Stuttering-Insensitive Automata for On-the-fly Detection of Livelock Properties

The research examines liveness and progress properties of concurrent systems and their on-the-fly verification. An alternative formalism to Büchi automata, called testing automata, is developed. The basic idea of testing automata is to observe changes in the values of state propositions instead of the values. Therefore, the testing automata are able to accept only stuttering-insensitive languages. Testing automata can accept the same stuttering-insensitive languages as (state-labelled) Büchi automata, and they have at most the same number of states. They are also more often deterministic. Moreover, on-the-fly verification using testing automata can often (but not always) use an algorithm performing only one search in the state space, whereas on-the-fly verification with Büchi automata requires two searches. Experimental results illustrating the benefits of testing automata are presented.     

The effect of titanium ion implantation into carbon ceramic on its wettability by liquid copper

There is a growing interest in the carbon ceramics and their use in present technology. Among other problems, the joining of such ceramics with other materials presents an important challenge. Since joining with metals is associated with wetting, we studied the effect of ion implantation on wetting of various forms of carbon and of silicon carbide by copper. An essential result is that Ti ion implantation followed by ArcPVD Ti deposition results in excellent wettability in all studied cases.     

Finely Tuned Submicroporous Thin-Film Molecular Sieve Membranes for Highly Efficient Fluid Separations

Polymeric membranes with increasingly high permselective performances are gaining a significant role in lowering the energy burden and improving the environmental sustainability of complex chemical separations. However, the commercial deployment of newly designed materials with promising intrinsic properties for fluid separations has been stalled by challenges associated with fabrication and scale up of low-cost, high-performance, defect-free thin-film composite (TFC) membranes. Here, a facile method to fabricate next-generation TFC membranes using a bridged-bicyclic triptycene tetra-acyl chloride (Trip) building block with a large fraction of finely tuned structural submicroporosity (pore size < 4 Å) is demonstrated. The TFCs exhibit superb potential for removal of small (≈200 g mol⁻¹) organic microcontaminants from organic solvent streams by showing both improved rejection and permeance in organic systems compared to current state-of-the-art commercial membranes. The TFCs also display unprecedented properties for desalination applications with performance located far above the current water permeance/sodium chloride rejection trendline. The strategy of using highly contorted triptycene building blocks with well-defined interconnected internal free volume elements establishes a scalable, generalized approach to fabricate highly selective, submicroporous TFC membranes for a wide variety of challenging energy-intensive fluid separations.     

Mathematical Modeling of Two-Stage Extraction Kinetics using the Single Drop Technique

This paper focuses on the mathematical modeling of the two-stage extraction using the single drop technique. Two stages of extraction are being considered: the drop formation step, where dimensions of the drop are highly dependent on time, and the drop travel step, during which the drops size and dimensions are assumed constant. Models for both extraction steps are derived and the combined model is proposed. Two-stage and one-stage models of extraction are compared. Errors occuring when considering only the travel stage of the single drop extraction have been calculated and their dependencies on various extraction parameters have been determined. The analysis of the combined two-stage model has proven that the travel-stage-only model generates significant errors during the determination of reaction rate constants when the drop formation time is significant in relation to the whole extraction time. Thus, the two-stage model should be used to reduce originating errors.     

Chemical structure of poly(β‐cyclodextrin‐co‐citric acid)

We synthesized water‐insoluble polymers, poly(β‐cyclodextrin‐co‐citric acid)s, by heating a mixture of citric acid, cyclodextrin (CD), and Na₂HPO₄ as a catalyst with a 6 : 1 : 2 molar ratio at 160, 170, and 180°C for 10 and 20 min. The chemical composition of the polyesters was determined by high pressure liquid chromatography (HPLC) analysis of the polymer hydrolysates. The crosslinking mechanisms and thermal degradation of the polymers were also investigated. The polyesters contained 30–35% citric acid, 1–4% unsaturated carboxylic acids (i.e., itaconic, cis‐aconitic, trans‐aconitic, and mesaconic acids), and 60–70% CD, whereas about 40% of them were able to form inclusion complexes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Steganalysis of transcoding steganography

Transcoding steganography (TranSteg) is a fairly new IP telephony steganographic method that functions by compressing overt (voice) data to make space for the steganogram by means of transcoding. It offers high steganographic bandwidth, retains good voice quality, and is generally harder to detect than other existing VoIP steganographic methods. In TranSteg, after the steganogram reaches the receiver, the hidden information is extracted, and the speech data is practically restored to what was originally sent. This is a huge advantage compared with other existing VoIP steganographic methods, where the hidden data can be extracted and removed, but the original data cannot be restored because it was previously erased due to a hidden data insertion process. In this paper, we address the issue of steganalysis of TranSteg. Various TranSteg scenarios and possibilities of warden(s) localization are analyzed with regards to the TranSteg detection. A novel steganalysis method based on Gaussian mixture models and mel-frequency cepstral coefficients was developed and tested for various overt/covert codec pairs in a single warden scenario with double transcoding. The proposed method allowed for efficient detection of some codec pairs (e.g., G.711/G.729), while some others remained more resistant to detection (e.g., iLBC/AMR).     

Design of a device for precision shaping of grinding wheel macro- and micro-geometry

The selected modifications to the construction of grinding wheels were described which facilitate an increase in the material removal rate (grinding wheels with conic chamfer and grinding wheels with microdiscontinuities on the active surface). Using these background details, a suggested thesis was put forward regarding the need to develop a device which will allow for the shaping of the macrogeometry of the grinding wheel (cylindrical and conical surfaces) and the microdiscontinuities within the dressing operation simultaneously. The device was presented and prepared in two functional variants (horizontal and vertical mounting of the motor), then a prototype was described. An example of the grinding wheel active surface, shaped by using this device, was also presented. The theoretical analysis and experimental verification performed determine that the error of shaping the conic chamfer angle within the range of 0–1.5°, using the developed device, is approximately ±3%.     

Behavior of composite beams prestressed with external tendons: Experimental study

The paper deals with the failure mechanisms and behavior of composite steel-concrete beams prestressed with external tendons and subjected to positive bending. Experimental tests were carried out on beams with straight and draped tendons as well as on a non-prestressed beam. Six simply supported beams subjected to a positive static bending moment were tested up to failure. The influence of shear connection flexibility was taken into account and slip was measured along the beam axis. Concurrently, push-out specimens were made and tested to determine shear force vs. slip curves. It was found that at the same eccentricity of tendons (draped or straight without saddle points) the tendon shape has no significant effect on the behavior and ultimate resistance of composite steel-concrete beams. It is also shown that steel-concrete bond cohesion can significantly influence the behavior of the shear connection in composite beams. This influence is comparable with the design shear resistance of a single stud connector.     

Load capacity and deflection of fire-resistant steel beams

The methodology of defining safety of constructions in fire has not yet been sufficiently verified and agreed upon. This paper includes calculation results for steel beams, which prove that the ultimate load-bearing capacity predicted by plastic design theory, which is valid in engineering calculations, is not sufficient for determining the critical temperature. The reason is that this temperature tends to be limited in some cases by large deflections of beams in fire.