k-colored kernels

We study $k$-colored kernels in $m$-colored digraphs. An $m$-colored digraph $D$ has $k$-colored kernel if there exists a subset $K$ of its vertices such that (i) from every vertex $v\notin K$ there exists an at most $k$-colored directed path from $v$ to a vertex of $K$ and (ii) for every $u,v\in K$ there does not exist an at most $k$-colored directed path between them. In this paper, we prove that for every integer $k\geq 2$ there exists a $(k+1)$-colored digraph $D$ without $k$-colored kernel and if every directed cycle of an $m$-colored digraph is monochromatic, then it has a $k$-colored kernel for every positive integer $k.$ We obtain the following results for some generalizations of tournaments: (i) $m$-colored quasi-transitive and 3-quasi-transitive digraphs have a $k$% -colored kernel for every $k\geq 3$ and $k\geq 4,$ respectively (we conjecture that every $m$-colored $l$-quasi-transitive digraph has a $k$% -colored kernel for every $k\geq l+1)$, and (ii) $m$-colored locally in-tournament (out-tournament, respectively) digraphs have a $k$-colored kernel provided that every arc belongs to a directed cycle and every directed cycle is at most $k$-colored

Analytical Approach to Model the Fade Depth and the Fade Margin in UWB Channels

In this letter, the variations of the ultra-wideband (UWB) channel power as a function of the channel bandwidth are investigated. An analytical approach to characterize the fade depth and the fade margin due to small-scale fading in indoor environments is proposed. The approach is based on the IEEE 802.15.4a ultra-wideband channel model and the assumption that the channel power can be modeled by a Gamma distribution. This analytical approach is checked by comparison with results derived through Monte Carlo simulations. The results show that the fade depth and the fade margin are closely related to the channel bandwidth. This analytical approach can be used to design and implement UWB communications systems.Rubio Arjona, L.; Reig, J.; Rubio Arjona, L. (2010). Analytical Approach to Model the Fade Depth and the Fade Margin in UWB Channels. IEEE Transactions on Vehicular Technology. 59(9):4214-4221. doi:10.1109/TVT.2010.2070815S4214422159

Frequency UWB Channel

Ultra wideband (UWB) transmission systems are characterized with either a fractional bandwidth of more that 20%, or a large absolute bandwidth (>500 MHz) in the 3.1 GHz to 10.6 GHz band, and for a very low power spectral density (-41.25 dBm/MHz, equivalent to 75nW/MHz), which allows to share the spectrum with other narrowband and wideband systems without causing interference (FCC, 2002), this spectral allocation has initiated an extremely productive activity for industry and academia. Wireless communications experts now consider UWB as available spectrum to be utilized with a variety of techniques and not specifically related to the generation and detection of short RF pulses as in the past (Batra, 2004). For this reason, UWB systems are emerging as the best solution for high speed short range indoor wireless communication and sensor networks, with applications in home networking, high-quality multimedia content delivery, radars systems of high accuracy, etc. UWB has many attractive properties, including low interference to and from other wireless systems, easier wall and floor penetration, and inherent security due to its Low Probability Interception/Detection (LPI/D). Two of the most promising applications of UWB are High Data Rate Wireless Personal Area Network (HDR-WPAN), and Sensor Networks, where the good ranging and geo-location capabilities of UWB are particularly useful and of interest for military applications (Molisch, 2005)

Extracción de pectinas a partir de los subproductos del beneficio del cacao

En este estudio se evaluó la posibilidad de obtener pectinas a partir de los subproductos del proceso del beneficio del cacao. Los experimentos se llevaron a cabo en el laboratorio de desarrollo de productos del departamento de ingeniería de procesos de la Universidad EAFIT.53 p.Contenido parcial: Cacao -- Pectina -- Materiales y equipos -- Procedimiento del desarrollo experimental -- Caracterización y comparación de las pectinas obtenidas con la pectina comercial -- Costos de materia prima

Estudio de factibilidad para acuerdos de compra de energía de proyectos solares fotovoltaicos de menos de 20 kWp en Antioquia

Actualmente, en Colombia no existe un modelo de negocio que haga viable los acuerdos de compra de energía con sistemas solares fotovoltaicos de menos de 20 kWp; en consecuencia, hay una gran porción del mercado, de gran interés para desarrolladores solares y EPCistas, desatendida -- En este estudio se evaluará la factibilidad de la estrategia de empaquetamiento de sistemas solares fotovoltaicos, con el fin de determinar si esta propuesta permite a los inversionistas acceder a los beneficios tributarios que ofrece la ley y, de esta forma, hacer viable la inversión en este tipo de proyectos de pequeña escala -- Para realizar el estudio se empleará la metodología de preparación de estudios de viabilidad industrial de la Organización de las Naciones Unidas para el Desarrollo Industrial (ONUDI) -- En un principio, se analizará la viabilidad del sector, posteriormente se determinará la demanda estimada para los sistemas solares fotovoltaicos de pequeña escala en Antioquia, luego se analizará la viabilidad técnica y legal del empaquetamiento de estos sistemas y, finalmente, se realizará una evaluación financiera, con el objetivo de concluir si es factible o no esta estrategia para el desarrollo de acuerdos de compra de energía de sistemas solares fotovoltaicos de menos de 20 kWpCurrently in Colombia, there is no record of business models that make power purchase agreements of solar photovoltaic systems of less than 20kWp viable -- Consequently, there is a great proportion of the market left uncovered that is equally appealing for solar developers and EPC’s -- This study will assess the feasibility of the packaging strategy for photovoltaic solar systems aiming at determining whether this proposal allows investors to have access to tributary benefits and, hence, make investment in small-scale projects viable -- In order to conduct this study, we are going to use the UNIDO methodology for the preparation of studies of industrial feasibility -- In the first stage, we are going to analyze the feasibility of the market and will subsequently determine the estimated demand for small- scale photovoltaic solar systems in Antioquia -- In a later stage, we will assess the technical and legal feasibility of packaging these systems and, finally, we will engage in a financial evaluation to conclude whether this strategy is feasible for the development of power purchase agreements of photovoltaic solar systems of less than 20kW