Aprovechamiento de piñas de segunda, para la obtención de un zumo de piña comercial

La piña es originaria de las regiones tropicales de América del Sur sembrándose en Colombia, desde los tiempos precolombinos; pero fue solo hasta las últimas décadas del siglo XX que se extendió hasta cubrir áreas importantes de grandes explotaciones comerciales, principalmente en los departamentos de Santander, Valle, Cauca y Risaralda, este último ocupando en la actualidad, el segundo puesto en producción de frutas con una producción anual promedio de 400.000 toneladas después de la producción de cítricos con una producción anual de 500.000 toneladas, según informes del DANE (Jaramillo, 2013) De acuerdo al perfil nacional de consumo de frutas y verduras (2012), la piña se encuentra entre las 15 frutas más consumidas de Colombia y según el DANE a diciembre de 2015, entre Enero y Septiembre de este año se habían exportado 2,25 millones de dólares de esta fruta tropical, lo que representa un 7.6% en comparación con el año anterior, esto debido al interés actual de la población mundial por adquirir hábitos saludables (FAO, 2015) En Risaralda el sector frutícola ha contribuido, en la última década, a la diversificación y dinamismo de la agricultura, como consecuencia, en gran medida de la situación cafetera; siguiendo esta dinámica, en la búsqueda de producciones rentables y eficientes, considerando además que la capital risaraldense siempre se ha caracterizado por ser una zona rentable y de condiciones ambientales excelentes para la piña, se ha podido observar presencia de este cultivo, sin embargo por el cambio de uso de las tierras y por la cercanía al área urbana, su siembra ha disminuido. (MADR, 2006). En el ámbito local, el cultivo de la piña en Cerritos (Risaralda) es la fuente generadora de empleo más importante de esta zona proporcionando gran cantidad de empleos directos (Jaramillo, 2013)

Improving Stability Prediction in Peripheral Milling of Al7075T6

Chatter is an old enemy to machinists but, even today, is far from being defeated. Current requirements around aerospace components call for stronger and thinner workpieces which are more prone to vibrations. This study presents the stability analysis for a single degree of freedom down-milling operation in a thin-walled workpiece. The stability charts were computed by means of the enhanced multistage homotopy perturbation (EMHP) method, which includes the helix angle but also, most importantly, the runout and cutting speed effects. Our experimental validation shows the importance of this kind of analysis through a comparison with a common analysis without them, especially when machining aluminum alloys. The proposed analysis demands more computation time, since it includes the calculation of cutting forces for each combination of axial depth of cut and spindle speed. This EMHP algorithm is compared with the semi-discretization, Chebyshev collocation, and full-discretization methods in terms of convergence and computation efficiency, and ultimately proves to be the most efficient method among the ones studied.The authors wish to acknowledge the financial support received from HAZITEK program, from the Department of Economic Development and Infrastructures of the Basque Government and from FEDER funds. Additional support was provided by the Tecnologico de Monterrey, through the Research Group in Nanomaterials and Devices Design

Inspection scheduling based onreliability updating of gas turbinewelded structures

This article presents a novel methodology for the inspection scheduling of gas turbine welded structures, based on reliability calculations and overhaul findings. The model was based on a probabilistic crack propagation analysis for welds in a plate and considered the uncertainty in material properties, defect inspection capabilities, weld geometry, and loads. It developed a specific stress intensity factor and an improved first-order reliability method. The proposed routine alleviated the computational cost of stochastic crack propagation analysis, with accuracy. It is useful to achieve an effective design for manufacturing, to develop structural health monitoring applications, and to adapt inspection schedules to airplane fleet experience.We are grateful to the Mechanical Technology Department of ITPAero (R) for supporting and helping us with this study. The invaluable guidance and feedback from Jose Ramon Andujar is recognized with great appreciation

Toolpath dependent stability lobes for the milling of thin-walled parts

The milling of thin-walled parts can become a seriously complex problem because the parts have variable dynamics. Firstly, the dynamics evolution of the part has been calculated through Finite Element Method (FEM) analysis. Then, the 3D stability lobes have been calculated for the thin walls and the thin floor. Finally, several milling tests have been performed in order to validate the predictions made by the model

New Objective Refraction Metric Based on Sphere Fitting to the Wavefront

Purpose. To develop an objective refraction formula based on the ocular wavefront error (WFE) expressed in terms of Zernike coefficients and pupil radius, which would be an accurate predictor of subjective spherical equivalent (SE) for different pupil sizes. Methods. A sphere is fitted to the ocular wavefront at the center and at a variable distance, t. The optimal fitting distance, topt, is obtained empirically from a dataset of 308 eyes as a function of objective refraction pupil radius, r0, and used to define the formula of a new wavefront refraction metric (MTR). The metric is tested in another, independent dataset of 200 eyes. Results. For pupil radii r0≤2 mm, the new metric predicts the equivalent sphere with similar accuracy (2 mm, the mean error of traditional metrics can increase beyond 0.25D, and the MTR remains accurate. The proposed metric allows clinicians to obtain an accurate clinical spherical equivalent value without rescaling/refitting of the wavefront coefficients. It has the potential to be developed into a metric which will be able to predict full spherocylindrical refraction for the desired illumination conditions and corresponding pupil size

New Industry 4.0 Advances in Industrial IoT and Visual Computing for Manufacturing Processes: Volume II

The second volume of the Special Issue New Industry 4 [...

Intracapsular accommodation mechanism in terms of lens curvature gradient

The intracapsular accommodation mechanism (IAM) may be understood as an increase in the lens equivalent refractive index as the eye accommodates. Our goal was to evaluate the existence of an IAM by analysing observed changes in the inner curvature gradient of the lens. To this end, we fitted a gradient index and curvature lens model to published experimental data on external and nucleus geometry changes during accommodation. For each case analysed, we computed the refractive power and equivalent index for each accommodative state using a ray transfer matrix. All data sets showed an increase in the effective refractive index, indicating a positive IAM, which was stronger for older lenses. These results suggest a strong dependence of the lens equivalent refractive index on the inner curvature gradient

Historia de la lucha por la tierra en el Estado de México, 1915-1958 de Elvia Montes de Oca Navas

Reseña del libro Elvia Montes de Oca Navas, Historia de la lucha por la tierra en el Estado de México 1915-1958, Toluca, Biblioteca Mexiquense del Bicentenario, 2009, pp. 336

Implementation of ICT in Physical Education: advantages, limitations and new educational trends

Desde su origen, las Tic han sido consideradas una amenaza para la práctica de actividad física y, por ende, para el área de Educación Física y los hábitos saludables que esta materia fomenta. No obstante, son muchos los docentes que han destruido esta clásica enemistad y han introducido las Tic en la Educación Física de manera justificada. Esta renovación puede ser muy positiva, si bien precisa del buen hacer del docente, pues debe introducir las Tic de forma efectiva para lograr dos fines principales: facilitar el trabajo de los distintos tipos de contenidos y aumentar el tiempo de práctica física.From its earliest days, ICT have been considered a threat to the practice of physical activity and, therefore, for the area of Physical Education and the healthy habits that this subject promotes. However, there are many teachers who have destroyed this classic enmity and they have introduced justifiably the ICT in PE. This renewal can be very positive, although it requires a great effort from the teacher, as he must introduce the ICT to achieve two purposes: to facilitate the work of different type of contents and to increase the time of physical practice

Thin-Wall Machining of Light Alloys: A Review of Models and Industrial Approaches

Thin-wall parts are common in the aeronautical sector. However, their machining presents serious challenges such as vibrations and part deflections. To deal with these challenges, di erent approaches have been followed in recent years. This work presents the state of the art of thin-wall light-alloy machining, analyzing the problems related to each type of thin-wall parts, exposing the causes of both instability and deformation through analytical models, summarizing the computational techniques used, and presenting the solutions proposed by di erent authors from an industrial point of view. Finally, some further research lines are proposed