Volume 62 (2011): Issue 4 (July 2011)

In this paper the results of the estimation of the fundamental frequency of the speech signal modeled by the G.723.1 method are analyzed. The estimation of the fundamental frequency was performed by the Peaking-Peaks algorithm with the implemented Parametric Cubic Convolution (PCC) interpolation. The efficiency of PCC was tested for Keys, Greville and Greville two-parametric kernel. Depending on MSE a window that gives optimal results was chosen.

This paper presents an optimal solution for eliminating pre specified order of harmonics from a stepped waveform of a multilevel inverter topology with equal dc sources. The main challenge of solving the associated non linear equation which are transcendental in nature and therefore have multiple solutions is the convergence of the relevant algorithms and therefore an initial point selected considerably close to the exact solution is required. The paper describes an efficient genetic algorithm that reduces significantly the computational burden resulting in fast convergence. An objective function describing a measure of effectiveness of eliminating selected order of harmonics while controlling the fundamental component is derived. The performance of cascaded multilevel inverter is compared based on computation of switching angle using Genetic Algorithm as well as conventional Newton Raphson approach. A significant improvement in harmonic profile is achieved in the GA based approach. A nine level cascaded multi level inverter is simulated in MATLAB Simulink and a proto type model has been fabricated to validate the simulation results.

Environment recognition from digital audio for forensics application is a growing area of interest. However, compared to other branches of audio forensics, it is a less researched one. Especially less attention has been given to detect environment from files where foreground speech is present, which is a forensics scenario. In this paper, we perform several experiments focusing on the problems of environment recognition from audio particularly for forensics application. Experimental results show that the task is easier when audio files contain only environmental sound than when they contain both foreground speech and background environment. We propose a full set of MPEG-7 audio features combined with mel frequency cepstral coefficients (MFCCs) to improve the accuracy. In the experiments, the proposed approach significantly increases the recognition accuracy of environment sound even in the presence of high amount of foreground human speech.

This research has been motivated by industrial demand for single phase PWM rectifier in traction application. This paper presents an advanced control structure design for a single phase PWM rectifier. The PWM rectifier is controlled to consume nearly sinusoidal current with power factor nearing to unity. The control structure consists of a DC-link voltage controller and a current controller implemented by a proportional-resonant controller using a fast phase angle and frequency estimator. The estimation algorithm is derived from the weighted least-squares estimation method. The feasibility of the proposed control structure is confirmed by experimental tests performed on designed laboratory prototype.

A variety of flight control units have been put into realization for navigational purposes of spatially moving vehicles (SMV), which is mostly manipulated by 2 or 3 degrees-of-freedom (DOF) joysticks. Since motion in space consists of three translational motions in forward, side and vertical directions and three rotational motions about these axis; with present joystick interfaces, spatial vehicles has to employ more than one navigational control unit to be able to navigate on all required directions. In this study, a 3 × 3 Stewart-Platform-based FBW (Fly-By-Wire) flight control unit with force feedback is presented which will provide single point manipulation of any SMVs along three translational and about three rotational axis. Within the frame of this paper, design, capability and the advantages of the novel system is mentioned. Kinematics of a Stewart Platform (SP) mechanism employed and its motion potentials is presented by simulations and workspace of the system is evaluated. Dynamic analysis by Bond-Graph approach will be mentioned. Mechatronic design of the complete structure is discussed and force reflection capability of the system with simulations is pointed out using stiffness control. Finally, the possible future work of the subject is discussed which may include the feasible solutions of the SP in terms of size and safety when implementing inside a cockpit.

This paper reports a study of coil inductance profile in all positions of plunger in tubular linear reluctance motors (TLRMs) with open type magnetic circuits. In this paper, maximum inductance calculation methods in winding of tubular linear reluctance motors are described based on energy method. Furthermore, in order to calculate the maximum inductance, equivalent permeability is measured. Electromagnetic finite-element analysis for simulation and calculation of coil inductance in this motor is used. Simulation results of coil inductance calculation using 3-D FEM with coil current excitation is compared to theoretical and experimental results. The comparison yields a good agreement.

The main objective of this paper is to develop the Service Oriented Architectural (SOA) Model for representation of power systems, especially of computing load flow analysis of large interconnected power systems. The proposed SOA model has three elements namely load flow service provider, power systems registry and client. The exchange of data using XML makes the power system services standardized and adaptable. The load flow service is provided by the service provider, which is published in power systems registry for enabling universal visibility and access to the service. The message oriented style of SOA using Simple Object Access Protocol (SOAP) makes the service provider and the power systems client to exist in a loosely coupled environment. This proposed model, portraits the load flow services as Web services in service oriented environment. To suit the power system industry needs, it easily integrates with the Web applications which enables faster power system operations.

At the present time work of spot welding is being broadly used at automotive applications which need serial production process and at part unification. In order to create a high quality spot welding time of welding, electric current intensity, junction, stress, and diameter of electrodes point must be considered earlier, Geometry of electrode point and current density are important for increasing quality at spot welding. In this study, Enose, Bnose and parabolic (ParaCap) type electrode geometries have been considered during design processes. Meanwhile, CMW 73, CMW 100, CMW 353, Elkaloy D, Elkaloy 20, Copper alloyed electrode types have been analyzed by using a magnetic analyzes software. The results helped to determine the best suitable electrode type which gives the best current density amongst different alloys and electrode shapes for the spot welding machines which have same diameter of electrode point.

The magnetic susceptibility shows a Hopkinson peak just below the Curie temperature T_C when heating the selected hexagonal and spinel ferrite samples. It is proposed that this peak can be associated with a transition from stable magnetic state to super-paramagnetic relaxation above the blocking temperature up to the T_C. The Hopkinson effect results are compared with SEM micrographs of both studied hexagonal and spinel ferrites.

In this paper, an analytical approach for evaluating performance of dual-hop cooperative link over shadowed Ricean fading channels is presented. New lower bound expressions for the probability density function (PDF), cumulative distribution function (CDF) and average bit error probability (ABEP) for system with channel state information (CSI) relay are derived. Some numerical results are presented to show behavior of performance gain for the proposed system. Analytical exact and lower bound expression for the outage probability (OP) of CSI assisted relay are obtained and required numerical results are compared.