OpenRaiser/Intern-Atlas huggingface dataset:
DGFIndex for Smart Grid: Enhancing Hive with a Cost-Effective Multidimensional Range Index
Venue: arXiv cs.DB 2014
Year: 2014

In Smart Grid applications, as the number of deployed electric smart meters increases, massive amounts of valuable meter data is generated and collected every day. To enable reliable data collection and make business decisions fast, high throughput storage and high-performance analysis of massive meter data become crucial for grid companies. Considering the advantage of high efficiency, fault tolerance, and price-performance of Hadoop and Hive systems, they are frequently deployed as underlying platform for big data processing. However, in real business use cases, these data analysis applications typically involve multidimensional range queries (MDRQ) as well as batch reading and statistics on the meter data. While Hive is high-performance at complex data batch reading and analysis, it lacks efficient indexing techniques for MDRQ. In this paper, we propose DGFIndex, an index structure for Hive that efficiently supports MDRQ for massive meter data. DGFIndex divides the data space into cubes using the grid file technique. Unlike the existing indexes in Hive, which stores all combinations of multiple dimensions, DGFIndex only stores the information of cubes. This leads to smaller index size and faster query processing. Furthermore, with pre-computing user-defined aggregations of each cube, DGFIndex only needs to access the boundary region for aggregation query. Our comprehensive experiments show that DGFIndex can save significant disk space in comparison with the existing indexes in Hive and the query performance with DGFIndex is 2-50 times faster than existing indexes in Hive and HadoopDB for aggregation query, 2-5 times faster than both for non-aggregation query, 2-75 times faster than scanning the whole table in different query selectivity.
In Order Packet Delivery in Instantly Decodable Network Coded Systems over Wireless Broadcast
Venue: arXiv cs.NI 2014
Year: 2014

In this paper, we study in-order packet delivery in instantly decodable network coded systems for wireless broadcast networks. We are interested in applications, in which the successful delivery of a packet depends on the correct reception of this packet and all its preceding packets. We formulate the problem of minimizing the number of undelivered packets to all receivers over all transmissions until completion as a stochastic shortest path (SSP) problem. Although finding the optimal packet selection policy using SSP is computationally complex, it allows us to systematically exploit the problem structure and draw guidelines for efficient packet selection policies that can reduce the number of undelivered packets to all receivers over all transmissions until completion. According to these guidelines, we design a simple heuristic packet selection algorithm. Simulation results illustrate that our proposed algorithm provides quicker packet delivery to the receivers compared to the existing algorithms in the literature.
List-Decoding Gabidulin Codes via Interpolation and the Euclidean Algorithm
Venue: arXiv cs.IT 2014
Year: 2014

We show how Gabidulin codes can be list decoded by using a parametrization approach. For this we consider a certain module in the ring of linearized polynomials and find a minimal basis for this module using the Euclidean algorithm with respect to composition of polynomials. For a given received word, our decoding algorithm computes a list of all codewords that are closest to the received word with respect to the rank metric.
A Revised Scheme to Compute Horizontal Covariances in an Oceanographic 3D-VAR Assimilation System
Venue: arXiv cs.NA 2014
Year: 2014

We propose an improvement of an oceanographic three dimensional variational assimilation scheme (3D-VAR), named OceanVar, by introducing a recursive filter (RF) with the third order of accuracy (3rd-RF), instead of a RF with first order of accuracy (1st-RF), to approximate horizontal Gaussian covariances. An advantage of the proposed scheme is that the CPU's time can be substantially reduced with benefits on the large scale applications. Experiments estimating the impact of 3rd-RF are performed by assimilating oceanographic data in two realistic oceanographic applications. The results evince benefits in terms of assimilation process computational time, accuracy of the Gaussian correlation modeling, and show that the 3rd-RF is a suitable tool for operational data assimilation.
Using Scripting Languages to Teach Programming
Venue: arXiv cs.CY 2014
Year: 2014

Nowadays, scripting programming languages like Python, Perl and Ruby are widely used in system programming, scientific computing, etc. Although solving a particular problem in these languages requires less time, less programming effort, and less concepts to be taught to achieve the desired goal, still they are not used as teaching tools. Therefore, the use of scripting languages as a teaching vehicle for programming course is very promising. On the other hand, GUI programming, when performed with such languages, is easy and rewarding, since one sees the result of her work immediately. Thus, we are sure that scripting languages combined with GUI toolkits will be the next big thing in computer education.
Hardware Efficient WiMAX Deinterleaver Capable of Address Generation for Random Interleaving Depths
Venue: arXiv cs.AR 2014
Year: 2014

The variation in the prescribed modulation schemes and code rates for WiMAX interleaver design, as defined by IEEE 802.16 standard, demands a plethora of hardware if all the modulation schemes and code rates have to be unified into a single electronic device. Add to this the complexities involved with the algorithms and permutations of the WiMAX standard, invariably dependent on floor function which is extremely hardware inefficient. This paper is an attempt towards removing the complexities and excess hardware involvement in the implementation of the permutations involved in Deinterleaver designs as defined by IEEE 802.16
FPGA design of a cdma2000 turbo decoder
Venue: arXiv cs.AR 2014
Year: 2014

This paper presents the FPGA hardware design of a turbo decoder for the cdma2000 standard. The work includes a study and mathematical analysis of the turbo decoding process, based on the MAX-Log-MAP algorithm. Results of decoding for a packet size of two hundred fifty bits are presented, as well as an analysis of area versus performance, and the key variables for hardware design in turbo decoding.
Mechanism Design for Data Science
Venue: arXiv cs.GT 2014
Year: 2014

Good economic mechanisms depend on the preferences of participants in the mechanism. For example, the revenue-optimal auction for selling an item is parameterized by a reserve price, and the appropriate reserve price depends on how much the bidders are willing to pay. A mechanism designer can potentially learn about the participants' preferences by observing historical data from the mechanism; the designer could then update the mechanism in response to learned preferences to improve its performance. The challenge of such an approach is that the data corresponds to the actions of the participants and not their preferences. Preferences can potentially be inferred from actions but the degree of inference possible depends on the mechanism. In the optimal auction example, it is impossible to learn anything about preferences of bidders who are not willing to pay the reserve price. These bidders will not cast bids in the auction and, from historical bid data, the auctioneer could never learn that lowering the reserve price would give a higher revenue (even if it would). To address this impossibility, the auctioneer could sacrifice revenue optimality in the initial auction to obtain better inference properties so that the auction's parameters can be adapted to changing preferences in the future. This paper develops the theory for optimal mechanism design subject to good inferability.
Maximum Margin Vector Correlation Filter
Venue: arXiv cs.CV 2014
Year: 2014

Correlation Filters (CFs) are a class of classifiers which are designed for accurate pattern localization. Traditionally CFs have been used with scalar features only, which limits their ability to be used with vector feature representations like Gabor filter banks, SIFT, HOG, etc. In this paper we present a new CF named Maximum Margin Vector Correlation Filter (MMVCF) which extends the traditional CF designs to vector features. MMVCF further combines the generalization capability of large margin based classifiers like Support Vector Machines (SVMs) and the localization properties of CFs for better robustness to outliers. We demonstrate the efficacy of MMVCF for object detection and landmark localization on a variety of databases and demonstrate that MMVCF consistently shows improved pattern localization capability in comparison to SVMs.
The fshape framework for the variability analysis of functional shapes
Venue: arXiv cs.CG 2014
Year: 2014

This article introduces a full mathematical and numerical framework for treating functional shapes (or fshapes) following the landmarks of shape spaces and shape analysis. Functional shapes can be described as signal functions supported on varying geometrical supports. Analysing variability of fshapes' ensembles require the modelling and quantification of joint variations in geometry and signal, which have been treated separately in previous approaches. Instead, building on the ideas of shape spaces for purely geometrical objects, we propose the extended concept of fshape bundles and define Riemannian metrics for fshape metamorphoses to model geometrico-functional transformations within these bundles. We also generalize previous works on data attachment terms based on the notion of varifolds and demonstrate the utility of these distances. Based on these, we propose variational formulations of the atlas estimation problem on populations of fshapes and prove existence of solutions for the different models. The second part of the article examines the numerical implementation of the models by detailing discrete expressions for the metrics and gradients and proposing an optimization scheme for the atlas estimation problem. We present a few results of the methodology on a synthetic dataset as well as on a population of retinal membranes with thickness maps.
Leader-Contention-Based User Matching for 802.11 Multiuser MIMO Networks
Venue: arXiv cs.NI 2014
Year: 2014

In multiuser MIMO (MU-MIMO) LANs, the achievable throughput of a client depends on who are transmitting concurrently with it. Existing MU-MIMO MAC protocols however enable clients to use the traditional 802.11 contention to contend for concurrent transmission opportunities on the uplink. Such a contention-based protocol not only wastes lots of channel time on multiple rounds of contention, but also fails to maximally deliver the gain of MU-MIMO because users randomly join concurrent transmissions without considering their channel characteristics. To address such inefficiency, this paper introduces MIMOMate, a leader-contention-based MU-MIMO MAC protocol that matches clients as concurrent transmitters according to their channel characteristics to maximally deliver the MU-MIMO gain, while ensuring all users to fairly share concurrent transmission opportunities. Furthermore, MIMOMate elects the leader of the matched users to contend for transmission opportunities using traditional 802.11 CSMA/CA. It hence requires only a single contention overhead for concurrent streams, and can be compatible with legacy 802.11 devices. A prototype implementation in USRP-N200 shows that MIMOMate achieves an average throughput gain of 1.42x and 1.52x over the traditional contention-based protocol for 2-antenna and 3-antenna AP scenarios, respectively, and also provides fairness for clients.
Proving Termination of Unfolding Graph Rewriting for General Safe Recursion
Venue: arXiv cs.LO 2014
Year: 2014

In this paper we present a new termination proof and complexity analysis of unfolding graph rewriting which is a specific kind of infinite graph rewriting expressing the general form of safe recursion. We introduce a termination order over sequences of terms together with an interpretation of term graphs into sequences of terms. Unfolding graph rewrite rules expressing general safe recursion can be successfully embedded into the termination order by the interpretation, yielding the polynomial runtime complexity. Moreover, generalising the definition of unfolding graph rewrite rules for general safe recursion, we propose a new criterion for the polynomial runtime complexity of infinite GRSs and for the polynomial size of normal forms in infinite GRSs.
Towards Tight Bounds on Theta-Graphs
Venue: arXiv cs.CG 2014
Year: 2014

We present improved upper and lower bounds on the spanning ratio of $θ$-graphs with at least six cones. Given a set of points in the plane, a $θ$-graph partitions the plane around each vertex into $m$ disjoint cones, each having aperture $θ=2π/m$, and adds an edge to the `closest' vertex in each cone. We show that for any integer $k \geq 1$, $θ$-graphs with $4k+2$ cones have a spanning ratio of $1+2\sin(θ/2)$ and we provide a matching lower bound, showing that this spanning ratio tight. Next, we show that for any integer $k \geq 1$, $θ$-graphs with $4k+4$ cones have spanning ratio at most $1+2\sin(θ/2)/(\cos(θ/2)-\sin(θ/2))$. We also show that $θ$-graphs with $4k+3$ and $4k+5$ cones have spanning ratio at most $\cos(θ/4)/(\cos(θ/2)-\sin(3θ/4))$. This is a significant improvement on all families of $θ$-graphs for which exact bounds are not known. For example, the spanning ratio of the $θ$-graph with 7 cones is decreased from at most 7.5625 to at most 3.5132. These spanning proofs also imply improved upper bounds on the competitiveness of the $θ$-routing algorithm. In particular, we show that the $θ$-routing algorithm is $(1+2\sin(θ/2)/(\cos(θ/2)-\sin(θ/2)))$-competitive on $θ$-graphs with $4k+4$ cones and that this ratio is tight. Finally, we present improved lower bounds on the spanning ratio of these graphs. Using these bounds, we provide a partial order on these families of $θ$-graphs. In particular, we show that $θ$-graphs with $4k+4$ cones have spanning ratio at least $1+2\tan(θ/2)+2\tan^2(θ/2)$. This is somewhat surprising since, for equal values of $k$, the spanning ratio of $θ$-graphs with $4k+4$ cones is greater than that of $θ$-graphs with $4k+2$ cones, showing that increasing the number of cones can make the spanning ratio worse.
Piecewise Boolean algebras and their domains
Venue: arXiv cs.LO 2014
Year: 2014

We characterise piecewise Boolean domains, that is, those domains that arise as Boolean subalgebras of a piecewise Boolean algebra. This leads to equivalent descriptions of the category of piecewise Boolean algebras: either as piecewise Boolean domains equipped with an orientation, or as full structure sheaves on piecewise Boolean domains.
An O(n) Time Algorithm For Maximum Induced Matching In Bipartite Star_123-free Graphs
Venue: arXiv cs.DM 2014
Year: 2014

A matching in a graph is a set of edges no two of which share a common vertex. A matching M is an induced matching if no edge connects two edges of M. The problem of finding a maximum induced matching is known to be NP-hard in general and specifically for bipartite graphs. Lozin has been proposed an O(n^3) time algorithm for this problem on the class of bipartite Star_123,Sun_4-free graphs. In this paper we improve and generalize this result in presenting a simple O(n) time algorithm for maximum induced matching problem in bipartite Star_123-free graphs.
Active Adversaries from an Information-Theoretic Perspective: Data Modification Attacks
Venue: arXiv cs.IT 2014
Year: 2014

We investigate the problem of reliable communication in the presence of active adversaries that can tamper with the transmitted data. We consider a legitimate transmitter-receiver pair connected over multiple communication paths (routes). We propose two new models of adversary, a "memoryless" and a "foreseer" adversary. For both models, the adversaries are placing themselves arbitrarily on the routes, keeping their placement fixed throughout the transmission block. This placement may or may not be known to the transmitter. The adversaries can choose their best modification strategy to increase the error at the legitimate receiver, subject to a maximum distortion constraint. We investigate the communication rates that can be achieved in the presence of the two types of adversaries and the channel (benign) stochastic behavior. For memoryless adversaries, the capacity is derived. Our method is to use the typical set of the anticipated received signal for all possible adversarial strategies (including their best one) in a compound channel that also captures adversarial placement. For the foreseer adversaries, which have enhanced observation capabilities compared to the memoryless ones, we propose a new coding scheme to guarantee resilience, i.e., recovery of the codeword independently of the adversarial (best) choice. We derive an achievable rate and we propose an upper bound on the capacity. We evaluate our general results for specific cases (e.g., binary symbol replacement or erasing attacks), to gain insights.
PySTEMM: Executable Concept Modeling for K-12 STEM Learning
Venue: arXiv cs.CY 2014
Year: 2014

Modeling should play a central role in K-12 STEM education, where it could make classes much more engaging. A model underlies every scientific theory, and models are central to all the STEM disciplines (Science, Technology, Engineering, Math). This paper describes executable concept modeling of STEM concepts using immutable objects and pure functions in Python. I present examples in math, physics, chemistry, and engineering, built using a proof-of-concept tool called PySTEMM . The approach applies to all STEM areas and supports learning with pictures, narrative, animation, and graph plots. Models can extend each other, simplifying getting started. The functional-programming style reduces incidental complexity and code debugging.
Indoor Activity Detection and Recognition for Sport Games Analysis
Venue: arXiv cs.CV 2014
Year: 2014

Activity recognition in sport is an attractive field for computer vision research. Game, player and team analysis are of great interest and research topics within this field emerge with the goal of automated analysis. The very specific underlying rules of sports can be used as prior knowledge for the recognition task and present a constrained environment for evaluation. This paper describes recognition of single player activities in sport with special emphasis on volleyball. Starting from a per-frame player-centered activity recognition, we incorporate geometry and contextual information via an activity context descriptor that collects information about all player's activities over a certain timespan relative to the investigated player. The benefit of this context information on single player activity recognition is evaluated on our new real-life dataset presenting a total amount of almost 36k annotated frames containing 7 activity classes within 6 videos of professional volleyball games. Our incorporation of the contextual information improves the average player-centered classification performance of 77.56% by up to 18.35% on specific classes, proving that spatio-temporal context is an important clue for activity recognition.
Lipschitz Robustness of Finite-state Transducers
Venue: arXiv cs.FL 2014
Year: 2014

We investigate the problem of checking if a finite-state transducer is robust to uncertainty in its input. Our notion of robustness is based on the analytic notion of Lipschitz continuity --- a transducer is K-(Lipschitz) robust if the perturbation in its output is at most K times the perturbation in its input. We quantify input and output perturbation using similarity functions. We show that K-robustness is undecidable even for deterministic transducers. We identify a class of functional transducers, which admits a polynomial time automata-theoretic decision procedure for K-robustness. This class includes Mealy machines and functional letter-to-letter transducers. We also study K-robustness of nondeterministic transducers. Since a nondeterministic transducer generates a set of output words for each input word, we quantify output perturbation using set-similarity functions. We show that K-robustness of nondeterministic transducers is undecidable, even for letter-to-letter transducers. We identify a class of set-similarity functions which admit decidable K-robustness of letter-to-letter transducers.
The Capacity Region of the Source-Type Model for Secret Key and Private Key Generation
Venue: arXiv cs.IT 2014
Year: 2014

The problem of simultaneously generating a secret key (SK) and private key (PK) pair among three terminals via public discussion is investigated, in which each terminal observes a component of correlated sources. All three terminals are required to generate a common secret key concealed from an eavesdropper that has access to public discussion, while two designated terminals are required to generate an extra private key concealed from both the eavesdropper and the remaining terminal. An outer bound on the SK-PK capacity region was established in [1], and was shown to be achievable for one case. In this paper, achievable schemes are designed to achieve the outer bound for the remaining two cases, and hence the SK-PK capacity region is established in general. The main technique lies in the novel design of a random binning-joint decoding scheme that achieves the existing outer bound.
An Information Theoretic Approach to Secret Sharing
Venue: arXiv cs.IT 2014
Year: 2014

A novel information theoretic approach is proposed to solve the secret sharing problem, in which a dealer distributes one or multiple secrets among a set of participants that for each secret only qualified sets of users can recover it by pooling their shares together while non-qualified sets of users obtain no information about the secret even if they pool their shares together. While existing secret sharing systems (implicitly) assume that communications between the dealer and participants are noiseless, this paper takes a more practical assumption that the dealer delivers shares to the participants via a noisy broadcast channel. An information theoretic approach is proposed, which exploits the channel as additional resources to achieve secret sharing requirements. In this way, secret sharing problems can be reformulated as equivalent secure communication problems via wiretap channels, and can be solved by employing powerful information theoretic security techniques. This approach is first developed for the classic secret sharing problem, in which only one secret is to be shared. This classic problem is shown to be equivalent to a communication problem over a compound wiretap channel. The lower and upper bounds on the secrecy capacity of the compound channel provide the corresponding bounds on the secret sharing rate. The power of the approach is further demonstrated by a more general layered multi-secret sharing problem, which is shown to be equivalent to the degraded broadcast multiple-input multiple-output (MIMO) channel with layered decoding and secrecy constraints. The secrecy capacity region for the degraded MIMO broadcast channel is characterized, which provides the secret sharing capacity region. Furthermore, these secure encoding schemes that achieve the secrecy capacity region provide an information theoretic scheme for sharing the secrets.