Geometry of physical dispersion relations

To serve as a dispersion relation, a cotangent bundle function must satisfy three simple algebraic properties. These conditions are derived from the inescapable physical requirements to have predictive matter field dynamics and an observer-independent notion of positive energy. Possible modifications of the standard relativistic dispersion relation are thereby severely restricted. For instance, the dispersion relations associated with popular deformations of Maxwell theory by Gambini-Pullin or Myers-Pospelov are not admissible.Comment: revised version, new section on applications added, 46 pages, 9 figure

Are There Arbitrage Opportunities in Credit Derivatives Markets? A New Test and an Application to the Case of CDS and ASPs

This paper analyzes possible arbitrage opportunities in credit derivatives markets using selffinancing strategies combining Credit Default Swaps and Asset Swaps Packages. We present a new statistical arbitrage test based on the subsampling methodology which has lower Type I error than existing alternatives. Using four different databases covering the period from 2005 to 2009, long-run (cointegration) and statistical arbitrage analysis are performed. Before the subprime crisis, we find long-run arbitrage opportunities in 26% of the cases and statistical arbitrage opportunities in 24% of the cases. During the crisis, arbitrage opportunities decrease to 8% and 19%, respectively. Arbitrage opportunities are more frequent in the case of relatively low rated bonds and bonds with a high coupon rate

Mono-objective minimization of operation cost for a microgrid with renewable power generation, energy storage and electric vehicles

Cuando se habla de Microgrid se hace alusión a un sistema de potencia a pequeña escala, compuesto de elementos activos (generación renovable y tradicional, almacenamiento de energía y cargas controlables) operando entre ellos. Diferentes estudios han evaluado y modelado el costo de operación de varios elementos que integran la Microgrid, con el fin de identificar los puntos de operación correctos. En este estudio, se evaluó un modelo de Microgrid cuyo generador principal es diésel, posee un parque de generación fotovoltaica, dos turbinas eólicas, un banco de baterías y dos agregadores que gestionan vehículos eléctricos. El objetivo de esta investigación es plantear una ecuación capaz de describir el costo de operación de una Microgrid como conjunto, teniendo en cuenta los modelamientos del costo de operación de la energía fotovoltaica, la energía eólica, el almacenamiento de energía en bancos de baterías y vehículos eléctricos. Esta ecuación ademas busca obtener la mayor rentabilidad posible o, en otras palabras, disminuir al máximo el costo de operación de la Microgrid. Para esto, se usó el método metaheurístico DEEPSO (Differential Evolutionary Particle Swarm Optimization), que es muy conocido por sus aplicaciones en sistemas de potencia. A través de este método se puede determinar las condiciones de operación de los diferentes elementos que tiene la Microgrid, con el fin de disminuir al máximo el costo de su operación. Teniendo en cuenta todos los parámetros, se encontró y visualizó el comportamiento de cada uno de los elementos de la Microgrid en un horizonte de tiempo de 24 horas para obtener el costo mínimo de operación.The term Microgrid refers to a power system in a small scale, made of active elements operating between them, namely renewable and traditional generation, energy storage and controllable charges. Previous studies have evaluated and modelled the operation cost of many elements that make up the Microgrid, in order to identify the correct point of operation. In this study, the researchers evaluated a model of Microgrid with diesel as traditional generator, a park of photovoltaic generation, two wind generators, one battery bank and two aggregators that manage electric vehicles. The objective of this research is to propose an equation capable of describing the operation cost of a Microgrid as a set, taking into account the modelling of the operation cost of photovoltaic energy, wind energy, and energy storage in battery banks and electric vehicles. This equation also seeks to obtain the best possible cost efficiency, i.e., decreasing the operation cost of the Microgrid. For this purpose, the Metauristic method DEEPSO (Differential Evolutionary Particle Swarm Optimization) was used, recognized for its performance for applications in power systems. Through this method, and determinate the conditions of operation of the different elements in the Microgrid. Taking into account all the parameters, the behavior of each one of the elements of the Microgrid in a 24-hour lapse was found and visualized.Peer Reviewe

AUTOMATED NETWORK SECURITY WITH EXCEPTIONS USING SDN

Campus networks have recently experienced a proliferation of devices ranging from personal use devices (e.g. smartphones, laptops, tablets), to special-purpose network equipment (e.g. firewalls, network address translation boxes, network caches, load balancers, virtual private network servers, and authentication servers), as well as special-purpose systems (badge readers, IP phones, cameras, location trackers, etc.). To establish directives and regulations regarding the ways in which these heterogeneous systems are allowed to interact with each other and the network infrastructure, organizations typically appoint policy writing committees (PWCs) to create acceptable use policy (AUP) documents describing the rules and behavioral guidelines that all campus network interactions must abide by. While users are the audience for AUP documents produced by an organization\u27s PWC, network administrators are the responsible party enforcing the contents of such policies using low-level CLI instructions and configuration files that are typically difficult to understand and are almost impossible to show that they do, in fact, enforce the AUPs. In other words, mapping the contents of imprecise unstructured sentences into technical configurations is a challenging task that relies on the interpretation and expertise of the network operator carrying out the policy enforcement. Moreover, there are multiple places where policy enforcement can take place. For example, policies governing servers (e.g., web, mail, and file servers) are often encoded into the server\u27s configuration files. However, from a security perspective, conflating policy enforcement with server configuration is a dangerous practice because minor server misconfigurations could open up avenues for security exploits. On the other hand, policies that are enforced in the network tend to rarely change over time and are often based on one-size-fits-all policies that can severely limit the fast-paced dynamics of emerging research workflows found in campus networks. This dissertation addresses the above problems by leveraging recent advances in Software-Defined Networking (SDN) to support systems that enable novel in-network approaches developed to support an organization\u27s network security policies. Namely, we introduce PoLanCO, a human-readable yet technically-precise policy language that serves as a middle-ground between the imprecise statements found in AUPs and the technical low-level mechanisms used to implement them. Real-world examples show that PoLanCO is capable of implementing a wide range of policies found in campus networks. In addition, we also present the concept of Network Security Caps, an enforcement layer that separates server/device functionality from policy enforcement. A Network Security Cap intercepts packets coming from, and going to, servers and ensures policy compliance before allowing network devices to process packets using the traditional forwarding mechanisms. Lastly, we propose the on-demand security exceptions model to cope with the dynamics of emerging research workflows that are not suited for a one-size-fits-all security approach. In the proposed model, network users and providers establish trust relationships that can be used to temporarily bypass the policy compliance checks applied to general-purpose traffic -- typically by network appliances that perform Deep Packet Inspection, thereby creating network bottlenecks. We describe the components of a prototype exception system as well as experiments showing that through short-lived exceptions researchers can realize significant improvements for their special-purpose traffic

Are all Credit Default Swap databases equal?

The presence of different prices in different databases for the same securities can impair the comparability of research efforts and seriously damage the management decisions based upon such research. In this study we compare the six major sources of corporate Credit Default Swap prices: GFI, Fenics, Reuters EOD, CMA, Markit and JP Morgan, using the most liquid single name 5-year CDS of the components of the leading market indexes, iTraxx (European firms) and CDX (US firms) for the period from 2004 to 2010. We find systematic differences between the data sets implying that deviations from the common trend among prices in the different databases are not purely random but are explained by idiosyncratic factors as well as liquidity, global risk and other trading factors. The lower is the amount of transaction prices available the higher is the deviation among databases. Our results suggest that the CMA database quotes lead the price discovery process in comparison with the quotes provided by other databases. Several robustness tests confirm these results.Credit Default Swap prices, Databases, Liquidity

Mathematical Formulation and Numerical Validation of Uncertainty Costs for Controllable Loads

Este documento presenta el desarrollo de una nueva formulación matemática para definir, a través de enfoques probabilísticos, el costo que puede generarse si existiera un mercado eléctrico diversificado, con participación activa de la demanda. Para ello, se considera que la demanda eléctrica en un instante de tiempo sigue una distribución determinada de probabilidad y es controlable por el operador del sistema. El estudio muestra un desarrollo matemático del costo de incertidumbre de la demanda a partir del cálculo del costo esperado de suplir el valor de demanda más conveniente para el sistema de potencia. La validación de la fórmula analítica se realiza a través del método de Monte Carlo, que permitió comparar los costos de penalización asociados con la subestimación o sobreestimación de la demanda de energía eléctrica.This document presents an analysis and development of a new mathematical formulation to determine, through probabilistic approaches, the cost that can appear in a diversified electricity market with active load participation. In our approach, we consider that power demand follows a specific probability distribution and its control is performed through system's operator actions. The cost of uncertainty of demand is mathematically developed by calculating the expected cost of supplying the most convenient demand value for the power system. The validation of the analytical formula is done through the Monte Carlo method, that allowed us to compare the penalty costs in the case of underestimating or overestimating the demand for electrical energy.Peer Reviewe

Rediseño del modelo de negocio de la empresa IENERCOM LTDA.

Este informe realiza un análisis de Ienercom Ltda., empresa dedicada a la importación, comercialización y distribución de productos eléctricos, de comunicaciones y seguridad industrial -- El análisis incluye el entorno, bajo la óptica de las cinco fuerza de Michael Porter, y una observación de los resultados del negocio actual, mediante el uso de la Matriz de Boston Consulting Group, y una representación del modelo de negocio actual, bajo la metodología del lienzo de los nueve bloques de Alexander Osterwalder y Yves Pigneur (Canvas) -- Con esta información se hace una propuesta de rediseño del modelo de negocio usando métodos de ideación y análisis, tales como la matriz DAFO, el mapa de empatía y la lluvia de ideas, con el fin de que la compañía pueda identificar claramente sus fortalezas y debilidades y pueda orientar sus esfuerzos hacia la consolidación de una propuesta de valor diferenciadora, que le permita generar estrategias orientadas hacia el crecimiento sostenido, entender el comportamiento del mercado, la relación con el cliente, las verdaderas fuentes de sus ingresos, la estructura de costos y la configuración de los recursos que le permitan crecer y ser rentable y sostenible en el tiemp

Revisión del género Hermodice Kinberg, 1857 (Polychaeta: Amphinomidae)

The genus Hermodice Kinberg, 1857 was established with the species Aphrodita carunculata Pallas, 1766, based on the shape and development of the caruncle. Several species were later described within the genus; however, it is currently regarded as monotypical, with H. carunculata as a widespread species. An evaluation of available type and non-type specimens together with observations of living specimens has allowed the diagnostic features to be refined, and two new features have been included: the number of branchial filaments and the anal lobe. Consequently, in this study we have been able to confirm the differences between Hermodice and Pherecardia Horst, 1886. The type species, H. carunculata, has been redescribed, and H. nigrolineata Baird, 1870 has been re-established. Further, H. formosa (Quatrefages, 1866) has been transferred to Pherecardia, together with H. pennata Treadwell, 1906 and H. distincta Hoagland, 1920.El género Hermodice, Kinberg, 1857 se estableció con la especie Aphrodita carunculata Pallas, 1766, debido a la forma y desarrollo de la carúncula. Posteriormente, se describieron varias especies dentro del género. Sin embargo, actualmente se considera que el género es monotípico y que H. carunculata es una especie cosmopolita. La revisión de material tipo y especímenes adicionales, incluyendo ejemplares vivos, nos ha permitido redefinir las características diagnósticas e incorporar dos nuevos atributos: el número de filamentos branquiales y el lóbulo anal. Como consecuencia, ha sido posible confirmar las diferencias entre Hermodice y Pherecardia Horst, 1886. Así mismo, se redescribe la especie tipo H. carunculata y se reestablece H. nigrolineata Baird, 1870. Además, H. formosa (Quatrefages, 1866) se transfiere a Pherecardia, junto H. pennata Treadwell, 1906 y H. distincta Hoagland, 1920

Hybrid sintering – The beneficial combination of sintering principles

„Hybrid Sintering“ can be defined as a beneficial combination of different sintering principles, e.g. direct and indirect heating, uniaxial and gas pressure, high and low electrical fields (Figure 1). In the technological context this can be completed by debindering, decoupled pre-heating and cooling as well as rate controlled sintering optionally. Hybrid sintering systems enable the development and production of all new material solutions. Please click Additional Files below to see the full abstract

An empirical analysis of the dynamic dependences in the European Corporate credit markets : bonds vs. credit derivatives

In this paper we provide new evidence on the determinants of credit spread returns and their dynamic dependences in three European corporate credit markets: the Bond market (cash market), the Credit Default Swap (CDS) market (derivatives market), and the Asset Swap Package (ASP) market (with properties of both derivatives and cash markets). Using daily data from 2005 to 2009, we find that credit spread returns are primarily driven by innovations and to a lower extent by changes in the expected loss component, the risk premium component, the liquidity premium component and the inertial component whose relative importance changes over time. The intra-market dependence during the current crisis decreases for bonds and ASP innovations but increases slightly for CDS. ASP and bond innovations are closely related, suggesting that the cash component dominates the ASP innovations’ behavior. On the other hand CDS’s innovations are unrelated with both the bonds’ and the ASP’s innovations, suggesting that the derivatives element in the ASP contract (due to the implicit interest rate swap) is essentially unrelated with the innovations in the pure credit derivative contract (CDS)