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991.
Kamran Kazemi Mohammadreza Amirian Mohammad Javad Dehghani 《Signal, Image and Video Processing》2014,8(3):533-541
The S-transform presents arbitrary time series as localized invertible time–frequency spectra. This transformation improves the short-time Fourier transform and the wavelet transform by merging the multiresolution and frequency-dependent analysis properties of wavelet transform with the absolute phase retaining of Fourier transform. The generalized S-transform utilizes a combination of a Fourier transform kernel and a scalable-sliding window. The common S-transform applies a Gaussian window to provide appropriate time and frequency resolution and minimizes the product of these resolutions. However, the Gaussian S-transform is unable to obtain uniform time and frequency resolution for all frequency components. In this paper, a novel window based on the $t$ student distribution is proposed for the S-transform to achieve a more uniform resolution. Simulation results show that the S-transform with the proposed window provides in comparison with the Gaussian window a more uniform resolution for the entire time and frequency range. The result is suitable for applications such as spectrum sensing. 相似文献
992.
993.
Mahdi Hajiaghayi Carl Wijting Cassio Ribeiro Mohammad T. Hajiaghayi 《Wireless Networks》2014,20(4):611-624
In this paper, we construct a practical framework for efficiently allocating long term evolution (LTE) resource blocks (RB) among the users in a device-to-device (D2D) network. For such network that presumably operates under the LTE cellular network, our aim is to improve the overall throughput of D2D connections using opportunistic or fairness-based approach. Taking the practical considerations into account, our proposed framework allows a number of connections to share a single RB whenever possible, thus utilizing the radio resources. To do so, our solution first identifies a superior set of the interference-free D2D reuse groups via graph modeling and graph coloring approach. In particular, we model a D2D network with a two-overlapping disk graph for which a suitable coloring algorithm is proposed and its performance bound is calculated. Once the reuse groups are known, our solution optimizes the RB allocation among these groups based on their reported channel condition as well as the scheduling criterion, whether it is fairness-based or opportunistic. Through numerical experiments, we show that our solution can significantly improve the throughput performance of a D2D network. 相似文献
994.
Mohammad A. Al-Jarrah Nedal K. Al-Ababneh Mohammad M. Al-Ibrahim Rami A. Al-Jarrah 《AEUE-International Journal of Electronics and Communications》2014,68(10):1022-1029
In this paper, parallel distributed detection in wireless sensor network (WSN) is investigated. Sensors are assumed to be transmitting their local decisions to a fusion center through a wireless fading channel using cooperative transmission. To enable cooperative transmission, sensors are divided into groups where sensors in each group help each other in transmitting their decisions in a way that the fusion center receives each local decision as an orthogonal frequency division multiplexed (OFDM) block. The fusion center detects all OFDM blocks sent by all groups to process them in order to obtain a final (global) decision. Using this cooperative transmission scheme enables the fusion center to apply diversity combining methods in order to reduce the fading effects of the channel. Optimal and sub-optimal fusion rules are derived for such system. Simulation results are provided to show the performance improvement that can be obtained compared to the conventional system where each local decision is transmitted to the fusion center individually and no diversity technique is applied at the fusion center. 相似文献
995.
Ariffuddin Joret Mohammad Faiz Liew Abdullah Muhammad Suhaimi Sulong Asmarashid Ponniran Siti Zuraidah Zainudin 《电子科技学刊:英文版》2014,12(1):90-94
Moments have been used in all sorts of object classification systems based on image. There are lots of moments studied by many researchers in the area of object classification and one of the most preference moments is the Zernike moment. In this paper, the performance of object classification using the Zernike moment has been explored. The classifier based on neural networks has been used in this study. The results indicate the best performance in identifying the aggregate is at 91.4% with a ten orders of the Zernike moment. This encouraging result has shown that the Zernike moment is a suitable moment to be used as a feature of object classification systems. 相似文献
996.
Post- dehydration storage life of fruits and plant nuts such as apricot, raisin, date, fig, almond, peanut, pinenut and walnut, was studied. The results showed that radiation dose of 1.0 kGy completely, inhibited insect infestation. Low dose radiation (0.25kGy) plus 20℃ and vacuum extended the storage life for 6 and 12 months in dry nuts and fruits respectively without affecting nutritional quality except ascorbic acid. Packaging in opaque pouches under vacuum proved better than other treatments in maintaining nutritional and sensoric quality. 相似文献
997.
Mohammad Reza Mousavi Michel Reniers 《Electronic Notes in Theoretical Computer Science》2007,175(1):45
In this paper, we solve two open problems posed by Karen L. Bernstein regarding her promoted tyft format for structured operational semantics. We show that, unlike formats with closed terms as labels, such as the tyft format, the well-foundedness assumption cannot be dropped for the promoted tyft format while preserving the congruence result. We also show that the well-founded promoted tyft format is incomparable to the tyft format with closed terms as labels, i.e., there are transition relations that can be specified by the promoted tyft format but not by the tyft format, and vice versa. 相似文献
998.
Mohammad Hossein Habibi Mojtaba Nasr-Esfahani Terry A. Egerton 《Journal of Materials Science》2007,42(15):6027-6035
TiO2—methylcellulose (MC) nanocomposite films processed by the sol-gel technique were studied for phocatalytic applications. Precalcined
TiO2 nanopowder was mixed with a sol and heat treated. The sol suspension was prepared by first adding titanium tetra isopropoxide
(Ti(OPr)4 or TTP) to a mixture of ethanol and HCl (molar ratio TTP:HCl:EtOH:H2O = 1:1.1:10:10) and then adding a 2 wt.% solution of methylcellulose (MC). The TiO2 nanopowder was dispersed in the sol and the mixture was deposited on a microscope glass slide by spin coating. Problems of
film inhomogeneity and defects which caused peeling and cracking during calcinations, because of film shrinkage, were overcome
by using MC as a dispersant. Effect of MC on the structure evaluation, crystallization behavior and mechanical integrity with
thermal treatment up to 500 °C are followed by SEM, XRD and scratch test. XRD Scanning electron microscopy (SEM) showed that
the composite films with MC have much rougher surface than films made without MC. Composite films heat treated at approximately
500 °C have the greatest hardness values. For the composite thick film, the minimum load which caused the complete coating
removal was 200 g/mm2, an indication of a strong bond to the substrate. Photocatalytic activities of the composite film were evaluated through
the degradation of a model pollutant, the textile dye, Light Yellow X6G (C.I. Reactive Yellow 2) and were compared with the
activity of (i) a similar composite film without MC, and (ii) a TiO2 nanopowder. The good mechanical integrity make this composite film an interesting candidate for practical catalytic applications. 相似文献
999.
The degradation behaviour of electrochemically prepared polythiophene and polypyrrole has been studied by thermal gravimetric
analysis technique. Studies on both the polymers show that they are more stable than polyacetylene but still undergo degradation
reactions which involve two steps, viz. loss of dopant and then degradation of polymer backbone. The general features of degradation
mechanisms are discussed. 相似文献
1000.
Andrew J. Allen Susan Krueger Ganesh Skandan Gabrielle G. Long Horst Hahn Helen M. Kerch John C. Parker Mohammad N. All 《Journal of the American Ceramic Society》1996,79(5):1201-1212
Using small-angle scattering, together with density measurements, X-ray diffraction, nitrogen adsorption, and both transmission and scanning electron microscopy, the microstructural evolution during sintering in nanostructured ceramic oxides has been studied. The availability of samples with sufficient size and uniformity has permitted absolute calibration of the scattering data and made possible determinations of microstructural parameters and surface areas that are statistically representative of the undisturbed nanophase morphologies. A fully quantitative microstructural model has been developed, and the effects of varying processing parameters during powder synthesis and sintering have been assessed. Predictions are made regarding the achievable sintered full-density microstructures. 相似文献