Aims and methods in non-isothermal reaction kinetics

The majority of the works dealing with non-isothermal kinetics assumes only one kinetic differential equation, uses linearization techniques and do not check the fit between the simulated and the experimental data. It is not clear from the literature why we need kinetic evaluations at all in this field. Due to this controversial situation, the author has outlined his views on the aims and methods of the non-isothermal kinetics in this paper. Accordingly, the goal of the kinetic evaluation is to obtain better, more informative results from the experiments. If realistic models are used, numerous unknown parameters have to be determined during the evaluation. Since the most important errors of thermal analysis are not random, the laws of the mathematical statistics do not offer means to find the best set of model parameters. Nevertheless, the simultaneous evaluation of a series of thermoanalytical experiments by the method of least squares aims directly at the description of the sample behavior in a wide range of experimental conditions and helps the determination of a large number of unknown parameters. The outlined considerations are supported by examples from the work of the author and his coworkers. As a comparison, a statistical survey is given on those papers that were published in journals specialized for thermal analysis, thermochemistry and pyrolysis in 2006 and contained the term “kinetic” or “kinetics” in their titles

Hungary's banking sector: achievements and challenges

Hungary is generally considered one of the best performing transition countries, having been successful in achieving macroeconomic stabilisation and in creating a market-driven economic system (see, for instance, Fischer and Sahay, 2000; and Weder, 2001). In terms of financial sector reforms, the country is also considered in the advanced league (Bokros, 2001). While we agree to this assessment, it is also true that the degree of monetisation and bank intermediation in the Hungarian economy is surprisingly low, and this despite Hungarys head start in setting a market-driven banking sector. More specifically, in contrast to many other Central and Eastern European Countries (CEECs), Hungary already had a two-tier banking system when the Berlin Wall came down. While the nature of activities that banks could pursue was strictly regulated - limiting competition between banks and resulting in a segmentation of the market - things changed in 1989 when commercial banks - originally confined to corporate customers - were admitted to the retail market. At the same time retail financial institutions were given commercial banking licenses

Biomassza tüzelőanyagok optimális hasznosítását elősegítő alapkutatás termikus analízis segítségével = Fundamental research by thermal analysis for the optimal utilization of biomass fuels

Kísérleti biomassza ültetvények termékeit, különböző fafajtákat, valamint biomasszából készült faszenet vizsgáltunk termogravimetrai, termogravimetria -tömegspektrometriai valamint pirolízis-gázkromatográfia-tömegspektrometriai mérések segítségével. A munka a hőbomlás valamint a kontrollált hőprogram mellett végzett égetés folyamatainak mélyebb megismerésére irányult. A folyamatokat befolyásoló tényezők közül az alábbiak szerepéről nyertünk az eddigieknél részletesebb ismereteket: a lignin hőbomlása; az extrahálható komponensek szerepe; továbbá a fakéreg szerepe a fakérget is tartalmazó biomassza anyagok termikus tulajdonságaiban. Részletes reakciókinetikai leírásmódokat dolgoztunk ki, melyeket nagyobb méréssorozatok egyidejű, legkisebb négyzetek elve szerinti kiértékelésére alapoztunk. A reakciókinetikai kiértékelés és modellezés a lejátszódó folyamatok pontosabb megértését szolgálta. Emellett segített az egyes minták közötti hasonlóságok és különbségek felderítésében is. | We studied the products of experimental biomass plantations as well as various wood samples and charcoal produced from biomass by thermogravimetry, thermogravimetry - mass spectrometry and pyrolysis - gas chromatograpy - mass spectrometry. A deeper insight was obtained into the partial processes of devolatilization and temperature-programmed combustion. We clarified several aspects of lignin devolatilization and the role of the extractives and bark in the thermal behavior of biomass samples. Detailed kinetic modeling was carried out. It was based on the least squares evaluation of larger series of experiments and helped in a more accurate understanding of the processes. The kinetic modeling helped also in discerning differences and observing similarities between the various biomass samples

Computer processing of thermogravimetric - mass spectrometric and high pressure thermogravimetric data. Part 1. Smoothing and differentiation

High quality data smoothing is frequently required in the thermal analysis. Though the mathematical methods for smoothing are well known, the selection of the proper smoothing parameters cannot be based on statistical checks alone in thermal analysis. Many times a compromise must be found between the effective removal of the various experimental error components and the distortion of the curves by too strong smoothing. The following topics are discussed from a practical point of view: (i) the determination of the derivative thermogravimetric (DTG) curves at low sample masses; (ii) the elimination of the noise and flutter from the results of high-pressure TG experiments; (iii) the evaluation of the noisy, low intensity mass spectrometric signals arising from the minor volatile products of decomposition or oxidation. The performance of the methods is shown in two applications: (1) Evaluation 0.25 – 0.5 mg mass loss steps in high-pressure thermogravimetry; (2) Study of NOx formation by atmospheric pressure thermogravimetry – mass spectrometry during the temperature programmed combustion of 0.4 mg coal char. Keywords: Thermogravimetry – mass spectrometry, high-pressure thermogravimetry, smoothing, differentiation, DT

Comparison of temperature programmed char combustion in CO2 - O2 and Ar - O2 mixtures at elevated pressure

A pressurized thermobalance (TGA) system was built. The role of CO2 was studied in the controlled temperature combustion under pressurized conditions. Particular care was taken to employ low sample masses in thin layers, to avoid self-heating phenomena and ensure kinetic control. It was found that a CO2 partial pressure of 0.57MPa at a 0.6 MPa total pressure had no effect on the overall reaction rate of a temperature programmed combustion. KEYWORDS: High pressure thermogravimetry, char, combustion, effect of carbon dioxid

Sticky price inflation index: An alternative core inflation measure

We show that in both time-dependent and state-dependent sticky price models, prices of sticky price products (i.e. whose price changes rarely) contain more information about medium term inflation developments than those of flexible price products (i.e. whose price changes frequently). We do this by establishing a novel measure for the extent of forwardlookingness of newly set prices, and showing that it is at least 60% when the monthly price change frequency is less than 15%. This result is robust across various sticky price models. On the empirical front, we show that the Hungarian sticky price inflation index indeed has a forward-looking component, as it has favorable inflation forecasting properties on the policy horizon of 1-2 years to alternative inflation indicators (including core inflation). Both theoretical and empirical results suggest that the sticky price inflation index is a useful indicator for inflation targeting central banks

Mass Flux Distribution Measurements and Visualizations of a Fluid Sheet Generated by a Partially Immersed Dip-Lubricated Gear

A simplified model of gearbox lubrication flow is investigated. A metric gear with module size 4 mm, tooth number 38, tip radius 80.25 mm and width 40 mm, is partially immersed and rotated between 0–12 1/s frequencies in room temperature distilled water. Flash and laser sheet visualizations of the global flow field and the boundary layer are presented. Resolved mass flow distributions in the fluid sheet above the water surface are obtained with in-situ liquid trapping (bucketing). The relation between the circumferential velocity and integrated mass flux of the fluid sheet is found to be linear above a critical speed, for which an analytical formula is given. Using dimensional analysis, we show that the relation between the mass flux and gear speed signifies a Reynolds-number independent behavior of the boundary layer around the immersed part of the gear