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Search Results: 1 - 10 of 1255 matches for " Moshe Horowitz "
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Multi-rate asynchronous sampling of sparse multi-band signals
Amir Rosenthal,Alex Linden,Moshe Horowitz
Physics , 2008, DOI: 10.1364/JOSAA.25.002320
Abstract: Because optical systems have huge bandwidth and are capable of generating low noise short pulses they are ideal for undersampling multi-band signals that are located within a very broad frequency range. In this paper we propose a new scheme for reconstructing multi-band signals that occupy a small part of a given broad frequency range under the constraint of a small number of sampling channels. The scheme, which we call multi-rate sampling (MRS), entails gathering samples at several different rates whose sum is significantly lower than the Nyquist sampling rate. The number of channels does not depend on any characteristics of a signal. In order to be implemented with simplified hardware, the reconstruction method does not rely on the synchronization between different sampling channels. Also, because the method does not solve a system of linear equations, it avoids one source of lack of robustness of previously published undersampling schemes. Our simulations indicate that our MRS scheme is robust both to different signal types and to relatively high noise levels. The scheme can be implemented easily with optical sampling systems.
Multirate Synchronous Sampling of Sparse Multiband Signals
Michael Fleyer,Amir Rosenthal,Alex Linden,Moshe Horowitz
Mathematics , 2008,
Abstract: Recent advances in optical systems make them ideal for undersampling multiband signals that have high bandwidths. In this paper we propose a new scheme for reconstructing multiband sparse signals using a small number of sampling channels. The scheme, which we call synchronous multirate sampling (SMRS), entails gathering samples synchronously at few different rates whose sum is significantly lower than the Nyquist sampling rate. The signals are reconstructed by solving a system of linear equations. We have demonstrated an accurate and robust reconstruction of signals using a small number of sampling channels that operate at relatively high rates. Sampling at higher rates increases the signal to noise ratio in samples. The SMRS scheme enables a significant reduction in the number of channels required when the sampling rate increases. We have demonstrated, using only three sampling channels, an accurate sampling and reconstruction of 4 real signals (8 bands). The matrices that are used to reconstruct the signals in the SMRS scheme also have low condition numbers. This indicates that the SMRS scheme is robust to noise in signals. The success of the SMRS scheme relies on the assumption that the sampled signals are sparse. As a result most of the sampled spectrum may be unaliased in at least one of the sampling channels. This is in contrast to multicoset sampling schemes in which an alias in one channel is equivalent to an alias in all channels. We have demonstrated that the SMRS scheme obtains similar performance using 3 sampling channels and a total sampling rate 8 times the Landau rate to an implementation of a multicoset sampling scheme that uses 6 sampling channels with a total sampling rate of 13 times the Landau rate.
Reduced Ventricular Arrhythmogeneity and Increased Electrical Complexity in Normal Exercised Rats
Horesh Dor-Haim, Omer Berenfeld, Michal Horowitz, Chaim Lotan, Moshe Swissa
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0066658
Abstract: Background The mechanisms whereby aerobic training reduces the occurrence of sudden cardiac death in humans are not clear. We test the hypothesis that exercise-induced increased resistance to ventricular tachycardia and fibrillation (VT/VF) involve an intrinsic remodeling in healthy hearts. Methods and Results Thirty rats were divided into a sedentary (CTRL, n = 16) and two exercise groups: short- (4 weeks, ST, n = 7) and long-term (8 weeks, LT, n = 7) trained groups. Following the exercise program hearts were isolated and studied in a Langendorff perfusion system. An S1–S2 pacing protocol was applied at the right ventricle to determine inducibility of VT/VF. Fast Fourier transforms were applied on ECG time-series. In-vivo measurements showed training-induced increase in aerobic capacity, heart-to-body weight ratio and a 50% low-to-high frequency ratio reduction in the heart rate variability (p<0.05). In isolated hearts the probability for VF decreased from 26.1±14.4 in CTRL to 13.9±14.1 and 6.7±8.5% in the ST and LT, respectively (p<0.05). Duration of VF also decreased from 19.0±5.7 in CTRL to 8.8±7.1 and 6.0±5.8 sec in ST and LT respectively (p<0.05). Moreover, the pacing current required for VF induction increased following exercise (2.9±1.7 vs. 5.4±2.1 and 8.5±0.9 mA, respectively; p<0.05). Frequency analysis of ECG revealed an exercise-induced VF transition from a narrow single peak spectrum at 17 Hz in CTRL to a broader range of peaks ranging between 8.8 and 22.5 Hz in the LT group (p<0.05). Conclusion Exercise in rats leads to reduced VF propensity associated with an intrinsic cardiac remodeling related to a broader spectral range and faster frequency components in the ECG.
The Transcervical Approach for Parapharyngeal Space Pleomorphic Adenomas: Indications and Technique
Gilad Horowitz, Oded Ben-Ari, Oshri Wasserzug, Noam Weizman, Moshe Yehuda, Dan M. Fliss
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090210
Abstract: Background Head and Neck Parapharyngeal space tumors are rare. Pleomorphic Adenomas are the most common Parapharyngeal space tumors. The purpose of this study was to define preoperative criteria for enabling full extirpation of parapharyngeal space pleomorphic adenomas via the transcervical approach while minimizing functional and cosmetic morbidity. Methods The surgical records and medical charts of 19 females and 10 males with parapharyngeal space pleomorphic adenomas operated between 1993 and 2012 were reviewed. Results Fifteen patients were operated by a simple transcervical approach, 13 by a transparotid transcervical approach, and one by a transmandibular transcervical approach. Complications included facial nerve paralysis, infection, hemorrhage and first bite syndrome. There were three recurrences, but neither recurrence nor complications were associated with the type of surgical approach. Conclusion A simple transcervical approach is preferred for parapharyngeal space pleomorphic adenomas with narrow attachments to the deep lobe of the parotid gland and for pleomorphic adenomas originating in a minor salivary gland within the parapharyngeal space.
Multi-rate asynchronous sampling of bandwidth-limited signals
Alfred Feldster,Yuval P. Shapira,Moshe Horowitz,Amir Rosenthal,Shlomo Zach,Lea Singer
Physics , 2008,
Abstract: We demonstrate experimentally an optical system for under-sampling several bandwidth limited signals with carrier frequencies that are not known apriori that can be located anywhere within a very broad frequency region between 0-18 GHz. The system is based on under-sampling asynchronously at three different sampling rates. The pulses required for the under-sampling are generated by a combination of an electrical comb generator and an electro-absorption modulator. To reduce loss and improve performance the implementation of the optical system is based on a wavelength division multiplexing technique. An accurate reconstruction of both the phase and the amplitude of the signals was obtained when two chirped signals generated simultaneously were sampled.
Harmonic Oscillator with Fluctuating Mass  [PDF]
Moshe Gitterman
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.210140
Abstract: We generalize the previously considered cases of a harmonic oscillator subject to a random force (Brownian motion), or having random frequency, or random damping. We consider here a random mass which corresponds to an oscillator where the particles of the surrounding medium adhere to the oscillator for some (random) time after collision, thereby changing the oscillator mass. Such a model is appropriate to chemical and biological solutions as well as to some nano-technological devices. The first moment and stability conditions for white and dichotomous noise are analyzed.
Oscillator with Random Mass  [PDF]
Moshe Gitterman
World Journal of Mechanics (WJM) , 2012, DOI: 10.4236/wjm.2012.22013
Abstract: We consider an oscillator with a random mass for which the particles of the surrounding medium adhere to the oscillator for some random time after the collision (Brownian motion with adhesion). This is another form of a stochastic oscillator, different from oscillator usually studied that is subject to a random force or having random frequency or random damping. We calculated first two moments for different form of a random force, and studied different resonance phenomena (stochastic resonance, vibration resonance and “erratic” behavior) interposed between order and chaos.
Almost Stochastic Dominance and Efficient Investment Sets  [PDF]
Moshe Levy
American Journal of Operations Research (AJOR) , 2012, DOI: 10.4236/ajor.2012.23038
Abstract: A major drawback of Mean-Variance and Stochastic Dominance investment criteria is that they may fail to determine dominance even in situations when all “reasonable” decision-makers would clearly prefer one alternative over another. Leshno and Levy [1] suggest Almost Stochastic Dominance (ASD) as a remedy. This paper develops algorithms for deriving the ASD efficient sets. Empirical application reveals that the improvement to the efficient sets implied by ASD is substantial (64% reduction for FSD). Direct expected utility maximization shows that investment portfolios excluded from the ASD efficient set would not have been chosen by any investors with reasonable preferences.
Root Study: Why Is It behind Other Plant Studies?  [PDF]
Moshe Silberbush
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.42026
Abstract: Until the 1980s, root studies were typically conducted in nutrient solution, because of the technical difficulties of studying roots in their natural environment, soil. Recent innovations and the realization that there are gaps between the expected and actual performance of plant root systems have emphasized the need for more realistic solutions. This review analyzes the study of plant roots in view of developments in soil science, microbiology, botany and plant physiology, and recently the introduction of molecular biology and computerized imaging.
Oscillator Subject to Periodic and Random Forces  [PDF]
Moshe Gitterman
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.41015

We illustrate the influence of an external periodic force and noise on a physical system by the example of an oscillator. These two forces seem to be the reverse of each other, since the latter leads to disorder while the former works in an orderly fashion. Nevertheless, it is shown that they may influence a system in a similar way, sometime even substituting for one another. These examples serve to illustrate one of the main achievements of twentieth-century physics, which has established that deterministic and random phenomena complement rather than contradict each other.

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