Hydroprocesssing of light gas oil — rape oil mixtures

Two series of experiments of hydroprocessing of light gas oil - rape oil mixtures were carried out. The reactor feed was composed of raw material: first series — 10 wt.% rape oil and 90 wt.% of diesel oil; second series — 20 wt.% rape oil and 80 wt.% of diesel oil.     

Thermal-Diffusivity Dependence on Temperature of Gadolinium Calcium Oxoborate Single Crystals

Thermal diffusivities of pure and doped gadolinium calcium oxoborate (GdCOB) single crystals were measured as a function of the temperature along optical indicatrix axes X, Y, and Z. Three GdCOB samples were investigated, chemically pure single crystal, the one doped with 4 at% of Nd and the next one doped with 7 at% of Yb. Measurements were carried out for temperature range 40 °C to 300 °C. Determination of the thermal diffusivity based on an analysis of thermal wave propagation in the sample. For a detection of temperature disturbance propagating in the sample the mirage effect was used. Obtained results show that the thermal diffusivity decreases with the increase of sample temperature for all investigated crystals. The GdCOB single crystals reveal a strong anisotropy. The thermal diffusivity along Y direction has the highest value while values obtained in X and Z axes are much lower. Dopants cause decrease in the thermal diffusivity for all investigated directions.     

Structural and electrical properties of Cr-doped SrTiO3 porous materials

Series of single-phase materials with assumed formula SrTi_1?xCr_xO₃ (where x = 0, 1, 4, 6 mol.%) were obtained by sol-gel method. The structure and microstructure of materials were characterised by X-ray diffraction and scanning electron microscopy methods. Moreover, the study of electrical properties and evaluation of chemical stability in CO₂/H₂O atmosphere was performed by electrochemical impedance spectroscopy and thermogravimery methods, respectively. The possibility of participation of Cr-doped strontium titanate in oxidation–reduction processes was analysed by temperature-programed reduction (TPR) and temperature-programed oxidation (TPOx) measurements. The changes of lattice parameters together with XPS analysis, the Seebeck coefficient measurements results and TPR profiles obtained for SrTi_1?xCr_xO₃ materials prove the presence of chromium on +3 and +6 oxidation stages. Thus, chromium can be treated as both acceptor- and donor-type dopant in the SrTiO₃ structure. The Cr³⁺/Cr⁶⁺ ratio strongly affects the electrical properties, as the change of conduction mechanism was observed. The results of performed stability test clearly indicate that incorporation of chromium into SrTiO₃ structure results with decrease of chemical stability in CO₂ atmosphere.     

Influence of addition of green tea and green coffee extracts on the properties of fine yeast pastry fried products

This study investigated the influence of antioxidants of green tea aqueous extract (GTE) and green coffee aqueous extract (GCE) in concentrations of 0.25, 0.5 and 1 g·100 g^? 1 on the nutritional properties of fine yeast pastry fried products such as donuts. Yeast donuts were made according to the traditional processing technology. In fried donuts physical properties (water activity, pH, hardness and color with the use of instrumental methods) as well as sensory properties were established. Moreover, quality of fat extracted from donuts (composition of fatty acids and peroxide value), content of acrylamide, composition of polyphenols and antioxidant activity were analyzed. Obtained extracts of GTE and GCE contained 26 and 41% of polyphenols, respectively, and the degree of polyphenol degradation during production of donuts was less when the dilution in dough was greater. Both tests indicated that the highest antioxidant activity had donuts with the highest analyzed addition of extract, however depending on the applied test or GTE or GCE had better antioxidant properties. Fatty acid composition was the most beneficial when the addition of GTE and GCE was on a level of 0.25 and 0.5 g·100 g^? 1, respectively. In fried donuts relatively low amounts of acrylamide were obtained, amounting to 18–46 μg·kg^? 1. Only the lowest addition of GTE and the highest addition of GCE caused an increase of acrylamide content in donuts, while all other levels of added extracts caused a decrease in the content of formed acrylamide.     

Selectivity enhancement in the catalytic heterogeneous hydrogenation of limonene in supercritical carbon dioxide by an ionic liquid

Ionic liquids as coated catalysts or additives tremendously alter the selectivity pattern of the heterogeneous solid catalyst in the selective hydrogenation of limonene. The conventional monometallic ruthenium over alumina catalyst combined with an ionic liquid enables the one-pot synthesis of the intermediate p-menthene through limonene hydrogenation in supercritical carbon dioxide. Among eight screened imidazolium ILs, [C₁₀mim]NTf₂ was employed as additive, or as the coating agent of ruthenium catalyst in the reaction under supercritical conditions.The coating of the heterogeneous catalyst allows the selective production of p-menthene and increases the conversion level of limonene (>99%) compared to the conversion of limonene in the reaction carried out in the presence of an ionic liquid as an additive. Results of the catalyst recycling indicate that there is no depletion of catalyst reactivity even after four successive cycles of operation under the studied reaction conditions. Further hydrogenation of p-menthene is strongly inhibited by employing an ionic liquid. The solubility of limonene or p-menthene in an ionic liquid governs the selective hydrogenation of limonene towards p-menthene.     

Explicit Nonlinear Predictive Control of a Distillation Column Based on Neural Models

A nonlinear Model Predictive Control (MPC) algorithm and its application to a distillation column are described. The algorithm uses a neural model of the process that is linearized online around the current operating point. The algorithm is computationally efficient because the control policy is calculated explicitly without any optimization. The algorithm requires online repetition of a matrix decomposition task and the solution of linear equations. The obtained solution is projected onto the admissible set of constraints imposed on the magnitude and the increment of the manipulated variables. For the distillation column considered, the control accuracy is comparable not only to that obtained in MPC with online linearization and quadratic programming but also to that obtained in nonlinear MPC, which is based on full nonlinear optimization repeated at each sampling instant.     

Analysis of three-phase chopper circuits controlled by asymmetrical firing of thyristors

Contents Using thyristor and thyristor-diode a.c. choppers causes distortion of currents and voltages in electrical power networks. In this paper the currents in three-phase, three-wire circuits with thyristor and thyristor-diode a.c. choppers are analysed, making allowances for asymmetrical phase-angle triggering. The computation results of the extinction angles versus firing angles, phase shift angles of the load and degree of asymmetry are shown. The d.c. and harmonic components of the current waveforms were calculated by applying Fourier analysis. The computation results of the magnitudes, which are characteristic of deformed waveforms are also presented.

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Übersicht Der Einsatz von Thyristoren und Thyristordioden verursacht Verzerrungen von Strömen und Spannungen in elektrischen Versorgungsnetzen. In diesem Beitrag werden Stromverläufe in Drehstromnetzen unter Berücksichtigung unsymmetrischer Ansteuerung durch Thyristoren analysiert. Die errechneten Abhängigkeiten des Löschwinkels von der Phasenlage der Last und der Unsymmetrie der Ansteuerung werden dargestellt. Mit Hilfe der Fourieranalyse werden Gleichstromanteil und Oberschwingungen der Ströme ermittelt. Berechnet und dargestellt werden auch andere Größen, die für nichtlinear verzerrte Vorgänge charakteristisch sind.

     

Optimizing Grid-Based Workflow Execution

Large-scale applications can be expressed as a set of tasks with data dependencies between them, also known as application workflows. Due to the scale and data processing requirements of these applications, they require Grid computing and storage resources. So far, the focus has been on developing easy to use interfaces for composing these workflows and finding an optimal mapping of tasks in the workflow to the Grid resources in order to minimize the completion time of the application. After this mapping is done, a workflow execution engine is required to run the workflow over the mapped resources. In this paper, we show that the performance of the workflow execution engine in executing the workflow can also be a critical factor in determining the workflow completion time. Using Condor as the workflow execution engine, we examine the various factors that affect the completion time of a fine granularity astronomy workflow. We show that changing the system parameters that influence these factors and restructuring the workflow can drastically reduce the completion time of this class of workflows. We also examine the effect on the optimizations developed for the astronomy application on a coarser granularity biology application. We were able to reduce the completion time of the Montage and the Tomography application workflows by 90% and 50%, respectively.     

Dosimetry of BNCT beams with novel thermoluminescent detectors

In the dosimetry of boron neutron capture therapy (BNCT) beams, thermoluminescent (TL) detectors are typically applied in phantom measurements to determine the spatial distribution of the gamma ray and neutron dose. Pairs of 6LiF and 7LiF are applied to discriminate between the thermal neutron and gamma ray field components, exploiting the high cross section for (n,alpha) reaction of 6Li. At the Institute of Nuclear Physics (INP) in Kraków (Poland) a prototype TL-based measuring set has been constructed and tested. This set consists of a miniature TL detector (of 2 mm diameter and 0.4 mm thickness) placed inside a miniature container made of non-thermoluminescent 6LiF. The outer dimensions of the set are 4.5 mm diameter and 1.4 mm thickness, enabling its application in place of a thermoluminescence dosemeter pellet in typical phantoms. The detector sets were tested in the BNCT beam of the Studsvik reactor. By exploiting the ratio of TL signals of the unshielded and shielded detectors, it was possible to estimate the contributions of the thermal and epithermal components of the neutron field.