A theoretical model to predict cavitation inception in centrifugal pumps

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.This paper presents a theoretical model for the prediction of the incipient of cavitation in centrifugal pumps. The model includes the physical fluid parameters and the real working phenomena at off-design condition. The parameters considered in the model were flow rate ratio, pump rational speed, water temperature, thermodynamic properties of water, nuclei and gas content, relative velocity and incidence angle. The thermodynamic effect had a more complex expression compared with other parameters. The present model has been tested against extensive earlier published experimental results in centrifugal pumps at wide operating conditions. The comparison of the predicted net positive suction head at inception with the published data showed a good agreement was achieved. This agreement means that the roles played by operating parameters, off-design phenomena and thermodynamic properties of water are consistent with the present model. The results obtained from the present model make it possible to explain why there is a difference between the real net positive suction head values and the theoretical ones in the previous published models. Therefore, the present model could help the pump user and designer to estimate the incipient net positive suction head at various conditions.cs201

Non-metal sensory electrode design and protocol of DNA-nucleobases in living cells exposed to oxidative stresses

Sensory protocols for evaluation of DNA distortion due to exposure to various harmful chemicals and environments in living cells are needed for research and clinical investigations. Here, a design of non-metal sensory (NMS) electrode was built by using boron-doped carbon spherules for detection of DNA nucleobases, namely, guanine (Gu), adenine (Ad), and thymine (Th) in living cells. The key-electrode based nanoscale NMS structures lead to voids with a facile diffusion, and strong binding events of the DNA nucleobases. Furthermore, the NMS geometric structures would significantly create electrode surfaces with numerous centrally active sites, curvature topographies, and anisotropic spherules. The NMS shows potential as sensitive protocol for DNA-nucleobases in living cells exposed to oxidative stresses. In one-step signaling assay, NMS shows high signaling transduction of Gu-, Ad-, and Th-DNA nucleobases targets with ultra-sensitive and low detection limits of 3.0, 0.36, and 0.34 nM, respectively, and a wide linear range of up to 1 μM. The NMS design and protocol show evidence of the role of surface construction features and B-atoms incorporated into the graphitic carbon network for creating abundant active sites with facile electron diffusion and heavily target loads along with within-/out-plane circular spheres. Indeed NMS, with spherule-rich interstitial surfaces can be used for sensitive and selective evaluation of damaged-DNA to various dysfunctional metabolism in the human body

Final state predictions for J2 gravity perturbed motion of the Earth’s artificial satellites using Bispherical coordinates

AbstractIn this paper, initial value problem for dynamical astronomy will be established using Bispherical coordinates. A computational algorithm is developed for the final state predictions for J2 gravity perturbed motion of the Earth’s artificial satellites. This algorithm is important in targeting, rendezvous maneuvers as well for scientific researches. The applications of the algorithm are illustrated by numerical examples of some test orbits of different eccentricities. The numerical results are extremely accurate and efficient

Analytical formulations to the method of variation of parameters in terms of universal Y's functions

The method of variation of parameters still has a great interest and wide applications in mathematics, physics and astrodynamics. In this paper, universal functions (the Y's functions) based on Goodyear's time transformation formula were used to establish a variation of parameters method which is useful in slightly perturbed two-body initial value problem. Moreover due to its universality, the method avoids the switching among different conic orbits which are commonly occurring in space missions. The position and velocity vectors are written in terms of f and g series. The method is developed analytically and computationally. For the analytical developments, exact literal formulations for the differential system of variation of the epoch state vector are established. Symbolical series solution of the universal Kepler's equation was also established, and the literal analytical expressions of the coefficients of the series are listed in Horner form for efficient and stable evaluation. For computational developments of the method, an efficient algorithm was given using continued fraction theory. Finally, a short note on the method of solution was given just for the reader guidance

Spectroscopic and semiempirical investigation of the structural features of hetarylazo-5-isoxazolones tautomerism

3-Methyl-4-hetarylazo-5-isoxazolones (I–IV) have been synthesized and investigated on the basis of Fourier transform infrared (FT-IR), UV–visible (UV–Vis), proton nuclear magnetic resonance (1H NMR) spectroscopic techniques and elemental analysis. The measured FT-IR and 1H NMR spectra together with the theoretical calculations (semiempirical) showed that the investigated compounds exist in the hydrazone-keto form in the solid state and chloroform. However, the measured UV–Vis electronic absorption spectra in solutions clarified that the hetarylazo-5-isoxazolone dyes possess equilibrium between hydrazone-keto and common anion forms depending upon the nature of the medium. Furthermore, these dyes display a broad absorption band in the visible region (between 370 and 435 nm) which could be assigned to π–π∗ transition with a considerable intramolecular charge transfer (CT) character

Recent progress in marine foul-release polymeric nanocomposite coatings

Progress in materials science is associated with the development of nanomaterials in terms of energy-saving, environmentally friendly, and low-cost methods. Since the use of tributyltin compounds in antifouling coatings was banned in 2003, the search for ecofriendly alternatives has been promoted. Foul-release (FR) nanocoatings have been extensively investigated because of their non-stick, ecological, and economic advantages. Such nanocomposite systems are dynamic non-stick surfaces that deter any fouling attachment through physical anti-adhesion terminology. Instead of biocidal solutions, several functional FR nanocomposite coatings have been developed to counter biofouling and biocorrosion with ecological and ecofriendly effects. Selected inorganic nanofillers have been incorporated because of their enhanced interaction at the filler‐polymer interface for nanocomposites. Metallic nanoparticles and their oxides have also been widely explored because of their unique morphological characteristics and size-dependent, self-cleaning properties. In modeling a novel series of FR nanocoatings, two modes of prevention are combined: chemical inertness and physical microfouling repulsion for maritime navigation applications. Long-term durability and self-cleaning performance are among the advantages of developing effective, stable, and ecofriendly modeling alternatives. This review provides a holistic overview of nano-FR research achievements and describes recent advancements in non-stick marine nanocoatings for ship hulls. This review highlights the key issues of nanocomposite structures and their features in improving the biological activity and surface self-cleaning performance of ship hulls. This review may also open new horizons toward futuristic developments in FR nanocomposites for maritime navigations