Electro-coalescence of an aqueous droplet at an oil-water interface

The coalescence of an aqueous droplet at an oil-water interface under an electric field has been investigated, with a view to quantify conditions that give rise to secondary droplet formation. Two patterns of drop-interface coalescence may occur: complete coalescence and partial coalescence. The former is obviously the desirable pattern for industrial coalescers. However in practice, the process of coalescence could actually produce smaller droplets, which become more difficult to remove, and hence undesirable. This is caused by either necking, due to extensive elongation of the droplet, or reaction to a fast and energetic coalescence and is referred to as partial coalescence. The volume of the droplets formed in this way has been analyzed as a function of the initial droplet size, electric field strength and the distance between the droplet and the interface. The expansion speed of the neck connecting the droplet and interface at the beginning of the pumping process has also been quantified. These results are useful in optimizing the electro-coalescence process.     

The effect of interfacial tension on secondary drop formation in electro-coalescence of water droplets in oil

The coalescence of water droplets in oils may be enhanced by application of an electric field. This approach is commonly used in the crude oil and petroleum industry to separate water from crude oil. However, the process could lead to the formation of fine secondary droplets during the process of coalescence. This is obviously undesirable, as it becomes more difficult to separate finer water droplets. In this work the effects of interfacial tension, manipulated by the use of surfactants, and electric field strength on the formation of secondary droplets are investigated. Two competing processes of necking and pumping determine whether secondary droplets are formed. The dimensionless groups Weber Number (describing droplet deformation and necking due to the electric field) and Ohnesorge Number (describing the pumping of water into the continuous phase in the process of coalescence) may be coupled to give a new dimensionless group WO, describing the volume fraction of secondary droplets that are formed. WO Number describes the ratio of the electrical stress energy that causes necking over the energy required for pumping the viscous fluid out of the droplets. For a wide range of interfacial tensions, brought about by the use of non-ionic and anionic surfactants and electric field strengths, a good unification of data is obtained. The outcome of this work will be useful for optimizing the design of the electro-coalescence systems.     

A tiny EBG‐based structure multiband MIMO antenna with high isolation for LTE/WLAN and C/X bands applications

This article proposes a compact multiple‐input multiple‐output (MIMO) antenna with the electromagnetic band gap (EBG) structures for mobile terminals. The proposed MIMO antenna is composed of two radiation patches in which diagonal and folded microstrip lines are utilized to control the frequency bands. The radiation patch, one EBG structure and a rectangular‐shaped ground plane are etched on both sides of the antenna. The EBG structures have been employed for reducing the mutual coupling between the antenna elements. As a result of the effect of these structures, the mutual coupling between the two elements is reduced by less than ?30 dB. The proposed antenna is implemented on an FR4 substrate with dimensions 20 × 10 × 1 mm³. According to measured results, frequency ranges of 2.2 to 3.6 GHz and 5.1 to 5.9 GHz with S₁₁ < ?10 dB and also 3.7 to 5 GHz and 8 to 12 GHz with S₂₂ < ?10 dB have been obtained. Moreover, measured S₁₂ and S₂₁ with values of less than ?30 dB for both Ports have been realized. Additionally, the envelope correlation and radiation efficiency of the purposed antenna are less than 0.09 and more than 82%, respectively.     

Full Adaptive Integral Backstepping Controller for Interior Permanent Magnet Synchronous Motors

This paper examines the speed control issue for fully unknown Interior Permanent Magnet Synchronous Motors (IPMSMs). A full adaptive controller is proposed to control the speed of these motors while all physical parameters, adaptive variation bounds, and the load torque are unknown. Applying a four‐step backstepping strategy, which constructs the infrastructure of the whole controller design, and utilizing proper Lyapunov functions leads to generating proper adaptive control rules. The desired control performance is basically satisfied by rejection of the load torque and motor uncertainties. Optimizing the performance criteria, integral tracking error signals have been taken into account in the backstepping procedure in order to enhance the efficiency, robustness, and reduced steady‐state errors. The closed‐loop system stability is analyzed and proved utilizing Lyapunov and Barbalat lemmas. To evaluate the high performance of the designed controller, an illustrative example is simulated whereas the obtained results confirm the efficient treatment of the proposed method for the fully unknown system. The comparison of the simulation results with one of the recent papers in the literature verifies the effectiveness of the proposed method.     

Design and simulation of type II fuzzy logic controller for capturing maximum wind energy

The main purpose of this paper is to capture the maximum output power of the wind turbine under various environmental conditions. To achieve this goal, the wind turbine model has been studied and analysed under both low-wind and high-wind circumstances and due to the noisy behaviour of the wind, type II fuzzy logic controller is used for this purpose. Simulations with MATLAB show that type II fuzzy logic controller has better performance than type I.