Admission control schemes for TCP elastic traffic in class-based networks

En aquesta tesi proposem dos esquemes de xarxa amb control d'admissió per al trànsit elàstic TCP amb mecanismes senzills. Ambdós esquemes són capaços de proporcionar throughputs diferents i aïllament entre fluxos, on un "flux" es defineix com una seqüència de paquets relacionats dins d'una connexió TCP. Quant a l'arquitectura, ambdós fan servir classes de paquets amb diferents prioritats de descart, i un control d'admissió implícit, edge-to-edge i basat en mesures. En el primer esquema, les mesures són per flux, mentre que en el segon, les mesures són per agregat. El primer esquema aconsegueix un bon rendiment fent servir una modificació especial de les fonts TCP, mentre que el segon aconsegueix un bon rendiment amb fonts TCP estàndard. Ambdós esquemes han estat avaluats satisfactòriament a través de simulació en diferents topologies de xarxa i càrregues de trànsit.

Label space reduction in GMPLs and All-Optical Label Swapping networks

All-Optical Label Swapping (AOLS) es una tecnología clave para la implementación de nodos de conmutación completamente óptica de paquetes. Sin embargo, el costo de su desarrollo es proporcional al tamaño del espacio de etiquetas (label space). Debido a que los principios de funcionamiento de AOLS son casos particulares de los del MultiProtocol Label Switching (MPLS), esta tesis estudia métodos generales, aplicables a ambos, con el propósito de reducir el espacio de etiquetas tanto como sea posible. Modelos de programación lineal entera y heurísticas son propuestos para el caso en el que se permite apilar una etiqueta extra. Encontramos que cerca del 50% del espacio de etiquetas puede ser reducido, si se permite colocar una etiqueta extra en la pila. Además, particularmente para AOLS, encontramos que se puede reducir el espacio de etiquetas cerca al 25% si se duplica la capacidad de los enlaces y se permite re-encaminar el tráfico.

A reconfigurable neural environment on active networks

This paper proposes the deployment of a neural network computing environment on Active Networks. Active Networks are packet-switched computer networks in which packets can contain code fragments that are executed on the intermediate nodes. This feature allows the injection of small pieces of codes to deal with computer network problems directly into the network core, and the adoption of new computing techniques to solve networking problems. The goal of our project is the adoption of a distributed neural network for approaching tasks which are specific of the computer network environment. Dynamically reconfigurable neural networks are spread on an experimental wide area backbone of active nodes (ABone) to show the feasibility of the proposed approach.

Informal communication networks and the diffusion of innovations in UK construction projects: A research design

The UK industry has been criticised for being slow to adopt construction process innovations. Research shows that the idiosyncrasies of participants, their roles in the system and the contextual differences between sections of the industry make this a highly complex problem. There is considerable evidence that informal social networks play a key role in diffusion of innovations. The aim is to identify informal communication networks of project participants and the role these play in the diffusion of construction innovations. The characteristics of this network will be analysed in order to understand how they can be used to accelerate innovation diffusion within and between projects. Social Network Analysis is used to determine informal communication routes. Control and experiment case study projects are used within two different organizations. This allows informal communication routes concerning innovations to be mapped, whilst testing if the informal routes can facilitate diffusion. Analysis will focus upon understanding the combination of informal strong and weak ties, and how these impede or facilitate the diffusion of the innovation. Initial work suggests the presence of an informal communication network. Actors within this informal network, and the organization's management are unaware of its' existence and their informal roles within it. Thus, the network remains an untapped medium regarding innovation diffusion. It is proposed that successful innovation diffusion is dependent upon understanding informal strong and weak ties, at project, organization and industry level.

Building networks to work: an ethnographic study of informal routes into the UK construction industry and pathways for migrant up-skilling

The UK construction industry labour market is characterised by high levels of self-employment, sub-contracting, informality and flexibility. A corollary of this, and a sign of the increasing globalisation of construction, has been an increasing reliance on migrant labour, particularly that from the Eastern European Accession states. Yet, little is known about how their experiences within and outside of work shape their work in the construction sector. In this context better qualitative understandings of the social and communication networks through which migrant workers gain employment, create routes through the sector and develop their role/career are needed. We draw on two examples from a short-term ethnographic study of migrant construction worker employment experiences and practices in the town of Crewe in Cheshire, UK, to demonstrate how informal networks intersect with formal elements of the sector to facilitate both recruitment and up-skilling. Such research knowledge, we argue, offers new evidence of the importance of attending to migrant worker’s own experiences in the development of more transparent recruitment processes.

Inference From Aging Information

For many learning tasks the duration of the data collection can be greater than the time scale for changes of the underlying data distribution. The question we ask is how to include the information that data are aging. Ad hoc methods to achieve this include the use of validity windows that prevent the learning machine from making inferences based on old data. This introduces the problem of how to define the size of validity windows. In this brief, a new adaptive Bayesian inspired algorithm is presented for learning drifting concepts. It uses the analogy of validity windows in an adaptive Bayesian way to incorporate changes in the data distribution over time. We apply a theoretical approach based on information geometry to the classification problem and measure its performance in simulations. The uncertainty about the appropriate size of the memory windows is dealt with in a Bayesian manner by integrating over the distribution of the adaptive window size. Thus, the posterior distribution of the weights may develop algebraic tails. The learning algorithm results from tracking the mean and variance of the posterior distribution of the weights. It was found that the algebraic tails of this posterior distribution give the learning algorithm the ability to cope with an evolving environment by permitting the escape from local traps.

Characterizing topological and dynamical properties of complex networks without border effects

The properties of complex networks are highly Influenced by border effects frequently found as a consequence of the finite nature of real-world networks as well as network Sampling Therefore, it becomes critical to devise effective means for sound estimation of net work topological and dynamical properties will le avoiding these types of artifacts. In the current work, an algorithm for minimization of border effects is proposed and discussed, and its potential IS Illustrated with respect to two real-world networks. namely bone canals and air transportation (C) 2009 Elsevier B.V. All rights reserved.

Density-Profile Processes Describing Biological Signaling Networks: Almost Sure Convergence to Deterministic Trajectories

We introduce jump processes in R(k), called density-profile processes, to model biological signaling networks. Our modeling setup describes the macroscopic evolution of a finite-size spin-flip model with k types of spins with arbitrary number of internal states interacting through a non-reversible stochastic dynamics. We are mostly interested on the multi-dimensional empirical-magnetization vector in the thermodynamic limit, and prove that, within arbitrary finite time-intervals, its path converges almost surely to a deterministic trajectory determined by a first-order (non-linear) differential equation with explicit bounds on the distance between the stochastic and deterministic trajectories. As parameters of the spin-flip dynamics change, the associated dynamical system may go through bifurcations, associated to phase transitions in the statistical mechanical setting. We present a simple example of spin-flip stochastic model, associated to a synthetic biology model known as repressilator, which leads to a dynamical system with Hopf and pitchfork bifurcations. Depending on the parameter values, the magnetization random path can either converge to a unique stable fixed point, converge to one of a pair of stable fixed points, or asymptotically evolve close to a deterministic orbit in Rk. We also discuss a simple signaling pathway related to cancer research, called p53 module.

Is there wage premium to computer use in Sweden

This paper examines the wage premium to computer use in Sweden in the early 1990’s. I use simple regression model and interaction terms in my paper to examine the effect of computer use at work. Although the data is only one-year cross-section data, my results clearly show a wage premium to computer use in Sweden. There are also interesting findings in my paper by using Swedish data. From the results, I find wage premium to be related to intensity of computer use at work.

Independent Domain of Symmetric Encryption using Least SignificantBit : Computer Vision, Steganography and Cryptography Techniques

The rapid development of data transfer through internet made it easier to send the data accurate and faster to the destination. There are many transmission media to transfer the data to destination like e-mails; at the same time it is may be easier to modify and misuse the valuable information through hacking. So, in order to transfer the data securely to the destination without any modifications, there are many approaches like cryptography and steganography. This paper deals with the image steganography as well as with the different security issues, general overview of cryptography, steganography and digital watermarking approaches.  The problem of copyright violation of multimedia data has increased due to the enormous growth of computer networks that provides fast and error free transmission of any unauthorized duplicate and possibly manipulated copy of multimedia information. In order to be effective for copyright protection, digital watermark must be robust which are difficult to remove from the object in which they are embedded despite a variety of possible attacks. The message to be send safe and secure, we use watermarking. We use invisible watermarking to embed the message using LSB (Least Significant Bit) steganographic technique. The standard LSB technique embed the message in every pixel, but my contribution for this proposed watermarking, works with the hint for embedding the message only on the image edges alone. If the hacker knows that the system uses LSB technique also, it cannot decrypt correct message. To make my system robust and secure, we added cryptography algorithm as Vigenere square. Whereas the message is transmitted in cipher text and its added advantage to the proposed system. The standard Vigenere square algorithm works with either lower case or upper case. The proposed cryptography algorithm is Vigenere square with extension of numbers also. We can keep the crypto key with combination of characters and numbers. So by using these modifications and updating in this existing algorithm and combination of cryptography and steganography method we develop a secure and strong watermarking method. Performance of this watermarking scheme has been analyzed by evaluating the robustness of the algorithm with PSNR (Peak Signal to Noise Ratio) and MSE (Mean Square Error) against the quality of the image for large amount of data. While coming to see results of the proposed encryption, higher value of 89dB of PSNR with small value of MSE is 0.0017. Then it seems the proposed watermarking system is secure and robust for hiding secure information in any digital system, because this system collect the properties of both steganography and cryptography sciences.

Controle em tempo real de robôs através de redes IP

Com o intuito de utilizar uma rede com protocolo IP para a implementação de malhas fechadas de controle, este trabalho propõe-se a realizar um estudo da operação de um sistema de controle dinâmico distribuído, comparando-o com a operação de um sistema de controle local convencional. Em geral, a decisão de projetar uma arquitetura de controle distribuído é feita baseada na simplicidade, na redução dos custos e confiabilidade; portanto, um diferencial bastante importante é a utilização da rede IP. O objetivo de uma rede de controle não é transmitir dados digitais, mas dados analógicos amostrados. Assim, métricas usuais em redes de computadores, como quantidade de dados e taxa de transferências, tornam-se secundárias em uma rede de controle. São propostas técnicas para tratar os pacotes que sofrem atrasos e recuperar o desempenho do sistema de controle através da rede IP. A chave para este método é realizar a estimação do conteúdo dos pacotes que sofrem atrasos com base no modelo dinâmico do sistema, mantendo o sistema com um nível adequado de desempenho. O sistema considerado é o controle de um manipulador antropomórfico com dois braços e uma cabeça de visão estéreo totalizando 18 juntas. Os resultados obtidos mostram que se pode recuperar boa parte do desempenho do sistema.

Facebook3d

INTRODUCTION With the advent of Web 2.0, social networking websites like Facebook, MySpace and LinkedIn have become hugely popular. According to (Nilsen, 2009), social networking websites have global1 figures of almost 250 millions unique users among the top five2, with the time people spend on those networks increasing 63% between 2007 and 2008. Facebook alone saw a massive growth of 566% in number of minutes in the same period of time. Furthermore their appeal is clear, they enable users to easily form persistent networks of friends with whom they can interact and share content. Users then use those networks to keep in touch with their current friends and to reconnect with old friends. However, online social network services have rapidly evolved into highly complex systems which contain a large amount of personally salient information derived from large networks of friends. Since that information varies from simple links to music, photos and videos, users not only have to deal with the huge amount of data generated by them and their friends but also with the fact that it‟s composed of many different media forms. Users are presented with increasing challenges, especially as the number of friends on Facebook rises. An example of a problem is when a user performs a simple task like finding a specific friend in a group of 100 or more friends. In that case he would most likely have to go through several pages and make several clicks till he finds the one he is looking for. Another example is a user with more than 100 friends in which his friends make a status update or another action per day, resulting in 10 updates per hour to keep up. That is plausible, especially since the change in direction of Facebook to rival with Twitter, by encouraging users to update their status as they do on Twitter. As a result, to better present the web of information connected to a user the use of better visualizations is essential. The visualizations used nowadays on social networking sites haven‟t gone through major changes during their lifetimes. They have added more functionality and gave more tools to their users, but still the core of their visualization hasn‟t changed. The information is still presented in a flat way in lists/groups of text and images which can‟t show the extra connections pieces of information. Those extra connections can give new meaning and insights to the user, allowing him to more easily see if that content is important to him and the information related to it. However showing extra connections of information but still allowing the user to easily navigate through it and get the needed information with a quick glance is difficult. The use of color coding, clusters and shapes becomes then essential to attain that objective. But taking into consideration the advances in computer hardware in the last decade and the software platforms available today, there is the opportunity to take advantage of 3D. That opportunity comes in because we are at a phase were the hardware and the software available is ready for the use of 3D in the web. With the use of the extra dimension brought by 3D, visualizations can be constructed to show the content and its related information to the user at the same screen and in a clear way. Also it would allow a great deal of interactivity. Another opportunity to create better information‟s visualization presents itself in the form of the open APIs, specifically the ones made available by the social networking sites. Those APIs allow any developers to create their own applications or sites taking advantage of the huge amount of information there is on those networks. Specifically to this case, they open the door for the creation of new social network visualizations. Nevertheless, the third dimension is by itself not enough to create a better interface for a social networking website, there are some challenges to overcome. One of those challenges is to make the user understand what the system is doing during the interaction with the user. Even though that is important in 2D visualizations, it becomes essential in 3D due to the extra dimension. To overcome that challenge it‟s necessary the use of the principles of animations defined by the artists at Walt Disney Studios (Johnston, et al., 1995). By applying those principles in the development of the interface, the actions of the system in response to the user inputs became clear and understandable. Furthermore, a user study needs to be performed so the users‟ main goals and motivations, while navigating the social network, are revealed. Their goals and motivations are important in the construction of an interface that reflects the user expectations for the interface, but also helps in the development of appropriate metaphors. Those metaphors have an important role in the interface, because if correctly chosen they help the user understand the elements of the interface instead of making him memorize it. The last challenge is the use of 3D visualization on the web, since there have been several attempts to bring 3D into it, mainly with the various versions of VRML which were destined to failure due to the hardware limitations at the time. However, in the last couple of years there has been a movement to make the necessary tools to finally allow developers to use 3D in a useful way, using X3D or OpenGL but especially flash. This thesis argues that there is a need for a better social network visualization that shows all the dimensions of the information connected to the user and that allows him to move through it. But there are several characteristics the new visualization has to possess in order for it to present a real gain in usability to Facebook‟s users. The first quality is to have the friends at the core of its design, and the second to make use of the metaphor of circles of friends to separate users in groups taking into consideration the order of friendship. To achieve that several methods have to be used, from the use of 3D to get an extra dimension for presenting relevant information, to the use of direct manipulation to make the interface comprehensible, predictable and controllable. Moreover animation has to be use to make all the action on the screen perceptible to the user. Additionally, with the opportunity given by the 3D enabled hardware, the flash platform, through the use of the flash engine Papervision3D and the Facebook platform, all is in place to make the visualization possible. But even though it‟s all in place, there are challenges to overcome like making the system actions in 3D understandable to the user and creating correct metaphors that would allow the user to understand the information and options available to him. This thesis document is divided in six chapters, with Chapter 2 reviewing the literature relevant to the work described in this thesis. In Chapter 3 the design stage that resulted in the application presented in this thesis is described. In Chapter 4, the development stage, describing the architecture and the components that compose the application. In Chapter 5 the usability test process is explained and the results obtained through it are presented and analyzed. To finish, Chapter 6 presents the conclusions that were arrived in this thesis.

Criteria for analysis of the structure of electronic scientific journals

This paper is the result of the Masters dissertation studying the role and history of scientific communication, especially the changes that have occurred after the appearance of electronic communication and computer networks. This study showed that hypertext systems are increasingly being used in the scientific and academic world in the production of electronic journals; this makes it possible for the user to rapidly access information in their area. However, these systems need to be improved to help the user during search and access to information. Both printed journals migrating to electronic media, and the exclusively electronic journals should present the current quality indicators. The attempt was made to discover whether characteristics related to printed journals are being maintained in their electronic counterparts. For this, a prototype model was developed to analyze the structure of electronic scientific journals; it composes 14 criteria expressing aspects of quality for these journals. It includes elements of Website Information Architecture and those already in place in printed scientific journals in order to ensure that basic functions - archiving and dissemination - are maintained in electronic publishing. Each criterion consists of variables, which measure the maintenance of these functions both in the migrating printed journals and the exclusively electronic ones. This prototype model was used to analyze Ciência da Informação On-line and DataGramaZero - Revista de Ciência da Informação. Results indicate that this model is able to find out if the basic functions of archiving and dissemination are being maintained in electronic journals. Therefore, its implementation is justified in electronic journals. The model can help librarians, authors, and users of electronic journals to identify quality journals, and assist editors in developing their projects. The material from the study may be included in the preservice and inservice education of Information Science professionals and to support editors of scientific journals.

Uma arquitetura baseada em SCTP e SIP para suporte a aplicações VoIP móveis e a especificação formal do seu módulo de controle

New versions of SCTP protocol allow the implementation of handover procedures in the transport layer, as well as the supply of a partially reliable communication service. A communication architecture is proposed herein, integrating SCTP with the session initiation protocol, SIP, besides additional protocols. This architecture is intended to handle voice applications over IP networks with mobility requirements. User localization procedures are specified in the application layer as well, using SIP, as an alternative mean to the mechanisms used by traditional protocols, that support mobility in the network layer. The SDL formal specification language is used to specify the operation of a control module, which coordinates the operation of the system component protocols. This formal specification is intended to prevent ambiguities and inconsistencies in the definition of this module, assisting in the correct implementation of the elements of this architecture

Artificial neural networks: A novel approach to analysing the nutritional ecology of a blowfly species, Chrysomya megacephala

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)