The "No Justice in the Universe" phenomenon: why honesty of effort may not be rewarded in tournaments

In 2000 Allen Schwenk, using a well-known mathematical model of matchplay tournaments in which the probability of one player beating another in a single match is fixed for each pair of players, showed that the classical single-elimination, seeded format can be "unfair" in the sense that situations can arise where an indisputibly better (and thus higher seeded) player may have a smaller probability of winning the tournament than a worse one. This in turn implies that, if the players are able to influence their seeding in some preliminary competition, situations can arise where it is in a player's interest to behave "dishonestly", by deliberately trying to lose a match. This motivated us to ask whether it is possible for a tournament to be both honest, meaning that it is impossible for a situation to arise where a rational player throws a match, and "symmetric" - meaning basically that the rules treat everyone the same - yet unfair, in the sense that an objectively better player has a smaller probability of winning than a worse one. After rigorously defining our terms, our main result is that such tournaments exist and we construct explicit examples for any number n >= 3 of players. For n=3, we show (Theorem 3.6) that the collection of win-probability vectors for such tournaments form a 5-vertex convex polygon in R^3, minus some boundary points. We conjecture a similar result for any n >= 4 and prove some partial results towards it.Comment: 26 pages, 2 figure

The Hegselmann-Krause dynamics on the circle converge

We consider the Hegselmann-Krause dynamics on a one-dimensional torus and provide the first proof of convergence of this system. The proof requires only fairly minor modifications of existing methods for proving convergence in Euclidean space.Comment: 9 pages, 2 figures. Version 2: A small error in the proof of Theorem 1.1 is corrected and an acknowledgement added. Bibliography update

Herramienta de apoyo a la docencia en sistemas operativos

El proyecto fin de carrera de herramienta de apoyo a la docencia en Sistemas Operativos quiere ayudar al alumno a entender el funcionamiento de un planificador a corto plazo. Lo hace mediante una representación gráfica de procesos que ocupan o el procesador o distintas unidades de entrada/salida mientras transcurre el tiempo. El tiempo está dividido en ciclos de reloj de un procesador, a lo que a continuación se referirá como unidades de tiempo. Los procesos están definidos por su nombre, la instante de entrada que entran al sistema, su prioridad y la secuencia de unidades de tiempo en el procesador y unidades de entrada/salida que necesitan para terminar su trabajo. El alumno puede configurar el sistema a su gusto en cuanto al número y comportamiento de las unidades de entrada/salida. Puede definir que una unidad solo permita acceso exclusivo a los procesos, es decir que solo un proceso puede ocuparla simultáneamente, o que permita el acceso múltiple a sus recursos. El alumno puede construir un planificador a corto plazo propio, integrarlo en el sistema y ver cómo se comporta. Se debe usar la interfaz Java proporcionada para su construcción. La aplicación muestra datos estadísticos como por ejemplo la eficiencia del sistema (el tiempo activo de la CPU dividido por el tiempo total de la simulación), tiempos de espera de los procesos, etc. Se calcula después de cada unidad de tiempo para que el alumno pueda ver el momento exacto donde la simulación tomó un giro inesperado. La aplicación está compuesta por un motor de simulación que contiene toda la lógica y un conjunto de clases que forman la interfaz gráfica que se presenta al usuario. Estos dos componentes pueden ser reemplazados siempre y cuando se mantenga la definición de sus conectores igual. La aplicación la he hecho de manejo muy simple e interfaz fácil de comprender para que el alumno pueda dedicar todo su tiempo a probar distintas configuraciones y situaciones y así entender mejor la asignatura. ABSTRACT. The project is called “Tool to Support Teaching of the Subject Operating Systems” and is an application that aims to help students understand on a deeper level the inner workings of how an operating system handles multiple processes in need of CPU time by the means of a short-term planning algorithm. It does so with a graphical representation of the processes that occupy the CPU and different input/output devices as time passes by. Time is divided in CPU cycles, from now on referred to as time units. The processes are defined by their name, the moment they enter the system, their priority and the sequence of time units they need to finish their job. The student can configure the system by changing the number and behavior of the input/output devices. He or she can define whether a device should only allow exclusive access, i.e. only one process can occupy it at any given time, or if it should allow multiple processes to access its resources. The student can build a planning algorithm of his or her own and easily integrate it into the system to see how it behaves. The provided Java interface and the programming language Java should be used to build it. The application shows statistical data, e.g. the efficiency of the system (active CPU time divided by total simulation time) and time spent by the processes waiting in queues. The data are calculated after passing each time unit in order for the student to see the exact moment where the simulation took an unexpected turn. The application is comprised of a simulation motor, which handles all the logic, and a set of classes, which is the graphical user interface. These two parts can be replaced individually if the definition of the connecting interfaces stays the same. I have made the application to be very easy to use and with an easy to understand user interface so the student can spend all of his or her time trying out different configurations and scenarios in order to understand the subject better

Extinctions of aculeate pollinators in Britain and the role of large-scale agricultural changes

Pollinators are fundamental to maintaining both biodiversity and agricultural productivity, but habitat destruction, loss of flower resources, and increased use of pesticides are causing declines in their abundance and diversity. Using historical records we assessed the rate of extinction of bee and flower-visiting wasp species in Britain, from the mid 19th century to the present. The most rapid phase of extinction appears to be related to changes in agricultural policy and practice beginning in the 1920s, before the agricultural intensification prompted by the Second World War, often cited as the most important driver of biodiversity loss in Britain. Slowing of the extinction rate from the 1960s onwards may be due to prior loss of the most sensitive species and/or effective conservation programs

Hydrological Behavior of Grasslands of the Sandhills of Nebraska: Water and Energy Balance Assessment from Measurements, Treatments and Modeling

Understanding energy and water balance processes in the Sandhills is crucial to assess the land-atmosphere feedback effects. The Sandhills located in western Nebraska covers a vast grassland ecosystem with limited variability in vegetation and soil. However, the combined effect of topography, land cover and micrometeorology by subjecting the land surface to various disturbances and treatments is rarely studied. The NOAH Land Surface Model was used to estimate net radiation, latent, sensible and ground heat fluxes as well as water balance components for two growing seasons between 2005 and 2006 in various plots at the Grasslands Destabilization Experimental site where these plots were subjected to four different treatments and located at two topographical locations namely high and low positions. The simulated results of net radiation and ground heat fluxes correlated well with measurements. While the amount of precipitation received was between 900 and 1000 mm for both seasons, on a daily and sub-daily time scale, the partitioning of net radiation into latent, sensible and ground heat fluxes showed high variability across the plots, primarily driven by vegetation and soil moisture. Total evapotranspiration and soil moisture averages suggested the influence of vegetation and timing of precipitation also in controlling various land surface processes in the Sandhills. This study provides a framework for using the LSM to quantify the feedback effects and emphasizes the importance of microtopography and land treatments in the model environment

Att starta eget - en väg till frigörelse? En kvalitativ studie om mikroföretagare i Sydafrika

The aim of our study is to explore the empowerment process among micro-business owners in Kayamandi, a black township of Stellenbosch in South Africa. What are the positive and negative implications for the empowerment process? Another aim is to find out the role of local and international support in this process. The theoretical framework of this study revolves around the concepts of gender, power and empowerment. Our methods are qualitative interviews and observations. We have interviewed five micro-business owners; three women and two men. The conclusions of our study are that having one’s own business can be empowering for the individual person in many levels, especially for the women. Most important is the feeling of pride and independence to be your own employer, and also to be able to work with your passion on a daily basis. Our informants started their businesses on their own, without the help of the local organisation Greater Stellenbosch Development Trust (GSDT), but the organisation facilitates the business by providing housing and offering a micro-business course. The informants have an awareness about the inequalities, which remain vast in post-apartheid South Africa. They generally look positively upon the future for Kayamandi and South Africa as a whole. They feel that it is important to work together with the other people of the township and they want to help other people, not just run their own business. In that sense, the informants have a broad perspective upon their own situation as well as the society. Empowerment on the structural level is yet to be achieved. The main negative implications for the empowerment process are the lack of resources as well as the lack of influence within the organisation. Many of the informants have a critical view upon the organisation. GSDT is not a grass-root organisation and the informants sometimes complain about the lack of influence. International aid can be an important source of strength for the organisation and business owners, for example by taking the initiative to start a Support Group Committee where the business owners can make their voices heard. The micro-business owners have many individual skills and resources, and they are constantly struggling to overcome the obstacles that are surrounding them. We feel that there is a great deal of opportunities and with the right kind of support there can be a change for the people in Kayamandi. An important point here is not to see people as victims, but as agents who have lots of potential to develop themselves and their community

Sulla scia di Icaro

La progettazione di velivoli dal minimo attrito tiene impegnati i ricercatori del DICAT di Genova che lavorano al progetto europeo FLUBIO. La realizzazione del "perfetto automa volante" trae ispirazione dalla natura e in particolare dal volo dell'airone, un ottimo modello per velivoli con ali ricoperte da piume che battono al vent