Journal of Advanced Materials in Engineering (Esteghlal)

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Pulse Width Modulation (PWM) techniques are commonly used to control the output voltage and current of DC to AC converters. Space Vector Modulation (SVM), of all PWM methods, has attracted attention because of its simplicity and desired properties in digital control of Three-Phase inverters. The main drawback of this PWM technique is its complex and time-consuming computations in real-time implementation. The time-consuming calculation as well as software and hardware complexities of the network grow dramatically as the number of inverter levels increases. Therefore, it is necessary to develop an exact, fast, and general computation SVM algorithm for multi-level converters. This paper introduces such an algorithm. Specifically, the SVM computation algorithm based on a vector classification technique, introduced for 2-level inverters in 1996, is developed and generalized to be applicable in determining the switching sequences and calculating the switching instants in m-level inverters. The proposed technique reduces hardware and software complexities, decreases the computation time, and increases the accuracy of the positioning of the switching instants when compared with the conventional implementation of the SVM in multi-level converters

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In this paper, an elastic constitutive model based on the Eulerian corotational rate of the logarithmic strain tensor is proposed. Using this model, the large deformation of a closed cycle containing tension, shear, compression and inverse shear is analyzed. Since the deformation path includes a closed cycle and the material is considered as an isotropic elastic material, the normal and shear components of the stress at the end of the cycle must vanish. Using conventional constitutive models, the non-zero solution for the stress components is obtained. Using the proposed constitutive model, the normal and shear components of stress at the end of the cycle are obtained to be exactly equal to zero.

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With progress in radar systems, a number of methods have been developed for signal processing and detection in radars. A number of modern radar signal processing methods use time-frequency transforms, especially the wavelet transform (WT) which is a well-known linear transform. The interference canceling is one of the most important applications of the wavelet transform. In Ad-hoc detection methods, the interference is firstly canceled and then a simple detector, like an energy detector, is used. Therefore, we have used wavelet-based approaches to cancel the interference and then an energy detector has been employed. In this paper, it is shown that in practical cases where the performance of matched filter or near-matched filter is degraded, wavelet-based methods are more efficient. Also, we have shown that for cases where targets with slow radial velocity or one close to blind velocity are removed by the MTI filter, wavelet-based denoising has a better performance.

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