bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress state of an earth dam under main loads considering data from field observations
Authors: Salyamova K D , Turdikulov Kh Kh 
Published: June 2021

Abstract
Reliable and safe operation of hydro-technical structures (earth dams), in the seismic regions of the republic, requires researchers to constantly improve the calculation methods in accordance with the requirements of regulatory documents for basic and special combinations of loads, including seismic ones. A calculation method is proposed for estimating the stress state on the example of an earth dam of the Charvak HPP (in operation for 47 years) in a plane elastic statement under main loads, taking into account the real piecewise-inhomogeneous physical and mechanical characteristics of soil of the structure body. Individual results of solving the problem were compared with the data of long-term field observations. The calculation method allows determining the kinematic characteristics (displacements, settlements, stresses, pore pressure) of an earth dam, which makes it possible to predict the state of the most vulnerable places in the structure and, if necessary, to develop appropriate measures to strengthen them. The problem was solved by the numerical finite element method. According to the developed technique, the problem by the numerical finite element method was reduced to solving a system of linear equations relative to the desired displacements. The calculation results are presented in the form of isolines of the stress-strain state of the dam body under the main loads (gravitational forces, hydrostatics). The numerical results of solving the problem and their comparison with the data of field observations make it possible to determine the reliability of the developed methods and software and thereby determine the vulnerable zones of the earth dam, where the loss of stable operation of the structure is possible. Based on the research results, appropriate recommendations were made.
Mathematical modeling of one-dimensional air movement with dispersed particles in a continuously working pneumatic mixer
Authors: Uvarov V A , Orekhova T N , Chekhovskoy E I , Kachaev A E 
Published: June 2021

Abstract
The improvement of methods and technologies for the production of dry building mixes, dispersed modifiers, dry paints and other finely ground, homogeneous systems is associated with the quality of their compositions, which, in turn, requires the use of high-tech energy-saving equipment. The use of the original pneumatic mixers proposed in the paper makes it possible to obtain high-quality multicomponent mixtures due to the specially organized movement of the two-phase flow meeting with the peripheral supply of the energy carrier. Forecasting and analyzing the dynamics of two- and multiphase systems distributed in the air in units of this type allows assessing the nature of the technological process of mixing components, while a mathematical description of the complex movement of particles in the air flow allows obtaining a result that helps to characterize the operating modes of the pneumatic mixer, which is important when operating this machine in production. The paper presents a method for numerical simulation of the axisymmetric motion of a two-phase flow in the homogenization chamber of a pneumatic mixer, which allows setting adequate operating modes of the unit for various dispersed systems mixed in it. The main assumptions in the construction of the mathematical model are also reflected, the conditions for setting the problem for this study are formulated, and the results are obtained in the form of analytical expressions of the main dynamic parameters of the flow with particles for the volume of the mixing chamber, depending on the design features of the pneumatic mixer.
Ratio of the ash concentration to the cement binder in the composition of concrete with the use of a modified additive
Authors: Lukpanov R E , Dusembinov D S , Yenkebayev S B , Tsygulyov D V 
Published: June 2021

Abstract
The paper presents studies of cement-ash binder in the composition of concrete with the use of a complex modified additive (CMA). The research is aimed at improving the conditions for the production of concrete works, in particular, improving the workability of a concrete mixture based on ash-cement binders. The main evaluation criterion of the study was the change in the viscosity of the composition with a change in the water-binding ratio. The measurements were carried out in two stages: at the first stage, the influence of the ash component on the water-binding ratio was estimated, at the second stage, the issue of changing the viscosity over time was considered. Laboratory tests were carried out using adapted methods for measuring the spread of the mixture and determining the setting time. According to the results of the first stage, the regularities of changes in the viscosity of the mixture by changing the water content were obtained, and the optimal ratios of water to the binder were obtained, depending on the percentage of the ash component. According to the results of the second stage, the regularities of changes in the viscosity (from the liquid to the solid state) of the mixture over the holding time, depending on the same percentage of ash were obtained. In conclusion, the data on the optimal water-binding ratio from the conditions for the manifestation of the ash-cement mixture of texotropic properties corresponding to the classical cement mixture, without the inclusion of ash, are presented.
Reduction of plane-radial freezing - thawing problems to plane-parallel ones
Authors: Aksenov B G , Abrosimova S A , Rydalina N V 
Published: June 2021

Abstract
Construction in northern conditions is complicated by the processes of seasonal freezing and thawing of soils. This factor is of particular importance in the area of permafrost distribution. The paper deals with the problems that arise when laying communication networks. Any engineering solution must be justified by a heat engineering calculation. In one case, it is necessary to exclude the thawing of water or sewer networks, in the other case – to prevent the destructive effect of the heating main on the permafrost soil. The most common mathematical model of the heat transfer process in the presence of phase transitions is the Stefan problem. When calculating the processes of freezing-thawing near the pipes of communications, it is rational to set the problem in cylindrical coordinates, using the property of plane-radial symmetry. But the Stefan problem has an exact solution only in Cartesian coordinates, for the case of plane-parallel symmetry. For this case, many approximate dependencies are also obtained. The paper presents a method that allows using the results of solving the plane-parallel Stefan problem to solve the plane-radial problem with the same values of the input parameters. Approximate values of the coordinate of the phase transition front as a function of time for the plane-parallel and plane-radial areas are obtained using the method of sequential change of stationary states. A one-to-one relationship is established between the obtained values. If there is a solution obtained by any method for a plane-parallel area, and then using this dependence, it can be applied to a plane-radial area. This technique is suitable not only for the Stefan problem, but also for many nonlinear heat conduction problems. The results given in the paper are of practical importance: using the above method, almost any solution obtained for one type of symmetry directly extends to other types of symmetry.
The model of formation of the spatial organization of shift settlements
Authors: Kh Ishmametov R 
Published: June 2021

Abstract
The purpose of the study contains two main aspects: - improvement of the spatial organization of the shift settlement of the oil and gas industry - the potential of the structure-forming component of the country’s settlement system; - development of the optimal functional and planning structure of the morph types of the shift settlements, providing a high level of comfort that meets the increasing needs of a modern, dynamically developing society. Comprehensive review of the existing forms of spatial organization of shift settlements is carried out on the example of foreign and domestic experience in the design, construction and operation of shift settlements at various stages of development in order to identify the intensity of their formation and determine the most perspective type, as a basis for development and the subject of further research. The vector of external and internal, first of all, production -technological and social factors influencing the morphology of shift settlements and the structure of territorial settlement in the system of industrial development of the natural complex is determined. The evolutionary transformations of the morphology of shift settlements in all countries took place taking into account the factors and characteristics of natural-geographical, climatic, socio-economic aspects and functional-industrial affiliation. Considered the circumstances and features of formation of the architectural and planning organization of shift settlements that affect the creation of an algorithm of gradual development through modernization the quality of its internal spatial structure. The increasing technological potential of the territories stimulated to the formation of typological and classification diversity of the territorial structure and spatial organization of shift settlements, their morphological and taxonomic hierarchy. On the basis of a concept formulated a predictive theoretical model of the holistic shift space settlements, with the functional program of the formation of the quality of the environment is comparable to quality of life in large urbanized space with respect to information-technology resource of the modern world, shaping the potential for sustainable development.
Features of thermal decomposition of titanium hydride fraction
Authors: Pavlenko V I , Yastrebinsky R N , Bondarenko N I , Kuprieva O V 
Published: June 2021

Abstract
One of the areas of work on the technology of producing products based on titanium hydride fraction HTK-D is the study of methods and modes of modifying the surface of titanium hydride fraction in order to increase its thermal stability at high temperatures and protect titanium from oxidation. The research was carried out using modern instrumental physical methods and physical and chemical analyses. Differential thermal and thermogravimetric analyses of the initial and modified titanium hydride fractions were performed in the temperature range of 20-1000 °C in the air atmosphere. The curves TG and DTG of the initial fraction of titanium hydride show a slight change in mass in the temperature range of 20-100 °C with a maximum at T– 82 °C, which is associated with the removal of sorbed moisture. The data of the DTG analysis showed that the modification of the titanium hydride fraction with sodium borosilicate leads to a noticeable decrease in the mass loss of the samples: in the temperature range of 600-900 °C, the mass loss for the modified titanium hydride fraction was 0.39 and 1.58% (wt.) for the initial fraction of titanium hydride. In the course of the experiment, it was revealed that a further increase in the temperature leads to an increase in the mass of titanium hydride fraction samples, which is a consequence of titanium oxidation. It was found that the modification of the titanium hydride fraction with sodium borosilicate increases its thermal stability.
Joukowski’s wake model for tip-splitting rotors
Authors: Castillo-Castellanos A , Durán Venegas E , Le Dizés S 
Published: June 2021

Abstract
The interaction between a tip vortex and a solid surface is responsible for premature structural component fatigue in wind turbines and undesirable noise in helicopter rotors during low speed and descending flight. One noise reduction strategy uses a modified airfoil to split and spread the vorticity in two tip vortices. The present paper aims to provide the wake structure produced by such a rotor for wind turbine and helicopter regimes. We use a filamentary approach, such that vortices are assumed to roll-up quickly to form thin vortex filaments of finite but small size and compute the induced velocity using a cut-off method. The structure of the wake is analyzed in the near- and far-fields separately. It is found to have a dual nature and to be well-described by a twisted vortex pair locally aligned along with a larger helical structure. The linear stability of the far-wake with respect to long-wave displacements is also analyzed. Two kinds of instability modes are obtained associated with a pairing between successive turns of the large helical structure and a pairing between successive turns of the vortex pair.
Deformation and wake of a flexible rotor in water
Authors: Eldemerdash A S , Leweke T 
Published: June 2021

Abstract
In this paper, we study experimentally the fluid-structure interaction of a simplified small-scale rotor operating in a water channel. The rotor consists of a single untwisted rectangular blade and is tested with various pitch angles at different rotation speeds and free stream velocities. Flapwise blade deformations are measured using image processing, and flow fields are obtained by Particle Image Velocimetry. The blade exhibits extreme downstream and upstream bending at high negative and positive pitch angles, respectively. In addition, for negative pitch angles, unsteady flapwise fluctuations are observed, accompanied by large-scale recirculation zones. These zones are formed and shed periodically behind the rotor, resembling the dynamics of the Vortex Ring State known for helicopters in steep descent. The induced axial velocity near the blade tip changes direction from upstream to downstream, in accordance with the bending direction, reaching values that exceed twice the free-stream velocity in extreme bending conditions. The blade deformation has a strong dependence on the tip speed ratio for low pitch angles, and a more pronounced dependence on the tip Reynolds number for high pitch angles. Results for a two-bladed rotor are also shown and compared to the behaviour observed for a single blade.
Wind turbine wake inflow over a heterogeneous forest - comparison between measurement and LES simulation
Authors: Navarro Diaz Gonzalo P. , Arnqvist Johan , Ivanell Stefan 
Published: June 2021

Abstract
In this work a new step in understanding the wind turbine (WT) wake behavior on forested areas is made. For this analysis, a pair of real scale WTs located on a site with moderately complex terrain and heterogeneous forest is simulated using Large Eddy Simulation (LES). This simulation is compared with met mast and power output measurements of two WTs in Ryningsnas, Sweden, considering near neutral stratification in the atmospheric boundary layer (ABL). Three validation steps are followed; first, the undisturbed wind profile is compared with met mast data and another similar LES code. Then, the wake for each WT wake impacting on the met mast at different directions is addressed. A feature of this pair of WTs is that these have different hub heights, but the same rated power and rotor diameter, which helps provide insight into how the tip clearance over the forest affects the operation and wake characteristics. Finally, power output deficits when the WTs are operating in each others wakes are compared to observed power deficits. For these simulations SOWFA, the Open FOAM project for wind farms simulation in ABL, is used. In this code, three new additions are made; the forest model, the mesh modification for complex terrain and the representation of the WT using an actuator disc model with local force adaptation for wind farm flows. The simulation results show a good performance on quantitatively and qualitatively capturing the velocity in the wake, but for TKE the simulation underestimates the magnitude, and fails to match the measured structure of the wake for one of two WTs. The power deficit on the impacted WTs is well captured, despite the complexity related to turbines with different hub heights. This study makes one of the first steps on validating LES simulations for wind farms in forest.
A Quantitative Comparison of Aeroelastic Computations using Flex5 and Actuator Methods in LES
Authors: Hodgson E L , Andersen S J , Troldborg N , Forsting A Meyer , Mikkelsen R F , Sørensen J N 
Published: June 2021

Abstract
Actuator disc and actuator line techniques are widely used for modelling wind turbines operating in wind farms. These techniques essentially replace the blade geometry with applied body forces, which reduce the resolved length scales significantly and hence the required grid resolution. This work is a verification of the coupling between the flow solver EllipSys3D and the aeroelastic tool Flex5, through a quantitative comparison of coupled actuator line, coupled actuator disc, and standalone Flex5. Steady state performance predictions, instantaneous reaction to turbulence and damage equivalent load analyses all show a very good agreement between the three methods. Differences can be explained primarily by the higher fidelity modelling of the coupled simulations; this is particularly in regard to the influence of blade flexibility, as the actuators deflect and interact with the modelled flow. Additionally, some overpredictions of loading at the blade tip and root below rated velocity for the actuator methods can be attributed to the Gaussian smearing used to apply the body forces.
Evaluating wind farm wakes in large eddy simulations and engineering models
Authors: Stieren Anja , Stevens Richard J. A. M. 
Published: June 2021

Abstract
We study wind farm wakes with large eddy simulations (LES) and use these results for the evaluation of engineering models such as the Jensen model, the coupled wake boundary layer model (CWBL), the Turbulence Optimized Park model (TurbOPark), and the wind farm model developed by Niayifar and Porté-Agel (Energies 9, 741 (2016)). We study how well these models capture the wake effects between two aligned wind farms with 72 turbines separated by 10 kilometers in a neutral boundary layer. We find that all considered models over-predict the wind farm wake recovery compared to what is observed in LES. The TurbOPark model predictions on the wind farm wake effect are closest to the LES results for the scenario considered here.
Feasibility assessment of climate change adaptation options across Africa: an evidence-based review
Authors: Williams Portia Adade , Simpson Nicholas Philip , Totin Edmond , North Michelle A , Trisos Christopher H 
Published: June 2021

Abstract
Considering the feasibility and effectiveness of adaptation options is essential for guiding responses to climate change that reduce risk. Here, we assessed the feasibility of adaptation options for the African context. Using the Global Adaptation Mapping Initiative, a stocktake of adaptation-related responses to climate change from the peer-reviewed literature in 2013–2020, we found 827 records of adaptation actions in Africa. We categorised and evaluated 24 adaptation options and for each option, six dimensions of feasibility were considered: economic, environmental, social, institutional, technological, and evidence of effectiveness. Over half (51%) of all adaptation actions were reported in the food sector where sustainable water management (SWM) was the most reported option. The fewest actions were reported for cities (5%). The majority of actions (53%) were recorded in just six countries: Ghana, Ethiopia, Kenya, Tanzania, Nigeria and South Africa. Encouragingly, effectiveness was assessed as medium or high for 95% of adaptation options. However, no options had high feasibility on any other dimension. Technological and institutional factors present major barriers to implementation. Crop management, SWM, sustainable agricultural practices, agroforestry, livelihood diversification, ecosystem governance and planning, health governance and planning, infrastructure and built environment, all had moderate feasibility across three or more dimensions. Human migration has low feasibility but high potential for risk reduction. Major knowledge gaps exist for environmental feasibility, for assessing adaptation limits at increasing levels of climate hazard, for economic trade-offs and synergies, and for Central and Northern Africa. Our results highlight sectors where enablers for adaptation can be increased. Future assessments can apply the method established here to extend findings to other national and local levels.
The arrangement of Hamdan Sukaraja Slum Settlements in Medan Indonesia, through the concept of affordable vertical village
Authors: Tanjung Z , Fitri I 
Published: June 2021

Abstract
Initially, the city of Medan consisted of villages, often called urban villages, which evolved to form cities. Sukaraja and Hamdan villages are old villages that are part of the Sultanate of Deli and reflect the sociocultural character of the local people of Medan. Now, these villages have grown to the banks of the Deli River. The residents choose to live in riverbank areas that are not well-designed and create unhealthy slums that have social, economic, and cultural problems. These villages will be displaced soon by the discourse of the toll project in the city of Medan on the Deli River. This paper aims to analyze and provide solutions to the problems of the development of slums in the Deli River area. Both environmental, architectural, social, and economic issues of the population. Based on data analysis, the people of Hamdan and Sukaraja villages need livable housing at an affordable cost and can support the community’s economy. This study recommends a vertical village design with an Ecological Architecture approach and integrated with sustainable economic systems. The vertical village design also accommodates the economic empowerment of Sukaraja and Hamdan villagers by developing and integrating businesses that have grown previously in this village.
Identification building mass pattern placement in the central government complex
Authors: Ashila T I , Kridarso E R , Iskandar J 
Published: June 2021

Abstract
Central governement complex is a place for organazing politics and adminitrative activities between government and society. Central government complex consists of some buildings that are adjusted to the organizational structure of the government, accompenied by its facilities and infrastructure. Each central government area should have a certain pattern that is considered the most suitable for its site. Determination of the pattern and the placement of building masses in the central government complex is important, because of its effect on the effectiveness and efficiency of the activities in it. This study uses a qualitative-comparative method by comparing the complex’ patterns and building mass placement at Tangerang Regency Government Center, Bandung Regency Government Center, Sejong City Administrative Complex, South Korea, and Tamar Government Center Complex, Hong Kong. This study results in an alternative range of optimal building mass pattern placement in the central government complex.