85 research outputs found
Heat and fluid flow in a scraped-surface heat exchanger containing a fluid with temperature-dependent viscosity
Scraped-surface heat exchangers (SSHEs) are extensively used in a wide variety of industrial settings where the continuous processing of fluids and fluid-like materials is involved. The steady non-isothermal flow of a Newtonian fluid with temperature-dependent viscosity in a narrow-gap SSHE when a constant temperature difference is imposed across the gap between the rotor and the stator is investigated. The mathematical model is formulated and the exact analytical solutions for the heat and fluid flow of a fluid with a general dependence of viscosity on temperature for a general blade shape are obtained. These solutions are then presented for the specific case of an exponential dependence of viscosity on temperature. Asymptotic methods are employed to investigate the behaviour of the solutions in several special limiting geometries and in the limits of weak and strong thermoviscosity. In particular, in the limit of strong thermoviscosity (i.e., strong heating or cooling and/or strong dependence of viscosity on temperature) the transverse and axial velocities become uniform in the bulk of the flow with boundary layers forming either just below the blade and just below the stationary upper wall or just above the blade and just above the moving lower wall. Results are presented for the most realistic case of a linear blade which illustrate the effect of varying the thermoviscosity of the fluid and the geometry of the SSHE on the flow
Modelling credit spreads with time volatility, skewness, and kurtosis
This paper seeks to identify the macroeconomic and financial factors that drive credit spreads on bond indices in the US credit market. To overcome the idiosyncratic nature of credit spread data reflected in time varying volatility, skewness and thick tails, it proposes asymmetric GARCH models with alternative probability density functions. The results show that credit spread changes are mainly explained by the interest rate and interest rate volatility, the slope of the yield curve, stock market returns and volatility, the state of liquidity in the corporate bond market and, a heretofore overlooked variable, the foreign exchange rate. They also confirm that the asymmetric GARCH models and Student-t distributions are systematically superior to the conventional GARCH model and the normal distribution in in-sample and out-of-sample testing
Experimental and numerical characterization of mixing in a hollow fiber membrane contactor by the iodide-iodate method
International audienc
Characterization of mixing in a hollow fiber membrane contactor by the iodide\textendashiodate method: Numerical simulations and experiments
International audienc
Experimental and numerical characterization of mixing in a hollow fiber membrane contactor by the iodide-iodate method
International audienc
Characterization of micromixing by the iodide-iodate method in a hollow fiber membrane contactor
International audienc
Inversion formulas for Riemann-Liouville transform and its dual associated with singular partial differential operators
We define Riemann-Liouville transform âα and its dual tâα associated with two singular partial
differential operators. We establish some results of harmonic
analysis for the Fourier transform connected with
âα. Next, we prove inversion formulas for the
operators âα, tâα and a Plancherel theorem for tâα
Inversion of the Riemann-Liouville operator and its dual using wavelets
We define and study the generalized continuous wavelet transform associated with the Riemann-Liouville operator that we use to express the new inversion formulas of the Riemann-Liouville operator and its dual
- âŠ