704 research outputs found
Discrete Boltzmann Equation model of polydisperse shallow granular flows
No full textA polydisperse shallow mixture consisting of N p solid phases (N p ≥ 1) and one fluid phase (the ambient fluid) is a reliable model for several industrial and environmental flows, as e.g. landslides, avalanches, debris flows and fluidized beds. The description and prediction of these flows is of primary importance, mainly with respect to the mitigation and protection from natural hazards. This paper is aimed at deriving the polydisperse shallow granular flow equations by depth-averaging mass and momentum equations of the mixture and at formulating an equivalent Discrete Boltzmann Equation (hereinafter DBE) model as solution method. The reason is the simplicity and the versatility of the DBE, which consists of a set of purely advective, linear, first order partial differential equations, whose numerical integration does not need sophisticated methods. Both 1D and 2D benchmarks, concerning with the propagation of discontinuities in three-phase shallow granular flows, are obtained by applying the finite differences Lax-Friedrichs (hereinafter LF) method to the polydisperse shallow granular flow equations. The overall agreement is good, showing that the DBE and the LF numerical results are equivalent
A box-model approach for reservoir operation during extreme rainfall events: A case study
No full textExtreme rainfall events in an urban area pose various challenges to the water resource managers in terms of flood mitigation, inundation, water conservation and harvesting for drinking water supply. The objective of this study is to apply the box-model approach to evaluate reservoir operation during extreme rainfall events. A large water supply reservoir in Chennai was chosen to carry out this study. A box model, based on input–output parameters, is proposed to simulate the reservoir operation and hydraulic behaviour. Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS) has been used to simulate the reservoir inflow hydrograph and to understand the run-off characteristics of the basin. Three extreme rainfall events occurred in past have been selected for the analysis. Three different scenarios have been framed to assess the reservoir performance. Reducing the initial storage to 50% and releasing water at the beginning of the event gives a possible solution for flood mitigation in reducing the outflow volume by 9–37% and delaying the time to peak by 1–6 h. Though the reduced outflow volume from this reservoir is less, it can help to mitigate the flood inundation to a significant extent. Thus the box-model approach presented here can be utilised as a simple tool to generate the various combinations of outflow hydrographs for any reservoir
Groundwater management in alluvial, coastal and hilly areas
No full textGroundwater plays a major role in the modern world being used for drinking, irrigation and industrial development. The increasing population and developments in agricultural and industrial sectors depends on groundwater as it is a reliable source, and so it leads to overexploitation of groundwater without due regard to the recharging capacity of the aquifers. Groundwater extraction from most of the aquifers around the world has exceeded its recharge capacity, and hence the water table has gone down drastically leading to adverse environmental consequences like land subsidence and water quality deterioration. A proper assessment of groundwater resource should be undertaken to ensure sustainable management of groundwater. Hence, the present study proposes empirical methods for the sustainable groundwater resource management in alluvial, coastal and hilly regions
Depth averaged modelling of loose rectangular granular piles collapsing in water
No full textThe collapse of a submerged granular pile under the action of the gravity force is investigated by means of a depth averaged model (hereinafter DAM). The granular pile is a mixture of solid particles and ambient liquid, totally covered by a layer of ambient liquid. The DAM is obtained by depth-averaging the mass and momentum equations of the mixture and the ambient fluid and is aimed at providing estimates of technical quantities regarding the considered phenomenon. The DAM is numerically solved by adopting an equivalent Discrete Boltzmann Equation model (hereinafter DBE) as solution method. The main advantage yielded by the DBE is the possibility to turn the original system of strongly non linear partial differential equations, which would require the resort to complex numerical schemes, into a purely advective, linear, first order one. Previously published experimental and numerical data, relative to the collapse of loose rectangular granular piles in water, are reproduced by the proposed model and a satisfactory agreement is found, revealing that the DAM is able to describe reliably the overall dynamics, in terms of quantities of technical interest as the height of the submerged granular flow and the instantaneous position of its front
INITIAL PRODUCTION OF DEFECTS IN ALKALI-HALIDES - F AND H CENTER PRODUCTION BY NON-RADIATIVE DECAY OF SELF-TRAPPED EXCITON
No full textRadiation damage in KCl can be produced by the decay of a self-trapped exciton into an F centre and an H centre. The authors present calculations of the energies of the states involved for various stages in the evolution of the damage. These lead to important conclusions about the very rapid damage process, and support strongly Itoh and Saidoh's suggestion (1973) that damage proceeds through an excited hole state. The results also help in understanding the prompt decay of F and H pairs at low temperatures, the thermal annihilation of F and H centres, the effects of optical excitation of the self-trapped exciton, and some of the trends within the alkali halides. The calculations use a self-consistent semi-empirical molecular-orbital method. A large cluster of ions is used (either 42 or 57 ions) plus long-range Madelung terms. The ion positions were obtained from separate lattice-relaxation calculations with the HADES code. The choice of CNDO parameters and the adequacy of the method were checked by a number of separate predictions
K-core of co-author network (k = 10).
No full text<p>The size of the node denotes the number of papers and the thickness of interconnecting lines (edges) denotes the number of co-authored papers between the authors. Authors having 10 or more co-author links during the study period have been visualized.</p
Generalized -Closed Sets in Ideal Topological Spaces
No full textThe main focus of this study is to introduce a new category of generalized closed sets, referred to as - closed sets, within the framework of ideal topological spaces. By using a few instances, we demonstrate - closed sets and establish some fundamental properties of -closed sets. We also investigate the relationship between -closed sets and other classes of generalized closed sets in ideal topological spaces, such as - closed sets, -closed sets, and -closed sets. Then, we focus on the topological implications of -closed sets and investigate how they relate to the concepts of -continuous map, -irresolute map, and a strongly -continuous map. First and foremost, we define the -continuous map, investigate the behavior of - continuous map with respect to -closed sets, and derive several important properties of -continuous map. Further, we studied their relationships with other classes of continuous maps in ideal topological spaces. Nevertheless, we defined the definitions of -irresolute maps and strongly -continuous maps in ideal topological spaces. We explored the connections with the notions of -continuous map, -irresolute map, and a strongly -continuous map. Our results provide new insights into the study of ideal topological spaces
Evaluating ERAIVA - a software for video-based awkward posture identification
No full textThe convergence of the focus of Industry 5.0 on human well-being and the prevalent problem of work-related musculoskeletal disorders necessitates advanced digital solutions due to limitations in manual risk assessment methods. This research aimed to compare usability of a newly developed video-based awkward posture identification software, the ergonomist assistant for evaluation (ERAIVA) with a conventional manual method. The risk assessment tool utilised in this study, integrated into the ERAIVA digital platform, is the risk management assessment tool for manual handling proactively (RAMP). Four assessors evaluated video-recorded tasks using both methods (manual and ERAIVA). The usability was assessed through the post-study system usability questionnaire, time consumption, number of video replays and video annotation deletions. The impact on identification of awkward posture durations was also studied. ERAIVA exhibited the highest usability score; it showed a higher number of video replays of specific sequences and annotations without significant differences in time consumption.CC BY 4.0Veeresh Elango: [email protected]</p
Longitudinal trajectories of arterial stiffness and the role of blood pressure: the Baltimore Longitudinal Study of Aging.
No full textCarotid-femoral pulse wave velocity (PWV), a marker of arterial stiffness, is an established independent cardiovascular risk factor. Little information is available on the pattern and determinants of the longitudinal change in PWV with aging. Such information is crucial to elucidating mechanisms underlying arterial stiffness and the design of interventions to retard it. Between 1988 and 2013, we collected 2 to 9 serial measures of PWV in 354 men and 423 women of the Baltimore Longitudinal Study of Aging, who were 21 to 94 years of age and free of clinically significant cardiovascular disease. Rates of PWV increase accelerated with advancing age in men more than women, leading to sex differences in PWV after the age of 50 years. In both sexes, not only systolic blood pressure (SBP) ≥140 mm Hg but also SBP of 120 to 139 mm Hg was associated with steeper rates of PWV increase compared with SBP<120 mm Hg. Furthermore, there was a dose-dependent effect of SBP in men with marked acceleration in PWV rate of increase with age at SBP ≥140 mm Hg compared with SBP of 120 to 139 mm Hg. Except for waist circumference in women, no other traditional cardiovascular risk factors predicted longitudinal PWV increase. In conclusion, the steeper longitudinal increase of PWV in men than women led to the sex difference that expanded with advancing age. Age and SBP are the main longitudinal determinants of PWV, and the effect of SBP on PWV trajectories exists even in the prehypertensive range
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