Mathematical modelling of the selective deep water intake process in a non-prismatic continuously stratified reservoir

Разработана математическая модель селективного водозаборного процесса в узко-глубоком непризматическом водоеме при наличии в нем прямой непрерывной плотностной стратификации. Модель представляет контактную краевую задачу потенциального движения воды в указанном водоеме. Движение воды обусловлено забором воды через два окна, устроенных одно над другим на напорной грани водоема. Учтена непризматическая конфигурация водоема в плане и по вертикали. Непризматические конфигурации описаны экспоненциальными функциями. В результате аналитического решения поставленной контактной краевой задачи получена совокупность расчетных формул, которая с привлечением конечноразностного метода Рунге-Кутты и компьютерных вычислительных систем позволила построить линии тока, приходящие к верхней кромке нижнего водозаборного окна. Вычислительные эксперименты показали, что по мере увеличения скорости потока воды через верхнее окно указанные линии тока опускаются вниз. При этом становится возможным управлять водозаборным процессом через нижнее окно с тем расчетом, чтобы в нижнее окно вода поступала из нижних холодных слоев водоема, что часто бывает необходимо для нужд теплоотвода от тепловыделяющих устройств предприятий, в том числе тепловых и атомных электростанций. Purpose. Mathematical simulation of the selective water intake process in a non-prismatic reservoir in the presence of continuous density stratification. Methodology. Water intake is carried out through two windows arranged one above the other on the pressure face of the reservoir. The non-prismatic configuration of the reservoir both in vertical and horizontal planes is taken into account. The contact initial-boundary value problem of the theory for surface and internal gravitational waves in an ideal incompressible fluid is used. Findings. As a result of the analytical solution of the mathematical model, a set of calculation formulas was obtained, which allows calculating the current lines coming to the upper edge of the lower water intake window. Originality/value. Authors obtain a set of formulas for the components of the water velocity vector. Using the set, a nonlinear boundary value problem is posed and solved for calculation of the current line coming to the upper edge of the lower water intake window by the finite-difference Runge-Kutta method. Based on the results of computational experiments, authors proved that the longitudinal and vertical non-prismatic configuration of a stratified reservoir significantly affects the process of selective water intake. It is proved that as the rate of water intake through the upper window increases, the thickness of the active layer from which water is taken through the lower window decreases to a certain minimum value. This hydrodynamic effect allows taking water from the deep cold layers of the reservoir

Turbulent Flow Around Obstacles: Simulation and Study with Variable Roughness

The present work aims to investigate the recirculation and incipient mixing zones in a channel flow supplied with obstacles. The main objective is to develop a new technique to control these recirculation zones by setting a variable roughness. For the purpose of varying that roughness, 4 small bars of heights 0.25H, 0.5H, 0.75H and H were placed downstream of the obstacle; H is the height of the obstacle. For this, a three-dimensional numerical approach was carried out using the ANSYS CFX computer code. In addition, the governing equations were solved using the finite volume method. The K-ω shear-stress transport (SST) turbulence model was utilized to model the turbulent stresses. In the end, we presented the time-averaged simulation results of the contours of the current lines (3D time-averaged streamlines, trace-lines), three components of the velocities: <u> (velocity u contour), <v> (velocity v contour) and <w> (velocity w contour), trace-lines, stream ribbons and mean Q-criterion iso-surface.

APPLICATION OF HVDC SYSTEMS FOR RES INTEGRATION AND POWER TRANSMISSION FROM THE PROFICIT SOUTH PART OF THE IES OF UKRAINE

The analysis and estimation of advantages from implementation of HVDC systems in parallel to the loaded alternating current lines as a means of solving the problem of power output from surplus energy regions of the IES of Ukraine was presented. Such regions arise with the active development of new Renewable Energy Resources (RES). Two variants of installation of such systems are proposed and the corresponding analysis of electrical modes of IES of Ukraine with reliability criteria "N-1" was executed. References 11, figures 4, table 1.

Global Trends in Cancer Nanotechnology: A Qualitative Scientific Mapping Using Content-Based and Bibliometric Features for Machine Learning Text Classification

This study presents a new way to investigate comprehensive trends in cancer nanotechnology research in different countries, institutions, and journals providing critical insights to prevention, diagnosis, and therapy. This paper applied the qualitative method of bibliometric analysis on cancer nanotechnology using the PubMed database during the years 2000–2021. Inspired by hybrid medical models and content-based and bibliometric features for machine learning models, our results show cancer nanotechnology studies have expanded exponentially since 2010. The highest production of articles in cancer nanotechnology is mainly from US institutions, with several countries, notably the USA, China, the UK, India, and Iran as concentrated focal points as centers of cancer nanotechnology research, especially in the last five years. The analysis shows the greatest overlap between nanotechnology and DNA, RNA, iron oxide or mesoporous silica, breast cancer, and cancer diagnosis and cancer treatment. Moreover, more than 50% of the information related to the keywords, authors, institutions, journals, and countries are considerably investigated in the form of publications from the top 100 journals. This study has the potential to provide past and current lines of research that can unmask comprehensive trends in cancer nanotechnology, key research topics, or the most productive countries and authors in the field.

Circular Economy Applied to Organic Residues and Wastewater: Research Challenges

To move today’s agricultural and urban systems towards tomorrow’s circular economy and respond to climate change, it is imperative to turn organic residues and wastewater into resourceful assets. This article discusses the changes that are needed in research to drive this paradigm shift and to go from a “losses and waste” situation to a “resource and opportunities” ambition. The current lines of research aim to maximise the use and value of biomass or organic residues and wastewater and propose new organisational schemes driven by technical innovations. Exploring the pathways to a sustainable future through many domains let us identify five challenges to structure the research efforts and find circular bioeconomy solutions for organic residues and wastewater: (1) proposing innovative processes and integrated multi-process systems; (2) promoting the emergence of multi-scale and cross-sectoral organisations; (3) developing multi-performance evaluation methods, (4) rethinking research–society intersections, and (5) enhancing research–legislation interactions. We end by outlining prospects for moving forward past current limitations: beyond increasing knowledge, research will continue its own transition. Our responsibility today is not to think about what we could do for a better world but what we should do to make our ever-changing world even better and more sustainable. Graphic Abstract

Applications of Artificial Intelligence, Machine Learning, Big Data and the Internet of Things to the COVID-19 Pandemic: A Scientometric Review Using Text Mining

The COVID-19 pandemic has wreaked havoc in every country in the world, with serious health-related, economic, and social consequences. Since its outbreak in March 2020, many researchers from different fields have joined forces to provide a wide range of solutions, and the support for this work from artificial intelligence (AI) and other emerging concepts linked to intelligent data analysis has been decisive. The enormous amount of research and the high number of publications during this period makes it difficult to obtain an overall view of the different applications of AI to the management of COVID-19 and an understanding of how research in this field has been evolving. Therefore, in this paper, we carry out a scientometric analysis of this area supported by text mining, including a review of 18,955 publications related to AI and COVID-19 from the Scopus database from March 2020 to June 2021 inclusive. For this purpose, we used VOSviewer software, which was developed by researchers at Leiden University in the Netherlands. This allowed us to examine the exponential growth in research on this issue and its distribution by country, and to highlight the clear hegemony of the United States (USA) and China in this respect. We used an automatic process to extract topics of research interest and observed that the most important current lines of research focused on patient-based solutions. We also identified the most relevant journals in terms of the COVID-19 pandemic, demonstrated the growing value of open-access publication, and highlighted the most influential authors by means of an analysis of citations and co-citations. This study provides an overview of the current status of research on the application of AI to the pandemic.

Possible changes in transport conception of international and long-distance railway connections relating the construction of new high-speed railway lines in the Czech Republic

The aim of this article is to deal with the issue of high-speed railway lines (HSL) in the Czech Republic in response to the Fast connections conception ("Rychlá spojení" in Czech, abbreviation "RS"). Currently the RS1, RS2 and RS4 projects are the most watched during the preparation of the HSL network construction. The authors would like to focus on this issue from the wider point of view and to assess possible impact on the current lines of long-distance trains, the location of graphical timetable nodes and the way of the transport service on the area of the state.

Quantitative assessment of hydraulic tortuosity of oil and gas reservoirs in Western Siberia based on capillarimetric studies

It is known that a capillary model with a given size pore channels distribution does not allow estimating the absolute reservoir permeability with sufficient accuracy. In this case, it is necessary to introduce a certain correction factor into the formula, which is called either the lithological factor or hydraulic tortuosity. The paper shows that the need for a correction factor appears mainly due to the capillary model inconsistency to the real geometry of the reservoir void space. In this regard, we propose to use the dumbbell model when calculating the absolute permeability, in which the filtering channels are represented by alternating pores and interporous narrowings. This paper presents a methodology for calculating the hydraulic tortuosity for reservoirs of Western Siberia based on the results of capillary studies, as well as based on the data from the capacitive properties study. Hydraulic tortuosity is explained by the process of expansion of current lines in the pores and their contraction in the interporous tubules of the rock. It is noted that the residual water leads to a narrowing of the pores’ open area and, accordingly, to a certain decrease in the hydraulic tortuosity.