Dynamics of secondary succession in a grassland ecosystem

Ph.D.Willard R. Fe

A Cautionary Note on Cosmological Magnetic Fields

This note is concerned with potentially misleading concepts in the treatment of cosmological magnetic fields by magnetohydrodynamical (MHD) modelling. It is not a criticism of MHD itself but rather a cautionary comment on the validity of its use in cosmology. Now that cosmological data are greatly improved compared with a few decades ago, and even better data are imminent, it makes sense to revisit original modelling assumptions and examine critically their shortcomings in respect of modern science. Specifically this article argues that ideal MHD is a poor approximation around recombination, since it inherently restricts evolutionary timescales, and is often misapplied in the existing literature.Comment: 5 page

A Robust Constrained Reference Governor Approach using Linear Matrix Inequalities

The purpose of this paper is to examine and provide a solution to the output reference tracking problem for uncertain systems subject to input saturation. As well-known, input saturation and modelling errors are very common problems at industry, where control schemes are implemented without accounting for such problems. In many cases, it is sometimes difficult to modify the existing implemented control schemes being necessary to provide them with external supervisory control approaches in order to tackle problems with constraints and modelling errors. In this way, a cascade structure is proposed, combining an inner loop containing any proper controller with an outer loop where a generalized predictive controller (GPC) provides adequate references for the inner loop considering input saturations and uncertainties. Therefore, the contribution of this paper consists in providing a state space representation for the inner loop and using linear matrix inequalities (LMI) to obtain a predictive state-vector feedback in such a way that the input reference for the inner loop is calculated to satisfy robust tracking specifications considering input saturations. Hence, the final proposed solution consists in solving a regulation problem to a fixed reference value subjected to a set of constraints described by several LMI and bilinear matrix inequalities (BMI). The main contribution of the paper is that the proposed solution is a non-linear setpoint tracking approach, that is, it is allowed that the system goes into saturation facing the problem of setpoint tracking instead of regulating to the origin. An illustrative numerical example is presented.Ministerio de Ciencia y Tecnología DPI2004-07444-C04-01/0

Producción de leche y consumo de materia seca de vacas Holstein en lactación consumiendo dietas bajas en fibra en el trópico

Three stargrass silage (SGS)-based diets formulated to contain 20, 26 and 32% neutral detergent fiber (NDF) were compared as to their effect on dry matter intake (DMI) and milk production. Twelve lactating Holstein cows averaging 110 days in milk were arranged in four replications of a 3 x 3 Latin Square design. Treatments did not affect DMI or DMI as percentage of body weight (BW); mean values for these parameters were 15.4 kg/cow/day and 3.06%, respectively. However, cows consuming 32% NDF diet had a tendency toward lower (8.6%) intake of organic matter (OM) as percentage of BW than cows on the 20% NDF diet. Intake of NDF as a percentage of BW increased (P < 0.01) linearly (0.62 to 0.93%) as dietary NDF concentration increased. Milk production averaged 21.0 kg/cow/day and was not affected by dietary treatment. Reducing dietary NDF from 32 to 20% resulted in a reduction (P < 0.01) in milk fat from 3.09 to 2.66%.This reduction resulted in a 1.3 kg/cow/day increase (P < 0.05) in 3.25% fat-corrected milk (3.25% FCM) as the percentage of dietary NDF increased. Gross efficiency of energy (NEL) use for milk production and 3.25% FCM increased linearly with dietary NDF by 9.7 and 17.3%, respectively. Results point out that for mid-lactation cows at the observed level of production, diets lower than 32% NDF will not result in higher DMI and milk production, and will be less efficient in the use of energy for milk production.Se compararon tres dietas basadas en ensilaje de yerba estrella formuladas para contener 20, 26 y 32% de fibra detergente neutro (FDN) para evaluar su efecto sobre el potencial de consumo de materia seca (MS) y producción de leche de vacas Holstein a media lactancia (110 días). Las vacas se asignaron a tratamientos de acuerdo con un diseño de cuadrados latinos de 3 x 3, replicado cuatro veces. Los tratamientos no tuvieron efecto sobre el consumo de MS y MS a base del porcentaje de peso vivo (PV) de la vaca; los promedios generales fueron 15.4 kg/vaca/día y 3.06% del PV, respectivamente. Sin embargo, las vacas que consumieron la dieta con 32% FDN exhibieron una tendencia a un menor (8.6%) consumo de materia orgánica (MO) como porcentaje del PV comparado con la dieta con 20% FDN. El consumo de FDN como un porcentaje del PV aumentó (P < 0.01) linealmente de 0.62 a 0.93% según aumentó la concentración de FDN. El promedio de producción de leche fue 21.0 kg/vaca/día y éste no se afectó por los tratamientos. La reducción de 32 a 20% en la concentración de FDN resultó en una reducción (P < 0.01) en la concentración de grasa láctea de 3.09 a 2.66%. Como resultado hubo un aumento de 1.3 kg/vaca/día en la producción de leche corregida al 3.25% de grasa, según aumentó el FDN de 20 a 32%. Al aumentar la concentración de FDN de 20 a 32% la eficiencia de la utilización de la energía (NEL) para la producción de leche y leche corregida al 3.25% de grasa se incrementó en un 9.7% (P < 0.05) y 17.3% (P < 0.01), respectivamente. Según los resultados de este estudio a los niveles de producción observados, las dietas con menos de 32% de FDN no tendrán un efecto sobre el consumo de MS ni sobre la producción de leche integra, aún cuando estas dietas resultan en un mayor consumo de energía. Además, estas dietas son menos eficientes en el uso de energía para la producción de leche

Laser marking of polymers. Work methodology

Laser marking of polymers. Work Methodology. Context The aim of this work is to obtain a work protocol for laser marking of polymers (figure 1). An in depth study regarding the ‘state of the art’ (articles, patents, books, dissertations) about the laser-polymer interaction, laser parameters, photo chemical/thermical processes, mechanical properties of polymers and optical characterization will be carried out. During laser marking, different phenomena can be observed from the most common photothermical processes to photochemical reactions. Those phenomena are not only due to the raw material, but also to different additives, wavelengths and laser parameters. This work will be developed with the resources available at the company B.S.H. (Balay) and the University of Zaragoza, mainly with the laser processing of materials group and the liquid crystals and polymers group. Initial proposal As starting materials for the study of laser marking, the following commercial polymers are proposed: ABS, SAN, PBT, PMMA and mainly PP. Regarding the irradiation following wavelengths are proposed: 1064, 532 and 355 nm covering IR, visible and UV spectra. Special interest will be paid to 355nm (UV) because in this range the possibilities of photochemical processes increases. Control of raw material There is a strong interest in controlling the raw material and additives, so alternatives for the production of different polymer plates will be studied; partially to identify the relationships between different phenomenology and additives. To control the raw material a profound knowledge of the quantitative and qualitative composition of the material is necessary. For the analysis various tools can be enhanced (XPS, ATR, EDX). Experiments According to the ‘state of the art’ different experiments are proposed, carrying them out on both, the raw material and the marks. The experiments fall into various investigation backgrounds, the different fields are shown below. . Design of experiments (DoE): parameter selection, factorial design. • Mathematical models: photo chemical/thermical rate, thermal models. • Mechanical properties: hardness and scratch resistance of the marks. • Temperature: measurement different tools • Morphology: roughness, appearance and depth of marks. • Optical characterization: Contrast and color distance (CIELab), absorption spectra. • Detection of photochemical/photothermical phenomena: carbonization, foaming, photo reduction, bond breaking, ablation, incubation, blocking. Importance of experimental results The experimental results must be discussed leading to conclusions. According to the conclusions the experiments can be accepted, discarded or adapted defining a solid work methodology suitable for a wide group of polymers

Auditing the Marketing and Social Media Communication of Natural Protected Areas. How Marketing Can Contribute to the Sustainability of Tourism

Natural Protected Areas face the challenge of conciliating attractions with satisfaction of their different stakeholders without compromising their own resources. Marketing can play an important role to this challenge from a macromarketing perspective. No studies are found in the literature on the integral assessment of marketing practices in Natural Protected Areas. For the first time, it proposes a marketing audit in Natural Protected Areas to fill that gap applying the Importance-Performance Analysis matrix, useful in strategic decisions, through interviews with directors of Natural Protected Areas. The main strengths, weaknesses, and deficits in the application of marketing are identified. The presence of a restricted and biased attitude towards marketing was noted among directors. In addition, the marketing behaviour is studied in two of the main social networks (Twitter/Facebook), comparisons were established in the USA, Spain, Italy and Mexico, identifying behavioural profiles in five groups in accordance with the 26 indicators under analysis