Journal articles on the topic 'Carbon dioxide – Mathematical models'
To see the other types of publications on this topic, follow the link: Carbon dioxide – Mathematical models.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Carbon dioxide – Mathematical models.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Orlovic, Aleksandar, Stojan Petrovic, and Dejan Skala. "Mathematical modeling and simulation of gel drying with supercritical carbon dioxide." Journal of the Serbian Chemical Society 70, no. 1 (2005): 125–36. http://dx.doi.org/10.2298/jsc0501125o.
Full textAbstract:
Mathematical models of alumina/silica gel supercritical drying with carbon dioxide were studied using supercritical drying experimental data. An alumina/silica gel with zinc chloride was synthesized and dried with superciritical carbon dioxide, and its weight change was monitored as a function of drying time. The pore size distribution of the obtained aerogel was determined using the BET method and nitrogen adsorption/ desorption. The mathematical model of the supercritical drying of the wet gel was represented as unsteady and one-dimensional diffusion of solvent through the aerogel pores filled with supercitical carbon dioxide. Parallel pore model and pores in series model were developed on the basis of the measured porous structure of the aerogel. It was found that these models which use different effective diffusivity value for each pore size were in much better agreement with the experimental data than models which use an overall effective diffusivity. The local effective diffusivity coefficients were calculated using different tortuosity values for each pore size, and they were distributed according to the pore size distribution data. Model simulations of the superciritical drying with carbon dioxide confirmed that the drying temperature and gel particle diameter have a significant influence on the drying time.
2
Khasanov, Marat K., Nail G. Musakaev, Maxim V. Stolpovsky, and Svetlana R. Kildibaeva. "Mathematical Model of Decomposition of Methane Hydrate during the Injection of Liquid Carbon Dioxide into a Reservoir Saturated with Methane and Its Hydrate." Mathematics 8, no. 9 (September 2, 2020): 1482. http://dx.doi.org/10.3390/math8091482.
Full textAbstract:
The article describes a mathematical model of pumping of heated liquid carbon dioxide into a reservoir of finite extent, the pores of which in the initial state contain methane and methane gas hydrate. This model takes into account the existence in the reservoir of three characteristic regions. We call the first region “near”, the second “intermediate”, and the third “far”. According to the problem statement, the first region contains liquid CO2 and hydrate, the second region is saturated with methane and water, the third contains methane and hydrate. The main features of mathematical models that provide a consistent description of the considered processes are investigated. It was found that at sufficiently high injection pressures and low pressures at the right reservoir boundary, the boundary of carbon dioxide hydrate formation can come up with the boundary of methane gas hydrate decomposition. It is also shown that at sufficiently low values of pressure of injection of carbon dioxide and pressure at the right boundary of the reservoir, the pressure at the boundary of hydrate formation of carbon dioxide drops below the boiling pressure of carbon dioxide. In this case, for a consistent description of the considered processes, it is necessary to correct the mathematical model in order to take into account the boiling of carbon dioxide. Maps of possible solutions have been built, which show in what ranges of parameters one or another mathematical model is consistent.
3
Leonzio, Grazia, and Edwin Zondervan. "Surface-Response Analysis for the Optimization of a Carbon Dioxide Absorption Process Using [hmim][Tf2N]." Processes 8, no. 9 (September 1, 2020): 1063. http://dx.doi.org/10.3390/pr8091063.
Full textAbstract:
The [hmim][Tf2N] ionic liquid is considered in this work to develop a model in Aspen Plus® capturing carbon dioxide from shifted flue gas through physical absorption. Ionic liquids are innovative and promising green solvents for the capture of carbon dioxide. As an important aspect of this research, optimization is carried out for the carbon capture system through a central composite design: simulation and statistical analysis are combined together. This leads to important results such as the identification of significant factors and their combinations. Surface plots and mathematical models are developed for capital costs, operating costs and removal of carbon dioxide. These models can be used to find optimal operating conditions maximizing the amount of captured carbon dioxide and minimizing total costs: the percentage of carbon dioxide removal is 93.7%, operating costs are 0.66 million €/tonCO2 captured (due to the high costs of ionic liquid), and capital costs are 52.2 €/tonCO2 captured.
4
Bobkov, Vladimir I., and Maxim I. Dli. "PECULIARITIES OF CALCULATION OF HEAT AND POWER BALANCE FOR ROASTING CONVEYOR MACHINE." Bulletin of the Saint Petersburg State Institute of Technology (Technical University) 58 (2021): 70–76. http://dx.doi.org/10.36807/1998-9849-2021-58-84-70-76.
Full textAbstract:
The work examines the chemical and energotechnological processes of pellet production from fine apatite-nepheline raw materials: moisture removal, carbonate dissociation, taking into account the thermal and technological features of the functioning of roasting conveyor machines. It was established that the same physicochemical processes differ in quantitative characteristics in the process zones of heating, roasting and recovery. The need of the charge for the heat carrier gas for the corresponding zones, the content of carbon dioxide, iron oxide and carbon in dry pellets, which depend on the chemical composition, the degree of carbon dioxide release, iron oxide oxidation and carbon combustion are taken into account. According to the results of the experimental data and depending on the composition of the charge the following characteristics are calculated for each of the zones: heat consumption for limestone decomposition, specific volume of carbon dioxide, heat output during the oxidation of iron oxide, oxygen flow for iron oxide oxidation, heat introduced by carbon dioxide, initial and final heat of heat carrier gas. The mathematical description of heat and power peculiarities of functioning of roasting conveyor machines is proposed. It is based on energy-balance mathematical models and takes into account thermally activated chemical-energotechnological processes, which take place in apatite-nepheline technogenic raw materials during heating
5
Lazăr, Avram, Cristescu Tudora, and Stoica Monica Emanuela. "Carbon Dioxide Emissions Monitoring in Romania in the Context of Greenhouse Gases Reduction." MATEC Web of Conferences 171 (2018): 05001. http://dx.doi.org/10.1051/matecconf/201817105001.
Full textAbstract:
The weather changes we are currently witnessing, characterised by dynamism and extreme phenomena, are the direct and indirect result of human activities which are determining the global atmosphere change in composition. The paperwork follows the evaluation and comparison of carbon dioxide emission coefficient in case of liquid oil fuels burning. The calculus model used for the carbon dioxide emission coefficient evaluation has been developed based on mathematical models from specific publications. It was applied in the case study based on data from specific literature. The results obtained following the evaluation allowed certain comparisons in the field of carbon dioxide emissions in case of the complete burning of certain fluid hydrocarbons use in industry.
6
Gheni, Saba A., Mohammed F. Abed, Essam K. Halabia, and Saad R. Ahmed. "Investigation of carbon dioxide (CO2) capture in a falling film contactor by computer simulation." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 73 (2018): 43. http://dx.doi.org/10.2516/ogst/2018020.
Full textAbstract:
In this work, mathematical models of carbon dioxide (CO2) absorption by monoethanolamine amine (MEA) in a falling film contactor are developed. The proposed models aim to predict conversion of the gas–liquid reaction along the contactor, gas–liquid interface temperature profile (axial and radial), liquid film thickness along the contactor length, axial and radial concentration profiles of reactants in liquid film, and axial and radial profiles of velocity in the liquid film. A code written in MatLab was used to obtain these profiles based on multi grid method through programming of kinetic and thermodynamic equations and physical properties of the absorption system. The mathematical model is validated by an experimental measurement based on absorption of CO2 gas by MEA solution. Four parameters are studied as independent variables namely, mole fraction of carbon dioxide in gaseous mixture, molar concentration of absorbent (MEA, volumetric flow rate of MEA, and its temperature. It is found that the entrance effect of the falling film contactor is related to axial distance from the contactor entrance exponentially: E=B0exp(−B1y) An optimization technique based on minimization of the sum of the squared error between the experimental and predicted composition of absorption process is used to obtain B0 and B1. It is found that reaction between carbon dioxide and MEA is instantaneous, and the axial conversion of carbon dioxide in the gas phase varies exponentially with the contactor length.
7
Leow, Melvin Khee-Shing. "Configuration of the hemoglobin oxygen dissociation curve demystified: a basic mathematical proof for medical and biological sciences undergraduates." Advances in Physiology Education 31, no. 2 (June 2007): 198–201. http://dx.doi.org/10.1152/advan.00012.2007.
Full textAbstract:
The oxygen dissociation curve (ODC) of hemoglobin (Hb) has been widely studied and mathematically described for nearly a century. Numerous mathematical models have been designed to predict with ever-increasing accuracy the behavior of oxygen transport by Hb in differing conditions of pH, carbon dioxide, temperature, Hb levels, and 2,3-diphosphoglycerate concentrations that enable their applications in various clinical situations. The modeling techniques employed in many existing models are notably borrowed from advanced and highly sophisticated mathematics that are likely to surpass the comprehensibility of many medical and bioscience students due to the high level of “mathematical maturity” required. It is, however, a worthy teaching point in physiology lectures to illustrate in simple mathematics the fundamental reason for the crucial sigmoidal configuration of the ODC such that the medical and bioscience undergraduates can readily appreciate it, which is the objective of this basic dissertation.
8
Ťupek, Boris, Carina A. Ortiz, Shoji Hashimoto, Johan Stendahl, Jonas Dahlgren, Erik Karltun, and Aleksi Lehtonen. "Underestimation of boreal soil carbon stocks by mathematical soil carbon models linked to soil nutrient status." Biogeosciences 13, no. 15 (August 10, 2016): 4439–59. http://dx.doi.org/10.5194/bg-13-4439-2016.
Full textAbstract:
Abstract. Inaccurate estimate of the largest terrestrial carbon pool, soil organic carbon (SOC) stock, is the major source of uncertainty in simulating feedback of climate warming on ecosystem–atmosphere carbon dioxide exchange by process-based ecosystem and soil carbon models. Although the models need to simplify complex environmental processes of soil carbon sequestration, in a large mosaic of environments a missing key driver could lead to a modeling bias in predictions of SOC stock change.We aimed to evaluate SOC stock estimates of process-based models (Yasso07, Q, and CENTURY soil sub-model v4) against a massive Swedish forest soil inventory data set (3230 samples) organized by a recursive partitioning method into distinct soil groups with underlying SOC stock development linked to physicochemical conditions.For two-thirds of measurements all models predicted accurate SOC stock levels regardless of the detail of input data, e.g., whether they ignored or included soil properties. However, in fertile sites with high N deposition, high cation exchange capacity, or moderately increased soil water content, Yasso07 and Q models underestimated SOC stocks. In comparison to Yasso07 and Q, accounting for the site-specific soil characteristics (e. g. clay content and topsoil mineral N) by CENTURY improved SOC stock estimates for sites with high clay content, but not for sites with high N deposition.Our analysis suggested that the soils with poorly predicted SOC stocks, as characterized by the high nutrient status and well-sorted parent material, indeed have had other predominant drivers of SOC stabilization lacking in the models, presumably the mycorrhizal organic uptake and organo-mineral stabilization processes. Our results imply that the role of soil nutrient status as regulator of organic matter mineralization has to be re-evaluated, since correct SOC stocks are decisive for predicting future SOC change and soil CO2 efflux.
9
Semenov, Sergey P., and Artem O. Tashkin. "The carbon cycle models analysis as applied to research wetland ecosystems in Western Siberia." Yugra State University Bulletin 18, no. 4 (January 14, 2023): 145–52. http://dx.doi.org/10.18822/byusu202204145-152.
Full textAbstract:
Subject of research: global climate processes are directly related to greenhouse gases (greenhouse gases, GHG). The main greenhouse gas in the atmosphere is carbon dioxide, which makes the problem of studying the dynamics of the carbon cycle relevant. Of particular interest is the study of the swamp ecosystems of Western Siberia, since they contain significant carbon reserves.
Purpose of research: the work is devoted to an analytical review and analysis of current publications in the field of modeling the dynamics of the carbon cycle.
Methods and objects of research: the most popular dynamic models reflecting schemes and elements of the global carbon cycle, as well as functional dependencies of carbon consumption and release are considered.
Main results of research: analytical reviews of modern scientific results in the field of mathematical modeling of the carbon cycle scheme are given. There is a proposition of a carbon cycle model, which aimed at studying the dynamics of greenhouse gases in swamp ecosystems of Western Siberia.
10
Diniz, Hélio A. G., Tiago F. Paulino, Juan J. G. Pabon, Antônio A. T. Maia, and Raphael N. Oliveira. "Dynamic Model of a Transcritical CO2 Heat Pump for Residential Water Heating." Sustainability 13, no. 6 (March 21, 2021): 3464. http://dx.doi.org/10.3390/su13063464.
Full textAbstract:
This paper presents a distributed mathematical model for a carbon dioxide direct expansion solar-assisted heat pump used to heat bath water. The main components are a gas cooler, a needle valve, an evaporator/collector, and a compressor. To develop the heat exchange models, mass, energy, and momentum balances were used. The model was validated for transient as well as steady state conditions using experimental data. A reasonably good agreement was observed between the predicted temperatures and experimental data. The simulations showed that the time step required to demonstrate the behavior of the heat pump in the transient regime is greater than the time step required for the steady state. The results obtained with the mathematical model revealed that a reduction in the water mass flow rate results in an increase in the water outlet temperature. In addition, when the carbon dioxide mass flow rate is reduced, the compressor inlet and outlet temperatures increase as well as the water outlet temperature.
11
Rees, S. E., and S. Andreassen. "Mathematical Models of Oxygen and Carbon Dioxide Storage and Transport: The Acid-Base Chemistry of Blood." Critical Reviews in Biomedical Engineering 33, no. 3 (2005): 209–64. http://dx.doi.org/10.1615/critrevbiomedeng.v33.i3.10.
Full text
12
Zhao, Mu Qiu, Ming Li, and Yun Feng Shi. "Carbon Storage and Carbon Dioxide Sequestration of Banana Plants at Different Growth Stages." Advanced Materials Research 1010-1012 (August 2014): 662–65. http://dx.doi.org/10.4028/www.scientific.net/amr.1010-1012.662.
Full textAbstract:
Large annual herbaceous plants such as banana (Musa spp.) have a very impressive carbon (C) storage and carbon dioxide (CO2) sequestration in agroecosystems, and play a certain role in global C cycle, climate regulation and reducing global warming. In this paper, we systematically studied C storage on the different growth stages, CO2sequestration and distribution, and mathematical models for predicting CO2sequestration by bananas which were planted in western Hainan island, China. The results showed that C content of dry matter in different structures of banana plants was 45-50% in line with the current results, and in fruit reached the highest, in stems and roots followed, while that in leaves were the lowest. C storage in different structures of banana plants increased exponentially during banana growing process (vegetative growth and bud stage), stems were the major storage structures of C, and roots and leaves also had considerable C storage. C fixed by banana plants was mainly distributed in fruit at fruit growing stage. CO2sequestration was 16.3, 41.1 and 80.0t/ha at vegetative growth, bud and fruit maturity stage separately, and power function model can be applied with stem diameter (D) or composite parameter (D2H) as independent variables to predict.
13
Yang, Xiaoping, and Zhuodi Cai. "Thermodynamic performance analysis of supercritical carbon dioxide Brayton cycle." Thermal Science, no. 00 (2020): 294. http://dx.doi.org/10.2298/tsci200314294y.
Full textAbstract:
S-CO2 (supercritical carbon dioxide) is used as working fluid for power system cycle. This paper presents thermodynamic performance analysis results on S-CO2 Brayton cycle. Based on the assumptions of the relevant initial parameters, the mathematical models of compressor, turbine, recuperator and heater are constructed, and the thermal efficiency of regenerative Brayton cycle and recompression Brayton cycle are calculated and analyzed. The results reveal that the efficiency of the recompression cycle is higher than that of the simple regenerative cycle. The effects of inlet temperature, inlet pressure of the main compressor and inlet temperature, inlet pressure of the turbine on the thermodynamic performance of the recompression cycle are studied, and the influencing mechanism is explained. The results show that the cycle efficiency decreases with the increase of the inlet temperature of the main compressor; there exists an optimum inlet pressure in the main compressor to maximize the cycle efficiency; and the cycle efficiency of the system increases with the increase of the inlet temperature and pressure of the turbine. When the inlet temperature of the turbine exceeds 600 ?, the thermal efficiency of the cycle can reach more than 50%.
14
Raho, Brenda, Gianpiero Colangelo, Marco Milanese, and Arturo de Risi. "A Critical Analysis of the Oxy-Combustion Process: From Mathematical Models to Combustion Product Analysis." Energies 15, no. 18 (September 6, 2022): 6514. http://dx.doi.org/10.3390/en15186514.
Full textAbstract:
Fossil fuels are the most widely used resource for energy production. Carbon dioxide (CO2) emissions are correlated with climate change, and therefore these emissions must be reduced in the future. It is possible by means of many different technologies, and one of the most promising seems to be oxyfuel combustion. This process, with oxygen and recirculating gas, produces a concentrated stream of CO2 and water. In recent years, many scientists carried out research and studies on the oxyfuel process, but a sufficient level of knowledge was not yet reached to exploit the great potential of this new technology. Although such areas of research are still highly active, this work provides an overview and summary of the research undertaken, the state of development of the technology, and a comparison of different plants so far.
15
Wołowicz, Marcin, Jarosław Milewski, and Piotr Lis. "Review of existing and development of a novel mathematical model for supercritical CO2 cycles working fluid." MATEC Web of Conferences 240 (2018): 01036. http://dx.doi.org/10.1051/matecconf/201824001036.
Full textAbstract:
The paper aims to compare the models of working fluids against experimental data for carbon dioxide close to its critical conditions. Fortunately, most of the work is already done and published where the authors compared the models based on the equation of the state (EoS). There are a few other models which were not investigated, thus we would like to add a few new results here and focus only on near-critical properties where the biggest deviation between experimental and calculated properties can be observed. The area of interest was pressure range of 7.39 – 20 MPa and temperature range of 304-340 K just above fluid critical point (7.39 MPa, 304.25 K). Model validation was performed for density and heat capacity as one of the most important parameters in preliminary cycle analysis.
16
O’Neill, David P., and Peter A. Robbins. "A mechanistic physicochemical model of carbon dioxide transport in blood." Journal of Applied Physiology 122, no. 2 (February 1, 2017): 283–95. http://dx.doi.org/10.1152/japplphysiol.00318.2016.
Full textAbstract:
A number of mathematical models have been produced that, given the Pco2 and Po2 of blood, will calculate the total concentrations for CO2 and O2 in blood. However, all these models contain at least some empirical features, and thus do not represent all of the underlying physicochemical processes in an entirely mechanistic manner. The aim of this study was to develop a physicochemical model of CO2 carriage by the blood to determine whether our understanding of the physical chemistry of the major chemical components of blood together with their interactions is sufficiently strong to predict the physiological properties of CO2 carriage by whole blood. Standard values are used for the ionic composition of the blood, the plasma albumin concentration, and the hemoglobin concentration. All Km values required for the model are taken from the literature. The distribution of bicarbonate, chloride, and H+ ions across the red blood cell membrane follows that of a Gibbs-Donnan equilibrium. The system of equations that results is solved numerically using constraints for mass balance and electroneutrality. The model reproduces the phenomena associated with CO2 carriage, including the magnitude of the Haldane effect, very well. The structural nature of the model allows various hypothetical scenarios to be explored. Here we examine the effects of 1) removing the ability of hemoglobin to form carbamino compounds; 2) allowing a degree of Cl− binding to deoxygenated hemoglobin; and 3) removing the chloride (Hamburger) shift. The insights gained could not have been obtained from empirical models. NEW & NOTEWORTHY This study is the first to incorporate a mechanistic model of chloride-bicarbonate exchange between the erythrocyte and plasma into a full physicochemical model of the carriage of carbon dioxide in blood. The mechanistic nature of the model allowed a theoretical study of the quantitative significance for carbon dioxide transport of carbamino compound formation; the putative binding of chloride to deoxygenated hemoglobin, and the chloride (Hamburger) shift.
17
Woehlck, Harvey J., David Mei, Marshall B. Dunning, and Franklin Ruiz. "Mathematical Modeling of Carbon Monoxide Exposures from Anesthetic Breakdown." Anesthesiology 94, no. 3 (March 1, 2001): 457–60. http://dx.doi.org/10.1097/00000542-200103000-00016.
Full textAbstract:
Background Carbon monoxide (CO) is produced by reaction of isoflurane, enflurane, and desflurane in desiccated carbon dioxide absorbents. The inspiratory CO concentration depends on the dryness and identity of the absorbent and anesthetic. The adaptation of existing mathematical models to a rebreathing circuit allows identification of patient factors that predispose to more severe exposures, as identified by carboxyhemoglobin concentration. Methods From our companion study, the authors used quantitative in vitro CO production data for 60 min at 7.5% desflurane or 1.5% isoflurane at 1 l/min fresh gas flow. The carboxyhemoglobin concentration was calculated by iteratively solving the Coburn Forster Kane equation modified for a rebreathing system that incorporates the removal of CO by patient absorption. Demonstrating good fit of predicted carboxyhemoglobin concentrations to published data from animal and human exposures validated the model. Carboxyhemoglobin concentrations were predicted for exposures of various severity, patients of different sizes, hematocrit, and fraction of inspired oxygen. Results The calculated carboxyhemoglobin concentrations closely predicted the experimental results of other investigators, thereby validating the model. These equations indicate the severity of CO poisoning is inversely related to the hemoglobin quantity of a subject. Fraction of inspired oxygen had the greatest effect in patients of small size with low hematocrit values, where equilibrium and not the rate of uptake determined carboxyhemoglobin concentrations. Conclusion This model predicts that patients with low hemoglobin quantities will have more severe CO exposures based on the attainment of a higher carboxyhemoglobin concentration. This includes patients of small size (pediatric population) and patients with anemia.
18
Hassan, Amjed, Salaheldin Elkatatny, and Abdulazeez Abdulraheem. "Intelligent Prediction of Minimum Miscibility Pressure (MMP) During CO2 Flooding Using Artificial Intelligence Techniques." Sustainability 11, no. 24 (December 9, 2019): 7020. http://dx.doi.org/10.3390/su11247020.
Full textAbstract:
Carbon dioxide (CO2) injection is one of the most effective methods for improving hydrocarbon recovery. The minimum miscibility pressure (MMP) has a great effect on the performance of CO2 flooding. Several methods are used to determine the MMP, including slim tube tests, analytical models and empirical correlations. However, the experimental measurements are costly and time-consuming, and the mathematical models might lead to significant estimation errors. This paper presents a new approach for determining the MMP during CO2 flooding using artificial intelligent (AI) methods. In this work, reliable models are developed for calculating the minimum miscibility pressure of carbon dioxide (CO2-MMP). Actual field data were collected; 105 case studies of CO2 flooding in anisotropic and heterogeneous reservoirs were used to build and evaluate the developed models. The CO2-MMP is determined based on the hydrocarbon compositions, reservoir conditions and the volume of injected CO2. An artificial neural network, radial basis function, generalized neural network and fuzzy logic system were used to predict the CO2-MMP. The models’ reliability was compared with common determination methods; the developed models outperform the current CO2-MMP methods. The presented models showed a very acceptable performance: the absolute error was 6.6% and the correlation coefficient was 0.98. The developed models can minimize the time and cost of determining the CO2-MMP. Ultimately, this work will improve the design of CO2 flooding operations by providing a reliable value for the CO2-MMP.
19
Dyukarev, E. A., and S. P. Semenov. "Numerical Modeling of Biogeochemical Carbon Cycles in Swamp Ecosystems." Izvestiya of Altai State University, no. 4(126) (September 9, 2022): 104–9. http://dx.doi.org/10.14258/izvasu(2022)4-16.
Full textAbstract:
A dynamic model of biogeochemical carbon cycles in swamp ecosystems is proposed. There are fast and slow biogeochemical cycles. Fast cycles operate in the biosphere and include photosynthesis, vegetative growth, and decomposition. Swamp ecosystems are one of the significant reservoirs of biogeochemical cycles. It is known that huge reserves of carbon in the form of slightly decomposed organic matter are preserved in the swamps. They are active sources of methane and carbon dioxide runoff from the atmosphere.
Mathematical models of dynamic processes in ecology can be divided into two categories: quantitative and qualitative. Quantitative models, as a rule, are aimed at solving problems of predicting numerical indicators of the dynamics of real systems. They must be modified to consider specific climatic conditions, special types of swamp vegetation, and hydrological regime for their successful application.
Qualitative models written as systems of differential equations assume the finding of singular points, their classification and study for stability, the construction of phase portraits, etc. Such models rarely lend themselves to quantitative verification, but provide important knowledge and understanding of processes in nature. A qualitative study of the system of ordinary differential equations describing carbon cycles is carried out, the types of singular points are investigated, integral curves and phase portraits are constructed.
20
Andreassen, S., and S. E. Rees. "Mathematical Models of Oxygen and Carbon Dioxide Storage and Transport: Interstitial Fluid and Tissue Stores and Whole-Body Transport." Critical Reviews in Biomedical Engineering 33, no. 3 (2005): 265–98. http://dx.doi.org/10.1615/critrevbiomedeng.v33.i3.20.
Full text
21
Kalinichenko, Antonina, Valerii Havrysh, and Vasyl Perebyynis. "Evaluation of Biogas Production and Usage Potential." Ecological Chemistry and Engineering S 23, no. 3 (September 1, 2016): 387–400. http://dx.doi.org/10.1515/eces-2016-0027.
Full textAbstract:
Abstract The aim of the research is the development of theoretical and methodical bases for determining the feasibility of plant raw materials growing for its further bioconversion into energy resources and technological materials to maximize profit from business activities. Monograph, statistics, modelling and abstract logical methods have been used during the research. Directions of biogas usage have been examined. Biogas yields from different crops have been analyzed. It has been determined that high methane yields can be provided from root crops, grain crops, and several green forage plants. So, forage beet and maize can provide more than 5,500 m3 of biogas per hectare. Attention is paid to the use of by-products of biogas plants, especially carbon dioxide. Carbon dioxide is an important commodity and can increase profitability of biogas plant operating. It can be used for different purposes (food industry, chemical industry, medicine, fumigation, etc). The most important parameters of the biogas upgrading technologies have been analyzed. If output of an upgrade module is more than 500 nm3/h, investment costs of different available technologies are almost equal. According to experts, it is economically feasible to use anaerobic digestion biogas systems to upgrade biomethane provided their performance is equivalent to 3,000 litres of diesel fuel per day. The economic and mathematical models have been suggested to determine the feasibility of growing plant materials to maximize the gross profit. The target function is the maximum gross income from biogas utilization. It has the following limitations: annual production of biogas, consumption of electricity, heat and motor fuels. The mathematical model takes into account both meeting own requirement and selling surplus energy resources and co-products including carbon dioxide. In case of diesel fuel substitution, an ignition dose of diesel fuels has been considered. The algorithm for making a decision on construction of a biogas plant has been offered.
22
Simeski, Filip, Arnout M. P. Boelens, and Matthias Ihme. "Modeling Adsorption in Silica Pores via Minkowski Functionals and Molecular Electrostatic Moments." Energies 13, no. 22 (November 16, 2020): 5976. http://dx.doi.org/10.3390/en13225976.
Full textAbstract:
Capillary condensation phenomena are important in various technological and environmental processes. Using molecular simulations, we study the confined phase behavior of fluids relevant to carbon sequestration and shale gas production. As a first step toward translating information from the molecular to the pore scale, we express the thermodynamic potential and excess adsorption of methane, nitrogen, carbon dioxide, and water in terms of the pore’s geometric properties via Minkowski functionals. This mathematical reconstruction agrees very well with molecular simulations data. Our results show that the fluid molecular electrostatic moments are positively correlated with the number of adsorption layers in the pore. Moreover, stronger electrostatic moments lead to adsorption at lower pressures. These findings can be applied to improve pore-scale thermodynamic and transport models.
23
Туркин, В. А., Г. В. Игнатенко, В. В. Беляев, С. С. Зубко, and Р. И. Джиоев. "Fuel management to reduce carbon dioxide emissions from marine diesel engines." MORSKIE INTELLEKTUAL`NYE TEHNOLOGII)</msg>, no. 4(58) (December 2, 2022): 106–12. http://dx.doi.org/10.37220/mit.2022.58.4.030.
Full textAbstract:
Выполнено моделирование рабочих процессов судового дизельного двигателя MAN D&T серии MC с целью снижения выбросов диоксида углерода с отработавшими газами. Целью моделирования был поиск конструктивных и эксплуатационных решений, влияющих на эмиссию СO2. При выполнении расчетного исследования использовалась математическая модель комбинированного двигателя внутреннего сгорания, реализованная в компьютерной программе ДИЗЕЛЬ-РК. В качестве исследуемых переменных приняты степень сжатия, угол опережения и продолжительность впрыска топлива, значения которых можно устанавливать без внесения существенных изменений в конструкцию двигателя. Получены математические модели в виде уравнений регрессии, описывающие влияние исследуемых параметров подачи топлива (степень сжатия, угол опережения впрыска топлива и продолжительность впрыска топлива) на целевые функции – удельный выброс диоксида углерода и эффективная мощность дизельного двигателя 6S60MC. Для определения коэффициентов уравнения регрессии реализовано планирование полного факторного эксперимента второго порядка. С целью поиска минимального значения выбросов диоксида углерода используя метод обобщенного приведенного градиента решена задача выбора оптимальных значений степени сжатия, продолжительности впрыска топлива и угла опережения впрыска топлива для заданной эффективной мощности судового дизельного двигателя 6S60MC. Показано, что, например, при мощности двигателя 10000 кВт снижение выбросов диоксида углерода за счет оптимизации указанных параметров топливоподачи будет равно 7,37 %. The simulation of the working processes of the MAN D&T MC series marine diesel engine was carried out in order to reduce carbon dioxide emissions with exhaust gases. The purpose of the simulation was to find design and operational solutions that affect CO2 emissions. When performing a computational study, a mathematical model of a combined internal combustion engine implemented in the DIESEL-RK computer program was used. The studied variables are the compression ratio, the advance angle and the duration of fuel injection, the values of which can be set without making significant changes to the engine design. Mathematical models are obtained in the form of regression equations that describe the effect of the studied fuel supply parameters (compression ratio, fuel injection advance angle and fuel injection duration) on the target functions - specific carbon dioxide emission and effective power of the 6S60MC diesel engine. To determine the coefficients of the regression equation, planning of a complete factorial experiment of the second order is implemented. In order to find the minimum value of carbon dioxide emissions using the generalized reduced gradient method, the problem of choosing the optimal values of the compression ratio, fuel injection duration and fuel injection advance angle for a given effective power of a 6S60MC marine diesel engine is solved. It is shown that, for example, with an engine power of 10,000 kW, the reduction in carbon dioxide emissions by optimizing the specified fuel supply parameters will be 7.37%.
24
Ma, Ping Hua, Hong Fu Fan, and Ke Li. "A Model with Back-Propagation Algorithm for Recovery Efficiency Forecast of Carbon Dioxide Flooding." Applied Mechanics and Materials 295-298 (February 2013): 3137–41. http://dx.doi.org/10.4028/www.scientific.net/amm.295-298.3137.
Full textAbstract:
As one of the most important displacements in producing petroleum, CO2 flooding has been developed for nearly 50 years around the world in order to improve the tertiary recovery. The recovery efficiency, R, is a key parameter in the CO2 displacement of crude oil. Traditionally, R is determined by conducting CO2 flooding experiment, requiring considerable resources and long time periods, with the consequence of a limited number of core plug evaluations for a particular reservoir. Thus, the estimation of R with mathematical models is developed in recent years, which also needs plenty of relevant parameters considered. The study reported in this paper uses artificial neural network to determine R. Five dimensionless variables are considered to analyse the CO2 immiscible displacement process. An optimal model is chosen with its suitable hidden layer nodes and activation functions for the hidden and output layers. Its performance is compared with the numerical simulation model, demonstrating the superior performance of the proposed R prediction model.
25
BIDDULPH, George Elliot, Yannick Enock BOCKO, Pierre BOLA, Bart CREZEE, Greta C. DARGIE, Ovide EMBA, Selena GEORGIOU, et al. "Current knowledge on the Cuvette Centrale peatland complex and future research directions." BOIS & FORETS DES TROPIQUES 350 (January 4, 2022): 3–14. http://dx.doi.org/10.19182/bft2021.350.a36288.
Full textAbstract:
The Cuvette Centrale is the largest tropical peatland complex in the world, covering approximately 145,000 km2 across the Republic of Congo and the Democratic Republic of Congo. It stores ca. 30.6 Pg C, the equivalent of three years of global carbon dioxide emissions and is now the first trans-national Ramsar site. Despite its size and importance as a global carbon store, relatively little is known about key aspects of its ecology and history, including its formation, the scale of greenhouse gas flows, its biodiversity and its history of human activity. Here, we synthesise available knowledge on the Cuvette Centrale, identifying key areas for further research. Finally, we review the potential of mathematical models to assess future trajectories for the peatlands in terms of the potential impacts of resource extraction or climate change.
26
Hoppej, Dominik, and Miroslav Variny. "Industrial-Scale Hydrogen Production Plant Modelling." Advances in Thermal Processes and Energy Transformation 4, no. 1 (2021): 09–15. http://dx.doi.org/10.54570/atpet2021/04/01/0009.
Full textAbstract:
Considering the process characteristics, hydrogen production via steam methane reforming is a vital part of oil refinery not just in terms of materials, but of energy integration as well. This work extends the mathematical model describing hydrogen production by ATE (Approach to Equilibrium) parameters implemented within the chemical reactors’ models. Equations for ATE parameter prediction, i.e. mass flow of process feed (natural gas) and reaction temperature, were formulated. Verification of the whole model as well as of its parameters was performed using process data from a real hydrogen plant. The extended mathematical model is suitable for the evaluation of the influence of increased hydrogen content in natural gas on plant´s material and energy efficiency, as renewable hydrogen injection and co-transport in natural gas pipelines in future is proposed by the European Union as a means of decreasing carbon dioxide emissions.
27
Karunarathne, Sumudu S., Khim Chhantyal, Dag A. Eimer, and Lars E. Øi. "Artificial Neural Networks (ANNs) for Density and Viscosity Predictions of CO2 Loaded Alkanolamine + H2O Mixtures." ChemEngineering 4, no. 2 (April 15, 2020): 29. http://dx.doi.org/10.3390/chemengineering4020029.
Full textAbstract:
The physical properties, like density and viscosity, of alkanolamine + H2O (water) + CO2 (carbon dioxide) mixtures receive a significant amount of attention as they are essential in equipment sizing, mathematical modelling and simulations of amine-based post-combustion CO2 capture processes. Non-linear models based on artificial neural networks (ANNs) were trained to correlate measured densities and viscosities of monoethanol amine (MEA) + H2O, MEA + H2O + CO2, and 2-amino-2-methyl-1-propanol (AMP) + MEA + H2O + CO2 mixtures and results were compared with conventional correlations found in literature. For CO2-loaded aqueous amine mixtures, results from the ANN models are in good agreement with measured properties with less than 1% average absolute relative deviation (AARD). The ANN-based methodology shows much better agreement (R2 > 0.99) between calculated and measured values than conventional correlations.
28
Wen, Baole, Daria Akhbari, Li Zhang, and Marc A. Hesse. "Convective carbon dioxide dissolution in a closed porous medium at low pressure." Journal of Fluid Mechanics 854 (August 31, 2018): 56–87. http://dx.doi.org/10.1017/jfm.2018.622.
Full textAbstract:
Motivated by the persistence of natural carbon dioxide ($\text{CO}_{2}$) fields, we investigate the convective dissolution of $\text{CO}_{2}$ at low pressure (below 1 MPa) in a closed system, where the pressure in the gas declines as convection proceeds. This introduces a negative feedback that reduces the convective dissolution rate even before the brine becomes saturated. We analyse the case of an ideal gas with a solubility given by Henry’s law, in the limits of very low and very high Rayleigh numbers. The equilibrium state in this system is determined by the dimensionless dissolution capacity, $\unicode[STIX]{x1D6F1}$, which gives the fraction of the gas that can be dissolved into the underlying brine. Analytic approximations of the pure diffusion problem with $\unicode[STIX]{x1D6F1}>0$ show that the diffusive base state is no longer self-similar and that diffusive mass transfer declines rapidly with time. Direct numerical simulations at high Rayleigh numbers show that no constant flux regime exists for $\unicode[STIX]{x1D6F1}>0$; nevertheless, the quantity $F/C_{s}^{2}$ remains constant, where $F$ is the dissolution flux and $C_{s}$ is the dissolved concentration at the top of the domain. Simple mathematical models are developed to predict the evolution of $C_{s}$ and $F$ for high-Rayleigh-number convection in a closed system. The negative feedback that limits convection in closed systems may explain the persistence of natural $\text{CO}_{2}$ accumulations over millennial time scales.
29
Shayakhmetov, A. I., V. L. Malyshev, E. F. Moiseeva, and A. I. Ponomarev. "Estimation of efficiency of oil extraction with supercritical CO2 in a low-permeability reservoir." SOCAR Proceedings, SI2 (December 30, 2021): 210–20. http://dx.doi.org/10.5510/ogp2021si200592.
Full textAbstract:
The results of experimental study of oil extraction by supercritical carbon dioxide in a low-permeability reservoir are presented. As an object of study, we selected core samples from a low-permeability oil-saturated reservoir of one of the fields in Western Siberia, which is currently being developed in the regime of depletion of reservoir energy. The contact time of supercritical carbon dioxide with composite core models in three experiments was 8, 24, and 72 hours, respectively. Based on the results of laboratory experiments, the dynamics of the penetration of carbon dioxide along the depth of the composite core model was established. The value of the oil recovery factor and it’s distribution along the length of the core model in time is given. Keywords: carbon dioxide; low-permeability reservoir; mnimum miscibility pressure; slim-tube; extraction; oil recovery.
30
Shpigunova, O. I., and A. A. Glazunov. "Numerical Simulation of Pulsed Arc Welding by Melting Electrode." Materials Science Forum 575-578 (April 2008): 786–91. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.786.
Full textAbstract:
In this paper the processes of melting and transfer of an electrode metal to the molten pool, hydrodynamics of molten pool in controlled pulsed arc welding in carbon dioxide have been investigated. The process of pulsed arc welding with systematic short-circuits of the arc gap is realized by adaptive algorithms of pulsed control over main energetic parameters of welding - arc current and voltage, arc heated efficiency, peak short-circuiting current, which provide the dosage of energy for melting and transfer of every drop of an electrode metal, the control over fluidity of the weld pool. Physical and mathematical models describing such processes in CO2, original software have been developed. The results of physical simulation and mathematical modelling permit to determine the influence of energetic parameters of the process on the condition of the “power source – electrode – arc – molten pool” electrodynamic system at each moment of time.
31
Srisertpol, J., P. Srinakorn, A. Kheawnak, and K. Chamniprasart. "Estimation of Biogas Production from Shrimp Pond Sediment Using the Artificial Intelligence." Applied Mechanics and Materials 260-261 (December 2012): 695–700. http://dx.doi.org/10.4028/www.scientific.net/amm.260-261.695.
Full textAbstract:
A biogas production development increases renewable energy and reduces the environmental impact which is caused by carbon dioxide. Thisis important for energy and environmental planning in Thailand. The biogas production by anaerobic digestionproduces methane that can be used as renewable energy. This research was to study biogas production from the anaerobic digestion of shrimp pond sediment by the batch reaction, an estimation of the mathematical model using theArtificial Intelligence (AI) technique and the treatment of shrimp pond sediment.The mass balance principle to create mathematical modeling and decompositions of organic matter into biogas were used to compare the experimental dataincluding, temperature, pH, biogas flow rate and biochemical properties of the shrimp pond sediment. From the results, mathematical models can estimate the dynamic response of the biogas flow rate and factors that affectedthe biogas productions. The treatment of shrimp pond sediment by anaerobic digestion process could reduce TS, TDS, TSS, TVS, BOD, COD and ECby81-89%, 52-60%, 95-99%, 80-89%, 86-95% , 85-95% and 12-22 % respectively.
32
Milosevic, Svetlana, Zika Lepojevic, Zoran Zekovic, and Senka Vidovic. "Determination of extraction conditions of Ginkgo biloba L. leaves by supercritical CO2 using response surface methodology." Chemical Industry 65, no. 2 (2011): 147–57. http://dx.doi.org/10.2298/hemind101214010m.
Full textAbstract:
The effects of process parameters on the extraction of Ginkgo biloba L. leaves with supercritical carbon dioxide were investigated. The investigated parameters include particle size (mean particle diameter 0.19, 0.467 and 1.009 mm), solvent flow rate (1.5810-3, 3.2210-3 and 4.1610-3 kg CO2/min) and pressure (100-300 bar), which were obtained by the response surface methodology (RSM) under the following condition ranges: temperature 40-50-60?C, pressure 100-140-180 bar and extraction time of 2-3-4 h at the flow rate of 3.2210-3 kg/min. Based on the experimental results of kinetics of Ginkgo biloba leaves extraction with supercritical carbon dioxide, modeling of the extraction system of Ginkgo biloba-supercritical CO2 was done. Two mathematical models (Reverchon-Sesti Osseo and Sovov?) were applied to correlate the experimental data. RSM was applied to optimize the process parameters of supercritical carbon dioxide extraction of Ginkgo biloba L. leaves. A second-order polynomial response surface equation was developed indicating the effect of variables on Ginkgo biloba extraction yield. The statistical analysis of the experiment indicated that pressure (X1), extraction time (X3), the quadratic of temperature (X22), and the interaction between pressure and extraction time (X1X3), show significant effect on the extraction yield. The results showed that the data were adequately fitted into the second-order polynomial model. It was predicted that the optimum extraction process parameters within the experimental ranges would be the extraction temperature of 52.7?C, the pressure of 184.4 bar, and the extraction time of 3.86 h. Under these conditions, the predicted extraction yield is 2.39% (g/100 g drug).
33
Alnahdi, Amani, Ali Elkamel, Munawar A. Shaik, Saad A. Al-Sobhi, and Fatih S. Erenay. "Optimal Production Planning and Pollution Control in Petroleum Refineries Using Mathematical Programming and Dispersion Models." Sustainability 11, no. 14 (July 10, 2019): 3771. http://dx.doi.org/10.3390/su11143771.
Full textAbstract:
Oil refineries, producing a large variety of products, are considered as one of the main sources of air contaminants such as sulfur oxides (SOx), hydrocarbons, nitrogen oxides (NOx), and carbon dioxide (CO2), which are primarily caused by fuel combustion. Gases emanated from the combustion of fuel in an oil refinery need to be reduced, as it poses an environmental hazard. Several strategies can be applied in order to mitigate emissions and meet environmental regulations. This study proposes a mathematical programming model to derive the optimal pollution control strategies for an oil refinery, considering various reduction options for multiple pollutants. The objective of this study is to help decision makers select the most economic pollution control strategy, while satisfying given emission reduction targets. The proposed model is tested on an industrial scale oil refinery sited in North Toronto, Ontario, Canada considering emissions of NOx, SOx, and CO2. In this analysis, the dispersion of these air pollutants is captured using a screening model (SCREEN3) and a non-steady state CALPUFF model based on topographical and meteorological conditions. This way, the impacts of geographic location on the concentration of pollutant emissions were examined in a realistic way. The numerical experiments showed that the optimal production and pollution control plans derived from the proposed optimization model can reduce NOx, SOx, and CO2 emission by up to 60% in exchange of up to 10.7% increase in cost. The results from the dispersion models verified that these optimal production and pollution control plans may achieve a significant reduction in pollutant emission in a large geographic area around the refinery site.
34
Istadi, I., Nor Aishah Saidina Amin, and Mohd Nizam Ahmad Sanusi. "Optimization of Ni loading and operating conditions for carbon dioxide reforming of methane over NiO/CeO2 catalyst using response surface methodology." Jurnal Teknik Kimia Indonesia 4, no. 2 (October 2, 2018): 248. http://dx.doi.org/10.5614/jtki.2005.4.2.8.
Full textAbstract:
Optimization of Ni loading and operating conditions for carbon dioxide reforming of methane over NiO/CeO2 catalyst using response surface methodologyModelling and optimization of Carbon Dioxide Reforming of Methane (CORM) reaction over NiO/CeO2 catalyst were developed using Response Surface Methodology (RSM). Relationship between responses, i.e. CH, conversion, H2 and CO selectivities, and three independent variables, i.e. reactor temperature, CO2/CH4 ratio, and wt. % Ni in the CeO-supported catalyst, were presented as empirical mathematical models. The models showed a good fitting to the experimental data statistically. The NiO/CeO2 showed a potential catalyst for the CORM process, though some coking formations were found. The catalysts exhibited a promising catalytic performance with the unity H2/CO ratio in the product, high methane conversion, and low reverse water gas shift reaction. The reactor temperature, CO2/CH4 ratio, and wt. % Ni in the CeO2-supported catalyst being 840oC, 1, and 6.5%, respectively were suggested with respect to CH4 conversion, H2 and CO selectivity, and H2/CO ratio of 75.7%, 68.5%, 54.5%, and 1.03, respectively. Keywords: Carbon dioxide reforming of methane, NiO/CeO, catalyst, Response Surface Methodology AbstrakPermodelan dan optimisasi reaksi pembentukan kembali metana dengan karbondioksida (CORM) melalui katalis NiO/CeO2 telah dikembangkan dengan menggunakan Response Surface Methodology (RSM). Hubungan antara respon-respon (konversi CH, selektifitas H2 and CO) dengan tiga peubah tak bergantung (temperatur reaktor; rasio CO2/CH4, dan % berat Ni dalam katalis berpenyangga CeO) dinyatakan dalam model matematika empiris. Model empiris tersebut secara statistik menunjukkan korelasi yang baik terhadap data-data eksperimen. NiO/CeO2 tersebut menunjukkan sebuah katalis yang berpotensi untuk proses CORM. Katalis tersebut menunjukkan kinerja katalitik yang menjanjikan dengan rasio H2/CO mendekati satu dalam produk, konversi metana yang tinggi, dan reaksi reverse water gas shift yang rendah. Temperatur reactor 840oC, rasio CO2/CH4, 1, dan 6.5 wt. % Ni adalah direkomendasikan dengan konversi CH4 75.7%, selektifitas H2 68.5%, selektifitas CO 54.5%, dan rasio H2/CO 1.03. Kata Kunci: Pembentukan kembali metana dengan karbondioksida, Katalis NiO/CeO2, Response Surface Methodology
35
Kwiatkowski, Mirosław, Jarosław Serafin, Andy M. Booth, and Beata Michalkiewicz. "Computer Analysis of the Effect of Activation Temperature on the Microporous Structure Development of Activated Carbon Derived from Common Polypody." Materials 14, no. 11 (May 30, 2021): 2951. http://dx.doi.org/10.3390/ma14112951.
Full textAbstract:
This paper presents the results of a computer analysis of the effect of activation process temperature on the development of the microporous structure of activated carbon derived from the leaves of common polypody (Polypodium vulgare) via chemical activation with phosphoric acid (H3PO4) at activation temperatures of 700, 800, and 900 °C. An unconventional approach to porous structure analysis, using the new numerical clustering-based adsorption analysis (LBET) method together with the implemented unique gas state equation, was used in this study. The LBET method is based on unique mathematical models that take into account, in addition to surface heterogeneity, the possibility of molecule clusters branching and the geometric and energy limitations of adsorbate cluster formation. It enabled us to determine a set of parameters comprehensively and reliably describing the porous structure of carbon material on the basis of the determined adsorption isotherm. Porous structure analyses using the LBET method were based on nitrogen (N2), carbon dioxide (CO2), and methane (CH4) adsorption isotherms determined for individual activated carbon. The analyses carried out showed the highest CO2 adsorption capacity for activated carbon obtained was at an activation temperature of 900 °C, a value only slightly higher than that obtained for activated carbon prepared at 700 °C, but the values of geometrical parameters determined for these activated carbons showed significant differences. The results of the analyses obtained with the LBET method were also compared with the results of iodine number analysis and the results obtained with the Brunauer–Emmett–Teller (BET), Dubinin–Radushkevich (DR), and quenched solid density functional theory (QSDFT) methods, demonstrating their complementarity.
36
Costa, Fabíola, Terra Ortega, Sarah Arvelos, Marcos Traczynski, Edson Silva, Lúcio Cardozo-Filho, Hori Eponina, and Erika Watanabe. "Evaluation of supercritical carbon dioxide extraction to obtain bioactive compounds from Vernonia amygdalina Delile leaves." Chemical Industry and Chemical Engineering Quarterly 26, no. 2 (2020): 113–24. http://dx.doi.org/10.2298/ciceq190226030c.
Full textAbstract:
Literature reports have shown that supercritical extraction is a promising method to obtain bioactive compounds used to develop drugs based on natural products. This work investigated the yield, antioxidant activity, and phytochemical constituents of the extracts obtained from Vernonia amygdalina Delile leaves with supercritical CO2. The supercritical extraction was examined at temperatures of 40, 50 and 60?C and at pressures of 200 and 250 bar. The supercritical fluid extraction (SFE) method was compared with the classical Soxhlet using different solvents at atmospheric pressure. The overall yield obtained using SFE varied from 0.69 to 1.24%. The extraction conditions which favored the highest yield were 60?C and 250 bar. The overall SFE curves were fitted using three mathematical models. All of them were able to describe satisfactorily the extraction kinetics. Spline model presented the best fit to experimental data and was able to characterize constant and decreasing extraction rate periods. Extracts were characterized by gas chromatography coupled with mass spectrometry technique and some major components were identified. The antioxidant activity tests showed that the SFE extracts had low antioxidant activity exhibiting the estimated concentration of extract required to reduce 50% of the stable free radical DPPH (EC50) values to be between 622.62 and 937.88 ?g mL-1.
37
Tatomir, Alexandru, Alexandru-Nicolae Dimache, Iancu Iulian, and Martin Sauter. "Modelling of CO2 storage in geological formations with DuMux, a free-open-source numerical framework. A possible tool to assess geological storage of carbon dioxide in Romania." E3S Web of Conferences 85 (2019): 07002. http://dx.doi.org/10.1051/e3sconf/20198507002.
Full textAbstract:
Geological storage of carbon dioxide represents a viable solution to reduce the greenhouse gases in the atmosphere. Romania has initiatives to build a large-scale integrated CO2 capture and storage demonstration project and find suitable on-shore and off-shore CO2 storage locations. Numerical simulators are essential tools helping the design process. These simulators are required to be capable to represent the complex thermo-hydro-mechanical-chemical and biological phenomena accompanying the geological CO2 storage such as, multi-phase flow, compositional effects due to dissolution of CO2 into the brine, non-isothermal effects due to cold CO2 injection, geomechanical effects, mineralization at the reservoir-scale. These processes can be simulated accurately and efficiently with DuMux (www.dumux.org), a free- and open-source simulator. This article presents and reviews briefly these mathematical and numerical models.
38
Dhanya, G., T. S. Pranesha, Kamsali Nagaraja, D. M. Chate, and G. Beig. "Comprehensive Modeling of Seasonal Variation of Surface Ozone Over Southern Tropical City, Bengaluru, India." Nature Environment and Pollution Technology 21, no. 3 (September 1, 2022): 1269–77. http://dx.doi.org/10.46488/nept.2022.v21i03.033.
Full textAbstract:
Surface ozone (O3) is an important pollutant. In this study we investigated the effects of precursor gases on the difference in ozone concentration utilizing various statistical methods like Multiple Linear Regression (MLR), Principal Component Regression (PCR), Artificial Neural Network (ANN), and Principal Component and Artificial Neural Network (PC-ANN) in conjunction with meteorological parameters for forecasting. The pollutants ozone (O3), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), oxides of nitrogen (NOx), and the meteorological parameters temperature (temp), relative humidity (RH), solar radiation (SR), wind speed (WS) and wind direction (WD) observed during 2019 are taken as inputs for MLR, PCR, ANN, and PCANN. The mathematical models obtained from the numerical analysis showed that O3 concentration was significantly affected by the CO, NO, NO2, NOX, temp, RH, SR, WS, and WD factors. PCR model’s regression coefficient was lower than the MLR model, but the same for ANN and PCANN models was much better in all the seasons than the linear models such as MLR and PCR. The efficiency of all methods is inspected using several performance metrics.
39
Asim Mushtaq, Asim Mushtaq, and Hilmi Mukhtar and Azmi Mohd Shariff Hilmi Mukhtar and Azmi Mohd Shariff. "Modelling for Gas Transport in Enhanced Polymeric Blend Membrane." Journal of the chemical society of pakistan 41, no. 4 (2019): 613. http://dx.doi.org/10.52568/000772/jcsp/41.04.2019.
Full textAbstract:
The main aim of this research work is to develop a model of carbon dioxide (CO2) separation from natural gas by using membrane separation technology. This study includes the transport mechanism of the porous membrane. The fundamental theories of diffusion, poiseuille (viscous) flow, Knudsen diffusion and surface diffusion are used. The developed model of incorporating three diffusion mechanisms to be modified for modeling of polymeric blends towards membrane selectivity and permeability. For the purpose of assessing the gas permeance using the theoretical models, the experimental data taken from CO2 permeance in the PSU/PVAc (85/15) wt. % /DEA enhanced polymeric blend membrane was considered. The results obtained from modified Cho Empirical model of total gas permeance showed the least error as compared to other models. The modified Cho Empirical mathematical models were extended by blending factor to predict CO2 gas molecule transport in Enhanced Polymeric Blend Membrane (EPBM) to obtain precise theoretical values that are close to the experimental values. The Extended modified Cho Empirical model validation demonstrated the ability to predict CO2 permeance with reasonable accuracy.
40
Hansen, James, Makiko Sato, Gary Russell, and Pushker Kharecha. "Climate sensitivity, sea level and atmospheric carbon dioxide." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 2001 (October 28, 2013): 20120294. http://dx.doi.org/10.1098/rsta.2012.0294.
Full textAbstract:
Cenozoic temperature, sea level and CO 2 covariations provide insights into climate sensitivity to external forcings and sea-level sensitivity to climate change. Climate sensitivity depends on the initial climate state, but potentially can be accurately inferred from precise palaeoclimate data. Pleistocene climate oscillations yield a fast-feedback climate sensitivity of 3±1 ° C for a 4 W m −2 CO 2 forcing if Holocene warming relative to the Last Glacial Maximum (LGM) is used as calibration, but the error (uncertainty) is substantial and partly subjective because of poorly defined LGM global temperature and possible human influences in the Holocene. Glacial-to-interglacial climate change leading to the prior (Eemian) interglacial is less ambiguous and implies a sensitivity in the upper part of the above range, i.e. 3–4 ° C for a 4 W m −2 CO 2 forcing. Slow feedbacks, especially change of ice sheet size and atmospheric CO 2 , amplify the total Earth system sensitivity by an amount that depends on the time scale considered. Ice sheet response time is poorly defined, but we show that the slow response and hysteresis in prevailing ice sheet models are exaggerated. We use a global model, simplified to essential processes, to investigate state dependence of climate sensitivity, finding an increased sensitivity towards warmer climates, as low cloud cover is diminished and increased water vapour elevates the tropopause. Burning all fossil fuels, we conclude, would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change.
41
Рудольф Александрович, Вирц,, and Папин, Александр Алексеевич. "Modelling the storage of carbon dioxide in viscoelastic porous medium." Вычислительные технологии, no. 6 (December 23, 2022): 4–18. http://dx.doi.org/10.25743/ict.2022.27.6.002.
Full textAbstract:
Предложена математическая модель фильтрации газа в среде с переменной пористостью. В двумерном случае определяющая система уравнений в предположении малости скорости твердой фазы сведена к параболическому уравнению для эффективного давления среды и уравнению первого порядка для пористости. Проведено численное исследование полученной начально-краевой задачи. Исследовано несколько вариантов параметров нагнетания углекислого газа в пласт с малой начальной пористостью. В ходе численных расчетов определены оптимальные варианты нагнетания газа для его хранения в геологической среде в долгосрочной перспективе. Purpose. This paper presents a model that describes gas filtration in a poroelastic medium. The initial-boundary problem describing carbon dioxide injection into a geological environment is formulated. The purpose of the research is numerical solution of the initial-boundary value problem and the analysis of results of the presented numerical simulation. Methodology. The assumption that the solid phase velocity is small allows reducing the original system of constitutive two-dimensional equations to two equations for the effective pressure and porosity. For numerical implementation, the scheme of alternating directions and the Runge - Kutta method of the fourth order of accuracy are used. A parabolic equation for the effective pressure was solved using the stabilizing correction scheme and the explicit scheme for the heat equation. Grid convergence is tested by a series of computational experiments on sequences of refined grids. Findings. Several options for gas injection are considered. Optimal parameters for storing carbon dioxide in geological formations in the long term have been found. Originality/value. Taking into account the poroelastic properties and the assumption of the deformability of the solid phase of the medium allows making new predictions of the distribution of carbon dioxide in geological media. The research results can be useful for improving existing carbon dioxide storage models and for developing new ones.
42
Kravchenko, Alexander, Boris Gerasimov, Evgeniy Loskutov, Alexander Okrugin, Larisa Galenchikova, and Vasily Beryozkin. "Statistical Models of the Distribution of Chemical Elements in Precambrian Rocks of the Siberian Craton." Separations 8, no. 3 (February 25, 2021): 23. http://dx.doi.org/10.3390/separations8030023.
Full textAbstract:
Natural chemical systems are an excellent object for studying the properties of various elements. The most diverse and informative geological complexes are crystalline rocks of the Precambrian. These rocks are exposed near the northern and southern margins of the Siberian craton. The chemical composition of rocks, the contents of impurity elements, and metals were studied by us using chemical and spectral analysis methods. Microprobe studies were performed. Using regression and multivariate statistical methods of analysis, the regularities of the distribution of chemical elements were found. It is shown that the distribution of precious metals and carbon dioxide in rocks is attributed to their chemical properties and comparable with close in-chemical properties’ rock-forming elements. It is found that the factor analysis reflects the uniform regularities of the distribution of elements in different regions and rocks. These regularities are similar on macro and micro levels. Comparison of the distribution patterns with the results of geochemical and petrological studies of other authors shows the leading role of the redox potential and acidity of the environment in the formation of rocks and minerals. The role of mathematical statistics for solving problems of chemical petrology and chemical systems analysis is underlined.
43
Zhuravleva, V. V., A. S. Manicheva, and A. A. Martynova. "Analysis of the Mathematical Model of Photosynthesis in Protected Ground." Izvestiya of Altai State University, no. 4(114) (September 9, 2020): 86–91. http://dx.doi.org/10.14258/izvasu(2020)4-13.
Full textAbstract:
The problem of predicting changes in the intensity of photosynthesis associated with changes in the lighting mode, atmospheric carbon dioxide concentration, and the temperature is urgent. Appropriate models can help choose the optimal mode of growing plants in protected soil, as well as serve as a basis for predicting the consequences of global climate change. It is noted that in the conditions of protected soil, the most significant factor is the illumination of plants.
The aim of the research is to construct an algorithm for additional illumination of plants in protected ground conditions based on a mathematical model of photosynthesis. The authors introduced the value of the efficiency of additional illumination and studied its dependence on the coefficient of light transmission of the roof.
The solution of the main task of the study is achieved by the fact that the light mode in protected ground structures is carried out on the basis of additional illumination to the ideal (optimal) for this type of plant. The entered value of the efficiency of additional illumination shows what energy costs will be for the production of photosynthesis products and, as a result, allows estimation of the economic costs.
The considered method of artificial lighting of plants makes it possible to effectively use both sunlight and artificial lighting, providing an optimal lighting mode all year round, and allows to increase the intensity of photosynthesis by 50-80 %.
44
Antonenko, Mikhail, Tatiana Guguchkina, Olga Antonenko, Alla Abakumova, and Anton Khrapov. "Research of mechanisms of transformation and removal of antibiotics from wine by sorbents of different nature." BIO Web of Conferences 34 (2021): 06006. http://dx.doi.org/10.1051/bioconf/20213406006.
Full textAbstract:
On the basis of own research, the authors experimentally confirmed the reliability of the hypothesis expressed in the scientific literature about the possibility of effective removal of nisin and natamycin from wines and wine materials. New knowledge has been obtained about the possible mechanisms of sorption of nisin and natamycin through the use of sorbents of various nature. Comparative experimental data on the interaction of sorbents with antibiotics in wines are presented. In this work, experimental data are presented that indicate different efficiency of antibiotic removal during wine processing, which is due to the structure and properties of sorbents. It has been shown that the sorption capacity of sorbents for natamycin and nisin decreases in the series: activated carbon, bentonite, and colloidal silicon dioxide. Mathematical models have been obtained for decontamination of antibiotics from wine production using sorbents of various nature.
45
Nguyen, V. H., A. S. Filimono, B. V. Peshnev, and A. I. Nikolaev. "OXIDATION OF DISPERSE CARBON MATERIALS." Fine Chemical Technologies 13, no. 3 (June 28, 2018): 57–63. http://dx.doi.org/10.32362/24106593-2018-13-3-57-63.
Full textAbstract:
It is proposed to consider the process of carbon materials oxidative activation from the positions of topochemical reactions involving chemisorption of the activating agent (oxidizer) on the material surface active centers followed by chemical interaction. Such an approach makes it possible to control the process of creating a carbon material with the desired characteristics of the porous space. It is assumed that the oxidizer chemisorption active centers are amorphous carbon, which is localized on the material crystallites boundaries. The change in the length of these boundaries will lead to a change in the process rate. It is shown that the number of such active centers on the carbon material surface depends on the size of the crystallites. It will have a significant impact not only on the rate of activation, but also on the possibility of the process flow on the surface or with porosity formation. Mathematical models describing the carbon sample specific surface changing in the oxidation process are proposed. They allow quantifying the proportion of carbon that is oxidized on the sample surface or with pores formation, as well as quantifying the number of pores. It is shown that the ratio of pore formation and surface oxidation processes depends on the oxidation temperature, the oxidizer nature and its flow rate. The proportion of porosity formation decreases with the increase in the oxidant flow rate and the increase in temperature. It was experimentally shown that in order to obtain a material with a more developed porous space and a high specific surface it is preferable to use carbon dioxide as an oxidizing agent.
46
Biszczanik, Aleksandra, Jan Górecki, Mateusz Kukla, Krzysztof Wałęsa, and Dominik Wojtkowiak. "Experimental Investigation on the Effect of Dry Ice Compression on the Poisson Ratio." Materials 15, no. 4 (February 18, 2022): 1555. http://dx.doi.org/10.3390/ma15041555.
Full textAbstract:
In the processing of waste materials, attention must be given to the efficient use of energy. The pelletization of dry ice is a good example of such processes. A literature review shows that in the pelletizers available on the market, the force applied in the process is excessive. As a result, the efficiency of the utilization of inputs, including electricity and carbon dioxide, is at a very low level. This article presents the results of experimental research on the effect of the degree of dry ice compression on the value of the Poisson ratio. The first part of this article presents the research methodology and a description of the test stand, developed specifically for this research, bearing in mind the unique properties of carbon dioxide in the solid state. The results presented show the behavior of dry ice during compression in a rectangular chamber for different final densities of the finished product. As a result, it is possible to determine the values of the Poisson ratio as a function of density, using for this purpose four mathematical models. The findings of this research may be useful for research work focused on the further development of this process, such as by using the Drucker–Prager/Cap numerical model to optimize the geometric parameters of the parts and components of the main unit of the machine used in the extrusion process of dry ice.
47
Rotskoff, Grant M., and Phillip L. Geissler. "Robust nonequilibrium pathways to microcompartment assembly." Proceedings of the National Academy of Sciences 115, no. 25 (June 4, 2018): 6341–46. http://dx.doi.org/10.1073/pnas.1802499115.
Full textAbstract:
Cyanobacteria sequester photosynthetic enzymes into microcompartments which facilitate the conversion of carbon dioxide into sugars. Geometric similarities between these structures and self-assembling viral capsids have inspired models that posit microcompartments as stable equilibrium arrangements of the constituent proteins. Here we describe a different mechanism for microcompartment assembly, one that is fundamentally nonequilibrium and yet highly reliable. This pathway is revealed by simulations of a molecular model resolving the size and shape of a cargo droplet and the extent and topography of an elastic shell. The resulting metastable microcompartment structures closely resemble those of carboxysomes, with a narrow size distribution and faceted shells. The essence of their assembly dynamics can be understood from a simpler mathematical model that combines elements of classical nucleation theory with continuum elasticity. These results highlight important control variables for achieving nanoscale encapsulation in general and for modulating the size and shape of carboxysomes in particular.
48
Zvada, Branislav, Radovan Nosek, Peter Ďurčanský, Andrej Kapjor, and Nikola Kantová Čajová. "Numerical Predictive Combustion Model of Hydrogen Enriched Natural Gas." MATEC Web of Conferences 369 (2022): 03003. http://dx.doi.org/10.1051/matecconf/202236903003.
Full textAbstract:
Hydrogen was established as one of the main pillars of energy stability in the Europe Union. One of the ways how to achieve this goal is natural gas enriched with hydrogen. Due to this is very important to know the properties of this fuel and its behaviour during combustion. The main scope of the research is to provide a better understanding of the emissions, efficiency, and performance of the heat source when combusting hydrogen and gas fuel mixture. In this paper is described hydrogen characteristics, hydrogen fuel preparation, an overview of gas fuel combustion in gas appliances with the hydrogen additive, a mathematical model for the combustion process estimation. In the conclusion, multiple predictive models were compared. We can state that, based on calculations of a numerical predictive model, as hydrogen concentration raised emissions, as nitrogen, carbon dioxide, wet exhaust, and water, are decreasing.
49
Domján, Gyula, Károly J. Kaffka, János M. Jákó, and István T. Vályi-Nagy. "Rapid Analysis of Whole Blood and Blood Serum Using near Infrared Spectroscopy." Journal of Near Infrared Spectroscopy 2, no. 2 (March 1994): 67–78. http://dx.doi.org/10.1255/jnirs.33.
Full textAbstract:
In the present study we describe the relationship between laboratory values obtained with routinely used laboratory analytical methods and near infrared (NIR) spectral data of 126 whole blood and 228 blood serum samples. Spectra were measured with a SPECTRALYZER 1025 (PMC) computerised research analyser. The relationship among laboratory data and values of the second derivative of the log (1/ R) spectra measured at different wavelengths was determined by multiple linear regression (MLR) using three and four term linear summation equations, principal component regression (PCR) and partial least-squares (PLS) regression methods. Along with examples for qualitative detection of protein and lipid in human sera, as well as distinction of albumin and globulin dissolved in physiological saline solution, we describe mathematical models and evaluate their performance for the determination of protein and beta-lipoprotein (β-LP) content of serum as well as oxygen saturation and carbon dioxide pressure in whole blood. Validation of our results yielded a standard error of performance (SEP) of 2.47 g L−1 for protein content and 0.79 TU for β-LP content in blood serum, whereas SEP values of 5.41% for oxygen saturation and 5.27 mm Hg for carbon dioxide pressure in whole blood were found. Our results presented in this preliminary study indicate that NIR measurements can be related to analytical data of whole blood and serum. NIR spectroscopy is a rapid, accurate, cost effective method for determining quality parameters of whole blood and serum and might be a promising new tool in the field of automated clinical laboratory analysis.
50
Kiehl, Jeffrey T., and Christine A. Shields. "Sensitivity of the Palaeocene–Eocene Thermal Maximum climate to cloud properties." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 2001 (October 28, 2013): 20130093. http://dx.doi.org/10.1098/rsta.2013.0093.
Full textAbstract:
The Palaeocene–Eocene Thermal Maximum (PETM) was a significant global warming event in the Earth's history (approx. 55 Ma). The cause for this warming event has been linked to increases in greenhouse gases, specifically carbon dioxide and methane. This rapid warming took place in the presence of the existing Early Eocene warm climate. Given that projected business-as-usual levels of atmospheric carbon dioxide reach concentrations of 800–1100 ppmv by 2100, it is of interest to study past climates where atmospheric carbon dioxide was higher than present. This is especially the case given the difficulty of climate models in simulating past warm climates. This study explores the sensitivity of the simulated pre-PETM and PETM periods to change in cloud condensation nuclei (CCN) and microphysical properties of liquid water clouds. Assuming lower levels of CCN for both of these periods leads to significant warming, especially at high latitudes. The study indicates that past differences in cloud properties may be an important factor in accurately simulating past warm climates. Importantly, additional shortwave warming from such a mechanism would imply lower required atmospheric CO 2 concentrations for simulated surface temperatures to be in reasonable agreement with proxy data for the Eocene.