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

External spur gear drives are one of the most widely used in engineering applications. These transmissions can be enclosed in a casing and well lubricated, or work exposed to contaminating agents, as in the case of some transmissions in the construction industry, mining, agricultural machinery, etc. In these cases they are called open transmissions and their essential failure is the wear on the flank of the tooth, with subsequent fracture of the same. One of the most used ways to mitigate this failure is the use of high wear resistance materials or special lubricating greases. However, there is very little information in the gear literature about the influence of tooth geometry on the wear resistance of gear drives. In the present work, an analysis of the influence of tooth geometry on the wear resistance of spur external spur gear transmissions is made. The optimal values ​​of the toothing correction coefficient that minimize the relative slip between the teeth as a function of the number of teeth of the wheels are determined.

The present work shows the simulation and implementation of a "Neurocontroller" in a second order plant. The neural controller, also known as Neurocontroller, was implemented with a multilayer network, where the backpropagation of the error was developed through the "Backprogation" algorithm. The multilayer network, composed of a hidden layer and an output layer, was first simulated in Matlab to get the variation parameters, then it was simulated in Visual C++ to achieve the optimization. The architecture of this multilayer network was varied many times until reaching an optimal form that will be shown as the final architecture. Next, the simulation was done in LabVIEW 8.4, corroborating the simulations in Visual C++. Finally, the neural controller developed in LabVIEW was tested in real time, showing gratifying results and verifying its effectiveness despite simultaneous changes in the parameters.

A surface Kerr effect magnetometer (MEKS) was built to measure the magnetic properties of Permalloy (Ni81Fe19) thin films of 20 nm thickness. It was found that the coercive field of the samples has values between 2-6 Oe. The films showed in-plane uniaxial anisotropy and axes of easy and difficult magnetization were identified. The Kerr angle was measured for the longitudinal and polar configurations and the magnetic saturation for different angles of incidence of the light beam. The results were satisfactorily compared with those obtained with a Vibrating Sample Magnetometer (VSM).

In the drying process of activated clay there are two important methods that can be used to dry this activated clay: Rotator continuous drying and drying atomization. But to determine the characteristics and mechanism which intervene in the drying of clay is fundamental to use a batch tray drying. The objective of the present work is obtain the curve of drying velocity, fixing sorne initial conditions of humidity, and to define the mechanisms involved in the drying of activated clay with sulphuric acid. Further, this information will be used to scale to continuous drying and find out the equations which govern this process. It was necessary to use a tray of 214 cm2 surface area to charge moist bentonite. Samples were taken containing between 48 and 138 g, and initial humidity between 38 and 50%; to achieve a.final humidity of between about 8 and 13%. Graph of clay total mass (MT) versus drying time (0) show two periods: firstly a linear trend, followed by a no-linear trend. This second period consist of two stages, the first one consist in the formation of a rigid structure ar semi-rigid on the surface of the so/id. The second one consists in the removal of the moisture balance and this is frequently accompanied by an internal vaporization which can cause the so/id expansion. These drying characteristics are presented in graphic N°6 as a curve of drying velocity vs. solid humidity. These second period can be represented by the equation: Wc= 0.003463Xm^1.6556 .

For the best performance and longer duration of devices or elements that participate in a mechanical energy transport system, they require an adequate lubrication process in the areas exposed to friction: bearings, gears, cylinder-piston, etc. This process is very important for the optimal functioning of the system, since it reduces repair costs and unscheduled failures. One of the frequent problems of poor lubrication is generated by the Cavitation phenomenon, for this reason it is important to study its effects under operating conditions. In the present work, the formulation and numerical simulation of Cavitation in bearings is carried out, considering the variation of the viscosity of the lubricant in relation to the pressure and the distribution space. In other works carried out on this phenomenon, it is mentioned how complex it would be to develop a numerical process in a two-dimensional Cartesian system, due to the difficulties of non-linearity that exist in the formulation to obtain the explicit solution. Considering some results of [1. 2 and 3], the present study contributes with the explicit solution of the generated free border problem; For this, the Reynolds differential equation and the application of Barus's law for the viscous effect are reduced to a Poison-type partial derivative equation, which is transformed into an elliptic variational inequality of the first kind on a Soboley functional space. of order one. Then, a numerical resolution scheme is built on a two-dimensional computational domain, using the Galerkin method with finite elements and an improved Uzawa algorithm. Finally, the results that allow simulating the location of the Cavitation zone are presented.

The main objective of this study was to give a very simple approach to exposure levels from extremely low frequency fields (ELF) and radiofrequency (RF) electromagnetic fields from a sample of typical microwave ovens in Lima city, in arder to asses the compliance of emissions limits established by IEEE and the maximum exposure limits established as reference levels in the ICNIRP 's Guidelines. This work was carried out on a sample of 14 domestic microwaves ovens from different brands, installed in several office in INICTEL-UNI, in Lima city, in 2006. It consisted of a bibliographic research on biological and health efjects related to frequencies used in microwaves oven; a bibliographic research on emission and exposure limits; and measurements of ELF electric and magnetic fields at 60 Hz plus measurements of radiofrequency electric fields at 2. 4 GHz, evaluating them against international emission and exposure limits. In any case the measured values were in compliance with emission and exposure limits being coherent withfield values evaluated everywhere.

This paper presents the results of evaluating the vibration of a Building (Science Building / UNI) based on the Method of Laser Photo deflection. The evaluated vibrations of the building were, respectively, of spontaneous nature (produced by wind, automobile traffic, seismic waves) and induced (micro vibrations excited by sound waves). The procedure allowed us,to evaluate the following cases: a-A resonant effect occurred in the principal building Hall, b-Correlation of spontaneous and induced vibrations in the building, c-Detection and evaluation of building vibrations generated by Seismic waves.

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