A generalized fuzzy Petri net model

The paper proposes a new model of Petri nets based on the use of logic based neurons. In contrast to the existing generalizations, this approach is aimed at neural-type modeling of the entire concept with a full exploitation of the learning capabilities of the processing units being used there. The places and transitions of the net are represented by OR and AND-type and DOMINANCE neurons, respectively. A correspondence between this model and the previous two-valued counterpart is also revealed. The learning aspects associated with the nets are investigated     

Synthesis and properties of peroxy derivatives of epoxy resins based on Bisphenol A: Effects of the presence of boron trifluoride ethereate

Oligomers containing peroxy groups have been synthesized on the basis of epoxides reacting with tert–butylhydroperoxide in the presence of boron trifluoride etherate. Dependence of reaction rates upon the quantity of catalyst, temperature and also nature of hydroperoxide has been investigated: A kinetic equation for the process has been formulated and also a kinetic scheme for the reaction taking into account the presence of boron trifluoride etherate is proposed. Structures of the synthesized peroxy oligomers have been confirmed by IR- and NMR-spectroscopy. The reaction initiating properties of the oligomers so synthesized were studied using as the example the styrene polymerization reaction. Electronic Publication     

Mechanical improvement of concrete by irradiated polypropylene fibers

Fiber reinforced concrete (FRC) contains fibers physically mixed with gravel, sand, cement, and water. So far, adequate mechanical performance of FRC has been obtained at high cost and using complex technologies; important here is the geometry and surface characteristics of the polymers. We have modified polymeric‐fiber surfaces by using gamma radiation. Irradiated polypropylene (PP) fibers were submitted to 0, 5, 10, 50, and 100 kGy of gamma irradiation dosages. First, tensile strength of PP fibers was evaluated, and then fibers blended at 0, 1.0, 1.5, and 2.0% in volume with Portland cement, gravel, sand, and water. The highest values of compressive strength were obtained with irradiated‐fibers at 10 kGy and 1.5% in volume of fiber. The result is 101 MPa, as compared to 35 MPa for simple concrete without fibers. POLYM. ENG. SCI., 45:1426–1431, 2005. © 2005 Society of Plastics Engineers     

A study of uncertain state estimation

In this paper, we present results of uncertain state estimation of systems that are monitored with limited accuracy. For these systems, the representation of state uncertainty as confidence intervals offers significant advantages over the more traditional approaches with probabilistic representation of noise. While the filtered-white-Gaussian noise model can be defined on grounds of mathematical convenience, its use is necessarily coupled with a hope that an estimator with good properties in idealised noise will still perform well in real noise. In this study we propose a more realistic approach of matching the noise representation to the extent of prior knowledge. Both interval and ellipsoidal representation of noise illustrate the principle of keeping the noise model simple while allowing for iterative refinement of the noise as we proceed. We evaluate one nonlinear and three linear state estimation technique both in terms of computational efficiency and the cardinality of the state uncertainty sets. The techniques are illustrated on a synthetic and a real-life system.     

An optimization of allocation of information granularity in the interpretation of data structures: toward granular fuzzy clustering

Clustering forms one of the most visible conceptual and algorithmic framework of developing information granules. In spite of the algorithm being used, the representation of information granules-clusters is predominantly numeric (coming in the form of prototypes, partition matrices, dendrograms, etc.). In this paper, we consider a concept of granular prototypes that generalizes the numeric representation of the clusters and, in this way, helps capture more details about the data structure. By invoking the granulation-degranulation scheme, we design granular prototypes being reflective of the structure of data to a higher extent than the representation that is provided by their numeric counterparts (prototypes). The design is formulated as an optimization problem, which is guided by the coverage criterion, meaning that we maximize the number of data for which their granular realization includes the original data. The granularity of the prototypes themselves is treated as an important design asset; hence, its allocation to the individual prototypes is optimized so that the coverage criterion becomes maximized. With this regard, several schemes of optimal allocation of information granularity are investigated, where interval-valued prototypes are formed around the already produced numeric representatives. Experimental studies are provided in which the design of granular prototypes of interval format is discussed and characterized.     

Effects of carbon black on tribology of blends of poly(vinylidene fluoride) with irradiated and non-irradiated ultrahigh molecular weight polyethylene

Friction and wear resistance are two vital tribological properties of polymer-based materials but optimization of both is rarely attempted. We have investigated blends of 70 wt% poly(vinylidene fluoride) (PVDF)+30% ultra high molecular weight polyethylene, the latter either un-irradiated or else γ-irradiated. Each sample contained varying amounts of carbon black (CB) and also had a varied degree of crosslinking and irradiation dose. We have determined static and dynamic friction, scratch resistance, and sliding wear in multiple scratching tests. Effects of the irradiation dose and CB concentration have been quantified. The electric conductivity threshold is reflected in a drop of static friction; formation of a continuous phase of the lubricant affects tribology as well as electrical properties—both for irradiated and for un-irradiated samples. The scratch resistance as represented by the residual (healing) depth is affected by crosslinking, by the stage at which irradiation is applied (before or after blending) and by CB addition. Crosslinking by moderate amounts of irradiation provides shallower residual depths while higher doses cause adverse results. Similarly, the CB lubricant can either improve or worsen the scratch resistance. A combination of both approaches produces either better or else worse results than crosslinking alone. Lower friction seems accompanied by higher scratch resistance. A combination of a specific irradiation dose and an optimized CB concentration lowers the sliding wear significantly. Strain hardening in sliding wear determination takes place for all materials studied, irrespective of the extent or radiation-induced crosslinking and of the presence and concentration of carbon black.     

Morphology and thermal properties of two polymethacrylates modified by a polymer liquid crystal

We have studied blends of a polymer liquid crystal (PLC) with poly(cyclohexylethyl methacrylate) (PCHEMA) or poly(cyclohexylpropyl methacrylate) (PCHPMA). The PLC is PET/0.6PHB where PET = poly(ethylene terephthalate), PHB = p-hydroxybenzoic acid and 0.6 is the mole fraction of the latter in the copolymer. The microstructure was studied by scanning electron microscopy (SEM). PCHEMA + PLC (20 wt% of the latter, blend E) has a fine texture with LC islands evenly distributed in the matrix and good adhesion between the phases resulting from their partial miscibility. The PCHPMA + PLC (20 wt% of the latter, blend P) shows only limited compatibility. The SEM results are confirmed by values of the glass transition temperatures T_g determined via thermal mechanical analysis. The T_g value of the blend E is shifted towards the T_g of PLC; T_g of blend P is practically equal to that of PCHPMA. The linear isobaric expansivity α_L values for both blends are lower than the respective values for pure PCHPMA and PCHEMA. Thermal stabilities of the blends determined by thermogravimetry are also better than those of pure polymethacrylates. The temperature of 50% weight degradation for blend E is higher than that for pure PCHEMA by more than 60 K Copyright © 2004 Society of Chemical Industry