OpenRaiser/Intern-Atlas huggingface dataset:
Is Light-Tree Structure Optimal for Multicast Routing in Sparse Light Splitting WDM Networks?
Venue: arXiv cs.NI 2010
Year: 2010

To minimize the number of wavelengths required by a multicast session in sparse light splitting wavelength division multiplexing (WDM) networks, a light-hierarchy structure, which occupies the same wavelength on all links, is proposed to span as many destinations as possible. Different from a light-tree, a light-hierarchy accepts cycles, which are used to traverse crosswise a 4-degree (or above) multicast incapable (MI) node twice (or above) and switch two light signals on the same wavelengths to two destinations in the same multicast session. In this paper, firstly, a graph renewal and distance priority light-tree algorithm (GRDP-LT) is introduced to improve the quality of light-trees built for a multicast request. Then, it is extended to compute light-hierarchies. Obtained numerical results demonstrate the GRDP-LT light-trees can achieve a much lower links stress, better wavelength channel cost, and smaller average end-to-end delay as well as diameter than the currently most efficient algorithm. Furthermore, compared to light-trees, the performance in terms of link stress and network throughput is greatly improved again by employing the light-hierarchy, while consuming the same amount of wavelength channel cost.
Testing of sequences by simulation
Venue: arXiv cs.DS 2010
Year: 2010

Let $ξ$ be a random integer vector, having uniform distribution \[\mathbf{P} \{ξ= (i_1,i_2,...,i_n) = 1/n^n \} \ \hbox{for} \ 1 \leq i_1,i_2,...,i_n\leq n.\] A realization $(i_1,i_2,...,i_n)$ of $ξ$ is called \textit{good}, if its elements are different. We present algorithms \textsc{Linear}, \textsc{Backward}, \textsc{Forward}, \textsc{Tree}, \textsc{Garbage}, \textsc{Bucket} which decide whether a given realization is good. We analyse the number of comparisons and running time of these algorithms using simulation gathering data on all possible inputs for small values of $n$ and generating random inputs for large values of $n$.
Computerized adaptive testing: implementation issues
Venue: arXiv cs.CY 2010
Year: 2010

One of the fastest evolving field among teaching and learning research is students' performance evaluation. Computer based testing systems are increasingly adopted by universities. However, the implementation and maintenance of such a system and its underlying item bank is a challenge for an inexperienced tutor. Therefore, this paper discusses the advantages and disadvantages of Computer Adaptive Test (CAT) systems compared to Computer Based Test systems. Furthermore, a few item selection strategies are compared in order to overcome the item exposure drawback of such systems. The paper also presents our CAT system along its development steps. Besides, an item difficulty estimation technique is presented based on data taken from our self-assessment system.
Multiple-access Network Information-flow and Correction Codes
Venue: arXiv cs.IT 2010
Year: 2010

This work considers the multiple-access multicast error-correction scenario over a packetized network with $z$ malicious edge adversaries. The network has min-cut $m$ and packets of length $\ell$, and each sink demands all information from the set of sources $\sources$. The capacity region is characterized for both a "side-channel" model (where sources and sinks share some random bits that are secret from the adversary) and an "omniscient" adversarial model (where no limitations on the adversary's knowledge are assumed). In the "side-channel" adversarial model, the use of a secret channel allows higher rates to be achieved compared to the "omniscient" adversarial model, and a polynomial-complexity capacity-achieving code is provided. For the "omniscient" adversarial model, two capacity-achieving constructions are given: the first is based on random subspace code design and has complexity exponential in $\ell m$, while the second uses a novel multiple-field-extension technique and has $O(\ell m^{|\sources|})$ complexity, which is polynomial in the network size. Our code constructions are "end-to-end" in that all nodes except the sources and sinks are oblivious to the adversaries and may simply implement predesigned linear network codes (random or otherwise). Also, the sources act independently without knowledge of the data from other sources.
Some fascinating series and their sums
Venue: arXiv cs.DM 2010
Year: 2010

In this paper we present some interesting results involving summation of series in particular trigonometric ones. We failed to locate these results in existing literature or in the web like MathWorld (http://mathworld.wolfram.com/) nor could we derive them using software for analytical computation like Maple. The identities are beautiful and involve finite series.
(α, β) Fibonacci Search
Venue: arXiv cs.DS 2010
Year: 2010

Knuth [12, Page 417] states that "the (program of the) Fibonaccian search technique looks very mysterious at first glance" and that "it seems to work by magic". In this work, we show that there is even more magic in Fibonaccian (or else Fibonacci) search. We present a generalized Fibonacci procedure that follows perfectly the implicit optimal decision tree for search problems where the cost of each comparison depends on its outcome.
A Bayesian Methodology for Estimating Uncertainty of Decisions in Safety-Critical Systems
Venue: arXiv cs.AI 2010
Year: 2010

Uncertainty of decisions in safety-critical engineering applications can be estimated on the basis of the Bayesian Markov Chain Monte Carlo (MCMC) technique of averaging over decision models. The use of decision tree (DT) models assists experts to interpret causal relations and find factors of the uncertainty. Bayesian averaging also allows experts to estimate the uncertainty accurately when a priori information on the favored structure of DTs is available. Then an expert can select a single DT model, typically the Maximum a Posteriori model, for interpretation purposes. Unfortunately, a priori information on favored structure of DTs is not always available. For this reason, we suggest a new prior on DTs for the Bayesian MCMC technique. We also suggest a new procedure of selecting a single DT and describe an application scenario. In our experiments on the Short-Term Conflict Alert data our technique outperforms the existing Bayesian techniques in predictive accuracy of the selected single DTs.
A Block Lanczos with Warm Start Technique for Accelerating Nuclear Norm Minimization Algorithms
Venue: arXiv cs.NA 2010
Year: 2010

Recent years have witnessed the popularity of using rank minimization as a regularizer for various signal processing and machine learning problems. As rank minimization problems are often converted to nuclear norm minimization (NNM) problems, they have to be solved iteratively and each iteration requires computing a singular value decomposition (SVD). Therefore, their solution suffers from the high computation cost of multiple SVDs. To relieve this issue, we propose using the block Lanczos method to compute the partial SVDs, where the principal singular subspaces obtained in the previous iteration are used to start the block Lanczos procedure. To avoid the expensive reorthogonalization in the Lanczos procedure, the block Lanczos procedure is performed for only a few steps. Our block Lanczos with warm start (BLWS) technique can be adopted by different algorithms that solve NNM problems. We present numerical results on applying BLWS to Robust PCA and Matrix Completion problems. Experimental results show that our BLWS technique usually accelerates its host algorithm by at least two to three times.
Supporting Information for the Paper: Optimal Ternary Constant-Composition Codes of Weight Four and Distance Five, IEEE Trans. Inform. Theory, To Appear
Venue: arXiv cs.IT 2010
Year: 2010

Supporting Information for the Paper: Optimal Ternary Constant-Composition Codes of Weight Four and Distance Five, IEEE Trans. Inform. Theory, To Appear.
Average Minimum Transmit Power to achieve SINR Targets: Performance Comparison of Various User Selection Algorithms
Venue: arXiv cs.IT 2010
Year: 2010

In multi-user communication from one base station (BS) to multiple users, the problem of minimizing the transmit power to achieve some target guaranteed performance (rates) at users has been well investigated in the literature. Similarly various user selection algorithms have been proposed and analyzed when the BS has to transmit to a subset of the users in the system, mostly for the objective of the sum rate maximization. We study the joint problem of minimizing the transmit power at the BS to achieve specific signal-to-interference-and-noise ratio (SINR) targets at users in conjunction with user scheduling. The general analytical results for the average transmit power required to meet guaranteed performance at the users' side are difficult to obtain even without user selection due to joint optimization required over beamforming vectors and power allocation scalars. We study the transmit power minimization problem with various user selection algorithms, namely semi-orthogonal user selection (SUS), norm-based user selection (NUS) and angle-based user selection (AUS). When the SINR targets to achieve are relatively large, the average minimum transmit power expressions are derived for NUS and SUS for any number of users. For the special case when only two users are selected, similar expressions are further derived for AUS and a performance upper bound which serves to benchmark the performance of other selection schemes. Simulation results performed under various settings indicate that SUS is by far the better user selection criterion.
MT4j - A Cross-platform Multi-touch Development Framework
Venue: arXiv cs.HC 2010
Year: 2010

This article describes requirements and challenges of crossplatform multi-touch software engineering, and presents the open source framework Multi-Touch for Java (MT4j) as a solution. MT4j is designed for rapid development of graphically rich applications on a variety of contemporary hardware, from common PCs and notebooks to large-scale ambient displays, as well as different operating systems. The framework has a special focus on making multi-touch software development easier and more efficient. Architecture and abstractions used by MT4j are described, and implementations of several common use cases are presented.
A Log Auditing Approach for Trust Management in Peer-to-Peer Collaboration
Venue: arXiv cs.DC 2010
Year: 2010

Nowadays we are faced with an increasing popularity of social software including wikis, blogs, micro-blogs and online social networks such as Facebook and MySpace. Unfortunately, the mostly used social services are centralized and personal information is stored at a single vendor. This results in potential privacy problems as users do not have much control over how their private data is disseminated. To overcome this limitation, some recent approaches envisioned replacing the single authority centralization of services by a peer-to-peer trust-based approach where users can decide with whom they want to share their private data. In this peer-to-peer collaboration it is very difficult to ensure that after data is shared with other peers, these peers will not misbehave and violate data privacy. In this paper we propose a mechanism that addresses the issue of data privacy violation due to data disclosure to malicious peers. In our approach trust values between users are adjusted according to their previous activities on the shared data. Users share their private data by specifying some obligations the receivers must follow. We log modifications done by users on the shared data as well as the obligations that must be followed when data is shared. By a log-auditing mechanism we detect users that misbehaved and we adjust their associated trust values by using any existing decentralized trust model.
Mobiles ortsbezogenes Projektmanagement
Venue: arXiv cs.SE 2010
Year: 2010

Classic project management and its tools usually deal with the management of three variables, and their relationships with each other. These are the factors of time, resources (cost) and quality. If one of the variables is to be improved, it always has negative effects on the other two. However, these factors only partially describe the reality of project management. What current project management tools often only consider implicitly is the location of an activity. In this paper, the implications of using location data for project management are clarified and a system that offers mobile support in planning and implementing projects. ----- Klassisches Projektmanagement und seine Werkzeuge befassen sich meist mit der Verwaltung dreier Größen und ihrer Zusammenhänge untereinander. Dabei handelt es sich um die Faktoren Zeit, Ressourcen (Kosten) und Qualität. Falls eine der Größen verbessert werden soll, hat dies immer negative Auswirkungen auf die anderen beiden Größen. Diese Größen beschreiben die Phänomene des Projektmanagement jedoch nur unvollständig. Was bei Projektmanagementwerkzeugen bis dato oft nur implizit durch den Projektleiter einbezogen wird ist ein Ortsbezug. In diesem Beitrag werden die Implikationen durch diesen Ortsbezug konkretisiert und ein System dargestellt, welches Projektleiter bei der Planung und Umsetzung von Projekten mobil wie auch stationär unterstützt.
On the Spectral Efficiency of Links with Multi-antenna Receivers in Non-homogenous Wireless Networks
Venue: arXiv cs.IT 2010
Year: 2010

An asymptotic technique is developed to find the Signal-to-Interference-plus-Noise-Ratio (SINR) and spectral efficiency of a link with N receiver antennas in wireless networks with non-homogeneous distributions of nodes. It is found that with appropriate normalization, the SINR and spectral efficiency converge with probability 1 to asymptotic limits as N increases. This technique is applied to networks with power-law node intensities, which includes homogeneous networks as a special case, to find a simple approximation for the spectral efficiency. It is found that for receivers in dense clusters, the SINR grows with N at rates higher than that of homogeneous networks and that constant spectral efficiencies can be maintained if the ratio of N to node density is constant. This result also enables the analysis of a new scaling regime where the distribution of nodes in the network flattens rather than increases uniformly. It is found that in many cases in this regime, N needs to grow approximately exponentially to maintain a constant spectral efficiency. In addition to strengthening previously known results for homogeneous networks, these results provide insight into the benefit of using antenna arrays in non-homogeneous wireless networks, for which few results are available in the literature.
The Block Neighborhood
Venue: arXiv cs.DM 2010
Year: 2010

We define the block neighborhood of a reversible CA, which is related both to its decomposition into a product of block permutations and to quantum computing. We give a purely combinatorial characterization of the block neighborhood, which helps in two ways. First, it makes the computation of the block neighborhood of a given CA relatively easy. Second, it allows us to derive upper bounds on the block neighborhood: for a single CA as function of the classical and inverse neighborhoods, and for the composition of several CAs. One consequence of that is a characterization of a class of "elementary" CAs that cannot be written as the composition of two simpler parts whose neighborhoods and inverse neighborhoods would be reduced by one half.
Improved linear programming decoding of LDPC codes and bounds on the minimum and fractional distance
Venue: arXiv cs.IT 2010
Year: 2010

We examine LDPC codes decoded using linear programming (LP). Four contributions to the LP framework are presented. First, a new method of tightening the LP relaxation, and thus improving the LP decoder, is proposed. Second, we present an algorithm which calculates a lower bound on the minimum distance of a specific code. This algorithm exhibits complexity which scales quadratically with the block length. Third, we propose a method to obtain a tight lower bound on the fractional distance, also with quadratic complexity, and thus less than previously-existing methods. Finally, we show how the fundamental LP polytope for generalized LDPC codes and nonbinary LDPC codes can be obtained.
Groups defined by automata
Venue: arXiv cs.FL 2010
Year: 2010

This is Chapter 24 in the "AutoMathA" handbook. Finite automata have been used effectively in recent years to define infinite groups. The two main lines of research have as their most representative objects the class of automatic groups (including word-hyperbolic groups as a particular case) and automata groups (singled out among the more general self-similar groups). The first approach implements in the language of automata some tight constraints on the geometry of the group's Cayley graph, building strange, beautiful bridges between far-off domains. Automata are used to define a normal form for group elements, and to monitor the fundamental group operations. The second approach features groups acting in a finitely constrained manner on a regular rooted tree. Automata define sequential permutations of the tree, and represent the group elements themselves. The choice of particular classes of automata has often provided groups with exotic behaviour which have revolutioned our perception of infinite finitely generated groups.
Rational subsets of groups
Venue: arXiv cs.FL 2010
Year: 2010

This text, Chapter 23 in the "AutoMathA" handbook, is devoted to the study of rational subsets of groups, with particular emphasis on the automata-theoretic approach to finitely generated subgroups of free groups. Indeed, Stallings' construction, associating a finite inverse automaton with every such subgroup, inaugurated a complete rewriting of free group algorithmics, with connections to other fields such as topology or dynamics. Another important vector in the chapter is the fundamental Benois' Theorem, characterizing rational subsets of free groups. The theorem and its consequences really explain why language theory can be successfully applied to the study of free groups. Rational subsets of (free) groups can play a major role in proving statements (a priori unrelated to the notion of rationality) by induction. The chapter also includes related results for more general classes of groups, such as virtually free groups or graph groups.
Use of semantic technologies for the development of a dynamic trajectories generator in a Semantic Chemistry eLearning platform
Venue: arXiv cs.AI 2010
Year: 2010

ChemgaPedia is a multimedia, webbased eLearning service platform that currently contains about 18.000 pages organized in 1.700 chapters covering the complete bachelor studies in chemistry and related topics of chemistry, pharmacy, and life sciences. The eLearning encyclopedia contains some 25.000 media objects and the eLearning platform provides services such as virtual and remote labs for experiments. With up to 350.000 users per month the platform is the most frequently used scientific educational service in the German spoken Internet. In this demo we show the benefit of mapping the static eLearning contents of ChemgaPedia to a Linked Data representation for Semantic Chemistry which allows for generating dynamic eLearning paths tailored to the semantic profiles of the users.
Creating a new Ontology: a Modular Approach
Venue: arXiv cs.AI 2010
Year: 2010

Creating a new Ontology: a Modular Approach
Analysis and visualisation of RDF resources in Ondex
Venue: arXiv cs.AI 2010
Year: 2010

Ondex is a data integration and visualization platform developed to support Systems Biology Research. At its core is a data model based on two main principles: first, all information can be represented as a graph and, second, all elements of the graph can be annotated with ontologies. This data model is conformant to the Semantic Web framework, in particular to RDF, and therefore Ondex is ideally positioned as a platform that can exploit the semantic web.
An In-depth Analysis of Spam and Spammers
Venue: arXiv cs.CR 2010
Year: 2010

Electronic mail services have become an important source of communication for millions of people all over the world. Due to this tremendous growth, there has been a significant increase in spam traffic. Spam messes up user's inbox, consumes network resources and spread worms and viruses. In this paper we study the characteristics of spam and the technology used by spammers. In order to counter anti spam technology, spammers change their mode of operation, therefore continues evaluation of the characteristics of spam and spammers technology has become mandatory. These evaluations help us to enhance the existing anti spam technology and thereby help us to combat spam effectively. In order to characterize spam, we collected four hundred thousand spam mails from a corporate mail server for a period of 14 months from January 2006 to February 2007. For analysis we classified spam based on attachment and contents. We observed that spammers use software tools to send spam with attachment. The main features of this software are hiding sender's identity, randomly selecting text messages, identifying open relay machines, mass mailing capability and defining spamming duration. Spammers do not use spam software to send spam without attachment. From our study we observed that, four years old heavy users email accounts attract more spam than four years old light users mail accounts. Relatively new email accounts which are 14 months old do not receive spam. But in some special cases like DDoS attacks, we found that new email accounts receive spam and 14 months old heavy users email accounts have attracted more spam than 14 months old light users. We believe that this analysis could be useful to develop more efficient anti spam techniques.
SPARQL Assist Language-Neutral Query Composer
Venue: arXiv cs.IR 2010
Year: 2010

SPARQL query composition is difficult for the lay-person or even the experienced bioinformatician in cases where the data model is unfamiliar. Established best-practices and internationalization concerns dictate that semantic web ontologies should use terms with opaque identifiers, further complicating the task. We present SPARQL Assist: a web application that addresses these issues by providing context-sensitive type-ahead completion to existing web forms. Ontological terms are suggested using their labels and descriptions, leveraging existing XML support for internationalization and language-neutrality.
Scientific Collaborations: principles of WikiBridge Design
Venue: arXiv cs.AI 2010
Year: 2010

Semantic wikis, wikis enhanced with Semantic Web technologies, are appropriate systems for community-authored knowledge models. They are particularly suitable for scientific collaboration. This paper details the design principles ofWikiBridge, a semantic wiki.
Populous: A tool for populating ontology templates
Venue: arXiv cs.AI 2010
Year: 2010

We present Populous, a tool for gathering content with which to populate an ontology. Domain experts need to add content, that is often repetitive in its form, but without having to tackle the underlying ontological representation. Populous presents users with a table based form in which columns are constrained to take values from particular ontologies; the user can select a concept from an ontology via its meaningful label to give a value for a given entity attribute. Populated tables are mapped to patterns that can then be used to automatically generate the ontology's content. Populous's contribution is in the knowledge gathering stage of ontology development. It separates knowledge gathering from the conceptualisation and also separates the user from the standard ontology authoring environments. As a result, Populous can allow knowledge to be gathered in a straight-forward manner that can then be used to do mass production of ontology content.