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Computation of certain topological coindices of graphene sheet and C 4 C 8(S) nanotubes and nanotorus

Abstract

Topological indices are widely used for quantitative structure-activity relationship (QSAR) and quantitative structure-property relationship (QSPR). Topological coindices are topological indices that considers the non adjacent pairs of vertices. Here, we consider the following five well-known topological coindices: the first and second Zagreb coindices, the first and second multiplicative Zagreb coindices and the F-coindex. By using graph structural analysis and derivation, we study the above-mentioned topological coindices of some chemical molecular graphs that frequently appear in medical, chemical, and material engineering such as graphene sheet and C 4 C 8(S) nanotubes and nanotorus and obtain the computation formulae of the coindices of these graphs. Furthermore, we analyze the results by MATLAB and obtain the relationship of the coindices which they describe the physcio-chemical properties and biological activities.

Open access
Identification of the initial temperature from the given temperature data at the left end of a rod

Abstract

This study aims to investigate the problem of determining the unknown initial temperature in a variable coefficient heat equation. We obtain the existence and uniqueness of the solution of the optimal control problem considered under some conditions. Using the adjoint problem approach, we get the Frechet differential of the cost functional. We construct a minimizing sequence and give the convergence rate of this sequence. Also, we test the theoretical results in a numerical example by using the MAPLE® program.

Open access
Modelling the time-dependent behaviour of soft soils

Abstract

Time dependence of soft soils has already been thoroughly investigated. The knowledge on creep and relaxation phenomena is generally available in the literature. However, it is still rarely applied in practice. Regarding the organic soils, geotechnical engineers mostly base their calculations on the simple assumptions. Yet, as presented within this article, the rate-dependent behaviour of soft soils is a very special and important feature. It influences both the strength and the stiffness of a soil depending on time. It is, thus, significant to account for time dependence in the geotechnical design when considering the soft soils. This can result in a more robust and economic design of geotechnical structures. Hence, the up-to-date possibilities of regarding creep in practice, which are provided by the existing theories, are reviewed herein.

In this article, we first justify the importance of creep effects in practical applications. Next, we present the fundamental theories explaining the time-dependent behaviour of organic soils. Finally, the revision of the existing constitutive models that can be used in numerical simulations involving soft soils is introduced. Both the models that are implemented in the commercial geotechnical software and some more advanced models that take into account further aspects of soft soils behaviour are revised. The assumptions, the basic equations along with the advantages and the drawbacks of the considered models are described.

Open access
Soret and Dufour effects on chemically reacting mixed convection flow in an annulus with Navier slip and convective boundary conditions

Abstract

This analysis is to study the incompressible mixed convection laminar Newtonian flow through concentric cylindrical annulus associated with slip and convective boundary conditions. This presentation considered the cross diffusions and chemical reaction effects also. The fluid flow in an annulus is due to the rotation of the outer cylinder with constant velocity. The analysis of such kind of fluid flow is governed by nonlinear partial differential equations. The governing system of equations were mapped into dimensionless system with appropriate transformations. The system has been solved using Homotopy Analysis Method (HAM). The influence of Soret, Dufour, slip parameter and the chemical reaction parameter on velocity, temperature and concentration are investigated, and presented through plots. The maximum values of slip leads to increase in velocity and temperature profiles. Further the impact of boundary conditions on velocity, temperature and concentration are also presented.

Open access
Aspects Regarding the Commercial Profitability of the Companies from Localities on the Coastal Area of Tulcea County

Abstract

The purpose of this paper is the analysis of the business environment in the coastal area of Tulcea county, by administrative-territorial units, with the help of a synthetic indicator to appreciate the economic-financial performance, the profit rate. The analysis was performed for year 2018, the economic phenomena and processes being captured at the spatial level. The results obtained from this work support the strategy for the rehabilitation of the coastal zone in order to increase the economic performances by adopting policies corresponding to the new realities.

Open access
The assessment of the physicochemical quality of water intended for irrigation of Oued Méskiana (Oum El Bouaghi) Algeria

Abstract

The aquatic ecosystem of the Meskiana Valley (wilaya of Oum El Bouaghi) covers a large area with a permanent flow and a semi-arid climate characterized by a strong evapotranspiration. In order to determine the Physico-chemical quality, pollution and salinity of the water of the river of Meskiana and more particularly in its downstream part which is exposed to wastewater discharges, analyses were carried out at the level of three sampling points: witness, the upstream (before spill), downstream (after spill)). In order to prevent the risk of alkalization and salinization of soil, the sodium absorption rate (SAR) and the percentage of sodium were determined and represented on the Wilcox and Riverside diagram. The high concentrations of polluting chemical elements and excessive salinity obtained at the downstream site show a high risk of pollution and salinization.

Open access
Biodiversity, Distribution and Ecology of Testate Amoebae (Arcellinida and Euglyphida) from the Bulgarian Black Sea Coast and the related brackish lakes. A Synthesis

Abstract

The studies on the marine and freshwater testate amoebae of the Bulgarian Black Sea littoral and some related coastal brackish lakes are briefly reviewed. So far, a total of 184 species and subspecies of testate amoebae from 18 families and 45 genera from orders of Arcellinida and Euglyphida were published in national and international journals. The underground waters of the Bulgarian marine sand supralittoral are better studied than the related continental lakes. A total of about 45 species of marine interstitial testate amoebae are known, so far, and a big part of them were for the first time described from the Black Sea littoral. It’s interesting to note the presence in the marine underground waters of the Black Sea littoral of many freshwater testate amoebae also, considered by us as eurybionts. That is due of the low and variable salinity of the littoral Black Sea waters during the year. The presence of some psammobiotic testate amoebae as Psammonobiotus lineare and Corythionella georgiana in some related brackish lakes is also of ecological interest. The general conclusion of the present synthesis is that the testate amoebae fauna of the Bulgarian Black Sea coast and the related with it many brackish and freshwater littoral lakes is few known yet and need more active researches.

Open access
Business Management Strategies for Business Development. Organization of the Territory and Planning of Construction Works

Abstract

In order for a project to be built with respect to quality, budget compliance and execution time - all required conditions, a professional management of site-level operations is required. The technical complexity, the importance of performing the work on the set deadline, the resource constraints and the substantial costs require the planning, programming and rigorous control of all the works.

Open access
Calculated neutron energy dependence of the dose-response of large recombination chamber

Abstract

A model of REM-2-type chamber was modeled with MCNPX code to study the dose-response to monoenergetic neutrons in wide energy range from thermal to 20 MeV for various compositions of gas in the chamber. The energy dependence of the total dose absorbed in the filling gas was compared with the energy dependence of ambient absorbed dose D*(10) and with experimental data. The results of the studies will be useful for designing new, improved generation of recombination chambers.

Open access
CFD Approach to Modelling Hydrodynamic Characteristics of Underwater Glider

Abstract

Autonomous underwater gliders are buoyancy propelled vehicles. Their way of propulsion relies upon changing their buoyancy with internal pumping systems enabling them up and down motions, and their forward gliding motions are generated by hydrodynamic lift forces exerted on a pair of wings attached to a glider hull. In this study lift and drag characteristics of a glider were performed using Computational Fluid Dynamics (CFD) approach and results were compared with the literature. Flow behavior, lift and drag forces distribution at different angles of attack were studied for Reynolds numbers varying around 105 for NACA0012 wing configurations. The variable of the glider was the angle of attack, the velocity was constant. Flow velocity was 0.5 m/s and angle of the body varying from −8° to 8° in steps of 2°. Results from the CFD constituted the basis for the calculation the equations of motions of glider in the vertical plane. Therefore, vehicle motion simulation was achieved through numeric integration of the equations of motion. The equations of motions will be solved in the MatLab software. This work will contribute to dynamic modelling and three-dimensional motion simulation of a torpedo shaped underwater glider.

Open access