Digital Filter Design Using Computer Algebra Systems

Digital filter design can be performed very efficiently using modern computer tools. The drawback of the numeric-based tools is that they usually generate a tremendous amount of numeric data, and the user might easily lose insight into the phenomenon being investigated. The computer algebra systems successfully overcome some problems encountered in the traditional numeric-only approach. In this paper, we introduce an original approach to algorithm development and digital filter design using a computer algebra system. The main result of the paper is the development of an algorithm for an infinite impulse response (IIR) filter design that, theoretically, is impossible to be implemented using the traditional approach. We present a step-by-step procedure which includes derivations of closed-form expressions for (1) the transfer functions of the implemented digital filter which contains the algebraic loop; (2) the closed-form expression for computing the number of requested iteration steps; and (3) the error function representing the difference of the output sample values of the new filter and that of the conventional filter. We demonstrate how one can use some already-known multiplierless digital filter as a start-up filter to design a new digital filter whose passband edge frequency can be simply moved by using a single parameter. As a result, we obtain a multiplierless IIR filter, which belongs to the family of low-power digital filters where multipliers are replaced with a small number of adders and shifters.     

Assessment of changes in desorption mechanism of MgH2 after ion bombardment induced destabilization

This paper deals with non-isothermal kinetics models of hydrogen desorption from MgH₂ altered by ion bombardment and stresses the importance of the MgH₂ surface during its decomposition. In the case of argon-irradiated samples, where defects are induced in the near-surface region, the Avrami Erofeev mechanism with parameter n = 2 can be adopted while in the case of boron-irradiated samples, where defects are created deeper in the bulk, the desorption mechanism is the same with n = 3. The difference is possibly related to the concentration and good dispersion of defects in near-surface region in the samples.     

Chitosan,itaconic acid and poly(vinyl alcohol) hybrid polymer networks of high degree of swelling and good mechanical strength

Chitosan is a biodegradable, non‐toxic, biocompatible polymer convenient for use in drug delivery. In this study, hybrid polymeric networks (HPNs) based on chitosan, itaconic acid and poly(vinyl alcohol) (PVA) were prepared and characterized. Chitosan was dissolved in itaconic acid in order to obtain ionic crosslinking with the dicarboxylic acid. In the second step, this chitosan/itaconic acid network was mixed with PVA and chemically crosslinked with glutaraldehyde. The chitosan/itaconic acid ratio was kept constant, while the concentrations of PVA and glutaraldehyde were varied. All samples were characterized using swelling studies, dynamic mechanical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, X‐ray diffraction and scanning electron microscopy. The equilibrium degrees of swelling obtained for the HPNs were higher than most of the values reported for chitosan hydrogels obtained by dissolving chitosan in acetic acid or HCl aqueous solutions. This method of synthesis also resulted in hydrogels with better mechanical properties and thermal stability. By changing the PVA content and the degree of crosslinking, it is possible to finely tune the properties of the HPNs, which could make them suitable as potential matrices in controlled drug delivery. Copyright © 2010 Society of Chemical Industry     

Effect of Storage in a Low Oxygen Gas Atmosphere on Colour and Sensory Properties of Pork Loins

The objective of this study was to examine the quality characteristics of packaging materials and packaging units, and the viability and acceptability of the colour and sensorial properties of fresh pork meat during storage in low oxygen and high carbon dioxide modified atmosphere packaging up to 16 days at two temperatures (0°C and 4°C), as well as the sensorial properties of cooked meat. Packaging materials had good mechanical and barrier properties and were suitable for packaging in selected atmosphere. The concentration of oxygen during the whole storage period was less than 0.5% at both temperatures. The proportion of red colour (a*) was successfully maintained although the colour was slightly darker (L*) and the sensory value was lower when evaluated at the end of the storage period. Based on the obtained results and discussion, it can be concluded that samples packaged in a modified atmosphere with 40% CO₂ and 60% N₂ can be stored at 0°C for 15 days and at 4°C for 10 days. Samples had a good sensory quality until the 16th day, with the best results achieved on the 7th day. Copyright © 2013 John Wiley & Sons, Ltd.     

Adsorption of n-Alkanes on Silicon Nitride Nanopowder

Adsorption properties of silicon nitride beads were investigated by the inverse gas chromatography (IGC) method. Silicon nitride beads were obtained from a commercial nanopowder. Retentions of n -pentane, n -hexane, n -heptane, and n -octane were measured in the temperature range from 343 to 383 K, at zero surface coverage. Surface partition coefficients and the related thermodynamic functions (standard free energy changes, standard state enthalpy, and entropy changes) of the adsorption process were determined. The dispersive component of the surface free energy of silicon nitride, at investigated temperatures, was also calculated.     

The Formal Specification of Level la of GKS

In this paper the formal specification of a part of level la of GKS is given in the algebraic specification language OBJ. It shows that it is possible to produce a formal specification of a substantial part of GKS which is of manageable size and complexity specifying the appropriate level of abstraction of the system and using a suitable formal technique.     

Intrinsic Equilibrium Constants of beta;-Silicon Carbide Obtained from Surface Charge Data

The surface charge behavior of β-SiC in KNO₃ electrolyte solutions is reported as a function of pH and ionic strength. The surface charge densities were obtained by potentiometric titration, and the point of zero charge of β-SiC was determined by the batch equilibration method. The intrinsic equilibrium constants, describing association-dissociation of surface groups, were calculated using the site-binding model.     

Effects of anthropogenic influences on the trophic status of two water supply reservoirs in Serbia

The results of hydrobiological investigations of Grošnica and Gruža Reservoirs near the city of Kragujevac in Serbia indicated differences in their trophic status. Although considerably younger than Grošnica Reservoir, Gruža Reservoir manifests all the signs of accelerated eutrophication. Primary and secondary plankton productivity is significantly greater in Gruža Reservoir, as is macrophyte production. Accelerated eutrophication also is indicated with the results of an ecological analysis. The manifested differences can be attributed mainly to the greater human influences, as well as the unfavourable morphometric characteristics of Gruža Reservoir, compared to Grošnica Reservoir.     

Effect of Starter Culture Addition and Processing Method on Proteolysis and Texture Profile of Traditional Dry-Fermented Sausage Petrovská klobása

Proteolysis and texture profile of Petrovská klobása, made with addition of starter culture, were investigated during the ripening in different conditions (traditional versus industrial). Due to intensive degradation of myofibrillar proteins, significant increases of non-protein nitrogen and free amino acids nitrogen contents were registered in all samples. Similar proteolytic changes were found in both starter and non-starter sausages, but were more pronounced in samples ripened in industrial room. In relation to ripening conditions hardness and chewiness differed significantly, while starter culture had significant effect only on hardness of sausages processed in industrial room.