Star-like auto-configurable layouts of variable radius for visualizing and exploring RDF/S ontologies

The visualization of ontologies is a challenging task especially if they are large. In this paper we propose a visualization approach which is based on star-like graphs of variable radius which enables users to gradually explore and navigate through the entire ontology without overloading them. The star-like graphs are visualized using a Force Directed Placement algorithm (FDP) specially suited for RDF schemas whose configuration parameters can be adjusted interactively by the end-user via an intuitive on-screen tool bar. In addition, and since each star-like graph exhibits different graph features, we propose a novel automatic configuration method for the FDP algorithm parameters that is based on a number of quality metrics (area density and verticality of subclass hierarchies) and corresponding corrective actions. The experimental evaluation showed the quality of the yielded layout is significantly improved and the proposed approach is acceptably fast for real-time exploration. The user study showed that users prefer these views and perform various very common tasks faster.     

An accelerated first-order method for solving SOS relaxations of unconstrained polynomial optimization problems

Our interest lies in solving sum of squares (SOS) relaxations of large-scale unconstrained polynomial optimization problems. Because interior-point methods for solving these problems are severely limited by the large-scale, we are motivated to explore efficient implementations of an accelerated first-order method to solve this class of problems. By exploiting special structural properties of this problem class, we greatly reduce the computational cost of the first-order method at each iteration. We report promising computational results as well as a curious observation about the behaviour of the first-order method for the SOS relaxations of the unconstrained polynomial optimization problem.     

Applying the Mahalanobis-Taguchi strategy for software defect diagnosis

The Mahalanobis-Taguchi (MT) strategy combines mathematical and statistical concepts like Mahalanobis distance, Gram-Schmidt orthogonalization and experimental designs to support diagnosis and decision-making based on multivariate data. The primary purpose is to develop a scale to measure the degree of abnormality of cases, compared to “normal” or “healthy” cases, i.e. a continuous scale from a set of binary classified cases. An optimal subset of variables for measuring abnormality is then selected and rules for future diagnosis are defined based on them and the measurement scale. This maps well to problems in software defect prediction based on a multivariate set of software metrics and attributes. In this paper, the MT strategy combined with a cluster analysis technique for determining the most appropriate training set, is described and applied to well-known datasets in order to evaluate the fault-proneness of software modules. The measurement scale resulting from the MT strategy is evaluated using ROC curves and shows that it is a promising technique for software defect diagnosis. It compares favorably to previously evaluated methods on a number of publically available data sets. The special characteristic of the MT strategy that it quantifies the level of abnormality can also stimulate and inform discussions with engineers and managers in different defect prediction situations.     

Stress in interactive applications: analysis of the valence-arousal space based on physiological signals and self-reported data

Measuring users’ emotional reaction to interactive multimedia and hypermedia is important. One particularly popular self-reported method for emotion assessment is the Valence-Arousal (VA) Scale: a 9?×?9 affective grid. This paper aims to identify specific stress region(s) in the VA space by combining self-reported ratings (pairs of VA) and physiological signals (skin conductance). To this end, 31 healthy volunteers participated in an experiment by performing five stressful interaction tasks while their skin conductance was monitored. The selected interaction tasks were most frequently listed as stressful by a separate group of 15 interviewees. After each task, participants expressed their perceived emotional experience using the VA rating space. Our findings show which regions in the VA rating space may reliably indicate self-reported stress that is in alignment with one’s measured skin conductance while using interactive applications. One additional important contribution of this work is the proposed approach for the empirical identification of affect regions in the VA space based on physiological signals.     

Continuous authentication on relational streams

According to the database outsourcing model, a data owner delegates database functionality to a third-party service provider, which answers queries received from clients. Authenticated query processing enables the clients to verify the correctness of query results. Despite the abundance of methods for authenticated processing in conventional databases, there is limited work on outsourced data streams. Stream environments pose new challenges such as the need for fast structure updating, support for continuous query processing and authentication, and provision for temporal completeness. Specifically, in addition to the correctness of individual results, the client must be able to verify that there are no missing results in between data updates. This paper presents a comprehensive set of methods covering relational streams. We first describe REF, a technique that achieves correctness and temporal completeness but incurs false transmissions, i.e., the provider has to inform the clients whenever there is a data update, even if their results are not affected. Then, we propose CADS, which minimizes the processing and transmission overhead through an elaborate indexing scheme and a virtual caching mechanism. In addition, we present an analytical study to determine the optimal indexing granularity, and extend CADS for the case that the data distribution changes over time. Finally, we evaluate the effectiveness of our techniques through extensive experiments.     

Stabilization of Nanoalumina Colloidal Slips

The processing of nanosized powders to produce dense components is a difficult task, mainly due to the strong agglomeration of nanoparticles. In this work, deagglomeration studies were carried out on sol–gel‐derived γ‐alumina suspensions through the addition of dispersant or dispersant in combination with ethylene glycol as binder and the proper wet ball‐milling. For this purpose, zeta‐potential, viscosity, and sedimentation studies were carried out, whereas dilatometric studies accompanied by XRD analyses were performed on the powders derived from the most stable suspensions. Sintering studies followed and the as received ceramics were evaluated by SEM. The optimum stabilization was achieved through the synergistic addition of 2.75 mg/g ammonium polymethacrylate with 1 wt% ethylene glycol. The respective powder, although it indicates a shift of the sintering start to higher temperature, leads to the densest ceramic with the finest (500 nm mean grain size) and the most homogeneous microstructure.     

A GENERALIZED BLOCK BOOTSTRAP FOR SEASONAL TIME SERIES

When time‐series data contain a periodic/seasonal component, the usual block bootstrap procedures are not directly applicable. We propose a modification of the block bootstrap – the generalized seasonal block bootstrap (GSBB) – and show its asymptotic consistency without undue restrictions on the relative size of the period and block size. Notably, it is exactly such restrictions that limit the applicability of other proposals of block bootstrap methods for time series with periodicities. The finite‐sample performance of the GSBB is also illustrated by means of a small simulation experiment.     

Factors Associated with Platelet Activation-Recent Pharmaceutical Approaches

Platelets are at the forefront of human health and disease following the advances in their research presented in past decades. Platelet activation, their most crucial function, although beneficial in the case of vascular injury, may represent the initial step for thrombotic complications characterizing various pathologic states, primarily atherosclerotic cardiovascular diseases. In this review, we initially summarize the structural and functional characteristics of platelets. Next, we focus on the process of platelet activation and its associated factors, indicating the potential molecular mechanisms involving inflammation, endothelial dysfunction, and miRs. Finally, an overview of the available antiplatelet agents is being portrayed, together with agents possessing off-set platelet-inhibitory actions, while an extensive presentation of drugs under investigation is being given.