Showing papers by "Modern Academy For Engineering & Technology published in 2015"

Torsional vibration reduction for rolling mill’s main drive system via negative velocity feedback under parametric excitation

Abstract: Torsional vibration characteristics are important information for rotating machinery design and control. Jointed shaft is a commonly used element in drive trains of rolling mill. The torsional vibrations of one- degree -of freedom nonlinear dynamical system are controlled using active control. The multiple scale perturbation technique used to get the approximate solution of the differential equation describes the system. The worst resonance cases were deduced and the frequency response function are obtained. The stability and steady state response of the system are studied and discussed numerically. The numerical solutions are focused on both the effects of the different parameters and the system behavior at different resonance cases. To insure the validity of the results, a comparison between the numerical and analytical solution was presented.

Exploring the performance of indoor localization systems based on VLC-RSSI, including the effect of NLOS components using two light-emitting diode lighting systems

Abstract: We analyze the effect of diffuse reflection on indoor localization systems based on visible light communication. The target position is estimated using a received signal strength indication technique. Two lighting systems are considered: distinct and uniform lighting systems. Each utilizes commercially available light-emitting diodes and photodiodes with an illumination level conforming to standards. We introduce a comparative study between the two lighting systems through different transmitter (Tx) and receiver (Rx) essential parameters. The results show that the uniform lighting system achieves less localization error (≤ 20.43 cm ) than a distinct lighting system (≤ 45.9 cm ). The uniform lighting system is well adapted to low-Rx field of view (FOV) and narrow radiation angle ( error = 1 mm when semiradiation angle = 5 deg ). In the case of a distinct lighting system, low-Rx FOV is also required, while the Tx semiradiation angle needs to be determined carefully ( error ≤ 3.08 cm when semiradiation angle = 20 deg ). Finally, the uniform lighting system shows flexibility in the process of Tx and Rx designs. A uniform lighting system can utilize Rxs with narrow FOVs (≥ 8.6 deg ), while a distinct lighting system is limited to Rx with a wide FOV (≥ 53.96 deg ).

2-Killing vector fields on warped product manifolds

Abstract: This paper provides a study of 2-Killing vector fields on warped product manifolds as well as characterization of this structure on standard static and generalized Robertson–Walker space-times. Some conditions for a 2-Killing vector field on a warped product manifold to be parallel are obtained. Moreover, some results on the curvature of a warped product manifolds in terms of 2-Killing vector fields are derived. Finally, we apply our results to describe 2-Killing vector fields of some well-known warped product space-time models.

Passive and active controllers for suppressing the torsional vibration of multiple-degree-of-freedom system

Abstract: In this paper, passive and active control methods are applied to reduce the torsional vibration of a nonlinear dynamical system. This system is subjected to multi parametric excitation forces and m...

Vibration Suppression of Subharmonic Resonance Response Using a Nonlinear Vibration Absorber

Abstract: This paper is concerned with the vibration of a two degree-of-freedom (2DOF) nonlinear system subjected to multi-parametric excitation forces The vibrating motion of the system is described by the coupled differential equations having both quadratic and cubic terms The major task of the present paper is to use a nonlinear absorber to control the vibration of the nonlinear system near the simultaneous subharmonic and internal resonances, where the vibrations are severe Multiple scale perturbation technique (MSPT) is applied to obtain the averaged equations up to the second-order approximation The steady-state response and their stability are studied numerically for the nonlinear system at the simultaneous subharmonic and internal resonances Some recommendations regarding to the different system parameters are given following studying the effects of various parameters Comparison with the available published work is made

6 Li breakup and suppression of complete fusion above the Coulomb barrier

Abstract: We study the role of the projectile breakup in the fusion process by example of the 6 Li reactions with the 59 Co, 144 Sm and 209 Bi targets in vicinity of the Coulomb barrier. The coupled channel and distorted wave approaches are employed in order to calculate the complete fusion and the breakup cross sections, respectively. The partial cross sections in both the channels are compared in order to estimate the breakup fraction responsible for the suppression of complete fusion. The calculations are compared with available experimental data. The conclusions and recommendations are made.

Towards Reliable Mobile Cloud Computing

Abstract: Cloud computing has been one of the fastest growing components of the IT industry. It altered the future of the web by having computing, communication, and storage provides as services to internet users. Mobile Cloud Computing (MCC) is currently gaining steam as an extension to cloud computing as it delivers a large variety of cloud application to billions of smartphones and wearable devices. This paper studies reliability for MCC by determining the ability of a system component to function correctly under different scenarios for a specified period of time. Our aim is to be able to estimate and manage uncertainty and risks of failure. The assessment procedures consist of determine Mean Time between Failures (MTBF), Mean Time to Failure (MTTF), and availability percentages for main components in both cloud computing and MCC structures applied on single node OpenStack installation to analyze its performance with different settings governing the behavior of participants. Additionally, we present here several factors with significant impact on the overall cloud system reliability that should be taken into account in order to deliver highly available cloud computing services for mobile consumers.

Quality of Service Enhancement of Voice Over Internet Protocol Via Novel Scheduling Algorithm

Abstract: Transport of Voice over IP (VoIP) has many problems such as end-to-end delay, delay variation (jitter), and packet loss, with other problems contribute in degrading the speech quality. One of the techniques that are used to overcome these problems is the scheduling. The main challenge is to guarantee the same Quality of Service (QoS) as that of traditional telephony. In particular, the delay jitter introduced by queuing in packet switched networks has a devastating impact on the perceived quality. Currently, many of packet scheduling algorithms were mainly designed to achieve this task. The Strict Priority (SP) is low-cost to maintain the delay sensitive voice traffic. In this paper, a new scheduling algorithm is proposed using Voice Activity Detector (VAD) to give nearly 50% of the call time to the lower priority traffic in order to overcome its starvation problem. Experimental results using a network simulator, OPNET, are analyzed for voice traffic. Preliminary results show that the performance of the proposed algorithm assures the research idea.

Effect of Variable Blank Holder Force on the Springback and Weld-Line Movement During Draw-Bending of Tailor Welded Blanks

Abstract: Tailor welded blanks (TWBs) manufactured by drawing processes suffer from two major defects; weld-line movement (WLM) and springback. These defects can be reduced by using a counterpunch or controlling the value of the blank holder force and its scheme. This work presents a finite element analysis of the effect of variable blank holder force (VBHF) on springback and WLM of bench mark problem of draw-bending process of a TWB. The proposed VBHF scheme is developed based on the reaction forces predicted in a finite element model for artificially clamped weld-line case. The results obtained by applying VBHF are compared with those obtained using a counterpunch. The use of counterpunch is found to eliminate Vertical WLM in all the considered cases. Whereas side WLM using VBHF is found to be less than that obtained using counterpunch. When compared to the counterpunch technique, the springback values are found to be improved by applying the VBHF schemes.Copyright © 2015 by ASME

Performance investigation of axial piston pumps of constant power regulation

Abstract: The industrial variable displacement of axial piston pump conical cylinder has wide application in hydraulic drives of mobile machinery in view of some advantages, such as good features good suction characteristics , low noise level,small dimensions and weight at high values of working pressure. Also good solutions in presses, milling production line machine,stucker in cement production line. Our pump with constant power regulator has many applications but is a good solution in deep drawing presses used in home appliance industry very spreader in Egypt .I replaced an old line of pumps. So the study of this pump with specified control is essential to develop a model validated. This paper is dedicated to investigate the steady state and dynamic performance of this class. The pump controller is of rocker-arm type, it serves to produce constant output hydraulic power. The study includes the development of non-linear mathematical model of the pumping mechanism and the pump controller. The mathematical models were used to develop computer simulation programs byusing Simulink-matlab program. The study included an experimental part where the steady state and transient responses were measured. An acceptable agreement between the simulation and experimental results was observed, which validates the developed simulated model program.The simulation model program was used to conduct a parametric study. The results are presented and analyzed.