Sectional curvature and Weitzenb\"ock formulae

We establish a new algebraic characterization of sectional curvature bounds $\sec\geq k$ and $\sec\leq k$ using only curvature terms in the Weitzenb\"ock formulae for symmetric $p$-tensors. By introducing a symmetric analogue of the Kulkarni-Nomizu product, we provide a simple formula for such curvature terms. We also give an application of the Bochner technique to closed $4$-manifolds with indefinite intersection form and $\sec>0$ or $\sec\geq0$, obtaining new insights into the Hopf Conjecture, without any symmetry assumptions.Comment: LaTeX2e, 25 pages, final version. To appear in Indiana Univ. Math.

Strongly positive curvature

We begin a systematic study of a curvature condition (strongly positive curvature) which lies strictly between positive curvature operator and positive sectional curvature, and stems from the work of Thorpe in the 1970s. We prove that this condition is preserved under Riemannian submersions and Cheeger deformations, and that most compact homogeneous spaces with positive sectional curvature satisfy it.Comment: LaTeX2e, 26 page

Advanced Control for Energy Management of Grid-Connected Hybrid Power Systems in the Sugar Cane Industry

This work presents a process supervision and advanced control structure, based on Model Predictive Control (MPC) coupled with disturbance estimation techniques and a finite-state machine decision system, responsible for setting energy productions set-points. This control scheme is applied to energy generation optimization in a sugar cane power plant, with non-dispatchable renewable sources, such as photovoltaic and wind power generation, as well as dispatchable sources, as biomass. The energy plant is bound to produce steam in different pressures, cold water and, imperiously, has to produce and maintain an amount of electric power throughout each month, defined by contract rules with a local distribution network operator (DNO). The proposed predictive control structure uses feedforward compensation of estimated future disturbances, obtained by the Double Exponential Smoothing (DES) method. The control algorithm has the task of performing the management of which energy system to use, maximize the use of the renewable energy sources, manage the use of energy storage units and optimize energy generation due to contract rules, while aiming to maximize economic profits. Through simulation, the proposed system is compared to a MPC structure, with standard techniques, and shows improved behavior.Ministerio de Economía y Competitividad CNPq401126/2014-5Ministerio de Economía y Competitividad CNPq303702/2011-7Ministerio de Economía y Competitividad DPI2016-78338-

Between two Worlds: Representations of the Rural and the Urban in two Portuguese Municipalities

In a context of contemporaneousness in which there is little mention of the articulation between urban spaces and those with predominantly “rural” characteristics, we seek to make a contribution towards the “social construction of the rural space” and towards an understanding of the relation spheres and articulation between these spaces and the dynamics of urbanisation. This analysis was conducted within the context of a larger study that used several tools for gathering information (analysis of secondary data, questionnaires and interviews) in seeking to understand the principle recent transformations in the more peripheral and rural areas of the Algarve region. The Algarve is better known, both nationally and internationally, as an attractive tourist destination for those seeking sun and accessible beaches; however, it is also a very diverse region (with mountainous and rural landscapes), and one, moreover, little studied by the social sciences. Here we discuss and problematize social representations of the local space by the residents of two municipalities: São Brás de Alportel and Alcoutim. Based on the results of a study concluded in 2010, we discuss the responses to a survey of 678 residents in both municipalities (the questionnaire was given to a representative sample of residents according to gender and age [2001 Census]), in order to understand their views on the development of their municipality, about the area’s strong and weak points and about the main changes taking place in respect of the (re)composition of the local population. These two municipalities, which are very different despite their geographical proximity, were selected in order to allow an analysis of long-term structural changes; however, here we are particularly interested in discussing some of the exploratory analysis indicators associated with the respondents’ subjective perceptions. The representations by residents of both municipalities are various and contrasting, with asymmetries and diversities between them. This analysis leads us to a conclusion in respect of the limits on the use of conceptions that are naturalist, a priori and which are based on the reification of the spatial characteristics and social practices of social protagonists within rural spaces. It is necessary to devise alternative conceptual tools, ones that take into consideration the relational spaces promoting the dynamics of inter-relationship, diversity and of hybridism that must be incorporated into socio-territorial and multi-scale projects and policies (local base, connected to the national and the international)

Marshall University Department of Music Presents a Faculty Recital, featuring faculty from, The University of Brasília (UnB)

https://mds.marshall.edu/music_perf/1887/thumbnail.jp