Saadetdin Herdem

Analysis of nonlinear circuits by using differential Taylor transform

Abstract An effective but not widely used method, differential Taylor transform, is introduced for the analysis of the nonlinear electrical circuits. To apply the method the differential transform of the mathematical model of the system is obtained first, and then the response function is evaluated by using the inverse transform of the differential spectra. The inverse transform can be written in the form of Taylor series. The method is described with two examples for nonlinear electrical circuits.

Theory of high-gradient magnetic filter performance

A unique general model for high-gradient magnetic filters is presented. The functional dependence of the filter performance on the systems physical and geometrical parameters is derived. The derived theoretical expression makes it possible to explain both of the two different, apparently opposite, experimental results reported in the literature. The new quality factor does not include the suspension viscosity, but instead depends on the suspension density, which leads to the application of the formula for a larger class of filtration media including liquids, gases, and vapors.

Computation of corona effects in transmission lines using state-space techniques

Abstract In this paper, state-space method is applied to compute transients in power transmission lines by considering corona effects. Transmission line is modeled by lumped parameter identical sections to simulate the distribution nature of the line and nonlinear corona branches are combined with these sections. The whole system is composed of RLC elements, sources and switches. The response of the system is calculated using state-space method which has been developed for the analysis of nonlinear power electronic circuits with periodically operated switches.

Comparison of first and second heart sounds after mechanical heart valve replacement

In this article, the spectral features of first heart sounds (S1) and second heart sounds (S2), which comprise the mechanical heart valve sounds obtained after aortic valve replacement (AVR) and mitral valve replacement (MVR), are compared to find out the effect of mechanical heart valve replacement and recording area on S1 and S2. For this aim, the Welch method and the autoregressive (AR) method are applied on the S1 and S2 taken from 66 recordings of 8 patients with AVR and 98 recordings from 11 patients with MVR, thereby yielding power spectrum of the heart sounds. Three features relating to frequency of heart sounds and three features relating to energy of heart sounds are obtained. Results show that in comparison to natural heart valves, mechanical heart valves contain higher frequency components and energy, and energy and frequency components do not show common behaviour for either AVR or MVR depending on the recording areas. Aside from the frequency content and energy of the sound generated by mechanical heart valves being affected by the structure of the lungs–thorax and the recording areas, the pressure across the valve incurred during AVR or MVR is a significant factor in determining the frequency and energy levels of the valve sound produced. Though studies on native heart sounds as a non-invasive diagnostic method has been done for many years, it is observed that studies on mechanical heart valves sounds are limited. The results of this paper will contribute to other studies on using a non-invasive method for assessing the mechanical heart valve sounds.

Analysis of spectral features of mechanical heart valve sounds after aortic and mitral valve replacement

Mechanical heart valves are a substitute for malfunctional native heart valves. In this study, the spectral features of S1 and S2 component of the mechanical heart valve sounds obtained after aortic valve replacement (AVR) and mitral valve replacement (MVR) are compared. For this aim, AR methods are applied on the S1 and S2 components of heart sounds taken from 68 recording of 8 patients with AVR and 87 recordings from 11 patients with MVR, thereby yielding power spectrum of the heart sound and six different features are obtained from power spectrum of the heart sounds. Using these features, S1 and S2 components are compared.

The effects of fuzzy control of magnetic flux on magnetic filter performance and energy consumption

Magnetic filters are used effectively in many industrial areas to clean up technological liquids and gases from micron and submicron size magnetic particles. Performance of the magnetic filter is affected by technological parameters like flow rate of the industrial liquid and concentration and flux magnitude of the magnetic filter. These parameters exhibit differences depending on the field of work. Controlling of magnetic filters without regard to these parameters has disadvantages such as low filter performance, ineffectiveness in parameter changes and high energy consumption. To remove these disadvantages, an adaptive fuzzy control system which considers these technological parameters was designed and realized. When the realized filter is compared to the filter that ignores technological parameters, it is observed that energy can be saved at a rate of 68% annually.

Analysis of Magnetization Properties of the Ferromagnetic Granular Beds

Magnetization properties of the packed beds that are constructed from ferromagnetic balls and metal chips have been examined. The average magnetic permeability and magnetization curves of the non-homogeneous ferromagnetic granulated medium (different size polyballs and chips) have been determined using the channel-by-channel magnetization model. From the magnetic properties of the single chain of the different sized balls as an element of the chain bundle in the polyball medium, application conditions of the model to the polyball medium were estimated. A new correlation for the influence of the packing density factor or the bed porosity change on the average magnetization curve has been evaluated. A new correlation between the packing density factor and the size of the bed elements, and also a relationship between the relative magnetic permeability of the bed elements and the external magnetic field intensity were obtained. The obtained theoretical results were compared with statistical data and an agreement was observed.

The Designing of Data Acquisition Card through PIC18F4550 and an Interface Study

Since automatic control is used in every field, there is almost no industrial application system which doesn’t employ the sensors. It makes correctly reading the data obtained from sensors in the system with sensors and transmitting this data into the computer more important. In this executed study, a design for an interface which can be easily used with a low cost data processing card and with flexible structure was performed. In the executed system, the PIC18F4550 microcontroller was used and data can be accurately read from 10 different channels. The data read from the designed data acquisition card was transferred into a computer interface program prepared in C# program using a USB and recorded into the database in the Microsoft Access program. The designed interface, the values of read signals and their graphs may be displayed on the screen. Thus, the interface screen may be used as both an indicator and oscilloscope screen.

Implementation of cooperative communications using ultrasonic wireless terminals

In this paper, an experimental framework that enables observing the performance improvements provided by cooperative diversity schemes is introduced. Unlike the RF based test-beds proposed in the literature, a wireless network consisting of ultrasonic terminals has been implemented. It has been shown that terrestrial applications of the ultrasonic communications provide an effective computer-aided experiment environment on which various cooperative physical layer protocols can be tested. Using this empirical setup, a digital relaying based bi-directional communication scenario has been examined where two users exchange information by employing differential binary modulation and network coding via a relay. The direct and relayed bit-wise XOR-ed and differential encoded signals are combined based on maximum likelihood (ML) detection at the receivers to prevent performance loss due to error propagation. Bit Error Rate (BER) measurement results have verified the theoretical studies in the literature by demonstrating that full diversity order is obtained.

Time Domain Features of Heart Sounds for Determining Mechanical Valve Thrombosis

Thrombosis of implanted heart valve is a rare but lethal complication for patients with mechanical heart valve. Echocardiogram of mechanical heart valves is necessary to diagnose valve thrombosis definitely. Because of the difficulty in making early diagnosis of thrombosis, and the cost of diagnosis equipment and operators, improving noninvasive, cheap and simple methods to evaluate the functionality of mechanical heart valves are quite significant especially for first step medical center. Because of this, time domain features obtained from auscultation of heart sounds are proposed to evaluate mechanical heart valve thrombosis as a simple method in this chapter. For this aim, heart sounds of one patient with mechanical heart valve thrombosis and five patients with normally functioning mechanical heart valve were recorded. Time domain features of recorded heart sounds, the skewness and kurtosis, were calculated and statistically evaluated using paired and unpaired t-test. As a result, it is clearly seen that the skewness of first heart sound is the most discriminative features (p < 0.01) and it may be used fairly well in differentiating normally functioning mechanical heart valve from malfunctioning mechanical heart valve.