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Lain S.,Autonomous University of Occidente
Indian Journal of Chemical Technology | Year: 2013

The present study deals with pneumatic conveying of spherical particles in a six meter long horizontal channel with rectangular cross-section from a numerical perspective. Calculations are done for spherical glass beads of different sizes with a mass loading of 1.0 kg particles/kg gas. Additionally, different wall roughnesses are considered. Air volume flow rate is kept constant in order to maintain a fixed gas average velocity of 20 m/s. The numerical computations are performed by the Euler/Lagrange approach in connection with a Reynolds stress turbulence model accounting for two-way coupling and inter-particle collisions. For the calculation of the particle motion, all relevant forces (drag, slip-shear and slip-rotational lift and gravity), inter-particle collisions and particle-rough wall collisions are considered. The agreement of the computations with the findings or earlier experiments are found to be satisfactory for mean and fluctuating velocities of both phases as well as for the normalized particle mass flux. Source

Nunez E.E.,Autonomous University of Occidente | Polycarpou A.A.,Texas A&M University
Wear | Year: 2015

Blended Polyetheretherketone (PEEK) and polyimide-based polymers are excellent lighter tribomaterials that make possible the replacement of sliding metallic components in machinery. In this work a quantitative analysis of the effect of surface roughness on the transfer of polymer films was investigated using a specialized tribometer, under air-conditioning and refrigeration specific operating conditions. Specifically, polyimide (Vespel SP-21), polyimide (Vespel SP-211), PEEK with carbon fibers, and Aromatic Thermosetting Polyester (ATSP) polymer pins were tested against gray cast iron disks under unlubricated unidirectional conditions. It was found that a continuous transfer layer of polymer on the surface of the cast iron disks with mirror finish (low surface roughness) was produced in all the combinations of tested blended polymers. In the case of the polymer pins tested against cast iron disks with high surface roughness, a discontinuous transfer layer was observed. © 2015 Elsevier B.V. Source

Zhang H.,Arizona State University | Vittal V.,Arizona State University | Heydt G.T.,Arizona State University | Quintero J.,Arizona State University | Quintero J.,Autonomous University of Occidente
IEEE Transactions on Power Systems | Year: 2012

The transmission expansion planning (TEP) problem in modern power systems is a large-scale, mixed-integer, non-linear and non-convex problem. Although remarkable advances have been made in optimization techniques, finding an optimal solution to a problem of this nature can still be extremely challenging. Based on the linearized power flow model, this paper presents a mixed-integer linear programming (MILP) approach that considers losses, generator costs and the $N - 1$ security constraints for the multi-stage TEP problem. The losses and generator cost are modeled as piecewise linear functions of the line flows and the generator outputs, respectively. The IEEE 24-bus system is used to compare the lossy and the lossless model. The results show that the lossy model provides savings in total cost in the long run. The selection of the best number of piecewise linear sections L is also shown. Then a complete planning framework is presented and a multi-stage TEP is performed on the IEEE 118-bus test system. Simulation results show that the proposed approach is accurate and efficient, and has the potential to be applied to large-scale power system planning problems. © 2012 IEEE. Source

Contreras J.P.,Autonomous University of Occidente | Ramirez J.M.,CINVESTAV
IEEE Transactions on Smart Grid | Year: 2014

This paper presents a Multi-Fed Power Electronic Transformer (MF-PET) for use in power distribution electrical systems. The MF-PET is a power electronic transformer with two or more AC/DC rectifiers at its input port, which may be connected to different feeders. Thus, it is possible to share the demand among feeders. Through a proper control, the AC/DC rectifiers may handle active power from the feeders (independently of the load type), may protect the load from sag/swell events, and may transfer power among feeders. This paper presents a three-phase MF-PET model. A small-scale laboratory prototype is shown and its application to distribution electrical system is discussed, exhibiting the MF-PET as a power electronic building block (PEBB) for its integration into electrical grids, enhancing the distribution system flexibility and contributing to the smart grid concept. © 2010-2012 IEEE. Source

Autonomous University of Occidente | Date: 2012-03-27

The invention relates to a ceramic biocomposite for bone regeneration, having a pH range of between 6.5 and 8.5, with an initial plasticity that allows the biocomposite to be easily moulded in situ and to set after 7 minutes, meaning that it can remain at the indicated location during the healing process. In addition, the biocomposite has demonstrated an ability to stimulate bone formation in hard-to-heal wounds. The material can act alone or in combination with other types of bone graft such as autografts, homografts or xenografts which act as a vehicle, as a binding material for endosseous prostheses or as a covering for endosseous implants or prostheses.

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