Journal articles on the topic 'Stream conservation Mathematical models'
To see the other types of publications on this topic, follow the link: Stream conservation 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 'Stream conservation 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
ALI MUNZER, SULEIMAN, D. S. BEGLYAROV, and R. R. SHAKIROV. "FEATURES AND ANALYSIS OF STUDIES OF FISH PROTECTION COMPLEX FOR WATER RECEIVERS OF LARGE HIGH-PRESSURE HYDROELECTRIC POWER PLANTS." Prirodoobustrojstvo, no. 2 (2022): 86–93. http://dx.doi.org/10.26897/1997-6011-2022-2-86-93.
Full textAbstract:
Development of effective fish protection measures at water intakes is one of the main directions of fish resources conservation and reproduction in inland water bodies of the country. Its complexity is associated with the involvement of many related disciplines: ichthyology, physiology, hydrobiology, ecology, hydraulics, hydrology, etc. In the process of solving the problem of standardization of information to be used for creating mathematical models for forecasting potential impact of water intakes with fish protection on aquatic ecosystem. The article gives a review of the research on the technology of aquatic bioresources (ABR) conservation, conducted by JSC «Institute Hydroproject» (Moscow) together with LLC «Hydrotechnika» (Sochi), the basic provisions of modeling methodology are considered; the results of mathematical modeling of currents in the upstream in the area of hydraulic units, spillways and rockfi ll dam at Boguchanskaya HPP; results of experimental studies of stream generators and biohydraulic modeling. The assessment of the conducted research is given.
2
Bondarenko, A., M. Savin, O. Supotnitskaya, and L. Yantseva. "ON COMBINED BURNING RATE OF LIQUID SODIUM STREAM AND POOL." PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES: NUCLEAR AND REACTOR CONSTANTS 2019, no. 1 (March 26, 2019): 224–29. http://dx.doi.org/10.55176/2414-1038-2019-1-224-229.
Full textAbstract:
Sodium fires with heat and fume release often happen at coolant circuit rupture of sodium fast reactor. At nuclear power plant with the sodium fast reactor the more probable scenario of sodium fire is considered burning of falling from damaged pipeline liquid sodium stream and the pool formed under it. The simple models for sodium fire which contains minimum of phenomenological parameters and gives the opportunity to get the upper limits of heat generation and amount of aerosol generated at sodium fire are more preferable. The physical and mathematical model for estimation a combined burning rate of the freely falling liquid sodium stream and the pool formed under it is proposed. The model is based on the laws of energy and mass conservation, the empiric correlations for burning rate of stream and pool sodium and assumption that pool depth cannot be less than equilibrium. The equilibrium pool depth depends on surface tension of liquid sodium. The probable heat transfer techniques for steam-phase and heterogeneous burning of metal are discussed. The experimental data of the Monju's sodium fire imitation are used for verification of the model presented. Good agreement between experimental and calculated data is observed.
3
Timakova, R. T. "Adaptive modeling of experimental conditions in the processing of food products (chilled fish) by the flow of accelerated electrons." Proceedings of the Voronezh State University of Engineering Technologies 83, no. 1 (June 3, 2021): 17–22. http://dx.doi.org/10.20914/2310-1202-2021-1-17-22.
Full textAbstract:
The use of mathematical modeling in various branches of the food industry as an effective tool for the policy of resource conservation of food systems is an innovative solution in the field of improving the efficiency of existing food production technologies based on established patterns in the production process. The issues of operational quality control in the process of processing food products with a stream of accelerated electrons in the absence of radiation doses regulated by standards, except for certain types of spices, to ensure the safety and quality of food products, in particular chilled fish, require a constructive approach with the general predictability of technological parameters in specialized radiation centers – operators of the irradiator. It was found that the dose absorbed by the samples of common carp scales with a high degree of correlation of 0.94 depends on the actual radiation dose and increases to 7.51±0.04 kGy when irradiated with a dose of 12 kGy or 25.9 times compared to samples treated with a stream of accelerated electrons with a radiation dose of 1 kGy. It is revealed that the operational quality is determined by the reproducibility of the results under the established conditions of the production processing process. As a result of experimental testing, mathematical models of various types were developed to predict the absorbed dose from experimental conditions on the example of samples of chilled carp scales: polynomial, 3D-graph and arccos. The practical significance is determined by the possibility of designing experimental conditions for processing chilled fish with a stream of accelerated electrons without performing trial processing of small batches of food products in radiation centers and using emitters as a model for technological runs.
4
Udalov, A. A., M. Yu Uleysky, and M. V. Budyansky. "Analysis of Stationary Points and Bifurcations of a Dynamically Consistent Model of a Two-dimensional Meandering Jet." Nelineinaya Dinamika 18, no. 4 (2022): 0. http://dx.doi.org/10.20537/nd220802.
Full textAbstract:
A dynamically consistent model of a meandering jet stream with two Rossby waves obtained using the law of conservation of potential vorticity is investigated. Stationary points are found in the phase space of advection equations and the type of their stability is determined analytically. All topologically different flow regimes and their bifurcations are found for the stationary model (taking into account only the first Rossby wave). The results can be used in the study of Lagrangian transport, mixing, and chaotic advection in problems of cross-frontal transport in geophysical flows with meandering jets.
5
Dobrynin, Ye, and V. Davydov. "SIMULATION MODEL OF THE INFORMATION TECHNOLOGY FOR THE TECHNICAL DIAGNOSIS OF THE IMPULSE HEAT MACHINE." Odes’kyi Politechnichnyi Universytet Pratsi 2, no. 61 (2020): 95–103. http://dx.doi.org/10.15276/opu.2.61.2020.11.
Full textAbstract:
A simulation model of the information technology for the technical diagnosis of the impulse heat machine has been developed and studied. The model incorporates such mathematical models as barrel energy; ballistic wave parameters; pressure of powder gases blasting from the barrel face behind the shell and the shot blast and determination of its attenuation rate. The information model enables to obtain parameters of the ballistic wave that accompanies an shot. A simplified mathematical model allows of determining the oblique shock inclination angle to the stream speed depending on Mach number which is represented by the two-dimensional flow wedge. The model of powder gas pressure blasting from the barrel face behind the shell is based on the energy conservation law for the compresses powder gases and makes it possible to avoid solution of the complicated modified Lagrange problem. While the shot blast propagates, at the initial stage it is possible that this blast reaches the record point earlier than the ballistic wave. Such phenomenon can be avoided by selecting a proper angle. The adopted mathematical model determines the shot blast propagation law and allows of evaluating the shot blast speed attenuation. The barrel energy model was based on the solution of the inverse problem of pyrostatics by determining a composition of the combustion gas of the shot. The applied approach provided for use of the model that describes combustion of the fuel and oxidizer mixture. The peculiarity is a necessity to know composition of all components of the arbitrary mixture. The limitation is a necessity that all components are gaseous. The considered case needs to develop a combustion model of a single-component solid substance (nitrocellulose powder) that provides for a possibility to vary the composition of its active part because of its degradation with time.
6
Lutz, Stefanie R., Ype van der Velde, Omniea F. Elsayed, Gwenaël Imfeld, Marie Lefrancq, Sylvain Payraudeau, and Boris M. van Breukelen. "Pesticide fate on catchment scale: conceptual modelling of stream CSIA data." Hydrology and Earth System Sciences 21, no. 10 (October 18, 2017): 5243–61. http://dx.doi.org/10.5194/hess-21-5243-2017.
Full textAbstract:
Abstract. Compound-specific stable isotope analysis (CSIA) has proven beneficial in the characterization of contaminant degradation in groundwater, but it has never been used to assess pesticide transformation on catchment scale. This study presents concentration and carbon CSIA data of the herbicides S-metolachlor and acetochlor from three locations (plot, drain, and catchment outlets) in a 47 ha agricultural catchment (Bas-Rhin, France). Herbicide concentrations at the catchment outlet were highest (62 µg L−1) in response to an intense rainfall event following herbicide application. Increasing δ13C values of S-metolachlor and acetochlor by more than 2 ‰ during the study period indicated herbicide degradation. To assist the interpretation of these data, discharge, concentrations, and δ13C values of S-metolachlor were modelled with a conceptual mathematical model using the transport formulation by travel-time distributions. Testing of different model setups supported the assumption that degradation half-lives (DT50) increase with increasing soil depth, which can be straightforwardly implemented in conceptual models using travel-time distributions. Moreover, model calibration yielded an estimate of a field-integrated isotopic enrichment factor as opposed to laboratory-based assessments of enrichment factors in closed systems. Thirdly, the Rayleigh equation commonly applied in groundwater studies was tested by our model for its potential to quantify degradation on catchment scale. It provided conservative estimates on the extent of degradation as occurred in stream samples. However, largely exceeding the simulated degradation within the entire catchment, these estimates were not representative of overall degradation on catchment scale. The conceptual modelling approach thus enabled us to upscale sample-based CSIA information on degradation to the catchment scale. Overall, this study demonstrates the benefit of combining monitoring and conceptual modelling of concentration and CSIA data and advocates the use of travel-time distributions for assessing pesticide fate and transport on catchment scale.
7
Marcinkowski, Paweł, and Dorota Mirosław-Świątek. "Modelling of climate change impact on flow conditions in the lowland anastomosing river." PeerJ 8 (June 23, 2020): e9275. http://dx.doi.org/10.7717/peerj.9275.
Full textAbstract:
The progressive degradation of freshwater ecosystems worldwide requires action to be taken for their conservation. Nowadays, protection strategies need to step beyond the traditional approach of managing protected areas as they have to deal with the protection or recovery of natural flow regimes disrupted by the effects of future climate conditions. Climate change affects the hydrosphere at catchment scale altering hydrological processes which in turn impact hydrodynamics at the river reach scale. Therefore, conservation strategies should consider mathematical models, which allow for an improved understanding of ecosystem functions and their interactions across different spatial and temporal scales. This study focuses on an anastomosing river system in north-eastern Poland, where in recent decades a significant loss of the anabranches has been observed. The objective was to assess the impact of projected climate change on average flow conditions in the anastomosing section of the Narew River. The Soil and Water Assessment Tool (SWAT software) for the Narew catchment was coupled with the HEC-RAS one-dimensional unsteady flow model. The study looked into projected changes for two future time horizons 2021–2050 and 2071–2100 under the Representative Concentration Pathway 4.5 using an ensemble of nine EURO-CORDEX model scenarios. Results show that low flow conditions in the anastomosing section of the Narew National Park will remain relatively stable in 2021–2050 compared to current conditions and will slightly increase in 2071–2100. Duration of low flows, although projected to decrease on an annual basis, will increase for August–October, when the loss on anastomoses was found to be the most intense. Hydraulic modeling indicated extremely low flow velocities in the anastomosing arm (<0.1 m/s) nowadays and under future projections which is preferable for in-stream vegetation development and their gradual sedimentation and closure.
8
An, Chenge, Andrew J. Moodie, Hongbo Ma, Xudong Fu, Yuanfeng Zhang, Kensuke Naito, and Gary Parker. "Morphodynamic model of the lower Yellow River: flux or entrainment form for sediment mass conservation?" Earth Surface Dynamics 6, no. 4 (November 6, 2018): 989–1010. http://dx.doi.org/10.5194/esurf-6-989-2018.
Full textAbstract:
Abstract. Sediment mass conservation is a key factor that constrains river morphodynamic processes. In most models of river morphodynamics, sediment mass conservation is described by the Exner equation, which may take various forms depending on the problem in question. One of the most widely used forms of the Exner equation is the flux-based formulation, in which the conservation of bed material is related to the stream-wise gradient of the sediment transport rate. An alternative form of the Exner equation, however, is the entrainment-based formulation, in which the conservation of bed material is related to the difference between the entrainment rate of bed sediment into suspension and the deposition rate of suspended sediment onto the bed. Here we represent the flux form in terms of the local capacity sediment transport rate and the entrainment form in terms of the local capacity entrainment rate. In the flux form, sediment transport is a function of local hydraulic conditions. However, the entrainment form does not require this constraint: only the rate of entrainment into suspension is in local equilibrium with hydraulic conditions, and the sediment transport rate itself may lag in space and time behind the changing flow conditions. In modeling the fine-grained lower Yellow River, it is usual to treat sediment conservation in terms of an entrainment (nonequilibrium) form rather than a flux (equilibrium) form, in consideration of the condition that fine-grained sediment may be entrained at one place but deposited only at some distant location downstream. However, the differences in prediction between the two formulations have not been comprehensively studied to date. Here we study this problem by comparing the results predicted by both the flux form and the entrainment form of the Exner equation under conditions simplified from the lower Yellow River (i.e., a significant reduction of sediment supply after the closure of the Xiaolangdi Dam). We use a one-dimensional morphodynamic model and sediment transport equations specifically adapted for the lower Yellow River. We find that in a treatment of a 200 km reach using a single characteristic bed sediment size, there is little difference between the two forms since the corresponding adaptation length is relatively small. However, a consideration of sediment mixtures shows that the two forms give very different patterns of grain sorting: clear kinematic waves occur in the flux form but are diffused out in the entrainment form. Both numerical simulation and mathematical analysis show that the morphodynamic processes predicted by the entrainment form are sensitive to sediment fall velocity. We suggest that the entrainment form of the Exner equation might be required when the sorting process of fine-grained sediment is studied, especially when considering relatively short timescales.
9
Pereira, Marcelo Divino Ribeiro, and João Batista Pereira Cabral. "Perda de Solo no Alto Curso das Bacias Hidrográficas dos Ribeirões Taquaruçu Grande e Taquaruçuzinho, Palmas (TO)." Revista Brasileira de Geografia Física 14, no. 1 (April 20, 2021): 332. http://dx.doi.org/10.26848/rbgf.v14.1.p332-339.
Full textAbstract:
A aplicação de modelos matemáticos na análise da perda de solo em bacias hidrográficas ganhou atenção, nos anos de 1960 e 1970, a partir da análise integrada da paisagem. Nesse contexto, a Equação Universal de Perda de Solo (EUPS) se destaca como um dos modelos mais utilizados mundialmente no conhecimento dos processos erosivos e no planejamento ambiental. Diante disso, este estudo tem por objetivo estimar as perdas de solos nas bacias hidrográficas dos córregos Macacão e Mutum, localizadas no município de Palmas (TO). Os resultados demonstram que as áreas estudadas sofreram com um alto poder de erosividade (R) ao longo dos anos 1995 a 2019, com valores entre 12,188 a 12,319 t/ha MJ-1 mm-1. Quanto ao solo, o Neossolo Litólico Distrófico (RLD) apresenta o maior valor de erodibilidade (K), 0,049 t/ha MJ-1 mm-1.No que tange ao fator topográfico (LS), cerca de 80% das áreas das bacias mostram valores de LS considerados baixos, situados entre 0,029 a 1,86, e 1,86 a 4,30. Já para o fator relacionado ao uso e manejo do solo e às práticas conservacionistas (CP), as áreas mais suscetíveis ao processo erosional diz respeito às classes de pastagem e queimadas. Desta forma, observa-se que as classes de erosão hídrica nas bacias são consideradas moderada, grave e muito grave pelo estudo da Food and Agriculture Organization (FAO) de 1984, ainda que represente somente 19% da área da bacia do Macacão e 24% da bacia do Córrego Mutum. Loss of soil in the high course of hydrographic basins of ribeirões Taquaruçu Grande and Taquaruçuzinho, Palmas (TO) A B S T R A C TThe application of mathematical models in the analysis of soil loss in watersheds gained attention in the 1960s and 1970s from the integrated analysis of the landscape. In this context, the Universal Soil Loss Equation (EUPS) stood out as one of the most used models worldwide in the knowledge of erosion processes and in environmental planning. Therefore, this study aims to estimate soil losses in the hydrographic basins of the Macacão and Mutum streams, located in the municipality of Palmas (TO). The results demonstrate that the studied areas suffered from a high power of erosivity (R) over the years 1995 to 2019, with values between 12.188 to 12.319 t/ha MJ-1 mm-1. As for the soil, the Neosol Litolic Dystrophic (RLD) has the highest erodibility value (K), 0.049 t/ha MJ-1 mm-1. Regarding the topographic factor (LS), about 80% of the basin areas show LS values considered low, situated between 0.029 to 1.86, and 1.86 to 4.30. As for the factor related to the use and management of soil and conservation practices (CP), the areas most susceptible to the erosion process concern the grazing and burning classes. Thus, it is observed that the classes of water erosion in the basins are considered moderate, severe and very severe by the Food and Agriculture Organization (FAO) study of 1984, although it represents only 19% of the area of the Macacão basin and 24% of the Mutum Stream basin.Keywords: Water erosion. Hydrographic basin. USLE.
10
Vasarevičius, Saulius, Asta Mineikaitė, and Petras Vaitiekūnas. "INVESTIGATION INTO HEAVY METALS IN STORM WASTEWATER FROM VILNIUS ŽIRMŪNAI DISTRICT AND POLLUTANTITS SPREAD MODEL IN NERIS RIVER." JOURNAL OF ENVIRONMENTAL ENGINEERING AND LANDSCAPE MANAGEMENT 18, no. 3 (September 30, 2010): 242–49. http://dx.doi.org/10.3846/jeelm.2010.28.
Full textAbstract:
The paper discusses investigation into uncleaned storm wastewater pollution with heavy metals in Vilnius Žirmūnai district. The goal is to determine the dependency of storm wastewater pollution with heavy metals on transport intensity. After determining this dependency, sweeps from street points is experimentally studied with the most intensive transport flows. As the street sweeps together with storm wastewater are both outflow from streets and through outflow pipes directly to the Neris, heavy metals in the outflow pipe sludge are also studied for each pool. The following heavy metals have been experimentally studied: Pb, Mn, Cr, Zn, Cu, Ni. The flame atomic absorption spectrometry method was used. The process of analysis is explained in short and its results are provided. A mathematical model by Phoenics 3.5 version program showing the distribution of heavy metals in the Neris river stream is made on the basis of the results received. Santrauka Nagrinejama nevalomu lietaus nuoteku tarša sunkiaisiais metalais Vilniaus Žirmūnu rajone. Siekiant nustatyti ryši tarp lietaus nuoteku užterštumo sunkiaisiais metalais nuo transporto eksperimentiškai tiriamos sašlavos nuo gatviu, kuriuos su lietumi išplaunamos i upe. Taip pat tiriami sunkieji metalai iš lietaus ištekamuju vamzdžiu i Neri. Eksperimentiškai nagrinejami šie sunkieji metalai: Pb, Mn, Cr, Zn, Cu, Ni. Tam panaudotas liepsnos absorbcijos spektrometrinis metodas. Trumpai aptariamas analizes procesas ir pateikiami tyrimu rezultatai. Remiantis gautais rezultatais sudaromas matematinis teršalu sklaidos modelis Neries upes tekmeje taikant Phoenics 3.5 programa. Резюме Исследуется загрязнение неочищаемых дождевых стоков тяжелыми металлами в районе Жирмунай г. Вильнюса. Для определения степени загрязнения дождевых стоков тяжелыми металлами от транспорта экспериментально исследовался мусор с улиц, вымываемый с дождем в реку. Также исследовались тяжелые металлы в дождевых стоках, попадающих в реку Нерис. Экспериментально с применением абсорбционно-спектрометрического метода исследовались тяжелые металлы Pb, Mn, Cr, Zn, Cu, Ni. Рассмотрен процесс анализа и результаты исследований. На основе полученных результатов составлена математическая модель распределения загрязняющих веществ в течении реки.
11
Жолобов, Владимир Васильевич, Валерий Юрьевич Морецкий, and Рустям Фаатович Талипов. "Distribution of volume of water accumulations in profile oil pipeline." SCIENCE & TECHNOLOGIES OIL AND OIL PRODUCTS PIPELINE TRANSPORTATION, no. 5 (October 31, 2022): 438–51. http://dx.doi.org/10.28999/2541-9595-2022-12-5-438-451.
Full textAbstract:
Введение. Имеющиеся математические модели поведения воды в эксплуатируемых нефтепроводах не учитывают возможность одновременного существования неподвижной и подвижной форм водных образований. Это ограничивает область применимости таких расчетных моделей и делает актуальной разработку обобщенных гидравлических моделей. Методы. Применение положений многоскоростного континуума позволяет сформулировать общую математическую модель многофазной среды, которая при адаптации допускает высокую степень детализации гидравлического описания накопления и миграции воды. При этом будут сформулированы незамкнутые уравнения (балансовые законы сохранения), которые применимы к описанию формирования условно неподвижного водного скопления и миграции коалесцированной воды как в непрерывной (ручейковой), так и в дисперсно-капельной форме на технологическом участке магистрального нефтепровода. Постановка задачи сводится к конкретизации межфазного взаимодействия на основе пограничного слоя и аналогии с движением влекомых наносов в теории русловых течений. Результаты. На основе соотношений пограничного слоя на поверхности контакта фаз и аналогового предположения о профиле продольной скорости получены расчетные зависимости для скорости среды на границе контакта, а также формулы для расчета силового взаимодействия и дисперсно-капельного массообмена. В отличие от имеющихся в научно-технической литературе вариантов замыкания здесь применен профиль скорости в циркуляционном течении воды. Обсуждение. Полученные зависимости в общем случае содержат дополнительные параметры, подлежащие идентификации и ранжированию по степени влияния на основные гидродинамические характеристики стратифицированных течений с поправкой на разницу в диаметрах срываемых и оседающих капель. Для этого требуются данные специально поставленных стендовых и численных экспериментов. Выводы. Представленная модель поведения воды в профильном трубопроводе сформулирована с учетом возможного волнового срыва капель с поверхности неподвижного водного скопления, полного дисперсно-капельного выноса или переноса капель на последующие участки. При практических расчетах, помимо обычной процедуры предварительной идентификации параметров однофазных моделей, дополнительно необходима идентификация параметров пограничного слоя на границе контакта фаз. Ключевые слова: стратифицированное течение, ручейковое течение, водные скопления в трубопроводах, двухфазное течение, математическая модель течения, дисперсная фаза, гидравлическая модель Introduction. The available mathematical models of water behavior in operated oil pipelines do not take into account the possibility of simultaneous existence of fixed and mobile forms of water formations. This limits the applicability of such design models and makes the development of generalized hydraulic models relevant. Methods. In the mechanics of multiphase media, on the basis of a multi-speed continuum, a mathematical apparatus is built, which, when adapted, allows any degree of detail in the hydraulic description of the process of accumulation and migration of water. At the same time, unclosed equations (balance conservation laws) are formulated, which are also applicable to the description of the formation of a conditionally stationary water accumulation and migration of coalesced water both in continuous (stream) and dispersed-droplet form in the technological section of the main oil pipeline. The formulation of the problem is reduced to the concretization of interphase interaction on the basis of the boundary layer and analogy with the movement of attracted sediments in the theory of channel currents. Results. Based on the ratios of the boundary layer on the phase contact surface and the assumption of the longitudinal velocity profile, calculated dependencies for the velocity of the medium at the contact boundary, as well as formulas for calculating the force interaction and disperse-droplet mass transfer, are obtained. In contrast to the options available in the literature, the velocity profile in the circulation flow of water is applied here. Discussion. The obtained dependencies in the general case contain additional parameters to be identified and ranked according to the degree of influence on the main hydrodynamic characteristics of the stratified currents, adjusted for the difference in the diameters of the torn and settling droplets. This requires data from specially staged bench and numerical experiments. Conclusion. The presented model of water behavior in the profile pipeline is formulated taking into account the possible wave breakage of droplets from the surface of a stationary water accumulation, complete dispersion-droplet removal or transfer of droplets to subsequent areas. In practical calculations, in addition to the usual procedure for preliminary identification of the parameters of single-phase models, it is additionally necessary to identify the parameters of the boundary layer at the phase contact boundary.
12
Ombaki, Richard, and Joash Kerongo. "Formulated Mathematical Model for Delayed Particle Flow in Cascaded Subsurface Water Reservoirs with Validation on River Flow." Journal of Applied Mathematics 2022 (November 10, 2022): 1–11. http://dx.doi.org/10.1155/2022/3438200.
Full textAbstract:
Migration of pollutant particles into subsurface water reservoirs through point sources is largely involved mixing processes within the system of water flow. Possible potential sources of pollution to these point sources include municipal wastes, septic loads, landfills, uncontrolled hazardous wastes, and sewage storage tanks. The mixing processes of pollutant significantly alter their predictive rate of flow in the water reservoirs, and therefore the time inherent in mixing processes need to be accounted for. In this study, pollution of subsurface water reservoirs mainly rivers and streams through contaminated water point sources (CWPS) was studied through a conceptual perspective of mixing problem processes in water tanks. The objective was to formulate a discrete time delay mathematical model which describes the dynamics of water reservoir pollution that involve single species contaminants such as nitrates, phosphorous, and detergents injecting from a point source. The concentration x t of pollutants was expressed as a function of the inflow and outflow rates using the principle for the conservation of mass. The major assumption made in modeling of mixing problems using tanks is that mixing is instantaneous. Practical realities dictate that mixing cannot occur instantaneously throughout the tank. So as to accommodate these realities, the study refined the systems of ordinary differential equations (ODEs) generated from principles of mixing problems in cascading tanks, into a system of delayed differential equations (DDEs) so that the concentration of pollutant leaving the reservoir at time t would be equal to the average concentration at some earlier instant, t − τ for the delay τ > 0 . The formulated model is a mathematical discrete time delay model which can be used to describe the dynamics of subsurface water reservoir pollution through a point source. The model was simulated on municipal River Nyakomisaro in Kisii County, Kenya. Physical and kinematic parameters of the river (cross-sectional lengths, depths, flow velocities) at three river sectional reservoirs were measured and the obtained parameter values were then used to evaluate coefficients of the formulated model equation. The system of DDEs from this simulation was solved numerically on MATLAB using dde23 software. From the graphical views generated for concentration of pollutant x t versus time t , it was established that the developed DDEs cover longer time series solutions (characteristic curves) than that from the corresponding ODEs in the same reservoir indicating that time necessary for particle flow through water reservoirs is underestimated if ODEs are used to describe particle flow. Also, the graphical views indicated similar tendencies (characteristics) in particle flow with time elapse even though initial values of concentration x t were different for every potentially recognized single species pollutant considered in each river reservoir. Hence, longer values of time t will imply more pollution in the water reservoir and vice versa. By introducing time delays due to constituent mixing processes in water quality simulation models that make use of advection-diffusion equation such as Qual2kw, the findings of this study can help for better understanding of the contaminant’s accumulation levels and their rate of transport in water resource. These will assist, for example, water-quality protection agencies such as Environmental Protection Agency (EPA), World Health Organization (WHO), and National Environmental Management Authority (NEMA) for the need to generate efficient and effective remedial strategies to control or mitigate hazardous or risks arising from water pollution.
13
Ryabova, G. O. "The Geminid meteor shower radiant: a mathematical model." Monthly Notices of the Royal Astronomical Society 507, no. 3 (August 9, 2021): 4481–86. http://dx.doi.org/10.1093/mnras/stab2286.
Full textAbstract:
ABSTRACT The origin of the Geminid meteoroid stream and its parent body the asteroid (3200) Phaethon is still under discussion. The observed bimodal activity profile of the Geminid shower agrees with a cometary scheme of the stream formation. We show that the radiant areas for meteors of different magnitudes may also be used to provide arguments supporting or undermining the cometary hypothesis. We used semi-analytic and numerical models of the stream. The resulting model radiants for meteors of various magnitudes (masses) have peculiar patterns that might be detected in a real shower.
14
Adam, C., J. Sánchez-Guillén, and A. Wereszczyński. "Conservation laws in Skyrme-type models." Journal of Mathematical Physics 48, no. 3 (March 2007): 032302. http://dx.doi.org/10.1063/1.2710652.
Full text
15
Boyraz, Uğur, and Cevza Melek Kazezyılmaz-Alhan. "Solutions for groundwater flow with sloping stream boundary: analytical, numerical and experimental models." Hydrology Research 49, no. 4 (June 9, 2017): 1120–30. http://dx.doi.org/10.2166/nh.2017.264.
Full textAbstract:
Abstract Protecting groundwater resources plays an important role in watershed management. For this purpose, studies on groundwater flow dynamics incorporating surface water–groundwater interactions have been conducted including analytical, numerical, and experimental models. In this research, a stream–aquifer system was considered to understand the physical behavior of surface water–groundwater interactions. Interactions in a stream–aquifer system were incorporated into the mathematical modeling by defining the stream head as a boundary condition for the groundwater flow equation. This boundary was chosen as a sloping stream boundary, which is an approach in representing the natural conditions of the stream and may be used to define continuous interactions between stream and aquifer. A semi-analytical solution for transient 2D groundwater flow was developed for the considered problem. Isotropic, homogeneous, and finite aquifer assumptions were made in order to define the aquifer characteristics. Then, a series of laboratory experiments was conducted to simulate this stream–aquifer system. Finally, a numerical model was developed by using Visual MODFLOW to verify analytical and experimental results. Numerical results matched with both analytical solutions and the experimental observations.
16
May, Robert M. "Food-web assembly and collapse: mathematical models and implications for conservation." Philosophical Transactions of the Royal Society B: Biological Sciences 364, no. 1524 (June 27, 2009): 1643–46. http://dx.doi.org/10.1098/rstb.2008.0280.
Full text
17
Sloat, Matthew R., and Ann-Marie K. Osterback. "Maximum stream temperature and the occurrence, abundance, and behavior of steelhead trout (Oncorhynchus mykiss) in a southern California stream." Canadian Journal of Fisheries and Aquatic Sciences 70, no. 1 (January 2013): 64–73. http://dx.doi.org/10.1139/cjfas-2012-0228.
Full textAbstract:
To determine individual and population responses of steelhead trout (Oncorhynchus mykiss) to stream temperature, we sampled summer stream temperature and juvenile steelhead occurrence, abundance, and behavior in a small stream near the species' southern limit. Maximum annual stream temperature (22.3–33.1 °C) exerted a strong threshold effect on steelhead occurrence. Steelhead persisted through summer in all pools that did not exceed 30 °C, but the probability of persistence rapidly decreased to zero at warmer sites. Below the threshold for fish persistence, thermal effects on steelhead abundance were inconsistent, with temperature receiving strong support for inclusion in models of fish abundance at the beginning of summer but weak support for inclusion in models of end-of-summer abundance and summer fish loss. Thermal refugia that would allow steelhead to behaviorally thermoregulate were rare. In response to elevated stream temperatures, steelhead reduced foraging and agonistic activity, presumably to minimize energetic costs. In anticipation of the effects of global climate trends on stream temperature, management actions that limit or reduce stream heating will be critical for conservation of steelhead populations in habitats approaching thermal tolerance thresholds.
18
van Odyck, Daniel E. A., John B. Bell, Franck Monmont, and Nikolaos Nikiforakis. "The mathematical structure of multiphase thermal models of flow in porous media." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, no. 2102 (November 4, 2008): 523–49. http://dx.doi.org/10.1098/rspa.2008.0268.
Full textAbstract:
This paper is concerned with the formulation and numerical solution of equations for modelling multicomponent, two-phase, thermal fluid flow in porous media. The fluid model consists of individual chemical component (species) conservation equations, Darcy's law for volumetric flow rates and an energy equation in terms of enthalpy. The model is closed with an equation of state and phase equilibrium conditions that determine the distribution of the chemical components into phases. It is shown that, in the absence of diffusive forces, the flow equations can be split into a system of hyperbolic conservation laws for the species and enthalpy and a parabolic equation for pressure. This decomposition forms the basis of a sequential formulation where the pressure equation is solved implicitly and then the component and enthalpy conservation laws are solved explicitly. A numerical method based on this sequential formulation is presented and used to demonstrate some typical flow behaviour that occurs during fluid injection into a reservoir.
19
Shields, F. Douglas, Eddy J. Langendoen, and Martin W. Doyle. "ADAPTING EXISTING MODELS TO EXAMINE EFFECTS OF AGRICULTURAL CONSERVATION PROGRAMS ON STREAM HABITAT QUALITY." Journal of the American Water Resources Association 42, no. 1 (February 2006): 25–33. http://dx.doi.org/10.1111/j.1752-1688.2006.tb03820.x.
Full text
20
Ziemińska-Stolarska, Aleksandra, and Jerzy Skrzypski. "Review of Mathematical Models of Water Quality." Ecological Chemistry and Engineering S 19, no. 2 (January 1, 2012): 197–211. http://dx.doi.org/10.2478/v10216-011-0015-x.
Full textAbstract:
Review of Mathematical Models of Water Quality Water is one of the main elements of the environment which determine the existence of life on the Earth, affect the climate and limit the development of civilization. Water resources management requires constant monitoring in terms of its qualitative-quantitative values. Proper assessment of the degree of water pollution is the basis for conservation and rational utilization of water resources. Water quality in lakes and dams is undergoing continuous degradation caused by natural processes resulting from eutrophication and due to anthropogenic reasons. One of the tools that are used to solve problems of surface water pollution is modelling of changes which take place in lake waters and associated water quality changes. In the last thirty years a rapid development of mathematical modelling of water resources quality has been observed. A number of computer models have been designed which are successfully applied in practice in many countries, including Poland. This paper presents an overview of mathematical models for assessment of water quality in dam reservoirs. Description of the WASP program which will be used for modelling water quality in the Sulejow Reservoir was the focal point.
21
Mohammed, F. A. "Soliton solutions for some nonlinear models in mathematical physics via conservation laws." AIMS Mathematics 7, no. 8 (2022): 15075–93. http://dx.doi.org/10.3934/math.2022826.
Full textAbstract:
<abstract><p>In this paper, we derive the soliton solutions from conserved quantities for the Benjamin-Bona-Mahoney equation with dual-power law nonlinearity (BBM), modified regularized long wave (MRLW) equation, modified nonlinearly dispersive KdV equations 2K(2, 2, 1) and 3K(3, 2, 2) equation, which are constructed by the multiplier approach (variational derivative method). Finally, we give the numerical simulations to illustrate this method.</p></abstract>
22
Ojimadu, U. H., A. O. Oluwole, A. O. Olasupo, M. A. Usman, T. J. Odule, O. O. Olubanwo, O. Oyewole, and M. A. Ayodele. "MATHEMATICAL ANALYSIS OF ELECTROPHYSIOLOGICAL CARDIAC TISSUE MEMBRANE MODELS." FUDMA JOURNAL OF SCIENCES 6, no. 2 (May 11, 2022): 138–43. http://dx.doi.org/10.33003/fjs-2022-0602-931.
Full textAbstract:
This paper presents some cardiac electrophysiological models. Proper mathematical analysis was done on the proposed models. In the cause of the analysis, several assumptions were made which helped in providing a parallel platform for making qualitative solutions so as to reduce any form of bias. Graphical analysis was adopted in solving the cardiac electrophysiological models using conservation and dispersions equations. The results obtained were derived from computer simulation by observing ring lengths on a valid restitution curve. The restitution curves helps us to subject three different turns of ring lengths and certain observations were made on the behavior of the three ring lengths. An increase in ring length will cause a corresponding increase in blood circulation and vice versa. It was suggested that 2D or 3D computer simulation should be adopted for better performance and yield of the models
23
Braun, Douglas C., and John D. Reynolds. "Relationships between habitat characteristics and breeding population densities in sockeye salmon (Oncorhynchus nerka)." Canadian Journal of Fisheries and Aquatic Sciences 68, no. 5 (May 2011): 758–67. http://dx.doi.org/10.1139/f2011-015.
Full textAbstract:
We examine the importance of stream habitat characteristics in governing variation in spawning densities of sockeye salmon ( Oncorhynchus nerka ) across 32 streams in the Fraser River Basin, British Columbia, Canada. We used mixed-effects models to examine four competing hypotheses for the influence of abiotic stream characteristics acting on either adult salmon or embryo mortality. All models that received support using Akaike’s information criterion included stream characteristics that are associated with cover. These included the percent area of pools, percentage of the banks that were undercut, and large woody debris (in that order). These results suggest the importance of stream characteristics, which reduce risk of predation on adults, in determining spawning sockeye salmon densities. Thus, identification of a small number of physical characteristics of streams provides insight into ecological processes that determine population densities. This information can be used to quantify habitat quality, which can guide habitat prioritization for conservation.
24
Peng, Liangrong, and Liu Hong. "Recent Advances in Conservation–Dissipation Formalism for Irreversible Processes." Entropy 23, no. 11 (October 31, 2021): 1447. http://dx.doi.org/10.3390/e23111447.
Full textAbstract:
The main purpose of this review is to summarize the recent advances of the Conservation–Dissipation Formalism (CDF), a new way for constructing both thermodynamically compatible and mathematically stable and well-posed models for irreversible processes. The contents include but are not restricted to the CDF’s physical motivations, mathematical foundations, formulations of several classical models in mathematical physics from master equations and Fokker–Planck equations to Boltzmann equations and quasi-linear Maxwell equations, as well as novel applications in the fields of non-Fourier heat conduction, non-Newtonian viscoelastic fluids, wave propagation/transportation in geophysics and neural science, soft matter physics, etc. Connections with other popular theories in the field of non-equilibrium thermodynamics are examined too.
25
Weil, Kristen K., Christopher S. Cronan, Spencer R. Meyer, Robert J. Lilieholm, Thomas J. Danielson, Leonidas Tsomides, and Dave Owen. "Predicting stream vulnerability to urbanization stress with Bayesian network models." Landscape and Urban Planning 170 (February 2018): 138–49. http://dx.doi.org/10.1016/j.landurbplan.2017.11.001.
Full text
26
Dash, S. K., and S. K. Som. "Ignition and Combustion of Liquid Fuel Droplet in a Convective Medium." Journal of Energy Resources Technology 113, no. 3 (September 1, 1991): 165–70. http://dx.doi.org/10.1115/1.2905799.
Full textAbstract:
A mathematical model of droplet combustion in surroundings of hot gas with a uniform free stream motion is made from the numerical solution of the conservation equations of heat, mass and momentum in both the carrier and droplet phases. The gas phase chemical reaction between fuel vapor and oxidizer is assumed to be a single-step irreversible one. The phenomena of ignition is recognized by the sudden rise of temperature in the temperature-time histories at different locations in the carrier phase. The relative influences of pertinent input parameters, namely initial Reynolds number Rei, ratio of free stream to initial drop temperature T∞, and the ambient pressure on: (i) the ignition time lag, (ii) extinction characteristics, and (iii) life histories of burning fuel drops have been established.
27
Alvarez, Benjamin Louis, and Jérémy Faupin. "Scattering theory for mathematical models of the weak interaction." Reviews in Mathematical Physics 32, no. 01 (August 8, 2019): 2050002. http://dx.doi.org/10.1142/s0129055x20500026.
Full textAbstract:
We consider mathematical models of the weak decay of the vector bosons [Formula: see text] into leptons. The free quantum field Hamiltonian is perturbed by an interaction term from the standard model of particle physics. After the introduction of high energy and spatial cut-offs, the total quantum Hamiltonian defines a self-adjoint operator on a tensor product of Fock spaces. We study the scattering theory for such models. First, the masses of the neutrinos are supposed to be positive: for all values of the coupling constant, we prove asymptotic completeness of the wave operators. In a second model, neutrinos are treated as massless particles and we consider a simpler interaction Hamiltonian: for small enough values of the coupling constant, we prove again asymptotic completeness, using singular Mourre’s theory, suitable propagation estimates and the conservation of the difference of some number operators.
28
Zhu, Ping. "Application of Thermodynamics to the Allocation of Cumulative Exergy Consumption in the Multiproduct Separation Processes." Advanced Materials Research 236-238 (May 2011): 741–45. http://dx.doi.org/10.4028/www.scientific.net/amr.236-238.741.
Full textAbstract:
Based on the minimum separation work theory, a novel allocation parameter of cumulative exergy consumption, the minimum separation power of the product stream (MSPS), is proposed in the separation processes in this article. The related mathematical models are established. The application of this approach to a case study is provided.
29
Dong, Z., and Xi Chen Yang. "Theoretical Simulation of Temperature Field of Coaxial Powder Stream in Laser Cladding." Key Engineering Materials 392-394 (October 2008): 245–49. http://dx.doi.org/10.4028/www.scientific.net/kem.392-394.245.
Full textAbstract:
Theoretical models of temperature field are presented from Beer-Lambert law. This paper uses Beer-Lambert law to calculate powder flow on the absorption of energy and applies the law of the conservation of the energy to calculate the temperature of powder stream. This paper analyzes the effect of the various factors on the temperature field of powder flow. Temperature field of powder stream is measured by CCD camera. Finally the comparison of the theoretical results and the experimental results indicates the accuracy of the theoretical calculation.
30
Răsvan, Vladimir. "Control of Conservation Laws – An Application." Tatra Mountains Mathematical Publications 71, no. 1 (December 1, 2018): 155–74. http://dx.doi.org/10.2478/tmmp-2018-0014.
Full textAbstract:
Abstract We present here three types of controlled boundary value problems for conservation laws arising from energy co-generation, hydraulic flows and water hammer for hydroelectric power plants and control of the open channel flows (shallow water). The novelty of these models, from the mathematical point of view, is that they are described by nonlinear hyperbolic partial differential equations of the conservation laws with (possibly) nonlinear boundary conditions. At their turn these boundary conditions are controlled by some systems of ordinary differential equations. The engineering requirements for such systems are asymptotic stability and disturbance rejection: these properties have to be achieved by feedback control. In our setting the main tool for tackling these problems is a suitable Lyapunov functional arising from the energy identity. The hints for “guessing” this functional are to be found in the linearized version of the aforementioned mathematical objects.
31
Falke, Jeffrey A., Kurt D. Fausch, Kevin R. Bestgen, and Larissa L. Bailey. "Spawning phenology and habitat use in a Great Plains, USA, stream fish assemblage: an occupancy estimation approach." Canadian Journal of Fisheries and Aquatic Sciences 67, no. 12 (December 2010): 1942–56. http://dx.doi.org/10.1139/f10-109.
Full textAbstract:
Knowledge of basic life-history attributes, paired with unbiased estimates of species distribution, is critical for the effective conservation of sensitive fish species. We quantified the spawning phenology, habitat use, and detectability for larvae of an assemblage of threatened Great Plains, USA, stream fishes using new occupancy estimation methods. Spawning by six Great Plains fish species occurred from April through July, and was likely initiated by changes in water temperature and photoperiod. Habitat size and type were important factors influencing the occupancy of larvae in spawning habitats. Detectability of larvae differed among species and over time, and was influenced by habitat depth and fish size. Our models indicated that multiple samples from individual habitats within a season are needed to adequately detect and predict occupancy by stream fish larvae. Conservation efforts for imperiled Great Plains fish assemblages should focus on sustaining flows that maintain a sufficient density and size of habitats needed for successful spawning and recruitment. The occupancy estimation and modeling methods employed here will be useful in developing comprehensive, unbiased programs to monitor the reproductive success of Great Plains stream fishes.
32
Karzilov, A. I., F. F. Tetenev, T. N. Bodrova, and P. Ye Mes’ko. "Prediction of bronchial permeability disturbance from breathing patterns." Bulletin of Siberian Medicine 6, no. 4 (December 30, 2007): 22–30. http://dx.doi.org/10.20538/1682-0363-2007-4-22-30.
Full textAbstract:
Health subjects (n = 15), patients with bronchial asthma (n = 30), COPD (n = 16), and community-acquired pneumonia (n = 17) have been inspected in the mixed group (40 men, 38 women, 15-64 years old). The results of research of breathing patterns with interruption of air stream have been used to construct Raw, FEV1, FEV1% and FEV1/FVC% mathematical models. High diagnostic importance of FEV1% and FEV1/FVC% models in prediction of bronchial permeability disturbance has been shown.
33
Widodo, Basuki, Eirene Juwita Ningtyas Pamela, Dieky Adzkiya, Chairul Imron, and Tri Rahayuningsih. "MAGNETOHYDRODYNAMICS NANOFERRO FLUID FLOWS PASSING THROUGH A MAGNETIC POROUS SPHERE UNDER THERMAL RADIATION EFFECT." BAREKENG: Jurnal Ilmu Matematika dan Terapan 16, no. 4 (December 15, 2022): 1303–12. http://dx.doi.org/10.30598/barekengvol16iss4pp1303-1312.
Full textAbstract:
In the application of thermonuclear reactor cooling, temperature regulation relies on experiments based on practical experience. Therefore, the accuracy of this temperature setting is operator-dependent. So it is necessary to develop a mathematical model to solve these problems. The dimensional mathematical model therefore is generated using the conservation laws of mass, momentum, and energy. The dimensional mathematical model is further transformed into non-dimensional mathematical model by using non-dimensional variables. The non-dimensional mathematical model is simplified using the similarity equation by utilizing the stream function. The model obtained is a system of nonlinear ordinary differential equations. This system of equations is then solved using an implicit numerical method using Keller-Box scheme. This Keller-Box method has high accuracy and is more efficient. The numerical simulation results show that the velocity profile and temperature profile decrease as the magnetic parameter, porosity parameter, and the Prandtl number increases, respectively. Meanwhile, when the radiation parameter increases, the temperature profile also increases, but the radiation parameter does not affect the velocity profile.
34
Rak, Tomasz, and Dariusz Rzonca. "Recommendations for Using QPN Formalism for Preparation of Incoming Request Stream Generator in Modeled System." Applied Sciences 11, no. 23 (December 5, 2021): 11532. http://dx.doi.org/10.3390/app112311532.
Full textAbstract:
Simulation models are elements of science that use software tools to solve complex mathematical problems. They are beneficial in areas such as performance engineering and communications systems. Nevertheless, to achieve more accurate results, researchers should use more detailed models. Having an analysis of the system operations in the early modeling phases could help one make better decisions relating to the solution. In this paper, we introduce the use of the QPME tool, based on queueing Petri nets, to model the system stream generator. This formalism was not considered during the first tool development. As a result of the analysis, an alternative design model is proposed. By comparing the behavior of the proposed generator against the one already developed, a better adjustment of the stream to the customer’s needs was obtained. The study results show that appropriately adjusting queueing Petri net models can help produce better streams of data (tokens).
35
Orazbayev, B., I. Issa, N. Dzumamukhambetov, B. E. Utenova, A. Seidaliyev, and G. Shuitenov. "Construction of geological and mathematical models for modeling the oil pool of the Kenkiyak deposit." Bulletin of the National Engineering Academy of the Republic of Kazakhstan 84, no. 2 (June 15, 2022): 195–205. http://dx.doi.org/10.47533/2020.1606-146x.143.
Full textAbstract:
Geological and mathematical models of the oil reservoir of the post-salt Kenkiyak field have been investigated and built. 6 types of geological models have been proposed, and on the basis of these models, mathematical models of oil deposits have been developed. Geological models are built on the basis of research results, taking into account the requirements of regulating the development of the Kenkiyak field, the geological characteristics of the field and the rate of operation. The mathematical model is based on the basic Darcy equations and includes equations for conservation of mass and energy, equations for limiting mass and oil saturation. The issues of modeling and determination of the relative permeability at the end point are studied, the results of determining the parameters of the relative permeability of different formations at normal and high temperatures are presented. The results of identification of parameters of mathematical models are considered.
36
L. Zambory, Courtney, Harvest Ellis, Clay L. Pierce, Kevin J. Roe, Michael J. Weber, Keith E. Schilling, and Nathan C. Young. "The Development of a GIS Methodology to Identify Oxbows and Former Stream Meanders from LiDAR-Derived Digital Elevation Models." Remote Sensing 11, no. 1 (December 21, 2018): 12. http://dx.doi.org/10.3390/rs11010012.
Full textAbstract:
Anthropogenic development of floodplains and alteration to natural hydrological regimes have resulted in extensive loss of off-channel habitat. Interest has grown in restoring these habitats as an effective conservation strategy for numerous aquatic species. This study developed a process to reproducibly identify areas of former stream meanders to assist future off-channel restoration site selections. Three watersheds in Iowa and Minnesota where off-channel restorations are currently being conducted to aid the conservation of the Topeka Shiner (Notropis topeka) were selected as the study area. Floodplain depressions were identified with LiDAR-derived digital elevation models, and their morphologic and topographic characteristics were described. Classification tree models were developed to distinguish relic streams and oxbows from other landscape features. All models demonstrated a strong ability to distinguish between target and non-target features with area under the receiver operator curve (AUC) values ≥ 0.82 and correct classification rates ≥ 0.88. Solidity, concavity, and mean height above channel metrics were among the first splits in all trees. To compensate for the noise associated with the final model designation, features were ranked by their conditional probability. The results of this study will provide conservation managers with an improved process to identify candidate restoration sites.
37
Sapa, Lucjan, Bogusław Bożek, Katarzyna Tkacz–Śmiech, Marek Zajusz, and Marek Danielewski. "Interdiffusion in many dimensions: mathematical models, numerical simulations and experiment." Mathematics and Mechanics of Solids 25, no. 12 (June 30, 2020): 2178–98. http://dx.doi.org/10.1177/1081286520923376.
Full textAbstract:
Over the last two decades, there have been tremendous advances in the computation of diffusion and today many key properties of materials can be accurately predicted by modelling and simulations. In this paper, we present, for the first time, comprehensive studies of interdiffusion in three dimensions, a model, simulations and experiment. The model follows from the local mass conservation with Vegard’s rule and is combined with Darken’s bi-velocity method. The approach is expressed using the nonlinear parabolic–elliptic system of strongly coupled differential equations with initial and nonlinear coupled boundary conditions. Implicit finite difference methods, preserving Vegard’s rule, are generated by some linearization and splitting ideas, in one- and two-dimensional cases. The theorems on the existence and uniqueness of solutions of the implicit difference schemes and the consistency of the difference methods are studied. The numerical results are compared with experimental data for a ternary Fe-Co-Ni system. A good agreement of both sets is revealed, which confirms the strength of the method.
38
Isaak, Daniel J., Jay M. Ver Hoef, Erin E. Peterson, Dona L. Horan, and David E. Nagel. "Scalable population estimates using spatial-stream-network (SSN) models, fish density surveys, and national geospatial database frameworks for streams." Canadian Journal of Fisheries and Aquatic Sciences 74, no. 2 (February 2017): 147–56. http://dx.doi.org/10.1139/cjfas-2016-0247.
Full textAbstract:
Population size estimates for stream fishes are important for conservation and management, but sampling costs limit the extent of most estimates to small portions of river networks that encompass 100s–10 000s of linear kilometres. However, the advent of large fish density data sets, spatial-stream-network (SSN) models that benefit from nonindependence among samples, and national geospatial database frameworks for streams provide the components to create a broadly scalable approach to population estimation. We demonstrate such an approach with density surveys for trout species from 108 sites in a 735 km river network. Universal kriging was used to predict a continuous map of densities among survey locations, and block kriging (BK) was used to summarize discrete map areas and make population estimates at stream, river, and network scales. The SSN models also accommodate covariates, which facilitates hypothesis testing and provides insights about factors affecting patterns of abundance. The SSN–BK population estimator can be applied using free software and geospatial resources to develop valuable information at low cost from many existing fisheries data sets.
39
Wall, Steven S., Charles R. Berry, Jr., Carmen M. Blausey, Jonathan A. Jenks, and Chad J. Kopplin. "Fish-habitat modeling for gap analysis to conserve the endangered Topeka shiner (Notropis topeka)." Canadian Journal of Fisheries and Aquatic Sciences 61, no. 6 (June 1, 2004): 954–73. http://dx.doi.org/10.1139/f04-017.
Full textAbstract:
Decision support tools that predict fish distribution over broad spatial scales are needed to assist in planning watershed management and endangered species recovery. We developed a geographical information system model with multivariate logistic regression to rank valley segments for probable occurrence of the endangered Topeka shiner (Notropis topeka) using stream condition variables (stream size, groundwater potential, channel slope, streamflow, network position) and land-cover variables (percent pasture, percent trees) in streams characteristic of the North American Great Plains. The stream condition and land-cover models correctly classified 89% and 68% of outcomes (i.e., presence or absence), respectively. Field tests of maps of predicted species distribution resulted in more species occurrences than expected in valley segments classified as high potential for presence and less than expected in low-potential valley segments. Gaps between high-priority segments and protected land parcels were found in all basins. In 37 basins with Topeka shiners, protected land coverage was <1% in 17 basins, 15% in 10 basins, and 521.8% in 10 basins. Conservation activities in gaps are long-term conservation measures, but maps of predicted species distribution have many immediate applications.
40
Władysiak, R., and P. Budzyński. "Structure of Water Mist Stream and its Impact on Cooling Efficiency of Casting Die." Archives of Foundry Engineering 12, no. 2 (April 1, 2012): 251–60. http://dx.doi.org/10.2478/v10266-012-0069-y.
Full textAbstract:
Structure of Water Mist Stream and its Impact on Cooling Efficiency of Casting Die The work is a continuation of research on the use water mist cooling in order to increase efficiency of die-casting aluminum alloys. The paper presents results of research and analysis process, spraying water and generated a stream of water mist, the effect of the type of nozzle, the nozzle size and shape of the emitting of the water mist on the wall surface of casting die on the microstructure and geometry of water mist stream and cooling efficiency. Tests were used to perform high-speed camera to record video in the visible and infrared camera. Results were used to develop a computerized image analysis and statistical analysis. The study showed that there are statistical relationships between water and air flow and geometry of the nozzle and nozzle emitting a stream of microstructure parameters of water mist and heat the incoming stream. These relationships are described mathematical models that allow you to control the generating of adequate stream of water mist and a further consequence, the cooling efficiency of casting die.
41
Liang, Zhong Wei, Xiao Chu Liu, Yi Jun Wang, and Zai Hai Yu. "Research on Fitting Curve's Characteristics of Turbulence Motion Locus Based on Image Projection Transformation and Light Stream Vector." Advanced Materials Research 148-149 (October 2010): 1674–79. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.1674.
Full textAbstract:
The variation discipline of turbulence motion locus during the process of bearing’s strengthening grinding is a difficult point in the research fields of fluid theory. For the purpose of obtaining accurate discipline of turbulence motion, the fitting curve’s characteristics of turbulence motion locus based on image projection transformation and light stream vector is investigated. Through tracing particles be equally-distributed scattered into flow field, they reflect turbulence’s motion discipline accurately. After each particle’s movement has been shot from different orientations in continuous time-points, thus sequential conjugate images have been obtained. Relationship of image projecting transformation is established for determining these particles’ absolute three-dimensional coordinates. Combining with light stream vector, these particles’ motion vectors in each instantaneous moment can be deducted and mathematical models of motion locus can be gotten. Then correlative mathematical characteristics are built, their variation tendency is analyzed in different flow velocities. This experiment provides theoretical foundation and technical preparation for research of complicated turbulence and selection of fluid signal sampling’s condition.
42
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.
43
Mohammed, G. A., W. Zijl, O. Batelaan, and F. De Smedt. "Comparison of Two Mathematical Models for 3D Groundwater Flow: Block-Centered Heads and Edge-Based Stream Functions." Transport in Porous Media 79, no. 3 (February 4, 2009): 469–85. http://dx.doi.org/10.1007/s11242-009-9336-y.
Full text
44
Gueuvoghlanian, E. P. "Bicomplexes and conservation laws in non-Abelian Toda models." Journal of Physics A: Mathematical and General 34, no. 31 (July 27, 2001): L425—L433. http://dx.doi.org/10.1088/0305-4470/34/31/102.
Full text
45
Bucklin, David N., Mathieu Basille, Stephanie S. Romañach, Lauren A. Brandt, Frank J. Mazzotti, and James I. Watling. "Considerations for Building Climate-based Species Distribution Models." EDIS 2016, no. 8 (October 6, 2016): 8. http://dx.doi.org/10.32473/edis-uw420-2016.
Full textAbstract:
Climate plays an important role in the distribution of species. A given species may adjust to new conditions in-place, move to new areas with suitable climates, or go extinct. Scientists and conservation practitioners use mathematical models to predict the effects of future climate change on wildlife and plan for a biodiverse future. This 8-page fact sheet explains how, with a better understanding of species distribution models, we can predict how species may respond to climate change. The models alone cannot tell us how a certain species will actually respond to changes in climate, but they can inform conservation planning that aims to allow species to both adapt in place and (for those that are able to) move to newly suitable areas. Such planning will likely minimize loss of biodiversity due to climate change. Written by David N. Bucklin, Mathieu Basille, Stephanie S. Romañach, Laura A. Brandt, Frank J. Mazzotti, and James I. Watling, and published by the Department of Wildlife Ecology and Conservation, August 2016. WEC375/UW420: Considerations for Building Climate-based Species Distribution Models (ufl.edu)
46
Zhang, Yu Fan, Zhi Hao Ji, Jin Yan Liu, Shu Sheng Xiong, Xiao Bo Huang, Bin Tao Mao, Bao Sheng Guo, Zhi Chao Ying, and Ya Bo Sun. "Study on Mathematical Model in Working Process of Automotive Air Conditioning Scroll Compressor." Applied Mechanics and Materials 741 (March 2015): 572–76. http://dx.doi.org/10.4028/www.scientific.net/amm.741.572.
Full textAbstract:
In order to study the working features of automotive air conditioning scroll compressor, this paper uses mathematical model of working process to analyze it. After studying working process, a equation of suction volume is given. The thermodynamic model of compression chamber and back pressure chamber includes mass conservation and energy conservation. Based on Hydromechanics, leakage models of radial leakage and tangential leakage are discussed. The model lays a foundation of automotive air conditioning scroll compressor performance simulation.
47
Myhan, Ryszard, and Marek Markowski. "Generalized Mathematical Model of the Grain Drying Process." Processes 10, no. 12 (December 19, 2022): 2749. http://dx.doi.org/10.3390/pr10122749.
Full textAbstract:
Convective cereal grain drying is an energy-intensive process. Mathematical models are applied to analyze and optimize grain drying processes in different types of dryers and in different stages of drying to improve final grain quality and reduce energy consumption. The aim of the present study was to develop a generalized mathematical model of the grain drying process that accounts for all drying stages, including loading and unloading of unprocessed grain, drying, and cooling of dry grain. The developed mathematical model is a system of algebraic equations, where the calculated coefficients are determined by the thermophysical and diffusive properties of dried grain. The model was validated for batch drying of wheat, canola, and corn grain, as well as continuous flow drying of wheat grain. The results were compared with published findings. The relationships between energy consumption during drying and drying time vs. air temperature at the dryer inlet and air stream volume were determined. Dryer capacity and drying conditions specified by the manufacturers, as well as loading and unloading capacity, were considered during batch drying. Continuous flow drying simulations were conducted in counter-flow, parallel-flow, and cross-flow mode. Simulation results indicate that the proposed models correctly depicted process flow in both batch and continuous flow dryers.
48
Ivanusa, Andriy. "Project of forming «culture and safety» of the airport." MATEC Web of Conferences 247 (2018): 00045. http://dx.doi.org/10.1051/matecconf/201824700045.
Full textAbstract:
Using the method analysis of the systems and synthesis parameters that influence on the process evacuation of people were certain. Methodological principles are used in relation to the management of people streams on the basis of the use critical path method, where the optimization synthesis of evacuation route people is considered as a topological chart of technological line, and an evacuation way is broken on separate parts. By means of probabilistic method and optimization synthesis of flexible technological lines topological case of users of airport streams frames are worked out and sometimes the evacuation. Conducted analysis of existent mathematical models, that describe motion streams of people on the objects of their mass stay showed that the stream users of the airport mutated and him mathematical description requires the synthesis of a few mathematical models. The method calculation time of evacuation users of the airport in that person informative base drawn on results other undertaken experimental studies is accordingly offered.
49
BARROS, RICARDO. "CONSERVATION LAWS FOR ONE-DIMENSIONAL SHALLOW WATER MODELS FOR ONE AND TWO-LAYER FLOWS." Mathematical Models and Methods in Applied Sciences 16, no. 01 (January 2006): 119–37. http://dx.doi.org/10.1142/s0218202506001078.
Full textAbstract:
A full set of conservation laws for the two-layer shallow water equations is presented for the one-dimensional case. We prove that all the conservation laws are linear combination of the equations for the conservation of mass and velocity (in each layer), total momentum and total energy.This result generalizes that of Montgomery and Moodie that found the same conserved quantities by restricting their search to the multinomials expressions in the layer variables. Though the question of whether or not there are only a finite number of these quantities is left as an open question by the authors. Our work puts an end to this: in fact, no more conservation laws are admitted for the two-layer shallow water equations. The key mathematical ingredient of the method proposed leading to the result is the Frobenius problem. Moreover, we present a full set of conservation laws for the classical one-dimensional shallow water model with topography, by using the same techniques.
50
Чермошенцева, А. А., and А. Н. Шулюпин. "Development of mathematical models for calculating parameters during transportation of a steam-water mixture." Вестник КРАУНЦ. Физико-математические науки, no. 3 (November 22, 2021): 94–109. http://dx.doi.org/10.26117/2079-6641-2021-36-3-94-109.
Full textAbstract:
В практике освоения геотермальных месторождений возникает необходимость нахождение взаимосвязи между параметрами потока. При транспортировке пароводяной смеси требуется определение условий, обеспечивающих стабильную работу трубопровода. На отечественных объектах геотермальной энергетики гидравлический расчет трубопроводов пароводяной смеси проводился с использованием компьютерной программы MODEL, разработанной авторами данной работы. Новые вызовы и появление теории устойчивости привели к созданию математической модели SWIP (Steam-Water Inclining Pipeline). В данной статье представлены этапы разработки авторами новой модели, отвечающей современным требованиям In the practice of developing geothermal fields, there is a need to find the dependence between the flow parameters. When transporting a steam-water mixture, it is necessary to determine the conditions that ensure the stability in the pipeline. At domestic geothermal energy, the hydraulic calculation of steam-water mixture pipelines was carried out using the computer program MODEL created by the authors of this work. New challenges and the emergence of the theory of stability led to the creation of a mathematical model SWIP (Stream-Water Inclining Pipeline). This article presents the stages of creating a new model by the authors that meets modern requirements.