Potentiall of Ferulic Acid as a Precursor to Off-Flavors in Stored Orange Juice

The hypothesis that free ferulic acid in stored orange juice contributes to the objectional aroma of p-vinyl guaiacol (PVG) was tested. Single-strength orange juice (SSOJ) contained 185 μg/L free ferulic acid which increased to 316 μg/L after pasteurization. Commercial samples of SSOJ contained 3.7mg/L free ferulic when incubated at 35°C for 28 days; incubation at 50°C, resulted in 9.5 mg/L, while samples kept at 4°C contained 2.9 mg/L. Simultaneously, PVG content in SSOJ increased by 2-(35°C) to 3-(50°C) fold, while addition of ferulic acid accelerated formation of PVG. Inclusion of orange juice with added ferulic acid, produced a less acceptable aroma (laboratory taste panel) than juice incubated without added ferulic acid.     

Application of control volume based finite element method for solving the black-oil fluid equations

This is the second paper of a series where we introduce a control volume based finite element method （CVFEM） to simulate multiphase flow in porous media. This is a fully conservative method able to deal with unstructured grids which can be used for representing any complexity of reservoir geometry and its geological objects in an accurate and efficient manner. In order to deal with the inherent heterogeneity of the reservoirs, all operations related to discretization are performed at the element level in a manner similar to classical finite element method （FEM）. Moreover, the proposed method can effectively reduce the so-called grid orientation effects. In the first paper of this series, we presented this method and its application for incompressible and immiscible two-phase flow simulation in homogeneous and heterogeneous porous media. In this paper, we evaluate the capability of the method in the solution of highly nonlinear and coupled partial differential equations by simulating hydrocarbon reservoirs using the black-oil model. Furthermore, the effect of grid orientation is investigated by simulating a benchmark waterflooding problem. The numerical results show that the formulation presented here is efficient and accurate for solving the bubble point and three-phase coning problems.     

A control volume based finite element method for simulating incompressible two-phase flow in heterogeneous porous media and its application to reservoir engineering

Applying the standard Galerkin finite element method for solving flow problems in porous media encounters some difficulties such as numerical oscillation at the shock front and discontinuity of the velocity field on element faces.Discontinuity of velocity field leads this method not to conserve mass locally.Moreover,the accuracy and stability of a solution is highly affected by a non-conservative method.In this paper,a three dimensional control volume finite element method is developed for twophase fluid flow simulation which overcomes the deficiency of the standard finite element method,and attains high-orders of accuracy at a reasonable computational cost.Moreover,this method is capable of handling heterogeneity in a very rational way.A fully implicit scheme is applied to temporal discretization of the governing equations to achieve an unconditionally stable solution.The accuracy and efficiency of the method are verified by simulating some waterflooding experiments.Some representative examples are presented to illustrate the capability of the method to simulate two-phase fluid flow in heterogeneous porous media.     

A COMPARATIVE STUDY OF ACOUSTIC AND VIBRATION SIGNALS IN DETECTION OF GEAR FAILURES USING WIGNER–VILLE DISTRIBUTION

Vibration analysis is widely used in machinery diagnostics and the Wigner–Ville distribution has also been implemented in many applications in the condition monitoring of machinery. In contrast to previous applications, this paper examines whether acoustic signal can be used effectively to detect the various local faults in gearboxes using the smoothed pseudo-Wigner–Ville distribution. Three types of progressing local faults, broken tooth, gear crack and localised wear, were simulated. The results from acoustic signals were compared with vibration signals. The results suggest that acoustic signals are very affective for the early detection of faults and may provide a powerful tool to indicate the various types of progressing faults in gearboxes.