The influence of economic parameters on the optimal values of the design variables of a combined cycle plant

This paper presents the analysis of the influence of fuel price variation on the optimal values of the design variables of the steam part of a combined cycle plant. The investigated system was a power plant with a triple-pressure heat recovery steam generator and extraction-condensation steam turbine. Fourteen design variables for the steam part were identified. The variables that were optimised were the pressure levels of the working medium in the steam part of the system, and characteristic differences of temperatures in the heat recovery steam generator. Thanks to the development of an optimising programme, based on the genetic algorithms theory, it was possible to find an optimal solution. The indices of economic efficiency, in the form of the break-even price of electricity, were chosen as the objective function in the optimisations. The results of economic optimisations were compared with the results of the optimisation, where the electric efficiency was the objective function. This paper includes an analysis of the sensitivity of the economic objective function to failures in the adherence of the optimal values of decision variables. This analysis allowed the selection of variables such that a failure results in the highest increase of the break-even price of electricity.     

Characterization of the surface layers formed on titanium by plasma electrolytic oxidation

This paper is concerned with the surface modification of titanium by the PEO method (plasma electrolytic oxidation) in the solutions which contain Ca, P, Si and Na. The chemical composition of the thus formed surface layers was examined by XPS and EDS. The morphology of the surface was observed by SEM. The phase composition was determined by X-ray diffraction (XRD). The adhesive strength of the oxide layers was evaluated by the scratch-test. The corrosion resistance was determined in a simulated body fluid (SBF) at a temperature of 37 °C by electrochemical methods for various exposure times.The oxide layers obtained were porous and enriched with Ca, P, Si and Na and their properties depended on the electrolyte solution and the parameters of the oxidation process. The results of the electrochemical examinations show that the surface modification by PEO does not worsen the corrosion resistance of titanium after a 13 h exposure in SBF. The electrochemical impedance spectroscopy (EIS) results indicate that the surface layers have a complex structure and that their electric properties undergo changes during long-term exposures in SBF.     

Acoustic emission for detecting deterioration of capacitors under aging

There is continuous pressure on production cost reduction of foil-based capacitors, widely used in domestic appliance. Therefore, investigation of the deterioration mechanisms within capacitors is important to reduce their production costs at maintained reliability. These mechanisms were observed in two capacitors batches of classes Y2 (27 nF) and X2 (470 nF). An acoustic emission signal was observed when the capacitors were polarized by excessive voltage. This signal is induced by partial discharges that can lead to capacitor destruction. Next, the capacitors were aged at elevated temperature and also in presence of excessive polarization. We conclude that the acoustic emission signal can predict deterioration of dielectric insulation resistance in capacitors of class Y2. The observed destruction of capacitor of class X2 is caused mainly by detachment of the sprayed metalized contacts that is induced by overheating during partial discharges sparking.     

Thermal properties of poly(pivalolactone)

Polypivalolactone (PPVL) is a highly crystalline polyester formed either by nucleophilic or electrophilic ring-opening polymerization of 2,2-dimethyl-β-propiolactone, commonly known as pivalolactone (PVL). The thermal properties and crystallization kinetics of the polymer formed under reaction injection molding (RIM) conditions were studied. The crystallization kinetics of PPVL were measured using differential scanning calorimetry (DSC), and Avrami theory was used to interpret the bulk crystallization kinetics. A comparison was made with commercially prepared PPVL. The kinetics data indicate laboratory prepared PPVL, which is of lower molecular weight, has similar crystallization rates compared to the higher molecular weight commercial material. The kinetics data also indicate the rate of crystallization is relatively rapid overall for PPVL, with low activation energies of crystallization. The calorimetric studies also utilized DSC and simultaneous ther-mogravimetric analysis/differential scanning calorimetry (TGA/DSC). Thermal analysis showed a clear difference in melting behavior between high and low molecular weight material, possibly a reflection of the presence of the α and γ-crystal forms of the polymer.     

s-Wave vs.d -Wave Superconductivity in the Two-Dimensional Hubbard Model

The anisotropic superconductivity has been considered in the two-dimensional Hubbard model. We allow for on and off-site intralayer Cooper pairs. Interlayer momentum-conserving Josephson tunneling which couples adjacent layers has been taken into account. The meanfield solution for the superconducting transition temperature demonstrates the competition between local Coulomb repulsion and interlayer tunneling in thes-wave channel. This competition leads to the mixedsd superconducting state at low doping. We also demonstrate thatc-phonon-assisted transitions between intra and interlayer states can effectively give rise to momentum-conserving Josephson tunneling.     

DRYING OF WASTE SLUDGES IN A FLUIDIZED BED DRYER WITH A MIXER

Sludge wastes are a very attractive source of many valuable compounds such as nitrogen, phosphorus and organic matter. One of the interesting methods of sludge utilization is dewatering and drying. In this paper some problems of drying of two types of sludge wastes of different form and origin are presented. One of the sludges—a brewery by-product— contains spent grain suspension of brewer's yeast and diatomaceous earth. The second one is a by-product of a biotechnological process which contains mainly lime, protein, many microelements and some microorganisms. Moisture content of both sludges is about 65-70% w/w. The laboratory experiments of sludge drying in the fluidized bed dryer with a mixer, fluidized bed hydrodynamics, and the effects and advantages of sludge drying are shown.     

Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

Investigations of bilayer and trilayer Al₂O₃/SiO₂ and Al₂O₃/HfO₂/SiO₂ antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10^?3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al₂O₃, 0.6 nm ? 0.8 nm/s for HfO₂ and 0.6 nm/s for SiO₂. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al₂O₃/SiO₂ and 78 nm/156 nm/78 nm for Al₂O₃/HfO₂/SiO₂. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.     

Support for argument structures review and assessment

Argument structures are commonly used to develop and present cases for safety, security and for other properties of systems. Such structures tend to grow excessively, which causes problems with their review and assessment. Two issues are of particular interest: (1) systematic and explicit assessment of the compelling power of an argument, and (2) communication of the result of such an assessment to relevant recipients. The paper presents a solution to these problems. The method of Visual Assessment of Arguments (VAA), being this solution, is based on the Dempster-Shafer theory of evidence applied to the assessment of the strength of arguments, and a visual mechanism of issuing and presenting assessments, supported by the so-called opinion triangle. In the paper we explain theoretical grounding for the method and provide guidance on its application. The results of some validation experiments are also presented.