HMM-based on-line signature verification: Feature extraction and signature modeling

A function-based approach to on-line signature verification is presented. The system uses a set of time sequences and Hidden Markov Models (HMMs). Development and evaluation experiments are reported on a subcorpus of the MCYT bimodal biometric database comprising more than 7000 signatures from 145 subjects. The system is compared to other state-of-the-art systems based on the results of the First International Signature Verification Competition (SVC 2004). A number of practical findings related to feature extraction and modeling are obtained.     

Building and implementing policies in autonomous and autonomic systems using MaCMAS

Autonomic Computing, self-management based on high level guidance from humans, is increasingly being accepted as a means forward in designing reliable systems that both hide complexity from the user and control IT management costs. Effectively, AC may be viewed as policy-based self-management. We look at ways of achieving this, with particular focus on agent-oriented software engineering. We propose utilizing MaCMAS, an AOSE methodology for specifying autonomic and autonomous properties of the system independently. Later, by means of composition of these specifications, guided by a policy specification, we construct a specification for the policy and its subsequent deployment. We illustrate this by means of a case study based on a NASA concept mission and describe future work on a support toolkit. This work has been partially supported by the European Commission (FEDER) and Spanish Government under CICYT project Web-Factories (TIN2006-00472) and grant TIC2003-02737-C02-01, by NASA Software Engineering Laboratory and NASA office of Safety and Mission Assurance Software Assurance Research Program (SARP), and at University of Ulster by the Computer Science Research Institute (CSRI) and the Centre for Software Process Technologies (CSPT), funded by Invest NI through the Centres of Excellence Programme, under the EU Peace II initiative.     

Comparative analysis of the factors associated with citation and media coverage of clinical research

Our objective was to study the relationship between the design and content of randomized clinical trials (RCTs) and the subsequent number of citations in the medical literature and attention in online news and social media. We studied RCTs published during 2014 in five highly cited medical journals. This was a retrospective review focusing on characteristics of the individual trials and measures of citation and lay media attention. Primary outcome measures included citation count and Altmetric^® scores (a composite score measuring attention in news, blogs, Twitter^®, and Facebook^®). Two hundred and forty two RCTs were included in the final analysis. Trial characteristics that were positive predictors of citation count included investigation of Hepatitis C treatment (r = 0.35, p < 0.001), private funding (r = 0.24, p < 0.001), mortality-related endpoint (r = 0.22, p < 0.001), and research setting within the United States (r = 0.13, p < 0.001). The trial characteristic that positively predicted Altmetric score was the population size potentially affected (r = 0.39, p < 0.001). The only negative predictor of citation count was the size of the population potentially affected (r = ?0.21, p < 0.001). Negative predictors of the Altmetric score included investigation of Hepatitis C treatment (r = ?0.21, p < 0.001) and private funding (r = ?0.13, p < 0.001). While correlation magnitudes were weak, the predictors of biomedical literature citation and non-academic media coverage were different. These predictors may affect editorial decisions and, given the rising influence of health journalism, further study is warranted.     

Strength and thermal shock resistance of fiber-bonded Si-Al-C-O and Si-Ti-C-O ceramics

Silicon carbide-based fiber-bonded ceramics, obtained from hot pressing of woven silicon carbide fibers, are a cost-effective alternative to ceramic-matrix composites due to their ease of fabrication, involving few processing steps, and competitive thermomechanical properties. In this work, we studied the high-temperature strength and thermal shock resistance of Si-Al-C-O and Si-Ti-C-O fiber-bonded SiC ceramics obtained from hot pressing of two types of ceramic fibers, by mechanical testing in four-point bending. The bending strength of Si-Al-C-O-based fiber-bonded ceramics at room temperature is ∼250–260 MPa and remains constant with temperature, while the bending strength of Si-Ti-C-O increases slightly from the initial 220 to ∼250 MPa for the highest temperature. Both materials retain up to 90% of their room temperature strength after thermal shocks of 1400°C and show no reduction in elastic moduli. After thermal shock, failure mode is the same as in the case of as-received materials.     

Effect of Mo and W interlayers on microstructure and mechanical properties of Si3N4–nickel-base superalloy joints

Si₃N₄/nickel-base superalloy (Inconel-625) and Si₃N₄/Si₃N₄ joints with refractory metal (W and Mo) interlayers were vacuum brazed using a Ti-active braze Cu-ABA (92.75Cu–3Si–2Al–2.25Ti) at 1317 K for 30 min with the following interlayered arrangements: Si₃N₄/Mo/W/Inconel and Si₃N₄/Mo/W/Si₃N₄. The joints exhibited Ti segregation at the Si₃N₄/Cu-ABA interface, elemental interdiffusion across the joint interfaces, and sound metallurgical bonding. Knoop microhardness profiles revealed hardness gradients across the joints that mimicked the interlayered arrangement. The compressive shear strength of Si₃N₄/Si₃N₄ joints both with and without W and Mo layers was ∼142 MPa but the strength of Si₃N₄/Inconel joints increased from ∼9 MPa for directly bonded joints without interlayers to 53.5 MPa for joints with Mo and W interlayers.     

Towards Fully Secure 5G Ultra-Low Latency Communications: ACost-Security Functions Analysis

Future components to enhance the basic, native security of 5G networks are either complex mechanisms whose impact in the requiring 5G communications are not considered, or lightweight solutions adapted to ultra-reliable low-latency communications (URLLC) but whose security properties remain under discussion. Although different 5G network slices may have different requirements, in general, both visions seem to fall short at provisioning secure URLLC in the future. In this work we address this challenge, by introducing cost-security functions as a method to evaluate the performance and adequacy of most developed and employed non-native enhanced security mechanisms in 5G networks. We categorize those new security components into different groups according to their purpose and deployment scope. We propose to analyze them in the context of existing 5G architectures using two different approaches. First, using model checking techniques, we will evaluate the probability of an attacker to be successful against each security solution. Second, using analytical models, we will analyze the impact of these security mechanisms in terms of delay, throughput consumption, and reliability. Finally, we will combine both approaches using stochastic cost-security functions and the PRISM model checker to create a global picture. Our results are first evidence of how a 5G network that covers and strengthened all security areas through enhanced, dedicated non-native mechanisms could only guarantee secure URLLC with a probability of ∼55%.     

A Holistic Solution to Icing by Acoustic Waves: De-Icing,Active Anti-Icing,Sensing with Piezoelectric Crystals,and Synergy with Thin Film Passive Anti-Icing Solutions

Icing has become a hot topic both in academia and in the industry given its implications in transport, wind turbines, photovoltaics, and telecommunications. Recently proposed de-icing solutions involving the propagation of acoustic waves (AWs) at suitable substrates may open the path for a sustainable alternative to standard de-icing or anti-icing procedures. Herein, the fundamental interactions are unraveled that contribute to the de-icing and/or hinder the icing on AW-activated substrates. The response toward icing of a reliable model system consisting of a piezoelectric plate activated by extended electrodes is characterized at a laboratory scale and in an icing wind tunnel under realistic conditions. Experiments show that surface modification with anti-icing functionalities provides a synergistic response when activated with AWs. A thoughtful analysis of the resonance frequency dependence on experimental variables such as temperature, ice formation, or wind velocity demonstrates the application of AW devices for real-time monitoring of icing processes.