249 research outputs found
Anaerob fermentációs folyamatok optimálása a mikroalga alkalmazhatóság továbbá a mikroelem adagolás tekintetében
Kinetics of Charcoal Devolatilization
The devolatilization kinetics of a biomass charcoal was studied by thermogravimetry - mass spectrometry. The overall mass loss rate (DTG curve) and the mass spectrometric intensities of ions H2+, CH3+, C2H2+, C2H3+ and C2H5+ were evaluated. The distributed activation energy model (DAEM) was employed, since it can mathematically represent the physical and chemical inhomogeneity of the charcoal. Some of the evaluated experimental curves consisted of 2 - 4 overlapping partial peaks. In those cases parallel reactions were assumed, and each reaction was described by a DAEM. The unknown parameters were determined by a simultaneous least squares evaluation of a series of experiments. Parameters were identified that enabled the model to describe equally well the non-isothermal experiments and the experiments containing isothermal sections. Kinetic information was obtained on the drying and the evaporation of the organics trapped on the surface of the samples; the decomposition of the side groups with low thermal stability; the splitting-off of the more resistant side groups and the formation of the aromatic rings; and the elimination of heteroaromatic oxygen followed by the formation of polyaromatic structures during carbonization
Kinetics of the thermal decomposition of cellulose under the experimental conditions of thermal analysis. Theoretical extrapolations to high heating rates.
Thermobalance - mass spectrometer (TG-MS) experiments carried out by the authors in a period of 8 years are reviewed and analyzed. Celluloses and lignocellulosic biomass samples were studied. The data are evaluated by the method of least squares. The results indicate that a single rate controlling reaction step dominates the kinetics of the cellulose decomposition at low heating rates (2 - 20°C/min) provided that the heat and mass transport problems are experimentally eliminated and the amount of catalytic impurities is reduced by dilute acid or hot water washing treatments. The kinetic parameters obtained from the experiments with different cellulose and biomass samples evidenced only ca. 8 percent scattering. A simple explanation is given for the kinetic compensation effect observed. Theoretical extrapolations are presented to predict the behavior of extremely small, idealized cellulose samples at high heating rates.
Keywords: Cellulose, Biomass, Thermal Decomposition, Thermogravimetry, Pyrolysis, Reaction Kinetics, Kinetic Compensation Effec
A rövidĂtett házastársi stressz skála pszichometriai jellemzĹ‘i = Psychometric characteristics of the shortened marital stress scale
CĂ©lkitűzĂ©s: A Gottsegen György Országos KardiolĂłgiai IntĂ©zet Kockázat Vizsgálatának cĂ©lja elsĹ‘sorban a nyitott szĂvműtĂ©ten átesett betegek pszichoszociális kockázati tĂ©nyezĹ‘inek vizsgálata Ă©s követĂ©se. MĂłdszer: 137, nyitott szĂvműtĂ©ten átesett betegnĂ©l (87 fĂ©rfi Ă©s 50 nĹ‘) a 17 tĂ©teles Házastársi Stressz Skála magyar változata a műtĂ©t után kĂ©t Ă©vvel kerĂĽlt felvĂ©telre, majd a kĂ©rdĹ‘Ăv Varimax rotáciĂłval törtĂ©nĹ‘ faktoranalĂzisĂ©t követĹ‘en teszteltĂĽk a kĂ©rdĹ‘Ăv rövidĂtett változatát is. EredmĂ©nyek: A 17 tĂ©teles Házastársi Stressz Skála (Cronbach-alfa 0,77) a faktoranalĂzis során öt kĂĽlönállĂł dimenziĂłt eredmĂ©nyezett: a szeretet-bizalom, a problĂ©mák, a szexuális kapcsolat, a szĂvbetegsĂ©g hatása a szexualitásra, valamint a szemĂ©lyes identitás faktorokat. A tĂ©telek az egyes dimenziĂłkban jĂłl elkĂĽlönĂĽltek, mindössze kĂ©t tĂ©telt találtunk, melyek nem egyĂ©rtelműen tartoztak egy faktorhoz, ezeket a rövidĂtĂ©s során kihagytuk. A kiválasztott RövidĂtett Házastársi Stressz Skála öt tĂ©telĂ©nek (három kĂ©rdĂ©s az elsĹ‘ faktorbĂłl, egy a másodikbĂłl, egy az ötödikbĹ‘l) skálaösszege korrelált a 17 tĂ©tel skálaösszegĂ©vel (r = 0,902, p<0,001), belsĹ‘ konzisztenciája megfelelĹ‘ (Cronbach-alfa 0,69). KonklĂşziĂł: A RövidĂtett Házastársi Stressz Skála pszichometriai jellemzĹ‘i megfeleÂlĹ‘ek
Az életesemények, a stressz és a megküzdés nemi különbségei = Gender differences of life events, stress, and coping
A tanulmány az Ă©letesemĂ©nyek, a stressz Ă©s a megkĂĽzdĂ©s nemi kĂĽlönbsĂ©geit elemzi hazai populáciĂłn. A mintát a Hungarostudy 2002 (HS2002, N=12 668) Ă©s a Hungarostudy 2006 (HS2006, N=5020) epidemiolĂłgiai vizsgálatok szolgáltatták. Az elsĹ‘ elemzĂ©s a negatĂv Ă©letesemĂ©nyek gyakorisági eloszlásának Ă©s szubjektĂv Ă©rtĂ©kelĂ©sĂ©nek nemi kĂĽlönbsĂ©geivel foglalkozik. Ezt követĹ‘en arra kerestĂĽnk választ, hogy a stresszt okozĂł Ă©letesemĂ©nyek Ă©s a krĂłnikus betegsĂ©gek kapcsolatát mennyiben befolyásolja a vizsgálati szemĂ©ly neme. A harmadik vizsgálatban vĂ©gĂĽl a megkĂĽzdĂ©s nemi kĂĽlönbsĂ©geit elemeztĂĽk. EredmĂ©nyeink szerint bár a nĹ‘k összessĂ©gĂ©ben nem találkoznak több negatĂv Ă©letesemĂ©nnyel, fokozottabb stresszválaszokat adnak, valamint szubjektĂve nehezebben Ă©lik meg ezeket. Ez a sĂ©rĂĽlĂ©kenysĂ©g Ă©rhetĹ‘ tetten abban a jelensĂ©gben is, hogy stressz hatására a nĹ‘knĂ©l jobban megnĹ‘ számos krĂłnikus betegsĂ©g kockázata (pszichiátriai betegsĂ©gek, OR = 3,1; daganatos betegsĂ©gek, OR = 2,1). A megkĂĽzdĂ©s nemi kĂĽlönbsĂ©geit vizsgálva azt találtuk, hogy a nĹ‘k az Ă©rzelemfĂłkuszĂş megkĂĽzdĂ©sen belĂĽl más mĂłdokat preferálnak, megdĹ‘lni látszik azonban az a sztereotip kĂ©p, hogy a fĂ©rfiak inkább Ă©lnĂ©nek a racionális, problĂ©mafĂłkuszĂş copinggal.
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Our study reports gender differences in life events, stress, and coping based on a Hungarian nationwide epidemiological survey: the Hungarostudy 2002 (HS2002, N=12 668) and the Hungarostudy 2006 (HS2006, N=5020). The study contains three analyses. The first one focused on the gender differences in the frequency of negative life events and their subjective appraisal. The second one explores how gender influences the relationship between life events and chronic illness. The third one studies the gender differences in coping. Our results show that women do not experience more negative life events than man but give stronger response to stress and they assess the same events as worse comparing to men. This increased vulnerability may also be the cause the phenomenon that stress results in a greater risk of some chronic illness among women (psychiatric illness, OR = 3.1; cancer; OR = 2.1). In coping, we found differences only in the coping method within emotion-focused coping strategies, on the other hand, our data do not support the stereotype that men use more rational, problem-focused coping strategies that women
Least squares criteria for the kinetic evaluation of thermoanalytical experiments. Examples from a char reactivity study
The mathematical modeling of the chemical processes is a crucial problem of the thermal analysis. Simple models with few parameters seldom can describe the real complexity of the phenomena arising during the heating of the various substances. In the case of more complex models the determination of the parameters and the validation of the model require the evaluation of carefully designed experimental series. The one-by-one evaluation of the experiments is a mathematically ill-defined problem at a larger number of unknown parameters. The non-statistical experimental errors of the thermal analysis hinder the determination of a single parameter set by the simultaneous least squares evaluation of the experiments. This paper discusses several evaluation techniques for the handling of the non-statistical errors during the least squares evaluation of experimental series. The methods are illustrated by the evaluation of oxidative thermogravimetric experiments of a lignite and a coal char.
Keywords: Kinetics, least squares evaluation, thermogravimetry, char reactivity, temperature programmed combustion
A szabadkőműves dosszié : A Magyar Királyi Belügyminisztérium szabadkőművesek megfigyeléséről szóló jelentése, 1938
Kinetic modeling of biomass pyrolysis : 10 years of a US - Hungarian cooperation
The thermal decomposition of lignocellulosic biomass materials and their major components is discussed. Thermogravimetric and DSC curves at different T(t) heating programs were evaluated by the method of least squares. Pseudo-first order models, parallel, successive and competitive reaction schemes and complex reaction networks were employed in the modeling. The following topics are treated: thermal decomposition of cellulose at low (2°/min) and high (50 - 80°C/min) heating rates; low temperature phenomena; the validity of the Broido – Shafizadeh model; effects of mineral catalysts; cellulose pyrolysis in closed sample holders; thermal decomposition kinetics of xylan, lignin and lignocellulosic plant samples.
Keywords: Biomass, Cellulose, Hemicellulose, Lignin, Reaction kinetics, Thermogravimetry, DS
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