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Three dimensional (3D) unsteady, incompressible flows in a pump-turbine during a transient process of load rejection were studied using the computational fluid dynamics method. The dynamic mesh (DM) method and remeshing method combined with non-conformal grid boundaries were applied to simulate the rotation of guide vanes. The fluid coupling and DM method were used to calculate the rotational speed for each time-step. Calculations were performed based on the $$ \overline{{v^{2} }} - f $$ turbulence model to incorporate the near-wall turbulence anisotropy as well as non-local pressure–strain effects. Results show that $$ \overline{{v^{2} }} - f $$ model is thought to be suitable to predict characteristics of the transient process during load rejection in a pump-turbine. The transient explicit characteristics, such as the flow-rate, head, torque of the runner, etc., during the process of load rejection are analyzed. Pressure fluctuation was larger in the region close to the runner during the load rejection. Stalls and reverse flow in the runner resulted in the decrease of the torque of runner at turbine mode and turbine-braking mode. Simulation results were also compared and verified by experimental results. 3D simulations can be used instead of experiments to study the influence of inner flow to the external characteristics during transient processes. This calculation was based on a prototype of a pumped storage power station, and the computational method could be used in the fault diagnosis of transient operation. [ABSTRACT FROM AUTHOR]

This paper reports the simulation results for the unsteady cavitating turbulent flow in a Francis turbine using the mixture model for cavity-liquid two-phase flows. The RNG k- ε turbulence model is employed in the Reynolds averaged Navier-Stokes equations in this study. In the mixture model, an improved expression for the mass transfer is employed which is based on evaporation and condensation mechanisms with considering the effects of the non-dissolved gas, the turbulence, the tension of interface at cavity and the effect of phase change rate and so on. The computing domain includes the guide vanes, the runner, and the draft tube, which is discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The finite volume method is used to solve the governing equations of the mixture model and a full coupled method is combined into the algorithm to accelerate the solution. The computing results with the mixture model have been compared with those by the single-phase flow model as well as the experimental data. The simulation results show that the cavitating flow computation based on the improved mixture model agrees much better with experimental data than that by the single-phase flow calculation, in terms of the amplitude and dominated frequency of the pressure fluctuation. It is also observed from the present simulations that the amplitude of the pressure fluctuation at small flow rate is larger than that at large flow rate, which accords with the experimental data. [ABSTRACT FROM AUTHOR]

The Ge-Zr system is assessed by means of calculation of phase diagram (CALPHAD) approach, supplemented with decisive experiments and enthalpies of formation computed via Vienna ab initio simulation package (VASP) code. Nine Ge-Zr alloys were prepared by arc melting the pure elements. The annealed samples were analyzed by means of XRD, optical microscopy, and SEM/EDX. Five compounds are observed in the equilibrium condition. The enthalpies of formation for ZrGe, ZrGe, and ZrGe are computed via first-principles calculations. These enthalpies of formation are used as key 'experimental data' in the CALPHAD approach in order to obtain the thermodynamic parameters with sound physical meaning. A consistent thermodynamic data set for the Ge-Zr system is finally obtained based on the present work and the literature data. Comparisons between the calculated and measured phase diagram and thermodynamic quantities show that the accurate experimental information is satisfactorily accounted for by the present thermodynamic description. [ABSTRACT FROM AUTHOR]

The Sr-M (M = Fe, Mn, Ni, Ti, V) systems have been modeled by means of the calculation of phase diagram (CALPHAD) technique, wherein the thermodynamic parameters of NiSr (the only intermetallic compound in the five systems), liquid, (αSr), (βSr), (αFe), (γFe), (δFe), (αMn), (βMn), (γMn), (δMn), (Ni), (αTi), (βTi) and (V) are obtained by using the experimental data. The gas phase for the three binary systems, Sr-Mn, Sr-Ti and Sr-V is treated with the ideal gas model. Comparisons between the calculated and measured phase diagrams show that the experimental information is satisfactorily accounted for by the present thermodynamic description. [ABSTRACT FROM AUTHOR]

The phase equilibrium and thermodynamic data on the Mn-B system are critically reviewed. Based on the experimental data, a thermodynamic modeling is performed on this system. A set of self-consistent thermodynamic parameters is obtained and the calculated results are in general agreement with the experimental data. A parameter ξ is introduced to compare the degree of flatness of the δMn/L liquidus with those in other metal-boron systems. It is found that the δMn/L liquidus is the flattest, which causes difficulties in its modeling. An effective approach to evaluate the thermodynamic parameters for o-Mn2B0.982 phase is developed. Such an approach is valid for evaluating thermodynamic parameters of the phases with limited phase diagram data. [ABSTRACT FROM AUTHOR]

Abstract  Our previous studies have demonstrated that ciliary neurotrophic factor, a member of the interleukin-6-type cytokine superfamily, could inhibit the differentiation of myoblasts into mature myotubes at a certain concentration. In this study, another two members, interleukin-6 and leukemia inhibitory factor, together with ciliary neurotrophic factor were tested their roles in the proliferation and differentiation of myoblasts derived from the adult human skeletal muscles, in order to confirm that these cytokines might be a new type of regulatory factors on the myoblasts. The results showed that the effects of interleukin-6, leukemia inhibitory factor, and ciliary neurotrophic factor on the proliferation and differentiation of adult human myoblasts were different. Leukemia inhibitory factor in the dose of 10 ng/ml could accelerate the cell proliferation. Leukemia inhibitory factor in the dose of 10 or 50 ng/ml and ciliary neurotrophic factor in the dose of 10 or 50 ng/ml could inhibit the myoblast differentiation. The inhibition mechanism might be that leukemia inhibitory factor and ciliary neurotrophic factor inhibited the expressions of transcription factor MyoD/myf5, which could regulate the myoblast differentiation. This study will provide the experimental and theoretic foundations for the basic and clinical researches about human myoblasts. [ABSTRACT FROM AUTHOR]

CA1 pyramidal neurons degenerate after transient forebrain ischemia, whereas neurons in other regions of the hippocampus remain intact. Here we show that in rat hippocampal CA1 neurons, forebrain ischemia induces the phosphorylation of the N-methyl-D-aspartate (NMDA) receptor 2A subunit at Ser1232 (phospho-Ser1232). Ser1232 phosphorylation is catalyzed by cyclin-dependent kinase 5 (Cdk5). Inhibiting endogenous Cdk5, or perturbing interactions between Cdk5 and NR2A subunits, abolished NR2A phosphorylation at Ser1232 and protected CA1 pyramidal neurons from ischemic insult. Thus, we conclude that modulation of NMDA receptors by Cdk5 is the primary intracellular event underlying the ischemic injury of CA1 pyramidal neurons. [ABSTRACT FROM AUTHOR]

Provides information on a study which examined two open reading frames of bovine foamy virus. Materials and methods; Results and discussion.