Nuevo conocimiento - i2T

URI permanente para esta colecciónhttp://hdl.handle.net/10906/78226

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3-D structure of the Rio Grande Rift from 1-D constrained joint inversion of receiver functions and surface wave dispersion
(Elsevier, 2014-01-01) Romero, Rodrigo
The Southern terminus of the Rio Grande Rift region has been poorly defined in the geologic record, with few seismic studies that provide information on the deeper Rift structure. In consequence, important questions related to tectonic and lithospheric activity of the Rio Grande Rift remain unresolved. To address some of these geological questions, we collect and analyze seismic data from 147 EarthScope Transportable Array (USArray) and other seismic stations in the region, to develop a 3-D crust and upper mantle velocity model. We apply a constrained optimization approach for joint inversion of surface wave and receiver functions using seismic S wave velocities as a model parameter. In particular, we compute receiver functions stacks based on ray parameter, and invert them jointly with collected surface wave group velocity dispersion observations. The inversions estimate 1-D seismic S-wave velocity profiles to 300 km depth, which are then interpolated to a 3-D velocity model using a Bayesian kriging scheme. Our 3-D models show a thin lower velocity crust anomaly along the southeastern Rio Grande Rift, a persistent low velocity anomaly underneath the Colorado Plateau and Basin and Range province, and another one at depth beneath the Jemez lineament, and the southern RGR.
A Comparison of Taxonomies for Model Transformation Languages
(Universidad de los Andes, 2010-01-01) Tamura Morimitsu, Gabriel
Since the introduction of the MDE/MDA/MDD ideas for software systems development several years ago, a number of different (meta)modeling and model transformation languages have been proposed. Although the OMG's QVT standard specification has somewhat stabilized the number of new model transformation languages, it is likely that new ones will continue to appear, following different paradigms and approaches. However, the evolution towards the consolidation of models as a unifying, foundational and consistent concept for software-intensive system development, requires the realization of a set of ideal characteristics for the specification of model transformation languages. Several works have been proposed for defining characterization and classification schemes, and the set of these ideal characteristics.
A flexible mid-term frequency domain scheduler for resource allocation in HetNets based on the SINR requested by users
(Elsevier, 2015-03-01) Pachón de la Cruz, Alvaro
This article treats the resource allocation problem for the downlink of a multi-cell, multiservice Wireless Mobile Communications System (WMCS) with heterogeneous architecture deployed into an urban environment using Long Term Evolution (LTE) and Orthogonal Frequency Division Multiple Access (OFDMA) in its physical level. The optimization model aims to satisfy services to users by making an efficient use of the available resources, and a fair frequency block allocation, using the Signal to Interference-plus-Noise Ratio (SINR). It is a Mixed Integer Nonlinear Programming (MINLP) model whose solution is complex to obtain directly. The proposed solution algorithm decouples the solution space of the problem and uses an iterative and semi-distributed approach to implement a frequency-domain scheduler in the medium term that uses a global vision of the system to allocate resources trying to obtain the SINR required for all users (the proposed goal). Since it is not always possible to achieve it, we take advantage of the elasticity of some of the services offered and incorporate a slack variable to solve it. The approach allows selecting the frequency allocation strategy, the exploration focus of the search space and the system administrator's vision. The results obtained show that the implementation that uses a coordinated frequency allocation obtains better results in the amount of users with full satisfaction and in the use of power when compared to implementations using other frequency allocation strategies. In scenarios with heterogeneous architecture, the combined effect of picocells and coordinated frequency allocation improves the value for the defined performance metrics.
A guide to best practices for the transition from ipv4 to ipv6
(Universidad Icesi., 2015-10-01) Roa G., Mario Alejandro
Este artículo presenta una propuesta de guía de buenas prácticas para asistir a las áreas de Tecnología de la In-formación [TI] en los procesos de planeación e implementación de la transición de sus servicios de infraestructura y tecnología hacia el protocolo IPv6. Se realizó un análisis de referencias para la identificación del problema y un exhaustivo estudio del estado del arte, particularmente se puntualizó en el estado actual del avance en la migración hacia IPv6 y su implementación a nivel global, en el estado actual de la tecnología en las regiones donde este protocolo es un factor clave y en el proceso que esas regiones han desarrollado para la materialización de la transición. Tam-bién se presentan los resultados del análisis de los métodos lleva-dos a cabo por los gobiernos para materializar dicha transición, la identificación de cómo los procesos del modelo de buenas prácticas para TI de ITIL® pueden soportar esta transición y los mecanismos existentes de transición tecnológica de IPv4 a IPv6 bajo dos escenarios: con y sin coexistencia de ambos protocolos.
A Model to Guide Dynamic Adaptation Planning in Self-Adaptive Systems
(Elsevier, 2016-03-14) Arboleda Jiménez, Hugo Fernando
Self-adaptive enterprise applications have the ability to continuously reconfigure themselves according to changes in their execution contexts or user requirements. The infrastructure managing such systems is based on IBM's MAPE-K reference model: a Monitor and an Analyzer to sense and interpret context data, a Planner and an Executor to create and apply structural adaptation plans, and a Knowledge manager to share relevant information. In this paper we present a formal model, built on the principles of constraint satisfaction, to address dynamic adaptation planning for self-adaptive enterprise applications. We formalize, modify and extend the approach presented in [H. Arboleda, J. F. Díaz, V. Vargas, and J.-C. Royer, "Automated reasoning for derivation of modeldriven spls," in SPLC'10 MAPLE'10, 2010, pp. 181-188] for working with self-adaptation infrastructures in order to provide automated reasoning on the dynamic creation of structural adaptation plans. We use a running example to demonstrate the applicability of such model, even in situations where complex interactions arise between context elements and the target self-adaptive enterprise application.
A multihop-authenticated proxy mobile IP scheme for asymmetric VANETs
(IEEE Transactions on Vehicular Technology, 2013-01-01) Cespedes Umaña, Sandra Lorena
Vehicular communications networks are envisioned for the access to drive-thru Internet and IP-based infotainment applications. These services are supported by roadside access routers (ARs) that connect vehicular ad hoc networks (VANETs) to external IP networks. However, VANETs suffer from asymmetric links due to variable transmission ranges caused by mobility, obstacles, and dissimilar transmission power, which make it difficult to maintain the bidirectional connections and to provide the IP mobility required by most IP applications. Moreover, vehicular mobility results in short-lived connections to the AR, affecting the availability of IP services in VANETs. In this paper, we study the secure and timely handover of IP services in an asymmetric VANET and propose a multihop-authenticated Proxy Mobile IP (MA-PMIP) scheme. MA-PMIP provides an enhanced IP mobility scheme over infrastructure-to-vehicle-to-vehicle (I2V2V) communications that uses location and road traffic information. The MA-PMIP also reacts, depending on the bidirectionality of links, to improve availability of IP services. Moreover, our scheme ensures that the handover signaling is authenticated when V2V paths are employed to reach the infrastructure so that possible attacks are mitigated without affecting the performance of the ongoing sessions. Both analysis and extensive simulations in OMNeT++ are conducted, and the results demonstrate that the MA-PMIP improves service availability and provides secure seamless access to IP applications in asymmetric VANETs. © 2013 IEEE.
A novel correlation adaptive receiver structure for high speed transmissions in ultra wide band systems with realistic channel estimation
(Institute of Electrical and Electronics Engineers, 2009-10-01) Navarro Cadavid, Andrés
Impulse radio ultra wide band (UWB) communications require robust receivers; typically Rake receivers are required to capture a large number of resolvable paths, (even hundred of paths), so large number of correlators are needed; otherwise, adaptive receivers use complex filters and channel estimation algorithms. Therefore, traditional Impulse Radio receivers demand non-practical implementation structures. In this paper we propose a novel correlation-adaptive receiver structure with low complexity for indoor high speed ultra wide band systems. This novel structure combines correlation characteristics from rake receivers with recursive filters from adaptive receivers. The receiver includes a low complexity recursive channel estimation filter capable of estimating hundreds of channel impulse responses, and a single filter-correlation filter used for coherent bit demodulation. Furthermore, we derive by simulations the bit error rate for high density multipath environments for several Impulse Radio modulations like TH-PPM, DS-BPSK and TH-BPSK and we compare the performance of the proposed structure with typical Rake receivers. © 2009 IEEE.
A Survey of Attack Mechanisms on Infrastructure-Mode 802.11 Wireless Networks and Their Detection - Encyclopedia of Information Science and Technology, Third Edition [Book]
(IGI Global, 2014-01-01) Madrid Molina, Juan Manuel
The 802.11 wireless network revolution has not come without trouble. Since their creation, wireless networks have been plagued with security problems, derived from poor initial design of 802.11 security mechanisms, accelerated deployment and adoption of the technology, and lack of user education.
Agrupamiento mediante Q-análisis
(Universidad Icesi, 2010-11-25T22:17:31Z) Múnera Salazar, Luis Eduardo
This article presents a novel clustering algorithm, based upon topology concepts and Q-analysis. The algorithm allows to create a structural clustering, which does not depend on the knowledge of similarity measures, distances, etc. The clustering is directed in a natural fashion by the internal topology of the network/ graph. Such topology becomes evident by applying Q-analysis, by means of the structure vector, which shows the network’s internal Q-connectivity.
Ajuste estadístico de modelos de propagación de señal usando medidas de la ciudad de Cali
(Universidad de Santiago de Cali,, 2012-03-20) Ardila, Carlos Andredy
La dificultad de estimar con exactitud la influencia de los obstáculos, los edificios y el terreno en la pérdida de trayectoria de la señal hace que los modelos de propagación, generalmente utilizados para la planificación de redes inalámbricas externas, en entornos urbanos incluyan algunos elementos empíricos. Por lo tanto, la ecuación final generalmente contiene constantes y coeficientes para los diferentes términos, que se obtienen principalmente a partir del análisis estadístico de mediciones recolectadas durante actividades de drive test en grandes áreas de la ciudad. Desafortunadamente, estos resultados son realmente válidos únicamente para las áreas de la ciudad en las que se obtuvieron y, en el mejor de los casos, para áreas o ciudades similares. Sin embargo, si el nivel de similitud no es suficiente, es necesario realizar ajustes, un proceso que resulta en la formulación de nuevas constantes y nuevos coeficientes. El propósito de este artículo es discutir algunos de los hallazgos obtenidos durante el proceso de ajuste estadístico al escenario de la ciudad de Cali, de los modelos Okumura-Hata, Stanford University Interim (SUI) y Walfisch-Bertoni, usando mediciones.
Algoritmos de planificación en redes de paquetes
(Universidad Icesi, 2010-03-24T23:27:25Z) Cuéllar Quiñonez, Juan Carlos
This article presents the mechanisms and processes required in order for a router to provide QoS in packet networks and it presents the state of the art in the subject of scheduling algorithms use in this kind of networks.
Alineamiento de múltiples secuencias de aminoácidos usando algoritmos genéticos
(Universidad Icesi, 2006-10-11) Solanilla, Luis Felipe
This article describes a genetic algorithm and its implementation that it allows the alignment of multiple sequences of amino acids by means of relocations that simulate the gaps insertion (holes) and actions of recombination to obtain higher scores in the alignment. Such scores are obtained by means of the method of the sum of even, in which there are considered all the possible combinations of amino acids in each column of the alignment and they are qualified being based on the punctuations of the matrix BLOSUM62.
Análisis basado en parámetros QoS para el servicio VoIP sobre wireless en un campus universitario
(Universidad de Manizales, 2014-07-31) Olave, Alexander
VoIP is one of the services that has been developing over under this type of wireless platforms and today has begun to implement as an alternative to the PSTN (Public Switched Telephone Network). The interest in VoIP is its cost-benefit ratio, and that organizations can use the same platform for their data network to transmit voice. Therefore it is important that the organization is clear that to ensure the smooth operation of the VoIP service, ie provide QoS, you must perform the measurement of parameters that affect the quality of service such as: delay, jitter, bandwidth, packet loss. In this paper we analyze and validate the QoS parameters needed to ensure the smooth operation of VoIP over wireless network on the Icesi University campus. We performed a series of tests in different scenarios to show that not only factors such as delay and jitter influencing the quality of service, but also the client signal strength received from of the AP (Access Point). Keywords : Voice over IP, Quality of service, Packet Loss, Delay, Delay variation, signal intensity.
Análisis de capacidad en sistemas CDMA y WCDMA, usando herramientas de planificación basadas en GIS y dinámica poliédrica
(Universitat Politècnica de València, 2003-10-17) Navarro Cadavid, Andrés; Cardona Marcet, Narcís
En este momento están entrando en operación los primeros sistemas UMTS en Europa, y están operando en varios países del mundo sistemas CDMA-2000 1xRTT, y aunque existen muchos trabajos publicados sobre la capacidad de estos sistemas, prácticamente todo lo existente se basa en el comportamiento de sistemas ideales que consideran celdas hexagonales o circulares y propagación basada en exponente inverso de la distancia y poco es lo que hay sobre el comportamiento real de dichos sistemas en entornos reales.

Sobre el exponente de pérdidas de propagación, es bien conocido que este afecta la capacidad de los sistemas CDMA; sin embargo hasta ahora no se ha considerado el efecto de los modelos de propagación que tienen en cuenta la difracción y otros fenómenos más cercanos a la realidad, y por lo tanto no se ha considerado el efecto del entorno urbano y el terreno sobre la capacidad real de los sistemas basados en CDMA.
Análisis de configuraciones en el núcleo de una red NGN para garantizar QoS
(Universidad Icesi, 2010-11-25T22:04:37Z) Cuéllar Quiñonez, Juan Carlos
The quality of service has become a vital issue for service providers, but their analysis has been oriented to the configuration in the interconnectivity devices mainly. The article presents the data analysis from a series of simulations for a NGN with MPLS cores, which together are configured QoS mechanisms with specific configurations within the core network. Additionally we present the data analysis from experimental setup laboratory similar characteristics to the simulated pattern.
Análisis descriptivo del proceso de implementación del nivel 2 del modelo CMMI en una empresa regional de desarrollo de software
(Universidad Icesi, 2008-12-18) Picazzo M., Catherine; Villegas Machado, Norha Milena; Tamura Morimitsu, Gabriel
CMMI (Capability Maturity Model Integration) is basically a continuous- improvement inspired model to classify software development organizations according to a fivelevel maturity and capability scale. The classification in a given level is based on the dominance that an organization shows evidence to have over the areas of that level, which in turn reflects the degree of maturity of the organization and of the processes that it follows to develop software. This article presents a preliminary descriptive analysis of a level 2 implementation process of the CMMI model in a Colombian software development company, making an overall presentation of how it was brought into practice the theory of the model in the processes of the company, to be compliant with the conditions, goals and practices defined in the level 2 process areas of the model. The article also describes the problems which arose in the execution of the project, as well as how they were solved. As preliminary results are presented some of the indicators defined by the company for the software processes, and the software tools that were acquired or developed for the support of the implementation of the process areas. Finally, some conclusions and recommendations which can be found.
Análisis espectral de parámetros fisiológicos para detección de emociones
(Universidad Icesi, 2012-01-01) Valderrama Cuadros, Camilo Ernesto; Ulloa Villegas, Gonzalo Vicente
This paper show a literature review in the field of emotions detection. Show the strength of aplications of Brain Computer Interfaces (BCI) and what the functionality of it is. Explain how work with neourosignal and how to extract information using Discrete Wavelet Transform to recognize some characteristics that are present in the signal. Also explain the methods which are used for classification the signals. The purpose of the review is established a basis for the development of a project which want define the behavior of brain signal's when a person sees a commercial advertisement.
Analysis of Quality of Service Parameters Using a Simulation Tool
(Universidad Católica de Pereira, 2011-01-01) Cuéllar Quiñonez, Juan Carlos
Simulation tools are a key element for data network design and implementation, since they allow for network behavior to be analyzed under defined parameters. This article analyzes the behavior of the IPTD and IPDV parameters on an MPLS core network, using several queuing algorithms, in order to discover which algorithm has the best performance under a defined set of constraints, according to ITU Y.1541 recommendations. The article presents the methodology employed for setting up the simulation experiments, as well as a survey of simulation tools Las herramientas de simulación son un elemento clave para el diseño e implementación de redes de datos, ya que permiten que el comportamiento de la red sea analizado bajo parámetros definidos. En este artículo se analiza el comportamiento de los parámetros IPTD e IPDV en una red central MPLS, utilizando algunos algoritmos de colas, con el fin de descubrir el algoritmo que tiene el mejor rendimiento en un conjunto definido de restricciones, de acuerdo con las recomendaciones UITY 1541. El artículo presenta la metodología empleada para la creación de los experimentos de simulación, así como un estudio de herramientas de simulación.
Aplicación de la metáfora de la colonia de hormigas en la administración de direcciones en redes móviles ad hoc
(Universidad Icesi, 2009-08-18T21:00:06Z) Veiga, Manuel Fernández; Pachón de la Cruz, Alvaro
Address management is a critical process in a network, because any node wishing to make part of the network must first obtain an address. Address management in MANETs poses particular challenges, due to their operation conditions, their dynamic topology and the unique events that take place inside them. This article presents an approach for solving the address management problem in this environment, using the self-organization and emergency principles governing the behavior of social insect colonies, particularly ant colonies. The article presents results that evaluate the proposal’s validity and efficiency through several scenarios. Three fundamental aspects were evaluated: Model functionality, efficiency and impact on user applications. The obtained results show the proposed model is able to identify, manage and solve all the events related to address management in a MANET, in an efficient manner.
Aplicación de modelos markovianos en sistemas de comunicación móvil celular GSM900*
(Universidad Icesi, 2006-07-28) Mantilla F., Javier D.; Monclou S., Alex A.; Navarro Cadavid, Andrés; Camerano F., Rafael
El presente artículo muestra en forma clara que el canal de acceso RACH del sistema GSM (Global System for Mobile) se puede modelar como una cadena de Markov discreta. La teoríade cadenas de Markov se emplea para encontrar el comportamiento de estado estable en el modelo de seis estados planteado por la norma GSM utilizando un lenguaje de alto nivelcomo Matlab, que se emplea para simular el modelo planteado teóricamente. Los resultados de las simulaciones muestran el comportamiento estadístico del proceso de selección yreselección de celda del terminal móvil en el sistema GSM.

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