OpenRaiser/Intern-Atlas huggingface dataset:
Optimal Lower Bound for Itemset Frequency Indicator Sketches
Venue: arXiv cs.DS 2014
Year: 2014

Given a database, a common problem is to find the pairs or $k$-tuples of items that frequently co-occur. One specific problem is to create a small space "sketch" of the data that records which $k$-tuples appear in more than an $ε$ fraction of rows of the database. We improve the lower bound of Liberty, Mitzenmacher, and Thaler [LMT14], showing that $Ω(\frac{1}εd \log (εd))$ bits are necessary even in the case of $k=2$. This matches the sampling upper bound for all $ε\geq 1/d^{.99}$, and (in the case of $k=2$) another trivial upper bound for $ε= 1/d$.
Multi-Party Set Reconciliation Using Characteristic Polynomials
Venue: arXiv cs.DS 2014
Year: 2014

In the standard set reconciliation problem, there are two parties $A_1$ and $A_2$, each respectively holding a set of elements $S_1$ and $S_2$. The goal is for both parties to obtain the union $S_1 \cup S_2$. In many distributed computing settings the sets may be large but the set difference $|S_1-S_2|+|S_2-S_1|$ is small. In these cases one aims to achieve reconciliation efficiently in terms of communication; ideally, the communication should depend on the size of the set difference, and not on the size of the sets. Recent work has considered generalizations of the reconciliation problem to multi-party settings, using a framework based on a specific type of linear sketch called an Invertible Bloom Lookup Table. Here, we consider multi-party set reconciliation using the alternative framework of characteristic polynomials, which have previously been used for efficient pairwise set reconciliation protocols, and compare their performance with Invertible Bloom Lookup Tables for these problems.
Challenge IEEE-ISBI/TCB : Application of Covariance matrices and wavelet marginals
Venue: arXiv cs.CV 2014
Year: 2014

This short memo aims at explaining our approach for the challenge IEEE-ISBI on Bone Texture Characterization. In this work, we focus on the use of covariance matrices and wavelet marginals in an SVM classifier.
Distributed SIR-Aware Opportunistic Access Control for D2D Underlaid Cellular Networks
Venue: arXiv cs.NI 2014
Year: 2014

In this paper, we propose a distributed interference and channel-aware opportunistic access control technique for D2D underlaid cellular networks, in which each potential D2D link is active whenever its estimated signal-to-interference ratio (SIR) is above a predetermined threshold so as to maximize the D2D area spectral efficiency. The objective of our SIR-aware opportunistic access scheme is to provide sufficient coverage probability and to increase the aggregate rate of D2D links by harnessing interference caused by dense underlaid D2D users using an adaptive decision activation threshold. We determine the optimum D2D activation probability and threshold, building on analytical expressions for the coverage probabilities and area spectral efficiency of D2D links derived using stochastic geometry. Specifically, we provide two expressions for the optimal SIR threshold, which can be applied in a decentralized way on each D2D link, so as to maximize the D2D area spectral efficiency derived using the unconditional and conditional D2D success probability respectively. Simulation results in different network settings show the performance gains of both SIR-aware threshold scheduling methods in terms of D2D link coverage probability, area spectral efficiency, and average sum rate compared to existing channel-aware access schemes.
Handling Flash-Crowd Events to Improve the Performance of Web Applications
Venue: arXiv cs.DC 2014
Year: 2014

Cloud computing can offer a set of computing resources according to users' demand. It is suitable to be used to handle flash-crowd events in Web applications due to its elasticity and on-demand characteristics. Thus, when Web applications need more computing or storage capacity, they just instantiate new resources. However, providers have to estimate the amount of resources to instantiate to handle with the flash-crowd event. This estimation is far from trivial since each cloud environment provides several kinds of heterogeneous resources, each one with its own characteristics such as bandwidth, CPU, memory and financial cost. In this paper, the Flash Crowd Handling Problem (FCHP) is precisely defined and formulated as an integer programming problem. A new algorithm for handling with a flash crowd named FCHP-ILS is also proposed. With FCHP-ILS the Web applications can replicate contents in the already instantiated resources and define the types and amount of resources to instantiate in the cloud during a flash crowd. Our approach is evaluated considering real flash crowd traces obtained from the related literature. We also present a case study, based on a synthetic dataset representing flash-crowd events in small scenarios aiming at the comparison of the proposed approach against Amazon's Auto-Scale mechanism.
Location Spoofing Detection for VANETs by a Single Base Station in Rician Fading Channels
Venue: arXiv cs.IT 2014
Year: 2014

In this work we examine the performance of a Location Spoofing Detection System (LSDS) for vehicular networks in the realistic setting of Rician fading channels. In the LSDS, an authorized Base Station (BS) equipped with multiple antennas utilizes channel observations to identify a malicious vehicle, also equipped with multiple antennas, that is spoofing its location. After deriving the optimal transmit power and the optimal directional beamformer of a potentially malicious vehicle, robust theoretical analysis and detailed simulations are conducted in order to determine the impact of key system parameters on the LSDS performance. Our analysis shows how LSDS performance increases as the Rician K-factor of the channel between the BS and legitimate vehicles increases, or as the number of antennas at the BS or legitimate vehicle increases. We also obtain the counter-intuitive result that the malicious vehicle's optimal number of antennas conditioned on its optimal directional beamformer is equal to the legitimate vehicle's number of antennas. The results we provide here are important for the verification of location information reported in IEEE 1609.2 safety messages.
Linear Precoding for the MIMO Multiple Access Channel with Finite Alphabet Inputs and Statistical CSI
Venue: arXiv cs.IT 2014
Year: 2014

In this paper, we investigate the design of linear precoders for the multiple-input multiple-output (MIMO) multiple access channel (MAC). We assume that statistical channel state information (CSI) is available at the transmitters and consider the problem under the practical finite alphabet input assumption. First, we derive an asymptotic (in the large system limit) expression for the weighted sum rate (WSR) of the MIMO MAC with finite alphabet inputs and Weichselberger's MIMO channel model. Subsequently, we obtain the optimal structures of the linear precoders of the users maximizing the asymptotic WSR and an iterative algorithm for determining the precoders. We show that the complexity of the proposed precoder design is significantly lower than that of MIMO MAC precoders designed for finite alphabet inputs and instantaneous CSI. Simulation results for finite alphabet signalling indicate that the proposed precoder achieves significant performance gains over existing precoder designs.
Computabilities of Validity and Satisfiability in Probability Logics over Finite and Countable Models
Venue: arXiv cs.LO 2014
Year: 2014

The $ε$-logic (which is called $ε$E-logic in this paper) of Kuyper and Terwijn is a variant of first order logic with the same syntax, in which the models are equipped with probability measures and in which the $\forall x$ quantifier is interpreted as "there exists a set $A$ of measure $\ge 1 - ε$ such that for each $x \in A$, ...." Previously, Kuyper and Terwijn proved that the general satisfiability and validity problems for this logic are, i) for rational $ε\in (0, 1)$, respectively $Σ^1_1$-complete and $Π^1_1$-hard, and ii) for $ε= 0$, respectively decidable and $Σ^0_1$-complete. The adjective "general" here means "uniformly over all languages." We extend these results in the scenario of finite models. In particular, we show that the problems of satisfiability by and validity over finite models in $ε$E-logic are, i) for rational $ε\in (0, 1)$, respectively $Σ^0_1$- and $Π^0_1$-complete, and ii) for $ε= 0$, respectively decidable and $Π^0_1$-complete. Although partial results toward the countable case are also achieved, the computability of $ε$E-logic over countable models still remains largely unsolved. In addition, most of the results, of this paper and of Kuyper and Terwijn, do not apply to individual languages with a finite number of unary predicates. Reducing this requirement continues to be a major point of research. On the positive side, we derive the decidability of the corresponding problems for monadic relational languages --- equality- and function-free languages with finitely many unary and zero other predicates. This result holds for all three of the unrestricted, the countable, and the finite model cases. Applications in computational learning theory, weighted graphs, and neural networks are discussed in the context of these decidability and undecidability results.
Multicore-optimized wavefront diamond blocking for optimizing stencil updates
Venue: arXiv cs.DC 2014
Year: 2014

The importance of stencil-based algorithms in computational science has focused attention on optimized parallel implementations for multilevel cache-based processors. Temporal blocking schemes leverage the large bandwidth and low latency of caches to accelerate stencil updates and approach theoretical peak performance. A key ingredient is the reduction of data traffic across slow data paths, especially the main memory interface. In this work we combine the ideas of multi-core wavefront temporal blocking and diamond tiling to arrive at stencil update schemes that show large reductions in memory pressure compared to existing approaches. The resulting schemes show performance advantages in bandwidth-starved situations, which are exacerbated by the high bytes per lattice update case of variable coefficients. Our thread groups concept provides a controllable trade-off between concurrency and memory usage, shifting the pressure between the memory interface and the CPU. We present performance results on a contemporary Intel processor.
A Study on Impacts of RTT Inaccuracy on Dynamic Bandwidth Allocation in PON and Solution
Venue: arXiv cs.NI 2014
Year: 2014

The circle travelling delay between OLT (Optical Line Terminal) and ONU (Optical Network Unit) is one of most important items in dynamic bandwidth allocation (DBA) algorithms in PON, called RTT (Round Trip Time). The RTT is taken into account when OLT assigns the start times for upstream bandwidth grants. In most case, RTT is estimated before making bandwidth allocation decisions in dynamic bandwidth allocation algorithms. If the estimated RTT is incorrect, the bandwidth allocation decisions are not matched with bandwidth requests of channels. Thus, performance of PON can get worse by deviation of RTT. There are several reasons that cause the RTT to be varying, such as processing delay, distance of OLT and ONU, changing in fiber refractive index resulting from temperature drift, and degree of accuracy of RTT estimation methods. In this paper, we evaluate the impacts of RTT inaccuracy on performance of DBA and identify levels of collision and waste of bandwidth. By this way, we propose a method to remedy the performance degradation encountered by the situation
Characterization of Driver Nodes of Anti-Stable Networks
Venue: arXiv cs.SY 2014
Year: 2014

A controllable network can be driven from any initial state to any desired state using driver nodes. A set of driver nodes to control a network is not unique. It is important to characterize these driver nodes and select the right driver nodes. The work discusses theory and algorithms to select driver node such that largest region of attraction can be obtained considering limited capacity of driver node and with unstable eigenvalues of adjacency matrix. A network which can be controllable using one driver node is considered. Nonuniqueness of driver node poses a challenge to select right driver node when multiple possibilities exist. The work addresses this issue.
POSTER: Privacy-preserving Indoor Localization
Venue: arXiv cs.CR 2014
Year: 2014

Upcoming WiFi-based localization systems for indoor environments face a conflict of privacy interests: Server-side localization violates location privacy of the users, while localization on the user's device forces the localization provider to disclose the details of the system, e.g., sophisticated classification models. We show how Secure Two-Party Computation can be used to reconcile privacy interests in a state-of-the-art localization system. Our approach provides strong privacy guarantees for all involved parties, while achieving room-level localization accuracy at reasonable overheads.
DISARM: A Social Distributed Agent Reputation Model based on Defeasible Logic
Venue: arXiv cs.MA 2014
Year: 2014

Intelligent Agents act in open and thus risky environments, hence making the appropriate decision about who to trust in order to interact with, could be a challenging process. As intelligent agents are gradually enriched with Semantic Web technology, acting on behalf of their users with limited or no human intervention, their ability to perform assigned tasks is scrutinized. Hence, trust and reputation models, based on interaction trust or witness reputation, have been proposed, yet they often presuppose the use of a centralized authority. Although such mechanisms are more popular, they are usually faced with skepticism, since users may question the trustworthiness and the robustness of a central authority. Distributed models, on the other hand, are more complex but they provide personalized estimations based on each agent's interests and preferences. To this end, this article proposes DISARM, a novel distributed reputation model. DISARM deals MASs as social networks, enabling agents to establish and maintain relationships, limiting the disadvantages of the common distributed approaches. Additionally, it is based on defeasible logic, modeling the way intelligent agents, like humans, draw reasonable conclusions from incomplete and possibly conflicting (thus inconclusive) information. Finally, we provide an evaluation that illustrates the usability of the proposed model.
An exploratory study of the suitability of UML-based aspect modeling techniques with respect to their integration into Model-Driven Engineering context
Venue: arXiv cs.SE 2014
Year: 2014

The integration of aspect oriented modeling approaches with model-driven engineering process achieved through their direct transformation to aspect-oriented code is expected to enhance the software development from many perspectives. However, since no aspect modeling technique has been adopted as the standard while the code generation has to be fully dependent on the input model, it becomes imperative to compare all ubiquitous techniques on the basis of some appropriate criteria. This study aims to assess existing UML-based aspect-oriented modeling techniques from the perspective of their suitability with regards to integration into model-driven engineering process through aspect-oriented code generation. We defined an evaluation framework and employed it to evaluate 14 well-published, UML-based aspect-oriented modeling approaches. Further, based on the comparison results, we selected 2 modeling approaches, Reusable Aspect Models and Theme/UML, and proceeded to evaluate them in a detailed way from specific perspectives of design and its mapping to the implementation code. Results of the comparison of 14 approaches show that majority of aspect modeling approaches lack from different perspectives, which results in reducing their use in practice within the context of model-driven engineering. The in-depth comparison of Reusable Aspect Models and Theme/UML reveals some points equally shared by both approaches, and identifies some areas where the former has advantage over the latter.
eTutor: Online Learning for Personalized Education
Venue: arXiv cs.CY 2014
Year: 2014

Given recent advances in information technology and artificial intelligence, web-based education systems have became complementary and, in some cases, viable alternatives to traditional classroom teaching. The popularity of these systems stems from their ability to make education available to a large demographics (see MOOCs). However, existing systems do not take advantage of the personalization which becomes possible when web-based education is offered: they continue to be one-size-fits-all. In this paper, we aim to provide a first systematic method for designing a personalized web-based education system. Personalizing education is challenging: (i) students need to be provided personalized teaching and training depending on their contexts (e.g. classes already taken, methods of learning preferred, etc.), (ii) for each specific context, the best teaching and training method (e.g type and order of teaching materials to be shown) must be learned, (iii) teaching and training should be adapted online, based on the scores/feedback (e.g. tests, quizzes, final exam, likes/dislikes etc.) of the students. Our personalized online system, e-Tutor, is able to address these challenges by learning how to adapt the teaching methodology (in this case what sequence of teaching material to present to a student) to maximize her performance in the final exam, while minimizing the time spent by the students to learn the course (and possibly dropouts). We illustrate the efficiency of the proposed method on a real-world eTutor platform which is used for remedial training for a Digital Signal Processing (DSP) course.
Recognizing implicitly given rational canal surfaces
Venue: arXiv cs.SC 2014
Year: 2014

It is still a challenging task of today to recognize the type of a given algebraic surface which is described only by its implicit representation. In~this paper we will investigate in more detail the case of canal surfaces that are often used in geometric modelling, Computer-Aided Design and technical practice (e.g. as blending surfaces smoothly joining two parts with circular ends). It is known that if the squared medial axis transform is a rational curve then so is also the corresponding surface. However, starting from a polynomial it is not known how to decide if the corresponding algebraic surface is rational canal surface or not. Our goal is to formulate a simple and efficient algorithm whose input is a~polynomial with the coefficients from some subfield of real numbers and the output is the answer whether the surface is a rational canal surface. In the affirmative case we also compute a rational parameterization of the squared medial axis transform which can be then used for finding a rational parameterization of the implicitly given canal surface.
The potential of mobile exhibition as a form of implementation for social transformation and educational expo-design in addressing public social problems
Venue: arXiv cs.CY 2014
Year: 2014

The article analyzes the humanistic basis of expo-design in conjunction with the ideological problems of modern design and the causes of their occurrence. It reveals the potential of mobile exhibition for social transformation in terms of its structural and ideological aesthetic content. It substantiates the effectiveness of expo-design expression's artistic and aesthetic means in viewer personality moral education. It investigates the features of social problems design presentation in the unity of the formative and design material components features of mobile exhibition.
A Fusion Approach for Efficient Human Skin Detection
Venue: arXiv cs.CV 2014
Year: 2014

A reliable human skin detection method that is adaptable to different human skin colours and illu- mination conditions is essential for better human skin segmentation. Even though different human skin colour detection solutions have been successfully applied, they are prone to false skin detection and are not able to cope with the variety of human skin colours across different ethnic. Moreover, existing methods require high computational cost. In this paper, we propose a novel human skin de- tection approach that combines a smoothed 2D histogram and Gaussian model, for automatic human skin detection in colour image(s). In our approach an eye detector is used to refine the skin model for a specific person. The proposed approach reduces computational costs as no training is required; and it improves the accuracy of skin detection despite wide variation in ethnicity and illumination. To the best of our knowledge, this is the first method to employ fusion strategy for this purpose. Qualitative and quantitative results on three standard public datasets and a comparison with state-of-the-art methods have shown the effectiveness and robustness of the proposed approach.
Towards Refactoring DMARF and GIPSY OSS
Venue: arXiv cs.SE 2014
Year: 2014

We present here an exploratory and investigatory study of the requirements, design, and implementation of two opensource software systems: the Distributed Modular Audio Recognition Framework (DMARF), and the General Intensional Programming System (GIPSY). The inception, development, and evolution of the two systems have overlapped and in terms of the involved developers, as well as in their applications. DMARF is a platform independent collection of algorithms for pattern recognition, identification and signal processing in audio and natural language text samples, become a rich platform for the research community in particular to use, test, and compare various algorithms in the broad field of pattern recognition and machine learning. Intended as a platform for intensional programming, GIPSY's inception was intended to push the field of intensional programming further, overcoming limitations in the available tools two decades ago. In this study, we present background research into the two systems and elaborate on their motivations and the requirements that drove and shaped their design and implementation. We subsequently elaborate in more depth about various aspects their architectural design, including the elucidation of some use cases, domain models, and the overall class diagram of the major components. Moreover, we investigated existing design patterns in both systems and provided a detailed view of the involved components in such patterns. Furthermore, we delve deeper into the guts of both systems, identifying code smells and suggesting possible refactorings. Patchsets of implementations of selected refactorings have been collected into patchsets and could be committed into future releases of the two systems, pending a review and approval of the developers and maintainers of DMARF and GIPSY.