Temat: chemical kinetics - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: FEDMA - a simple algorithm for theoretical modeling of linear metabolic pathways: from fuzzy data sets to prediction and experiment.
Autorzy:: Pawlowski, Piotr
Zielenkiewicz, Piotr
Powiązania:: https://bibliotekanauki.pl/articles/1041464.pdf
Data publikacji:: 2005
Wydawca:: Polskie Towarzystwo Biochemiczne
Tematy:: linear metabolic pathway
chemical kinetics
algorithm
theoretical modeling
Opis:: A theoretical model of a chain of irreversible Michaelis-Menten reactions proceeding inside a living cell, taking cell growth, division and subcellular compartmentation into account, was proposed. It became a basis for the construction of a "fuzzy" enzymatic data-modeling algorithm (FEDMA) - a procedure allowing the estimation of missing parameter values for the modeled system, in accordance both with the derived theoretical rules and the available experimental data. The obtained tool was tested to model the heme biosynthesis pathway in Saccharomyces cerevisiae, where about 40% of parameters remain unknown. The missing parameters estimated by means of FEDMA fall in the range of expected values.
Źródło:: Acta Biochimica Polonica; 2005, 52, 1; 71-86
0001-527X
Pojawia się w:: Acta Biochimica Polonica
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Biochemical kinetics in changing volumes.
Autorzy:: Pawłowski, Piotr
Zielenkiewicz, Piotr
Powiązania:: https://bibliotekanauki.pl/articles/1043352.pdf
Data publikacji:: 2004
Wydawca:: Polskie Towarzystwo Biochemiczne
Tematy:: glycolytic oscillations
chemical kinetics
cyclin oscillations
varying volume
Opis:: The need of taking into account the change of compartment volume when developing chemical kinetics analysis inside the living cell is discussed. Literature models of a single enzymatic Michaelis-Menten process, glycolytic oscillations, and mitotic cyclin oscillations were tested with appropriate theoretical extension in the direction of volume modification allowance. Linear and exponential type of volume increase regimes were compared. Due to the above, in a growing cell damping of the amplitude, phase shift, and time pattern deformation of the metabolic rhythms considered were detected, depending on the volume change character. The perfomed computer simulations allow us to conclude that evolution of the cell volume can be an essential factor of the chemical kinetics in a growing cell. The phenomenon of additional metabolite oscillations caused by the periodic cell growth and division was theoretically predicted and mathematically described. Also, the hypothesis of the periodized state in the growing cell as the generalization of the steady-state was formulated.
Źródło:: Acta Biochimica Polonica; 2004, 51, 1; 231-243
0001-527X
Pojawia się w:: Acta Biochimica Polonica
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Investigation of the cook-off processes of HMX-based mixed explosives
Autorzy:: Chen, L.
Ma, X.
Lu, F.
Wu, J.
Powiązania:: https://bibliotekanauki.pl/articles/358000.pdf
Data publikacji:: 2014
Wydawca:: Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:: explosives
chemical kinetics
thermal decomposition
cook-off
numerical simulation
Opis:: In order to investigate the characteristics of the thermal reaction for two kinds of mixed explosives, PBXC-10 (HMX/TATB/Binder, 38/57/5) and JO-8 (HMX/Binder, 95/5), multi-point measured temperature cook-off tests were carried out at different heating rates. The thermal transfer and finite chemical reactions that include the β→δ transition of HMX, and the endothermic and exothermic cook-off processes were analyzed. A 3D model of the explosive cook-off test was developed to simulate the thermal and chemical behaviour in a thermal ignition. The decomposition mechanisms for HMX and TATB are described by the multistep, chemical kinetic model. The thermal properties, decomposition pathways, and chemical kinetic reaction rate constants for each component are used to develop the reaction courses at various weight percentages. The thermal decomposition reaction of a multi-component, mixed explosive can be predicted as long as the chemical kinetics model of each single-base explosive and binder are known. The phase transition of HMX has an influence on the temperature of the explosive, especially for an explosive with a high HMX content. For mixed explosives containing HMX and TATB, most of the heat release is produced by the decomposition of HMX before ignition, but TATB can delay the ignition time and decrease the reaction violence in the cook-off process.
Źródło:: Central European Journal of Energetic Materials; 2014, 11, 2; 199-218
1733-7178
Pojawia się w:: Central European Journal of Energetic Materials
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: A study of the local entropy generation rate in a porous media burner
Autorzy:: Mohammadi, I.
Esfahani, J. A.
Kim, K. C.
Powiązania:: https://bibliotekanauki.pl/articles/38597672.pdf
Data publikacji:: 2020
Wydawca:: Instytut Podstawowych Problemów Techniki PAN
Tematy:: porous media burner
chemical kinetics
volumetric heat transfer
axisymmetric combustion
local entropy generation
excess air ratio
Opis:: In this paper, the work and performance of the premixed methane-air porous axisymmetrical burner have firstly been simulated numerically using the CFD tools. For this purpose the set of governing equations has been enriched by an additional energy equation in porous solid, and the chemical species transport has been extended onto the multi-step mechanism (GRI-2-11). This numerical model has been verified on the base of available benchmark experiments. Next, we have studied the local entropy generation problem taking into account not only classical contributions like viscous and turbulent dissipation but also, the porous combustion of gases. The results showed that the greatest portion of entropy generation in the porous medium burner is related to chemical reactions, followed by heat transfer, mass diffusion (mixing) and friction (viscous dissipation), respectively. According to the results, as the excess air ratio increases, the local entropy generation rate due to heat transfer and friction increases and the local entropy generation rate due to chemical reactions is decreased. Also, by increasing the volumetric heat transfer coefficient, the local entropy generation rate due to heat transfer decreases and the local entropy generation rate due to friction and chemical reactions increases. Also, the local entropy generation rate due to mixing does not show a significant change with the changing excess air ratio and volumetric heat transfer coefficient.
Źródło:: Archives of Mechanics; 2020, 72, 3; 257-279
0373-2029
Pojawia się w:: Archives of Mechanics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Numerical study of detonation processes in rotating detonation engine and its propulsive performance
Badanie numeryczne procesów detonacji w wirującym silniku detonacyjnym i jego wydajności napędowej
Autorzy:: Yi, Tae-Hyeong
Lou, Jing
Turangan, Cary Kenny
Wolanski, Piotr
Powiązania:: https://bibliotekanauki.pl/articles/36427720.pdf
Data publikacji:: 2020
Wydawca:: Sieć Badawcza Łukasiewicz - Instytut Lotnictwa
Tematy:: detonation wave
rotating detonation engine
propulsion
chemical kinetics
finite volume method
adaptive mesh refinement
fala detonacyjna
wirujący silnik detonujący
napęd
kinetyka chemiczna
metoda skończonej objętości
adaptacyjne udoskonalanie siatki
Opis:: Numerical studies on detonation wave propagation in rotating detonation engine and its propulsive performance with one- and multi-step chemistries of a hydrogen-based mixture are presented. The computational codes were developed based on the three-dimensional Euler equations coupled with source terms that incorporate high-temperature chemical reactions. The governing equations were discretized using Roe scheme-based finite volume method for spatial terms and second-order Runge-Kutta method for temporal terms. One-dimensional detonation simulations with one- and multi-step chemistries of a hydrogen-air mixture were performed to verify the computational codes and chemical mechanisms. In two-dimensional simulations, detonation waves rotating in a rectangular chamber were investigated to understand its flowfield characteristics, where the detailed flowfield structure observed in the experiments was successfully captured. Three-dimensional simulations of two-waved rotating detonation engine with an annular chamber were performed to evaluate its propulsive performance in the form of thrust and specific impulse. It was shown that rotating detonation engine produced constant thrust after the flowfield in the chamber was stabilized, which is a major difference from pulse detonation engine that generates repetitive and intermittent thrust.
Przedstawiono badania numeryczne propagacji fali detonacyjnej w wirującym silniku detonacyjnym oraz jego wydajności pędnej z jedno- i wielostopniową mieszanką chemiczną na bazie wodoru. Kody obliczeniowe opracowano w oparciu o trójwymiarowe równania Eulera w połączeniu z pojęciami źródłowymi, które obejmują wysokotemperaturowe reakcje chemiczne. Obowiązujące równania zostały zdyskredytowane przy użyciu metody skończonej objętości opartej na schemacie Roe'a dla terminów przestrzennych oraz metody Runge-Kutta drugiego rzędu dla terminów czasowych. W celu weryfikacji kodów obliczeniowych i mechanizmów chemicznych przeprowadzono jednowymiarowe symulacje detonacji z jedno- i wieloetapowymi chemikaliami mieszaniny wodoru i powietrza. W symulacjach dwuwymiarowych badano fale detonacyjne obracające się w komorze prostokątnej w celu zrozumienia jej charakterystyki pola przepływu, gdzie udało się uchwycić szczegółową strukturę pola przepływu zaobserwowaną w doświadczeniach. Przeprowadzono trójwymiarowe symulacje dwufalowego wirującego silnika detonacyjnego z komorą pierścieniową w celu oceny jego właściwości pędnych w postaci ciągu i impulsu właściwego. Wykazano, że wirujący silnik detonujący wytwarza stały ciąg po ustabilizowaniu się pola przepływu w komorze, co stanowi istotną różnicę w stosunku do silnika detonującego impulsowo, który wytwarza powtarzalny i przerywany ciąg.
Źródło:: Transactions on Aerospace Research; 2020, 3 (260); 30-48
0509-6669
2545-2835
Pojawia się w:: Transactions on Aerospace Research
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Flameless oxidation at the GT26 gas turbine: numerical study via full chemistry
Autorzy:: Ochrymiuk, T.
Badur, J.
Powiązania:: https://bibliotekanauki.pl/articles/1955802.pdf
Data publikacji:: 2001
Wydawca:: Politechnika Gdańska
Tematy:: combustion
full kinetics of chemical reaction
CFD
computational fluid dynamics CFD
flameless oxidation
flameless combustion
Opis:: Sequential combustion was first applied to gas turbines more than 40 years ago, and almost half of these early machines are still operating. This form of oxidation leads to the flame-less combustion at a second chamber. In GT26, the second stage combustor has 24 SEV burners which are similar in action to the well known ABB EV burner. In this paper, a 3D numerical simulation of the first EV combustor and the second SEV-combustor are performed for normal operating conditions (exhaust mass flow 542 kg/s, exhaust temperature 610 C). Physical modelling of the flame-less oxidation is based on an original implementation of the Gri-Mech mechanism (325 chemical reactions) into the Fluent 5.4. Precise estimation of NOx emission and other pollutants has been done.
Źródło:: TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2001, 5, 2; 239-246
1428-6394
Pojawia się w:: TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: A study on the dissolution kinetics of iron oxide leaching from clays by oxalic acid
Autorzy:: Arslan, Volkan
Powiązania:: https://bibliotekanauki.pl/articles/1447278.pdf
Data publikacji:: 2021
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:: clay
physico-chemical characterization
chemical leaching
oxalic acid
dissolution kinetics
activation energy
Opis:: Clay is widely used in a number of industries due to its special properties like fine particle size, brightness and whiteness, chemical inertness, platy structure, etc. In this study, the general characteristics of clays have been investigated by XRF, XRD, FT-IR, TG-DTA and SEM. The presence of iron as an impurity decreases its commercial value due to giving unwanted colors to clay mineral. Therefore, the dissolution capacity of clay ore was investigated by oxalic acid leaching. Under optimized leaching conditions (0.8 M oxalic acid concentration, 85°C reaction temperature, 1.75 ambient pH, 106+75 µm particle size, 15% w/v solids concentration and 150 min. leaching time) with 250 rpm stirring, 83.90% of $Fe_2O_3$ was removed. The amount of iron oxide, the main impurity in the clay, has been reduced from 2.70 to 0.40%. The iron dissolution kinetics was mainly controlled by internal diffusion control of shrinking core model and activation energy, $E_a$, of 26.29 kJ/mol was obtained for the process. The results also showed that the studied clays have adequate characteristics for ceramics industry, earthenware and porcelain production.
Źródło:: Physicochemical Problems of Mineral Processing; 2021, 57, 3; 97-111
1643-1049
2084-4735
Pojawia się w:: Physicochemical Problems of Mineral Processing
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Leaching kinetics of atrazine and inorganic chemicals in tilled and orchard soils
Autorzy:: Szajdak, L.W.
Lipiec, J.
Siczek, A.
Nosalewicz, A.
Majewska, U.
Powiązania:: https://bibliotekanauki.pl/articles/25267.pdf
Data publikacji:: 2014
Wydawca:: Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:: leaching
kinetics
atrazine
inorganic chemical
tilled soil
orchard soil
Opis:: The aim of this study was to verify first-order kinetic reaction rate model performance in predicting of leaching of atrazine and inorganic compounds (K+1, Fe+3, Mg+2, Mn+2, NH4 +, NO3 - and PO4 -3) from tilled and orchard silty loam soils. This model provided an excellent fit to the experimental concentration changes of the compounds vs. time data during leaching. Calculated values of the first-order reaction rate constants for the changes of all chemicals were from 3.8 to 19.0 times higher in orchard than in tilled soil. Higher first-order reaction constants for orchard than tilled soil correspond with both higher total porosity and contribution of biological pores in the former. The first order reaction constants for the leaching of chemical compounds enables prediction of the actual compound concentration and the interactions between compound and soil as affected by management system. The study demonstrates the effectiveness of simultaneous chemical and physical analyses as a tool for the understanding of leaching in variously managed soils.
Źródło:: International Agrophysics; 2014, 28, 2
0236-8722
Pojawia się w:: International Agrophysics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Separation and physicochemical properties of residual carbon in gasification slag
Autorzy:: Fan, Xiaoting
Fan, Panpan
Liu, Xiaodong
Ren, Zhenyang
Bao, Weiren
Wang, Jiancheng
Dong, Lianping
Fan, Minqiang
Powiązania:: https://bibliotekanauki.pl/articles/2175447.pdf
Data publikacji:: 2022
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:: waste treatment
gasification slag
physical properties
chemical properties
structural features
reaction kinetics
Opis:: Gasification slag is the solid waste produced in the coal gasification process, and its treatment and disposal problems are becoming more and more serious. In this study, the gasification slag produced in a chemical base in northern China and its residual carbon obtained by gravity separation of water medium were taken as the research objects, and their physicochemical properties were analyzed comprehensively. The residual carbon products, ash-rich products and high-ash products were obtained from the gasification slag after gravity separation. Under the optimal structure, the ignition loss of residual carbon products was reduced from 79.80% to 16.84%, and the yield was 11.64%. The high content of amorphous carbon and developed pores in the residual carbon provide the possibility of manufacturing high value-added materials. Raman spectrum showed that the residual carbon had lower aromaticity, higher content of small and medium aromatic ring structures, lower structural stability and easier combustion. Thermogravimetric combustion kinetics showed that the average combustion rate of residual carbon was 0.325(dm/dt)mean/%•min−1, the comprehensive combustion characteristic index was 1.41•10−9%2•min−2•°C−3. It has excellent performance and can be used as a raw material for mixed combustion in a circulating fluidized bed. The analysis of physical and chemical properties of residual carbon is of great significance for follow-up exploration of the resource utilization and high-value utilization of the residual carbon.
Źródło:: Physicochemical Problems of Mineral Processing; 2022, 58, 6; art. no. 154928
1643-1049
2084-4735
Pojawia się w:: Physicochemical Problems of Mineral Processing
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Regularities of Crystallization Heat Release During Solidification of Alloyed Cast Irons
Autorzy:: Aftandiliants, Y.
Gnyloskurenko, S.
Meniailo, H.
Khrychikov, V.
Lomakin, V.
Powiązania:: https://bibliotekanauki.pl/articles/27314122.pdf
Data publikacji:: 2023
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:: alloying
cast irons
crystallization
kinetics of crystallization
chemical composition
stopowanie
żeliwo
krystalizacja
kinetyka krystalizacji
skład chemiczny
właściwości
Opis:: The chemical composition of alloys plays an important role at their crystallization and influences the solid phase formation, and thus, microstructure and properties. The present paper studies the release of the heat of crystallization of alloyed wear-resistant cast irons in order to determine the quantitative patterns of the chemical composition influence to the kinetics of crystallization. The differential thermal analysis was applied to get the data of heat release, its rate at cast iron temperature decrease. The normalized dependence of the amount of crystallization heat over time was obtained. The main temperature parameters were analyzed and four stages at irons crystallization were established and characterized with their duration and released heat. The multiple correlation analysis allowed considering a numerous physical and chemical factors and distinguishing their role at crystallization of irons. As a result, the quantitative regularities are determined of influencing the content of alloying elements, impurities and carbides on a heat and time of crystallization at the different stages of solidification, which are of great importance in developing alloyed irons with required quality and properties.
Źródło:: Archives of Foundry Engineering; 2023, 23, 1; 110--117
1897-3310
2299-2944
Pojawia się w:: Archives of Foundry Engineering
Dostawca treści:: Biblioteka Nauki

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