Enhanced arc-flow formulations to minimize weighted completion time on identical parallel machines

We consider the problem of scheduling a set of jobs on a set of identical parallel machines, with the aim of minimizing the total weighted completion time. The problem has been solved in the literature with a number of mathematical formulations, some of which require the implementation of tailored branch-and-price methods. In our work, we solve the problem instead by means of new arc-flow formulations, by first representing it on a capacitated network and then invoking a mixed integer linear model with a pseudo-polynomial number of variables and constraints. According to our computational tests, existing formulations from the literature can solve to proven optimality benchmark instances with up to 100 jobs, whereas our most performing arc-flow formulation solves all instances with up to 400 jobs and provides very low gap for larger instances with up to 1000 jobs

Analysis of the European Directive 98/83/EC: Paradigm of the Justification and Establishment of Parametric Values. The Specific Case of Pesticides

La protección de la salud a la vez que se garantiza el acceso al agua potable a toda la población es uno de los objetivos principales a nivel mundial. En ese sentido, la Unión Europea, a través de la Directiva 98/83/CE, establece los parámetros y valores paramétricos máximos admisibles para garantizar la calidad del agua destinada al consumo humano. El objetivo de este artículo es dar una visión global de los valores establecidos en la Directiva Europea en comparación con otros países y organizaciones, como la Organización Mundial de la Salud, en base a su justificación toxicológica, haciendo especial mención al caso concreto de los plaguicidas, en los que existe una gran diferencia entre los valores paramétricos fijados. Asimismo, se presenta una comparativa con los valores establecidos por la Directiva 91/414/CEE para límites máximos de residuos de plaguicidas en alimentos, destacando la importancia de aunar criterios.The health protection while ensuring the access to safe drinking water to the entire population is one of the main objectives all over the world. In this regard, the European Union, through Directive 98/83/EC, sets the parameters and maximum allowable parametric values to ensure the quality of water intended for human consumption. The aim of this paper is to give an overview of the values established in the European Directive in comparison with other countries and organizations, such as the World Health Organization, based on toxicological justification, doing special mention to the case of pesticides, in which there is great difference between the parametric values set. It also presents a comparison with the values fixed by the Directive 91/414/EEC concerning maximum residue limits of pesticides in food, highlighting the importance of joining criteria

A ideia de cidade, em Álvaro Siza.

O estudo em causa procura compreender a perspectiva que Álvaro Siza construiu sobre a cidade ao longo da sua experiência e produção arquitectónica. Na verdade, na sua obra, parece existir a consciência de que cada projecto faz parte do processo evolutivo da cidade. As marcas impressas no lugar são testemunho dessa evolução e da história das cidades. Assim, a arquitectura de Siza, respeitando as memórias do passado e seus fragmentos, procura restabelecer uma unidade equilibrada. Já nos seus projectos dos anos 70, nomeadamente em S. Vítor, o arquitecto manipula a modernidade da linguagem, reconhecendo, simultaneamente, a complexidade e o carácter fragmentário da cidade e da arquitectura. Efectivamente, o projecto de renovação da zona de S. Vítor (1974-77), informado pelas experiências anteriores de habitação colectiva, implica diferentes formas de relação com a cidade. A partir do estudo das diversas intervenções contempladas por este projecto, é possível observar o modo como Siza desenha o espaço a favor de uma relação positiva e multifacetada com a cidade. O conhecimento desenvolvido através da análise deste projecto cruza-se com a compreensão de uma metodologia projectual que Siza expõe em diversos depoimentos. Após a experiência de S. Vítor, Siza continua o seu percurso arquitectónico, amadurecendo a ideia de cidade aqui desenvolvida. Por um lado, o plano para a Malagueira, em Évora, e o plano para Porto Exterior e Areia Preta, em Macau, correspondem à urbanização de amplas zonas contíguas à cidade e exploram a relação das formas urbanas propostas com os caracteres do lugar. Já os projectos para para Kreuzberg, em Berlim, Schilderswijk e Doedijnstraat, em Haia, e Chiado, em Lisboa, dizem respeito, sobretudo, à intervenção sobre troços delimitados da cidade existente, mas sobre condições e aspirações muito variadas. A diversidade destes projectos e obras será fundamental para procurar os caracteres essenciais e imutáveis que caracterizam a arquitectura e a ideia de cidade de Siza. Subentendida no percurso do arquitecto, encontramos a presença de diversas contaminações e referências. Na relação com o lugar e na dialética tradição/modernidade, Fernando Távora e Alvar Aalto são personagens incontornáveis. Por outro lado, na crítica ao movimento moderno, particularmente à Carta de Atenas, Aldo Rossi propõe uma nova abordagem da arquitectura e da cidade assente na sua condição fragmentária e na circularidade do tempo, que influi significativamente na obra de Siza.The present study seeks to understand Álvaro Siza's perspective of city throughout his experience and architectural production. Indeed, in all his work, he seems aware that every project is part of the city's evolutionary process. The unique features of each place are evidence of the city's history and evolution. Thus, the architecture of Siza, respecting memories from the past and its fragments, seeks to restore a balanced unity. During the seventies, he already manipulates a modern language while recognizing the complex and fragmentary nature of city and architecture, particularly in S. Vítor. In fact, the project of renovation of S. Vítor´s area (1974-77), informed by his previous experiences of collective housing, involves several forms of relations with the city. Through the study of the various interventions covered by this project, it is possible to see how Siza designs the space on behalf of a positive and versatile relation with the city. The knowledge developed through the analysis of this project crosses itself with the understanding of his methodology, which Siza exposes in his statements. After S. Vítor, Siza continues his architectural experience, maturing his idea of city. On one hand, the plan for Malagueira, in Évora, and the plan for Porto Exterior and Areia Preta, in Macau, correspond to the urbanization of large areas contiguous to the city and explore the relation between the proposed urban shapes and the place's character. On the other hand, the projects for Kreuzberg, in Berlin, Schilderswijk and Doedijnstraat, in Haia, and Chiado, at Lisbon, concern mainly the intervention on defined sections of the existing city, but on very different conditions and aspirations. The diversity of these projects is fundamental in order to find the essential and immutable features of the arquitecture of Álvaro Siza and his idea of city. The presence of various references is implicit in the work of the architect. Fernando Távora and Alvar Aalto are fundamental characters regarding to the relation with the place and the dialectic tradition/modernity. Moreover, Aldo Rossi is an important character by having a critical position in relation to the modern movement, particularly the Charte d'Athenes. He proposes a new approach to the architecture and city based on their fragmentary condition and the circularity of time, which significantly affects Siza's work

Kinetic theory of a confined quasi-one-dimensional gas of hard disks

A dilute gas of hard disks confined between two straight parallel lines is considered. The distance between the two boundaries is between one and two particle diameters, so that the system is quasi-one-dimensional. A Boltzmann-like kinetic equation, that takes into account the limitation in the possible scattering angles, is derived. It is shown that the equation verifies an -theorem implying a monotonic approach to equilibrium. The implications of this result are discussed, and the equilibrium properties are derived. Closed equations describing how the kinetic energy is transferred between the degrees of freedom parallel and perpendicular to the boundaries are derived for states that are homogeneous along the direction of the boundaries. The theoretical predictions agree with results obtained by means of Molecular Dynamics simulations.Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía US-1380729 (partially financed by FEDER 2014-2020 funds

Effectiveness of Virtual Reality on Functional Performance after Spinal Cord Injury: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

A spinal cord injury (SCI) usually results in a significant limitation in the functional outcomes, implying a challenge to the performance of activities of daily living. The main aim of this study is to analyze the effectiveness of virtual reality to improve functional performance in patients with SCI. The search was performed between October and December 2019 in Cumulative Index to Nursing and Allied Health Literature (CINAHL), Medline, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database (PEDro), PubMed, Scopus, Web of Science, and Embase. The methodological quality of the studies was evaluated through the PEDro scale, and the risk of bias was evaluated with the Cochrane collaboration's tool. Seven articles were included in this systematic review, and five of them in the meta-analysis. Statistical analysis showed favorable results for functional performance in control group performing conventional therapy, measured by the functional independence measure (standardized mean difference (SMD)= -0.70; 95% confidence interval: -1.25 to -0.15). Results were inconclusive for other outcomes. Most studies have not shown beneficial effects on functional performance compared with conventional physical therapy. The results obtained showed that virtual reality may not be more effective than conventional physical therapy in improving functional performance in patients with SCI

Cambios estructurales durante las reformas de mercado: evidencias para Argentina y Brasil entre 1980 y 2008

La investigación observa el cambio estructural y su eficiencia en Argentina y Brasil entre 1980 y 2008, como resultado de la interacción del cambio tecnológico y las innovaciones con las complementariedades. Para ello, tras realizar las pruebas de raíces unitarias y de cointegración, se ha estimado una ecuación general sobre el cambio estructural y tres parciales sobre sus componentes. Según los resultados no hubo crecimiento basado en el cambio estructural en Argentina. En Brasil hubo una respuesta positiva pero débil, lo que apunta a la necesidad de mejorar la coordinación de su sistema de innovación y la articulación de su estructura productiva

Extracción de características en un esquema de recuperación de imágenes

En este trabajo se presentan dos módulos fundamentales dentro del esquema diseñado de recuperación de imágenes de una base de datos a partir del color y la forma de los objetos presentes en las escenas. De una parte, se diseña un nuevo método para la detección de fronteras en imágenes en color. Se muestra una aproximación al espacio perceptual (H,S,I) (un espacio de Escala de Cromaticidad Uniforme (UCS)) sobre el que se describen tanto sus propiedades como una métrica para trabajar en el mismo. De otra, se lleva a cabo un proceso de simplificación de la información tendente a formar una estructura gráfica en la que los píxeles de la imagen se agrupan entorno a regiones de color similar. Para ello se diseña un mecanismo de crecimiento de regiones en base a la información de gradiente proporcionada por el módulo detector de fronteras, así como un módulo de división de las mismas.Eje: Procesamiento distribuido y paralelo. Tratamiento de señalesRed de Universidades con Carreras en Informática (RedUNCI

Extracción de características en un esquema de recuperación de imágenes

En este trabajo se presentan dos módulos fundamentales dentro del esquema diseñado de recuperación de imágenes de una base de datos a partir del color y la forma de los objetos presentes en las escenas. De una parte, se diseña un nuevo método para la detección de fronteras en imágenes en color. Se muestra una aproximación al espacio perceptual (H,S,I) (un espacio de Escala de Cromaticidad Uniforme (UCS)) sobre el que se describen tanto sus propiedades como una métrica para trabajar en el mismo. De otra, se lleva a cabo un proceso de simplificación de la información tendente a formar una estructura gráfica en la que los píxeles de la imagen se agrupan entorno a regiones de color similar. Para ello se diseña un mecanismo de crecimiento de regiones en base a la información de gradiente proporcionada por el módulo detector de fronteras, así como un módulo de división de las mismas.Eje: Procesamiento distribuido y paralelo. Tratamiento de señalesRed de Universidades con Carreras en Informática (RedUNCI

Virtual Reality Systems for Upper Limb Motor Function Recovery in Patients With Spinal Cord Injury: Systematic Review and Meta-Analysis

Background: Patients with spinal cord injury (SCI) usually present with different motor impairments, including a deterioration of upper limb motor function (ULMF), that limit their performance of activities of daily living and reduce their quality of life. Virtual reality (VR) is being used in neurological rehabilitation for the assessment and treatment of the physical impairments of this condition. Objective: A systematic review and meta-analysis was conducted to evaluate the effectiveness of VR on ULMF in patients with SCI compared with conventional physical therapy. Methods: The search was performed from October to December 2019 in Embase, Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, Medline, Physiotherapy Evidence Database (PEDro), PubMed, and Cochrane Central Register of Controlled Trials. The inclusion criteria of selected studies were as follows: (1) comprised adults with SCI, (2) included an intervention with VR, (3) compared VR intervention with conventional physical therapy, (4) reported outcomes related to ULMF, and (5) was a controlled clinical trial. The Cochrane Collaboration's tool was used to evaluate the risk of bias. The RevMan 5.3 statistical software was used to obtain the meta-analysis according to the standardized mean difference (SMD) and 95% CIs. Results: Six articles were included in this systematic review. Four of them contributed information to the meta-analysis. A total of 105 subjects were analyzed. All of the studies used semi-immersive or nonimmersive VR systems. The statistical analysis showed nonsignificant results for the Nine-Hole Peg Test (SMD -0.93, 95% CI -1.95 to 0.09), muscle balance test (SMD -0.27, 95% CI -0.82 to 0.27), Motricity Index (SMD 0.16, 95% CI -0.37 to 0.68), Jebsen-Taylor Hand Function Test (JTHFT) subtests (writing, SMD -0.10, 95% CI -4.01 to 3.82; simulated page turning, SMD -0.99, 95% CI -2.01 to 0.02; simulated feeding, SMD -0.64, 95% CI -1.61 to 0.32; stacking checkers, SMD 0.99, 95% CI -0.02 to 2.00; picking up large light objects, SMD -0.42, 95% CI -1.37 to 0.54; and picking up large heavy objects, SMD 0.52, 95% CI -0.44 to 1.49), range of motion of shoulder abduction/adduction (SMD -0.23, 95% CI -1.48 to 1.03), shoulder flexion/extension (SMD 0.56, 95% CI -1.24 to 2.36), elbow flexion (SMD -0.36, 95% CI -1.14 to 0.42), elbow extension (SMD -0.21, 95% CI -0.99 to 0.57), wrist extension (SMD 1.44, 95% CI -2.19 to 5.06), and elbow supination (SMD -0.18, 95% CI -1.80 to 1.44). Favorable results were found for the JTHFT subtest picking up small common objects (SMD -1.33, 95% CI -2.42 to -0.24). Conclusions: The current evidence for VR interventions to improve ULMF in patients with SCI is limited. Future studies employing immersive systems to identify the key aspects that increase the clinical impact of VR interventions are needed, as well as research to prove the benefits of the use of VR in the rehabilitation of patients with SCI in the clinical setting