Soils with roots or root-like inclusions have often been tested in direct shear to quantify the effects of vegetation on the shear strength of soil, and in turn, the stability of slopes. However, a ...straightforward evaluation of root reinforcement is challenging due to the complex nature of roots, and the dependency of soil behaviour on many factors. An Inclinable Large-scale Direct Shear Apparatus (ILDSA) was built to study the shearing behaviour of root-permeated soils. Planted specimens, consisting of two different sets of species, were prepared with a moraine, sampled from a recent landslide location, and tested in direct shear subsequent to saturation. Relationships of peak stress ratio with dry weight of roots, maximum dilatancy angle and void ratio were investigated to evaluate the behaviour of root-permeated soil. The combined approach, of taking both presence of roots and dilatant behaviour of soil into consideration, results in a more realistic understanding and quantification of the effects of root reinforcement, at least, for laboratory testing of root-permeated soils.
•A recently developed large-scale direct shear apparatus has been introduced.•Saturated root-permeated soil specimens were tested.•Root growth mitigates change in void ratio.•Dilatancy and root biomass explain the most of the variation in shear strength.
Practically, every processing technology deals with complex multi-phase flows and predicting the fluid flow behavior is crucial for these processes. Current study discusses the application of a ...mesh-less numerical methodology, i.e. Incompressible Smoothed Particle Hydrodynamics (ISPH) to investigate the behavior of different multi-phase flow systems. This work is presented in a coherent way with increasing test problem difficulties and their concerned physical complexities. A wide range of problems including Laplace’s law, bubble rising, bubble suspension under an external electric field are considered for a code validation purpose, while the numerical results manifest very good accordance with the experimental and theoretical data. Finally, we show the effectiveness of using an external electric field for controlling a complex problem such as Couette flow for a range of electrical permittivity and electrical conductivity ratios. It is noted that the Electrohydrodynamics (EHD) effect on a suspended droplet in Couette flow case is simulated for the first time using the SPH method.
We have presented a multiphase incompressible smoothed particle hydrodynamics method with an improved interface treatment procedure. To demonstrate the effectiveness of the interface treatment which ...can handle multiphase flow problems with high density and viscosity ratios, we have modeled several challenging two phase flow problems; namely, single vortex flow, square droplet deformation, droplet deformation in shear flow, and finally the Newtonian bubble rising in viscous and viscoelastic liquids. The proposed interface treatment includes the usage of (i) different smoothing functions (in this work, cubic spline kernel function for discretizing equations associated with the calculation of the surface tension force while the quintic spline for the discretization of governing equations and the relevant boundary conditions), and (ii) a new discretization scheme for calculating the pressure gradient. It is shown that with the application of the improved interface treatment, it becomes possible to model multiphase flow problems with the density and viscosity ratios up to 1000 and 100 respectively while using standard projection method. The utilization of cubic spline for the continuum surface force model significantly improves the quality of the calculated interface, thereby eliminating the interphase particle penetrations, and in turn leading to the calculation of more accurate velocity and pressure fields.
A smoothed particle hydrodynamics (SPH) solution to the Rayleigh–Taylor instability (RTI) problem in an incompressible viscous two-phase immiscible fluid with surface tension is presented. The ...present model is validated by solving Laplace’s law, and square bubble deformation without surface tension whereby it is shown that the implemented SPH discretization does not produce any artificial surface tension. To further validate the numerical model for the RTI problem, results are quantitatively compared with analytical solutions in a linear regime. It is found that the SPH method slightly overestimates the border of instability. The long time evolution of simulations is presented for investigating changes in the topology of rising bubbles and falling spike in RTI, and the computed Froude numbers are compared with previous works. It is shown that the numerical algorithm used in this work is capable of capturing the interface evolution and growth rate in RTI accurately.
Genetic mutations in the leptin pathway can be a cause of human obesity. It is still unknown whether leptin can be effective in the treatment of fully established morbid obesity and its endocrine and ...metabolic consequences in adults. To test the hypothesis that leptin has a key role in metabolic and endocrine regulation in adults, we examined the effects of human leptin replacement in the only three adults identified to date who have genetically based leptin deficiency. We treated these three morbidly obese homozygous leptin-deficient adult patients with recombinant human leptin at low, physiological replacement doses in the range of 0.01-0.04 mg/kg for 18 months. Patients were hypogonadal, and one of them also had type 2 diabetes mellitus. We chose the doses of recombinant methionyl human leptin that would achieve normal leptin concentrations and administered them daily in the evening to model the normal circadian variation in endogenous leptin. The mean body mass index dropped from 51.2 ± 2.5 (mean ± SEM) at baseline to 26.9± 2.1 kg/ m2 after 18 months of treatment, mainly because of loss of fat mass. We document here that leptin replacement therapy in leptin-deficient adults with established morbid obesity results in profound weight loss, increased physical activity, changes in endocrine function and metabolism, including resolution of type 2 diabetes mellitus and hypogonadism, and beneficial effects on ingestive and noningestive behavior. These results highlight the role of the leptin pathway in adults with key effects on the regulation of body weight, gonadal function, and behavior.
•Two density-based iterative SPH methods are proposed for incompressible flows.•They eliminate non-physical pressure waves in density-based schemes.•Both proposed DTS-SPH and AL-SPH methods generate ...smooth pressure fields.
In this study, we have introduced two new iterative density-based Smoothed Particle Hydrodynamics (SPH) methods to model incompressible flows, namely, preconditioned dual time-stepping, and augmented Lagrangian method. The performance of these new methods are compared with each other and also with a modified version of the well-known weakly compressible SPH (WC-SPH) method through solving three carefully chosen incompressible flow problems: a laminar incompressible channel flow over a backward-facing step, a 2D stiff pressure decay problem and Taylor-Green vortices flow. For the first test problem, the results are compared with available data in literature. Moreover, it is observed that the two iterative methods provide a better accuracy in terms of smoother pressure field and also smaller magnitude of the velocity divergence across the computational domain. In the second test problem, it is shown that the preconditioned dual time-stepping and the augmented Lagrangian SPH methods yield rather smooth pressure fields, and converge to the exact solution, while the pressure field computed by the WC-SPH method oscillates even after very long time. As for the third test case, the iterative methods are compared with WC-SPH method for different iteration numbers and particle resolutions.
In this paper, the sine-cosine optimization algorithm (SCO) is used to solve the shape optimization of a vehicle clutch lever. The design problem is posed for the shape optimization of a clutch lever ...with a mass objective function and a stress constraint. Actual function evaluations are based on finite element analysis, while the response surface method is used to obtain the equations for objective and constraint functions. Recent optimization techniques such as the salp swarm algorithm, grasshopper optimization algorithm, and sine-cosine algorithm are used for shape optimization. The results show the ability of the sine-cosine optimization algorithm to optimize automobile components in the industry.
Pulmonary aspiration of gastric content is a serious complication of anesthesia. It is unclear what effects different parts of the menstrual cycle have on how long it takes for the stomach to empty. ...This prospective observational study assessed the relationship between menstrual cycle phases and gastric emptying using ultrasonography (USG) in volunteers of reproductive age.
Between days 8-10 of the menstrual cycle in the follicular phase and days 18-20 of the luteal phase, a total of 24 healthy volunteers received four stomach USG procedures. In both phases, the gastric antrum was evaluated with USG in the right lateral decubitus position after fasting for 10 hours, followed by 2 hours of fasting after liquid intake and 6 hours of fasting after solid food intake. The gastric content, gastric antrum area, and estimated gastric volume determined whether the stomach was full or empty.
A full stomach was detected in 8 (8.3%) out of 96 measurements performed on the volunteers. After liquid food intake, a full stomach was detected in 2 subjects in the luteal phase, while all the subjects had an empty stomach during the follicular phase (p=0.500). After solid food intake, a full stomach was detected in 6 subjects in the luteal phase, and again, all subjects had an empty stomach during the follicular phase (p=0.031).
Ultrasound assessment of gastric volume in volunteers of reproductive age has shown that gastric emptying of solid foods is slowed during the luteal phase of the menstrual cycle.
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