Automated circular assume-guarantee reasoning

Model checking is a successful approach for verifying hardware and software systems. Despite its success, the technique suffers from the state explosion problem which arises due to the large state space of real-life systems. One solution to the state explosion problem is compositional verification, that aims to decompose the verification of a large system into the more manageable verification of its components. To account for dependencies between components, assume-guarantee reasoning defines rules that break-up the global verification of a system into local verification of individual components, using assumptions about the rest of the system. In recent years, compositional techniques have gained significant successes following a breakthrough in the ability to automate assume-guarantee reasoning. However, automation has been restricted to simple acyclic assume-guarantee rules. In this work, we focus on automating circular assume-guarantee reasoning in which the verification of individual components mutually depends on each other. We use a sound and complete circular assume-guarantee rule and we describe how to automatically build the assumptions needed for using the rule. Our algorithm accumulates joint constraints on the assumptions based on (spurious) counterexamples obtained from checking the premises of the rule, and uses a SAT solver to synthesize minimal assumptions that satisfy these constraints. To the best of our knowledge, our work is the first to fully automate circular assume-guarantee reasoning. We implemented our approach and compared it with established non-circular compositional methods that use learning or SAT-based techniques. The experiments show that the assumptions generated for the circular rule are generally smaller, and on the larger examples, we obtain a significant speedup.     

Study of nisin adsorption on plasma-treated polymer surfaces for setting up materials with antibacterial properties

Setting up antibacterial materials by nisin adsorption on surfaces depends mainly on the surface properties and the surface treatments allowing the modification of such properties. In order to investigate the factors affecting such adsorption, the native low density polyethylene (LDPE) was modified using Argon/Oxygen (Ar/O₂) plasma, nitrogen (N₂) plasma and plasma-induced grafting of acrylic acid (AA). The films were studied by various characterization techniques. The chemical surface modification was confirmed by X-ray photoelectron spectroscopy (XPS), the wettability of the surfaces was evaluated by contact angle measurements, the surface charge was determined by the zeta potential measurements, and the changes in surface topography and roughness were revealed by atomic force microscopy (AFM). Nisin was adsorbed on the native and the modified surfaces. The antibacterial activity, the nisin adsorbed amount, and the peptide distribution were compared for the four nisin-functionalized films. The highest antibacterial activity was recorded on the Ar/O₂ followed by AA then by N₂ treated films and the lowest activity was on the native film. The observed antibacterial activity was correlated to the type of the surface, hydrophobic and hydrophilic interactions, surface charge, surface topography, nisin adsorbed amount, and nisin distribution on the surfaces.     

Morphological text extraction from images

This paper presents a morphological technique for text extraction from images. The proposed morphological technique is insensitive to noise, skew and text orientation. It is also free from artifacts that are usually introduced by both fixed/optimal global thresholding and fixed-size block-based local thresholding. Examples are presented to illustrate the performance of the proposed method.     

Video Texture and Motion Based Modeling of Rate Variability-Distortion (VD) Curves

We examine and model the bit rate variability-distortion (VD) curve of -4 part 2 variable bit rate (VBR) video encodings. The VD curve has important applications for evaluating the statistical multiplexing of streaming video. We show that the concave VD curve shape at high compression ratios, or equivalently large quantization scales, is influenced by both the texture and the motion information. Based on this insight, we first develop a general VD curve model by analytically expressing the VD curve in terms of elementary statistics (mean, variance, covariance) of the numbers of motion and texture coding bits. In a second step we develop and validate linear and quadratic models for the elementary texture and motion bit statistics, whereby the model parameters are obtained from only two sample encodings. The texture and motion bit models are then employed in our general VD curve model. This work extends our previous work on piecewise models of the VD curve. The texture and motion based VD model obtained from two sample encodings has comparable accuracy to a piecewise model based on three sample encodings. In addition, the texture and motion based VD model provides fundamental insights into how texture and motion affect traffic variability.     

Correction to: An improved binary sparrow search algorithm for feature selection in data classification

Neural Computing and Applications -     

Thermodegradative and morphological behavior of composites of HDPE with surface-treated hydroxyapatite

In the present work, the thermodegradative and morphological behavior of composites of high-density polyethylene and surface-treated hydroxyapatite (HDPE/HA) were studied. Composites were prepared with HDPE, 30 wt% of HA and 2 phr of an ethylene–acrylic acid copolymer (20 wt% of acrylic acid) (EAA) and melt-blended in an internal mixer at 160 °C and 50 rpm. Two sets of composites filled with different surface-treated hydroxyapatite (STHA) were prepared: one HA sample was pretreated with ethylene–acrylic acid copolymer (STHA₁) and the other one with acrylic acid (STHA₂). Thermogravimetric analyses were carried out to evaluate the thermal stability of the composites. The activation energies (Ea) were determined using a numerical method based on the Invariant Kinetic Parameters (IKP). The thermal decomposition of the HDPE/HA composites showed an Ea value of 330 kJ/mol. On the other hand, HDPE/HA/EAA and HDPE/STHA₁ composites showed a sudden decrease in Ea (272 and 270 kJ/mol, respectively). The HDPE/STHA₂ composite exhibited an Ea value of 313 kJ/mol, slightly lower than that of the HDPE/HA composite. Additionally, with the presence of EAA copolymer and acrylic acid in the composites, the nucleation and nucleus growth kinetic-model probabilities decreased compared to those of the HDPE/HA composite. However, there was an increase in the probability of the reaction order of the model. This behavior could be attributed to the morphology of the composites and to the addition of a less thermally stable component, i.e. EAA copolymer and acrylic acid. On the other hand, due to the interaction polymer/surface-treated filler, an increase in the Young Modulus and the tensile strength was observed.     

Two-staged informed dynamic scheduling for sequential belief propagation decoding of LDPC codes

Recent studies have shown that sequential belief propagation decoding of low-density parity-check codes can increase the decoding convergence speed while simultaneously improving the asymptotic performance compared to the conventional flooding scheme. Two of the practical sequential decoding schemes known are the ones by Casado et al. [1] in which informed dynamic scheduling is used for scheduling the sequential updates of the messages. In this letter, we propose a two-staged informed dynamic scheduling that unifies and outperforms the two schemes of [1].     

Synthesis,in Vitro Metabolism,Mutagenicity, and DNA-Adduction of Naphtho[1,2- e ]pyrene

Literature data, although limited, underscore the contribution of C 24 H 14 polycyclic aromatic hydrocarbons to the biological activity of the extracts of complex environmental samples. However, little attention has been given to naphthopyrene (NP) isomers due to lack of synthetic standards and, therefore, lack of studies aimed at unequivocal identification of C 24 H 14 isomers in environmental samples. We hypothesize that naphtho[1,2- e ]pyrene (N[1,2- e ]P), having a fjord region and a bay region might be a potent mutagen. To test our hypothesis, we synthesized N[1,2- e ]P by Suzuki reaction and examined its in vitro metabolism with the S 9 fraction from phenobarbital/ g -naphthoflavone-induced rat liver homogenates. We have tentatively identified its K-region diol as the major metabolite and a fjord region dihydrodiol as minor metabolite. Contrary to our hypothesis, N[1,2- e ]P was not mutagenic in S. typhimurium strain TA 100 and did not induce morphological cell transformation in mammalian cells. Its metabolite, 11,12-dihydroxy-11,12-dihydro-N[1,2- e ]P was a weak mutagen. The reaction of calf thymus DNA with N[1,2- e ]P-11,12-diol-13,14-epoxide showed that it reacts predominately with the exocyclic amino group of adenine.     

Thermal, mechanical, morphological, thermogravimetric, rheological and toxicological behavior of HDPE/seaweed residues composites

The objective of this research was to study the thermal, mechanical, rheological and toxicological behavior of high-density polyethylene composites filled with seaweed residues (SR) at different compositions (10, 20, 30, 40 wt%), using Lica 12 as coupling agent at concentrations between 0 and 1.0 wt%. From the thermal analysis, it can be inferred that crystallinity increased with filler content as well as crystallization temperatures. The initial decomposition temperature of materials did not show significant changes varying between 482 and 485 °C. Regarding the mechanical behavior, a slight increase in Young’s modulus from 652 to 738 MPa was observed. Elongation at break decreased drastically from 1000% to 20% while strength at break remained approximately constant. Melt flow index decreased from 5.08 to 3.57 g/10 min. Based on the results, it is possible to select any filler content as a candidate for bone substitute material. Therefore, for toxicity studies we chose 40% composite. The inclusion of SR in polymeric matrix proved to be biocompatible with animal tissue, showing no adverse reactions, which allows its possible application in biomedicine.