k. singh

In a centrifugal pump, the clearance flow is quite common due to the existence of clearance between the casing and impeller. Apart from the clearance, the impeller speed and flow rate have a significant impact on fluid frictional torque. This study uses experimental and numerical methods to investigate these dynamics. The experimental setup includes measurements of fluid frictional torque at various levels of axial clearance (0.6 mm, 1.2 mm, and 1.8 mm), flow rates (8 L/min, 10 L/min, and 12 L/min), and impeller speeds (800 rpm, 1000 rpm, and 1200 rpm). A 3-level, 3-factor factorial design (L27) is employed to systematically examine the impact of these factors on fluid frictional torque. Response Surface Methodology (RSM) and Artificial Neural Networks (ANNs) are utilized to capture complex parameter interactions, with optimization performed using a Desirability Function (DF). The analysis reveals a significant increase in fluid frictional torque with increasing axial clearance, impeller speed, and flow rate. The optimal operational parameters for minimizing fluid frictional torque in the centrifugal pump are identified as    and mm, achieving a minimum fluid frictional torque of 0.499 Nm

Physical and chemical changes caused by oxidative stress in the spermatozoa membrane can reduce spermatozoa function and even lead to death. Cystamine (NH2-CH2-CH2-SH, β-mercaptoethylamine) is a natural substance that modulates the endocrine and metabolic status of animals. This substance has antioxidant and anti-apoptotic effects by inducing intracellular cysteine accumulation. Cystamine is used to treat many diseases despite its many side effects. Sheep semen is sensitive to the stressful condition of chilling storage, which restricts semen storage for artificial insemination in commercial herds. The effect of cystamine on spermatogenesis is not yet fully understood. The present study aimed to investigate the effect of cysteamine addition to the sheep sperm extender during cooling storage on semen quality parameters. Sperm samples were collected from six Edilbayevskaya rams (2 and 3 years old, 70-85 kg). The samples were diluted by extender and supplemented with different concentrations of cysteamine (0, 1, 2, 5, and 10 mM) and cooled to 4ºC for 50 h. Motility parameters, membrane integrity, viability, lipid peroxidation, and mitochondrial activity of cooled semen were evaluated at 0, 25, and 50 h of cooling storage. Although cysteamine failed to affect semen quality at start time (0 hrs), extender supplementation with cysteamine improved sperm total motility, progressive motility, and mitochondrial membrane potential during storage periods (P≤0.01). Moreover, using 1 and 2 mM cysteamine functionally and viably improved (P≤0.01) sperm membrane compared to other treatments. Antioxidant potential (AOP), lipid peroxidation (LPO), and total glutathione (tGSH) (except AOP at 50 h) were significantly different after semen storage at 4 °C. Therefore, levels of AOP and tGSH were significantly increased by using cysteamine. Cysteamine supplementation (1 and 2 mM cysteamine) leads to lower levels of LPO (p<0.01) at 0, 25, and 50 h. Therefore, finding and using the best concentrations of cysteamine in a cooling extender could be effective in saving sheep semen against damages of the cooling storage process.

Using Galerkin vector approach closed-form analytic expressions for the displacements and stresses caused by a doublet source buried in a homogenous, isotropic, perfectly elastic half-space have been obtained. Further, the viscoelastic deformation field has been obtained by applying the correspondence principle of linear viscoelasticity, assuming the medium to be elastic in dilatation and Kelvin, Maxwell, or SLS (Standard linear solid) type viscoelastic in distortion. The effect of Poisson’s ratio on the deformation field due to a doublet source is examined in elastic half-space. The effect of relaxation time on displacement and stress fields is studied due to a doublet source in viscoelastic half-space. The variation of the displacements and stresses with the epicentral distance is studied graphically using MATLAB software. Stresses for a doublet with axis parallel to x-axis attain minimum value for Poissonian half- space. Viscoelastic displacements and stresses attain maxima for the Maxwell model and minima for the Kelvin model.

A mathematical model is presented to investigate the effects of sandiness, irregular boundary interfaces, heterogeneity and viscoelasticity on the phase velocity of Love waves. Geometry of the problem is consisting of an initially stressed viscoelastic layer with corrugated irregular boundaries, which is sandwiched between heterogeneous orthotropic semi-infinite half-space with initial stress and pre-stressed dry sandy half-space. Heterogeneity arises in the upper half-space is due to trigonometric variation in elastic parameters of the orthotropic medium. Inclusion of the concept of corrugated irregular viscoelastic layer clamped between two dissimilar half-spaces under different physical circumstances such as initial stress and heterogeneity brings a novelty to the existing literature related to the study of Love wave. Dispersion equation for Love wave is obtained in closed form. The obtained dispersion relation is found to be in well agreement with classical Love wave equation. Numerical example and graphical illustrations are made to demonstrate notable effect of initial stress, internal friction, wave number and amplitude of corrugations on the phase velocity of Love waves.

This paper studies the propagation of shear waves in a composite structure consisting of a piezoelectric layer perfectly bonded over a micropolar elastic half space. The general dispersion equations for the existence of shear waves are obtained analytically in the closed form. Some particular cases have been discussed and in one special case the relation obtained is in agreement with existing results of the classical –Love wave equation. The micropolar and piezoelectric effects on the phase velocity are obtained for electrically open and mechanically free structure. To illustrate the utility of the problem numerical computations are carried out by considering PZT-4 as a piezoelectric and aluminium epoxy as micropolar elastic material. It is observed that the micropolarity present in the half space influence the phase velocity significantly in a particular region.  The micropolar effects on the phase velocity in the piezoelectric coupled structure can be used to design high performance acoustic wave devices.