Assessment of cement characteristics affecting rheological properties of cement pastes

Neural Computing and Applications - In this study, the cement-based parameters affecting CEMI portland cements-polycarboxylate ether-based high-range water-reducing (HRWR) admixtures compatibility...     

Velocity Uniformity of Microchannels in a Laminated‐Sheet Structure Under Parallel and Series Methods

An integral microchannel device is generally formed by lamination of multiple microchannel sheets. Uniform velocity distribution among the microchannels in each sheet shows a large influence on the device's performance. The effects of microchannel and manifold structure on the velocity uniformity in each sheet with different structural parameters under parallel and series laminated structures are investigated. For the laminated‐sheet structure where each sheet has the same structural parameters, a more uniform velocity distribution exists as compared to where the structural parameters are different. There exists a direct correlation between the velocity values in each sheet and structural parameters, whereas an inverse correlation is found under series laminated structure.     

Power loss calculation in two different multilevel inverter models (2DM)

This work investigates a general comparison of power loss between the neutral point clamped (NPC) and the multi-neutral points (MNP without clamping diodes) inverter models. Our goal in this study was to compare their respective efficiencies. For an NPC, four devices induce power losses: the switching devices (conduction and switching), the anti-parallel diodes, the clamping diodes and the DC link capacitors. For an MNP model, we have the same electrical devices for each phase except the clamping diodes. In this article, we discuss about two series of equations to estimate the power losses in NPC and MNP models. Finally, we present simulation results.     

Quasi-light-storage enhancement by reducing the Brillouin gain bandwidth

The quasi-light-storage (QLS) is a method for the variable and almost distortion free storage of optical data which is based on stimulated Brillouin scattering (SBS). The natural gain bandwidth of SBS limits the storage time of this method to up to 100?ns. We overcome this limit by the superposition of the SBS gain bandwidth with two losses. With this narrowed gain bandwidth, we were able to enhance the storage time for the QLS by 40%.     

A simple and accurate dynamical modeling of quantum‐dot semiconductor optical amplifiers

In this article, quantum‐dot semiconductor optical amplifiers (QD‐SOAs) have been modelled using state space method. To derive this model, we have manipulated the rate equation model of the QD‐SOA, where the average values of the occupation probabilities along the QD‐SOA cavity are considered as the state variables of the system. Using these variables, the distance dependence of the rate equations is eliminated. The derived state space model gives the optical gain and output signal of the amplifier with a high accuracy. Simulation results show that the derived model is not only much simpler and faster than conventional rate equation models, but also the optical gain and output signal of the investigated QD‐SOA are calculated with a higher precision compared to the rate equation model. Copyright © 2013 John Wiley & Sons, Ltd.     

A polymer electro-optic modulator with ultra wide-band and low driving voltage

In this paper, a polymer electro-optic modulator is designed and simulated using the full vectorial finite element method. First order edge elements are used in finite element implementation, and the finite element technique is used to obtain modulator response thoroughly. From the numerical analysis, frequency dispersions of modulator’s important parameters, such as microwave effective index nm , microwave characteristic impedance ZC and microwave loss a, are extracted. Our design exhibits elec...     

Studies on the essential oil from guarana

The essential oil from guarana [Paullinia cupana H.B.K. var. sorbilis (Mart.) Ducke] was analysed. Nine components were identified, namely (2) methylbenzenes, (1) cyclic monoterpene and (2) cyclic sesquiterpene hydrocarbons, (2) methoxyphenylpropenes and (2) alkylphenol derivatives. The alleged psychoactivity of the essential oil is presumably due to the identified constituents estragole and anethole. Any contribution of aminated metabolites of estragole/anethole to the alleged psychoactivity of the essential oil of guarana can be excluded. Neither the psychoactive 4-methoxyamphetamine nortert-aminoketones could be traced in human urine after oral application of guarana.     

Biofilm affected characteristics of porous structures

Formation of biofilm within a porous matrix reduces the pore size and the total open space of the system, altering the porosity and permeability of the medium. This change in the pore size distribution can be quantified by expressing the porous structure with a proper geometrical model. A set of pertinent multispecies biofilm models is used to arrive at the dynamic biofilm thickness distribution. The obtained results are utilized within a modified Kozeny–Carman framework to establish permeability and porosity distribution during the biofilm formation. The biofilm thickness and the obtained permeability profile for a special microorganism, Pseudomonas aeruginosa, are compared with available experimental data. The potential reasons attributing to the differences between the numerical and experimental data are discussed.     

An investigation of the thermal performance of cylindrical heat pipes using nanofluids

In this work, a two-dimensional analysis is used to study the thermal performance of a cylindrical heat pipe utilizing nanofluids. Three of the most common nanoparticles, namely Al₂O₃, CuO, and TiO₂ are considered as the working fluid. A substantial change in the heat pipe thermal resistance, temperature distribution, and maximum capillary heat transfer of the heat pipe is observed when using a nanofluid. The nanoparticles within the liquid enhance the thermal performance of the heat pipe by reducing the thermal resistance while enhancing the maximum heat load it can carry. The existence of an optimum mass concentration for nanoparticles in maximizing the heat transfer limit is established. The effect of particle size on the thermal performance of the heat pipe is also investigated. It is found that smaller particles have a more pronounced effect on the temperature gradient along the heat pipe.