OpenRaiser/Intern-Atlas huggingface dataset:
On challenges and opportunities of designing integrated IT platforms for supporting knowledge works in organizations
Venue: arXiv cs.DL 2009
Year: 2009

Designing and implementing comprehensive IT-based support environments for KM in organizations is fraught with many problems. Solving them requires intimate knowledge about the information usage in knowledge works and the scopes of technology intervention. In this paper, the Task-oriented Organizational Knowledge Management or TOKM, a design theory for building integrated IT platforms for supporting organizational KM, is proposed. TOKM brings together two apparently mutually exclusive practices of building KM systems, the task-based approach and the generic or universalistic approach. In developing the design, the information requirements of knowledge workers in light of an information usage model of knowledge works is studied. Then the model is extended to study possibilities of more advanced IT support and formulate them in form of a set of meta-requirements. Following the IS design theory paradigm, a set of artifacts are hypothesized to meet the requirements. Finally, a design method, as a possible approach of building an IT-based integrated platform, the Knowledge Work Support Platform (KWSP) to realize the artifacts in order to meet the requirements, is outlined. The KWSP is a powerful platform for building and maintaining a number of task-type specific Knowledge Work Support Systems (KWSS) on a common sharable platform. Each KWSS, for the task-type supported by it, can be easily designed to provide extensive and sophisticated support to individual as well as group of knowledge workers in performing their respective knowledge work instances
Communication scientifique : Pour le meilleur et pour le PEER
Venue: arXiv cs.DL 2009
Year: 2009

This paper provides an overview (in French) of the European PEER project, focusing on its origins, the actual objectives and the technical deployment.
Expectation Maximization as Message Passing - Part I: Principles and Gaussian Messages
Venue: arXiv cs.IT 2009
Year: 2009

It is shown how expectation maximization (EM) may be viewed as a message passing algorithm in factor graphs. In particular, a general EM message computation rule is identified. As a factor graph tool, EM may be used to break cycles in a factor graph, and tractable messages may in some cases be obtained where the sum-product messages are unwieldy. As an exemplary application, the paper considers linear Gaussian state space models. Unknown coefficients in such models give rise to multipliers in the corresponding factor graph. A main attraction of EM in such cases is that it results in purely Gaussian message passing algorithms. These Gaussian EM messages are tabulated for several (scalar, vector, matrix) multipliers that frequently appear in applications.
Bloggers Behavior and Emergent Communities in Blog Space
Venue: arXiv cs.CY 2009
Year: 2009

Interactions between users in cyberspace may lead to phenomena different from those observed in common social networks. Here we analyse large data sets about users and Blogs which they write and comment, mapped onto a bipartite graph. In such enlarged Blog space we trace user activity over time, which results in robust temporal patterns of user--Blog behavior and the emergence of communities. With the spectral methods applied to the projection on weighted user network we detect clusters of users related to their common interests and habits. Our results suggest that different mechanisms may play the role in the case of very popular Blogs. Our analysis makes a suitable basis for theoretical modeling of the evolution of cyber communities and for practical study of the data, in particular for an efficient search of interesting Blog clusters and further retrieval of their contents by text analysis.
FFT-based Network Coding For Peer-To-Peer Content Delivery
Venue: arXiv cs.IT 2009
Year: 2009

In this paper, we propose a structured peer-to-peer (P2P) distribution scheme based on Fast Fourier Transform (FFT) graphs. We build a peer-to-peer network that reproduces the FFT graph initially designed for hardware FFT codecs. This topology allows content delivery with a maximum diversity level for a minimum global complexity. The resulting FFTbased network is a structured architecture with an adapted network coding that brings flexibility upon content distribution and robustness upon the dynamic nature of the network. This structure can achieve optimal capacity in terms of content recovery while solving the problem of last remaining blocks, even for large networks.
An Immune Inspired Network Intrusion Detection System Utilising Correlation Context
Venue: arXiv cs.AI 2009
Year: 2009

Network Intrusion Detection Systems (NIDS) are computer systems which monitor a network with the aim of discerning malicious from benign activity on that network. While a wide range of approaches have met varying levels of success, most IDSs rely on having access to a database of known attack signatures which are written by security experts. Nowadays, in order to solve problems with false positive alerts, correlation algorithms are used to add additional structure to sequences of IDS alerts. However, such techniques are of no help in discovering novel attacks or variations of known attacks, something the human immune system (HIS) is capable of doing in its own specialised domain. This paper presents a novel immune algorithm for application to the IDS problem. The goal is to discover packets containing novel variations of attacks covered by an existing signature base.
Degrees of Freedom of Multi-Source Relay Networks
Venue: arXiv cs.IT 2009
Year: 2009

We study a multi-source Gaussian relay network consisting of $K$ source--destination pairs having $K$ unicast sessions. We assume $M$ layers of relays between the sources and the destinations. We find achievable degrees of freedom of the network. Our schemes are based on interference alignment at the transmitters and symbol extension and opportunistic interference cancellation at the relays. For $K$-$L$-$K$ networks, i.e., 2-hop network with $L$ relays, we show $\min\{K,K/2+L/(2(K-1))\}$ degrees of freedom are achievable. For $K$-hop networks with $K$ relays in each layer, we show the full $K$ degrees of freedom are achievable provided that $K$ is even and the channel distribution satisfies a certain symmetry.
Algorithms for Image Analysis and Combination of Pattern Classifiers with Application to Medical Diagnosis
Venue: arXiv cs.CV 2009
Year: 2009

Medical Informatics and the application of modern signal processing in the assistance of the diagnostic process in medical imaging is one of the more recent and active research areas today. This thesis addresses a variety of issues related to the general problem of medical image analysis, specifically in mammography, and presents a series of algorithms and design approaches for all the intermediate levels of a modern system for computer-aided diagnosis (CAD). The diagnostic problem is analyzed with a systematic approach, first defining the imaging characteristics and features that are relevant to probable pathology in mammo-grams. Next, these features are quantified and fused into new, integrated radio-logical systems that exhibit embedded digital signal processing, in order to improve the final result and minimize the radiological dose for the patient. In a higher level, special algorithms are designed for detecting and encoding these clinically interest-ing imaging features, in order to be used as input to advanced pattern classifiers and machine learning models. Finally, these approaches are extended in multi-classifier models under the scope of Game Theory and optimum collective deci-sion, in order to produce efficient solutions for combining classifiers with minimum computational costs for advanced diagnostic systems. The material covered in this thesis is related to a total of 18 published papers, 6 in scientific journals and 12 in international conferences.
Stealth-MITM DoS Attacks on Secure Channels
Venue: arXiv cs.CR 2009
Year: 2009

We define stealth Man-in-the-Middle adversaries, and analyse their ability to launch denial and degradation of service (DoS) attacks on secure channels. We show realistic attacks, disrupting TCP communication over secure VPNs using IPsec. We present: First amplifying DoS attack on IPsec, when deployed without anti-replay window. First amplifying attack on IPsec, when deployed with a `small' anti-replay window, and analysis of `sufficient' window size. First amplifying attack on IPsec, when deployed with `sufficient' window size. This attack (as the previous) is realistic: attacker needs only to duplicate and speed-up few packets. We also suggest a solution designed to prevent the presented attacks, and to provide secure channel immune to degradation and other DoS attacks. Our solution involves changes (only) to the two gateway machines running IPsec. In addition to their practical importance, our results also raise the challenge of formally defining secure channels immune to DoS and degradation attacks, and providing provably-secure implementations.
Comparison of Algorithms for Checking Emptiness on Buechi Automata
Venue: arXiv cs.LO 2009
Year: 2009

We re-investigate the problem of LTL model-checking for finite-state systems. Typical solutions, like in Spin, work on the fly, reducing the problem to Buechi emptiness. This can be done in linear time, and a variety of algorithms with this property exist. Nonetheless, subtle design decisions can make a great difference to their actual performance in practice, especially when used on-the-fly. We compare a number of algorithms experimentally on a large benchmark suite, measure their actual run-time performance, and propose improvements. Compared with the algorithm implemented in Spin, our best algorithm is faster by about 33 % on average. We therefore recommend that, for on-the-fly explicit-state model checking, nested DFS should be replaced by better solutions.
Distributed Universally Optimal Strategies for Interference Channels with Partial Message Passing
Venue: arXiv cs.IT 2009
Year: 2009

In distributed wireless networks, nodes often do not know the topology (network size, connectivity and the channel gains) of the network. Thus, they have to compute their transmission and reception parameters in a distributed fashion. In this paper, we consider that each of the transmitter know the channel gains of all the links that are at-most two-hop distant from it and the receiver knows the channel gains of all the links that are three-hop distant from it in a deterministic interference channel. With this limited information, we find a condition on the network connectivity for which there exist a distributed strategy that can be chosen by the users with partial information about the network state, which achieves the same sum capacity as that achievable by the centralized server that knows all the channel gains. Specifically, distributed decisions are sum-rate optimal only if each connected component is in a one-to-many configuration or a fully-connected configuration. In all other cases of network connectivity, the loss can be arbitrarily large.
Variance Analysis of Randomized Consensus in Switching Directed Networks
Venue: arXiv cs.MA 2009
Year: 2009

In this paper, we study the asymptotic properties of distributed consensus algorithms over switching directed random networks. More specifically, we focus on consensus algorithms over independent and identically distributed, directed Erdos-Renyi random graphs, where each agent can communicate with any other agent with some exogenously specified probability $p$. While it is well-known that consensus algorithms over Erdos-Renyi random networks result in an asymptotic agreement over the network, an analytical characterization of the distribution of the asymptotic consensus value is still an open question. In this paper, we provide closed-form expressions for the mean and variance of the asymptotic random consensus value, in terms of the size of the network and the probability of communication $p$. We also provide numerical simulations that illustrate our results.
On the Delay-Throughput Tradeoff in Distributed Wireless Networks
Venue: arXiv cs.IT 2009
Year: 2009

This paper deals with the delay-throughput analysis of a single-hop wireless network with $n$ transmitter/receiver pairs. All channels are assumed to be block Rayleigh fading with shadowing, described by parameters $(α,\varpi)$, where $α$ denotes the probability of shadowing and $\varpi$ represents the average cross-link gains. The analysis relies on the distributed on-off power allocation strategy (i.e., links with a direct channel gain above a certain threshold transmit at full power and the rest remain silent) for the deterministic and stochastic packet arrival processes. It is also assumed that each transmitter has a buffer size of one packet and dropping occurs once a packet arrives in the buffer while the previous packet has not been served. In the first part of the paper, we define a new notion of performance in the network, called effective throughput, which captures the effect of arrival process in the network throughput, and maximize it for different cases of packet arrival process. It is proved that the effective throughput of the network asymptotically scales as $\frac{\log n}{\hatα}$, with $\hatα \triangleq α\varpi$, regardless of the packet arrival process. In the second part of the paper, we present the delay characteristics of the underlying network in terms of the packet dropping probability. We derive the sufficient conditions in the asymptotic case of $n \to \infty$ such that the packet dropping probability tend to zero, while achieving the maximum effective throughput of the network. Finally, we study the trade-off between the effective throughput, delay, and packet dropping probability of the network for different packet arrival processes.
Heuristic Methods for Security Protocols
Venue: arXiv cs.CR 2009
Year: 2009

Model checking is an automatic verification technique to verify hardware and software systems. However it suffers from state-space explosion problem. In this paper we address this problem in the context of cryptographic protocols by proposing a security property-dependent heuristic. The heuristic weights the state space by exploiting the security formulae; the weights may then be used to explore the state space when searching for attacks.
Swarm Intelligence
Venue: arXiv cs.NE 2009
Year: 2009

Biologically inspired computing is an area of computer science which uses the advantageous properties of biological systems. It is the amalgamation of computational intelligence and collective intelligence. Biologically inspired mechanisms have already proved successful in achieving major advances in a wide range of problems in computing and communication systems. The consortium of bio-inspired computing are artificial neural networks, evolutionary algorithms, swarm intelligence, artificial immune systems, fractal geometry, DNA computing and quantum computing, etc. This article gives an introduction to swarm intelligence.
Collaborative Relay Beamforming for Secrecy
Venue: arXiv cs.IT 2009
Year: 2009

In this paper, collaborative use of relays to form a beamforming system with the aid of perfect channel state information (CSI) and to provide physical-layer security is investigated. In particular, a decode-and-forward-based relay beamforming design subject to total and individual relay power constraints is studied with the goal of maximizing the secrecy rate. It is shown that the total power constraint leads to a closed-form solution. The design under individual relay power constraints is formulated as an optimization problem which is shown to be easily solved using two different approaches, namely semidefinite programming and second-order cone programming. Furthermore, a simplified and suboptimal technique which reduces the computation complexity under individual power constraints is presented.
Digital Curvatures Applied to 3D Object Analysis and Recognition: A Case Study
Venue: arXiv cs.CG 2009
Year: 2009

In this paper, we propose using curvatures in digital space for 3D object analysis and recognition. Since direct adjacency has only six types of digital surface points in local configurations, it is easy to determine and classify the discrete curvatures for every point on the boundary of a 3D object. Unlike the boundary simplicial decomposition (triangulation), the curvature can take any real value. It sometimes makes difficulties to find a right value for threshold. This paper focuses on the global properties of categorizing curvatures for small regions. We use both digital Gaussian curvatures and digital mean curvatures to 3D shapes. This paper proposes a multi-scale method for 3D object analysis and a vector method for 3D similarity classification. We use these methods for face recognition and shape classification. We have found that the Gaussian curvatures mainly describe the global features and average characteristics such as the five regions of a human face. However, mean curvatures can be used to find local features and extreme points such as nose in 3D facial data.
Time Delay Estimation in Cognitive Radio Systems
Venue: arXiv cs.IT 2009
Year: 2009

In cognitive radio systems, secondary users can utilize multiple dispersed bands that are not used by primary users. In this paper, time delay estimation of signals that occupy multiple dispersed bands is studied. First, theoretical limits on time delay estimation are reviewed. Then, two-step time delay estimators that provide trade-offs between computational complexity and performance are investigated. In addition, asymptotic optimality properties of the two-step time delay estimators are discussed. Finally, simulation results are presented to explain the theoretical results.
K-User Fading Interference Channels: The Ergodic Very Strong Case
Venue: arXiv cs.IT 2009
Year: 2009

Sufficient conditions required to achieve the interference-free capacity region of ergodic fading K-user interference channels (IFCs) are obtained. In particular, this capacity region is shown to be achieved when every receiver decodes all K transmitted messages such that the channel statistics and the waterfilling power policies for all K (interference-free) links satisfy a set of K(K-1) ergodic very strong conditions. The result is also of independent interest in combinatorics.
On Physically Secure and Stable Slotted ALOHA System
Venue: arXiv cs.IT 2009
Year: 2009

In this paper, we consider the standard discrete-time slotted ALOHA with a finite number of terminals with infinite size buffers. In our study, we jointly consider the stability of this system together with the physical layer security. We conduct our studies on both dominant and original systems, where in a dominant system each terminal always has a packet in its buffer unlike in the original system. For N = 2, we obtain the secrecy-stability regions for both dominant and original systems. Furthermore, we obtain the transmission probabilities, which optimize system throughput. Lastly, this paper proposes a new methodology in terms of obtaining the joint stability and secrecy regions.
The Uned systems at Senseval-2
Venue: arXiv cs.CL 2009
Year: 2009

We have participated in the SENSEVAL-2 English tasks (all words and lexical sample) with an unsupervised system based on mutual information measured over a large corpus (277 million words) and some additional heuristics. A supervised extension of the system was also presented to the lexical sample task. Our system scored first among unsupervised systems in both tasks: 56.9% recall in all words, 40.2% in lexical sample. This is slightly worse than the first sense heuristic for all words and 3.6% better for the lexical sample, a strong indication that unsupervised Word Sense Disambiguation remains being a strong challenge.
An Example of Symmetry Exploitation for Energy-related Eigencomputations
Venue: arXiv cs.NA 2009
Year: 2009

One of the most used approaches in simulating materials is the tight-binding approximation. When using this method in a material simulation, it is necessary to compute the eigenvalues and eigenvectors of the Hamiltonian describing the system. In general, the system possesses few explicit symmetries. Due to them, the problem has many degenerate eigenvalues. The ambiguity in choosing a orthonormal basis of the invariant subspaces, associated with degenerate eigenvalues, will result in eigenvectors which are not invariant under the action of the symmetry operators in matrix form. A meaningful computation of the eigenvectors needs to take those symmetries into account. A natural choice is a set of eigenvectors, which simultaneously diagonalizes the Hamiltonian and the symmetry matrices. This is possible because all the matrices commute with each other. The simultaneous eigenvectors and the corresponding eigenvalues will be in a parametrized form in terms of the lattice momentum components. This functional dependence of the eigenvalues is the dispersion relation and describes the band structure of a material. Therefore it is important to find this functional dependence in any numerical computation related to material properties.
The Cyborg Astrobiologist: Testing a Novelty-Detection Algorithm on Two Mobile Exploration Systems at Rivas Vaciamadrid in Spain and at the Mars Desert Research Station in Utah
Venue: arXiv cs.CV 2009
Year: 2009

(ABRIDGED) In previous work, two platforms have been developed for testing computer-vision algorithms for robotic planetary exploration (McGuire et al. 2004b,2005; Bartolo et al. 2007). The wearable-computer platform has been tested at geological and astrobiological field sites in Spain (Rivas Vaciamadrid and Riba de Santiuste), and the phone-camera has been tested at a geological field site in Malta. In this work, we (i) apply a Hopfield neural-network algorithm for novelty detection based upon color, (ii) integrate a field-capable digital microscope on the wearable computer platform, (iii) test this novelty detection with the digital microscope at Rivas Vaciamadrid, (iv) develop a Bluetooth communication mode for the phone-camera platform, in order to allow access to a mobile processing computer at the field sites, and (v) test the novelty detection on the Bluetooth-enabled phone-camera connected to a netbook computer at the Mars Desert Research Station in Utah. This systems engineering and field testing have together allowed us to develop a real-time computer-vision system that is capable, for example, of identifying lichens as novel within a series of images acquired in semi-arid desert environments. We acquired sequences of images of geologic outcrops in Utah and Spain consisting of various rock types and colors to test this algorithm. The algorithm robustly recognized previously-observed units by their color, while requiring only a single image or a few images to learn colors as familiar, demonstrating its fast learning capability.
Vector Bin Packing with Multiple-Choice
Venue: arXiv cs.DS 2009
Year: 2009

We consider a variant of bin packing called multiple-choice vector bin packing. In this problem we are given a set of items, where each item can be selected in one of several $D$-dimensional incarnations. We are also given $T$ bin types, each with its own cost and $D$-dimensional size. Our goal is to pack the items in a set of bins of minimum overall cost. The problem is motivated by scheduling in networks with guaranteed quality of service (QoS), but due to its general formulation it has many other applications as well. We present an approximation algorithm that is guaranteed to produce a solution whose cost is about $\ln D$ times the optimum. For the running time to be polynomial we require $D=O(1)$ and $T=O(\log n)$. This extends previous results for vector bin packing, in which each item has a single incarnation and there is only one bin type. To obtain our result we also present a PTAS for the multiple-choice version of multidimensional knapsack, where we are given only one bin and the goal is to pack a maximum weight set of (incarnations of) items in that bin.