Chemically radiative dissipative MHD Casson nanofluid flow on a non-linear elongating stretched sheet with numerous slip and convective boundary conditions

The flow of a Casson nanofluid across a nonlinear stretching surface with a velocity slip and a convective boundary condition is investigated in this work in the magnetohydrodynamic (MHD) domain. This technique emphasizes a variety of effects, including chemical reaction, viscosity dissipation, and velocity ratio. In this study, Brownian motion and thermophoresis are also illustrated. It is assumed that suction exists while a magnetic field is uniform. The governing nonlinear partial differential equations are converted into a set of nonlinear ordinary differential equations using the required similarity transformations, and the Runge-Kutta-Fehlberg fourth-fifth method is then used to solve the system. The updated results are fairly similar to the earlier ones. The graphs and tables examine how various variables affect the speeds, temperatures, concentrations of substances, skin friction values, Sherwood numbers and Nusselt numbers

Cost-Effective Management of Sea Water Intrusion in Shallow Unconfined Aquifers

The cost efficiency aspects of different hydraulic barriers to control seawater intrusion (SWI) in shallow unconfined aquifer are investigated using the direct integration of simulation model with multi objective optimization tool. Positive barrier by recharging the water into aquifer using subsurface pond, negative barrier by abstraction of saline water and combination of these two are the three scenarios that are optimally assessed in this study. In the descriptive case study considered, the results indicate that application of treated waste water (TWW) as source of recharge increases the efficiency and the practical value of combined management scenario to control SWI

Environmental determinants of the ecology and distribution of Acacia tortilis under arid conditions in Qatar

PhD ThesisScrub or woodland communities dominated by Acacia tortilis form one of the few tree-dominated natural ecosystems in the hyper-arid climate of Qatar, making it a very important tree species that provides an essential habitat both for native animals and domestic livestock. However, the conservation and sustainable management of this tree has so far been neglected and it is now severely impacted by overgrazing and wood fuel collection. This research investigates the main environmental, ecological and management factors affecting the growth and distribution of Acacia tortilis in Qatar, including the factors affecting its regeneration. It also aims to guide the implementation of conservation programmes and development of a strategy to forestall deforestation and prevent the extinction of Acacia tortilis in Qatar. Initially, field survey, remote sensing and GIS techniques, together with univariate and multivariate statistical modelling techniques, were used to explore environmental influences on distribution of A. tortilis in Qatar at a national scale. Different vegetation indices (VIs), normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), were derived for a time series of Landsat TM/ETM+ images for 1998 and 2010 and tested using ground-truth data to explore the temporal dynamics of Acacia-dominated ecosystems which indicated substantial reduction in vegetation greenness in 2010 than 1998. The initial approach had limited success due to difficulties of identifying Acacia tortilis communities accurately on satellite images due to the sparsity of tree cover and indicates the limitations of using remote sensing methods for tracing vegetation dynamics in Qatar and similar arid and hyper arid environments. The multinomial logistic regression model has a superior ability to predict Acacia distribution and is a suitable method in the prediction of the occurrence of different vegetation types. Phytogeographical investigations of the environmental and biotic factors that control the distribution of the Acacia tortilis at a local scale, in both areas protected and unprotected from human land use impacts, demonstrate that topographic factors and their control on soil and water conditions are fundamental determinants. The distinctive topography of Qatar has resulted in a heterogeneous soil landscape with extreme contrasts of chemical and physical soil conditions within and between depressions and more elevated positions in soil toposequences. Depressional land forms are more suitable for the Acacia tree growth than the surrounding higher ground because ENVIRONMENTAL DETERMINANTS OF ACACIA TORTILIS IN QATAR II depression soils have greater soil water content, soil depth, organic carbon and available phosphorus contents. Conversely, the absence of Acacia trees in summit areas is related to severe limitations for tree growth, including negligible soil water content and shallow soil depth caused by impeding bedrock or cemented horizons resulting in drought stress, as well as large contents of gypsum and/or CaCO3 in soils. The slope-controlled movement of eroded soil material, water and plant debris, and the localised leaching of soluble salts, are suggested to be important processes that lead to improved soil quality and better tree growth in depressions. The regeneration of Acacia tortilis through seedling establishment is perhaps surprisingly shown to be greater in the unprotected than in protected areas. This is attributed to the importance of ingestion by large mammals (mainly domestic herbivores) on the germination and recruitment of Acacia seedlings. The greater frequency of Acacia saplings in depressions within the unprotected areas is, however, also attributed to the presence of greater amounts of soil water, soil depth, available phosphorus, and organic carbon. Although the action of browsing may be regarded as positive, most anthropogenic impacts were shown to have negative effects on the condition and distribution of Acacia tortilis. The results proved that the impacts of cutting and browsing were severe in the unprotected sites, despite the evidence of more active regeneration. It is concluded that there is an urgent need to review the provision and management of protected habitats for Acacia tortilis in Qatar. It is suggested that cutting for domestic use should be restricted; that conservation efforts should be concentrated in depressions that favour tree growth; and that the livestock numbers should be limited to enable seedling establishment without excessive browsing.“Qatar University”, for sponsoring my Ph.D. researc

Image Formation Free Rotation in Triple Pole-Piece Magnetic Lenses

Present work is mainly concern with the mathematical function, considered to represent the axial magnetic flux density distributions of proposed triple pole-pieces magnetic lenses which is used as rotation free lenses. This function has, in fact, three-optimization parameters. The only important parameter is the bore radius of the lens in the proposed model. This parameter can be affect on the projector properties of the lens, when the other two optimization parameters (maximum value of flux density and lens length) are constants, where the literature survey proved that unaffected on the lens properties. Results have clearly shown that the optimization parameter for current function, have a considerable effect on the lens distortion, lens magnification, and the reconstructed pole-pieces. Furthermore, the results obviously show the excellent ability for converting the form of the chosen mathematical function in order to represent the magnetic field of triple pole-pieces lenses. Keywords: Electron Optics, Projector Lens, Distortion, Magnificatio

Numerical modelling of the impacts of sea level rise on seawater intrusion in unconfined coastal aquifers

Copyright © 2014 the University of Exeter.This study presents the application of a density-dependent finite element model to simulate the transient effects of sea level rise (SLR) on seawater intrusion (SWI) in a conceptual case of unconfined aquifer. The model considers both the unsaturated and saturated flow conditions. To model the natural process of SLR, a time-dependent boundary condition is used to define the hydrostatic head imposed by seawater at the coastal boundary where the effect of the gradual rise in the sea level with time is considered. The specified values of SLR are chosen, in the range of that predicted by IPCC (Intergovernmental Panel on Climate Change), for five different periods of time in the current century (from 2014 to 2100). The results indicate that a considerable advance in SWI can be expected in the coastal aquifers until the end of century. The rising of sea level is followed by the lifting of the groundwater table, especially near the shoreline, which gradually declines towards the inland boundary. The effects of spatial variations of the shoreline slope on SWI under SLR condition are also investigated. The results highlight that the flatter slopes of the shoreline intensify the landward process of seawater intrusion

Optimal control of seawater intrusion in coastal aquifers

Seawater intrusion is one of the most serious environmental problems in many coastal regions all over the world. This is because mixing a small quantity of seawater with groundwater makes it unsuitable for use and can result in abandonment of aquifers. Therefore, seawater intrusion should be prevented or at least controlled to protect groundwater resources. This paper presents a new method for optimal control of seawater intrusion. The proposed method is based on a combination of abstraction of saline water near shoreline and recharge of aquifer using surface ponds. The source of water for the surface pond could be treated waste water or excess of desalinated brackish water (if any), etc. The variable density flow and solute transport model, SUTRA, is integrated with a Genetic Algorithm optimization tool in order to investigate the efficacy of different scenarios of the seawater intrusion control in an unconfined costal aquifer. The locations of the pond and the abstraction well in relation to the shoreline, depth of abstraction well and the rates of abstraction and recharge are considered as the main decision variables of the optimization model, which aims to minimize the costs of construction and operation of the abstraction wells and recharge ponds as well as the salt concentrations in the aquifer. Comparison is made between the results of the proposed method and other methods of seawater intrusion control. The results indicate that the proposed method is efficient in controlling seawater intrusion. This proposed strategy can be considered as a powerful tool for cost-effective management of seawater intrusion in coastal aquifers

Relationship between Economic Growth and Debt: An Empirical Analysis for Sub-Saharan Africa

In this study, we examine the connection between economic growth and debt, with the question in mind -“Is debt a burden and bad for economic growth? Employing several sophisticated statistical approaches to investigate the problem and to assess the impact of debt on economic growth in 48 countries of Sub-Saharan Africa from 1995 to 2012, we find evidence of Granger causality between debt and economic growth in 8 out of the 48 sub-Saharan countries during the period of study and validate for the existence of “Debt Laffer Curve.” We also study the relationship between debt and economic growth rate in Granger causality and Dynamic Arellano-Bond panel data estimation frameworks, and find evidence of a negative correlation between the two variables (Debt and GDP) and confirm the findings by testing several versions of the models. Political decision and economic policy are intertwined and need to be examined carefully when implemented for economic growth and our findings lend credence to the politically unpopular austerity measures (constraints on government spending financed by borrowing). There is a limit to the economic growth rate that the government financed expenditure can bring. If the burden of debt is too high then there is a negative impact of debt on the economic growth.Keywords. Economic Growth, Debt, Laffer curve and Investments.JEL. E20, E60, E24

Modulating Mathematical Function to be used in Electron Objective Lens

A theoretical study has been carried out on the magnetic field resulting from a modulating mathematical function to produce a magnetic pole to be used for designing the objective magnetic lens in the electron optical devices. This function has only one effective optimization parameter (a) which is named half of the half-width of the magnetic field that can affect on the design and focal properties of the magnetic lens. At first we will be seen the peak of the magnetic field shifted out of a symmetry point (z=0) by a distance approximately equals to the half half-width of the magnetic field. Therefore, some axial transformations have been carried out to make this peak symmetric around the symmetry axis. The present work has shown the possibly of obtaining a magnetic pole of the magnetic field in which the peak shifted off symmetry point. Keywords: Electron optics, Objective Magnetic Lenses, Aberration