ANALYSIS AND OPTIMIZATION OF FRICTION WELDING PARAMETERS FOR AA6061-AA2014 DISSIMILAR JOINTS

Friction welding is a solid state welding used owing to its properties such as low heat input, high production efficiency and environment friendliness. Materials which aredifficult towelded by fusion welding processes can be successfully done friction welding. In this work, an effort was made to predict the maximum tensile strength of friction welded AA 6061 and AA 2014 aluminium alloy dissimilar joints incorporating the process parameters such as rotational speed, friction pressure and forging pressures which have immense on the strength of joints. The friction welding process parameters were optimized to achieve maximum tensile strength of the joint. The maximum tensile strength of 210MPa  for the joints fabricated under the welding conditions ofrotational speed 1508 rpm, friction pressure of 8.16 MPa/secand forging pressure of 6.79 MPa/sec using the optimization techniques

An Efficacious and Secure Registration for Internet Protocol Mobility

For the ample development of mobile internet protocol (IP) technology and the recurrent movement of a mobile device, it is necessary for the mobile device to inform their home network where initially registered through an efficient and secured procedure against any sort of attacks. The procedure of registration for IP mobility by the portable system must have a better performance by providing a certain level of security, such as authentication, integrity, replay attack protection, and location privacy. All at once, the extreme security in the registration of IP mobility may cause long registration time, principally for real-time systems. This paper mainly deals with a balanced effort for secure and efficient registration procedure which gives better security and efficiency in terms of registration delay. The proposed work provides an easy and fast registration procedure and lessens the registration delay through the usage of an identity based authenticated key exchange scheme that eliminates expensive pairing operations. The proposed protocol is verified by using AVISPA tool. The performance evaluation reveals that the proposed protocol significantly outperforms the existing protocols in terms of the registration delay.Defence Science Journal, 2013, 63(5), pp.502-507, DOI:http://dx.doi.org/10.14429/dsj.63.400

The Reasons for the Poor Achievement of Students in the Three Basic Grades in Reading and Ways to Address Them from the Point of View of Teachers

This study aimed to identify the reasons for the poor achievement of students in the first three grades in reading from the teachers\u27 point of view and ways to address them, and in order to achieve the desired objectives of the study. (35) schools were selected using a simple random sampling method out of (51) schools, and (100) teachers were selected from these schools out of (300) male and female teachers at a rate of 30%, and an opinion poll was conducted for (25) teachers of the basic stage , from the first to the third grade of the Deir Alla District Directorate. The researcher used a questionnaire as a tool that she prepared to achieve the objectives of the study, which consisted of (14) paragraphs. The study concluded at the total level that the degree of weakness was high, due to the reasons for weakness in the field of reading, with an arithmetic mean (3.86) and a standard deviation (.53), and the number of The paragraphs that got a high degree of weakness (10), and the number of paragraphs that got a medium degree of weakness (4). Among the results of ways to treat poor reading that ranked first is the paragraph that states that students’ tendencies and desires are taken into account while writing school books in light of the achieved results, at a rate of (20%), and the paragraph that got the lowest degree of weakness, the paragraph that states that students should be involved in the radio school at a rate of 4%. The researcher reached some recommendations that she recommends, including the need to reduce the frequent absence of students from school, through communication between school and home. And the development of teachers of the stage professionally, by training them on everything new in the methods of teaching reading, and informing them about the basics of teaching students of the first three grades, especially reading, and emphasizing the importance of training teachers during the service, on new and modern teaching methods for reading. And taking into account the importance of the diagnostic evaluation of students at the beginning of the school year and the semester, and raising the teachers’ awareness of that and following them up by their supervisors through periodic visits to them during the school year, to find out the strengths and weaknesses of each studen

Thermodynamic Consistency of Plate and Shell Mathematical Models in the Context of Classical and Non-Classical Continuum Mechanics and a Thermodynamically Consistent New Thermoelastic Formulation

Inclusion of dissipation and memory mechanisms, non-classical elasticity and thermal effects in the currently used plate/shell mathematical models require that we establish if these mathematical models can be derived using the conservation and balance laws of continuum mechanics in conjunction with the corresponding kinematic assumptions. This is referred to as thermodynamic consistency of the mathematical models. Thermodynamic consistency ensures thermodynamic equilibrium during the evolution of the deformation. When the mathematical models are thermodynamically consistent, the second law of thermodynamics facilitates consistent derivations of constitutive theories in the presence of dissipation and memory mechanisms. This is the main motivation for the work presented in this paper. In the currently used mathematical models for plates/shells based on the assumed kinematic relations, energy functional is constructed over the volume consisting of kinetic energy, strain energy and the potential energy of the loads. The Euler’s equations derived from the first variation of the energy functional for arbitrary length when set to zero yield the mathematical model(s) for the deforming plates/shells. Alternatively, principle of virtual work can also be used to derive the same mathematical model(s). For linear elastic reversible deformation physics with small deformation and small strain, these two approaches, based on energy functional and the principle of virtual work, yield the same mathematical models. These mathematical models hold for reversible mechanical deformation. In this paper, we examine whether the currently used plate/shell mathematical models with the corresponding kinematic assumptions can be derived using the conservation and balance laws of classical or non-classical continuum mechanics. The mathematical models based on Kirchhoff hypothesis (classical plate theory, CPT) and first order shear deformation theory (FSDT) that are representative of most mathematical models for plates/shells are investigated in this paper for their thermodynamic consistency. This is followed by the details of a general and higher order thermodynamically consistent plate/shell thermoelastic mathematical model that is free of a priori consideration of kinematic assumptions and remains valid for very thin as well as thick plates/shells with comprehensive nonlinear constitutive theories based on integrity. Model problem studies are presented for small deformation behavior of linear elastic plates in the absence of thermal effects and the results are compared with CPT and FSDT mathematical models

Channel Estimators for Full-Duplex Communication using Orthogonal Pilot Sequences

Full-duplex communication is desirable to maximize the spectral efficiency, despite the challenges it puts forth. The key challenge inhibiting the operation of radios in full-duplex mode is self-interference. In this paper, we propose a pilot-based channel estimation to estimate both self-interference and communication channels simultaneously at both ends of a full-duplex link using orthogonal sequences. The Cramer-Rao Lower Bound for estimators of both the channels was determined and compared with the half-duplex channel estimator. We performed simulations varying sequence length and channel taps and studied the performance of the estimators. We also studied the effect of synchronization between the sequences on the performance of the estimators. Thus, providing a solution to balance the trade-off between the accuracy of the channel estimation and the overhead added to the transmissions for full-duplex communication