rate, and a relation was presented for the breakup length of the liquid jet at different injection angles. The breakup length results were compared with theory and published experimental data. The presented relation is more consistent with experimental data than other theories due to considering the nature of waves. The results showed that the instability of the liquid jet is influenced by three forces: inertial, surface tension, and aerodynamic. Therefore, Rayleigh–Taylor, Kelvin–Helmholtz, Rayleigh–Plateau, and azimuthal instabilities occur in the process. Decreasing the injection angle changes the nature of waves and shifts from Rayleigh–Taylor to Kelvin–Helmholtz. That reduces the wavelength and increases the growth rate of the waves. Axial waves have a significant impact on the physics of the waves and influence parameters. If axial waves are not formed, the growth rate of the waves is independent of the injection angle. An increase in the gas Weber number causes a change in the type of dominant waves and a greater instability of the liquid jet. In contrast, an increase in the liquid Weber number causes an enhancement in the resistance of the liquid jet against the transverse flow without changing the type of the dominant waves. Decreasing the density ratio reduces the effect of Rayleigh–Taylor waves and strengthens the Kelvin–Helmholtz waves. It causes two trends to be observed for the growth rate of waves at low spray angles, while one trend occurs at high spray angles. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of pre-cured and co-cured flowable composite liner on fracture strength and microleakage of primary anterior teeth with extended composite resin restorations. Methods: In the current in vitro experimental study, the crowns of 54 extracted primary canine teeth were cut 1 mm above the CEJ, and a pulpectomy procedure was performed. The samples were randomly divided into three groups to restore the coronal part up to 4 mm above the CEJ. In group 1, the samples were built up with Filtek Z250 packable composite resin. In group 2 (pre-cure), first, 1 mm of Filtek Z350 XT flowable liner was applied to the sample, and after curing, the restoration process continued using packable composite resin. In group 3 (co-cure), the flowable composite liner was cured while the first layer of packable composite resin was applied; then, the same restorative procedure similar to the other groups was followed. The samples' cross-sectional area in the fracture strength test was calculated by AutoCAD software. Subsequently, the samples were subjected to a force in a universal testing machine. The samples related to the microleakage experiment were cut vertically, and then, the dye penetration percentage (10% methylene blue) was measured under a stereomicroscope. ANOVA was used to analyze the data. Results: Mean fracture strength in group 2 was significantly higher than in group 1 (P = 0.016). The microleakage mean in group 3 was significantly lower than in groups 1 (P = 0.000) and 2 (P = 0.026). Conclusion: The flowable composite liner and its relevant separate curing increased the fracture strength of composite resin restorations. However, less microleakage was reported in the group where the liner was applied as a co-cure. [ABSTRACT FROM AUTHOR]

In the present study, an experimental approach is developed to study collisions of particles with a fixed air bubble. An air bubble with a diameter of 5.5 mm in deionized water is created, plastic particles (with diameters of 1.5, 2, and 2.5 mm) are released at different heights from the bubble surface, and their collisions with the bubble surface are studied. The results show that the particle size significantly affects the particle velocity and sliding time on the bubble surface. As the particle diameter increases, its sliding velocity on the bubble surface increases, and the particles are detached quickly from the bubble surface. The effects of the drag, capillary, pressure, weight, and buoyancy forces acting on the particles during the attachment-detachment on the bubble surface are also studied. The results show that the particle stays attached if the capillary force is dominant. The effects of the three-phase contact line on the capillary and pressure forces are also analyzed. A modified Bond number is proposed to check the attachment-detachment regimes. [ABSTRACT FROM AUTHOR]

Although there are several correlations for estimating the convective heat transfer coefficient (CHTC) of standalone buildings, the heat transfer properties of buildings arranged in tandem, staggered, or disorderly are not fully understood. In the current study, the CHTC of cubical buildings in several tandem and staggered configurations were studied in detail, using RANS numerical simulations. The simulations were performed for 60 different configurations, containing 5 different backward distances (B), 4 lateral distances (L), and 3 incident wind velocities (U10). Simulation results showed that the CHTC of the rear building increased with its distance from the front building when there was no lateral distance between the two buildings. For the staggered configuration, however, the CHTC of the rear building was affected by the wake structure of the front building. The simulation results also showed that the CHTC averaged on all facades of the rear building was proportional to U 10 0.911 for all the studied cases. Based on the presented numerical results, a correlation to estimate the average CHTC of the rear building as a function of the backward distance, lateral distance, and wind velocity was developed. [ABSTRACT FROM AUTHOR]

There is a lack of well-verified models in the literature for the prediction of the frictional pressure drop (FPD) in the helically coiled tubes at different conditions/orientations. In this study, the robust and universal models for estimating two-phase FPD in smooth coiled tubes with different orientations were developed using several intelligent approaches. For this reason, a databank comprising 1267 experimental data samples was collected from 12 independent studies, which covers a broad range of fluids, tube diameters, coil diameters, coil axis inclinations, mass fluxes, saturation temperatures, and vapor qualities. The earlier models for straight and coiled tubes were examined using the collected database, which showed absolute average relative error (AARE) higher than 21%. The most relevant dimensionless groups were used as models' inputs, and the neural network approach of multilayer perceptron and radial basis functions (RBF) were developed based on the homogenous equilibrium method. Although both intelligent models exhibited excellent accuracy, the RBF model predicted the best results with AARE 4.73% for the testing process. In addition, an explicit FPD model was developed by the genetic programming (GP), which showed the AARE of 14.97% for all data points. Capabilities of the proposed models under different conditions were described and, the sensitivity analyses were performed. [ABSTRACT FROM AUTHOR]

In this study, the carbon-doped zirconium dioxide (ZrO2-C) nanocatalyst was synthesized by sol-gel method and was used for the degradation of basic red 46 (BR46) in water. In order to optimize the dye removal efficiency, different experimental variables involving pH, ZrO2-C concentration, initial BR46 concentration, and light intensity were analyzed by the response surface methodology. Variance analysis showed high determination coefficient values, with R2 and adjusted-R2 of, respectively, 0.9984 and 0.9965, as well as, a satisfactory prediction of the second-order regression model. Optimization results showed a maximum color removal efficiency of 98.4% at the optimal condition with initial pH 11, ZrO2-C concentration =0.15 g/L, UV light intensity =18W and the initial dye concentration =5 mg/L. Finally, a new kinetic model, in the form of Langmuir-Hinshelwood equation, based on the intrinsic element reactions was developed. The results indicated that the developed DDR-II model fitted well with the experimental data and with a minimal value of the mean absolute relative residual (13.08%). [ABSTRACT FROM AUTHOR]

Six viroids have been reported to infect grapevine and among which only Grapevine yellow speckle viroid-1 (GYSVd-1) and Grapevine yellow speckle viroid-2 (GYSVd-2) are able to induce yellow speckle (YS) disease, characterized by yellowish flecks scattered on the leaf blade or massed along the veins. The mixed infection of GYSVd-1 or GYSVd-2 with Grapevine fanleaf virus (GFLV) may elicit vein banding (VB), a syndrome characterized by chrome-yellow flecks along the main veins of mature leaves and expanding through the interveinal tissues of infected leaves. In the present study, we have developed a multiplex RT-PCR (mRT-PCR) for simultaneous detection of GYSVd-1, GYSVd-2 and GFLV. Hop stunt viroid (HSVd), another viroid that infects most grapevines worldwide is used as a positive control instead of a host-derived internal control. The test developed in this study proved to be reliable for simultaneous detection of three pathogens, i.e. GYSVd-1, GYSVd-2 and GFLV in grapevine; hence it is useful for detection of YS and VB in large-scale surveys and certification programs. [ABSTRACT FROM AUTHOR]

This study describes a multidimensional 3D/lumped parameter (LP) model which contains appropriate inflow/outflow boundary conditions in order to model the entire human arterial trees. A new extensive LP model of the entire arterial network (48 arteries) was developed including the effect of vessel diameter tapering and the parameterization of resistance, conductor and inductor variables. A computer aided-design (CAD) algorithm was proposed to efficiently handle the coupling of two or more 3D models with the LP model, and substantially lessen the coupling processing time. Realistic boundary conditions and Navier-Stokes equations in healthy and stenosed models of carotid artery bifurcation (CAB) were used to investigate the unsteady Newtonian blood flow velocity distribution in the internal carotid artery (ICA). The present simulation results agree well with previous experimental and numerical studies. The outcomes of a pure LP model and those of the coupled 3D healthy model were found to be nearly the same in both cases. Concerning the various analyzed 3D zones, the stenosis growth in the ICA was not found as a crucial factor in determining the absorbing boundary conditions. This paper demonstrates the advantages of coupling local and systemic models to comprehend physiological diseases of the cardiovascular system. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Current work deals with experimental investigation, modeling, and optimization of friction stir welding process (FSW) to reach desirable mechanical properties of aluminum 7075 plates. Main factors of process were tool pin profile, tool rotary speed, welding speed, and welding axial force. Also, main responses were tensile strength, yield strength, and hardness of welded zone. Four factors and five levels of central composite design have been utilized to minimize the number of experimental observations. Then, adaptive neuro-fuzzy inference systems (ANFIS) have been used to generate mapping relationship between process factors and main response using experimental observations. Afterward, the developed models were applied as objective function to select optimal parameters, in which the process reaches to its desirable mechanical properties by using the simulated annealing algorithm. Results indicated that the tool with square pin profile, rotary speed of 1,400 RPM, welding speed of 1.75 mm/s, and axial force of 7.5 KN resulted in desirable mechanical properties in both cases of single response and multi-response optimization. Also, these solutions have been verified by confirmation tests and FSW process physical behavior. These verifications indicated that both ANFIS model and simulated annealing algorithm are appropriate tools for modeling and optimization of process. [ABSTRACT FROM AUTHOR]

The field equations of a second-order microcontinuum are discussed and the equation for the local entropy production of a second-order micro-elastic solid is obtained. A set of constitutive equations are also presented and discussed. [ABSTRACT FROM AUTHOR]

Starting from the Navier-Stokes equation, the evolution equation of the first order probability density functions of turbulence is derived. Closure assumptions for the pressure terms are introduced and the closed pdf equation is obtained. The resulting evolution equation takes the form of the Fokker-Planck equation and contains the existing Langevin based models as special cases. It is shown that the model predicts the known behaviors of turbulence in the limit of extremely high Reynolds number as well as a decaying turbulence. The moment equations are also examined. It is shown that the model is consistent with the recent second and third order closure models of turbulence. [ABSTRACT FROM AUTHOR]

A continuum theory of a two phase solid-fluid media is formulated. The basic balance laws for the solid phase as well as for the fluid phase are presented. Based on thermodynamical consideration a set of constitutive equations are derived and the basic equations of motions of the distributed solid and fluid continua are obtained and discussed. It is shown that the theory contains as its special cases, Mohr-Coulomb criterion of limiting equilibrium of granular materials, Saffman theory of dusty gas, as well as Darcy's law of flow through porous media. It is then concluded that the present theory covers the full spectrum of two phase solid-fluid media from low porosity granular media with Darcy's law of fluid motion to low and high concentration two phase flows such as dusty gas and blood flow. [ABSTRACT FROM AUTHOR]

Copyright of Acta Mechanica is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Mechanica is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We obtain criteria of stability of the unsteady motion of an incompressible Cosserat fluid in an arbitrary time-dependent domain, employing a general energy method due to J. Serrin. It is shown that the original motion is stable if R≦80 + 12800 C or if λ R≦80 + 6400 C. The quantities R and C are the Reynolds number and Cosserat number, respectively, and -λ is the lower bound for the eigenvalues of the strain rate tensor D. The theorems established for the stability criteria are universal in the sense that they do not depend either on the shape of the domain or on the distribution of the basic field variables. Finally an experimental scheme is proposed to determine the upper bound of the Cosserat number and consequently the characteristic length of a Cosserat fluid. [ABSTRACT FROM AUTHOR]