The viscous micropump consists of a cylinder placed eccentrically inside a microchannel, where the rotor axis is perpendicular to the channel axis. When the cylinder rotates, a net force is transferred to the fluid because of the unequal shear stresses on the upper and lower surfaces of the rotor. Consequently, this causes the surrounding fluid in the channel to displace toward the microchannel outlet. The simplicity of the viscous micropump renders it ideal for micropumping; however, previous studies have shown that its performance is still less than what is required for various applications. The performance of the viscous micropump, in terms of flow rate and pressure capabilities, may be enhanced by implementing more than one rotor into the configuration either horizontally or vertically oriented relative to each other. This is analogous to connecting multiple pumps in parallel or in series. The present study will numerically investigate the performance of various configurations of the viscous micropumps with multiple rotors, namely, the dual-horizontal rotor, triple-horizontal rotor, symmetrical dual-vertical rotor, and eight-shaped dual-vertical rotor. The development of drag-and-lift forces with time, as well as the viscous resisting torque on the cylinders were studied. In addition, the corresponding drag, lift, and moment coefficients were calculated. The flow pattern and pressure distribution on the cylinders' surfaces are also included in the study

Microchannels can separate analytes faster with higher resolution, higher efficiency and with lower reagent consumption than typical column techniques. Unfortunately, an impediment in the path toward fully integrated microchannel-based labs-on-a-chip is the integration of pre-separation sample processing. Although possible in microchannels, such steps are challenging because of the difficulty in maintaining spatial control over many reagents simultaneously. In contrast, the alternative format of digital microfluidics (DMF), in which discrete droplets are manipulated on an array of electrodes, is well-suited for carrying out sequential chemical reactions. Here, we report the development of the first digital-channel hybrid microfluidic device for integrated pre-processing reactions and chemical separations. The device was demonstrated to be useful for on-chip labeling of amino acids and primary amines in cell lysate, as well as enzymatic digestion of peptide standards, followed by separation in microchannels. Given the myriad applications requiring pre-processing and chemical separations, the hybrid digital-channel format has the potential to become a powerful new tool for micro total analysis systems

Digital microfluidics is a popular tool for lab-on-a-chip applications and is typically implemented in one of two formats: single-plate (“open”) devices or two-plate (“closed”) devices. Single-plate devices have some advantages relative to the more common two-plate format such as faster mixing, the capacity to move larger volumes on a given footprint, and easier access to droplets for handling or optical detection. In contrast with the two-plate format, in which ground potential is generally supplied via a top electrode, in the single-plate format, many different geometries of ground wires/electrodes have been used. Until the present study, there has been no metric to determine which of these geometries is best suited for droplet actuation. Here, we present a combination of numerical simulations and experimental tests to compare six different single-plate designs. We applied finite element analysis, using the commercially available COMSOL software package to calculate the electrodynamic actuation forces in each of the different designs and used the results to optimize device design. Forces predicted by the electrodynamic model were in agreement with forces predicted using electromechanical models. More importantly, results were verified experimentally using a unique technique that permits indirect estimation of actuation forces on digital microfluidic devices. This work illustrates the promise of using numerical modeling to enhance the design and performance of digital microfluidic devices.

The new process technologies developed during the last years made it possible to produce biodiesel from desert plants. From an economic point of view; the production of biodiesel is very feedstock sensitive. Many previous reports estimated the cost of biodiesel production based on assumptions, made by their authors, regarding production volume, feedstock and chemical technology. From a waste management standpoint, producing biodiesel from used frying oil is environmentally beneficial, since it provides a cleaner way for disposing these products; meanwhile, it can yield valuable cuts in CO2 as well as significant tail-pipe pollution gains. This paper introduces a review of some researches related to the production of biofuels from plants. The present study is focused on five types of plants which are castor, coconut, dates nucleus, jatropha and olive. Plants comparison in terms of growing conditions and how to convert each plant's oil to biofuels are presented. Chemical properties (heating value, flash point, viscosity……etc) of pure oil, oil mixing ratios with the petro diesel and for pure biofuels and also economic aspects are reviewed. The study leads to the best plants (castor and jatropha) for the production of biofuels in Egypt. The plants are appropriate to the circumstances of their agriculture with farming conditions in Egypt and non–edible. Biodiesel output from these plants has chemical properties approach to the chemical properties of petro diesel

The new process technologies developed during the last years made it possible to produce biodiesel from desert plants. From an economic point of view; the production of biodiesel is very feedstock sensitive. Many previous reports estimated the cost of biodiesel production based on assumptions, made by their authors, regarding production volume, feedstock and chemical technology. From a waste management standpoint, producing biodiesel from used frying oil is environmentally beneficial, since it provides a cleaner way for disposing these products; meanwhile, it can yield valuable cuts in CO2 as well as significant tail-pipe pollution gains. This paper introduces a review of some researches related to the production of biofuels from plants. The present study is focused on five types of plants which are castor, coconut, dates nucleus, jatropha and olive. Plants comparison in terms of growing conditions and how to convert each plant's oil to biofuels are presented. Chemical properties (heating value, flash point, viscosity……etc) of pure oil, oil mixing ratios with the petro diesel and for pure biofuels and also economic aspects are reviewed. The study leads to the best plants (castor and jatropha) for the production of biofuels in Egypt. The plants are appropriate to the circumstances of their agriculture with farming conditions in Egypt and non–edible. Biodiesel output from these plants has chemical properties approach to the chemical properties of petro diesel

The aim of the present work is to increase the limit of stability and improve the performance of an actual aircraft turbocharger compressor with different casing modifications. Three schemes of modifications in the shroud side of the compressor casing through the vaneless region; circumferential groove, protrude and combined of groove and protrude, were studied. The time variations of wall static pressure were observed using couple of pressure transducers with high frequency response in the vaneless region at different compressor operating conditions. Stall initiation and surge triggering were detected by analyzing both of the fluctuations of pressure signals and the power spectrum density (PSD) which deduced by using the Fast Fourier Transformation analysis (FFT). The number and speed of stall cells relative to the impeller speed were investigated. The flow angles, that are representing the stall initiation for the original compressor, were studied theoretically and experimentally. Both the theoretical and the experimental results were compared with those experimentally obtained by another author and show good agreements. The present measurements show that the inception of unsteady flow which leads to rotating stall initiation hence surge trigger appears at the vaneless region between the impeller exit and the diffuser vane leading edge. The modified casing by one way of the three-presented schemes can be used to increase the limit of stability for low speed compressor at different operating conditions. The compressor with groove height Hg = 0.2 and depth Tg = 0.2 gives about 55% and 39% improvement in stall margin, but unfortunately with decrease in the pressure coefficient at low flow rates. While the compressor achieves improvement between 14% and 26% in the range of stable operating based on surge margin and about 13% in pressure coefficient. Modification utilizing combination of groove and protrude achieves improvements of about 28% in stall margin, 22% in surge margin and 4% in maximum pressure coefficients

The aim of the present work is to increase the limit of stability and improve the performance of an actual aircraft turbocharger compressor with different casing modifications. Three schemes of modifications in the shroud side of the compressor casing through the vaneless region; circumferential groove, protrude and combined of groove and protrude, were studied. The time variations of wall static pressure were observed using couple of pressure transducers with high frequency response in the vaneless region at different compressor operating conditions. Stall initiation and surge triggering were detected by analyzing both of the fluctuations of pressure signals and the power spectrum density (PSD) which deduced by using the Fast Fourier Transformation analysis (FFT). The number and speed of stall cells relative to the impeller speed were investigated. The flow angles, that are representing the stall initiation for the original compressor, were studied theoretically and experimentally. Both the theoretical and the experimental results were compared with those experimentally obtained by another author and show good agreements. The present measurements show that the inception of unsteady flow which leads to rotating stall initiation hence surge trigger appears at the vaneless region between the impeller exit and the diffuser vane leading edge. The modified casing by one way of the three-presented schemes can be used to increase the limit of stability for low speed compressor at different operating conditions. The compressor with groove height Hg = 0.2 and depth Tg = 0.2 gives about 55% and 39% improvement in stall margin, but unfortunately with decrease in the pressure coefficient at low flow rates. While the compressor achieves improvement between 14% and 26% in the range of stable operating based on surge margin and about 13% in pressure coefficient. Modification utilizing combination of groove and protrude achieves improvements of about 28% in stall margin, 22% in surge margin and 4% in maximum pressure coefficients

The essential physical characteristics of the distinction of particles are size, shape and surface roughness. Particle shape and surface roughness are considered important parameters in the prediction of the behavior of particles individually or collectively. These parameters are of great importance to industries employing various materials in a powder form. These parameters have not been currently reviewed satisfactory in the mineral processing field. Therefore, this research is concerned with the different methods used to estimate the particle shape and surface roughness and also to relate these parameters with the behavior of some mineral processing operations, especially comminution and flotation processes. The surface roughness of mineral particle influences the fundamental processes of particle–bubble attachment and the other sub-processes in froth flotation. The contact angle is dependent on the surface roughness. The modification of the wettability due to surface roughness can be greatly enhanced in the fractal surface; that is the fractal surface will be superrepellen (superwettable) to a liquid when the contact angle is greater (less) than 90°. Correlations were found between the shape properties, surface roughness values and wettability. The dry grinding produces relatively rough particle surfaces with a high concentration of microstructural defects while the wet grinding produces smoother cleaner surfaces. The dry ground samples exhibited more stable, higher loaded froths and faster flotation kinetics.