Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The aeronautical sector is strategically important for the economic development of Mexico and has grown steadily over the last 10 years. Furthermore, it generates high added value for its products. In Mexico, the aircraft manufacturing sector mainly focuses on the fabrication of heat exchangers, seals, fuel ducts, and engine support rings. Currently, this sector is not involved in the manufacture of engine hot section components such as combustion chambers and turbine blades. Estimation of the associated costs enables assessment of the feasibility of fabricating such components. This study investigates the feasibility of establishing production lines for aeronautical combustion chamber fabrication in factories dedicated to the manufacture of aeronautical gas turbine engines.

Lamina and laminate mechanical properties of materials suitable for flywheel high-speed energy storage were investigated. Low density, low modulus and high strength composite material properties were implemented for the constant stress portion of the flywheel while higher density, higher modulus and strength were implemented for the constant thickness portion of the flywheel. Design and stress analysis were used to determine the maximum energy densities and shape factors for the flywheel. Analytical studies along with the use of the CADEC-online software were used to evaluate the lamina and laminate properties. This study found that a hybrid composite of M46J/epoxy–T1000G/epoxy for the flywheel exhibits a higher energy density when compared to known existing flywheel hybrid composite materials such as boron/epoxy–graphite/epoxy. Results from this study will contribute to further development of the flywheel that has recently re-emerged as a promising application for energy storage due to significant improvements in composite materials and technology.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief.

Spiking patterns observed at the output of lasers have been widely used to predict their dynamic behavior. The light output of a laser was associated with the coordinate of a particle moving in a potential well by Kleinman (1964). In this paper, this mechanical analogy is revisited so as to investigate a new approximation which might greatly simplify the relationships that determine the rate equations’ parameters. A ruby laser numerical example is presented to highlight the consistency of the proposed approximation near the equilibrium point.

During their use, optical fibers are subject to harsh installation and environmental conditions. To evaluate more precisely the lifetime of an optical fiber, it is necessary to study the mechanical behavior of optical fibers under extreme conditions, in particular under mechanical and thermal stresses.This paper presents the results of new silica optical fibers aged in hot water between 20◦C and 70◦C and subjected to mechanical static bending stresses from 3 GPa to 3.5 GPa. Thermal dependence of the time to failure was observed. This dependence can be described by the Arrhenius model, where the activation energy is one of the main physical characteristic. The stress corrosion parameter also seems to regularly change with temperature.

Cadmium selenide nanoparticles (NPs-CdSe) were synthesized by colloidal route at room temperature and atmospheric pressure using cadmiumchloride (CdCl2·2.5 hydrate) and elemental selenium (Se) as precursors. Sodium borohydride (NaBH4) was used as reducing agent to obtain Se2− ions and an aqueous solution with a NaOH and Penta sodium tripolyphosphate (STPP) was used to protect Cd2+ ions. To remove the by-productsgenerated during the chemical reaction and to promote the precipitation of NPs-CdSe, a cleaning process with an aqueous solution of HCl wasperformed. The HCl volume was varied from 0.2 to 1.2 ml during the cleaning process to study its effects on CdSe synthesis. The crystallinestructure was analyzed by inspection of the high-resolution transmission electron microscope (HR-TEM) and X-ray diffraction (XRD). Thisanalysis showed that crystals of CdSe exhibit a face-centered cubic structure (FCC). The calculated crystallite size is 3.5 nm and increases to4.5 nm as the HCl volume increases. The morphologies of the products were observed by SEM and TEM techniques. HRTEM images showed thatNPs-CdSe synthetized to 0.8 ml are composed of a great number of homogeneous and smooth nanospheres which are not appreciable in SEM butare observable in TEM. By contrast, 0.2 and 1.2 ml HCl samples are comprised of a great deal of rods of compounds of Se mixed with CdSe spheresnanostructures. This work, which did not require the use of surfactants complexes or specials environment, is considered to have advantages overother works.

Chemical methods are the most convenient and economical for wax precipitation and deposition prevention. The chemical additives so far in use have varied limitations, ranging from high cost to limited spread of crude oil that a particular additive can handle. The influence of cheaper natural chemicals, obtained from plant seeds (jatropha – JSO, rubber – RSO and castor – CSO) on the rheological properties and wax deposition tendencies of Nigerian waxy crude oil were investigated. Previously tested synthetic chemical additives (triethanolamine – TEA and xylene) were simultaneously examined too on the crude oils for comparative study. Four different crude oil samples obtained from Niger Delta region of Nigeria used for the study were characterized to obtain their hydrocarbon composition, wax content, pour points, viscosities, specific gravity and APIg using standard methods. The rheological properties such as apparent viscosity, plastic viscosity, yield stress were determined for the crude oils doped and undoped with the chemical additives using Fann V-G Standard Viscometer. The results obtained revealed that oils from the three seeds could be used as flow improvers and pour depressants for Nigerian waxy crude oil. Jatropha and castor seed oils depressed the pour point than the previously investigated triethanolamine. They are capable of depressing the pour point up to about 17◦C, and they can also reduce the viscosity of the waxy crude oil appreciably within 0.1–0.3% (v/v) dosage concentration. Also, CSO could exhibit as high as 77.7% paraffin inhibition efficiency (PIE) and JSO 73.5% at low concentration of doping.

Many lagoon systems in Mexico, and generally in developing countries, do not meet the norm for water pouring into receptors bodies. It wasapplied mathematical modeling to optimize the design and cost of a maturation pond, considering the methodology adopted for Mexico by theNational Water Commission, taking as variables the hydraulic retention time and the number of screens, then the results were compared with atraditional design of a maturation pond without screens. Both analyses fulfill the treated water quality standards for pouring into receptors bodies.The results show a reduction in the hydraulic retention time by 8.65 days, and a reduction by 48.16 percent in land requirement. About the cost, itwas obtained a reduction of 42.24 percent in comparison whit the traditional method. A major advantage of the mathematical model is the obtainingof the optimal design, which would be very difficult to get with the traditional methodology because the process is iterative and uses more thanone variable, also can be inferred that the use of screens increases the efficiency. The algorithm used was the interior point by Matlab’s Fminconfunction, which determines the optimal values to accomplish the water quality constraints and obtains the lowest possible cost for construction. Itis included the sensitive analysis for the mathematical model. It is recommended to carry out the present research at real scale with the finality tocheck the results given by the optimization.

Saturation of the magnetic core of transformers in a power system is an important effect that can be attributed to solar Geomagnetic InducedCurrents (GICs). This saturation can conduce to voltage-control problems, generating harmonic currents, and heating of the transformer internalcomponents, leading to gas relay alarm/operation and possible damage. This paper presents an analog physical reduced scale model of GICs inpower transformers. The instrumentation employed to carry out this study consists of a single-phase reduced scale transformer, a controllablecurrent source, a resistive load and a data acquisition system. The work establishes not only that it is possible to model the behavior of magneticvariables and to extrapolate the results to large full size power transformers, but also provides insight into GICs generation and their effects onpower transformers. Obtained results are related to the non-linear behavior of GICs due to asymmetric saturation of the magnetic core in the powertransformer, where computational model simulation is not able to give acceptable outcomes. Results are discussed for several GICs magnitudes,which include voltage, current, harmonics waveforms, magnetic core point of operation, the behavior of the stray flow, instantaneous power andcore temperature.

Global solar radiation (GSR) is an essential parameter for the design and operation of solar energy systems. Long-standing records of global solar radiation data are not available in many places because of the cost and maintenance of the measuring instruments. The major objective of this work is to develop an ANN model for accurately predicting solar radiation. Two ANN models with four different algorithms are considered in the present study. Meteorological data collected for the last 10 years from five different locations across India have been used to train the models. The best ANN algorithm and model are identified based on minimum mean absolute error (MAE) and root mean square error (RMSE) and maximum linear correlation coefficient (R). Further, the present study confirms that prediction accuracy of the ANN model depends on the complete set of data being used for training the network for the intended application. The developed ANN model has a low mean absolute percentage error (MAPE) which ascertains the accuracy and suitability of the model to predict the monthly average global radiation so as to design or evaluate solar energy installations, where the meteorological data measuring facilities are not in place in India.