The automatic recognition of the modulation format of a detected signal is a major task of an intelligent receiver. This task becomes more difficult when the receiver has no information about the transmitted signal or the channel. At first, the maximum likelihood (ML) classifier for classifying phase-amplitude modulated schemes in coherent environment is presented. It is well known that the ML classifier requires a priori knowledge of the incoming signal and channel (including Amplitude, timing information, noise power and the roll-off factor of the PULSE SHAPING filter). To relax this requirement, we introduce a novel estimator to estimate the parameters required by ML classifier which is blind to the modulation scheme of the received signal, and this gives rise to a new completely blind modulation classifier for digital amplitude-phase modulated signals over fading channels. Results are presented from simulations in terms of correct detection probability versus SNR for the class of BPSK, QPSK, 8-PSK, 16-QAM and 64-QAM modulation schemes. The results show that the performance of this classifier is very close to the ideal classifier with perfect estimates.

In this research, temporal variations in intense TEA CO2 laser PULSEs passing through SF6 gas-filled cells with a pressure of 10- 150 mbar have been characterized at different energy fluences and gas pressures. It has been shown that for every fluence there is a certain cut-off pressure at which the PULSE spike is completely quenched. While the PULSE tail escapes, saving appreciable fractions of its initial energy. Experimental evidence along with FTIR spectrometry data have clearly revealed incisive laser-induced multi-photon dissociation of SF6 molecules in these conditions, pronounced as the main responsible for these behaviors.

In SCPC-DAMA satellite networks, the baseband RRC PULSE SHAPING is utilized to reduce the bandwidth and Inter Symbol Interference (ISI). But the variation in carrier's envelope, which expands the spectrum and ultimately increases the bandwidth, causes ISI and Quadrature Channel Crosstalk CQCc). The goal of this paper is to introduce a method to shape baseband RRC PULSEs, in order to make a nearly constant carrier envelope. We have introduced and implemented an algorithm to limit the amplitude variation of each PULSE to generate constant amplitude RRC PULSEs at the input of modulator. Matlab simulation and hardware experiments show that OQPSK modulation and this PULSE SHAPING method, can improve BER about 2dB.

In this paper, using a PULSE shaper, different geometric parameters affecting the incident PULSE shape and achieving a constant strain rate condition are studied. To this end, PULSE shapers in different thicknesses and diameters were made from copper. Based on wave propagation analysis, proper incident PULSE shape for testing brittle and hardening materials were determined. In addition, performing experiments and simulations in LS-DYNA, the effects of PULSE shaper thickness, its diameter, striker velocity, and its length on incident PULSE were studied. Moreover, several Hopkinson tests for cast iron (GGG-60) specimens with and without PULSE shaper were carried out. The results show that using PULSE shaper with proper dimensions helps to achieve constant strain rate condition which is highly desirable in split Hopkinson pressure bar testing.

Background: PULSE wave velocity (PWV) is widely used for estimating the stiffness of an artery. Various invasive and non-invasive methods have been developed to determine PWV over the years. In the present research, the non-invasive ESTIMATION of the PWV of large arteries was used as an index for arterial stiffness. Methods: A dynamic model based on the Navier-Stokes equations coupled to elasticity equations was introduced for the PWV in arteries with elastic walls. This system of equations was completed by clinical information obtained from the Doppler ultrasound images of the carotid artery of 40 healthy male volunteers. For this purpose, the Doppler ultrasound images were recorded and saved in a computer; and subsequently center-line blood velocity, arterial wall thickness, and arterial radius were measured by offline processing. Results: The results from the analytic solution of the completed equations showed that the mean value of PWV for the group of healthy volunteers was 2.35 m/s when the mean arterial radius was used as the neutral radius and 5.00 m/s when the end-diastole radius was used as the neutral radius. It is noteworthy that the latter value closely complies with that reported by other researchers. Conclusion: By applying this method, a non-invasive clinical and local evaluation of the common carotid artery stiffness via a Doppler ultrasound measurement will be possible.

Time-frequency analysis is an important technique in the seismic data involving nonstationary signal processing and interpretation. Due to the limitations of the Fourier transform in analyzing nonstationary signals, it cannot be used for time-frequency representation. Time-frequency transforms such as short-time Fourier transform, wavelet transform and S-transform are common tools in the study of nonstationary characteristics in the seismic data. Based on regularized least-squares inversion, Liu et al. (2009) have recently proposed a new method of time-varying frequency characterization of nonstationary seismic signals. In this paper, we applied the method of Liu et al. (2009) by designing an invertible nonstationary time-frequency transform called local time-frequency (LTF) transform (Liu and Fomel, 2010). This method generates time-frequency characterization without sliding windows. The LTF transform aims at depicting the nonstationary character of seismic data. This transform uses a Fourier basis to match the target signal under the regularized least-squares norm and provided an invertible time-frequency representation where are the Fourier coefficients and. The use of a non-stationary regression makes it possible for the coefficients to vary with x. In the linear case, they can be obtained by solving the least-squares problem: The solution where denotes the least-squares estimate of m and LT denotes the adjoint operator and S is a smoothing (SHAPING) operator, was introduced by Fomel (2007) using SHAPING regularization. The λ scaling in this solution controls the relative scaling of the forward operator L. The key idea is to minimize the error between the input signal and all of its Fourier components simultaneously using a regularized nonstationary regression (Fomel, 2009) with control on time resolution. The transform can provide LTF representations for common seismic data interpretation tasks such as Q factor ESTIMATION. Seismic waves lose energy by traveling through the earth due to a variety of phenomena such as attenuation. Attenuation refers to the loss of energy caused by phenomena other than geometrical spreading, and depends on the characteristics of the transmitting medium. Generally, attenuation is expressed in terms of quality factor (Q) which is a dimensionless parameter and is inversely proportional to attenuation coefficient. Experiments show that the quality factor is controlled by the elastic properties of formation and its fluid content. Hence, as one of the most important attributes in seismic exploration, it is used to directly identify hydrocarbon reserves on seismic sections (Hedlin et al., 2001). In this paper, we present a procedure using the differences in seismic reflection time-frequency spectra to estimate relative seismic attenuation in a reservoir of carbonate rock with fractures and voids. It is difficult to determine the seismic reflections at the top and bottom of the reservoir, required by the conventional amplitude ratio and the frequency spectra ratio methods. But in this study, we use the difference of seismic reflection time-frequency coefficients to estimate the relative seismic attenuation in such reservoirs. Gu and Stewart (2006) considered a special case where the incident spectrum has a Gaussian distribution, and discussed the reflection centroid of frequency downshift. Here, we give the analytical expression of the differences of reflection spectra corresponding to two frequencies with an attenuation coefficient. We show that the differences of reflection spectra corresponding to the two frequencies that are symmetrical to the centroid of frequency and separated by twice the incident signal’s standard deviation can be used to calculate the attenuation coefficient. As a time-frequency representation tool, the LTF transform of Fomel et al. (2010) is used to study seismic wave attenuation coefficient in synthetic and real field data examples.

In this paper, a new scheme for serial communication is proposed. In this method, in addition to the PULSE states (high and low), either of negative slope or positive slope of the PULSE (saw-tooth waveform) is employed as a representative for another digit. Using PULSE slope as a representative for a separate digit will result in sending two-bit-digits using a single PULSE, which doubles the transfer rate. The proposed scheme can be used in both synchronized and asynchronized communications and can improve communication speed. Through simulating the proposed scheme, it turned out that this method, because of its proper immunity to noise, can be used as a peripheral interface alongside in-chip communication. The main idea in the raised discussion is to obtain four different geometric PULSE shapes acting as four different numbers in the quaternary numeric system, in which it can be serialized/desrialized as easy as PULSE states. This proposed method and the suggested system for serialization and deserialization of data can be an adequate alternative in high-speed communication approaches.

Background & Objective: Several indices have been introduced to estimate arterial stiffness that based on changes in brachial blood pressure. But because of the error resulted by the substitution of brachial blood pressure instead of the other central arteries, such as carotid, it will be very important to present elastic parameter based on the mechanical models without any emphasis on brachial blood pressure. In this study, ESTIMATION of PULSE wave velocity of large arteries is used as an index for arterial stiffness. Materials & Methods: At first a suitable dynamic model is introduced for pulsatile blood flow in arteries based on Navier-Stokes equations in fluid mechanics. Then, according to the theory of elasticity, equations governing arterial wall is described and coupled to the equations of fluid flow. Attained system of equations is completed by clinical information that obtained from Doppler ultrasound images from carotid artery of healthy male subject. For this purpose Doppler ultrasound images were recorded and saved in computer and then center-line blood velocity, arterial wall thickness, the period of a cardiac cycle and arterial radius measured by offline processing. Results: The results from analytic solution of completed equations showed that the PWV for this healthy subject is 2 m/s. Conclusion: By applying this method, non-invasive and clinical evaluation of arterial stiffness by Doppler ultrasound measurement of common carotid artery without any measurement of local blood pressure will be possible.

The ESTIMATION of seismic demand that connects the ground motion intensity measure and the damage measure of structures is one of the most important components in the performance-based design. In the seismic demand model, the relationship between the structural response and a seismic parameter that expresses the random nature of earthquake is expressed in the mathematical form. Therefore, proper choice of earthquake intensity measure as a seismic parameter and identifying how it is related to structural damage can play an important role in reducing errors in seismic assessments. In many studies, the first mode spectral acceleration (Sa (t1)) or maximum ground acceleration (PGA) has been introduced as an appropriate intensity measure. However, some recent studies indicate that these IMs are insufficient in some circumstances. On the other hand, choosing a suitable method for measuring the sufficiency of intensity measures due to the existing uncertainties and also examining the performance of single-line demand model is of particular importance and should be considered. In this study, the suitability of different intensity measures of ground motion is quantified by using information theory and relative entropy concepts and    Sa (t1) is used as the base IM. For this purpose, several concrete moment frame structures with different number of floors and heights have been considered and time history dynamic analysis has been performed using PULSE-like earthquake records by IDARC software. The Park-Ang damage index, which has many applications, especially in concrete structures, has been used for structural response. Given that there is a possibility of different behavior of intensity measures at different damage levels, the discussion of multilinear demand models is proposed and the performance of several multilinear models has been evaluated by statistical tests. The results show that velocity-based intensity measures are sufficient for moderate damage level under PULSE liked records. At these damage levels, the use of first mode spectral acceleration or acceleration-based intensity measures such as maximum ground acceleration can cause errors. Also, studies conducted in this paper have shown that the use of single-linear model is not suitable for all damage levels and the use of a three linear model with respect to damage levels can reduce errors in seismic assessments.

Many important speech enhancement methods operate in frequency domain. In these methods, a frequency gain filter is multiplied by the noisy spectrum. In this paper, frequency methods are investigated and the gain filters are shown as functions of the Signal to Noise Ratio (SNR). Since gain filters are functions of SNR, SNR ESTIMATION methods are presented and consequently a new SNR ESTIMATION method is proposed. Moreover, we proposed a technique for controlling the level of residual noise and SHAPING it. In our proposed techniques, the frequency gain filters are tuned in order to have less noise reduction and as a result achieve less distortion. In addition to controlling the level of noise, in our proposed technique, the shape of residual noise is changed in order to have more pleasant residual noise. For evaluation of methods, listening tests are performed and the results are reported based of four aspects of speech signals: musical residual noise, level of background noise, echo and unnatural residual noise. Evaluation of methods shows that the proposed methods are successful from these aspects point of view.