Natural convection in an annular space provided with metal foam fins attached to the inner cylinder is studied numerically. The metal foam fins made of copper were inserted in different axial sections with three fins in each section. The temperature of the inner cylinder is kept constant while the annular outer surface is adiabatic. The thickness effect of the inner pipe wall was considered. Naiver Stokes equation with Boussinesq approximation is used for the fluid regime while Brinkman-Forchheimer Darcy model is used for metal foam. In addition, the local thermal non-equilibrium condition in the energy equation of the porous media is presumed. The effect of Rayleigh number and number of foam fins in the axial direction, on fluid flow and heat transfer characteristics, were examined. The current model was valid with the available published results and good agreement is noticed. Results showed that as the Rayleigh number increases the dominated of convection mode increases and average Nusselt increases. It was found that at Rayleigh of 106 Nusselt reached its higher value which is 4.6 for the case of adding seven axial metal foams. A comparison between adding foam fins and copper fins was established for a range of Rayleigh numbers between 104 and 106. It showed a good enhancement in Nusselt number and the greatest enhancement percentage was 45.9% at Rayleigh equal 106 for the case of using seven sections of foam fins. |
This paper aims to prove an existence theorem for Voltera-type equation in a generalized G- metric space, called the -metric space, where the fixed-point theorem in - metric space is discussed and its application. First, a new contraction of Hardy-Rogess type is presented and also then fixed point theorem is established for these contractions in the setup of -metric spaces. As application, an existence result for Voltera integral equation is obtained.
In this paper, we introduce and discuss an algorithm for the numerical solution of two- dimensional fractional partial differential equation with parameter. The algorithm for the numerical solution of this equation is based on implicit and an explicit difference method. Finally, numerical example is provided to illustrate that the numerical method for solving this equation is an effective solution method.
The electrical performance of bottom-gate/top source-drain contact for p-channel organic field-effect transistors (OFETs) using poly(3-hexylthiophene) (P3HT) as an active semiconductor layer with two different gate dielectric materials, Polyvinylpyrrolidone (PVP) and Hafnium oxide (HfO2), is investigated in this work. The output and transfer characteristics were studied for HfO2, PVP and HfO2/PVP as organic gate insulator layer. Both characteristics show a high drain current at the gate dielectric HfO2/PVP equal to -0.0031A and -0.0015A for output and transfer characteristics respectively, this can be attributed to the increasing of the dielectric capacitance. Transcondactance characteristics also studied for the three organic mater
... Show MoreSome research reports that cognitive grammar (CG) theory has good contributions to teaching English as a foreign language. In this research, the researchers seek to apply this theory and its principles when teaching the simple present tense to Iraqi students who face difficulties in differentiating between the multiple usages of this tense. To achieve this objective, the researchers have conducted an experimental study on a group of 60 Iraqi students in the University of Baghdad, College of Education for Women. Langacker’s (2003) theory has been adopted in the analysis of the cognitive relations to understand the common and different connections of these usages of the simple present. The study has concluded that the cognitive grammar t
... Show MoreSpecialized banks provide their banking activities to their customers at interest rates that are determined according to the approved bank policy, which is almost similar to most or most banks. To satisfy the financial desires of customers and at the same time it is a source of the bank's profits, However, these banks have been introduced to new services that they provide with the funds of the Central Bank initiative launched at the beginning of (2016) to address the economic stagnation that befell the country due to the (financial security) crisis that the country faced in 2014. To put forward initiatives amounting to nearly (15) trillion dinars, which were put forward through private commercial and Islamic banks and specialized
... Show MoreOne of the most frightening to children ages pre-school entry , Are those concerns about natural phenomena such as (The darkness, the sound of thunder, lightning and light, and rainfall, and storms) These natural phenomena are not familiar to the child , It may have a surprise when he/ she sees , And others intimidated , The affects of panic and fears that may lead him some psychological injury symptoms.
The fear of the dark, of the most common concerns associated with the child in his daily life , As the children's fear of the dark is reasonably fear that makes him a natural to live in the unknown , We can not identify what around him and is afraid of something collision, Or injury from somet
... Show MoreThe problem of the damage caused by terrorist acts has raised many difficulties in many countries, including Iraq, which requires the existence of a law that sets out sufficient rules for compensating the victims of terrorist acts, in order to compensate them for the harm they have not suffered. It may be difficult or impossible for them to identify causing damage, and therefore unable to obtain compensation by applying the traditional rules of liability that require proof of fault and identify the culprit. The security funds come as an appropriate alternative that pays compensation in such cases for victims to reparation for the damage they suffered. Therefore, this problem remains one of the most problems that Iraq suffers from it, which
... Show MoreSince the Internet has been more widely used and more people have access to multimedia content, copyright hacking, and piracy have risen. By the use of watermarking techniques, security, asset protection, and authentication have all been made possible. In this paper, a comparison between fragile and robust watermarking techniques has been presented to benefit them in recent studies to increase the level of security of critical media. A new technique has been suggested when adding an embedded value (129) to each pixel of the cover image and representing it as a key to thwart the attacker, increase security, rise imperceptibility, and make the system faster in detecting the tamper from unauthorized users. Using the two watermarking ty
... Show MoreBoth of the species Typha domengensis and Phragmites communis among the most important plant endemic in flora of Iraq from monocotyledon. Due to the similarity of the two species with each other in many morphological characteristics such as the environment where they live and the form of leaves and type of leaf venation and type of stomata….ets, also both of species belong to monocots plant therefore this research work was conducted find anatomical differences that have the same as taxonomic value to help distinguishing between both species under study. Through this research, we found great importance to the anatomical characteristics which we reached by studying the roots, stems and leaves sections f
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