Non-destructive testing of dissimilar friction stir welds

friction stir welds between 5754 aluminium alloy and C11000 copper. The Friction stir welds of 5754 aluminium alloy and C11000 copper were produced at different tool rotational speeds and feed rates. The tool rotational speed was varied between 600 and 1200 rpm while the feed rate was varied between 50 and 300 mm/min. The visual inspection and the x-ray radiographic testing techniques were employed to conduct the tests; these tests were conducted on the welds to ascertain the joint integrity before characterization to have an idea of the quality of the welds. No visual defects were observed on all the welds considered but the x-ray radiography technique revealed the presence of wormhole defects and discontinuities in some of the welds. It was found that the welds produced at 950 rpm with varied feed rates were the best quality welds produced and this was substantiated with the microstructural evaluation of the joint interface. It was found that these welds have good mixing and metallurgical bonding at the interfaces

Design of a support system for a re-configured milling machine to achieve friction stir welds

The detailed design of a clamping and support system for a reconfigured milling machine to produce friction stir welds is reported in this paper. Two different concepts were considered and subjected to performance evaluation. The selected design concept is expected to effectively clamp and support the workpiece during the process of friction stir welding to achieve a good integrity

Analytic and Numerical Solutions of Time-Fractional Linear Schrödinger Equation

Fractional Schrödinger equation is a basic equation in fractional quantum mechanics. In this paper, we consider both analytic and numerical solutions of time-fractional linear Schrödinger Equations. This is done via a proposed semi-analytical method upon the modification of the classical Differential Transformation Method (DTM). Some illustrative examples are used; the results obtained converge faster to their exact forms. This shows that this modified version is very efficient, and reliable; as less computational work is involved, even without given up accuracy. Therefore, it is strongly recommended for both linear and nonlinear time-fractional partial differential equations (PDEs) with applications in other areas of applied sciences, management, and finance

On a Modified Iterative Method for the Solutions of Advection Model

Variational Iterative Method (VIM) has been reported in literature as a powerful semi-analytical method for solving linear and nonlinear differential equations; however, it has also been shown to have some weaknesses such as calculation of unneeded terms, and time-consumption regarding repeated calculations for series solution. In this work, a modified VIM is applied for approximate-analytical solution of homogeneous advection model. The result attest to the robustness and efficiency of the proposed method (MVIM)

A review of femtocell

The popularity of wireless networks has attracted the attention of researchers to improve the network system and this motivated the operators to find a new technology called femtocells with the aim of meeting the increased coverage and data demand in the indoor environment. The application of femtocells in both indoors and office environment has provided good quality service and high performance network gains. However, femtocells face challenges of interference management which deteriorate the capacity and quality of network. But to cope with these challenges, many researchers have come up with solutions to solve the problems, some of which include interference cancellation and interference avoidance

Modeling of the mechanical responses of nanocrystalline metals and alloys

This paper reports the proposed model of the flow behaviors of nanocrystalline metals and alloys deformed at different strains, strain rates and temperatures. It incorporated the effect of grain size, high internal stresses and lattice distortions existing near boundaries to the Hall-Petch relations. The developed model was compared to that of Khan-Huang-Liang and found to be more reliable in clarifying the inverse Hall-Petch relation. Using the new proposed constitutive model, the mechanical behaviour of materials at different grain sizes for ultrafine grained to nanostructure materials at different temperatures and strain rates can be obtained. The model is also useful in predicting the response of nanocrystalline metals and alloys during the forming process

Overview of interference management techniques in Femtocell networks : challenges and approach.

The most important use of techniques for the new technology network called femtocell, is to improve coverage and enhance capacity in mobile network. However, the deployment of femtocell over macrocell network has a new technology has attracted benefits in telecommunication industry. Several technical challenges toward the mass deployment of these new technology called femtocell have been addressed in industry. Interference mitigation between femtocell and macrocell, and among the neighboring femtocell user, is considered to be one of the major issues in femtocell networks due to sharing the same licensed frequency spectrum with macrocell. In this paper, we provide different techniques schemes for interference mitigation and general view for the efficiency of interference management techniques in femtocell network

A pricing policy to mitigate interference management in femtocell network

Recently, the concepts of game theory has attract the attention of researcher for self-governing decision making to study the performance of wireless network. There has been growing interest in accepting game theoretic method to wireless systems. The problem of interference management in femtocell network is approached from the prospective of game theory with the concept of price policy. Whereby price is used to control the power transmission of each femto users in the cell coverage. In this paper, we propose a price policy to reduce the effect of interference between the femto users at both center and edge regions of cell network. The performance of our proposed algorithm is demonstrated by simulation results

Indoor communication : Femtocell behavior in an indoor environment

The indoor Telecom coverage suffers poor reception, call distortion and low voice calling quality, by signal distortions and interference. In order to improve the quality and performance of voice calls service in the indoor environment, a number of base stations are required. Therefore, femtocells were introduced in the indoor environment for signal booster and other services for end users. Femtocells are deployed in the existing macrocell network coverage to enhance network coverage in an indoor environment. In this paper, we present the simulation base on the signal and the path loss model in the indoor environment, to show that femtocell enhanced indoor communication with improved signal strength without interference

Economic value of Femtocell networks for mobile solution

The deployment of femtocell network in an indoor are used for the purpose of voice calling, data usage, mobile media, internet access and security service which has attracted the attention of economic values for telecom providers. However, femtocell works in the same full frequency band as well as macro cell. The mobile provider would prefer to choose femtocell rather than building macrocell site which leads to its quality of service and increase in profit; and thus, it increases savings compared to site building of macrocell. In this paper, the evaluations of the economic gain and impact factors of femtocell networks in the economy were investigated