Compact modes in quasi one dimensional coupled magnetic oscillators

In this work we study analytically and numerically the spectrum and localization properties of three quasi-one-dimensional (ribbons) split-ring resonator arrays which possess magnetic flatbands, namely, the stub, Lieb and kagome lattices, and how their spectra is affected by the presence of perturbations that break the delicate geometrical interference needed for a magnetic flatband to exist. We find that the Stub and Lieb ribbons are stable against the three types of perturbations considered here, while the kagome ribbon is, in general, unstable. When losses are incorporated, all flatbands remain dispersionless but become complex, with the kagome ribbon exhibiting the highest loss rate.Comment: 11 pages, 15 figure

Agroindustria y Sistemas de Innovación en Nicaragua

El artículo explora el desarrollo de la agro industrialización rural, y discursa sobre los distintos enfoques teóricos aplicados en Nicaragua para luego plantear que se requiere un enfoque sistémico a la par de los enfoque de cadenas en sus distintas variantes. Se propone el enfoque de sistemas nacionales de innovación como un enfoque comprensivo que conlleve a la formulación de políticas de innovación sistémicas. Nicaragua y en general los países en desarrollo están experimentando encadenamientos de producción y abastecimiento y revisión de los sistemas regulatorio. Hay una demanda de alimentos y la revalorización de la agricultura, está empujando a la aparición de nuevos compradores en las zonas rurales compitiendo por diversos productos, sin mencionar el crecimiento de nuevos mercados de biocombustibles, el pago de servicios ambientales para la reducción de las emisiones de gases efecto invernadero y la preservación de la biodiversidad. Esta nueva ronda económica/mercantil genera nuevas amenazas y presiones sobre los recursos naturales, y los agentes económicos buscan nuevas formas de explotación. Nicaragua no puede seguir compitiendo sobre la base de ventajas comparativas centradas en recursos naturales abundantes. Esta estrategia agotara dichos factores y recurso

Black Pugilism: The First Act In Twentieth Century America

When teaching about the twenty-first century in the United States of America, educators delve deeply into how the Jim Crow Era was but a new manifestation of a slave-era philosophy. As W.E.B. Du Bois states in his 1903 book The Souls of Black Folk, “the problem of the Twentieth Century is the problem of the color-line.” Inspiring pro-Jim Crow government officials and citizens to impose economic and political segregation on black citizens that, on paper, are “separate but equal” when infringing on their civil and human rights deliberately. Limiting the black individual to the status of second-class citizenship where they are not slaves nor citizens, numerous historical figures emerged in the communal effort to end the color line’s systematic influence. However, among the accounts of brave activists fighting for equal rights between the races, those who defied the color line with more self-centered ambitions exist. Black Pugilism studies, analyzes, and illustrates how the realm of professional boxing became a fascinating focal point of racial tension. Two manly descendants of enslaved peoples use the worldly popular craft to express themselves self-absorbedly and unapologetically or an appealing image of their community to their naysayers and oppressors. Those legendary men are “The Galveston Giant” Jack Johnson and “The Black Panther” Harry Wills. Readers will learn how and why professional boxing was a contentious arena between black equality activists against economically and politically advantaged pro-Jim Crow whites over the “reality” of white supremacy. A “reality” so faulty that when even a single boxing match can effectively prove it as mere fantasy, white men nationwide pay rapt attention in hopes of validation for their racial and manly validation expectations. As W.E.B. Du Bois expresses in his 1910 magazine article “The Souls of White Folk,” “pity for a people imprisoned and enthralled, hampered, and made miserable for such a cause, for such a phantasy!” So too, enters the politics of manliness. Precisely because, in early Jim Crow eyes, masculinity is an exclusively white trait. An underrepresented and virtually untaught history in the fight for equality in spaces of more than one color. Examining the encompassing racial and gender politics of the multi-decade story will reveal the ease of disrupting but the difficulty of ending the entrenched belief of inherent greatness by skin color. As seen when the sons of freedpeople are not seen and treated as men but as a lowly race of males of far lesser mental and physical makeup than any white man. Then, after revealing no correlation between masculinity and race, a new predominant narrative emerges of the black man as beastly and immoral. An unforgiving history of the frustrating and fatal gradual progression to one day become a justly and fairly treated demographic of American citizens

matlab scripts for MMC Pareto optimization

Calculate the Pareto frontier with minimum arm energy ripple and conduction loss of an MMC when the second and fourth harmonic of the circulating current is used as free parameters. ParetoMMC attempts to solve min F(X, lambda), X where F(X, lambda) = E_ripple(X)*lambda + P_loss*(1 - lambda). X denotes the amplitudes and phases of the second and fourth harmonic of the circulating current. lambda is the weighting scalar in the range 0 <= lamda <= 1. The MMC dc side is connected to a dc voltage source, while the ac side is a symmetric three phase voltage with isolated star point. A third harmonic in the common mode voltage is assumed.:ParetoMMC.m F_eval.m LICENSE.GNU_AGPLv

Reactive evolutionary path planning for autonomous surface vehicles in lake environments.

Autonomous Surface Vehicles (ASVs) have found a lot of promising applications in aquatic environments, i.e., sea, lakes, rivers, etc. They can be used for applications of paramount importance, such as environmental monitoring of water resources, and for bathymetry to study the characteristics of the basing of a lake/sea or for surveillance in patrol missions, among others. These vehicles can be built with smaller dimensions when compared to regular ships since they do not need an on-board crew for operation. However, they do require at least a telemetry control as well as certain intelligence for making decisions and responding to changing scenarios. Water resources are very important in Paraguay since they provide fresh water for its inhabitants and they are crucial for the main economic activities such as agriculture and cattle raising. Furthermore, they are natural borders with the surrounding countries, and consequently the main transportation route for importing/exporting products. In fact, Paraguay is the third country in the world with the largest fleet of barges after USA and China. Thus, maintaining and monitoring the environmental conditions of these resources is key in the development of the country. This work is focused on the maintenance and monitoring of the greatest lake of the country called Ypacarai Lake. In recent years, the quality of its water has been seriously degraded due to the pollution caused by the low control of the dumping of waste thrown into the Lake. Since it is also a national icon, the government of Paraguay has put a lot of effort in recovering water quality of the Lake. As a result, it is monitored periodically but using manual procedures. Therefore, the primary objective of this work is to develop these monitoring tasks autonomously by means of an ASV with a suitable path planning strategy. Path planning is an active research area in robotics. A particular case is the Coverage Path Planning (CPP) problem, where an algorithm should find a path that achieves the best coverage of the target region to be monitored. This work mainly studies the global CPP, which returns a suitable path considering the initial conditions of the environment where the vehicle moves. The first contribution of this thesis is the modeling of the CPP using Hamiltonian Circuits (HCs) and Eulerian Circuits (ECs). Therefore, a graph adapted to the Ypacarai Lake is created by using a network of wireless beacons located at the shore of the lake, so that they can be used as data exchange points between a control center and the ASV, and also as waypoints. Regarding the proposed modeling, HCs and ECs are paths that begin and end at the same point. Therefore, the ASV travels across a given graph that is defined by a set of wireless beacons. The main difference between HC and EC is that a HC is a tour that visits each vertex only once while EC visits each edge only once. Finding optimal HCs or ECs that minimize the total distance traveled by the ASV are very complex problems known as NP-complete. To solve such problems, a meta-heuristic algorithm can be a suitable approach since they provide quasi-optimal solutions in a reasonable time. In this work, a GA (Genetic Algorithm) approach is proposed and tested. First, an evaluation of the performance of the algorithm with different values of its hyper-parameters has been carried out. Second, the proposed approach has been compared to other approaches such as randomized and greedy algorithms. Third, a thorough comparison between the performance of HC and EC based approaches is presented. The simulation results show that EC-based approach outperforms the HC-based approach almost 2% which in terms of the Lake size is about 1.4 km2 or 140 ha (hectares). Therefore, it has been demonstrated that the modeling of the problem as an Eulerian graph provides better results. Furthermore, it has been investigated the relationship between the number of beacons to be visited and the distance traveled by the ASV in the EC-based approach. Findings indicate that there is a quasi-lineal relationship between the number of beacons and the distance traveled. The second contribution of this work is the development of an on-line learning strategy using the same model but considering dynamic contamination events in the Lake. Dynamic events mean the appearance and evolution of an algae bloom, which is a strong indicator of the degradation of the lake. The strategy is divided into two-phases, the initial exploration phase to discover the presence of the algae bloom and next the intensification phase to focus on the region where the contamination event is detected. This intensification effect is achieved by modifying the beacon-based graph, reducing the number of vertices and selecting those that are closer to the region of interest. The simulation results reveal that the proposed strategy detects two events and monitors them, keeping a high level of coverage while minimizing the distance traveled by the ASV. The proposed scheme is a reactive path planning that adapts to the environmental conditions. This scheme makes decisions in an autonomous way and it switches from the exploratory phase to the intensification phase depending on the external conditions, leading to a variable granularity in the monitoring task. Therefore, there is a balance between coverage and the energy consumed by the ASV. The main benefits obtained from the second contribution includes a better monitoring in the quality of water and control of waste dumping, and the possibility to predict the appearance of algae-bloom from the collected environmental data